Polydopamine-Assisted Hydroxyapatite and Lactoferrin Multilayer on Titanium for Regulating Bone Balance and Enhancing Antibacterial Property

Maintaining the balance between bone formation and bone resorption as well as reducing bacterial infection are two major challenges for titanium (Ti) when it is used as the implant in orthopedic surgery. Because of its excellent properties, including anti-inflammatory, antimicrobial, promoting osteoblasts, and inhibiting osteoclasts growth, lactoferrin (LF) is a potential bioactive molecule for surface modification of Ti implants. Inspired by the highly hierarchical structure of natural bone tissue, in this work, a polydopamine-assisted hydroxyapatite and lactoferrin multilayer structure (PDA-HALF) was prepared onto the Ti substrate surface by a biomimetic approach and spin-assisted layer-by-layer (LBL) assembly technique. Meanwhile, its capabilities on regulation of bone balance and antibacterial properties were measured with cell experiments and antimicrobial activity in vitro. Furthermore, the regulation theory was investigated by qPCR and theoretical simulation. The results showed that the biological properties of LF are highly correlated with its concentration. High concentration of LF was toxic to osteoblasts but has obvious effects on inhibition of osteoclasts and bacteria (S. aureus and E. coli). However, through polydopamine-assisted hydroxyapatite deposition, cytotoxicity of LF could be improved. The modified Ti implant could greatly improve the proliferation and differentiation of osteoblasts. Meanwhile, the activity of osteoclasts was somewhat inhibited, which indicated that the modified Ti implant could efficiently regulate the balance between bone resorption and bone formation, as well as have a certain antibacterial effect.