Photothermal activity in cancer therapy and antimicrobial properties of green gold nanoparticles from winery waste

Nanomaterial-mediated photothermal therapy is an emerging approach to cancer care; however, the required biocompatibility of nanoparticles remains a critical aspect. To enhance their biocompatibility, biocompatible sources can be used in nanoparticle preparation instead of the conventional toxic substances that are generally required. To this end, grape marc, obtained as agricultural waste from the winery industry, was chosen as an important source of natural compounds. By modifying the nanoparticle surface, it can form a crucial interface with the surrounding environment. In this work, green gold nanoparticles were synthesized and applied in photothermal therapy, and their biocompatibility, antitumor, and antibacterial properties were evaluated. Reducing sugars and polyphenolic compounds, naturally occurring in grape marc waste, were extracted in water and successfully employed in the preparation of gold nanoparticles, as confirmed by the appearance of a plasmonic band at 535 nm. A second peak at 286 nm, typical of phenolic groups, demonstrated the presence of a polyphenolic layer on the nanoparticle surface, which was also confirmed in FTIR studies. TEM and XRD analyses revealed their crystalline nature, with an average diameter of about 30 nm. A third absorption peak in the near-infrared region (750 nm) shows that the synthesized gold nanoparticles can be good photothermal agents with a temperature increase of about 22 °C after 10 minutes of NIR laser irradiation (808 nm and 1.7 W cm−2). Good biocompatibility with human fibroblasts and breast cancer cells (MCF-7) was also demonstrated at high concentrations (400 µg mL−1), with the cell viability remaining above 70% during 72 hours of incubation. Antibacterial and antitumoral effects of the synthesized nanoparticles were observed after NIR laser irradiation, with 41.7% and 52.5% cell viability inhibition in S. aureus and E. coli, respectively, at higher concentrations, and a reduction of MCF-7 cell viability to 37%.