Gallic acid-grafted hybrid strontium fluoride/polycaprolactone nanocomposite fibers for bone regeneration

Abstract

This study aimed to develop a new bioactive scaffold by combining the structural characteristics of polycaprolactone (PCL) nanofibers with the therapeutic properties of gallic acid (GA) and strontium fluoride (SrF2) nanoparticles (NPs). Thus, SrF2 NPs were first synthesized and then incorporated into PCL nanofibers in different amounts (0, 5, 10, and 15 wt%). The resultant nanofibrous mats were then aminolized to immobilize GA via carbodiimide chemistry. As demonstrated by FTIR, GA is successfully immobilized on PCL nanofibers. The crystallinity of PCL nanofiber declined with a lower SrF2 amount but improved when the SrF2 amount increased to 15 wt%. The addition of SrF2 decreases the diameter of the fibers while enhancing their water absorption and tensile strength. The bioactivity results indicated that GA promotes apatite formation on the PCL nanofibers and that SrF2 increases the amount of deposited apatite. MTT results indicate that both strontium and GA do not have cytotoxic effects on human mesenchymal stem cells. GA enhances PCL wettability, allowing more water or culture medium to penetrate the pores of the scaffold, which increases Sr2+ release and, consequently, enhances cell adhesion and proliferation, ALP activity, biomineralization, and antibacterial activity. Overall, hybrid SrF2-PCL nanocomposite fibers immobilized with GA have significant potential for bone regeneration applications.