Atorvastatin loaded PLGA microspheres: Preparation, HAp coating, drug release and effect on osteogenic differentiation of ADMSCs.

Polymer/bioceramic composite micro-particles have been used for bone regeneration in order to address weak mechanical properties/bioactivity of polymers and to enable easy filling of irregular bone defects through minimally invasive injection procedure. The purpose of this study was to determine whether injectable apatite-coated atorvastatin (AT) loaded Poly (d,l-lactide-co-glycolide) (PLGA) micro-particles can support osteogenic differentiation of adipose derived mesenchymal stem cells(ADMSCs). Particle preparation conditions (oil-in-water (O/W) emulsion), were carefully adjusted to yield uniform particles of about 20-50 µm in diameter. Taking a solid in oil-in water (S/O/W) emulsion strategy, it became possible to load atorvastatin (10 wt%) in the micro-particles without deformation. The particles were then coated with HAp by incubation in 10X simulated body fluid (SBF). The apatite coating layer was similar to apatite in natural bone, as demonstrated by SEM, XRD, and FTIR analyses. Adipose derived mesenchymal stem cells (ADMSCs), were cultured on the micro-particles and calcium deposition measurement was performed through Alizarin Red assay. Initial cell adhesion did not differ significantly between the samples and the control. The strongest osteogenic differentiation was observed on PLGA-AT-HAp in both the osteogenic and non osteogenic culture media, while PLGA-AT slightly decreased and PLGA-HAp slightly increased osteogenic differentiation of the cells, indicating suitability of PLGA-AT-HAp as an injectable tissue engineering system.