Characterization of the absorption properties of 5 nm spherical gold nanoparticles functionalized with dodecanothiol and without functionalization with potential therapeutic applications

Hybrid nanosystems have useful properties for preparing therapeutic systems. Among the most commonly used inorganic components in hybrid nanosystems are gold nanoparticles (AuNP). The design of these nanosystems may require AuNP of hydrophilic or hydrophobic nature. Upon irradiation of AuNP, reactive oxygen species (ROS) are formed, and the temperature of the surrounding medium rises, depending on the size, shape and structure of the nanoparticle. The aim of this work is to evaluate whether irradiating 5 nm spherical gold nanoparticles both 'bare' (AuNP) and functionalized with dodecanethiol (AuNPf) with a Nd:YAG pulsed laser (30 ps, and 10 Hz) at wavelengths of 532 nm (0.031 J cm(-2)) and 1064 nm (1.91 J cm(-2)) produces ROS and heat sufficiently to induce cytotoxicity, or to demonstrate whether functionalization significantly influences such processes. It was verified by UV-vis spectrophotometry with ABMA and DCPIP that AuNP and AuNPf in solution induced ROS formation. They also produce a moderate elevation of the temperature of the surrounding medium. Irradiation of T47D cells at 532 nm in the presence of AuNP significantly decreased cell viability (>60%) compared to irradiation in the absence of NP (<20%). This effect was less evident when irradiating at 1064 nm because the cytotoxicity in the absence of AuNPs was very high (80%). AuNPf showed in solution a similar behavior to AuNP but due to the solvent in the suspension it was not possible to evaluate the cell toxicity caused by AuNPf. The results obtained indicate that it is feasible to design hybrid nanosystems for therapy from these 5 nm NPs, which would have photodynamic and photothermal effect.