Linpeng Fan

Genipin-crosslinked silk fibroin/hydroxybutyl chitosan nanofibrous scaffolds for tissue-engineering application

To improve water-resistant ability and mechanical properties of silk fibroin (SF)/hydroxybutyl chitosan (HBC) nanofibrous scaffolds for tissue-engineering applications, genipin, glutaraldehyde (GTA), and ethanol were used to crosslink electrospun nanofibers, respectively. The mechanical properties of nanofibrous scaffolds were obviously improved after 24 h of crosslinking with genipin and were superior to those crosslinked with GTA and ethanol for 24 h. SEM indicated that crosslinked nanofibers with genipin and GTA vapor had good water-resistant ability. Characterization of the microstructure (porosity and pore structure) demonstrated crosslinked nanofibrous scaffolds with genipin and GTA vapor had lager porosities and mean diameters than those with ethanol. Characterization of FTIR-ATR and (13)C NMR clarified both genipin and GTA acted as crosslinking agents for SF and HBC. Furthermore, genipin could induce SF conformation from random coil or α-helix to β-sheet. Although GTA could also successfully crosslink SF/HBC nanofibrous scaffolds, in long run, genipin maybe a better method due to lower cytotoxicity than GTA. Cell viability studies and wound-healing test in rats clarified that the genipin-crosslinked SF/HBC nanofibrous scaffolds had a good biocompatibility both in vitro and in vivo. These results suggested that genipin-crosslinked SF/HBC nanofibrous scaffolds might be potential candidates for wound dressing and tissue-engineering scaffolds.

Vitamin E-loaded silk fibroin nanofibrous mats fabricated by green process for skin care application

In the present study, we reported fabrication and skin benefit of a novel vitamin E (VE)-loaded silk fibroin (SF) nanofibrous mats. RRR-α-Tocopherol polyethylene glycol 1000 succinate (VE TPGS), a water-soluble derivative of VE, was incorporated into SF nanofiber successfully by aqua solution electrospinning for the first time. Morphology of the composite nanofibers changed with the different amount of VE TPGS: a ribbon-like shape for lower loading dose of VE TPGS, while a round shape for higher loading dose (more than 4% (wt/wt) based on the weight of SF). After treated with 75% (v/v) ethanol vapor, the composite nanofibrous mats showed an excellent water-resistant ability. In vitro study disclosed a sustained release behavior of VE TPGS disassociated from the nanofibrous mats. The mouse skin fibroblasts (L929 cells) cultured on the VE-loaded SF nanofibrous mats spread and proliferated much better than on cover slips. Moreover, the incorporation of VE TPGS was found strengthening the ability of SF nanofibrous mats on protecting the cells against oxidation stress induced by tert-butyl hydroperoxide. Our data presented impressive skin benefits of this VE-loaded SF nanofibrous mats, suggesting a promising applicative potential of this novel product on personal skin care, tissue regeneration and other related area.

Hierarchically designed injectable hydrogel from oxidized dextran, amino gelatin and 4-arm poly(ethylene glycol)-acrylate for tissue engineering application

Hydrogels are high in water content and have physical properties similar to native extracellular matrix (ECM), and thus they have been widely studied as three-dimensional (3D) tissue engineering scaffolds for cell culture. In this work, a two-step process was introduced to fabricate injectable hydrogel from oxidized dextran (ODex), amino gelatin (MGel) and 4-arm poly(ethylene glycol)-acrylate (4A-PEG-Acr) for cell encapsulation. A primary network was formed based on a Schiff based reaction between ODex and MGel, then a UV light-induced radical reaction of 4A-PEG-Acr was used to produce the independent secondary network. Both of the reactions were carried out under physiological conditions in the presence of living cells with no toxicity. The primary network depending on natural polymers could degrade rapidly to provide space and nutrition for encapsulated cells’ growth, and the secondary network could provide long-term mechanical stability. The attachment and spreading of pre-osteoblasts (MC3T3-E1) on IPN hydrogels were observed by DEAD/LIVE kit staining. Furthermore, cell spreading and cell proliferation within IPN hydrogels were observed using confocal microscopy after phalloidin/DAPI staining. The results showed that the as-prepared interpenetrating polymer network (IPN) hydrogels possessed good mechanical properties, a controllable degradation rate and favorable biocompatibility. Therefore, the hierarchically designed hydrogel in this study could be a promising candidate for bone or cartilage tissue engineering applications.

Vitamin C-reinforcing silk fibroin nanofibrous matrices for skin care application

In this work, we reported on the preparation and skin benefits of L-ascorbic acid 2-phosphate (VC-2-p)-loaded silk fibroin (SF) nanofibrous matrices for the first time. The matrices was fabricated using a facile eco-friendly electrospinning processing. With a post treatment of 75 v/v% ethanol vapor, the structure of the matrices transformed from unstable silk I form into water-stable silk II. In vitro release studies confirmed VC-2-p disassociated from SF nanofibrous matrices easily. Both neat and VC-2-p-loaded SF nanofibrous matrices were beneficial to mouse fibroblast L929 cells (L929 cells) adhering, spreading and proliferating against cover slips. Whereas compared with neat SF nanofibrous matrices, VC-2-p-loaded SF nanofibrous matrices significantly promoted the expression of collagen type I alpha 1 (Col1a1), as evidenced by real time PCR. Subsequently, the oxidative injury model further verified both matrices aided L929 cells through antioxidation to survive from tert-butyl hydroperoxide-induced oxidative stress (OS). Importantly, under severe OS, L929 cells on VC-2-p-loaded SF nanofibrous matrices maintained a higher mRNA level of Col1a1 as well as another two important functional genes, glutathione peroxidase 1 and catalase, than neat SF nanofibrous matrices. Our findings clearly indicated that the impressive skin benefits of SF nanofibrous matrices were further reinforced with the incorporation of VC-2-p, which implies the promising application of VC-2-p-loaded SF nanofibrous matrices in personal skin care and skin regeneration, including serving as wound dressings and anti-aging materials.

Electrospun Silk Fibroin–Hydroxybutyl Chitosan Nanofibrous Scaffolds to Biomimic Extracellular Matrix

Silk fibroin (SF)–hydroxybutyl chitosan (HBC) blend nanofibrous scaffolds were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM by electrospinning. SEM results showed that the average nanofibrous diameter increased when the content of HBC was raised from 20% to 100%. Whereas water contact angle measurements confirmed that SF/HBC nanofibrous scaffolds with different weight ratios were of good hydrophilicity. Both the tensile strength and the elongation at break were improved obviously when the weight ratio of SF to HBC was 20:80. 13C-NMR clarified that SF and HBC molecules existed in H-bond interactions, but HBC did not induce SF conformation to transform from random coil form to β-sheet structure. Moreover, the use of genipin vapour not only induced conformation of SF to convert from random coil to β-sheet structure but also acted as a cross-linking agent for SF and HBC. Cell viability studies demonstrated that SF/HBC nanofibrous scaffolds presented good cellular compatibility. Thus, electrospun SF/HBC blended nanofibres may provide an ideal biomimic tissue-engineering scaffold.

Regenerated Silk Fibroin Nanofibrous Matrices Treated with 75% Ethanol Vapor for Tissue-Engineering Applications

As an excellent biocompatible and biodegradable protein polymer, silk fibroin (SF) has found wide applications, particularly serving as therapeutic agent for tissue-engineering applications, on which both post-spin treatment and sterilization processing are crucial to drug-loaded matrices. To find a safe, effective and appropriate post-spin treatment and sterilization approach for drug-loaded biomaterial matrices is one of the major problems in the field of tissue engineering at present. In this work, a simple, safe and effective approach skillfully integrating post-spin treatment with sterilization processing was developed to drug-loaded SF nanofibrous matrices. Electrospun SF nanofibrous matrices from its aqueous solution were post-treated with 75% ethanol vapor. 13C-NMR and WAXD analysis demonstrated that such post-spin treatment rendered the structure of SF nanofibrous matrices transform from the silk I form to the silk II form. Furthermore, biological assays suggested that as-treated SF nanofibrous matrices significantly promoted the development of murine connective tissue fibroblasts. Skillfully integrated with novel sterilization processing, 75% ethanol vapor treatment could be a potential approach to designing and fabricating diverse drug-loaded SF nanofibrous matrices serving as therapeutic agents for tissue-engineering applications in that it can effectively protect the drug from losing compared with traditional post-spin treatment and sterilization processing.

Electrospun Biomimic Nanofibrous Scaffolds of Silk Fibroin/Hyaluronic Acid for Tissue Engineering

Abstract This study aimed to fabricate nanofibrous scaffolds which could biomimic the natural extracellular matrix from aqueous solutions of silk fibroin and hyaluronic acid blends (SF/HA) by means of electrospinning. Scanning electronic microscopy results indicated that electrospun SF/HA nanofibers were ribbon-shaped and their average width obviously decreased with the increase of HA content. However, there is no fiber observed when the volume of HA further increased to 50% of overall volume. After being treated with 75% ethanol vapor for 24 h, the fibers still remained their fibrous morphologies and presented good capability of water-resistance. Fourier transform infrared attenuated total reflectance spectroscopy, 13C-CP-MAS nuclear magnetic resonance and differential scanning calorimetry results revealed that HA did not induce SF conformation from random coil to β-sheet. SF conformation converted from random coil to β-sheet after being treated with 75% ethanol vapor. Cell viability studies demonstrated that SF/HA nanofibrous scaffolds significantly promoted cell proliferation. Electrospun SF/HA nanofibers may provide an ideal biomimic tissue-engineering scaffold or vehicle for water-soluble drugs.

Crosslinking of poly(L-lactide) nanofibers with triallyl isocyanutrate by gamma-irradiation for tissue engineering application.

The radiation crosslinked poly(L-lactide) (PLLA) electrospun nanofibers have been developed with improved thermal stability and mechanical properties. Trially isocyanurate (TAIC) were added into PLLA solution at different weight ratios (1, 3, and 5%) and electrospun into nanofibrous mats, the mats were then irradiated by gamma ray at different radiation doses (5, 10, and 25 kGy) to crosslink the PLLA chains. Their surface morphology, thermal properties, mechanical properties, and biodegradation properties were investigated and compared before and after gamma irradiation. Furthermore, the in vitro biocompatibilities were also evaluated by using mouse L929 fibroblasts. The results indicated that the efficient crosslinking networks can be generated when the TAIC content is higher than 3%. The thermal stability and tensile mechanical properties were significantly increased at higher irradiation dose of 10 and 25 kGy. However, radiation dose at 25 kGy have an adverse effect on the thermal stability of crosslinked samples due to thermal degradation induced by irradiation, the crosslinked samples irradiated at 10 kGy exhibited the best enzymatic degradation. The in vitro results also revealed that the crosslinked PLLA/TAIC composite nanofibers did not induce cytotoxic effects and are suitable for cell growth. Therefore, the crosslinked PLLA nanofibers are one of the promising materials for future tissue engineering applications.

Green electrospun grape seed extract-loaded silk fibroin nanofibrous mats with excellent cytocompatibility and antioxidant effect.

Silk fibroin (SF) from Bombyx mori has an excellent biocompatibility and thus be widely applied in the biomedical field. Recently, various SF-based composite nanofibers have been developed for more demanding applications. Additionally, grape seed extract (GSE) has been demonstrated to be powerful on antioxidation. In the present study, we dedicate to fabricate a GSE-loaded SF/polyethylene oxide (PEO) composite nanofiber by green electrospinning. Our results indicated the successful loading of GSE into the SF/PEO composite nanofibers. The introduction of GSE did not affect the morphology of the SF/PEO nanofibers and GSE can be released from the nanofibers with a sustained manner. Furthermore, comparing with the raw SF/PEO nanofibrous mats, the GSE-loaded SF/PEO nanofibrous mats significantly enhanced the proliferation of the skin fibroblasts and also protected them against the damage from tert-butyl hydroperoxide-induced oxidative stress. All these findings suggest a promising potential of this novel GSE-loaded SF/PEO composite nanofibrous mats applied in skin care, tissue regeneration and wound healing.

A Novel Skin-Care Product Based on Silk Fibroin Fabricated by Electrospinning

A novel Vitamin C (VC) loaded silk fibroin (SF) nanofibers was fabricated by electrospinning with blend aqueous solution of the materials. The morphology of electrospun VC loaded SF (VC/SF) nanofibers was observed by scanning electronic microscope (SEM) and the compositions of the composite nanofibers were inspected by X-ray photoelectron spectroscopy (XPS). The nanofibrous membrane was post-treated by methanol vapor, which rendered the nanofibers a good water-insoluble characterization. After soaked into phosphate buffered saline (PBS) for 4 days, the water-insoluble nanofibers have swelled due to the absorbing of water. The electrospun SF nanofiber membrane could be a more effective vehicle to delivery the VC into skin tissue and this novel product of VC/SF composite nanofiber is expected to have a good prospect of application on skin care, wound dressing and skin tissue engineering.