André Ferreira Moreira

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%.

Introduction: In today's world, cancer remains a major public health problem. Consequently, there has been a focused investigation of alternative therapeutic approaches to address this ongoing health concern. In this study, PLGA-gold nanomaterials were produced through various processes to determine whether these variations affected their structural integrity and, consequently, their physicochemical properties. Methods: The PLGA-gold nanomaterials were produced through an oil-in-water (O/W) process (Formulation A) or a water-in-oil-in-water (W1/O/W2) process (Formulation B). The nanomaterials' physiscochemical properties were characterized by electron microscopy, dynamic light scattering, and UV-vis. Photothermal studies were performed using a 808 nm NIR laser and the PLGA-gold nanomaterials cytocompatibility was evaluated using resazurin. Results: Both methods originated particles with similar size and charge, 276.8 and –19.6 mV for formulation A and 317.5 nm and –18.6 mV for formulation B. Nevertheless, the TEM images revealed structural differences, with formulation A presenting the gold spheres clustered in the particle nucleus, whereas in formulation B the gold spheres were found in the outer PLGA shell. Moreover, upon irradiation with a NIR laser (808 nm, 1.7 W cm–2, 10 min), the particles showed a concentration dependent photothermal effect, promoting a temperature increase of 21 °C and 13.9 °C for formulation A and B at 400 μg/mL, respectively. Additionally, preliminary cellular assays demonstrated that the PLGA-gold nanoparticles are cytocompatible, with both FibH and HeLa cells exhibiting a cellular viability of approximately 100%. Conclusion: Thus, these results underline the potential the PLGA-gold nanoparticles, particularly formulation A, for advanced applications in nanomedicine. In the future the encapsulation of drugs will be evaluated in order to characterise both the uptake and the cytotoxic capacity of this multifunctional nanomaterial. Additionally, the utilization of more complex in vitro models, such as tumor spheroids and animal models, will then be essential to determine the therapeutic potential of PLGA/gold nanoparticles.

Gold nanoparticles (AuNPs) possess unique properties, including low toxicity and excellent optical characteristics, making them highly appealing for biomedical applications. The plasmonic photothermal effect of AuNPs has been explored to trigger localized hyperthermia. Four commonly explored gold nanoparticles (spheres, rods, stars, and cages) are produced and optimized to present the localized surface plasmon resonance effect in the near-infrared region, exploiting the increased penetration in the human body. Additionally, the production of hybrid AuNPs, combining them with other materials, such as silica, graphene, zinc oxide, polymers, and small molecules has been explored to amplify the photothermal effect (T ≥ 45ºC). This review provides an overview of AuNPs' application in photothermal therapy, describing the general synthesis processes and the main particle parameters that affect their application in photothermal therapy, including the hybrid nanomaterials. Associated with this rapid progress, surface functionalization can also improve colloidal stability, safety, and therapeutic outcomes. In this regard, we also highlight the emerging trend of applying cell-derived vesicles as biomimetic coatings, capable of evading immune recognition, increasing blood circulation, and targeting specific tissues. In addition, the challenges and future developments of AuNPs for accelerating the clinical translations are discussed in light of their therapeutic and theragnostic potential.