Anti-Biofilm Properties and Conditions for 3D Printed Polymer Coatings in Combination with Antimicrobial Metal-Dispersed Alkoxysilane Coating Agents

Alkoxysilane-based resin with dispersed silver and copper composite nanoparticles was applied to resin-coated films made by 3D additive molding with micro-grooves on the surface, and the anti-biofilm properties were investigated according to ISO 4768. Two different polymer coatings were applied to the substrate, which was then coated with an alkoxysilane-based resin. The resin agent reacts with moisture in the air, hardens, and eventually adheres to the surface of the material, improving its environmental resistance in many ways. The resin layers with several irregularities were formed on the substrate surface by 3D modeling as a sample. After steam-pressure sterilization, the specimens were immersed in a bacterial solution containing Staphylococcus epidermidis in 1/5 TSB liquid medium at a concentration of 10^3 cfu/ml and incubated at 35°C for 48 hours. The biofilm was then stained with 0.1% crystal violet solution, wiped off with a non-woven cloth, dissolved in 1% sodium dodecyl sulfate, and irradiated with light at 595 nm to calculate absorbance. The absorbance corresponds to the amount of biofilm on the sample surface. The relationship between the surface irregularity structure and biofilm activity was investigated and discussed. Concretely speaking, the larger the peak-to-peak distance of the surface irregularities, the higher the anti-biofilm property, which means that the surface properties must be such that the liquid alkoxysilane resin can easily penetrate and solidify, thereby providing the required properties. This surface design is efficiently realized by 3D printing.