A type i aie photosensitizer based on receptor intensity regulation and a design method thereof

Abstract

The present application belongs to the technical field of theoretical design and computational chemistry of photosensitizers for photodynamic therapy, and discloses a type I AIE photosensitizer based on acceptor intensity regulation and a design method thereof. By introducing acceptor groups with stronger electron-withdrawing ability, the efficiency of intersystem crossing of the photosensitizer molecules can be significantly improved, thereby improving the generation capacity of active oxygen. In the present application, diphenylamine bridged coumarin is used as a fixed electron donor, malonitrile is used as a connecting unit, and nitrobenzene and cationized quinoline are selected as strong electron-withdrawing acceptors to construct new molecular models DPCMN and DPCMQ. The present application is purely theoretically calculated and designed, without chemical synthesis and experimental testing, thereby reducing the research and development cost and shortening the design period. By regulating the electron-withdrawing strength of the acceptor, the efficiency of intersystem crossing of the photosensitizer and the generation capacity of active oxygen can be precisely regulated. The designed DPCMQ molecule has the highest intersystem crossing rate, generates only •OH, and has excellent activity in a low-oxygen environment.

Description

Technical Field

[0001] This invention belongs to the field of theoretical design and computational chemistry technology of photosensitizers for photodynamic therapy, and relates to a type I AIE photosensitizer based on receptor intensity regulation and its design method. Background Technology

[0002] Photosensitizers, as an important class of functional molecules, have broad application prospects in biomedicine, photodynamic therapy, and photocatalysis. When photosensitizers are excited, they transition from the ground state to an excited singlet state. At this point, most of the excited singlet states undergo intersystem crossing to reach the excited triplet state, and then undergo a series of chemical reactions with surrounding oxygen and substrate molecules, generating reactive oxygen species (ROS) that damage the target. Based on the type of ROS generated, photosensitizers can be divided into two categories. Type II photosensitizers are currently the most widely studied; however, they are limited by oxygen concentration, thus affecting therapeutic efficacy. Type I photodynamic therapy (PDT) has a lower oxygen dependence, therefore type I photosensitizers have a significant advantage in the treatment of solid tumors. Aggregation-induced emission (AIE) photosensitizers can overcome the aggregation-induced quenching (ACQ) defect of traditional photosensitizers and have become a research hotspot in the PDT field. Most importantly, AIE photosensitizers based on the type I mechanism generate oxygen-independent ROS such as hydroxyl radicals (•OH) through electron transfer pathways, which can maintain high therapeutic activity even in the hypoxic tumor microenvironment, providing a new strategy for breaking through the bottleneck of traditional PDT technology.

[0003] Current research has successfully synthesized AIE photosensitizers with type I photodynamic properties. The article "Lipid droplet-targeted NIR AIE photosensitizer evoking concurrent ferroptosis and apoptosis" reports four type I AIE photosensitizers synthesized by changing different acceptors in the DA structure: DPCMM, DPCMB, DPCMP, and DPCMC. These four photosensitizer molecules use diphenylamine-bridged coumarin as an electron donor and malononitrile as a fixed acceptor unit, and construct differentiated acceptor units by introducing different electron-withdrawing groups. Although these experimental strategies have made some progress, two core problems remain: first, existing experimental methods are insufficient to quantitatively analyze the influence of molecular structure on the efficiency of type I ROS generation at the microscopic level, such as molecular orbital arrangement and electronic transition pathways; second, there is a lack of systematic theoretical explanation of the photophysical mechanism by which photosensitizers generate reactive oxygen species through electron transfer pathways, resulting in a lack of clear guiding principles for molecular design. Therefore, studying the mechanism of DA-type photosensitizer molecules through theoretical calculations is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing type I AIE photosensitizers, which rely on experimental trial and error, lack systematic theoretical mechanisms, and lack quantitative design strategies, this invention provides a purely theoretical calculation-based method for designing and studying the mechanism of type I AIE photosensitizers based on receptor strength modulation, enabling rational design and precise mechanistic analysis of photosensitizers. Specifically, by introducing acceptor groups with stronger electron-withdrawing capabilities, the efficiency of intersystem crossing in photosensitizer molecules can be significantly improved, thereby enhancing the generation of reactive oxygen species. This invention uses diphenylamine-bridged coumarin as the fixed electron donor and malononitrile as the connecting unit, theoretically screening nitrobenzene and cationic quinoline as strong electron-withdrawing acceptors to construct novel molecular models DPCMN and DPCMQ. This design not only enhances the electron-withdrawing ability of the acceptor but also increases spin-orbit coupling to promote intersystem crossing. Furthermore, by introducing cationic acceptors, the reduction potential of the acceptor can be effectively increased, further enhancing its electron-withdrawing ability. Theoretical calculations show that, compared with DA-type photosensitizers using diphenylamine-bridged coumarin as the donor and cyanobenzene as the acceptor, photosensitizers linking nitrobenzene and cationic quinoline as the acceptor exhibit higher acceptor reduction potentials, smaller singlet and triplet band gaps, larger spin-orbit coupling coefficients, and longer absorption and emission wavelengths. These superior properties indicate that the photosensitizer designed in this invention has greater application potential in photodynamic therapy.

[0005] The technical solution of this invention: A type I AIE photosensitizer based on receptor intensity modulation has the following structure: The structure of R is as follows: .

[0006] A method for designing type I AIE photosensitizers based on receptor intensity modulation, comprising the following steps: Step 1: Use InDraw to draw the type I AIE photosensitizer molecule; Step 2: Using Gaussian 16 software, the M06-2X functional and def2-TZVP basis set were selected to simulate the properties of type I AIE photosensitizer molecules in DMSO under the SMD solvation model. The geometric structure optimization and frequency of the ground state, excited singlet state and excited triplet state of the type I AIE photosensitizer molecule were calculated. Step 3: Confirm that the calculation results obtained in Step 2 have no imaginary frequencies, and confirm that the geometric structures of the ground state, excited singlet state, and excited triplet state of the Type I AIE photosensitizer molecule are the most stable structures; Step 4: Use BDF software to calculate the spin-orbit coupling constant between the excited singlet and excited triplet states of the type I AIE photosensitizer, in order to determine the intersystem crossing channel of the type I AIE photosensitizer; Step 5: After determining the intersystem crossing channel using the spin-orbit coupling constant output in Step 4, obtain the band gap difference between the excited singlet and excited triplet states of the intersystem crossing channel based on the optimization results of the type I AIE photosensitizer molecular structure in Step 2. Step 6: Generate a MOMAP input file using the spin-orbit coupling constant obtained in Step 4 and the band gap difference between the excited singlet and excited triplet states obtained in Step 5. Run the MOMAP input file using MOMAP software. After the calculation is completed, output the rate coefficient of the intersystem crossing channel of the type I AIE photosensitizer molecule. The rate coefficient is proportional to the ability of reactive oxygen species to be generated. Step 7: Perform TD-DFT calculations on the ground state and excited singlet state of the type I AIE photosensitizer molecule to obtain the maximum absorption wavelength and maximum emission wavelength of the type I AIE photosensitizer molecule; Step 8: Calculate the Gibbs free energy change (ΔG) of electron transfer in the type I AIE photosensitizer molecule to generate reactive oxygen species, and verify the thermodynamic feasibility of the ROS generation pathway of the type I AIE photosensitizer molecule; Step 9: Calculate the acceptor reduction potential of the type I AIE photosensitizer molecule using ORCA software. The larger the acceptor reduction potential, the stronger the electron-withdrawing ability. Step 10: Use GROMACS software to perform a 30 ns aqueous solution molecular dynamics simulation of type I AIE photosensitizer molecules to analyze the self-aggregation behavior of type I AIE photosensitizer molecules in aqueous solution; Step 11: Use AutoDock software to perform molecular docking between the type I AIE photosensitizer molecule and the Fas protein, and calculate the binding free energy between the type I AIE photosensitizer molecule and the Fas protein.

[0007] To verify whether the two molecules designed in this invention (named DPCMN and DPCMQ, respectively) possess intersystem crossing capabilities, theoretical calculations were first performed on the photosensitizer molecules DPCMM, DPCMB, DPCMP, and DPCMC from previous literature. By using known photosensitizer molecules capable of generating reactive oxygen species (ROS) as benchmarks, the aim was to highlight that the two molecules proposed in this invention may possess a stronger ROS generation capacity. Evaluating newly designed molecules through theoretical calculations is an effective strategy that can guide subsequent experimental research and accelerate the development and application of novel photosensitizers. This theoretical calculation method allows for a deeper understanding of the photophysical properties of novel photosensitizers, providing important references for their future applications and optimization.

[0008] The beneficial effects of this invention are: (1) Pure theoretical calculation design, without chemical synthesis and experimental testing, reduces R&D costs and shortens the design cycle; (2) By regulating the electron-withdrawing intensity of the acceptor, the intersystem crossing efficiency and reactive oxygen generation capacity of the photosensitizer can be precisely controlled; (3) The designed DPCMQ molecule has the highest intersystem crossing rate, specifically generates •OH, and exhibits excellent activity under low oxygen conditions; (4) Establish a complete multi-scale theoretical calculation system to provide a general method for the rational design of DA-type and I-type AIE photosensitizers. Detailed Implementation

[0009] The specific embodiments of the present invention will be further described below in conjunction with the technical solution.

[0010] DPCMM, DPCMB, DPCMP, and DPCMC from the published article "Lipid droplet-targeted NIR AIE photosensitizer evoking concurrent ferroptosis and apoptosis" were selected as control photosensitizers. These molecules use diphenylamine-bridged coumarin as the donor and methoxybenzene, benzene ring, pyridine, and cyanobenzene as acceptors, respectively. Experiments have confirmed their ability to generate type I ROS, but the acceptor electron-withdrawing ability is weak, resulting in limited ROS generation efficiency. This invention uses these molecules as a benchmark to compare and evaluate the performance advantages of the newly designed DPCMM and DPCMQ molecules, clarifying the core role of acceptor intensity regulation.

[0011] The purpose of performing theoretical calculations against the reference photosensitizer is to obtain comparative theoretical data that will help evaluate the performance of the new molecules DPCMN and DPCMQ. By comparing the theoretical calculation results with those of the reference photosensitizer, the potential advantages of the new molecules in terms of reactive oxygen species generation capacity and photophysical properties can be revealed more clearly. The theoretical calculation data are as follows (details of the calculations are in the specific implementation method): the reduction potentials of the DPCMM, DPCMB, DPCMP, and DPCMC acceptors are -3.436 V, -3.464 V, -2.946 V, and -2.414 V, respectively; the theoretically calculated maximum absorption wavelengths are 413.75 nm, 421.40 nm, 432.25 nm, and 434.47 nm, respectively; and the theoretically calculated maximum emission wavelengths are 552.59 nm, 559.81 nm, 573.77 nm, and 573.64 nm, respectively. The differences between the calculated and experimental values ​​are unavoidable due to theoretical approximations, but their magnitude trend corresponds to the experimental results; the theoretically calculated intersystem crossing rate coefficient is 6.939 × 10⁻⁶. 6 s -1 6.555×10 6 s -1 5.606×10 6 s -1 4.412×10 6 s -1These data do indeed support the design concept of this invention. Subsequent theoretical calculations have verified that DPCMN and DPCMQ have superior photophysical properties, indicating that they are expected to show stronger effects in photodynamic therapy.

[0012] Theoretical calculations show that the acceptor reduction potentials of DPCMN and DPCMQ are -1.661 V and -1.178 V, respectively. A higher acceptor reduction potential indicates a stronger electron-withdrawing ability. These values ​​are all higher than the control photosensitizer, indicating that the acceptor groups in DPCMN and DPCMQ have stronger electron-withdrawing properties than the control photosensitizer.

[0013] Theoretical calculations show that the maximum absorption wavelengths of DPCMN and DPCMQ in the examples are 437.75 nm and 471.96 nm, respectively, both longer than the maximum absorption wavelength of the control photosensitizer. This strongly indicates that DPCMN and DPCMQ have properties that are more conducive to the absorption of light in deep tissues, thereby improving the depth of treatment. The maximum emission wavelengths of DPCMN and DPCMQ in the examples are 577.03 nm and 626.86 nm, respectively, both longer than the maximum emission wavelength of the control photosensitizer. This indicates that DPCMN and DPCMQ help reduce light scattering in tissues, making it easier for the therapeutic light to concentrate within the target tissue, improving efficacy and reducing damage to surrounding normal tissues. The redshift of the maximum absorption and emission wavelengths helps improve the therapeutic effect and safety of photodynamic therapy.

[0014] Theoretical calculations show that the theoretically calculated intersystem crossing rate coefficients for examples DPCMN and DPCMQ are 6.489 × 10⁻⁶. 6 s -1 2.940×10 7 s -1 A higher intersystem crossing rate coefficient favors the formation of the first excited triplet state. Since photosensitizers in the first excited triplet state can undergo electron and energy transfer to generate reactive oxygen species (ROS), a higher intersystem crossing rate coefficient further favors ROS formation. In the examples DPCMN and DPCMQ, the intersystem crossing rate coefficient of DPCMQ was significantly higher than that of the control photosensitizer, indicating that DPCMQ has a stronger intersystem crossing ability and is expected to generate more ROS.

[0015] Thermodynamic calculations for reactive oxygen species (ROS) generation: The Gibbs free energy change (ΔG) for ROS generation from the excited state of the photosensitizer was calculated. The ΔG for the generation of •OH by control molecules DPCMM, DPCMB, DPCMP, and DPCMC were -213.590 kJ / mol, -215.992 kJ / mol, -220.618 kJ / mol, and -222.154 kJ / mol, respectively, resulting in the generation of O2.•- The ΔG values ​​of both molecules are less than 0, indicating that they can co-generate two types of ROS. The ΔG values ​​of the new molecules DPCMN and DPCMQ for generating •OH are -236.495 kJ / mol and -238.571 kJ / mol, respectively, both less than 0, indicating thermodynamic spontaneity and the generation of O2. •- The ΔG values ​​were 16.517 kJ / mol and 41.874 kJ / mol, respectively, both greater than 0, indicating that spontaneous generation of •OH was not possible. The specific generation of •OH was achieved, and the higher the acceptor strength, the stronger the spontaneous tendency of •OH generation.

[0016] Aggregation Behavior Molecular Dynamics Simulation: All six molecules spontaneously formed stable aggregates in the aqueous phase, exhibiting typical AIE characteristics. Statistical analysis of intermolecular center distances showed that the average aggregation distances of DPCMM, DPCMB, DPCMP, DPCMC, DPCCMN, and DPCMQ were 2.9 Å, 3.5 Å, 3.5 Å, 3.9 Å, 4.6 Å, and 5.8 Å, respectively. DPCMQ had the largest aggregation distance, effectively suppressing π-π stacking and further avoiding the ACQ effect. Calculations of the radial distribution function and coordination number of water molecules showed that the 1 nm sphere around DPCMQ contained the most water molecules, which could fully participate in the •OH generation reaction, improving ROS generation efficiency.

[0017] Molecular docking calculations: The binding free energies of the six photosensitizers (Fas) to tumor apoptosis proteins were -7.65 kcal / mol, -7.5 kcal / mol, -7.62 kcal / mol, -7.96 kcal / mol, -8.39 kcal / mol, and -8.19 kcal / mol, respectively. All molecules had binding free energies below -6 kcal / mol, demonstrating excellent protein binding ability. DPCMN and DPCMQ showed higher binding free energies than the control photosensitizer, indicating their effective targeting of tumor cells to exert photodynamic effects. By modifying the receptor structure in DPCMN and DPCMQ in the examples, their electron-withdrawing ability was adjusted, thereby achieving precise regulation of the intersystem crossing process. This design concept is highly consistent with the results of this invention, highlighting that fine-tuning the photosensitizer structure can significantly affect its photodynamic therapy efficacy. This strategy provides a new approach for developing more effective photosensitizers and is expected to achieve better application results in the field of photodynamic therapy.

Claims

1. A type I AIE photosensitizer based on receptor intensity modulation, characterized in that, The structure of this type I AIE photosensitizer is as follows: The structure of R is as follows: 。 2. A method for designing type I AIE photosensitizers based on receptor intensity modulation, characterized in that, The steps are as follows: Step 1: Use InDraw to draw the type I AIE photosensitizer molecule; Step 2: Using Gaussian 16 software, the M06-2X functional and def2-TZVP basis set were selected to simulate the properties of type I AIE photosensitizer molecules in DMSO under the SMD solvation model. The geometric structure optimization and frequency of the ground state, excited singlet state and excited triplet state of the type I AIE photosensitizer molecule were calculated. Step 3: Confirm that the calculation results obtained in Step 2 have no imaginary frequencies, and confirm that the geometric structures of the ground state, excited singlet state, and excited triplet state of the Type I AIE photosensitizer molecule are the most stable structures; Step 4: Use BDF software to calculate the spin-orbit coupling constant between the excited singlet and excited triplet states of the type I AIE photosensitizer, in order to determine the intersystem crossing channel of the type I AIE photosensitizer; Step 5: After determining the intersystem crossing channel using the spin-orbit coupling constant output in Step 4, obtain the band gap difference between the excited singlet and excited triplet states of the intersystem crossing channel based on the optimization results of the type I AIE photosensitizer molecular structure in Step 2. Step 6: Generate a MOMAP input file using the spin-orbit coupling constant obtained in Step 4 and the band gap difference between the excited singlet and excited triplet states obtained in Step 5. Run the MOMAP input file using MOMAP software. After the calculation is completed, output the rate coefficient of the intersystem crossing channel of the type I AIE photosensitizer molecule. The rate coefficient is proportional to the ability of reactive oxygen species to be generated. Step 7: Perform TD-DFT calculations on the ground state and excited singlet state of the type I AIE photosensitizer molecule to obtain the maximum absorption wavelength and maximum emission wavelength of the type I AIE photosensitizer molecule; Step 8: Calculate the Gibbs free energy change of electron transfer in the type I AIE photosensitizer molecule to generate reactive oxygen species, and verify the thermodynamic feasibility of the ROS generation pathway of the type I AIE photosensitizer molecule; Step 9: Calculate the acceptor reduction potential of the type I AIE photosensitizer molecule using ORCA software. The larger the acceptor reduction potential, the stronger the electron-withdrawing ability. Step 10: Use GROMACS software to perform molecular dynamics simulation of type I AIE photosensitizer molecules in aqueous solution for 30 ns, and analyze the self-aggregation behavior of type I AIE photosensitizer molecules in aqueous solution for 30 ns. Step 11: Use AutoDock software to perform molecular docking between the type I AIE photosensitizer molecule and the Fas protein, and calculate the binding free energy between the type I AIE photosensitizer molecule and the Fas protein.

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