A graphene–poly(methacrylic acid)–gold bipyramid hybrid plasmonic nanocomposite for in vitro bioimaging and photothermal therapy

This study presents two new hybrid nanosystems (G-PMA(1 : 1)@AuBPs and G-PMA(1 : 3)@AuBPs), constructed from amine graphene (G-NH2) functionalized with poly(methacrylic acid) (PMA) and gold nanoparticles with a bipyramidal shape (AuBPs). These nanoplatforms behave like efficient photothermal agents, making them suitable for effective in vitro photothermal therapy and for bioimaging applications simultaneously. The nanosystems were synthesized by combining covalent and supramolecular approaches and characterized by several techniques including XPS, Raman spectroscopy, UV-vis spectroscopy, XRD, and STEM. It was observed that G-PMA@AuBP systems demonstrate remarkable light-to-heat conversion efficiency under near-infrared irradiation at 785 and 808 nm. Both systems showed an enhancement of the photothermal properties compared to the individual materials. Particularly, a photothermal conversion efficiency exceeding 70% was estimated for the G-PMA(1 : 3)@AuBP sample under 808 nm irradiation. Beyond their photothermal capabilities, G-PMA@AuBP systems can be effective as label-free bioimaging probes. G-PMA(1 : 1)@AuBP has been successfully visualized within B16F10 melanoma cells using FLIM, conventional fluorescence, and dark-field microscopy techniques, with localization observed in the perinuclear region. Cytotoxicity assays confirmed the biocompatibility of both nanosystems. Finally, the in vitro phototherapeutic efficacy was validated under 808 nm laser irradiation, showing promising results for melanoma cell treatment through photothermal therapy.