NANOPHOTOSENSITIZERS FOR REGENERATIVE PHOTOTHERAPY OF TUMORS

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Abstract Inorganic nanoparticles (INPs) exhibit unique properties that favor their diverse application in medicine, engineering, science, and technology. The large surface-to-volume ratio of these INPs provides sites for the attachment of multiple drugs and/or imaging agents for therapy and imaging of diverse human diseases. Further conjugation of biological entities, such as proteins, nucleic acids, and lipids confers specific targeting of these INPs to desired tissues in vivo. Recent studies have shown that the intrinsic properties of some INPs can be harnessed for therapeutic outcomes, but spontaneous stimulation of intrinsic therapeutic effects through interactions of the NPs with intracellular organelles, proteins, or molecular processes is difficult to control, leading to significant off target toxicity. An alternative therapeutic approach can be achieved by harnessing the ability of some INPs to serve as efficient nanoscale energy transducers. Quantum dots, upconversion NPs, carbon nanomaterials, and photocatalytic NPs such as titanium dioxide nanoparticles are some nanoscale energy transducers that have shown promise in the treatment of human diseases. The excellent redox properties of these nanophotosensitizers offer high spatiotemporal control and precision phototherapy upon absorption of light. Two major limitations of current phototherapeutic interventions are the limited penetration of light used to activate the photosentizers, which confines therapy to shallow lesions, and the frequent reliance on oxygen to generate cytotoxic reactive oxygen species, which precludes effective treatment under the hypoxic conditions found in many solid tumors. We hypothesize that photoactivation of low radiance-sensitive nanophotosensitizers via depth-independent Cerenkov radiation will generate cytotoxic free radicals in an oxygen- independent manner for effective therapy. In this proposal, we will (1) Synthesize and optimize tumor-targeting nanophotosensitizers for effective spatiotemporal therapy of diseases; and (2) optimize orthogonally targeted radionuclides for selective delivery of Cerenkov radiation to pathologic cells and tissue. Using animal models of cancer, we will determine the efficacy of Cerenkov radiation mediated nano-phototherapy.