We developed a pH dependent amino heptamethine cyanine based theranostic probe (I2-IR783-Mpip) that can be activated by near infrared light. I2-IR783-Mpip, in acidic condition, exhibited an intense, broad NIR absorption band (820–950 nm) with high singlet oxygen generation upon exposure to NIR light (~850 nm). Theoretical calculations showed that the protonation of the probe in an acidic environment decreased the molecular orbital energy gaps and increased the intramolecular charge transfer efficiency. I2-IR783-Mpip exhibited good photodynamic efficiency towards liver hepatocellular carcinoma cells under physiological and slightly acidic conditions while normal human embryonic kidney cells remained alive under the same conditions. Detection of intracellular reactive oxygen species (ROS) in cells treated with I2-IR783-Mpip after NIR light exposure confirmed PDT efficiency of the probe in acidic environment. Moreover, I2-IR783-Mpip also demonstrated efficient phototoxicity under deep-seated tumour cell system. We believed this is the first PDT agent that possesses intrinsic tumour binding and selectively eradicate tumour in acidic environment under 850 nm NIR lamp.
The mechanisms of the photodissociation of single isolated methanol (CH3OH) molecules in the lowest singlet-excited (S1) state were systematically studied using the complete active-space second-order perturbation theory (CASPT2) and transition state theory (TST). This theoretical study focused on the nonradiative relaxation processes that transform the S0 → S1 vertically excited molecule to the products in their respective electronic ground states. The results confirmed that O–H dissociation is the predominant exothermic process and that the formation of formaldehyde (CH2O), in which the O–H dissociated species are the precursors for the reaction in the S0 state, is the second most favorable process. For C–O dissociation, the theoretical results suggested a thermally excited precursor in a different Franck–Condon region in the S0 state, from which vertical excitation leads to a transition structure in the S1 state and spontaneously to the [CH3]· and [OH]· products in their electronic ground states. The CASPT2 and TST results also revealed the possibility of [CH3OH] → [CH2OH2] isomerization dissociation, in which another thermally excited precursor is vertically excited, and C–O dissociation and intermolecular proton transfer lead to the singlet and triplet [CH2]–[H2O] H-bond complexes in their electronic ground states. Although sufficient thermal energy to generate the precursors in the S0 state is available and the reactions are kinetically feasible at high temperatures, the strongly kinetically controlled O–H dissociation predominates the C–O and [CH3OH] → [CH2OH2] isomerization dissociations. The present results verified and confirmed the reported theoretical and experimental findings and provided insights into the thermal selectivity and interplay between thermal excitation and photoexcitation.
The dynamics and mechanism of proton exchange in phosphonic acid-functionalized polymers were studied using poly(vinyl-phosphonic acid) (PVPA) as a model system along with quantum chemical calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations at the B3LYP/TZVP level as model calculations. This theoretical study began with searching for the smallest, most active polymer segments and their intermediate conformations which could be involved in the local proton-exchange process. The B3LYP/TZVP results confirmed that a low local dielectric environment and excess proton conditions are required to generate the intermediate conformations, and the shapes of the potential energy curves of the proton exchange between the two phosphonic acid functional groups are sensitive to the local conformational changes. In contrast, a high local dielectric environment increases the energy barriers, thereby preventing the proton from returning to the original functional group. Based on the static results, a mechanism for the proton exchange between the two functional groups involving fluctuations in the local dielectric environment and a local conformational change was proposed. The BOMD results confirmed the proposed mechanism by showing that the activation energies for the proton exchange in the hydrogen bond between two immobilized phosphonic acid moieties, obtained from the exponential relaxation behaviors of the envelopes of the velocity autocorrelation functions and the 1 H Nuclear Magnetic Resonance (NMR) line-shape analyses, are too low to be the ratedetermining process. Instead, coupled librational motion in the backbone which leads to the interconversion between the two intermediate conformations possesses higher activation energy, and therefore represents one of the most important rate-determining processes. These findings suggested that the rate of the proton exchange in the model phosphonic acidfunctionalized polymer is determined by the polymer mobility which, in this case, is the large-amplitude librational motion of the vinyl backbone.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.