Sub-micrometric mesoporous strontium substituted hydroxyapatite particles for sustained delivery of vancomycin drug

In this study, mesoporous strontium substituted hydroxyapatite (SrHAP) powders with individual sub-micrometric particle morphologies of irregular particles (SrHAP-IP) and nanostructured spherical particles (SrHAP-SP) were tested for vancomycin loading and releasing abilities. Initially, structural and physicochemical properties of synthesized products were comprehensively investigated. XRD analysis identified HAP as a chief phase in both SrHAP-IP and SrHAP-SP powders. Rietveld refinement suggested that HAP nanocrystals had appropriate lattice parameters and subjected to tensile strain. FESEM and HRTEM evaluations suggested that the particles of SrHAP-IP and SrHAP-SP powders were irregular (0.14 ± 0.04 μm) and nanostructured assembled burr-like spheres (0.88 ± 0.23 μm) in shape, respectively. SAED and lattice fringes corroborated the polycrystalline structure of both powders. EDX corroborated the formation of strontium substituted apatite in both powders. Isotherms suggested the mesoporous structure having specific surface area of 74.666 and 32.450 m 2 g −1 for SrHAP-IP and SrHAP-SP powders, respectively. SrHAP-SP powder was 2.3 times more porous than SrHAP-IP powder. Accordingly, SrHAP-SP powder exhibited 44% higher vancomycin loading efficiency than SrHAP-IP powder. Although, both powders exhibited sustained drug release during longer incubation, but drug releasing rate of SrHAP-SP powder was relatively more than SrHAP-IP powder. Thus, this study made it apparent that difference in structural and physicochemical properties of SrHAP powders influenced their drug loading and releasing efficacies.