Image-Guided Enhanced PDT/PTT Combination Therapy Using Brominated Hemicyanine-Loaded Folate Receptor-Targeting Ag2S Quantum Dots.

Tumor-targeting nanoparticles and phototherapies are the two major trends in tumor-specific, local cancer therapy with minimal side effects. Organic photosensitizers (PSs) usually offer effective photodynamic therapy (PDT) but require enhanced solubility and tumor-targeting, which may be provided by a nanoparticle. Near-infrared (NIR)-emitting Ag2S quantum dots may act as a delivery vehicle for the PS, NIR tracking agent, and as a phototherapy (PTT) agent. A combination of the two provides luminescent dual-phototherapy agents with tumor-specificity and image-guided and enhanced cytotoxicity as a result of synergistic PDT and PTT. In this study, brominated hemicyanine (Hemi-Br), a photosensitizer, was loaded onto folic acid (FA)-tagged, glutathione (GSH)-coated Ag2S quantum dots (AS-GSH QDs) to provide enhanced phototoxicity via a photodynamic and mild photothermal effect in folate receptor(+) cancer cell lines at clinically relevant 640 nm irradiation. Final particles (AS-GSH-FA/Hemi-Br) had a hydrodynamic size of 75.5 nm, dual emission at both 705 and 910 nm, and a 93% light-to-heat conversion efficiency under 640 nm laser irradiation. In vitro cytotoxicity studies were conducted with folate receptor (FR)-positive HeLa and -negative A549 cell lines to differentiate receptor-mediated uptake. Enhanced phototoxicity on HeLa cells was observed with AS-GSH-FA/Hemi-Br compared to free Hemi-Br and AS-GSH-FA QDs due to increased uptake of the photosensitizer via active targeting and combination therapy, which is especially visible at the safe dose of single agents. Upon irradiation with a 640 nm (300 mW, 0.78 W/cm2) laser for 5 min, the viability of the HeLa cells decreased from 64% to 42 and 25% when treated with free Hemi-Br, AS-GSH-FA, and AS-GSH-FA/Hemi-Br, respectively. Overall, AS-GSH-FA/Hemi-Br provides image-guided enhanced PDT/PTT, which may be adopted for different FR(+) tumors.

A hydrogen sulfide and tyrosinase responsive dual-locked fluorophore for selective imaging of melanoma cells.

A resorufin-based dual-locked fluorescent probe (RHT) was introduced to image melanoma cells selectively. RHT was shown to function as an AND molecular logic gate as it emitted a signal only in the presence of both hydrogen sulfide (H2S) and tyrosinase (Tyr), which are known to be overexpressed in melanoma cells. In vitro cell culture studies revealed that RHT can be activated with endogenous H2S and Tyr and allows selective imaging of B16-F10 cancer cells under confocal microscopy. RHT marks the first ever example of a fluorescent probe that is sequentially activated by H2S and Tyr.