Photophysical Exploration of Zn(II) Polypyridine Photosensitizers in Two-Photon Photodynamic Therapy: Insights from Theory

Abstract

The high incidence and difficulties of treatment of cancer have always been a challenge for mankind. Two-photon photodynamic therapy (TP-PDT) as a less invasive technique provides a new perspective for tumor treatment due to its low-energy near-infrared excitation, high targeting, and minor damage. At present, the emerging metal complexes used as the photosensitizers (PSs) in TP-PDT have aroused great interest. However, most metal complexes as PSs in TP-PDT still face some problems, such as slow clearance, unsatisfactory two-photon absorption (TPA) characteristics, high price, low reactivity, and poor solubility. In this work, density functional theory and time-dependent density functional theory were used to characterize the one/two-photon response, solvation free energy, and lipophilicity of a series of novel PSs applied in TP-PDT. The results suggest that based on complex 1, replacing Ru(II) center with Zn(II) (complex 2) can effectively prolong the triplet excited state lifetime while reducing the cost and environmental pollution, and the azetidine heterospirocycles were introduced into the ligand scaffold (complex 3), which effectively reduced the vibration relaxation of the ligand group and improved the water solubility; further, the addition of acetylenyl groups subtly enhanced the light absorption and significantly improved the two-photon response (complex 4). In addition, all complexes met the requirement of a PS and could be used as potential candidates for TP-PDT. In particular, complex 4 has the advantages of high solvation free energy, a large TPA cross-section (1413 GM), a long triplet state lifetime (671 μs), good chemical reactivity, and low cost, and it is easy to be scavenged by organisms. Overall, this contribution may provide an important clue to formulate clear design principles for type I/II PSs and rational design of PSs with high intersystem crossing rates, a long lifetime, and therapeutic excitation wavelengths.

Design of Sonosensitizers Integrated with Resveratrol Motif for Synergetic Sonodynamic Therapy and Nuclear Factor Kappa B Transcription Suppression of Breast Cancer

“…The electron excitation of the compounds showed a poor overlapping between the electron and hole, indicating a typical charge transfer characteristic (Figure S3). The calculated oscillator strength ( f ) also proved that TR2 and TR3 were more easily excited to S 1 than TR1 . These calculations showed that the f and Δ E ST of TR2 and TR3 were close in values, which could explain their similar 1 O 2 production under ultrasonic treatment.…”

“…28 The calculated oscillator strength (f) also proved that TR2 and TR3 were more easily excited to S 1 than TR1. 29 These calculations showed that the f and ΔE ST of TR2 and TR3 were close in values, which could explain their similar 1 O 2 production under ultrasonic treatment.…”

The effect of heteroatoms at end groups of anthracene derivatives on the photoelectric properties and crystal/film morphology: a theoretical perspective

“…k r and k nr are the radiative decay rate and nonradiative decay internal conversion rate from S 1 to the ground state (S 0 ), respectively. The formulas are expressed as follows: 57 k r = fDE fi 2 /1.499 (12)…”

Design, Synthesis and Evaluation of Fluorescent Properties of Benzothiazole Derivatives

“…However, some reported small molecular fluorescent compounds exhibited low tissue penetration or spatial resolution, which had a limitation for their further bioimaging applications [16–18] . Furthermore, some potential fluorescent compounds, which were investigated by systemic theoretical investigation, need to be synthesized to verify the excellent optical properties [19–20] . Therefore, it is urged to develop more novel small molecular fluorescence compounds for various bioimaging applications by theoretical and experimental methods.…”

“…[16][17][18] Furthermore, some potential fluorescent compounds, which were investigated by systemic theoretical investigation, need to be synthesized to verify the excellent optical properties. [19][20] Therefore, it is urged to develop more novel small molecular fluorescence compounds for various bioimaging applications by theoretical and experimental methods.…”