Current researches on design and manufacture of biopolymer-based osteochondral biomimetic scaffolds

Currently,osteochondral(OC)tissue engineering has become a potential treatment strategy in repairing chondral lesions and early osteoarthritis due to the limited self-healing ability of cartilage.However,it is still challenging to ensure the integrity,physiological function and regeneration ability of stratified OC scaffolds in clinical application.Biomimetic OC scaffolds are attractive to overcome the above problems because of their similar biological and mechanical properties with native OC tissue.As a consequence,the researches on biomimetic design to achieve the tissue function of each layer,and additive manufacture(AM)to accomplish composition switch and ultrastructure of personalized OC scaffolds have made a remarkable progress.In this review,the design methods of biomaterial and structure as well as computer-aided design,and performance prediction of biopolymer-based OC scaffolds are presented;then,the characteristics and limitations of AM technologies and the integrated manufacture schemes in OC tissue engineering are summarized;finally,the novel biomaterials and techniques and the inevitable trends of multifunctional bio-manufacturing system are discussed for further optimizing production of tissue engineering OC scaffolds.

3D/4D printed bio-piezoelectric smart scaffolds for next-generation bone tissue engineering

Piezoelectricity in native bones has been well recognized as the key factor in bone regeneration.Thus,bio-piezoelectric materials have gained substantial attention in repairing damaged bone by mimicking the tissue’s electrical microenvironment(EM).However,traditional manufacturing strategies still encounter limitations in creating personalized bio-piezoelectric scaffolds,hindering their clinical applications.Three-dimensional(3D)/four-dimensional(4D)printing technology based on the principle of layer-by-layer forming and stacking of discrete materials has demonstrated outstanding advantages in fabricating bio-piezoelectric scaffolds in a more complex-shaped structure.Notably,4D printing functionality-shifting bio-piezoelectric scaffolds can provide a time-dependent programmable tissue EM in response to external stimuli for bone regeneration.In this review,we first summarize the physicochemical properties of commonly used bio-piezoelectric materials(including polymers,ceramics,and their composites)and representative biological findings for bone regeneration.Then,we discuss the latest research advances in the 3D printing of bio-piezoelectric scaffolds in terms of feedstock selection,printing process,induction strategies,and potential applications.Besides,some related challenges such as feedstock scalability,printing resolution,stress-to-polarization conversion efficiency,and non-invasive induction ability after implantation have been put forward.Finally,we highlight the potential of shape/property/functionality-shifting smart 4D bio-piezoelectric scaffolds in bone tissue engineering(BTE).Taken together,this review emphasizes the appealing utility of 3D/4D printed biological piezoelectric scaffolds as next-generation BTE implants.

Degradation modeling of degradable copolymers for biomimetic scaffolds

Biomimetic scaffolds provide a suitable growth environment for tissue engineering and demonstrate good potential for application in biomedical fields.Different-sized copolymerized biomimetic scaffolds degrade differently,and the degradation rate is affected by the copolymerization ratio.The study of the degradation property is the foundational research necessary for realizing individualized biomimetic scaffold design.The degradation performance of polyesters with different copolymerization ratios has been widely reported;however,the modeling of this performance has been rarely reported.In this research,the degradation of copolymers was studied with multi-scale modeling,in which the copolymers were dispersed in a cellular manner,the chain break time was simulated,and the chain selection was based on the Monte Carlo(MC)algorithm.The probability model of the copolymer's chain break position was established as a//roulette,/model,whose probability values were estimated by the calculation of the potential energy difference at different chain break positions by molecular dynamics that determined the position of chain shear,thereby fully realizing the simulation of the chain micro-break process.The diffusion of the oligomers was then calculated using the macro diffusion equation,and the degradation process of the copolymer was simulated by three-scale coupling calculations.The calculation results were in good agreement with the experimental data,demonstrating the effectiveness of the proposed method.

Biomimetic microstructural scaffolds and their applications in tissue engineering

The dynamic structures of extracellular matrix regulate cell behaviors by providing three-dimension ecological niche and mechanical cues.Under the progress of both surface patterning and biomaterials,the cues of micro-and nanoscale topography on microstructural scaffold biomaterials are increasingly recognized as decisive factors of biomimetic materials.In this review,we provide an overview of the recent progress of biomimetic microstructured scaffolds,including advances in their biomimetic manufacturing technology,functionality,potential applications and future challenges.We highlight recent progress in the fabrication of microstructured scaffold materials with various biological and physicochemical characteristics of native extracellular matrix.The recent key advances of microstructured scaffold for tissue engineering,bio-adhesive,antibacterial and biosensing applications were offered.Eventually,we summarize by offering our perspective on this fast-growing field.

Novel structural designs of 3D-printed osteogenic graft for rapid angiogenesis

Large bone defect regeneration has always been recognized as a challenging clinical problem due to the difficulty of revascularization.Conventional treatments exhibit certain inherent disadvantages(e.g.,secondary injury,immunization,and potential infections).However,three-dimensional(3D)printing technology as an emerging field can serve as an effective approach to achieve satisfactory revascularization while making up for the above limitations.A wide variety of methods can be used to facilitate blood supply during the design of a 3D-printed scaffold.Importantly,the scaffold structure lays a foundation for the entire printing object;any method to promote angiogenesis can be effective only if it is based on well-designed scaffolds.In this review,different designs related to angiogenesis are summarized by collecting the literature from recent years.The 3D-printed scaffolds are classified into four major categories and discussed in detail,from elementary porous scaffolds to the most advanced bone-like scaffolds.Finally,structural design suggestions to achieve rapid angiogenesis are proposed by analyzing the above architectures.This review can provide a reference for organizations or individual academics to achieve improved bone defect repair and regeneration using 3D printing.

From the microspheres to scaffolds:advances in polymer microsphere scaffolds for bone regeneration applications

The treatment and repair of bone tissue damage and loss due to infection,tumours,and trauma are major challenges in clinical practice.Artificial bone scaffolds offer a safer,simpler,and more feasible alternative to bone transplantation,serving to fill bone defects and promote bone tissue regeneration.Ideally,these scaffolds should possess osteoconductive,osteoinductive,and osseointegrative properties.However,the current first-generation implants,represented by titanium alloys,have shown poor bone-implant integration performance and cannot meet the requirements for bone tissue repair.This has led to increased research on second and third generation artificial bone scaffolds,which focus on loading bioactive molecules and cells.Polymer microspheres,known for their high specific surface areas at the micro-and nanoscale,exhibit excellent cell and drug delivery behaviours.Additionally,with their unique rigid structure,microsphere scaffolds can be constructed using methods such as thermal sintering,injection,and microsphere encapsulation.These scaffolds not only ensure the excellent cell drug loading performance of microspheres but also exhibit spatial modulation behaviour,aiding in bone repair within a three-dimensional network structure.This article provides a summary and discussion of the use of polymer microsphere scaffolds for bone repair,focusing on the mechanisms of bone tissue repair and the current status of clinical bone grafts,aimed at advancing research in bone repair.

Biomimetic microchannel network with functional endothelium formed by sacrificial electrospun fibers inside 3D gelatin methacryloyl(GelMA)hydrogel models

Three-dimensional(3D)hydrogel models play a crucial role in tissue engineering for promoting tissue regeneration.A biomimetic microchannel network system in the 3D hydrogel model is necessary for optimal cellular function.This report describes the preparation of a biomimetic hydrogel scaffold with an internal microchannel network,using electrospinning techniques and the sacrificial template method for 3D cell culture.Microchannels and cavities were created within the gelatin methacryloyl(GelMA)hydrogel by sacrificing polyvinyl alcohol(PVA)electrospun fibers(>10µm),resulting in the creation of microvessel-like channels.Mechanical characterizations,swelling properties,and biodegradation analysis were conducted to investigate the feasibility of a biomimetic microchannel network hydrogel scaffold for 3D cell culture applications.Compared to pure GelMA hydrogel,the hydrogel with microchannels promoted cell proliferation,adhesion,and endothelial tube formation.Moreover,the results confirmed that the biomimetic microchannel network scaffold had a major impact on the distribution and arrangement of human umbilical vein endothelial cells(HUVECs)and can enable the formation of artificial microvasculature by the culture of HUVECs and cell media perfusion.

Mesenchymal stem cells,secretome and biomaterials in in-vivo animal models:Regenerative medicine application in cutaneous wound healing

The treatment of nonhealing and chronic cutaneous wounds still needs a clinical advancement to be effective.Both mesenchymal stem cells(MSCs),obtained from different sources,and their secretome derived thereof(especially exosomes)can activate signaling pathways related to promotion of cell migration,vascularization,collagen deposition,and inflammatory response demonstrating prohealing,angiogenetic and anti-scarring capacities.On the other hand,biodegradable biomimetic scaffolds can facilitate endogenous cell attachment and proliferation as well as extracellular matrix production.In this Review,we revise the complex composites made by biomimetic scaffolds,mainly hydrogels,and MSC-derived exosomes constructed for cutaneous wound healing.Studies demonstrate that there exists a synergistic action of scaffolds with encapsulated exosomes,displaying a sustained release profiles to facilitate longlasting healing effects.It can be envisioned that dressings made by biomimetic hydrogels and MSC-derived exosomes will be clinically applied in the near future for the effective treatment of nonhealing and chronic wounds.

Advances and prospects in biomimetic multilayered scaffolds for articular cartilage regeneration

Due to the sophisticated hierarchical structure and limited reparability of articular cartilage(AC),the ideal regeneration of AC defects has been a major challenge in the field of regenerative medicine.As defects progress,they often extend from the cartilage layer to the subchondral bone and ultimately lead to osteoarthritis.Tissue engineering techniques bring new hope for AC regeneration.To meet the regenerative requirements of the heterogeneous and layered structure of native AC tissue,a substantial number of multilayered biomimetic scaffolds have been studied.Ideal multilayered scaffolds should generate zone-specific functional tissue similar to native AC tissue.This review focuses on the current status of multilayered scaffolds developed for AC defect repair,including design strategies based on the degree of defect severity and the zone-specific characteristics of AC tissue,the selection and composition of biomaterials,and techniques for design and manufacturing.The challenges and future perspectives of biomimetic multilayered scaffold strategies for AC regeneration are also discussed.

Three-dimensional collagen-based scaffold model to study the microenvironment and drug-resistance mechanisms of oropharyngeal squamous cell carcinomas

Objective:Squamous cell carcinoma(SCC)represents the most common histotype of all head and neck malignancies and includes oropharyngeal squamous cell carcinoma(OSCC),a tumor associated with different clinical outcomes and linked to human papilloma virus(HPV)status.Translational research has few available in vitro models with which to study the different pathophysiological behavior of OSCCs.The present study proposes a 3-dimensional(3 D)biomimetic collagen-based scaffold to mimic the tumor microenvironment and the crosstalk between the extracellular matrix(ECM)and cancer cells.Methods:We compared the phenotypic and genetic features of HPV-positive and HPV-negative OSCC cell lines cultured on common monolayer supports and on scaffolds.We also explored cancer cell adaptation to the 3 D microenvironment and its impact on the efficacy of drugs tested on cell lines and primary cultures.Results:HPV-positive and HPV-negative cell lines were successfully grown in the 3 D model and displayed different collagen fiber organization.The 3 D cultures induced an increased expression of markers related to epithelial–mesenchymal transition(EMT)and to matrix interactions and showed different migration behavior,as confirmed by zebrafish embryo xenografts.The expression of hypoxia-inducible factor 1α(1α)and glycolysis markers were indicative of the development of a hypoxic microenvironment inside the scaffold area.Furthermore,the 3 D cultures activated drug-resistance signaling pathways in both cell lines and primary cultures.Conclusions:Our results suggest that collagen-based scaffolds could be a suitable model for the reproduction of the pathophysiological features of OSCCs.Moreover,3 D architecture appears capable of inducing drug-resistance processes that can be studied to better our understanding of the different clinical outcomes of HPV-positive and HPV-negative patients with OSCCs.

TGF-beta 1 Gene-Activated Matrices Regulated the Osteogenic Differentiation of BMSCs

Poly （lactic acid/glycolic acid/asparagic acid-co-polyethylene glycol）（PLGA-[ASP-PEG]） scaffold materials were linked with a novel nonviral vector （K）16GRGDSPC through cross linker Sulfo- LC-SPDP to construct a new type of nonviral gene transfer system. Eukaryotic expressing vector containing transforming growth factor beta 1 （pcDNA3-TGFβ1） was encapsulated by the system. Bone marrow stromal cells （BMSCs） obtained from rabbit were cultured on PLGA-[ASP-PEG] modified by （K）16GRGDSPC and TGF-β1 gene and PLGA-[ASP-PEG] modified by （K）16GRGDSPC and empty vector pcDNA3 as control. The expressions of osteogenic makers of the BMSCs cultured on the TGF-β1 gene-activated scaffold materials were found significantly higher than those of the control group （P〈0.05）. A brand-new way was provided for regulating seed cells to directionally differentiate into osteoblasts for bone defect restoration in bone tissue engineering.

A novel electrospinning method for self-assembled tree-like fibrous scaffolds:Microenvironment-associated regulation of MSC behavior and bone regeneration

Numerous studies highlight advantages of electrospun scaffolds in bone tissue engineering,in which cellular behavior is tightly affected by fiber topographical cues of scaffolds.However,the classic electrospinning setup limits a desired presentation of biomimetic fibrous microenvironments that sense mechanosignaling and regulate stem cell behavior.The aims of this study were to fabricate advanced asspun scaffolds presenting tree-like microfiber/nanonet networks and to evaluate their regulatory potentials on behavior of human mesenchymal stem cells(h MSCs)and bone regeneration.Here we developed a novel electrospinning setup that allowed the presentation of patterned Trunk microfibers(TMF)and/or branched nanonet fibers(BNn Fs)in biomimetic fibrous scaffolds.As the cellular mechanisms,anisotropichierarchical topography of TMF controlled behavior of h MSCs through focal adhesion formation and Yesassociated protein(YAP)induction,whereas BNn F disturbed such mechanosensing responses in the cells.The fiber microenvironment-related expression and nuclear localization of YAP were.also correlated with the potentials of as-spun scaffolds to enhance osteogenic differentiation of the h MSCs and alveolar bone defect healing in an animal model.Collectively,this study provides an advanced approach of the modified electrospinning setup for presentation of biomimetic fibrillar microenvironments in as-spun scaffolds along with their application in stem cell behavior regulation and regenerative tissue engineering.

3D-printed cell-free PCL-MECM scaffold with biomimetic micro-structure and micro-environment to enhance in situ meniscus regeneration

Despite intensive effort was made to regenerate injured meniscus by cell-free strategies through recruiting endogenous stem/progenitor cells,meniscus regeneration remains a great challenge in clinic.In this study,we found decellularized meniscal extracellular matrix(MECM)preserved native meniscal collagen and glycosaminoglycans which could be a good endogenous regeneration guider for stem cells.Moreover,MECM significantly promoted meniscal fibrochondrocytes viability and proliferation,increased the expression of type II collagen and proteoglycans in vitro.Meanwhile,we designed 3D-printed polycaprolactone(PCL)scaffolds which mimic the circumferential and radial collagen orientation in native meniscus.Taken these two advantages together,a micro-structure and micro-environment dually biomimetic cell-free scaffold was manipulated.This cell-free PCL-MECM scaffold displayed superior biocompatibility and yielded favorable biomechanical capacities closely to native meniscus.Strikingly,neo-menisci were regenerated within PCL-MECM scaffolds which were transplanted into knee joints underwent medial meniscectomy in rabbits and sheep models.Histological staining confirmed neo-menisci showed meniscus-like heterogeneous staining.Mankin scores showed PCL-MECM scaffold could protect articular cartilage well,and knee X-ray examination revealed same results.Knee magnetic resonance imaging(MRI)scanning also showed some neo-menisci in PCL-MECM scaffold group.In conclusion,PCL-MECM scaffold appears to optimize meniscus regeneration.This could represent a promising approach worthy of further investigation in preclinical applications.

Remote control of the recruitment and capture of endogenous stem cells by ultrasound for in situ repair of bone defects

Stem cell-based tissue engineering has provided a promising platform for repairing of bone defects.However,the use of exogenous bone marrow mesenchymal stem cells(BMSCs)still faces many challenges such as limited sources and potential risks.It is important to develop new approach to effectively recruit endogenous BMSCs and capture them for in situ bone regeneration.Here,we designed an acoustically responsive scaffold(ARS)and embedded it into SDF-1/BMP-2 loaded hydrogel to obtain biomimetic hydrogel scaffold complexes(BSC).The SDF-1/BMP-2 cytokines can be released on demand from the BSC implanted into the defected bone via pulsed ultrasound(p-US)irradiation at optimized acoustic parameters,recruiting the endogenous BMSCs to the bone defected or BSC site.Accompanied by the daily p-US irradiation for 14 days,the alginate hydrogel was degraded,resulting in the exposure of ARS to these recruited host stem cells.Then another set of sinusoidal continuous wave ultrasound(s-US)irradiation was applied to excite the ARS intrinsic resonance,forming highly localized acoustic field around its surface and generating enhanced acoustic trapping force,by which these recruited endogenous stem cells would be captured on the scaffold,greatly promoting them to adhesively grow for in situ bone tissue regeneration.Our study provides a novel and effective strategy for in situ bone defect repairing through acoustically manipulating endogenous BMSCs.

A conductive supramolecular hydrogel creates ideal endogenous niches to promote spinal cord injury repair

The current effective method for treatment of spinal cord injury(SCI)is to reconstruct the biological microenvironment by filling the injured cavity area and increasing neuronal differentiation of neural stem cells(NSCs)to repair SCI.However,the method is characterized by several challenges including irregular wounds,and mechanical and electrical mismatch of the material-tissue interface.In the current study,a unique and facile agarose/gelatin/polypyrrole(Aga/Gel/PPy,AGP3)hydrogel with similar conductivity and modulus as the spinal cord was developed by altering the concentration of Aga and PPy.The gelation occurred through non-covalent interactions,and the physically crosslinked features made the AGP3 hydrogels injectable.In vitro cultures showed that AGP3 hydrogel exhibited excellent biocompatibility,and promoted differentiation of NSCs toward neurons whereas it inhibited over-proliferation of astrocytes.The in vivo implanted AGP3 hydrogel completely covered the tissue defects and reduced injured cavity areas.In vivo studies further showed that the AGP3 hydrogel provided a biocompatible microenvironment for promoting endogenous neurogenesis rather than glial fibrosis formation,resulting in significant functional recovery.RNA sequencing analysis further indicated that AGP3 hydrogel significantly modulated expression of neurogenesis-related genes through intracellular Ca2+signaling cascades.Overall,this supramolecular strategy produces AGP3 hydrogel that can be used as favorable biomaterials for SCI repair by filling the cavity and imitating the physiological properties of the spinal cord.