Molybdenum Disulfide Surfaces to Reduce Staphylococcus aureus and Pseudomonas aeruginosa Biofilm Formation

Abstract

The reduction of bacteria and biofilm formation is important when designing surfaces for use in industry. Molybdenum disulfide surfaces (MoS_2SUR) were produced using MoS₂ particle (MoS_2PAR) sizes of 90 nm, 2 μm, and 6 μm containing MoS_2PAR concentrations of 5%, 10%, 15%, and 20%. These were tested to determine the efficacy of the MoS_2SUR to impede bacterial retention and biofilm formation of two different types of bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. The MoS_2SUR were characterized using Fourier transform infrared spectroscopy, ion-coupled plasma atomic emission spectroscopy, scanning electron microscopy, optical profilometry, and water contact angles. The MoS_2SUR made with the smaller 90 nm MoS_2PAR sizes demonstrated smaller topographical-shaped features. As the size of the incorporated MoS_2PAR increased, the MoS_2SUR demonstrated wider surface features, and they were less wettable. The increase in MoS_2PAR concentration within the MoS_2SUR groups did not affect the surface topography but did increase wettability. However, the increase in MoS_2PAR size increased both the surface topography and wettability. The MoS_2SUR with the smaller topographical-shaped features influenced the retention of the S. aureus bacteria. Increased MoS_2SUR topography and wettability resulted in the greatest reduction in bacterial retention, and the bacteria became more heterogeneously dispersed and less clustered across the surfaces. The surfaces that exhibited decreased bacterial retention (largest particle sizes, largest features, greatest roughness, and most wettable) resulted in decreased biofilm formation. Cytotoxicity testing of the surface using cell viability demonstrated that the MoS_2SUR were not toxic against HK-2 cells at MoS_2PAR sizes of 90 nm and 2 μm. This work demonstrated that individual surface variables (MoS_2SUR topographic shape and roughness, MoS_2PAR size, and concentration) decreased bacterial loading on the surfaces, which then decreased biofilm formation. By optimizing MoS_2SUR properties, it was possible to impede bacterial retention and subsequent biofilm formation.

Keywords: antifouling; bacteria; biofilms; cytotoxicity; molybdenum disulfide surfaces; retention.