Porous Silk Fibroin Scaffolds Research Articles

Modulation of Biophysical Cues in Nature Inspired Patterning of Porous Silk Fibroin Scaffold for Replenishable Controlled Drug Delivery.

In our daily lives, cuts and wounds are unavoidable. while they are generally minor, sometimes they do turn serious. While a sticking plaster might be enough in most cases, critical situations like surgical wounds, lacerations, gunshot wounds, accidental skin injuries, diabetic wounds, and other cutaneous deep cuts may require implants and simultaneous medications for healing. From the biophysical standpoint one of the least explored aspects to surmount these hurdles is the internal force-based physical surface stimulus crucial for cellular sensing at the time of wound repair. With more people needing medical attention for wound healing, smart patches will be an integral part of the future generation of wound treatment. We report fabrication of a novel biomimetically patterned silk fibroin porous scaffold with an approach to ampicillin loading and replenishment by joining a polytetrafluoroethylene (PTFE) catheter attached 18G butterfly intravenous infusion needle at the bottom of the substrates. In vitro swelling study reveals that the patterned substrates show less swelling compared to that of the other variants and consequently less in vitro degradation. The ampicillin release patterns from the scaffolds follows the Korsemeyer-Peppas model depicting surface hydrophobicity mediated non-fickian first-order anomalous controlled release. The scaffolds show remarkable antibacterial efficacy against Methicillin-Resistant Staphylococcus aureus (MRSA) and Escherichia coli. Four distinct cell-matrix adhesion regimes were investigated for the fibroblasts to eventually form cell sheets all over the hierarchical surface structures. The fluorescence images after DAPI and FDA staining clearly demonstrates that the patterned surface to be superior to its other variants. A comparative study among molecular expressions of collagen I, vinculin, and vimentin using immunofluorescence, substantiated the patterned surface to be superior to others. The work report potential development of a deep cutaneous wound healing drug replenishable implant with biophysical cues capable of controlling fibroblast behavior and release kinetics of ampicillin. This article is protected by copyright. All rights reserved.

Effect of silk fibroin scaffold loaded with 17-β estradiol on the proliferation and differentiation of BMSCs.

In this study, different concentrations of 17-β estradiol silk fibroin (SF)porous scaffolds (SFPS) were prepared using freeze-drying technique, with a hope for optimal concentration and apply it locally to the bone defect area. In this study, the porous scaffold morphology structure was characterized by SEM, FTIR and universal capacity testing machines, and the invitro cytocompatibility and biological activity of scaffold materials were studied by cell adhesion, viability and proliferation experiments. The results showed that SFPS boasts better physicochemical properties, while 17-β estradiol SF scaffolds with low concentrations of 10-10mol/L and 10-12mol/L had more growth and proliferation of SF scaffolds with higher concentrations, and 10-10mol/L was the optimal concentration of 17-β estradiol SFPS, which was more conducive to cell adhesion and proliferation. On the other hand, after osteogenesis induction of BMSCs inoculated on 17-β estradiol SFPS at different concentrations, it was found that the expression of alkaline phosphatase in BMSCs on different concentrations of 17-β estradiol porous scaffolds was not large. No conflict of interest exits in the submission of this manuscript.

Development of bilayered porous silk scaffolds for thymus bioengineering

The thymus coordinates the development and selection of T cells. It is structured into two main compartments: the cortex and the medulla. The replication of such complex 3D environment has been challenged by bioengineering approaches. Nevertheless, the effect of the scaffold microstructure on thymic epithelial cell (TEC) cultures has not been deeply investigated. Here, we developed bilayered porous silk fibroin scaffolds and tested their effect on TEC co-cultures. The small and large pore scaffolds presented a mean pore size of 84.33 ± 21.51 μm and 194.90 ± 61.38 μm, respectively. The highly porous bilayered scaffolds presented a high water absorption and water content (> 94 %), together with mechanical properties in the range of the native tissue. TEC (i.e., medullary (mTEC) and cortical (cTEC) cell lines) proliferation is increased in scaffolds with larger pores. The co-culture of both TEC lines in the bilayered porous silk scaffolds presents enhanced cell proliferation and metabolic activity when compared with mTEC in single culture. Also, when the co-culture occurred with cTEC in the small pores layer and mTEC in the large pores layer, a 9.2- and 18.9-fold increase in Foxn1 and Icam1 gene expression in cTEC is evident. These results suggest that scaffold microstructure and the co-culture influence TEC's behaviour. Bilayered silk scaffolds with adjusted microstructure are a valid alternative for TEC culture, having possible applications in advanced thymus bioengineering strategies.

Preliminary study of silk fibroin porous scaffold for oral soft-tissue thickening.

This study aimed to investigate the feasibility of three different concentrations of silk-fibroin porous scaffolds applied to oral soft-tissue thickening in vivo. Silk-fibroin scaffolds with three different concentrations (1 wt%, 3 wt%, and 5 wt%; denoted as SF1, SF3, and SF5, respectively) were prepared by freeze drying and methanol enhancement. The scaffolds were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis. Pore size, porosity, and in vitro degradation rate were also evaluated. The three groups of scaffold materials (the experimental sides) and the collagen matrix (the control side) were implanted into the oral mucosa of New Zealand white rabbits. Changed in mucosa thickness before and 3 months after operation were compared. The in vivo metabolism and regeneration effect of each group were observed by histological hematoxylin-eosin (HE) and Masson staining. SEM showed that the three groups of scaffolds were all cross-linked porous structures. XRD and FTIR showed that the three scaffolds were dominated by a relatively stable Silk Ⅱ structure, which degraded more slowly in vitro. Among them, SF3 had the largest pore size (133.40 μm±22.85 μm) and moderate porosity (90.05%±6.68%). In vivo results showed that the thickening effect of SF1 was similar to that of the control group because of insufficient space-maintenance property. Meanwhile, the properties of SF3 and SF5 were more stable, and the thickening effect was significantly better than those of the control group. However, unlike SF5 that induced obvious inflammation, SF3 showed better degradation, more fibrosis and angiogenesis, and less inflammatory response in vivo. Silk-fibroin scaffolds can be applied to effectively thicken soft tissues, among which SF3 (3 wt%) silk fibroin scaffold exhibited the best physicochemical properties, histocompatibility, and mucosal-thickening effect.

Developing a novel calcium magnesium silicate/graphene oxide incorporated silk fibroin porous scaffold with enhanced osteogenesis, angiogenesis and inhibited osteoclastogenesis

Recently, biofunctional ions (Mg2+, Si4+, etc) and graphene derivatives are proved to be promising in stimulating bone formation. In this study, a novel inorganic/organic composite porous scaffold based on silk fibroin (SF), graphene oxide (GO), and calcium magnesium silicate (CMS) was developed for bone repair. The porous scaffolds obtained by lyophilization showed a little difference in pore structure while GO and CMS displayed a good interaction with SF matrix. The addition of CMS with good mineralization potential and sustainedly release ability of biofunctional ions (Ca2+, Mg2+ and Si4+) increased the strength of SF scaffolds a little and facilitated the osteogenic differentiation of bone mesenchymal stem cells (BMSCs) by upregulating bone formation-related genes (ALP, COL1, OC and Runx2). The further incorporation of GO in SF scaffolds enhanced the compressive strength and water retention, and also remarkably promoted the osteogenic differentiation of BMSCs. Besides, the angiogenesis of human umbilical vein endothelial cells was significantly promoted by CMS/GO/SF scaffold extract through the upregulation of angiogenesis genes (eNOs and bFGF). Moreover, the osteoclastic formation ability of RAW264.7 cells was suppressed by the released ions from CMS/GO/SF scaffold through the down-regulation of CAK, MMP9 and TRAP. The promoted osteogenesis, angiogenesis and inhibited osteoclastogenesis functions of CMS/GO/SF composite scaffold may enable it as a novel therapy for bone repair and regeneration.

The stiffness variability of a silk fibroin scaffold during bone cell proliferation.

Complex assessment of gradual changes in scaffold morphology and stiffness is an essential step in bone filler development. Current approach, however, does not reflect long term cell proliferation effect as the mechanical tests are usually conducted on pristine materials without cells or cell influence on material stiffness is evaluated after one time period only. Here, biocompatible silk fibroin (SF) porous scaffolds envisioned for bone defect filling were prepared by dissolving of fibroin fibers, followed by dialysis, freeze-drying and final stabilization. Particular attention was devoted to the influence of bone cell proliferation up to 2 months on the stiffness of the material. The morphology of the material was studied in terms of its inner structure and the overall changes in the surface characteristics due to proliferation of MG 63 bone cell line. The SF scaffold stiffness significantly increased during first month followed by its decline during second month due to bone cell seeding. After 2 months, the SF scaffold was completely colonized, which resulted in a gradual decay of its structure. The length of degradation due to bone cell proliferation and mechanical behavior corresponded to the requirements set for reasonable filler material indicating that porous SF scaffolds comprise a promising biomaterial for bone regeneration.

Radially Aligned Porous Silk Fibroin Scaffolds as Functional Templates for Engineering Human Biomimetic Hepatic Lobules.

Bioengineering functional hepatic tissue constructs that physiologically replicate the human native liver tissue in vitro is sought for clinical research and drug discovery. However, the intricate architecture and specific biofunctionality possessed by the native liver tissue remain challenging to mimic in vitro. In the present study, a versatile strategy to fabricate lobular-like silk protein scaffolds with radially aligned lamellar sheets, interconnected channels, and a converging central cavity was designed and implemented. A proof-of-concept study to bioengineer biomimetic hepatic lobules was conducted through coculturing human hepatocytes and primary endothelial cells on these lobular-like scaffolds. Relatively long-term viability of hepatocyte/endothelial cells was found along with cell alignment and organization in vitro. The hepatocytes showed special epithelial polarity and bile duct formation, similar to the liver plate, while the aligned endothelial cells generated endothelial networks, similar to natural hepatic sinuses. This endowed the three-dimensional (3D) tissue constructs with the capability to recapitulate hepatic-like parenchymal-mesenchymal growth patterns in vitro. More importantly, the cocultured hepatocytes outperformed monocultures or monolayer cultures, displaying significantly enhanced hepatocyte functions, including functional gene expression, albumin (ALB) secretion, urea synthesis, and metabolic activity. Thus, this functional unit with a biomimetic phenotype provides a novel technology for bioengineering biomimetic hepatic lobules in vitro, with potential utility as a building block for bioartificial liver (BAL) engineering or as a robust tool for drug metabolism investigation.

Fabrication of Silk Scaffold Containing Simvastatin-Loaded Silk Fibroin Nanoparticles for Regenerating Bone Defects

Background:In the present study, a tissue engineered SF scaffold containing simvastatin-loaded SFNPs were used to stimulate the regeneration of the defected bone.Methods:At first, the porous SF scaffold was prepared using freeze-drying. Then simvastatin-loaded SFNPs were made by dissolvation method and embedded in the SF scaffold. Afterwards, the scaffold and the NPs were characterized in terms of physicochemical properties and the ability to release the simvastatin small molecule.Results:The results exhibited that the SF scaffold had a porous structure suitable for releasing the small molecule and inducing the proliferation and attachment of osteoblast cells. SFNPs containing simvastatin had spherical morphology and were 174 ± 4 nm in size with -24.5 zeta potential. Simvastatin was also successfully encapsulated within the SFNPs with 68% encapsulation efficiency. Moreover, the small molecule revealed a sustained release profile from the NPs during 35 days. The results obtained from the in vitro cell-based studies indicated that simvastatin-loaded SFNPs embedded in the scaffold had acceptable capacity to promote the proliferation and ALP production of osteoblast cells while inducing osteogenic matrix precipitation. Conclusion:The SF scaffold containing simvastatin-loaded SFNPs could have a good potential to be used as a bone tissue-engineered construct.

Silk Fibroin Scaffolds as Biomaterials for 3D Mesenchymal Stromal Cells Cultures

Silk fibroin (SF), a protein-based fiber extracted from Bombyx mori cocoons, has recently emerged with great potential for the biomedical field to be used as a biomaterial processable in a variety of formats and applications, due to its natural characteristics. The aims of the present study were to characterize the structural properties of the SF scaffolds, in the format of porous sponges, and to investigate their feasibility to support the adhesion of mesenchymal stromal/stem cells isolated from human Wharton’s jelly of the umbilical cord (WJ-MSC). Adhesion is a prerequisite for using the SF scaffold as biomaterial for supporting three-dimensional (3D) WJ-MSC cultures for several applications. The integration among micro-computed tomography, confocal analysis, and field emission scanning electron microscopy allowed carrying out a deep investigation based on quantitative morphological parameters and qualitative observations at high resolution. High levels of porosity, interconnection, and contact surface–volume ratio confirmed the appropriateness of the designed SF porous scaffolds as supports for cell cultures. WJ-MSC was demonstrated to be capable of adhering to and colonizing the SF scaffold applicable as a 3D cell culture system, of conducting in vitro experiments in a more controlled environment, and possibly of being used in tissue engineering, regenerative medicine, and applications in oncology.

A New Strategy for the Preparation of Porous Silk Fibroin Scaffolds

In order to prepare Silk Fibroin (SF) scaffolds with excellent pore structure, the fresh SF solution was concentrated at relative humidity 55% and 25°C for 3 days. During the above process, SF micelles, existed in the fresh SF solution, aggregated into nanofilaments as concentration increased, and the nanofilament feature of SF were similar to that observed in silk gland. SF nanofilaments were easy to form SF scaffolds with porous and silk I structure, in contrary, SF micelles were liable for formation of SF scaffolds with lamellar and random coil structure. It suggested that the formation of SF nanofilaments is a critical step for pore and secondary structure control of lyophilized SF scaffolds.

Improved Mesenchymal Stem Cell Proliferation, Differentiation, Epithelial Transition, and Restrained Senescence on Hierarchically Patterned Porous Honey Silk Fibroin Scaffolds.

We report a significant improvement of adipose-derived mesenchymal stem cells' (ADMSCs) biocompatibility and proliferation on hierarchically patterned porous honey-incorporated silk fibroin scaffolds fabricated using a combination of soft lithography and freeze-drying techniques. Parametric variations show enhanced surface roughness, swelling, and degradation rate with good pore interconnectivity, porosity, and mechanical strength for soft-lithographically fabricated biomimetic microdome arrays on the 2% honey silk fibroin scaffold (PHSF2) as compared to its other variants, which eventually made PHSF2 more comparable to the native environment required for stem cell adhesion and proliferation. PHSF2 also exhibits sustained honey release with remarkable antibacterial efficacy against methicillin-resistant Staphylococcus aureus (MRSA). Honey incorporation (biochemical cue) influences microdome structural features, that is, biophysical cues (height, width, and periodicity), which further allows ADMSCs pseudopods (filopodia) to grasp the microdomes for efficient cell-cell communication and cell-matrix interaction and regulates ADMSCs behavior by altering their cytoskeletal rearrangement and thereby increases the cellular spreading area and cell sheet formation. The synergistic effect of biochemical (honey) and biophysical (patterns) cues on ADMSCs studied by the nitro blue tetrazolium assay and DCFDA fluorescence spectroscopy reveals limited free radical generation within cells. Molecular expression studies show a decrease in p53 and p21 expressions validating ADMSCs senescence inhibition, which is further correlated with a decrease in cellular senescence-associated β galactosidase activity. We also show that an increase in CDH1 and CK19 molecular expressions along with an increase in SOX9, RUNX2, and PPARγ molecular expressions supported by PHSF2 justify the substrate's efficacy of underpinning mesenchymal to epithelial transition and multilineage trans-differentiation. This work highlights the fabrication of a naturally healing nutraceutical (honey)-embedded patterned porous stand-alone tool with the potential to be used as smart stem cells delivering regenerative healing implant.

Implantation of nanofibrous silk scaffolds seeded with bone marrow stromal cells promotes spinal cord regeneration (6686 words)

Spinal cord injury (SCI) is a common pathology often resulting in permanent loss of sensory, motor, and autonomic function. Numerous studies in which stem cells have been transplanted in biomaterial scaffolds into animals have demonstrated their considerable potential for recovery from SCI. In the present study, a three-dimensional porous silk fibroin (SF) scaffold with a mean pore size of approximately 383 μm and nanofibrous structure was fabricated, the silk scaffold enabling the enhanced attachment and proliferation of bone marrow stromal cells (BMSCs). Investigation of its therapeutic potential was conducted by implantation of the nanofibrous SF scaffold seeded with BMSCs into a transected spinal cord model. Recovery of the damaged spinal cord was significantly improved after 2 months, compared with a non-nanofibrous scaffold, in combination with decreased glial fibrillary acidic protein (GFAP) expression and improved axonal regeneration at the site of injury. Furthermore, elevated Basso-Beattie-Bresnahan (BBB) scores indicated greatly improved hindlimb movement. Together, these results demonstrate that transplantation of neural scaffolds consisting of nanofibrous SF and BMSCs is an attractive strategy for the promotion of functional recovery following SCI.

A study of the differentiation of stem cells from human exfoliated deciduous teeth on 3D silk fibroin scaffolds using static and dynamic culture paradigms.

Stem cells from human exfoliated deciduous teeth (SHED) are considered the best current source of human stem cells due to their ability to differentiate into multiple cell lineages. Dynamic co-culture systems can improve the culture environment, as they provide cells with signaling factors, extracellular matrixes, and cellular shear force, as well as enable the formation of heterotypic clusters. We seeded SHED in 3D silk fibroin porous scaffolds under static and dynamic cultures for 28days, using the NIH3T3 cultivated medium as an induction agent. Many hepatospheres formed in these porous scaffolds, and cellular viability was shown to continually increase by MTT assays. Hepatic AFP and ALB gene expression, as well as glycogen storage, albumin secretion, and urea synthesis, were greater in cells in the 3D porous scaffold under a dynamic culture than in those cultured under 3D static culture and petri dish conditions. However, the 3D static culture is still superior to the traditional petri dish culture. The NIH3T3 cultivated medium can significantly induce hepatic differentiation of SHED, while the 3D dynamic culture system significantly enhances hepatic differentiation of SHED. This study provides alternative sources of hepatocytes for liver disease treatment.

Nano-hydroxyapatite mineralized silk fibroin porous scaffold for tooth extraction site preservation

ObjectiveTo fabricate a novel nano-hydroxyapatite mineralized silk fibroin (MSF) scaffold in order to diminish the resorption of alveolar ridge and accelerate new bone formation within tooth sockets. Also, to investigate the biocompatibility and osteogenic ability of the MSF in vitro, and the effect of site preservation of the MSF graft in post-extractive sockets in vivo. MethodsSEM, EDX, FTIR and XRD were used to analyze the mineral crystals deposited on the silk fibroin (SF) surface. Pre-osteoblasts (MC3T3-E1) were seeded on SF and MSF scaffolds. Cell viability, distribution and differentiation were examined using a live-dead assay, histological analysis and Alizarin Red S staining. Furthermore, prepared grafts (SF or MSF scaffold) were implanted into the maxillary right first molar sockets of Sprague Dawley rats for 6 weeks and newly formed bone tissue was analyzed by micro-CT and histological examination. ResultsThe SEM, EDX, FTIR and XRD analysis demonstrated that granulate nano-hydroxyapatite (nHA) crystals were uniformly distributed on the SF scaffold. In addition, the MSF hydrophilicity measured by water contact angle and swelling ratio was superior to plain SF scaffold. The effect of nHA inorganic crystals on osteogenic differentiation of MC3T3-E1 cells indicated the MSF scaffolds improved osteogenesis. Furthermore, MSF grafts induced more bone formation and reduced the height of alveolar bone resorption after tooth extraction. SignificanceThe MSF scaffold partially simulated the structure and composition of natural bone matrix. It induced osteogenic differentiation of MC3T3-E1 cells in vitro, and also promoted new bone regeneration in tooth extraction sockets in vivo, indicating it is a biomaterial with great potential for tooth extraction site preservation.

Steady-State Behavior and Endothelialization of a Silk-Based Small-Caliber Scaffold In Vivo Transplantation.

A silk-based small-caliber tubular scaffold (SFTS), which is fabricated using a regenerated silk fibroin porous scaffold embedding a silk fabric core layer, has been proved to possess good cell compatibility and mechanical properties in vitro. In this study, the endothelialization ability and the steady-state blood flow of SFTSs were evaluated in vivo by implanting and replacing a common carotid artery in a rabbit. The results of the color doppler ultrasound and angiographies showed that the blood flow was circulated in the grafts without aneurysmal dilations or significant stenoses at any time point, and ran stronger and close to the autologous blood vessel from one month after implantation. The SFTSs presented an initial tridimensionality without being distorted or squashed. SEM and immunohistochemistry results showed that a clear and discontinuous endodermis appeared after one month of implantation; when implanted for three months, an endothelial layer fully covered the inner surface of SFTSs. RT-PCR results indicated that the gene expression level of CD31 in SFTSs was 45.8% and 75.3% by that of autologous blood vessels at 3 months and 12 months, respectively. The VEGF gene showed a high expression level that continued to increase after implantation.

Observation of co-culturing cells on porous silk fibroin films

Porous silk fibroin films (PSFFs) are widely used in skin regeneration. Prevascularization of PSFFs is a successful strategy for enhancing the survival of engineered tissues in vivo. The adhesion and migration of human umbilical vein endothelial cells (HUVECs) and fibroblasts on PSFFs were observed by scanning electron microscopy and confocal laser scanning microscopy after vital staining of the cells. PSFFs could attract a large number of HUVECs and fibroblasts to pores in an interesting alignment and support them to spread well from the outside of pores to the center of PSFFs to form cell layers. PSFFs showed minor structural changes due to less degradation for 12 d culture, and cell layers overlapped from pores to the center in PSFFs. The total DNA assay indicated excellent cell proliferation on PSFFs on days 1 and 6 and no difference between co-culturing HUVECs and mono-HUVECs and monofibroblasts. PSFFs could guide cell migration and arrangement to form pore-centered and vessel-like structures without additional coating of proteins. The authors’ aim was to study the potential prevascularization of porous silk fibroin scaffolds by co-culturing HUVECs and fibroblasts. This model has potential application for angiogenesis in dermis regeneration in the future and provides a suitable microenvironment for the development of capillary-like structures.

Development of Salt Leached Silk Fibroin Scaffold using Direct Dissolution Techniques for Cartilage Tissue Engineering

Autologous transplantations, the gold standard, did not meet sufficient health tissue coverage area for cartilage damage treatments. The field of tissue engineering offers a promising alternative to fulfill this limitation by growing patient own cells on biomaterials through tissue culture, reconstructed into new cartilage tissue, and the implanted to the injury area. To support tissue regeneration, biocompatible, biodegradable, and high strength silk fibroin (SF) was proposed in this study as scaffold materials. In this research, direct dissolution in CaCl2/formic acid, a faster and simpler process than traditional dissolution techniques, combined with salt leaching technique. SF contents on the scaffold were varied from 2 w/v% to 12 w/v% and NaCl size as porogen was fixed in diameter of 250±58 µm. Evaluation of the SF scaffold’s morphology, hydrophilicity, biodegradability, and biocompatibility were conducted. The results showed porous silk fibroin scaffold had been successfully developed. The SF scaffolds have pore size 261-293 µm with highly interconnected pores. FTIR and XRD analysis of the scaffolds showed the characteristics of silk fibroin, which reveals the α-helix amorphous and β-sheet crystalline structure and comparable to the silk fibers. The scaffold showed good hydrophilicity and high water uptakes, which essential properties for cell survival. The scaffold degraded under Protease XIV, indicate biodegradable properties. Observation of cell attachment confirms the scaffold has good biocompatibility to adipose-derived stem cells and are suitable to be used in cartilage tissue engineering.

Cell-seeded porous silk fibroin scaffolds promotes axonal regeneration and myelination in spinal cord injury rats

Accumulating evidence indicates that a suitable scaffold designed for the spinal cord injury (SCI) was needed to enhance the survival of transplanted Bone mesenchymal stem cells (BMSCs) and to promote nerve regeneration. The current study was aimed to evaluate the effect of the porous silk fibroin scaffold (PSFSs) seeded with BMSCS on nerve regeneration, myelination and functional recovery after SCI. We previously demonstrated that the PSFSs could bridge defected nerve with nerve fibers when applied to the transected spinal cord. And we found that BMSCs were adhered to the scaffold closely and have good biological compatibility with PSFSs. PSFSs seeded with BMSCs exhibited significant improvement in complete transverse thoracic SCI rat models. Flow cytometric assay also indicated that BMSCs grew well and adhered closely to the surface of the scaffold. The Basso-Beattie-Bresnehan (BBB) scores at each time point showed that the hindlimb motor function of each transplant group was also significantly restored. Meanwhile, growth associated protein 43 (GAP-43)marker of damaged axons regeneration and myelin basic protein (MBP) marker of maintaining the myelin structural and functional integrity, all markedly increased in PSFSs seeded with BMSCs models. Together, these results demonstrated that transplantation of PSFSs seeded with BMSCS could promote the nerve regeneration, myelination and functional recovery after SCI.

Fabrication, characterization, and in vitro evaluation of biomimetic silk fibroin porous scaffolds via supercritical CO2 technology

Scaffolds that mimic the nanofibrous structures of extracellular matrix (ECM) are essential for cell adhesion and proliferation in tissue engineering. In this study, silk fibroin (SF) scaffolds with interconnected porous and ECM-like nanofibrous structures were prepared by successfully combining supercritical CO2 technology with a porogen leaching process. The effects of pressure and concentration of the SF solution on the nanofibrous structures of the SF scaffolds were not significant. By manipulating the proportion of porogen, SF scaffolds with a porosity of (32.7 ± 1.7) % to (82.1 ± 2.3) % and a mechanical strength of (237.0 ± 2.2) kPa to (163.0 ± 6.5) kPa were fabricated. In vitro biocompatibility evaluation using a MTT assay, DAPI staining, and SEM observation indicated that the SF scaffolds exhibited no toxicity and could facilitate Schwann cell attachment and proliferation. Therefore, the biomimetic SF porous scaffolds with ECM-like nanofibrous structure have potential application in nerve regeneration.

Highly Porous Silk Fibroin Scaffold Packed in PEGDA/Sucrose Microneedles for Controllable Transdermal Drug Delivery.

Polymeric microneedles have attracted increasing attention as a minimally invasive platform for delivering drugs or vaccines in a more patient-friendly manner. However, traditional microfabrication techniques using negative molds with needle-shaped cavities usually require cumbersome centrifugation and vacuum degassing processes, which have restricted the scaled-up mass production of polymeric microneedles. Herein, a novel polydimethylsiloxane (PDMS)-based negative mold with cavities packed with silk fibroin scaffold is developed for rapid fabrication of polymeric microneedles, which comprise primarily the composition of poly(ethylene glycol) diacrylate (PEGDA) and sucrose as the needle matrix. Fibroin scaffolds can instantly adsorb prepolymer solution due to capillary force, and subsequently initiate the formation of microneedles via photoinduced polymerization. Based on three types of model drugs, including Rhodamine B (RhB), indocyanine green (ICG), and doxorubicin (DOX), the fabricated PEGDA/sucrose microneedles can realize effective transdermal delivery and controllable release of therapeutic molecules by regulating the sucrose content. The presented method provides a simple strategy for quick fabrication of polymeric microneedles toward transdermal drug delivery applications.