Tunable gelatin-coated biosynthesized gold nanotriangles: Thermoplasmonic performance and in vitro therapeutic potential via on-demand visible-NIR LED activation

In this work, we report a green and surfactant-free biosynthesis of gold nanotriangles (AuNTs) using gelatin as a multifunctional stabilizing and biocompatible capping agent. Gelatin effectively mediated particle growth in the presence of ascorbic acid, enabling precise tuning of the longitudinal localized surface plasmon resonance (LSPR) of AuNTs between 880 and 1090 nm through control of size and morphology. The resulting LSPR within the NIR-II plasmonic window provides distinct therapeutic advantages, including deeper tissue penetration, reduced light scattering, and diminished tissue autofluorescence, highly relevant for clinical translation. Here, we present a systematic evaluation of the thermoplasmonic performance of biosynthesized AuNTs under low-cost LED irradiation across the visible and NIR biological windows, yielding photothermal conversion efficiencies of up to ∼65 % in the NIR range. Comparable thermoplasmonic responses were obtained under two laser sources (532 nm and 980 nm), therefore demonstrating the efficiency of LED as irradiation sources for NIR responsive AuNTs. In vitro investigations demonstrated negligible intrinsic cytotoxicity of gelatin-stabilized AuNTs and confirmed the cellular uptake in two breast cancer lines (i.e., MDA-MB-231 and MCF-7). Upon irradiation, distinct cell-type-dependent responses were observed, with significant photothermal cytotoxicity (47 %) induced particularly in MCF-7 cells under 850 nm exposure. Taken together, these results establish gelatin-biosynthesized AuNTs as efficient, biocompatible light-to-heat nanotransducers and highlight the potential of LED-driven photothermal therapy across the visible and NIR spectral regions.