Preparation of Raspberry-Like PDA-Cu NPs Nanoparticles with Antibacterial Properties

In this paper, raspberry-like polydopamine/copper nanoparticles (PDA-Cu NPs) were constructed by simply adjusting the contents of copper source and reduction temperature on the basis of good adhesion properties of polydopamine (PDA) with metal particles. The successful introduction of copper nanoparticles was confirmed by measurements of X-ray diffraction (XRD) and Zeta potential. Scanning electron microscopy (SEM) results showed that the raspberry-like structure had been successfully constructed. When the reduction temperature was 60 ℃, the copper nanoparticles had more uniform particle size. When the mass ratio of PDA to copper nitrate was more than 1/6, the copper nanoparticles were evenly distributed on PDA particles. The static contact angle measurements revealed that the introduction of copper nanoparticles increased the surface roughness of the PDA particles, and the surface contact angle was up to 102.2°, showing that the modified particles turned from hydrophilic to hydrophobic. At the same time, copper nanoparticles had good antibacterial properties. The antibacterial activity of raspberry-like nanoparticles was evaluated by shake flask method. Compared with pure dopamine nanoparticles, PDA-Cu NPs had excellent antibacterial properties. With the increase of copper content, 100% sterilization could be achieved, and its antibacterial performance against S.epidermidis was better than that of E.coli. The bacterial zone experiments showed that PDA-Cu NPs (1/6, mass ratio of PDA to copper nitrate) had a clear zone of inhibition and its diameter was larger than that of PDA-Cu NPs (1/8), suggesting the optimal antibacterial properties. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of raspberry-like nanoparticles made from optimal reaction conditions for E.coli were 48.7 μg/mL and 195.0 μg/mL, respectively, while the MIC and MBC values for S.epidermidis were 39.0 μg/mL and 97.5 μg/mL, respectively. Raspberry-like nanoparticles showed good abtibacterial properties, which were expected to have a good application in biomedical fields.