Fabrication of strontium/calcium containing poly(γ-glutamic acid) – organosiloxane fibrous hybrid materials for osteoporotic bone regeneration

Abstract

Recent researches have proved that combination of several therapeutic metal ions, such as silicate (Si), calcium (Ca), strontium (Sr) and so on, with biomaterials may have promising effects for stimulating bone regeneration. In the present study, the Sr/Ca containing silicate hybrid materials (Sr/Ca-γ-PGA-silica) with a mimetic native extracellular matrix (ECM) structure have been developed by electrospinning. With the aim to promote the solubility of γ-PGA in aqueous-based solution and introduce Sr/Ca elements into the prepared hybrid materials, SrCO₃ and CaCO₃ were employed due to their nontoxicity and no by-products during chemical reaction between γ-PGA and SrCO₃/CaCO₃. Results of SEM, EDX and elemental mapping images showed that Sr and Ca have been successfully incorporated into the prepared fibrous hybrid materials with homogeneous dispersion. Results of ICP-AES revealed that there was continuous Si, Sr and Ca ion release behavior of Sr/Ca-γ-PGA-silica hybrid materials in Tris–HCl buffer solution and the Si ions release rate can be tailored by adjusting the molar ratio of Sr to Ca. Immersion of Sr/Ca-γ-PGA-silica hybrid materials in a simulated body fluid (SBF) resulted in the formation of an apatite-like surface layer within 3 days, indicating their excellent bioactivity. In addition, the prepared Sr/Ca-γ-PGA-silica hybrid materials supported the proliferation and alkaline phosphatase (ALP) activity of osteoblast in vitro, showing their good biocompatibility. Altogether, the results indicated that the prepared Sr/Ca-γ-PGA-silica hybrid materials with an adjusted ionic release behavior have great potential for providing an excellent ECM for osteoporotic bone regeneration.