Precisely controlled polydopamine-mediated antibacterial system: mathematical model of polymerization, prediction of antibacterial capacity, and promotion of wound healing

In this work, the polydopamine (PDA)-mediated antibacterial system is synthesized to carry out antimicrobial activities in vitro and in vivo. First, to precisely control the surface modification of nanodiamonds (NDs), a mathematical kinetics model of PDA deposition is established, and the conditions of synthesis reaction are discussed including influencing factors such as the concentrations of dopamine, reaction time, and the kinetic constant k1, which is a function of several variables associated with the reaction temperature, light irradiance (especially at ultraviolet wavelengths), pH value and concentration of dissolved O2 in the solution. A simulated visualization demonstrates that the deposition thickness of PDA is positively correlated with temperature and light irradiance, and PDA is easier to deposit in an alkaline solution and will be terminated if the dissolved O2 is insufficient. Then, the precisely controlled thickness of PDA can control the growth of AgNPs, rendering the intensity of Raman peaks increased and providing a predictable antibacterial effect against E. coli in vitro. An optimized antibacterial hydrogel containing NDs-PDA/Ag is prepared and characterized by the Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Finally, the antibacterial experiments to promote wound healing in vivo are performed, which are verified by pathological and immunohistochemical-stained sections. This work provides a theoretical basis of predicting the PDA-assisted surface modification of NDs, giving a divinable antibacterial effect, and promoting wounds healing in vivo.