PROJECT SUMMARY Our goal in this R15 proposal is to investigate the photoreduction of Pt(IV) complexes as a new versatile approach for NIR-uncaging that can operate both in vitro and in vivo. Photo-uncaging is a technique that selectively blocks biologically relevant functional groups, enabling external spatiotemporal control with light. Targeted light-induced cleavage is used to achieve uncaging and release the photolabile protecting group, providing a means to regulate the amount of the relevant compound released. However, the current limitation of photolabile protecting groups has largely restricted photo-uncaging technology to the use of UV light. NIR light (700–1000 nm) can penetrate deeper into biological tissues, making it a promising candidate for biomedical research and phototherapy. This R15 proposal aims to present a new approach toward overcoming such drawbacks by inventing novel fluorophore-conjugated Pt(IV) complexes for NIR-uncaging. The central hypothesis is that photoreduction of Pt(IV) complexes enables NIR-uncaging of bioactive ligands. This hypothesis is based on our preliminary data: 1). photoinduced electron transfer empowers rapid activation of Pt(IV) complexes via conjugation with fluorophores. 2). conjugation of the Pt(IV) complex with IR780 (a lipophilic NIR dye) enables photoreduction upon NIR irradiation. 3). the use of carboplatin as the Pt core generate Pt(IV) complexes with excellent stability against biological reductants without additional protection. 4). the fluorophores being used in the scaffold dictate the wavelength of light irradiation from visible to NIR. To test our central hypothesis, we hereby present a three-year research project composed of two specific aims. Aim 1 of our proposal is dedicated to synthesizing new Pt(IV) complexes using the aforementioned scaffold and investigating their photo-uncaging properties. In Aim 2, we aim to enhance the potential of our newly developed photo- uncaging technology by validating and optimizing NIR-uncaging of drug molecules in vitro and in vivo. Successful completion of Aim 1 will not only illustrate the scaffold's adaptability but also provide valuable information on the photoreduction properties of the Pt(IV) complexes. The successful completion of Aim 2 could lead to the development of a new NIR photo-uncaging technology with numerous noteworthy applications in different domains, including drug delivery and phototherapy. The educational goal of this R15 proposal is to enhance undergraduate student biomedical research at Kent State University (KSU). Based on the different background of the two PIs, including bioinorganic chemistry and cell biology, we seek to establish a multidisciplinary research program to support three undergraduate students and one graduate student at KSU every year.