Gold-Decorated Porous Silicon Nanopillars for Targeted Hyperthermal Treatment of Bacterial Infections

In order to address the issue of pathogenic bacterial colonization of diabetic wounds, a more direct and robust approach is required, which relies on a physical form of bacterial destruction in addition to the conventional biochemical approach (i.e., antibiotics). Targeted bacterial destruction through the use of photothermally active nanomaterials has recently come into the spotlight as a viable approach to solving the rising problem of antibiotic resistant microorganisms. Materials with high absorption coefficients in the near-infrared (NIR) region of the electromagnetic spectrum show promise as alternative antibacterial therapeutic agents, since they preclude the development of bacterial resistance and can be activated on demand. Here were report on a novel approach for the fabrication of gold nanoparticle decorated porous silicon nanopillars with tunable geometry that demonstrate excellent photothermal conversion properties when irradiated with a 808 nm laser. These photothermal antibacterial properties are demonstrated in vitro against the Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). Results show a reduction in bacterial viability of up to 99% after 10 min of laser irradiation. We also show an increase in antibacterial performance after modifying the nanopillars with S. aureus targeting antibodies causing up to a 10-fold increase in bactericidal efficiency compared to E. coli. In contrast, the nanomaterial resulted in minimal disruption of metabolic processes in human foreskin fibroblasts (HFF) after an equivalent period of irradiation.