Nisin-loaded polydopamine/hydroxyapatite composites: Biomimetic synthesis, and in vitro bioactivity and antibacterial activity evaluations

Microbial contamination caused by bacterial adhesion and colonization onto the materials surfaces has long been a serious threat to human health. Thus, it is imperative to develop advanced antimicrobial materials for bio-applications. Here, a unique polydopamine/ hydroxyapatite/nisin (PDA/HAP/Nisin) composite with good bioactivities and enhanced antibacterial activities have been developed. The uniform PDA particles are first prepared via the dopamine self-polymerization in an alkaline water-ethanol mixed solvent. Due to the abundance surface catecholamine moieties, PDA particles can serve as the powerful templates for the in-situ mineralization of hydroxyapatite (HAP) in a simulated body fluid (SBF) solution, forming PDA/HAP composites. Transmission electron microscopy, scanning electron microscopy, transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction are used to investigate the morphology, surface composition, and crystalline structure of the PDA/HAP composites. These PDA/HAP composites are utilized as the reservoir for loading the antimicrobial peptide–nisin. Ultraviolet visible spectrophotometry analysis shows that PDA/HAP composites have exhibited a high loading capacity and a superior loading efficiency for nisin. The resulting PDA/HAP/Nisin composites are ideal antimicrobial biomaterials for bio-application because they exhibit not only a significant in vitro cytocompatibility to human embryonic kidney HEK293 T cells, but also the enhanced antibacterial activities against Staphylococcus aureus (Gram-positive bacteria). These advantageous properties of the PDA/HAP/Nisin composites allow them as the promising candidates for a broad range of bio-applications, e.g., drug delivery, implant engineering, and bio-scaffold.