Spinal cord injury is considered one of the most difficult injuries to repair and has one of the worst prognoses for injuries to the nervous system.Following surgery,the poor regenerative capacity of nerve cells and t...Spinal cord injury is considered one of the most difficult injuries to repair and has one of the worst prognoses for injuries to the nervous system.Following surgery,the poor regenerative capacity of nerve cells and the generation of new scars can make it very difficult for the impaired nervous system to restore its neural functionality.Traditional treatments can only alleviate secondary injuries but cannot fundamentally repair the spinal cord.Consequently,there is a critical need to develop new treatments to promote functional repair after spinal cord injury.Over recent years,there have been seve ral developments in the use of stem cell therapy for the treatment of spinal cord injury.Alongside significant developments in the field of tissue engineering,three-dimensional bioprinting technology has become a hot research topic due to its ability to accurately print complex structures.This led to the loading of three-dimensional bioprinting scaffolds which provided precise cell localization.These three-dimensional bioprinting scaffolds co uld repair damaged neural circuits and had the potential to repair the damaged spinal cord.In this review,we discuss the mechanisms underlying simple stem cell therapy,the application of different types of stem cells for the treatment of spinal cord injury,and the different manufa cturing methods for three-dimensional bioprinting scaffolds.In particular,we focus on the development of three-dimensional bioprinting scaffolds for the treatment of spinal cord injury.展开更多
Traditional tumor models do not tend to accurately simulate tumor growth in vitro or enable personalized treatment and are particularly unable to discover more beneficial targeted drugs.To address this,this study desc...Traditional tumor models do not tend to accurately simulate tumor growth in vitro or enable personalized treatment and are particularly unable to discover more beneficial targeted drugs.To address this,this study describes the use of threedimensional(3D)bioprinting technology to construct a 3D model with human hepatocarcinoma SMMC-7721 cells(3DP-7721)by combining gelatin methacrylate(GelMA)and poly(ethylene oxide)(PEO)as two immiscible aqueous phases to form a bioink and innovatively applying fluorescent carbon quantum dots for long-term tracking of cells.The GelMA(10%,mass fraction)and PEO(1.6%,mass fraction)hydrogel with 3:1 volume ratio offered distinct pore-forming characteristics,satisfactorymechanical properties,and biocompatibility for the creation of the 3DP-7721 model.Immunofluorescence analysis and quantitative real-time fluorescence polymerase chain reaction(PCR)were used to evaluate the biological properties of the model.Compared with the two-dimensional culture cell model(2D-7721)and the 3D mixed culture cell model(3DM-7721),3DP-7721 significantly improved the proliferation of cells and expression of tumor-related proteins and genes.Moreover,we evaluated the differences between the three culture models and the effectiveness of antitumor drugs in the three models and discovered that the efficacy of antitumor drugs varied because of significant differences in resistance proteins and genes between the three models.In addition,the comparison of tumor formation in the three models found that the cells cultured by the 3DP-7721 model had strong tumorigenicity in nude mice.Immunohistochemical evaluation of the levels of biochemical indicators related to the formation of solid tumors showed that the 3DP-7721 model group exhibited pathological characteristics of malignant tumors,the generated solid tumors were similar to actual tumors,and the deterioration was higher.This research therefore acts as a foundation for the application of 3DP-7721 models in drug development research.展开更多
Three-dimensional(3D)bioprinting is widely used in ophthalmic clinic,including in diagnosis,surgery,prosthetics,medications,drug development and delivery,and medical education.Articles published in 2011–2022 into bio...Three-dimensional(3D)bioprinting is widely used in ophthalmic clinic,including in diagnosis,surgery,prosthetics,medications,drug development and delivery,and medical education.Articles published in 2011–2022 into bioinks,printing technologies,and bioprinting applications in ophthalmology were reviewed and the strengths and limitations of bioprinting in ophthalmology highlighted.The review highlighted the trade-offs of printing technologies and bioinks in respect to,among others,material type cost,throughput,gelation technique,cell density,cell viability,resolution,and printing speed.There is already widespread ophthalmological application of bioprinting outside clinical settings,including in educational modelling,retinal imaging/visualization techniques and drug design/testing.In clinical settings,bioprinting has already found application in pre-operatory planning.Even so,the findings showed that even with its immense promise,actual translation to clinical applications remains distant,but relatively closer for the corneal(except stromal)tissues,epithelium,endothelium,and conjunctiva,than it was for the retina.This review similarly reflected on the critical on the technical,practical,ethical,and cost barrier to rapid progress of bioprinting in ophthalmology,including accessibility to the most sophisticated bioprinting technologies,choice,and suitability of bioinks,tissue viability and storage conditions.The extant research is encouraging,but more work is clearly required for the push towards clinical translation of research.展开更多
Among the different bioprinting techniques,the drop-on-demand(DOD)jetting-based bioprinting approach facilitates contactless deposition of pico/nanoliter droplets ofmaterials and cells for optimal cell–matrix and cel...Among the different bioprinting techniques,the drop-on-demand(DOD)jetting-based bioprinting approach facilitates contactless deposition of pico/nanoliter droplets ofmaterials and cells for optimal cell–matrix and cell–cell interactions.Although bioinks play a critical role in the bioprinting process,there is a poor understanding of the influence of bioink properties on printing performance(such as filament elongation,formation of satellite droplets,and droplet splashing)and cell health(cell viability and proliferation)during the DOD jetting-based bioprinting process.An inert polyvinylpyrrolidone(PVP360,molecular weight=360 kDa)polymerwas used in this study to manipulate the physical properties of the bioinks and investigate the influence of bioink properties on printing performance and cell health.Our experimental results showed that a higher bioink viscoelasticity helps to stabilize droplet filaments before rupturing from the nozzle orifice.The highly stretched droplet filament resulted in the formation of highly aligned“satellite droplets,”which minimized the displacement of the satellite droplets away from the predefined positions.Next,a significant increase in the bioink viscosity facilitated droplet deposition on the wetted substrate surface in the absence of splashing and significantly improved the accuracy of the deposited main droplet.Further analysis showed that cell-laden bioinks with higher viscosity exhibited higher measured average cell viability(%),as the presence of polymer within the printed droplets provides an additional cushioning effect(higher energy dissipation)for the encapsulated cells during droplet impact on the substrate surface,improves the measured average cell viability even at higher droplet impact velocity and retains the proliferation capability of the printed cells.Understanding the influence of bioink properties(e.g.,bioink viscoelasticity and viscosity)on printing performance and cell proliferation is important for the formulation of new bioinks,and we have demonstrated precise DOD deposition of living cells and fabrication of tunable cell spheroids(nL–μL range)using multiple types of cells in a facile manner.展开更多
Cryobioprinting has tremendous potential to solve problems to do with lack of shelf availability in traditional bioprinting by combining extrusion bioprinting and cryopreservation.In order to ensure the viability of c...Cryobioprinting has tremendous potential to solve problems to do with lack of shelf availability in traditional bioprinting by combining extrusion bioprinting and cryopreservation.In order to ensure the viability of cells in the frozen state and avoid the possible toxicity of dimethyl sulfoxide(DMSO),DMSO-free bioink design is critical for achieving successful cryobioprinting.A nontoxic gelatin methacryloyl-based bioink used in cryobioprinting is composed of cryoprotective agents(CPAs)and a buffer solution.The selection and ratio of CPAs in the bioink directly affect the survival of cells in the frozen state.However,the development of universal and efficient cryoprotective bioinks requires extensive experimentation.We first compared two commonly used CPA formulations via experiments in this study.Results show that the effect of using ethylene glycol as the permeable CPA was 6.07%better than that of glycerol.Two datasets were obtained and four machinelearning models were established to predict experimental outcomes.The predictive powers of multiple linear regression(MLR),decision tree(DT),random forest(RF),and artificial neural network(ANN)approaches were compared,suggesting an order of ANN>RF>DT>MLR.The final selected ANN model was then applied to another dataset.Results reveal that this machine-learning method can accurately predict the effects of cryoprotective bioinks composed of different CPAs.Outcomes also suggest that the formulations presented here have universality.Our findings are likely to greatly accelerate research and development on the use of bioinks for cryobioprinting.展开更多
Articular cartilage damage caused by trauma or degenerative pathologies such as osteoarthritis can result in significant pain,mobility issues,and disability.Current surgical treatments have a limited capacity for effi...Articular cartilage damage caused by trauma or degenerative pathologies such as osteoarthritis can result in significant pain,mobility issues,and disability.Current surgical treatments have a limited capacity for efficacious cartilage repair,and long-term patient outcomes are not satisfying.Three-dimensional bioprinting has been used to fabricate biochemical and biophysical environments that aim to recapitulate the native microenvironment and promote tissue regeneration.However,conventional in vitro bioprinting has limitations due to the challenges associated with the fabrication and implantation of bioprinted constructs and their integration with the native cartilage tissue.In situ bioprinting is a novel strategy to directly deliver bioinks to the desired anatomical site and has the potential to overcome major shortcomings associated with conventional bioprinting.In this review,we focus on the new frontier of robotic-assisted in situ bioprinting surgical systems for cartilage regeneration.We outline existing clinical approaches and the utilization of robotic-assisted surgical systems.Handheld and robotic-assisted in situ bioprinting techniques including minimally invasive and non-invasive approaches are defined and presented.Finally,we discuss the challenges and potential future perspectives of in situ bioprinting for cartilage applications.展开更多
The review focuses on the most important areas of cell therapy for spinal cord injuries.Olfactory mucosa cells are promising for transplantation.Obtaining these cells is safe for patients.The use of olfactory mucosa c...The review focuses on the most important areas of cell therapy for spinal cord injuries.Olfactory mucosa cells are promising for transplantation.Obtaining these cells is safe for patients.The use of olfactory mucosa cells is effective in restoring motor function due to the remyelination and regeneration of axons after spinal cord injuries.These cells express neurotrophic factors that play an important role in the functional recovery of nerve tissue after spinal cord injuries.In addition,it is possible to increase the content of neurotrophic factors,at the site of injury,exogenously by the direct injection of neurotrophic factors or their delivery using gene therapy.The advantages of olfactory mucosa cells,in combination with neurotrophic factors,open up wide possibilities for their application in threedimensional and four-dimensional bioprinting technology treating spinal cord injuries.展开更多
Bioprinting has been widely investigated for tissue engineering and regenerative medicine applications.However,it is still difficult to reconstruct the complex native cell arrangement due to the limited printing resol...Bioprinting has been widely investigated for tissue engineering and regenerative medicine applications.However,it is still difficult to reconstruct the complex native cell arrangement due to the limited printing resolution of conventional bioprinting techniques such as extrusion-and inkjet-based printing.Recently,an electrohydrodynamic(EHD)bioprinting strategy was reported for the precise deposition of well-organized cell-laden constructs with microscale filament size,whereas few studies have been devoted to developing bioinks that can be applied for EHD bioprinting and simultaneously support cell spreading.This study describes functionalized alginate-based bioinks for microscale EHD bioprinting using peptide grafting and fibrin incorporation,which leads to high cell viability(>90%)and cell spreading.The printed filaments can be further refined to as small as 30μm by incorporating polyoxyethylene and remained stable over one week when exposed to an aqueous environment.By utilizing the presented alginate-based bioinks,layer-specific cell alignment along the printing struts could be observed inside the EHD-printed microscale filaments,which allows fabricating living constructs with cell-scale filament resolution for guided cellular orientation.展开更多
The significance of bioink suitability for the extrusion bioprinting of tissue-like constructs cannot be overemphasized.Gelatin,derived from the hydrolysis of collagen,not only can mimic the extracellular matrix to imm...The significance of bioink suitability for the extrusion bioprinting of tissue-like constructs cannot be overemphasized.Gelatin,derived from the hydrolysis of collagen,not only can mimic the extracellular matrix to immensely support cell function,but also is suitable for extrusion under certain conditions.Thus,gelatin has been recognized as a promising bioink for extrusion bioprinting.However,the development of a gelatin-based bioink with satisfactory printability and bioactivity to fabricate complex tissue-like constructs with the desired physicochemical properties and biofunctions for a specific biomedical application is still in its infancy.Therefore,in this review,we aim to comprehensively summarize the state-of-the-art methods of gelatin-based bioink application for extrusion bioprinting.Wefirstly outline the properties and requirements of gelatin-based bioinks for extrusion bioprinting,highlighting the strategies to overcome their main limitations in terms of printability,structural stability and cell viability.Then,the challenges and prospects are further discussed regarding the development of ideal gelatin-based bioinks for extrusion bioprinting to create complex tissue-like constructs with preferable physicochemical properties and biofunctions.展开更多
Biomanufacturing of tissues/organs in vitro is our big dream,driven by two needs:organ transplantation and accurate tissue models.Over the last decades,3D bioprinting has been widely applied in the construction of man...Biomanufacturing of tissues/organs in vitro is our big dream,driven by two needs:organ transplantation and accurate tissue models.Over the last decades,3D bioprinting has been widely applied in the construction of many tissues/organs such as skins,vessels,hearts,etc.,which can not only lay a foundation for the grand goal of organ replacement,but also be served as in vitro models committed to pharmacokinetics,drug screening and so on.As organs are so complicated,many bioprinting methods are exploited to figure out the challenges of different applications.So the question is how to choose the suitable bioprinting method?Herein,we systematically review the evolution,process and classification of 3D bioprinting with an emphasis on the fundamental printing principles and commercialized bioprinters.We summarize and classify extrusion-based,dropletbased,and photocuring-based bioprinting methods and give some advices for applications.Among them,coaxial and multi-material bioprinting are highlighted and basic principles of designing bioinks are also discussed.展开更多
Three-dimensional(3D)bioprinting fabricates 3D functional tissues/organs by accurately depositing the bioink composed of the biological materials and living cells.Even though 3D bioprinting techniques have experienced...Three-dimensional(3D)bioprinting fabricates 3D functional tissues/organs by accurately depositing the bioink composed of the biological materials and living cells.Even though 3D bioprinting techniques have experienced significant advancement over the past decades,it remains challenging for 3D bioprinting to artificially fabricate functional tissues/organs with high post-printing cell viability and functionality since cells endure various types of stress during the bioprinting process.Generally,cell viability which is affected by several factors including the stress and the environmental factors,such as pH and temperature,is mainly determined by the magnitude and duration of the stress imposed on the cells with poorer cell viability under a higher stress and a longer duration condition.The maintenance of high cell viability especially for those vulnerable cells,such as stem cells which are more sensitive to multiple stresses,is a key initial step to ensure the functionality of the artificial tissues/organs.In addition,maintaining the pluripotency of the cells such as proliferation and differentiation abilities is also essential for the 3D-bioprinted tissues/organs to be similar to native tissues/organs.This review discusses various pathways triggering cell damage and the major factors affecting cell viability during different bioprinting processes,summarizes the studies on cell viabilities and functionalities in different bioprinting processes,and presents several potential approaches to protect cells from injuries to ensure high cell viability and functionality.展开更多
Three-dimensional(3D)tumor models prepared from patient-derived cells have been reported to imitate some of the biological development processes of in situ tumors in vitro.These 3D tumor models share several important...Three-dimensional(3D)tumor models prepared from patient-derived cells have been reported to imitate some of the biological development processes of in situ tumors in vitro.These 3D tumor models share several important characteristics with their in vivo tumor counterparts.Accordingly,their applications in tumor modeling,drug screening,and precision-targeted treatment are promising.However,the establishment of tumormodels is subject to several challenges,including advancements in scale size,repeatability,structural precision in time and space,vascularization,and the tumor microenvironment.Recently,bioprinting technologies enabling the editorial arrangement of cells,factors,and materials have improved the simulation of tumormodels in vitro.Among the 3D bioprinted tumor models,the organoidmodel has been widely appreciated for its advantages of maintaining high heterogeneity and capacity for simulating the developmental process of tumor tissues.In this review,we outline approaches and potential prospects for tumor model bioprinting and discuss the existing bioprinting technologies and bioinks in tumor model construction.The multidisciplinary combination of tumor pathology,molecular biology,material science,and additive manufacturing will help overcome the barriers to tumor model construction by allowing consideration of the structural and functional characteristics of in vitro models and promoting the development of heterogeneous tumor precision therapies.展开更多
Many studies have shown that bio-scaffolds have important value for promoting axonal regeneration of injured spinal cord.Indeed,cell transplantation and bio-scaffold implantation are considered to be effective methods...Many studies have shown that bio-scaffolds have important value for promoting axonal regeneration of injured spinal cord.Indeed,cell transplantation and bio-scaffold implantation are considered to be effective methods for neural regeneration.This study was designed to fabricate a type of three-dimensional collagen/silk fibroin scaffold (3D-CF) with cavities that simulate the anatomy of normal spinal cord.This scaffold allows cell growth in vitro and in vivo.To observe the effects of combined transplantation of neural stem cells (NSCs) and 3D-CF on the repair of spinal cord injury.Forty Sprague-Dawley rats were divided into four groups: sham (only laminectomy was performed),spinal cord injury (transection injury of T10 spinal cord without any transplantation),3D-CF (3D scaffold was transplanted into the local injured cavity),and 3D-CF + NSCs (3D scaffold co-cultured with NSCs was transplanted into the local injured cavity.Neuroelectrophysiology,imaging,hematoxylin-eosin staining,argentaffin staining,immunofluorescence staining,and western blot assay were performed.Apart from the sham group,neurological scores were significantly higher in the 3D-CF + NSCs group compared with other groups.Moreover,latency of the 3D-CF + NSCs group was significantly reduced,while the amplitude was significantly increased in motor evoked potential tests.The results of magnetic resonance imaging and diffusion tensor imaging showed that both spinal cord continuity and the filling of injury cavity were the best in the 3D-CF + NSCs group.Moreover,regenerative axons were abundant and glial scarring was reduced in the 3D-CF + NSCs group compared with other groups.These results confirm that implantation of 3D-CF combined with NSCs can promote the repair of injured spinal cord.This study was approved by the Institutional Animal Care and Use Committee of People’s Armed Police Force Medical Center in 2017 (approval No.2017-0007.2).展开更多
The three-dimensional (3D)bioprinting technology has progressed tremendously over the past decade.By controlling the size, shape,and architecture of the bioprinted constructs,3D bioprinting allows for the fabrication ...The three-dimensional (3D)bioprinting technology has progressed tremendously over the past decade.By controlling the size, shape,and architecture of the bioprinted constructs,3D bioprinting allows for the fabrication of tissue/organ-like constructs with strong structural-functional similarity with their in vivo counterparts at high fidelity.The bioink,a blend of biomaterials and living cells possessing both high biocompatibility and printability,is a critical component of bioprinting.In particular, gelatin methacryloyl (GelMA)has shown its potential as a viable bioink material due to its suitable biocompatibility and readily tunable physicochemical properties.Current GelMA-based bioinks and relevant bioprinting strategies for GelMA bioprinting are briefly reviewed.展开更多
Three-dimensional(3D)bioprinting is a rapidly growing technology that has been widely used in tissue engineering,disease studies,and drug screening.It provides the unprecedented capacity of depositing various types of...Three-dimensional(3D)bioprinting is a rapidly growing technology that has been widely used in tissue engineering,disease studies,and drug screening.It provides the unprecedented capacity of depositing various types of biomaterials,cells,and biomolecules in a layer-by-layer fashion,with precisely controlled spatial distribution.This technology is expected to address the organ-shortage issue in the future.In this review,we first introduce three categories of 3D bioprinting strategies:inkjet-based printing(IBP),extrusion-based printing(EBP),and light-based printing(LBP).Biomaterials and cells,which are normally referred to as“bioinks,”are then discussed.We also systematically describe the recent advancements of 3D bioprinting in fabricating cell-laden artificial tissues and organs with solid or hollow structures,including cartilage,bone,skin,muscle,vascular network,and so on.The development of organs-onchips utilizing 3D bioprinting technology for drug discovery and toxicity testing is reviewed as well.Finally,the main challenges in current studies and an outlook of the future research of 3D bioprinting are discussed.展开更多
Biomedical field has been seeking a feasible standard drug screening system consisting of 3D tumor model array for drug researching due to providing sufficient samples and simulating actual in vivo tumor growth situat...Biomedical field has been seeking a feasible standard drug screening system consisting of 3D tumor model array for drug researching due to providing sufficient samples and simulating actual in vivo tumor growth situation,which is still a challenge to rapidly and uniformly establish though.Here,we propose a novel drug screening system,namely 3D tumor array chip with“layer cake”structure,for drug screening.Accurate gelatin methacryloyl hydrogel droplets(~0.1μL)containing tumor cells can be automatically deposited on demand with electrohydrodynamic 3D printing.Transparent conductive membrane is introduced as a chip basement for preventing charges accumulation during fabricating and convenient observing during screening.Culturing chambers formed by stainless steel and silicon interlayer is convenient to be assembled and recycled.As this chip is compatible with the existing 96-well culturing plate,the drug screening protocols could keep the same as convention.Important properties of this chip,namely printing stability,customizability,accuracy,microenvironment,tumor functionalization,are detailly examined.As a demonstration,it is applied for screening of epirubicin and paclitaxel with breast tumor cells to confirm the compatibility of the proposed screening system with the traditional screening methods.We believe this chip will potentially play a significant role in drug evaluation in the future.展开更多
Three-dimensional(3D)extrusion-based bioprinting is widely used in tissue engineering and regenerative medicine to create cell-incorporated constructs or scaffolds based on the extrusion technique.One critical issue i...Three-dimensional(3D)extrusion-based bioprinting is widely used in tissue engineering and regenerative medicine to create cell-incorporated constructs or scaffolds based on the extrusion technique.One critical issue in 3D extrusion-based bioprinting is printability or the capability to form and maintain reproducible 3D scaffolds from bioink(a mixture of biomaterials and cells).Research shows that printability can be affected by many factors or parameters,including those associated with the bioink,printing process,and scaffold design,but these are far from certain.This review highlights recent developments in the printability assessment of extrusion-based bioprinting with a focus on the definition of printability,printability measurements and characterization,and printability-affecting factors.Key issues and challenges related to printability are also identified and discussed,along with approaches or strategies for improving printability in extrusion-based bioprinting.展开更多
Three-dimensional(3D)organoids derived from pluripotent or adult tissue stem cells seem to possess excellent potential for studying development and disease mechanisms alongside having a myriad of applications in regen...Three-dimensional(3D)organoids derived from pluripotent or adult tissue stem cells seem to possess excellent potential for studying development and disease mechanisms alongside having a myriad of applications in regenerative therapies.However,lack of precise architectures and large-scale tissue sizes are some of the key limitations of current organoid technologies.3D bioprinting of organoids has recently emerged to address some of these impediments.In this review,we discuss 3D bioprinting with respect to the use of bioinks and bioprinting methods and highlight recent studies that have shown success in bioprinting of stem cells and organoids.We also summarize the use of several vascularization strategies for the bioprinted organoids,that are critical for a complex tissue organization.To fully realize the translational applications of organoids in disease modeling and regenerative medicine,these areas in 3D bioprinting need to be appropriately harnessed and channelized.展开更多
Three-dimensional(3D)bioprinting based on traditional 3D printing is an emerging technology that is used to precisely assemble biocompatible materials and cells or bioactive factors into advanced tissue engineering so...Three-dimensional(3D)bioprinting based on traditional 3D printing is an emerging technology that is used to precisely assemble biocompatible materials and cells or bioactive factors into advanced tissue engineering solutions.Similar technology,particularly photo-cured bioprinting strategies,plays an important role in the field of tissue engineering research.The successful implementation of 3D bioprinting is based on the properties of photopolymerized materials.Photocrosslinkable hydrogel is an attractive biomaterial that is polymerized rapidly and enables process control in space and time.Photopolymerization is frequently initiated by ultraviolet(UV)or visible light.However,UV light may cause cell damage and thereby,affect cell viability.Thus,visible light is considered to be more biocompatible than UV light for bioprinting.In this review,we provide an overview of photo curing-based bioprinting technologies,and describe a visible light crosslinkable bioink,including its crosslinking mechanisms,types of visible light initiator,and biomedical applications.We also discuss existing challenges and prospects of visible light-induced 3D bioprinting devices and hydrogels in biomedical areas.展开更多
Three-dimensional(3D)bioprinting is a powerful approach that enables the fabrication of 3D tissue constructs that retain complex biological functions.However,the dense hydrogel networks that form after the gelation of...Three-dimensional(3D)bioprinting is a powerful approach that enables the fabrication of 3D tissue constructs that retain complex biological functions.However,the dense hydrogel networks that form after the gelation of bioinks often restrict the migration and proliferation of encapsulated cells.Herein,a sacrificial microgel-laden bioink strategy was designed for directly bioprinting constructs with mesoscale pore networks(MPNs)for enhancing nutrient delivery and cell growth.The sacrificial microgel-laden bioink,which contains cell/gelatin methacryloyl(GelMA)mixture and gelled gelatin microgel,is first thermo-crosslinked to fabricate temporary predesigned cell-laden constructs by extrusion bioprinting onto a cold platform.Then,the construct is permanently stabilized through photo-crosslinking of GelMA.The MPNs inside the printed constructs are formed after subsequent dissolution of the gelatin microgel.These MPNs allowed for effective oxygen/nutrient diffusion,facilitating the generation of bioactive tissues.Specifically,osteoblast and human umbilical vein endothelial cells encapsulated in the bioprinted large-scale constructs(≥1 cm)with MPNs showed enhanced bioactivity during culture.The 3D bioprinting strategy based on the sacrificial microgel-laden bioink provided a facile method to facilitate formation of complex tissue constructs with MPNs and set a foundation for future optimization of MPN-based tissue constructs with applications in diverse areas of tissue engineering.展开更多
基金supported by the National Natural Science Foundation of China,No.82171380(to CD)Jiangsu Students’Platform for Innovation and Entrepreneurship Training Program,No.202110304098Y(to DJ)。
文摘Spinal cord injury is considered one of the most difficult injuries to repair and has one of the worst prognoses for injuries to the nervous system.Following surgery,the poor regenerative capacity of nerve cells and the generation of new scars can make it very difficult for the impaired nervous system to restore its neural functionality.Traditional treatments can only alleviate secondary injuries but cannot fundamentally repair the spinal cord.Consequently,there is a critical need to develop new treatments to promote functional repair after spinal cord injury.Over recent years,there have been seve ral developments in the use of stem cell therapy for the treatment of spinal cord injury.Alongside significant developments in the field of tissue engineering,three-dimensional bioprinting technology has become a hot research topic due to its ability to accurately print complex structures.This led to the loading of three-dimensional bioprinting scaffolds which provided precise cell localization.These three-dimensional bioprinting scaffolds co uld repair damaged neural circuits and had the potential to repair the damaged spinal cord.In this review,we discuss the mechanisms underlying simple stem cell therapy,the application of different types of stem cells for the treatment of spinal cord injury,and the different manufa cturing methods for three-dimensional bioprinting scaffolds.In particular,we focus on the development of three-dimensional bioprinting scaffolds for the treatment of spinal cord injury.
基金supported by the National Natural Science Foundation of China(Nos.51975400 and 62031022)Shanxi Provincial Key Medical Scientific Research Project(Nos.2020XM06 and 2021XM12)+3 种基金Fundamental Research Program of Shanxi Province(No.202103021224081)Shanxi Provincial Basic Research Project(Nos.202103021221006 and 202103021223040)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2021L044)Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(No.2022SX-TD026).
文摘Traditional tumor models do not tend to accurately simulate tumor growth in vitro or enable personalized treatment and are particularly unable to discover more beneficial targeted drugs.To address this,this study describes the use of threedimensional(3D)bioprinting technology to construct a 3D model with human hepatocarcinoma SMMC-7721 cells(3DP-7721)by combining gelatin methacrylate(GelMA)and poly(ethylene oxide)(PEO)as two immiscible aqueous phases to form a bioink and innovatively applying fluorescent carbon quantum dots for long-term tracking of cells.The GelMA(10%,mass fraction)and PEO(1.6%,mass fraction)hydrogel with 3:1 volume ratio offered distinct pore-forming characteristics,satisfactorymechanical properties,and biocompatibility for the creation of the 3DP-7721 model.Immunofluorescence analysis and quantitative real-time fluorescence polymerase chain reaction(PCR)were used to evaluate the biological properties of the model.Compared with the two-dimensional culture cell model(2D-7721)and the 3D mixed culture cell model(3DM-7721),3DP-7721 significantly improved the proliferation of cells and expression of tumor-related proteins and genes.Moreover,we evaluated the differences between the three culture models and the effectiveness of antitumor drugs in the three models and discovered that the efficacy of antitumor drugs varied because of significant differences in resistance proteins and genes between the three models.In addition,the comparison of tumor formation in the three models found that the cells cultured by the 3DP-7721 model had strong tumorigenicity in nude mice.Immunohistochemical evaluation of the levels of biochemical indicators related to the formation of solid tumors showed that the 3DP-7721 model group exhibited pathological characteristics of malignant tumors,the generated solid tumors were similar to actual tumors,and the deterioration was higher.This research therefore acts as a foundation for the application of 3DP-7721 models in drug development research.
文摘Three-dimensional(3D)bioprinting is widely used in ophthalmic clinic,including in diagnosis,surgery,prosthetics,medications,drug development and delivery,and medical education.Articles published in 2011–2022 into bioinks,printing technologies,and bioprinting applications in ophthalmology were reviewed and the strengths and limitations of bioprinting in ophthalmology highlighted.The review highlighted the trade-offs of printing technologies and bioinks in respect to,among others,material type cost,throughput,gelation technique,cell density,cell viability,resolution,and printing speed.There is already widespread ophthalmological application of bioprinting outside clinical settings,including in educational modelling,retinal imaging/visualization techniques and drug design/testing.In clinical settings,bioprinting has already found application in pre-operatory planning.Even so,the findings showed that even with its immense promise,actual translation to clinical applications remains distant,but relatively closer for the corneal(except stromal)tissues,epithelium,endothelium,and conjunctiva,than it was for the retina.This review similarly reflected on the critical on the technical,practical,ethical,and cost barrier to rapid progress of bioprinting in ophthalmology,including accessibility to the most sophisticated bioprinting technologies,choice,and suitability of bioinks,tissue viability and storage conditions.The extant research is encouraging,but more work is clearly required for the push towards clinical translation of research.
文摘Among the different bioprinting techniques,the drop-on-demand(DOD)jetting-based bioprinting approach facilitates contactless deposition of pico/nanoliter droplets ofmaterials and cells for optimal cell–matrix and cell–cell interactions.Although bioinks play a critical role in the bioprinting process,there is a poor understanding of the influence of bioink properties on printing performance(such as filament elongation,formation of satellite droplets,and droplet splashing)and cell health(cell viability and proliferation)during the DOD jetting-based bioprinting process.An inert polyvinylpyrrolidone(PVP360,molecular weight=360 kDa)polymerwas used in this study to manipulate the physical properties of the bioinks and investigate the influence of bioink properties on printing performance and cell health.Our experimental results showed that a higher bioink viscoelasticity helps to stabilize droplet filaments before rupturing from the nozzle orifice.The highly stretched droplet filament resulted in the formation of highly aligned“satellite droplets,”which minimized the displacement of the satellite droplets away from the predefined positions.Next,a significant increase in the bioink viscosity facilitated droplet deposition on the wetted substrate surface in the absence of splashing and significantly improved the accuracy of the deposited main droplet.Further analysis showed that cell-laden bioinks with higher viscosity exhibited higher measured average cell viability(%),as the presence of polymer within the printed droplets provides an additional cushioning effect(higher energy dissipation)for the encapsulated cells during droplet impact on the substrate surface,improves the measured average cell viability even at higher droplet impact velocity and retains the proliferation capability of the printed cells.Understanding the influence of bioink properties(e.g.,bioink viscoelasticity and viscosity)on printing performance and cell proliferation is important for the formulation of new bioinks,and we have demonstrated precise DOD deposition of living cells and fabrication of tunable cell spheroids(nL–μL range)using multiple types of cells in a facile manner.
基金supported by the Major Science and Technology Special Project of Henan Province,China(No.171100210600)the Program of China Scholarship Council(No.201807045057)+2 种基金the High Level Talent Internationalization Training Program of Henan Province,China(No.2019004)the Scientific and Technological Research Project of Henan Province,China(Nos.212102310854 and 222102310526)the Open Foundation of the State Key Laboratory of Fluid Power and Mechatronic Systems(No.GZKF-202105)。
文摘Cryobioprinting has tremendous potential to solve problems to do with lack of shelf availability in traditional bioprinting by combining extrusion bioprinting and cryopreservation.In order to ensure the viability of cells in the frozen state and avoid the possible toxicity of dimethyl sulfoxide(DMSO),DMSO-free bioink design is critical for achieving successful cryobioprinting.A nontoxic gelatin methacryloyl-based bioink used in cryobioprinting is composed of cryoprotective agents(CPAs)and a buffer solution.The selection and ratio of CPAs in the bioink directly affect the survival of cells in the frozen state.However,the development of universal and efficient cryoprotective bioinks requires extensive experimentation.We first compared two commonly used CPA formulations via experiments in this study.Results show that the effect of using ethylene glycol as the permeable CPA was 6.07%better than that of glycerol.Two datasets were obtained and four machinelearning models were established to predict experimental outcomes.The predictive powers of multiple linear regression(MLR),decision tree(DT),random forest(RF),and artificial neural network(ANN)approaches were compared,suggesting an order of ANN>RF>DT>MLR.The final selected ANN model was then applied to another dataset.Results reveal that this machine-learning method can accurately predict the effects of cryoprotective bioinks composed of different CPAs.Outcomes also suggest that the formulations presented here have universality.Our findings are likely to greatly accelerate research and development on the use of bioinks for cryobioprinting.
基金the funding provided by the United Kingdom(UK)Engineering and Physical Sciences Research Council(EPSRC)Doctoral Prize Fellowship(EP/R513131/1)。
文摘Articular cartilage damage caused by trauma or degenerative pathologies such as osteoarthritis can result in significant pain,mobility issues,and disability.Current surgical treatments have a limited capacity for efficacious cartilage repair,and long-term patient outcomes are not satisfying.Three-dimensional bioprinting has been used to fabricate biochemical and biophysical environments that aim to recapitulate the native microenvironment and promote tissue regeneration.However,conventional in vitro bioprinting has limitations due to the challenges associated with the fabrication and implantation of bioprinted constructs and their integration with the native cartilage tissue.In situ bioprinting is a novel strategy to directly deliver bioinks to the desired anatomical site and has the potential to overcome major shortcomings associated with conventional bioprinting.In this review,we focus on the new frontier of robotic-assisted in situ bioprinting surgical systems for cartilage regeneration.We outline existing clinical approaches and the utilization of robotic-assisted surgical systems.Handheld and robotic-assisted in situ bioprinting techniques including minimally invasive and non-invasive approaches are defined and presented.Finally,we discuss the challenges and potential future perspectives of in situ bioprinting for cartilage applications.
文摘The review focuses on the most important areas of cell therapy for spinal cord injuries.Olfactory mucosa cells are promising for transplantation.Obtaining these cells is safe for patients.The use of olfactory mucosa cells is effective in restoring motor function due to the remyelination and regeneration of axons after spinal cord injuries.These cells express neurotrophic factors that play an important role in the functional recovery of nerve tissue after spinal cord injuries.In addition,it is possible to increase the content of neurotrophic factors,at the site of injury,exogenously by the direct injection of neurotrophic factors or their delivery using gene therapy.The advantages of olfactory mucosa cells,in combination with neurotrophic factors,open up wide possibilities for their application in threedimensional and four-dimensional bioprinting technology treating spinal cord injuries.
基金This work was financially supported by the National Key Research and Development Program of China(No.2018YFA0703003)the National Natural Science Foundation of China(No.52125501)+1 种基金the Key Research Project of Shaanxi Province(Nos.2021LLRH-08,2020GXLH-Y-021,and 2021GXLH-Z-028)the Youth InnovationTeam of Shaanxi Universities and the Fundamental Research Funds for the Central Universities.
文摘Bioprinting has been widely investigated for tissue engineering and regenerative medicine applications.However,it is still difficult to reconstruct the complex native cell arrangement due to the limited printing resolution of conventional bioprinting techniques such as extrusion-and inkjet-based printing.Recently,an electrohydrodynamic(EHD)bioprinting strategy was reported for the precise deposition of well-organized cell-laden constructs with microscale filament size,whereas few studies have been devoted to developing bioinks that can be applied for EHD bioprinting and simultaneously support cell spreading.This study describes functionalized alginate-based bioinks for microscale EHD bioprinting using peptide grafting and fibrin incorporation,which leads to high cell viability(>90%)and cell spreading.The printed filaments can be further refined to as small as 30μm by incorporating polyoxyethylene and remained stable over one week when exposed to an aqueous environment.By utilizing the presented alginate-based bioinks,layer-specific cell alignment along the printing struts could be observed inside the EHD-printed microscale filaments,which allows fabricating living constructs with cell-scale filament resolution for guided cellular orientation.
基金support for this work from the National Key R&D Program of China(No.2018YFA0703100)the National Natural Sci-ence Foundation of China(Nos.32122046,82072082,and 32000959)+2 种基金the Youth Innovation Promotion Association of CAS(No.2019350)the Guangdong Natural Science Foundation(No.2019A1515111197)the Shenzhen Fundamental Research Foun-dation(Nos.JCYJ20190812162809131,JCYJ20200109114006014,JCYJ20210324113001005,and JCYJ20210324115814040).
文摘The significance of bioink suitability for the extrusion bioprinting of tissue-like constructs cannot be overemphasized.Gelatin,derived from the hydrolysis of collagen,not only can mimic the extracellular matrix to immensely support cell function,but also is suitable for extrusion under certain conditions.Thus,gelatin has been recognized as a promising bioink for extrusion bioprinting.However,the development of a gelatin-based bioink with satisfactory printability and bioactivity to fabricate complex tissue-like constructs with the desired physicochemical properties and biofunctions for a specific biomedical application is still in its infancy.Therefore,in this review,we aim to comprehensively summarize the state-of-the-art methods of gelatin-based bioink application for extrusion bioprinting.Wefirstly outline the properties and requirements of gelatin-based bioinks for extrusion bioprinting,highlighting the strategies to overcome their main limitations in terms of printability,structural stability and cell viability.Then,the challenges and prospects are further discussed regarding the development of ideal gelatin-based bioinks for extrusion bioprinting to create complex tissue-like constructs with preferable physicochemical properties and biofunctions.
基金sponsored by the National Natural Science Foundation of China(No.U1609207)。
文摘Biomanufacturing of tissues/organs in vitro is our big dream,driven by two needs:organ transplantation and accurate tissue models.Over the last decades,3D bioprinting has been widely applied in the construction of many tissues/organs such as skins,vessels,hearts,etc.,which can not only lay a foundation for the grand goal of organ replacement,but also be served as in vitro models committed to pharmacokinetics,drug screening and so on.As organs are so complicated,many bioprinting methods are exploited to figure out the challenges of different applications.So the question is how to choose the suitable bioprinting method?Herein,we systematically review the evolution,process and classification of 3D bioprinting with an emphasis on the fundamental printing principles and commercialized bioprinters.We summarize and classify extrusion-based,dropletbased,and photocuring-based bioprinting methods and give some advices for applications.Among them,coaxial and multi-material bioprinting are highlighted and basic principles of designing bioinks are also discussed.
文摘Three-dimensional(3D)bioprinting fabricates 3D functional tissues/organs by accurately depositing the bioink composed of the biological materials and living cells.Even though 3D bioprinting techniques have experienced significant advancement over the past decades,it remains challenging for 3D bioprinting to artificially fabricate functional tissues/organs with high post-printing cell viability and functionality since cells endure various types of stress during the bioprinting process.Generally,cell viability which is affected by several factors including the stress and the environmental factors,such as pH and temperature,is mainly determined by the magnitude and duration of the stress imposed on the cells with poorer cell viability under a higher stress and a longer duration condition.The maintenance of high cell viability especially for those vulnerable cells,such as stem cells which are more sensitive to multiple stresses,is a key initial step to ensure the functionality of the artificial tissues/organs.In addition,maintaining the pluripotency of the cells such as proliferation and differentiation abilities is also essential for the 3D-bioprinted tissues/organs to be similar to native tissues/organs.This review discusses various pathways triggering cell damage and the major factors affecting cell viability during different bioprinting processes,summarizes the studies on cell viabilities and functionalities in different bioprinting processes,and presents several potential approaches to protect cells from injuries to ensure high cell viability and functionality.
基金The authors appreciated the financial support from the National Key R&D Program of China(No.2018YFA0703000)the National Natural Science Foundation of China(No.82072412)+2 种基金the Translation Medicine National Key Science and Technology Infrastructure(Shanghai)Open Project(No.TMSK-2020-118)the Lingang Laboratory“Seeking Outstanding Youth Program”Open Project(No.LG-QS-202206-04)the Shanghai Municipal Natural Science Foundation(No.19ZR1429100).
文摘Three-dimensional(3D)tumor models prepared from patient-derived cells have been reported to imitate some of the biological development processes of in situ tumors in vitro.These 3D tumor models share several important characteristics with their in vivo tumor counterparts.Accordingly,their applications in tumor modeling,drug screening,and precision-targeted treatment are promising.However,the establishment of tumormodels is subject to several challenges,including advancements in scale size,repeatability,structural precision in time and space,vascularization,and the tumor microenvironment.Recently,bioprinting technologies enabling the editorial arrangement of cells,factors,and materials have improved the simulation of tumormodels in vitro.Among the 3D bioprinted tumor models,the organoidmodel has been widely appreciated for its advantages of maintaining high heterogeneity and capacity for simulating the developmental process of tumor tissues.In this review,we outline approaches and potential prospects for tumor model bioprinting and discuss the existing bioprinting technologies and bioinks in tumor model construction.The multidisciplinary combination of tumor pathology,molecular biology,material science,and additive manufacturing will help overcome the barriers to tumor model construction by allowing consideration of the structural and functional characteristics of in vitro models and promoting the development of heterogeneous tumor precision therapies.
基金supported by the National Natural Science Foundation of China,No.11672332(to XYC)the National Key Research and Development Plan of China,No.2016YFC1101500(to SZ)
文摘Many studies have shown that bio-scaffolds have important value for promoting axonal regeneration of injured spinal cord.Indeed,cell transplantation and bio-scaffold implantation are considered to be effective methods for neural regeneration.This study was designed to fabricate a type of three-dimensional collagen/silk fibroin scaffold (3D-CF) with cavities that simulate the anatomy of normal spinal cord.This scaffold allows cell growth in vitro and in vivo.To observe the effects of combined transplantation of neural stem cells (NSCs) and 3D-CF on the repair of spinal cord injury.Forty Sprague-Dawley rats were divided into four groups: sham (only laminectomy was performed),spinal cord injury (transection injury of T10 spinal cord without any transplantation),3D-CF (3D scaffold was transplanted into the local injured cavity),and 3D-CF + NSCs (3D scaffold co-cultured with NSCs was transplanted into the local injured cavity.Neuroelectrophysiology,imaging,hematoxylin-eosin staining,argentaffin staining,immunofluorescence staining,and western blot assay were performed.Apart from the sham group,neurological scores were significantly higher in the 3D-CF + NSCs group compared with other groups.Moreover,latency of the 3D-CF + NSCs group was significantly reduced,while the amplitude was significantly increased in motor evoked potential tests.The results of magnetic resonance imaging and diffusion tensor imaging showed that both spinal cord continuity and the filling of injury cavity were the best in the 3D-CF + NSCs group.Moreover,regenerative axons were abundant and glial scarring was reduced in the 3D-CF + NSCs group compared with other groups.These results confirm that implantation of 3D-CF combined with NSCs can promote the repair of injured spinal cord.This study was approved by the Institutional Animal Care and Use Committee of People’s Armed Police Force Medical Center in 2017 (approval No.2017-0007.2).
基金the National Institutes of Health (K99CA201603,R21EB025270, R21EB026175)Doctoral New Investigator Grant from American Chemical Society Petroleum Research Fund (56840-DNI7).G.L. Y.acknowledges Natural and Science Foundation of Hubei Province (2014CFB778).
文摘The three-dimensional (3D)bioprinting technology has progressed tremendously over the past decade.By controlling the size, shape,and architecture of the bioprinted constructs,3D bioprinting allows for the fabrication of tissue/organ-like constructs with strong structural-functional similarity with their in vivo counterparts at high fidelity.The bioink,a blend of biomaterials and living cells possessing both high biocompatibility and printability,is a critical component of bioprinting.In particular, gelatin methacryloyl (GelMA)has shown its potential as a viable bioink material due to its suitable biocompatibility and readily tunable physicochemical properties.Current GelMA-based bioinks and relevant bioprinting strategies for GelMA bioprinting are briefly reviewed.
基金The authors would like to acknowledge support from the National Natural Science Foundation of China(51875518,51475419,and 81501607)the Natural Science Foundation of Zhejiang Province of China(LY15H160019)the Key Research and Development Projects of Zhejiang Province(2017C01054).
文摘Three-dimensional(3D)bioprinting is a rapidly growing technology that has been widely used in tissue engineering,disease studies,and drug screening.It provides the unprecedented capacity of depositing various types of biomaterials,cells,and biomolecules in a layer-by-layer fashion,with precisely controlled spatial distribution.This technology is expected to address the organ-shortage issue in the future.In this review,we first introduce three categories of 3D bioprinting strategies:inkjet-based printing(IBP),extrusion-based printing(EBP),and light-based printing(LBP).Biomaterials and cells,which are normally referred to as“bioinks,”are then discussed.We also systematically describe the recent advancements of 3D bioprinting in fabricating cell-laden artificial tissues and organs with solid or hollow structures,including cartilage,bone,skin,muscle,vascular network,and so on.The development of organs-onchips utilizing 3D bioprinting technology for drug discovery and toxicity testing is reviewed as well.Finally,the main challenges in current studies and an outlook of the future research of 3D bioprinting are discussed.
基金This work was sponsored by the National Nature Science Foundation of China(No.U1609207)the National Key Research and Development Program of China(2018YFA0703000)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.51521064).
文摘Biomedical field has been seeking a feasible standard drug screening system consisting of 3D tumor model array for drug researching due to providing sufficient samples and simulating actual in vivo tumor growth situation,which is still a challenge to rapidly and uniformly establish though.Here,we propose a novel drug screening system,namely 3D tumor array chip with“layer cake”structure,for drug screening.Accurate gelatin methacryloyl hydrogel droplets(~0.1μL)containing tumor cells can be automatically deposited on demand with electrohydrodynamic 3D printing.Transparent conductive membrane is introduced as a chip basement for preventing charges accumulation during fabricating and convenient observing during screening.Culturing chambers formed by stainless steel and silicon interlayer is convenient to be assembled and recycled.As this chip is compatible with the existing 96-well culturing plate,the drug screening protocols could keep the same as convention.Important properties of this chip,namely printing stability,customizability,accuracy,microenvironment,tumor functionalization,are detailly examined.As a demonstration,it is applied for screening of epirubicin and paclitaxel with breast tumor cells to confirm the compatibility of the proposed screening system with the traditional screening methods.We believe this chip will potentially play a significant role in drug evaluation in the future.
基金The authors acknowledge financial support from the Natural Sciences and Engineering Research Council of Canada(NSERC,Grant No.:RGPIN-2014-05648).
文摘Three-dimensional(3D)extrusion-based bioprinting is widely used in tissue engineering and regenerative medicine to create cell-incorporated constructs or scaffolds based on the extrusion technique.One critical issue in 3D extrusion-based bioprinting is printability or the capability to form and maintain reproducible 3D scaffolds from bioink(a mixture of biomaterials and cells).Research shows that printability can be affected by many factors or parameters,including those associated with the bioink,printing process,and scaffold design,but these are far from certain.This review highlights recent developments in the printability assessment of extrusion-based bioprinting with a focus on the definition of printability,printability measurements and characterization,and printability-affecting factors.Key issues and challenges related to printability are also identified and discussed,along with approaches or strategies for improving printability in extrusion-based bioprinting.
文摘Three-dimensional(3D)organoids derived from pluripotent or adult tissue stem cells seem to possess excellent potential for studying development and disease mechanisms alongside having a myriad of applications in regenerative therapies.However,lack of precise architectures and large-scale tissue sizes are some of the key limitations of current organoid technologies.3D bioprinting of organoids has recently emerged to address some of these impediments.In this review,we discuss 3D bioprinting with respect to the use of bioinks and bioprinting methods and highlight recent studies that have shown success in bioprinting of stem cells and organoids.We also summarize the use of several vascularization strategies for the bioprinted organoids,that are critical for a complex tissue organization.To fully realize the translational applications of organoids in disease modeling and regenerative medicine,these areas in 3D bioprinting need to be appropriately harnessed and channelized.
基金supported by the Key-Area Research and Development Program of Guangdong Province(2019B010941001)the Shenzhen Double Chain Project for Innovation and Development Industry supported by the Bureau of Industry and Information Technology of Shenzhen(201908141541)Shenzhen Fundamental Research Foundation(GJHZ20170314154845576 and GJHS20170314161106706).
文摘Three-dimensional(3D)bioprinting based on traditional 3D printing is an emerging technology that is used to precisely assemble biocompatible materials and cells or bioactive factors into advanced tissue engineering solutions.Similar technology,particularly photo-cured bioprinting strategies,plays an important role in the field of tissue engineering research.The successful implementation of 3D bioprinting is based on the properties of photopolymerized materials.Photocrosslinkable hydrogel is an attractive biomaterial that is polymerized rapidly and enables process control in space and time.Photopolymerization is frequently initiated by ultraviolet(UV)or visible light.However,UV light may cause cell damage and thereby,affect cell viability.Thus,visible light is considered to be more biocompatible than UV light for bioprinting.In this review,we provide an overview of photo curing-based bioprinting technologies,and describe a visible light crosslinkable bioink,including its crosslinking mechanisms,types of visible light initiator,and biomedical applications.We also discuss existing challenges and prospects of visible light-induced 3D bioprinting devices and hydrogels in biomedical areas.
基金sponsored by the National Nature Science Foundation of China(Nos.U1609207,81827804).
文摘Three-dimensional(3D)bioprinting is a powerful approach that enables the fabrication of 3D tissue constructs that retain complex biological functions.However,the dense hydrogel networks that form after the gelation of bioinks often restrict the migration and proliferation of encapsulated cells.Herein,a sacrificial microgel-laden bioink strategy was designed for directly bioprinting constructs with mesoscale pore networks(MPNs)for enhancing nutrient delivery and cell growth.The sacrificial microgel-laden bioink,which contains cell/gelatin methacryloyl(GelMA)mixture and gelled gelatin microgel,is first thermo-crosslinked to fabricate temporary predesigned cell-laden constructs by extrusion bioprinting onto a cold platform.Then,the construct is permanently stabilized through photo-crosslinking of GelMA.The MPNs inside the printed constructs are formed after subsequent dissolution of the gelatin microgel.These MPNs allowed for effective oxygen/nutrient diffusion,facilitating the generation of bioactive tissues.Specifically,osteoblast and human umbilical vein endothelial cells encapsulated in the bioprinted large-scale constructs(≥1 cm)with MPNs showed enhanced bioactivity during culture.The 3D bioprinting strategy based on the sacrificial microgel-laden bioink provided a facile method to facilitate formation of complex tissue constructs with MPNs and set a foundation for future optimization of MPN-based tissue constructs with applications in diverse areas of tissue engineering.
