Red Light Activation of Ru(II) Polypyridyl Prodrugs via Triplet-Triplet Annihilation Upconversion: Feasibility in Air and through Meat

Red Light Activation of Ru(II) Polypyridyl Prodrugs via Triplet-Triplet Annihilation Upconversion: Feasibility in Air and through Meat

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Triplet-triplet annihilation upconversion (TTA-UC) is a promising photophysical tool to shift the activation wavelength of photopharmacological compounds to the red or near-infrared wavelength domain, in which light penetrates human tissue optimally.However, TTA-UC is sensitive to dioxygen, which quenches the triplet states needed for upconversion.Here, we demonstrate not only that the sensitivity beetroot birkenstock of TTA-UC liposomes to dioxygen can be circumvented by adding antioxidants, but also that this strategy is compatible with the activation of ruthenium-based chemotherapeutic compounds.First, red-to-blue upconverting liposomes were functionalized with a blue-light sensitive, membrane-anchored ruthenium polypyridyl complex, and put in solution in presence of a cocktail of antioxidants composed of ascorbic acid and glutathione.Upon red light irradiation with a medical grade 630 nm PDT laser, enough blue light was produced by TTA-UC liposomes under air to efficiently trigger full activation of the Ru-based prodrug.

Then, the blue light generated by TTA-UC liposomes under red light irradiation (630 nm, 0.57 W/cm2) through different thicknesses of pork or chicken superdry baseball top meat was measured, showing that TTA-UC still occurred even beyond 10 mm of biological tissue.Overall, the rate of activation of the ruthenium compound in TTA-UC liposomes using either blue or red light (1.6 W/cm2) through 7 mm of pork fillet were found comparable, but the blue light caused significant tissue damage, whereas red light did not.Finally, full activation of the ruthenium prodrug in TTA-UC liposomes was obtained under red light irradiation through 7 mm of pork fillet, thereby underlining the in vivo applicability of the activation-by-upconversion strategy.