Advanced Materials Research Vols. 175-176

Abstract: For exploiting the novel multifunctional ecological cotton fibers, a new cotton fiber with the collagen protein cross-linking (CPCCF) was prepared by the limited selective oxidation of a cotton thread with sodium periodate solution and subsequent treatment with a solution of collagen protein at 40°C in aqueous acetic acid. FT-IR spectra of the CPCCF suggested that the imine covalent bond between the collagen protein and the oxidized cotton fiber was formed through a series of reaction. X-ray diffractograms analysis showed that the crystallinity of oxidized cotton fiber after collagen protein treatment increased slightly. Meanwhile, Scanning electron microscopy photographs illuminated that the modification with collagen protein occurred on the surface of cotton fiber. Kjeldahl nitrogen analysis of the CPCCF showed that the maximum percentage of collagen protein introduced into cotton fiber was 1.68% (w/w). However, the breaking strength of the cotton thread oxidized partially by sodium periodate at the concentration of less than 2.0 mg ml-1 did not decrease much. Furthermore, a model experiment for the controlled release drugs was performed using aloe anthraquinone, components of a Chinese medicine, suggested potential usefulness of the CPCCF as a carrier for the controlled release drugs.

Abstract: Schwann cells (SCs) are primary structural and functional cells in peripheral nervous system and play a crucial role in peripheral nerve regeneration. Current challenge in peripheral nerve tissue engineering is to produce an implantable scaffold capable of bridging long nerve gaps and assist Scs in directing the growth of regenerating axons in nerve injury recovery. Electrospun silk fibroin nanofibers, fabricated for the cell culture in vitro, can provide such experiment support. Silk fibroin scaffolds (SFS) were fabricated with formic acid (FA), and the average fiber diameter was 305 ± 24 nm. The data from microscopic, immunohistochemical and scanning electron micrograph confirmed that the scaffold was beneficial to the adherence, proliferation and migration of SCs without exerting any significant cytotoxic effects on their phenotype. Thus, providing an experimental foundation accelerated the formation of bands of Bünger to enhance nerve regeneration. 305 nm SFS could be a candidate material for nerve tissue engineering.

Abstract: Objective: Evaluate the biocompatibility of olfactory ensheathing cells (OECs) on the electrospun low-diameter silk fibroin scaffold (LD-SFS). Methods: 400 nm silk fibroin nanofibers were prepared by electrospinning technique and were observed by scanning electron microscope (SEM). The OECs were isolated and purified by the modified differential adherent velocity method. Then, the purified OECs were seed on the poly-L-lysine and electrospun silk fibroin scaffold. The nerve growth factor receptor (NGFR) p75 and glial fibrillary acidic protein (GFAP) were used to identify OECs by immunofluorescence staining. The MTT and flow cytometric assay were used to detect the proliferation and apoptosis effect of OECs on the different scaffolds. Results: The SEM showed that the average diameter of the fibers was about 400 nm and the nanofibers constituted a three-dimensional structure with porous network and smooth surface. The morphology of OECs on the LD-SFS group was similar to that on the poly-L-lysine (PLL) group. In addition, MTT and flow cytometric assay also showed that there was no significant difference between the two scaffolds in the proliferation and apoptosis activity. Conclusion: LD-SFS may serve as an ideal tissue engineering scaffold for the olfactory ensheathing cells.

Abstract: Objective: To evaluate the growth of olfactory ensheathing cells (OECs) on the silk fibroin (SF) nanofibers scaffold. Methods: The purified OECs were cultured with poly-L-lysine (control group) and 1200 nm SF nanofibers (experimental group). The morphological features and growth characteristics of which were analyzed by phase contrast microscopy. Nerve growth factor receptor (NGFR) p75 were applied to identify OECs by immunostaining. SEM was used to observe the adherence and spreading of OECs on different substrates. MTT assay was performed to evaluate the proliferation activity of OECs both on the control and experimental scaffolds. Results: The isolated OECs reached confluence after 4-5 days of culture, which were stained for antibody NGFRp75(+). The morphology of OECs on the 1200 nm SF nanofibers was similar to that on the control group. The SEM clearly revealed the close interaction between the OECs and the nanofbers. The OECs on SF nanofibers still maintain its original characteristic phenotypes. The MTT showed that the most obvious proliferation was reached over 10 days. The differences of OD values between 1200 nm SF and PLL were significant at day 5, 7 (p < 0.05). However, there was no significant difference at day 10. Conclusion: SF nanofibers scaffold could support the growth of OECs, and may be a promising tissue-engineered scaffold for the repair of SCI.

Abstract: regeneration silk fibroin particles prepared through the dissolving-regeneration route do not fulfill many desired requirements for bio-related applications, due to their partial solubility in water. So, Native silk fibroin powder (NSFP) was prepared by mechanical method to instead of regeneration silk fibroin particles. The goal of this paper is to evaluate the inflammatory response of polyurethane/NSFP composite membrane containing aspirin implanted in mice. The polyurethane/NSFP composite membranes containing aspirin were fabricated by coagulation technique at 30°C. The composite membranes were embedded in mice for 1 weeks and inflammatory response of composite membranes in mice was studied. Inflammatory cells accumulation occurred around implanted polyurethane/NSFP composite membrane, but was reduced significantly in composite membrane containing aspirin. The results indicated that the aspirin released from composite membrane of polyurethane and NSFP could suppress the replication of inflammatory cells and prevent the entering of cells into composite membrane.

Abstract: In this paper, the electrospinning of regenerated cellulose acetate (short as CA), acetone as the solvent, was basically studied, and the electrospinning setup used was self-designed. In order to explore the present condition of electrospun cellulose acetate nanofibers, the effect of traditional processing parameters on the cellulose acetate nanofibers was paid a lot of attention to, the influence of solution concentration especially, spinning voltage, the distance from spinneret to collecting screen on the morphology and the structure of the electrospun fibers. With a scanning electron microscope, the structures of the mats and the fibers were characterized and compared to the original acetate cellulose using an infrared spectrometer. It was concluded that the optimal processing parameters in the electrospinning were 8 wt%, 18 kV and 15 cm, respectively. Comparing the inner structure of the original CA and the electrospun fibers, the number of –OH groups changed apparently, this was mainly due to the dissolution.

Abstract: In electrospinning, non-woven fabrics are commonly used as substrates to receive polymer nanofibers. Nanofiber mats formed in this process have many advantages, such as extensive application prospects in the thermal insulation, filtration, protection and so on. Polyvinyl alcohol (PVA) is the main electrospun material with excellent physical properties, biodegradable properties, chemical resistance, and good mechanical properties in the dry state. However, PVA has a poor water resistance which limits its application. In this study, The PVA nanofibrous mats prepared by electrospinning were chemically crosslinked with glutaraldehyde (GA) in acetone. Scanning Electron Micrograph (SEM) and Fourier Transform Infrared (FTIR) spectrometry were employed to characterize the morphology and structure of crosslinked PVA nanofiber mat and PVA nanofiber mat. The differences of morphology and structure between the modified and nonmodified nanofiber mat were revealed. Such nanofibrous mat has good water resistance and excellent warmth retention property. Thus, the practical applications of PVA nanofiber mats were broadened.

Abstract: Bone Morphogenetic Protein 2 (BMP-2) is a member of the transforming growth factor superfamily. It plays an important role in stimulating osteoblast differentiation and bone formation, and has been widely utilized in clinical bone repairing by implantation. In this study, the nano-hydroxyapatite (nHA)/silk fibroin (SF) porous scaffolds were fabricated for the sustained delivery of recombinant human bone morphogenetic protein-2 (rhBMP-2), and then used to address the hypothesis that rhBMP-2 delivered from the scaffolds could enhance the bone formation in vitro. We optimized an effective method using a prokaryotic expression system to produce rhBMP-2. The rhBMP-2 was expressed, purified and renatured in vitro. And then the rhBMP-2 was loaded onto the nHA/SF scaffolds. The bioactivities of rhBMP-2-loaded nHA/SF scaffolds were assessed in vitro. The results showed that the rhBMP-2 promoted the osteoblasts adhesion and proliferation on the nHA/SF scaffolds. Also, the rhBMP-2 released from the nHA/SF scaffold stimulated a significant increase in alkaline phosphatase (ALP) activity of osteoblasts in vitro. These results demonstrated that the rhBMP-2-loaded nHA/SF scaffolds could promote the bone regeneration and showed potential applications in the bone tissue engineering.

Abstract: Using genetic engineering methods, we attempted to produce novel silk-like proteins with new function by combining several functional sequences selected from fibroin of Bombyx mori (B.mori), Samia Cynthia ricini (S.c.ricini) and spider silks or by inducing cell adhesive sequence or calcium binding sequence into silk proteins. The secondary structure of these silk-like proteins was characterized with solid state NMR. Cell adhesion assay indicated that silk-like proteins have higher cell activity. Mineralization of fibroin protein was improved with induction of calcium binding sequence. Nanofiber formation of silk-like proteins was achieved using electrospinning. Fiber was formed from silk-like proteins. These silk-like proteins might be candidates to meet requirement in the field of biomaterials.

Abstract: The native silk fibroin fiber from Bombyx mori has been used as suture with non-degradable character. Therefore, preparing biodegradable silk fibroin fiber is very attractive and important. In this paper, the biodegradable silk fibroin fiber with high strength was prepared according to the process of regenerated silk fibroin fiber from the 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solution and by adding calcium chloride CaCl2 to the silk fibroin solution. The degradation rate of the regenerated silk fibroin fibers was dependent on calcium chloride concentration.