Strontium-hydroxyapatite incorporated Poly(Hydroxybutyrate-CO-Hydroxyvalerate)/ Poly(Lactic-CO-Glycolic Acid) electrospun nanofibers for bone tissue engineering scaffold

Abstract

Hydroxyapatite polymer nanofibers composites offer many advantages such as good osteoconductivity, bone bonding ability, and also mimicking the bone extracellular matrix (ECM). In particular, strontium-hydroxyapatite (Sr-HA) has the ability to enhance osteogenesis as compare to neat hydroxyapatite (HA). Therefore, the Sr-HA has been incorporated within polymer nanofiber scaffolds to develop composite materials for bone tissue application. In this study, biodegradable composites scaffolds were fabricated by electrospinning technique. It was composed of poly (lactic-co-glycolic acid) (PLGA) and poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV), optimized at 50:50 weight ratio with a solution concentration of 26 % (w/v). The physicochemical properties of the HA and Sr-HA nanoparticles were then characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), selected area electron diffraction analysis (SAED), surface area analysis, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD). Meanwhile, the physicochemical properties of the scaffolds, known as PHBV/PLGA, PHBV/PLGA/HA and PHBV/PLGA/Sr-HA were characterized by scanning electron microscopy (SEM), EDX, pore size, porosity, atomic force microscopy (AFM), water contact angle, ATR-FTIR, and thermogravimetric (TGA) analyses. Mechanical properties were quantified by tensile test. Other characterizations include bioactivity and biodegradation test were also performed. According to the results, optimization of electrospinning parameters had produce homogenous and smooth nanofibers with an average diameter of 600 - 700 nm and porosity of ~78 %. The addition of either HA or Sr-HA nanoparticles has improved the surface roughness, bioactivity, and tensile strength of the composites as compare to PHBV/PLGA scaffold. The nanofiber scaffolds have suitable mechanical properties for bone tissue application with a tensile strength up to ~1.3 MPa and a Young’s Modulus of ~ 45 MPa. The scaffolds have slow degradation rate with less than 10 % weight loss that is suitable for bone regeneration. Finally, the biocompatibility of the scaffolds was evaluated through in vitro cell culture with human skin fibroblast cells (HSF 1184) and human fetal osteoblast cells (hFOB 1.19). Cellular activities such as morphology, attachment and proliferation, were analyzed by SEM, cytoskeletal staining, MTT, and live/dead assay. The results showed that the scaffolds have promoted cellular adhesion and proliferation due to their nanoscale topography similar to the ECM, in addition to porous and high surface roughness. The biocompatibility and cell viability of osteoblast were enhanced with a demonstration of greater alkaline phosphatase activity by the PHBV/PLGA/Sr-HA scaffold. In conclusion, we proposed that PHBV/PLGA/Sr-HA nanofiber scaffold can be a potential material for bone tissue application.