Seed-Mediated Galvanic Synthesis of CuS-Au Nanohybrids for Photo-Theranostic Applications

Copper sulfide nanoparticles (CuS) have received attentionas apotential photothermal therapy (PTT) and photoacoustic imaging contrastagent for cancer theranostics. Prior studies suggest that functionalizedgold (Au) nanoparticles show anticancer effects. Hence, CuS/Au nanohybridsare being explored for various imaging and therapy operations. However,the relatively bigger size of such nanohybrids limits their applicationsfor deep tumor applications. This study specifically focuses on developingultrasmall CuS-Au (TSP-CA) nanohybrid using seed-mediatedgalvanic reduction of gold precursors on the surface of CuS nanoparticles.Tannic acid (TA) and sodium citrate were used as reducing agents toform Au nanoseeds and to impart its anticancer effect. Polyvinylpyrrolidone(PVP) was used as a stabilizing agent to form small PVP-CuSNPs. Furthermore, the hydrogen-bonding properties of TA and PVP wereutilized, followed by galvanic reduction to form the TSP-CAnanohybrids. These particles were expected to show reactive oxygenspecies (ROS) effect, and PTT influenced anticancer effects. The photoacoustic(PA) properties of the nanohybrids were also studied for their potentialas an exogenous contrast agent. The proposed nanohybrids attaineda mean size of 8 nm and retained their crystalline nature. The X-rayphotoelectron spectroscopy studies revealed the presence of Cu andAu. PA experiments indicated a higher signal-to-noise ratio. PTT efficiencywas estimated to be 25%, and the nanohybrid showed good photo stability.In vitro experiments suggest ROS-mediated anticancer effects on lungcancer cells. The nanohybrid was evaluated for PTT and PA signal generationusing ex vivo chicken breast studies at depths of 1 and 1.5 cm, respectively.PA signal was measured using an ultrasound transducer of 2.25 MHzcenter frequency and the laser operating at 960 nm at depths of 1cm. Additionally, the ROS and apoptosis studies revealed the enhancedanticancer effect of the hybrid nanoparticles compared to the individualnanoparticle category.