A novel artificial nerve graft for repairing longdistance sciatic nerve defects:a self-assembling peptide nanofiber scaffold-containing poly (lactic-co-glycolic acid) conduit

In this study, we developed a novel artificial nerve graft termed self-assembling peptide nanofiber scaffold （SAPNS）-containing poly（lactic-co-glycolic acid） （PLGA） conduit （SPC） and used it to bridge a 10-mm-long sciatic nerve defect in the rat. Retrograde tracing, behavioral testing and histomorphometric analyses showed that compared with the empty PLGA conduit implantation group, the SPC implantation group had a larger number of growing and extending axons, a markedly increased diameter of regenerated axons and a greater thickness of the myelin sheath in the conduit. Furthermore, there was an increase in the size of the neuromuscular junction and myofiber diameter in the target muscle. These findings suggest that the novel artificial SPC nerve graft can promote axonal regeneration and remyelination in the transected peripheral nerve and can be used for repairing peripheral nerve injury.

Optimization of nanofiber scaffold properties towards nerve guidance channel design

Nerve guidance channels are limited by lack of topographical guidance：Treatment of sizeable nerve gaps remains problematic following peripheral nerve injury.Functional outcomes are good when neurorrhaphy,or direct end-to-end suture repair,is possible.The problem arises when there is significant segmental loss,which can occur following trauma as well as oncological procedures.

Robust Alcohol Soluble Polyurethane/Chitosan/Silk Sericin(APU/CS/SS)Nanofiber Scaffolds Toward Artificial Skin Extracellular Matrices via Microfluidic Blow‑Spinning

Skin regeneration is a matter of high concern since many individuals suffer from skin damage.To date,the concept of protein-based artificial skin scaffolds have been successfully applied and proven in skin regeneration.However,realizing a skin tissue scaffold with a skin-like extracellular matrix(ECM)that combines low price,good biocompatibility,excellent antibacterial properties,good cell adhesion,and strong mechanical properties is still a major challenge.In this study,inexpensive silk sericin(SS)protein-based artificial skin nanofiber scaffolds(NFSs)with excellent biological activity,no immune rejection,and high mechanical strength were fabricated via microfluidic blow-spinning(MBS).In particular,the as-prepared NFS was transformed from a random coil structure to aβ-sheet structure by using the MBS in high-speed shear chips to improve its stability and mechanical strength.Additionally,through in vitro and in vivo studies,it was shown that SS protein-based artificial skin NFSs possessed excellent antibacterial effects and degradability properties,as well as accelerated tissue granu-lation growth,effectively promoting full skin wound healing and skin regeneration for medical problems worldwide.Thus,this skin ECM-inspired NFS offers new perspectives for accelerating wound healing and tissue regeneration and provides potential applications for clinical medicine.

Crimped nanofiber scaffold mimicking tendon-to-bone interface for fatty-infiltrated massive rotator cuff repair

Electrospun fibers,with proven ability to promote tissue regeneration,are widely being explored for rotator cuff repairing.However,without post treatment,the microstructure of the electrospun scaffold is vastly different from that of natural extracellular matrix(ECM).Moreover,during mechanical loading,the nanofibers slip that hampers the proliferation and differentiation of migrating stem cells.Here,electrospun nanofiber scaffolds,with crimped nanofibers and welded joints to biomimic the intricate natural microstructure of tendon-to-bone insertion,were prepared using poly(ester-urethane)urea and gelatin via electrospinning and double crosslinking by a multi-bonding network densification strategy.The crimped nanofiber scaffold(CNS)features bionic tensile stress and induces chondrogenic differentiation,laying credible basis for in vivo experimentation.After repairing a rabbit massive rotator cuff tear using a CNS for 3 months,the continuous translational tendon-to-bone interface was fully regenerated,and fatty infiltration was simultaneously inhibited.Instead of micro-CT,μCT was employed to visualize the integrity and intricateness of the three-dimensional microstructure of the CNS-induced-healed tendon-to-bone interface at an ultra-high resolution of less than 1μm.This study sheds light on the correlation between nanofiber post treatment and massive rotator cuff repair and provides a general strategy for crimped nanofiber preparation and tendon-to-bone interface imaging characterization.

Modeling the density gradient of 3D nanofiber scaffolds fabricated by divergence electrospinning

Following recent insights on structure-cell-function interactions and the critical role of the extracellular matrix(ECM),the latest biofabrication approaches have increasingly focused on designing materials with biomimetic microarchitecture.Divergence electrospinning is a novel fabrication method for three-dimensional(3D)nanofiber scaffolds.It is introduced to produce 3D nanofiber mats that have numerous applications in regenerative medicine and tissue engineering.One of the most important characteristics of 3D nanofiber mats is the density gradient.This study provides a statistical analysis and response surface modeling framework based on experimental data to evaluate the manner by which the geometric designs of double-bevel collectors influence the fiber density gradient.Specifically,variance of analysis and sensitivity analysis were performed to identify parameters that had significant effects,and a response surface model embedded with seven location indicators was developed to predict the spatial distribution of fiber density for different collector designs.It was concluded that the collector height,bevel angle,and their interactions were significant factors influencing the density gradient.This study revealed the sensitivity of system configuration and provided an optimization tool for process controllability of microstructure gradients.

Photothermal‑Triggered Structural Change of Nanofiber Scaffold Integrating with Graded Mineralization to Promote Tendon–Bone Healing

Scaffolds functionalized with graded changes in both fiber alignment and mineral content are more appealing for tendon-bone healing.This study reports the healing of rotator cuff injury using a heterogeneous nanofiber scaffold,which is associated with a structural gradating from aligned to random and an increasing gradient of mineral content in the same orientation.The photothermal-triggered structural change of a nanofiber scaffold followed by graded mineralization is key to constructing such scaffolds.This type of scaffold was found to be biocompatible and provide beneficial contact guidance in the manipulation of tendon-derived stem cell morphologies in vitro.Specifically,tenogenic and osteogenic differentiation of tendon-derived stem cells were simultaneously achieved using the fabricated scaffold.In vivo investigation also showed the improved healing of rabbit rotator cuff injuries based on immunohistochemical analysis and biomechanical investigation that indicates the promising potential of a dual-gradient nanofiber scaffold in clinical tendon-bone healing.

Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue Engineering Applications

The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.

介孔生物活性玻璃/聚己内酯短纤维骨组织工程支架体外抑炎功能研究

目的利用介孔生物活性玻璃纳米颗粒(mesoporous bioactive glass nanoparticles,MBGN)增强聚己内酯(poly⁃capro⁃lactone,PCL)静电纺丝纳米纤维制备3D骨组织工程支架,并探究该支架材料的体外抑炎功能。方法通过静电纺丝获得PCL静电纺丝膜,溶胶-凝胶法制得MBGN。经过分散、均质化、筛选、冻干、明胶热自组装、羧甲基壳聚糖表面修饰等步骤,制备得到MBGN增强PCL静电纺丝纳米纤维3D骨组织工程(bone tissue engineering,BTE)支架PCL@MBGN。扫描电镜、能谱仪等检测支架表征。CCK⁃8法和活死细胞染色法检测支架的生物相容性。采用脂多糖(lipopolysaccharide,LPS)刺激RAW264.7细胞12 h,诱导巨噬细胞向M1型极化后用含不同MBGN添加量的PCL@MBGN支架浸提液刺激细胞48 h,流式细胞术检测M1、M2型巨噬细胞特征性表面标记分子CD86、CD206表达水平,并使用qRT⁃PCR法检测炎性相关细胞因子肿瘤坏死因子⁃α(tumor necrosis factor alpha,TNF⁃α)、白细胞介素1β(interleukin⁃1 beta,IL⁃1β)、白细胞介素4(interleukin⁃4,IL⁃4)、诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOs)的转录水平。结果随着MBGN添加量增加,扫描电镜下支架表面球状微粒增加,但没有显著影响支架的宏观形貌。PCL@MBGN在体外不仅拥有良好的生物相容性,而且可抑制LPS诱导的促炎型M1巨噬细胞极化,CD86表达降低(P<0.05),在一定程度上促进抑炎型M2巨噬细胞极化,CD206表达增高(P<0.05);抑制IL⁃1β、TNF⁃α、iNOs等促炎细胞因子的基因转录(P<0.05),同时还促进抑炎细胞因子IL⁃4表达(P<0.05),发挥体外免疫调节作用。结论本研究成功制备了具有3D结构的纳米纤维支架PCL@MBGN,MBGN的加入没有显著影响支架的形貌且支架无细胞毒性,具有抑炎作用。PCL@MBGN在炎症环境下的骨缺损修复中具有很大的应用前景。