An information processing triple input fluorescent probe for melanoma cancer

Abstract

Background

Multi-analyte responsive fluorescent sensors are promising tools for selective imaging of malignant tissues. Glutathione tripeptide is a common cancer biomarker. Tyrosinase enzyme is involved in melanogenesis and neuroactive dopamine synthesis. Activity/level of this enzyme is significantly altered in various diseases including melanoma and neurological diseases. Molecular tools capable of sensing different cellular states are yet to be developed. In the research presented here, a novel reconfigurable pyridinium functionalized distyryl-BODIPY P2 is developed as tyrosinase sensor with the synergistic effect of glutathione and carboxylesterase to discriminate different pathological cellular states.

Results

Acetyl-masked tyrosinase responsive 3-hydroxybenzyl substrate analogue is attached to the sensor. Following the ester hydrolysis by carboxylesterase, tyrosinase mediated oxidation to catechol followed by spontaneous 1,6-elimination generates pyridine BODIPY P1, resulting in 81 nm hypsochromic shift in aqueous solution compared to parent probe P2. Glutathione further enhances the response by removing acetyl group and/or reducing the quinone by-product back to cleavable quinol. A molecular AND logic gate can be constructed with enzymes and GSH, enabling multi-analyte melanoma sensing. Setting the fluorescence output threshold, distinct phenotypes can be diagnosed i.e. drug-resistant melanoma. Tyrosinase expressing B16–F10 melanoma cells display a significantly increased fluorescence when incubated with P2 compared to breast cancer cells. When inhibitor of any of the inputs is used, fluorescence intensity is significantly reduced, proving the synergistic effect of all disease parameters.

Significance

With versatile chemistry and sufficient solubility in aqueous media, this structure provides the first triple input Near-IR fluorescent sensor for melanoma with the potential of discriminating different pathological status. Modular structure can provide a common scaffold for information processing molecular sensors for hydrolytic/oxidoreductive enzymes and/or disease associated analytes.