Tumor thermal damage assessment in nanoparticle-mediated photothermal therapy with hyperspectral imaging: preliminary in vivo results in a syngeneic 4T1 mouse model

Photothermal therapy (PTT) using plasmonic nanoparticles is a promising, minimally invasive approach for solid tumors, yet label-free assessment of thermal damage remains challenging. We report preliminary in vivo results on the use of hyperspectral imaging (HSI, 400–1000 nm) to characterize photothermally induced tissue changes in a syngeneic 4T1 triple-negative breast cancer mouse model. Experiments included a control condition, i.e., laser irradiation after tumor injection of phosphate-buffered saline (PBS), and nanoparticle-treated tumor-bearing mice subjected to identical laser irradiation. Reflectance hypercubes were acquired and processed through white/black normalization and region-of-interest analysis at the tumor core with a reference site. Spectral descriptors emphasized hemoglobin-family bands and their thermo-chemical evolution, focusing on the 600–800 nm window where slope and peak shifts are consistent with methemoglobin formation, alongside broader trends approaching the water-influenced region toward 900–1000 nm. Smoothed spectral representations enabled comparison of pre-laser and short-term follow-up states. Across nanoparticle-treated tumors, we observed reductions in reflectance and altered spectral slopes within 600–800 nm, whereas the control showed weaker or localized changes. These findings support HSI as a non-invasive, wide-field, and spectrally informed readout for tumor thermal damage assessment in nanoparticle-mediated PTT. The adopted approach aligns with biophotonics goals of therapy guidance and may assist dose selection and endpoint definition in photothermal procedures.