Gold Nanoparticle Synthesis, Characterization, and Photothermal Activation for Biomedical Application as a Bactericidal Agent

Gold nanoparticles were synthesized using the Turkevich method via trisodium citrate reduction of gold (III) chloride and then characterized using Ocean Optics and UV-VIS spectroscopy to determine the particles’ peak wavelength absorption. Relevant nanoparticle sizes, using dynamic light scattering, were determined to be approximately 21.87 nm in diameter. Given their unique optical properties at this size, gold nanoparticles can be employed in a plethora of ways within the biomedical field. Particularly, research regarding the growing antibiotic resistance crisis stands to benefit much from the use of nanoparticles, as the mechanisms of action by which they may combat bacteria are many and would be difficult to develop resistance to. In the present study, gold nanoparticles were introduced to bacteria Escherichia coli and Staphylococcus epidermidis at varying concentration levels on general nutrient agar in the hopes of delineating the relationship between the inhibition of bacterial growth and the presence of gold nanoparticles combined with high intensity laser irradiation. The subsequent irradiation of the bacteria using a 532 nm laser diode allowed the gold nanoparticles to become photothermally excited and emit heat to create localized hotspots within the nano-bio interface, leading to protein denaturing among other detrimental effects to the bacteria.