A comparative insight into the mechanical properties, antibacterial potential, and cytotoxicity profile of nano-hydroxyapatite and nano-whitlockite-incorporated poly-L-lactic acid for bone tissue engineering

This work reports the synthesis and characterization of nanohydroxyapatite (nHA) and nanowhitlockite (nWH), which were further incorporated to poly-l-lactic acid (PLLA) to study their effects on the structure, mechanical properties, antibacterial potential, and cytotoxicity of PLLA. SEM images of PLLA-nHA and PLLA-nWH revealed uniform dispersion of nanoparticles in polymer. FTIR spectroscopy showed shift in functional group position and indicated transformation of PLLA alpha ' to more crystalline PLLA alpha, which was further confirmed by X-ray diffraction. The mechanical properties of the materials showed that addition of nanoparticles have made PLLA ductile and strong pertaining to the effective dissipation of loads across the interfaces, enabling them to delay the crack growth by avoiding stress concentration sites. PLLA-nWH10% showed the highest antibacterial activity against Gram-positive bacteria Listeria monocytogenes and Staphylococcus aureus. In vitro cytocompatibility of PLLA-nWH10% was highest, 98%, at day 7 against fibroblasts MC3T3-E1 (osteoblastic cell line), whereas all nanocomposites have enhanced cell viability (94%) as compared to pure PLLA. Alizarin red assay showed twofold increase in calcification at day 14 with PLLA-nWH as compared to PLLA-nHA. It was clearly observed that binary system PLLA-nWH at all concentrations had good dispersion and interfacial interaction resulting in improved mechanical and enhanced osteoconductive properties as compared to PLLA-nHA.