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.