Biomimetic fabrication of antibacterial calcium phosphates mediated by polydopamine

In this work we developed new antibacterial composite materials using polydopamine (PDA) to trigger the deposition of silver nanoparticles (AgNPs) onto calcium phosphates, namely octacalcium phosphate (OCP) and Alpha-tricalcium phosphate (TCP). Functionalization of OCP and TCP with a self-polymerized polydopamine layer was obtained by soaking the calcium phosphates in dopamine solution. The PDA surface of functionalized calcium phosphates (OCPd and TCPd) promoted the deposition of AgNPs by reducing silver ions when soaked in a silver nitrate solution. The amount of deposited AgNPs can be modulated by varying the concentration of silver nitrate solution and the type of substrate. The results of in vitro tests carried out with osteoblast-like MG63 cells indicate that the combination of AgNPs with OCP provides more biocompatible materials than those obtained using TCP as substrate. In particular, the study of osteoblast activity and differentiation was focused on the samples OCPdAg5 (silver content = 8.2 wt%) and TCPdAg5 (silver content = 4.7 wt%), which did not show any cytotoxicity, and compared with those obtained on pure OCP and TCP. The results demonstrate that the AgNPs loaded materials support osteoblast viability and differentiation, whereas they significantly inhibit the growth of relevant antibiotic-resistant pathogenic bacteria.