Melt-compounded polylactic acid composite hybrids with hydroxyapatite nanorods and silver nanoparticles: biodegradation, antibacterial ability, bioactivity and cytotoxicity

Abstract

Designing bulk polymer composite materials with firmly embedded nanofillers having good biocompatibility, high bactericidal activity and large scale production capability is considered of technological importance. Biodegradable polylactic acid (PLA) with 18 wt% hydroxyapatite nanorod (nHA) and silver nanoparticle (AgNP) of different loadings were fabricated by melt-compounding process. Hybridizing nHA with AgNP fillers in the PLA matrix permitted efficient attachment and proliferation of osteoblasts and good bactericidal ability of the resulting nanocomposites. This study aimed to evaluate the biodegradation, antibacterial ability, bioactivity and cytotoxicity of melt-compounded PLA/18% nHA–Ag hybrids using solution immersion, water contact angle, agar disk diffusion, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and biomineralization measurements. Weight-loss and water contact angle measurements showed that the nHA and Ag nanofillers increase the degradation rate and hydrophilicity of PLA, respectively; AgNPs were more effective than nHA for those tests. Disk diffusion test results demonstrated that the PLA/18% nHA–Ag hybrids show high bactericidal activity against Escherichia coli and moderate activity against Staphylococcus aureus. MTT test results revealed that high AgNP contents (18 and 25 wt%) in the PLA hybrids inhibit the proliferation of osteoblasts. However, composite hybrids with low loading Ag levels (2 and 6 wt%) showed good biocompatibility. Such hybrids maintained a good balance between antibacterial activity and cytocompatibility. Biomineralization test revealed that a dense apatite layer can be fully developed on the surfaces of PLA/18% nHA–Ag hybrids. The development of industrially scalable, efficient and cost effective polymer composite hybrids with good osteoconductivity and great bactericidal activity opens new perspective for bone tissue engineering applications.