Elsevier

Polymer

Volume 50, Issue 1, 2 January 2009, Pages 279-285
Polymer

Studies of electrospun regenerated SF/TSF nanofibers

https://doi.org/10.1016/j.polymer.2008.10.053Get rights and content

Abstract

The Bombyx mori silk fibroin/Tussah silk fibroin (SF/TSF) nanofibers with diameters between 300 and 3500 nm were prepared by electrospinning with the solvent HFIP. The average diameters of SF/TSF blend fibers increased from 404 to 1977 nm, with the increase of SF content in blend solutions, and the relationship between the average diameters of SF/TSF and SF content was proved to be linear correlation. Results from FTIR, TG-DTA and X-ray diffraction showed that the electrospun fibers were mainly β-sheet structure and, heterogeneous micro-structures. In particular, the presence of two different endothermic peaks at 300 and 360 °C in the TG-DTA curves may be ascribed to the thermal decomposition of SF and TSF. These results suggested that SF and TSF were still immiscible even dissolved in hexafluoroisopropanol (HFIP) after electrospinning and ethanol treatment. Moreover, the thermal decomposition temperature and enthalpy were improved with the blend of SF and TSF, else the SF/TSF nanofibers' moisture absorption was higher than the pure SF or TSF nanofibers. To study the cytocompatibility and cell behavior on the SF/TSF nanofibers, MSCs, VECs, and Neurons were seeded onto the nanofibers. Results indicated that the SF/TSF nanofibers promote cell attachment and spreading, suggesting that these nanofibers could be a candidate scaffold for blood vessel and nerve injury recovery.

Introduction

Recently, much attention has been paid to electrospinning, a very effective way to prepare nanofibers [1]. Electrospinning can be used to process many kinds of materials, like polymers, composite, ceramic materials, cellulose acetate [2], [3], and so on. Bombyx mori silk, Sussah silk, Samia cynthia, recombinant hybrid silk all have been electrospun to nanofibers which are probably used in biomaterials [4], [5], [6].

B. mori silk has been used for medical suture for a long time [7]. SF (silk fibroin) is a valuable candidate materials for biomedical applications for its distinctive biomedical properties including good biocompatibility, blood compatibility, good oxygen and water permeability, biodegradability, non-cytotoxicity and minimal inflammatory reaction [8]. Tussah silk is one of the wild silks, and its chemical structure, molecular conformation and physical properties have been extensively studied [9]. In contrast to domestic silk, its amino acid composition is characterized by more Ala, Asp and Arg contents and, less Gly. Moreover, it is well known that the presence of the Arg-Gly-Asp (RGD) tripeptide sequence may act as a biological recognition signal, promoting cell adhesion and, consequently, make this protein suitable for biomedical application [10].

The aim of this study was to prepare SF/TSF blend nanofibers by electrospinning of their solution and, to characterize the micro-structure properties of these nanofibers by SEM, FTIR, X-ray diffraction, and TG-DTG analyses. Furthermore, in order to evaluate the cytocompatibility and cell behavior on the SF/TSF nanofibers, MSCs, VECs, and NSCs were seeded onto the nanofibers.

Section snippets

Solution preparation

B. mori silk fibroin film and Tussah silk fibroin (TSF) film were made as per our previous report [11], [12]. The 10% concentration spinning solutions with the SF/TSF ratios of 0/100, 20/80, 40/60, 50/50, 60/40, 80/20, 100/0 were prepared by dissolving SF film and TSF film in HFIP, and oscillating in 25 °C water bath for one week.

Electrospinning and post-treatment

The electrospinning setup used in this study consisted of a syringe and needle (0.9 mm OD × 0.5 mm ID), a rectangular (20 × 10 cm) aluminum foil collecting plate, a high

Morphological characteristics

Fig. 1 shows SEM micrographs and diameters' distribution of SF/TSF nanofibers. The ribbon-like as-spun nanofibers had a smooth surface and round cross section. Due to the incomplete solvent evaporation and jet split, fibers' adhesion and bifurcation were observed.

As shown in Fig. 1, the diameters of SF/TSF blend nanofibers were between 300 and 3500 nm, the average diameters increased from 404 to 1977 nm with the increase of SF content in blend compositions, and the diameter of five groups with

Conclusions

In this study, the SF and TSF dissolved in HFIP were electrospun into nanofibers with the blend ratios of 100/0, 80/20, 60/40, 50/50, 40/60, 20/80, 0/100. A linear correlation was found between the average diameters and SF or TSF content. The estimated structure and physical properties of electrospun SF/TSF blend nanofibers suggest that the two fibrous proteins have low degree of compatibility after electrospinning. After 75% ethanol treatment, random coil, α-helix and β-sheet co-exist in the

Acknowledgement

The present work is supported financially by the Natural Science Foundation of Jiangsu (No. BK2007054) and Sponsored by National Base Research Program of China (973 program) (2005CB623906).

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