Axon-like aligned conductive CNT/GelMA hydrogel fibers combined with electrical stimulation for spinal cord injury recovery

Rehabilitation and regenerative medicine are two promising approaches for spinal cord injury(SCI)recovery,but their combination has been limited.Conductive biomaterials could bridge regenerative scaffolds with electrical stimulation by inducing axon regeneration and supporting physiological electrical signal transmission.Here,we developed aligned conductive hydrogel fibers by incorporating carbon nanotubes(CNTs)into methacrylate acylated gelatin(GelMA)hydrogel via rotating liquid bath electrospinning.The electrospun CNT/GelMA hydrogel fibers mimicked the micro-scale aligned structure,conductivity,and soft mechanical properties of neural axons.For in vitro studies,CNT/GelMA hydrogel fibers supported PC12 cell proliferation and aligned adhesion,which was enhanced by electrical stimulation(ES).Similarly,the combination of aligned CNT/GelMA hydrogel fibers and ES promoted neuronal differentiation and axon-like neurite sprouting in neural stem cells(NSCs).Furthermore,CNT/GelMA hydrogel fibers were transplanted into a T9 transection rat spinal cord injury model for in vivo studies.The results showed that the incorporating CNTs could remain at the injury site with the GelMA fibers biodegraded and improve the conductivity of regenerative tissue.The aligned structure of the hydrogel could induce the neural fibers regeneration,and the ES enhanced the remyelination and axonal regeneration.Behavioral assessments and electrophysiological results suggest that the combination of aligned CNT/GelMA hydrogel fibers and ES could significantly restore motor function in rats.This study demonstrates that conductive aligned CNT/GelMA hydrogel fibers can not only induce neural regeneration as a scaffold but also support ESto promote spinal cord injury recovery.The conductive hydrogel fibers enable merging regenerative medicine and rehabilitation,showing great potential for satisfactory locomotor recovery after SCI.

Drug-nanoencapsulated PLGA microspheres prepared by emulsion electrospray with controlled release behavior

The development of modern therapeutics has raised the requirement for controlled drug delivery system which is able to efficiently encapsulate bioactive agents and achieve their release at a desired rate satisfying the need of the practical system.In this study,two kind of aqueous model drugs with different molecule weight,Congo red and albumin from bovine serum(BSA)were nanoencapsulated in poly(DL-lactic-co-glycolic acid)(PLGA)microspheres by emulsion electrospray.In the preparation process,the aqueous phase of drugs was added into the PLGA chloroform solution to form the emulsion solution.The emulsion was then electrosprayed to fabricate drugnanoencapsulated PLGA microspheres.The morphology of the PLGA microspheres was affected by the volume ratio of aqueous drug phase and organic PLGA phase(V_(w)/V_(o))and the molecule weight of model drugs.Confocal laser scanning microcopy showed the nanodroplets of drug phase were scattered in the PLGA microspheres homogenously with different distribution patterns related to V_(w)/V_(o).With the increase of the volume ratio of aqueous drug phase,the number of nanodroplets increased forming continuous phase gradually that could accelerate drug release rate.Moreover,BSA showed a slower release rate from PLGA microspheres comparing to Congo red,which indicated the drug release rate could be affected by not only V_(w)/V_(o)but also the molecule weight of model drug.In brief,the PLGA microspheres prepared using emulsion electrospray provided an efficient and simple systemto achieve controlled drug release at a desired rate satisfying the need of the practices.

Aligned fibrin/functionalized self-assembling peptide interpenetrating nanofiber hydrogel presenting multi-cues promotes peripheral nerve functional recovery

Nerve guidance conduits with hollow lumen fail to regenerate critical-sized peripheral nerve defects(15 mm in rats and 25 mm in humans),which can be improved by a beneficial intraluminal microenvironment.However,individual cues provided by intraluminal filling materials are inadequate to eliminate the functional gap between regenerated nerves and normal nerves.Herein,an aligned fibrin/functionalized self-assembling peptide(AFG/fSAP)interpenetrating nanofiber hydrogel that exerting synergistic topographical and biochemical cues for peripheral nerve regeneration is constructed via electrospinning and molecular self-assembly.The hydrogel possesses an aligned structure,high water content,appropriate mechanical properties and suitable biodegradation capabilities for nerve repair,which enhances the alignment and neurotrophin secretion of primary Schwann cells(SCs)in vitro,and successfully bridges a 15-mm sciatic nerve gap in rats in vivo.The rats transplanted with the AFG/fSAP hydrogel exhibit satisfactory morphological and functional recovery in myelinated nerve fibers and innervated muscles.The motor function recovery facilitated by the AFG/fSAP hydrogel is comparable with that of autografts.Moreover,the AFG/fSAP hydrogel upregulates the regeneration-associated gene expression and activates the PI3K/Akt and MAPK signaling pathways in the regenerated nerve.Altogether,the AFG/fSAP hydrogel represents a promising approach for peripheral nerve repair through an integration of structural guidance and biochemical stimulation.

Gene expression profiling and mechanism study of neural stem cells response to surface chemistry

To declare the mechanisms of neural stem cells(NSCs)in response to material surface chemistry,NSCs were exposed to the self-assemble monolayers of alkanethiolates on gold surfaces terminated with amine(NH2),hydroxyl(OH)and methyl(CH3)for analysis.The morphological responses of NSCs were recorded;the gene expression profilings were detected by genechips;the gene expressions data of NSCs responded to different chemical groups were declared through the gene ontology term and pathway analyses.It showed that cells behaved dissimilar on the three chemical groups,the adhesion,proliferation and migration were easier on the NH2 and OH groups;the gene expressions of NSCs were induced differently,either,involved in several functional processes and signaling pathways.CH3 group induced genes enriched much in chemistry reactions and death processes,whereas many genes of cellular nucleotide metabolism were down-regulated.NH2 group induced NSCs to express many genes of receptors on membrane,and participated in cellular signal transduction of cell adhesion and interactions,or associated with axon growth.OH group was similar to NH2 group to induce the membrane response,but it also down regulated metabolism of cells.Therefore,it declared the chemical groups affected NSCs through inner way and the NH2,OH and CH3 groups triggered the cellular gene expression in different signaling pathways.

Development of an antimicrobial peptide-loaded mineralized collagen bone scaffold for infective bone defect repair

The repair of infective bone defects is a great challenge in clinical work.It is of vital importance to develop a kind of bone scaffold with good osteogenic properties and long-term antibacterial activity for local anti-infection and bone regeneration.A porous mineralized collagen(MC)scaffold containing poly(D,L-lactide-co-glycolic acid)(PLGA)microspheres loaded with two antibacterial synthetic peptides,Pac-525 or KSL-W was developed and characterized via scanning electron microscopy(SEM),porosity measurement,swelling and mechanical tests.The results showed that the MC scaffold embedded with smooth and compact PLGA microspheres had a positive effect on cell growth and also had antibacterial properties.Through toxicity analysis,cell morphology and proliferation analysis and alkaline phosphatase evaluation,the antibacterial scaffolds showed excellent biocompatibility and osteogenic activity.The antibacterial property evaluated with Staphylococcus aureus and Escherichia coli suggested that the sustained release of Pac-525 or KSL-W from the scaffolds could inhibit the bacterial growth aforementioned in the long term.Our results suggest that the antimicrobial peptides-loaded MC bone scaffold has good antibacterial and osteogenic activities,thus providing a great promise for the treatment of infective bone defects.

Regulation of RAW 264.7 macrophages behavior on anodic TiO2 nanotubular arrays

Titanium （Ti） implants with TiO2 nanotubular arrays on the surface could regulate cells adhesion, proliferation and differentiation to determine the bone integra- tion. Additionally, the regulation of immune cells could improve osteogenesis or lead in appropriate immune reaction. Thus, we evaluate the behavior of RAW 264.7 macrophages on TiO2 nanotubular arrays with a wide range diameter （from 20 to 120 nm） fabricated by an electrochemical anodization process. In this work, the proliferation, cell viability and cytokine/chemokine secretion were evaluated by CCK-8, live/dead staining and ELISA, respectively. SEM and confocal microscopy were used to observe the adhesion morphology. Results showed that the small size nanotube surface was benefit for the macrophages adhesion and proliferation, while larger size surface could reduce the inflammatory response. These findings contribute to the design of immune-regulating Ti implants surface that supports successful implantation.

White matter regeneration induced by aligned fibrin nanofiber hydrogel contributes to motor functional recovery in canine T12 spinal cord injury

A hierarchically aligned fibrin hydrogel(AFG)that possesses soft stiffness and aligned nanofiber structure has been successfully proven to facilitate neuroregeneration in vitro and in vivo.However,its potential in promoting nerve regeneration in large animal models that is critical for clinical translation has not been sufficiently specified.Here,the effects of AFG on directing neuroregeneration in canine hemisected T12 spinal cord injuries were explored.Histologically obvious white matter regeneration consisting of a large area of consecutive,compact and aligned nerve fibers is induced by AFG,leading to a significant motor functional restoration.The canines with AFG implantation start to stand well with their defective legs from 3 to 4 weeks postoperatively and even effortlessly climb the steps from 7 to 8 weeks.Moreover,high-resolution multi-shot diffusion tensor imaging illustrates the spatiotemporal dynamics of nerve regeneration rapidly crossing the lesion within 4 weeks in the AFG group.Our findings indicate that AFG could be a potential therapeutic vehicle for spinal cord injury by inducing rapid white matter regeneration and restoring locomotion,pointing out its promising prospect in clinic practice.