Bioactive composite scaffolds of carboxymethyl chitosan-silk fibroin containing chitosan nanoparticles for sustained release of ascorbic acid

Abstract

This study introduces and characterizes the biomimetic and bioactive scaffolds for bone regeneration based on silk fibroin (SF)-carboxymethyl chitosan (CMCh) incorporated with ascorbic acid (AA)-loaded chitosan nanoparticles (ChNPs). The ChNPs were prepared to encapsulate AA, as a simple and safe osteoinductive drug, through the ionic gelation process. CMCh was also prepared through chemical reaction with monochloroacetic acid under various temperature conditions (60–80 °C). The CMCh with higher carboxyl content (T = 80 °C) was chosen for further scaffolding. Then, the AA-loaded ChNPs were mixed with different ratios of SF: CMCh to prepare osteoconductive and osteoinductive scaffolds. As proved by scanning electron microscopy, all composites had well-interconnected porous structures. Larger pore size, higher porosity, and greater water uptake were obtained by increasing CMCh, while the opposite trend was observed for compressive modulus and strength. The in vitro release studies showed that the release of AA was controlled by Fickian diffusion and was faster in the scaffolds containing more CMCh. The mineralization study in simulated body fluid indicated that both CMCh and AA promote calcium phosphate deposition throughout all scaffolds, while the bioactivity enhanced with the increase of CMCh. Osteoblast-like cells (MG63) cultured on the scaffolds demonstrated that higher CMCh content enhanced cell spreading, proliferation, and alkaline phosphatase activity.