A Biomimetic Breast Tumor-On-Chip Platform Reveals Mesenchymal Marker Upregulation Following Gold Nanorod Photothermal Therapy.

Photothermal therapy (PTT) using plasmonic nanoparticles has emerged as a promising strategy for localized cancer treatment, yet physiologically relevant models for assessing cell-line model-dependent responses remain limited. Here, we engineered a breast tumor-on-chip platform to investigate gold nanorod (AuNR)-mediated PTT in a 3D type I collagen microenvironment using luminal-like MCF7 and triple-negative breast cancer MDA-MB-231 spheroids. A custom microfluidic architecture incorporating sliding-wall technology enabled controlled lateral perfusion with a spatially restricted thermal response consistent with localized AuNR-mediated heating within the central matrix compartment. Both tumor models exhibited pronounced cytotoxicity at temperatures above ∼50°C and showed comparable half-maximal responses in the Live/Dead ratio dose-response curves, corresponding to laser powers of approximately 0.48 and 0.38 W for MCF7 and MDA-MB-231 spheroids, respectively, despite their distinct epithelial and mesenchymal phenotypes. Immunofluorescence analyses 24 h after sublethal PTT revealed protein-level changes, including an increased vimentin-to-E-cadherin ratio and enhanced N-cadherin expression, particularly in MCF7 spheroids. Complementary gene expression analysis revealed treatment-associated modulation of apoptosis-, inflammation-, and epithelial-mesenchymal transition (EMT)-associated genes, although most changes in EMT-associated transcripts were modest and not statistically significant. Altogether, this work suggests treatment-associated alterations in selected mesenchymal markers in MCF7 spheroids following sublethal photothermal stress, warranting further temporal and functional validation.