Candle-derived carbon soot nanoparticles as Photothermal agents for controlled opening of the blood–brain barrier

Targeted modulation of the blood–brain barrier (BBB) can improve delivery of macromolecular therapeutics to the central nervous system. We developed candle-derived carbon soot nanoparticles as low-cost photothermal agents for controlled BBB opening. Acid-purified soot was characterized by TEM, XPS and UV–Vis, showing broad absorption (200–1000 nm) and efficient heating under 808 nm irradiation (1 W cm −2 ). In vitro assays in b.END3 and HT22 cells indicated minimal cytotoxicity. In C57BL/6 mice, intravenous soot (50 mg kg −1 ) followed by localized 808 nm laser exposure (5 min) raised cortical temperature by ~30 °C and markedly increased BBB permeability, evidenced by Evans blue extravasation and enhanced delivery of Cy5–BSA and FITC–dextran tracers. Tight-junction proteins ZO-1, claudin-5, and occludin were transiently downregulated. These results establish candle-soot nanoparticles as effective, biocompatible photothermal mediators for noninvasive, reversible BBB disruption.