Acidic Lysosome-Anchoring Croconium-Based Nanoplatform for Enhanced Triple-Mode Bioimaging and Fe3+-Triggered Tumor Synergistic Therapy.

Metal-modulated croconium dyes with multimodal-imaging and synergistic therapy in the tumor microenvironment have exhibited great potential in tumor theranostics. However, their unideal structure optimization always weakened the efficacy of near-infrared fluorescence-photoacoustic (NIRF/PA) imaging and photothermal therapy (PTT). Here, we screened croconium dye containing two indole groups with better NIRF/PA imaging and PTT in their family, linked to two morpholine rings, and obtained CR-736, as a lysosome-targeting and Fe3+-modulated agent. The established CR-736-Fe3+ nanoplatform was accurately delivered to the breast tumor site, released CR-736 and Fe3+ in the lower acidic lysosome microenvironment, and activated pH-responsive NIRF/PA/magnetic resonance imaging and PTT. Furthermore, ferroptosis generated hydroxyl free radicals and lipid peroxide by consuming GSH and H2O2 by dint of the accumulation of Fe3+ in tumor cells, which resulted in the inhibition of the expression of heat shock proteins and the concomitant recovery of PTT. The synergistic therapy of PTT, ferroptosis, and chemodynamics was further optimized to the maximal extent in tumor lysosome acidic microenvironment and proved both in vitro and a mouse tumor model. This study opens a new avenue in designing excellent and unique croconium-based nanoplatforms, synergizing multiple tumor theranostic methods, and further optimizing the theranostic effects in tumor microenvironment.

Water-solubility croconic acid-bisindole dye with morpholine ring for tumor NIRF/PA imaging and photothermal therapy activated by lysosome pH-response.

A novel croconic acid-bisindole dye CR-630 with a morpholine ring showed good water-solubility and obvious lysosome-targeting. The protonation of the nitrogen atom in the indole and lysosome-targeting of morpholine ring let it exhibit stronger pH-responsive NIR/PA imaging and photothermal effect in the lysosome acidic microenvironment (pH 4.0-5.5) than in the tumor acidic microenvironment. In the animal study, compound CR-630 could NIRF/PA image in the tumor tissues in 1.5-2.0 h, effectively inhibit the growth of the tumor, and even ablate the tumor at the drug dose of 1 mg/kg. It also demonstrated good biosafety. This study gives a new idea to develop water-solubility organic dyes with lysosome targeting, stronger pH-responsive NIRF/PA imaging and PTT for breast cancer.