Poly(γ-glutamic acid)–silica hybrids with fibrous structure: effect of cation and silica concentration on molecular structure, degradation rate and tensile properties

Abstract

Biodegradable organic/inorganic hybrid fibremats were prepared by electrospinning using poly(γ-glutamic acid) (γ-PGA) and glycidoxypropyl trimethoxysilane (GPTMS) for application in bone tissue engineering. Ca(OH)₂ was used for preparing the calcium salt form of γ-PGA (Ca-γPGA), which is water-soluble. Effects of the amount of Ca(OH)₂ mixed with γ-PGA on the chemical structure and characteristics of resulting hybrid fibremats were studied. ATR-FTIR data indicated that cross-linking between γ-PGA chains was achieved due to the coupling reaction between the polymer side chain and epoxy terminated group of GPTMS and silica network formation between GPTMS molecules. ¹³C CP/MAS-NMR and ²⁹Si MAS-NMR spectra indicated that open epoxy groups in GPTMS reacted with each other and the rate of condensation between its silanol groups was lower when the added amount of Ca(OH)₂ was smaller. Tensile test data demonstrated that elongation to failure was improved for the hybrid fibremat in comparison with just Ca-γPGA fibremats.