Natural Silk Nanofibril Aggregates Featuring Diverse Architectures as Templates for Hydroxyapatite Biomineralization

Abstract

Living organisms have developed a miraculous biomineralization strategy to form multistage organic-inorganic composites through the orderly assembly of hard/soft substances, achieving the functions of tissues and organs. Natural silk fibroin nanofibers (SNF) have recently attracted great attention in the field of biomaterials due to their excellent biocompatibility and biomimetic nanostructures. In this paper, we utilized SNFs aggregates as templates for hydroxyapatite (HAp) biomineralization and investigated the mineralization processes of SNFs materials with various architectures, including single SNF, two-dimensional (2D) SNFs membranes, and three-dimensional (3D) SNFs scaffolds with different morphologies. During the mineralization process, amorphous HAp (ACP) is initially mineralized on one-dimensional SNFs and then transformed into stable HAp crystals, which differs from the mineralization process on the 2D nanofiber membrane where no amorphous structure is formed at the early stage. More HAp can be formed on 3D scaffolds with nanofiber network structures than on porous wall scaffolds, depending on the specific surface area for fiber mineralization in the scaffold. Generally, the mineralization of these three materials enhances the mechanical properties and biocompatibility of nanofiber materials, providing a novel idea for the design of biomimetic hard tissue engineering scaffolds.

Keywords: Silk fibroin nanofibers, Hyaluronic acid, Biomineralization, Hydroxyapatite