Dynamics of Oxygen-Independent Photocleavage of Blebbistatin as a One-Photon Blue or Two-Photon Near-Infrared Light-Gated Hydroxyl Radical Photocage

Abstract

Development of versatile, chemically tunable photocages for photoactivated chemotherapy (PACT) represents an excellent opportunity to address the technical drawbacks of conventional photodynamic therapy (PDT) whose oxygen-dependent nature renders it inadequate in certain therapy contexts such as hypoxic tumors. As an alternative to PDT, oxygen free mechanisms to generate cytotoxic reactive oxygen species (ROS) by visible light cleavable photocages are in demand. Here, we report the detailed mechanisms by which the small molecule blebbistatin acts as a one-photon blue light-gated or twophoton near-infrared light-gated photocage to directly release a hydroxyl radical (•OH) in the absence of oxygen. By using femtosecond transient absorption spectroscopy and chemoselective ROS fluorescent probes, we analyze the dynamics and fate of blebbistatin during photolysis under blue light. Waterdependent photochemistry reveals a critical process of water-assisted protonation and excited state intramolecular proton transfer (ESIPT) that drives the formation of short-lived intermediates, which surprisingly culminates in the release of •OH but not superoxide or singlet oxygen from blebbistatin. CASPT2//CASSCF calculations confirm that hydrogen bonding between water and blebbistatin underpins this process. We further determine that blue light enables blebbistatin to induce mitochondria-dependent apoptosis, an attribute conducive to PACT development. Our work demonstrates blebbistatin as a controllable photocage for •OH generation and provides insight into the potential development of novel PACT agents.

Breaking the barrier: an osmium photosensitizer with unprecedented hypoxic phototoxicity for real world photodynamic therapy

“…41,[48][49][50][51][52][53][54] Likewise, relatively few systems have been tested for photodissociation in cell-free conditions under low oxygen conditions (i.e., 0-3%). 37,49,50,52,55 Performing experiments under hypoxic conditions is challenging due to a variety of factors such as the initial establishment of low oxygen tension or differences in cellular growth and metabolismif the cells can even grow at the desired oxygen level. A hypoxia chamber for cell incubation and processing is required to establish and maintain a low oxygen atmosphere, but many light devices do not t inside the chamber and/or result in excessive heating in the chamber.…”

Disentangling Multiple Effects on Excited‐State Intramolecular Charge Transfer among Asymmetrical Tripartite PPI‐TPA/PCz Triads

“…Ultrafasttime-resolved transient absorption spectroscopy has become ap owerful technique to explore ar ange of excited states and CT dynamics of molecules. [39][40][41] By combination of femtosecond/nanosecond transient absorption (fs-TA/ns-TA) spectroscopy and excited-state theoretical calculations, the complete photophysical and photochemical behavior of PPI-TPA/PCz triads was elucidated.…”

“…Herein, compounds in which a PPI unit is coupled with two TPA or PCz moieties to form two kinds of asymmetrical ternary structures were designed and synthesized to explore the nature of the charge transfer (CT) in a series of asymmetrical tripartite PPI–TPA/PCz triads (Scheme 1). Ultrafast time‐resolved transient absorption spectroscopy has become a powerful technique to explore a range of excited states and CT dynamics of molecules [39–41] . By combination of femtosecond/nanosecond transient absorption (fs‐TA/ns‐TA) spectroscopy and excited‐state theoretical calculations, the complete photophysical and photochemical behavior of PPI‐TPA/PCz triads was elucidated.…”

Metalloporphyrin Pd(T4) Exhibits Oncolytic Activity and Cumulative Effects with 5-ALA Photodynamic Treatment against C918 Cells

“…For example, blebbistatin when conditioned with blue light undergoes photoexcitation, resulting in hydroxide radicals and subsequent cytotoxicity, even in hypoxic environments. Although lacking absorption outside the blue spectrum, when irradiated with 800 nm using a two-photon NIR, blebbistatin exhibited similar effects [70]. This display of transition from a one-photon blue light method to a two-photon NIR is a display of development that would unlock the clinical efficacy of blue light photosensitizers.…”