Nanoscale control of silks for nanofibrous scaffold formation with an improved porous structure

Abstract

Silk-based porous scaffolds have been used extensively in tissue engineering because of their excellent biocompatibility, tunable biodegradability and robust mechanical properties. Although many silk-based scaffolds have been prepared through freeze-drying, a challenge remains to effectively control porous structures during this process. In the present study silk fibroin with different nanostructures were self-assembled in aqueous solution by repeated drying-dissolving process and then used to improve porous structure formation in lyophilization process. Viscosity, secondary structures and water interactions were also studied to exclude their influence on the formation and control of porous structures. Following nanofiber formation in aqueous solution, silk scaffolds with improved porous structure were directly formed after lyophilization and then stabilized with water or methanol annealing treatments. Compared to silk scaffolds derived from fresh solution, the nanofibrous scaffolds showed significantly better cell compatibility in vitro. Therefore, this nanoscale control of silk offers feasible way to regulate the matrix features including porous structure and nanostructure, which are important in regulating cell and tissue outcomes in tissue engineering and regeneration, and then achieve silk-based scaffolds with improved properties.

A mild process to design silk scaffolds with reduced β-sheet structure and various topographies at the nanometer scale

“…Recently, nanofibrous silk scaffold with 3-D porous structure and better biocompatibility was successfully prepared by a modified lyophilization method in our laboratory [34,35]. Silk nanofiber solution was firstly prepared via a slowly increasing concentration process [36,37].…”

“…Silk nanofiber solution was firstly prepared via a slowly increasing concentration process [36,37]. Then, scaffolds with porous structure instead of separate lamellar sheets were directly derived from the nanofiber solution after freeze-drying process [34]. However, methanol or water annealing treatments were required to achieve water insolubility, in which methanol was harmful for environment while water annealing partly sacrificed the porous structure [36].…”

A novel method to prepare tussah/Bombyx mori silk fibroin-based films

“…Different with BSF lm, the TSF lm showed layer structure as previous reports. 24,25 The specic nanostructure of BSF existed, and the layer structure of TSF disappeared in the blend lms. Furthermore, the morphological phase separation was not observed, which had been reported in the BSF/TSF, 26 and in the TSF/carboxymethyl chitosan blend lms prepared using water as a co-solvent.…”

Simulation of ECM with silk and chitosan nanocomposite materials

“…The DSC peaks of SF strongly depend on the measurement conditions such as the heating rate. 61 Based on previous studies under similar measurement conditions, 55,62 the degradation peak at 250–260 °C belongs to a random/silk I structure whereas the peaks at 260–280 °C are the beta-sheet formation. 63 The increase in temperature of the degradation peaks suggests a higher beta-sheet content.…”

“…63 The increase in temperature of the degradation peaks suggests a higher beta-sheet content. 62,63 Figure 2A illustrates the standard DSC curves for pure CS and SF scaffolds. Besides the water evaporation peaks at 50–100 °C, the CS scaffolds showed a significant nonisothermal crystallization peak at 247 °C whereas the SF scaffolds showed a nonisothermal crystallization peak at 214 °C and a degradation peak at 265 °C.…”