Department of Biomedical Engineering, Tufts University, 4 Colby St., Medford, 02155, MA, USA.
Macromol Biosci. 2014 Feb;14(2):257-69. doi: 10.1002/mabi.201300321. Epub 2013 Nov 8.
The effect of some sterilization methods (autoclaving and ethanol treatments) on the degradation rate and mechanical properties of two types of porous silk scaffolds (aqueous- and hexafluoroisopropanol-derived) is evaluated. Changes in secondary structure, crystal size, and supramolecular features of silk fibroin, resulting from sterilization, are tracked to elucidate molecular level effects on protease XIV enzymatic degradation and compressive mechanical properties. The structural features and pore sizes of the silk scaffolds remain intact after both sterilization processes. Autoclave sterilization dramatically reduce the degradation rate of the silk scaffolds in response to protease XIV and significantly increase mechanical properties, in contrast to scaffolds sterilized with 70% ethanol. Higher β-sheet content and larger crystal size are observed after autoclaving, unlike in response to 70% ethanol sterilization, based on examination of Fourier transform (FT) IR spectroscopy and wide-angle X-ray scattering (WAXS). In addition, thermal analysis finds supramolecular features within silk fibroin amorphous regions, including the glass transition temperature (Tg ), heat capacity of glass transition (ΔCp-Tg ), and thermal gravimetric degradability. Such supramolecular level changes are related to the shift in enzymatic degradation and mechanical properties due to autoclaving versus treatment with 70% EtOH. The changes in supramolecular organization in amorphous regions can retard enzyme diffusion through the glassy regions of the silk matrix or/and hinder binding of enzymes, while also stiffening these matrices.
评估了几种灭菌方法（高压蒸汽灭菌和乙醇处理）对两种多孔丝支架（水相和六氟异丙醇衍生）的降解速率和力学性能的影响。跟踪丝素蛋白的二级结构、晶体尺寸和超分子特征的变化，以阐明灭菌对蛋白酶 XIV 酶降解和压缩力学性能的分子水平影响。两种灭菌过程后，丝支架的结构特征和孔径均保持完整。与用 70%乙醇灭菌的支架相比，高压蒸汽灭菌可显著降低蛋白酶 XIV 对丝支架的降解速率，并显著提高机械性能。与 70%乙醇灭菌相反，高压蒸汽灭菌后观察到更高的β-折叠含量和更大的晶体尺寸，这是基于傅里叶变换（FT）红外光谱和广角 X 射线散射（WAXS）的检查。此外，热分析发现丝素蛋白无定形区域内的超分子特征，包括玻璃化转变温度（Tg）、玻璃化转变热容量（ΔCp-Tg）和热重降解性。由于高压蒸汽灭菌与用 70%乙醇处理相比，这种超分子水平的变化与酶降解和机械性能的变化有关。无定形区域中超分子组织的变化可以阻碍酶在丝基质的玻璃区域中的扩散，或者/和阻碍酶的结合，同时也使这些基质变硬。
