Singlet Oxygen Yield Research Articles

Fabrication of Carbon Dots with Singlet Oxygen Generation and Their Potential Photodynamic Therapy Applications.

Due to the unique chemical and biomedical properties of carbon dots (CDs), they have increasingly obtained the attention in many research fields, for example, bioimaging, fluorescence sensing, and drug delivery, etc. Recently, it was found that, under light excitation, CDs can also be exploited as a novel photosensitizer to prepare reactive oxygen species (ROS), which expand their applications in the field of photodynamic therapy for cancer treatment. Nevertheless, the high cost and complex fabrication approach of CDs significantly limit their applications. To address this issue, bottom-up routes usually utilize sustainable and inexpensive carbon precursor as starting materials, employed N,N-dimethylformamide (DMF) or ethanol as an environmental-friendly solvent. Bottom-up approach was energy efficient, and the purification process was relatively simple by dialysis. Therefore, carbon dots (CDs) were facilely fabricated in a one-pot solvothermal process using 1-aminoanthraquinone as a precursor, and their application as photosensitizers for in vitro antitumor cells, especially photodynamic therapy (PDT) was established. Then the photophysical and nanoscale dimensions properties of the fabricated CDs were characterized via TEM, UV-visible, fluorescence, and FT-IR spectroscopy. The synthesized N-doped CDs can easily dissolve in water, possess very low biotoxicity, yellow-light emission (maximum peak at 587nm). More importantly, PDT studies demonstrated that the obtained CDs possess a high singlet oxygen yield of 35%, and exhibit significant phototoxicity to cancer cells upon 635nm laser irradiation. These studies highlight that N-doped CDs can be facilely synthesized from only one precursor, and are a potentially novel theranostic agent for in vivo PDT.

Anticancer photodynamic activities of triphenylphosphine-labelled phthalocyanines and their bovine serum albumin-gold nanoparticles- complexes on melanoma A375 cell lines in vitro

This work reports on the synthesis of triphenylphosphine-labelled cationic phthalocyanines (Pc) complexed with bovine serum albumin (BSA) and gold nanoparticles (Au NPs). This nano-complex (Pc-BSA-Au) is studied for its photodynamic therapy (PDT) activity compared to the non-complexed Pc counterpart. The photochemical properties and in vitro PDT efficacies of the Pc and the nano-complex were determined and are compared herein. The singlet oxygen (1O2) yields of the Pcs were determined and are reported in DMF. A singlet oxygen quantum yield of 0.47 was obtained for the Pcs. The PDT efficacies of the complexes were thereafter determined using malignant melanoma A375 cancer cell line in vitro. An increase in the cell toxicity was observed for cells treated with Pc-BSA-Au compared to those treated with the Pc alone. The cell survival percentages were 23.1% for cells treated with Pc-BSA-Au and 48.7% for those treated with Pc alone under PDT treatments.

Potential of Ruthenium as a photosensitizer in radiation-activated Photodynamic Therapy (radioPDT)

In Photodynamic Therapy (PDT), light is used to activate photosensitizers (PS) to generate reactive oxygen species (ROS) as a cell-killing mechanism. However, PDT's application is limited to the surface and small size tumors because of the inefficiency of light in penetrating larger and deep-seated tumors. We have developed novel nanoparticles (NPs) that can be activated by radiation, a process known as the radiation-activated PDT (radioPDT). In our studies we developed a new variant of pegylated poly-lactic-co-glycolic (PEG-PLGA) encapsulated nanoscintillators (NSC) and ruthenium-based photosensitizer (Ru/rPDT) that exhibits minimal cell toxicity while having significant cell killing effect upon radiation activation. Our data suggest that radioPDT with Ru/rPDT can be a more effective strategy than previous protoporphyrin-based iterations in treating many deep-seated tumors.Introduction and Background: Toxicity and normal tissue damage are limiting factors for the application of radiotherapy (RT) where higher doses of radiation is required to cure deep-seated tumor such as prostate cancer. In Photodynamic Therapy (PDT), photosensitizers (PS) are activated by light to generate reactive oxygen species (ROS) to kill tumor cells. However, the main limitation of the current PDT is the limited tissue penetration of PS-activating light. Thus, PDT cannot be effectively used to treat deep-seated and larger size tumors. RT has higher tissue penetration depth, making the radiation-activated PDT (radioPDT) advantageous in treating deep seated tumors.We aim to develop novel radioPDT nanoparticles (NP) with more efficient anti-cancer therapeutic effect in vitro and in vivo to enhance targeted radiotherapy.Methods: LaF3:Ce3+ nanoscintillators (NSCs) were synthesized in a single step wet chemistry technique. The NSCs along with Ruthenium-based PS (Ru) with matching excitation/emission spectra were successfully encapsulated in PEG-PLGA. UV-Vis spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) were used to confirm the presence of NSCs and Ru, and dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine the size of NP. Singlet oxygen generation was measured by Singlet Oxygen Sensor Green (SOSG) and direct singlet oxygen fluorescence. RadioPDT therapeutic potential was evaluated in PC3 prostate cancer cell under radiation by Alamar Blue cell viability assay.Results: UV-Vis spectrometry and ICP-MS determined the successful PEG-PLGA encapsulation of NSC and Ru. The TEM imaging confirmed the encapsulation NSC inside the nanocarrier PEG-PLGA. TEM and DLS measurements showed the size of radioNP ranged from 90nm to 150nm with polydispersity index of <0.3. Singlet oxygen generation by Ru/rPDT NPs was greater than PPIX based radioPDT (PPIX/rPDT) NPs. Furthermore, the direct measurement of singlet oxygen generation with fluorescence spectroscopy of Ru/rPDT showed preserved singlet oxygen yield and no evidence of quenching. The Ru/rPDT and PPIX/rPDT showed minimal PC3 cell cytotoxicity in dark conditions. The PC3 cell killing efficiency was comparable between Ru/rPDT and PPIX/rPDT either under light or radiation activation.Conclusion: Our in vitro studies show Ru/rPDT significantly increases anti-cancer therapeutic effect of RT, with minimal toxicity. Future studies will refine in vivo NP biodistribution, dosing, and RT dose/fractionation schemes.

Design of AsLOV2 domain as a carrier of light-induced dissociable FMN photosensitizer.

Flavin mononucleotide (FMN) is a highly efficient photosensitizer (PS) yielding singlet oxygen (1 O2 ). However, its 1 O2 production efficiency significantly decreases upon isoalloxazine ring encapsulation into the protein matrix in genetically encoded photosensitizers (GEPS). Reducing isoalloxazine ring interactions with surrounding amino acids by protein engineering may increase 1 O2 production efficiency GEPS, but at the same time weakened native FMN-protein interactions may cause undesirable FMN dissociation. Here, in contrast, we intentionally induce the FMN release by light-triggered sulfur oxidation of strategically placed cysteines (oxidation-prone amino acids) in the isoalloxazine-binding site due to significantly increased volume of the cysteinyl side residue(s). As a proof of concept, in three variants of the LOV2 domain of Avena sativa (AsLOV2), namely V416C, T418C, and V416C/T418C, the effective 1 O2 production strongly correlated with the efficiency of irradiation-induced FMN dissociation (wild type (WT) < V416C < T418C < V416C/T418C). This alternative approach enables us: (i) to overcome the low 1 O2 production efficiency of flavin-based GEPSs without affecting native isoalloxazine ring-protein interactions and (ii) to utilize AsLOV2, due to its inherent binding propensity to FMN, as a PS vehicle, which is released at a target by light irradiation.

γ-glutamyl transpeptidase activatable NIR photosensitizer for visualization and selective killing of liver cancer cells

Photodynamic therapy (PDT) is a treatment model that involves using light sources to excite photosensitizers (PSs), generating reactive oxygen species. This method is considered a potential treatment for tumors. However, the non-selective toxicity of traditional PSs to both tumors and normal tissues hinders the advancement of PDT. This lack of selectivity is a major obstacle in the development of effective PDT. The activatable PS can only function in a specific environment, which enhances the selectivity and safety of PDT. In this paper, we focus on GGT (γ-glutamyltranspeptidase) overexpressed in liver cancer as the biological target. We designed and synthesized the activatable PS BrCy-Glu by modifying the substrate of GGT (l-glutamic acid) onto the brominated hemicyanine PS (BrCy-OH). The intramolecular charge transfer (ICT) effect of BrCy-Glu is inhibited, which leads to low fluorescence quantum yield and singlet oxygen yield. However, in the presence of GGT, it can undergo selective hydrolysis and be converted into BrCy-OH through a series of elimination reactions. This process is accompanied by a significant increase in fluorescence quantum yield and singlet oxygen yield. In vitro studies demonstrate that BrCy-Glu is suitable for precise fluorescence identification of liver cancer and selective eradication of cancer cells under light conditions.

Novel naphthalimide bridged zinc porphyrin/BODIPY nanomaterials with D-A structure for photodynamic therapy

As a non-invasive cancer therapy method, photodynamic therapy (PDT) shows tremendous promise in clinical cancer treatment. Light-activated singlet oxygen production of photosensitizers (PSs) is the prerequisite for cancer PDT, and the use of organic photosensitizers is always limited by visible light-based activation, hydrophilicity, biocompatibility, selectivity and quantum yield of singlet oxygen. Currently, both zinc porphyrin- and BODIPY-based structures have been widely used in the development of PDT PSs. Here, we developed a novel naphthalimide bridged zinc porphyrin/BODIPY molecule (Por-BDP-1) with two poly(ethylene glycol) (PEG) chains, in which D-A structure was constructed between the naphthalimide group and porphyrin group. After self-assembly into nanoparticles, Por-BDP-1 NPs (Diameter: 122.4 nm) could quench fluorescence in 600–700 nm, bind with calf thymus-DNA, and produce singlet oxygen during light-irradiation (laser: 680 nm, 1.0 W/cm[Formula: see text]. In addition, Por-BDP-1 NPs effectively killed HeLa cells with a IC[Formula: see text] value = 44.8 μg/mL and showed a lower dark toxicity under the same conditions. All our results demonstrated that our naphthalimide bridged zinc porphyrin/BODIPY nano-photosensitizer is a promising nanoagent for PDT in the clinic.

Photothermal/photodynamic antibacterial hydrogel embedded with copper carbon dots and Au nanoparticles

In this paper, we created a hydrogel (named AuNPs-CuCCDs@Gel) with photothermal and photodynamic performance through incorporating copper carbon dots (CuCCDs) and Au nanoparticles (AuNPs) into gelatin and chitosan hydrogels. The thus-obtained hydrogel exhibited a high photothermal and photodynamic antibacterial activity with a superior singlet oxygen yield (0.70), which was better than that of methylene blue (0.52). After laser irradiation at 808 nm for 6 min, the temperature of AuNPs-CuCCDs@Gel rose from room temperature to 50 °C, which manifested good effects for avoiding local heat damage and protecting normal cells. AuNPs-CuCCDs@Gel exhibited the highest antibacterial efficacy of 96.46% and 97.48% against S. aureus and E. coli respectively. The significantly improved bactericidal performance was attributed to the synergistic effects of hyperthermia and reactive oxygen species (ROS). This work suggests that photothermal/photodynamic antibacterial hydrogel is a promising agent for treating wound infection.

Photogeneration and quenching of singlet molecular oxygen by bacterial C40 carotenoids with long chain of conjugated double bonds.

Measurement of photosensitized luminescence of singlet oxygen has been applied to studies of singlet oxygen generation and quenching by C40 carotenoids (neurosporene, lycopene, rhodopin, and spirilloxanthin) with long chain of conjugated double bonds (CDB) using hexafluorobenzene as a solvent. It has been found that neurosporene, lycopene, and rhodopin are capable of the low efficient singlet oxygen generation in aerated solutions upon photoexcitation in the spectral region of their main absorption maxima. The quantum yield of this process was estimated to be (1.5-3.0) × 10-2. This value is near the singlet oxygen yields in solutions of ζ-carotene (7 CDB) and phytoene (3 CDB) and many-fold smaller than in solutions of phytofluene (5 CDB) (Ashikhmin et al. Biochemistry (Mosc) 85:773-780, https://doi.org/10.1134/S0006297920070056 , 2020, Biochemistry (Mosc) 87:1169-1178, 2022, https://doi.org/10.1134/S00062979221001082022 ). Photogeneration of singlet oxygen was not observed in spirilloxanthin solutions. A correlation was found between the singlet oxygen yields and the quantum yields and lifetimes of the fluorescence of the carotenoid molecules. All carotenoids were shown to be strong physical quenchers of singlet oxygen. The rate constants of 1O2 quenching by the carotenoids with long chain of CDB (9-13) were close to the rate constant of the diffusion-limited reactions ≈1010M-1s-1, being many-fold greater than the rate constants of 1O2 quenching by the carotenoids with the short chain of CDB (3-7) phytoene, phytofluene, and ζ-carotene studied in prior papers of our group (Ashikhmin et al. 2020, 2022). To our knowledge, the quenching rate constants of rhodopin and spirilloxanthin have been obtained in this paper for the first time. The mechanisms of 1O2 photogeneration by carotenoids in solution and in the LH2 complexes of photosynthetic cells, as well as the efficiencies of their protective action are discussed.

Alternative cancer therapy through modeling pteridines photosensitizer quantum yield singlet oxygen production using swarm-based support vector regression and extreme learning machine

Alternative cancer therapy through modeling pteridines photosensitizer quantum yield singlet oxygen production using swarm-based support vector regression and extreme learning machine

Water-soluble red fluorescent protein dimers for hypoxic two-photon photodynamic therapy.

In this study, two water-soluble red fluorescent protein (RFP) dimers, FP2R' and FP2R'', were synthesized by linking two phenothiazine-based RFP chromophore analogues through alkyl chains or alkoxy chains for hypoxic two-photon photodynamic therapy. RFP dimers are heavy-atom-free two-photon photosensitizers in which the intersystem crossing process is boosted by S and N heteroatoms. In terms of the aqueous solubility, the saturation concentration of FP2R'' was 3.5 mM, the emission wavelength was 677 nm, the singlet oxygen yield was 18%, and the two-photon absorption coefficient (β) was 2.1 × 10-11 cm W-1. Further, the RFP dimer FP2R'' showed excellent biocompatibility, negligible dark toxicity, and could produce 1O2 and O2˙- simultaneously. Under 460 nm illumination, the photosensitizer FP2R'' showed high phototoxicity with an IC50 value of 4.08 μM in an hypoxia environment, indicating that the photosensitizer FP2R'' has an excellent anti-hypoxia ability. In addition, the photosensitizer FP2R'' demonstrated a precise localization ability to lysosomes and its Pearson's colocalization coefficient was 0.94, which could guide the aggregation of photosensitizers in the lysosomes of tumor cells to effectively improve its photodynamic therapy (PDT) effect. In particular, when exposed to 800 nm two-photon excitation, FP2R'' effectively produced 1O2 and O2˙- in zebrafish and exhibited a bright two-photon fluorescence imaging capability. At the same time, the efficacy of two-photon photodynamic therapy mediated by the photosensitizer FP2R'' was verified in the tumor zebrafish model, and the growth of tumor cells in zebrafish was significantly inhibited under a two-photon laser irradiation. The water-soluble two-photon photosensitizer FP2R'' that was reasonably constructed in this study can be used as a high-efficiency hypoxic two-photon photosensitizer to inhibit deep tumor tissues.

Near-infrared BODIPY photosensitizers for two-photon excited singlet oxygen generation and tumor cell photodynamic therapy.

In this paper, two near-infrared BODIPY photosensitizers, Id-BDPI and Cz-BDPI, were obtained by modifying the indole and carbazole aromatic heterocycles in the core of BODIPY. The maximum absorption wavelengths of Id-BDPI and Cz-BDPI were 694 nm and 722 nm, and their singlet oxygen yields were 48% and 48.4%, respectively. In the simulated tumor cell photodynamic therapy, Id-BDPI and Cz-BDPI could effectively inhibit the growth of A549 tumor cells under near-infrared light. Meanwhile, the lysosomal co-localization coefficients of Id-BDPI and Cz-BDPI with A549 tumor cells were 0.94 and 0.89, respectively, showing high lysosomal targeting ability and biocompatibility. The two-photon absorption cross sections measured at 1050 nm by the Z-scanning method were 661.8 GM and 715.6 GM, respectively, and Cz-BDPI was further successfully applied to two-photon fluorescence imaging and two-photon excited singlet oxygen generation in zebrafish. The above results indicate that the introduction of aromatic heterocycles can effectively enhance the photodynamic efficacy of BODIPY photosensitizers, and the larger two-photon absorption cross section also brings potential for two-photon photodynamic therapy applications.

NIR light-triggered photodynamic antibacterial nanofiber membrane based on polycaprolactone and phthalocyanine derivative for biomedical applications.

Photodynamic therapy (PDT) is gaining recognition as a promising alternative method for the treatment of diverse biomedical applications. Toward this goal, we report herein the fabrication of an electrospun membrane utilizing polycaprolactone (PCL), and a phthalocyanine derivative, namely 1,4,8,11,15,22,25-octabutyloxy-29H,31-phthalocyanine (OBuPc). The designed OBuPc-PCL membrane aims to function as a dressing with the potential to facilitate the management of wound healing. The absorption and fluorescence studies of OBuPc have been examined by the steady-state and time-resolved absorption and fluorescence techniques. From direct detection of the weak emission of the singlet oxygen in the NIR region (at 1270 nm), the quantum yield of singlet oxygen was determined to be 0.05. The physiochemical properties of the nanofibers and membranes that were prepared were determined. The photo-activity of all the modified PCL nanofibers against Gram-positive S. aureus and Gram-negative E. coli was observed. The PCL/4.8 OBuPc nanofiber exhibited the highest effectiveness, primarily attributed to the enhanced effect of photosensitizer OBuPc as its concentration increased within the fibre. This resulted in S. aureus bacterial inhibition% of 62.5% ± 0.38 and 78.5% ± 0.49 after exposure to near infrared emission NIR at 630 nm for 15 minutes and 30 minutes, respectively. The inhibition of E. coli bacteria was observed to be 51.51% ± 0.49 and 62.44% ± 0.12% after exposure to near infrared (NIR) emission at a wavelength of 630 nm for durations of 15 minutes and 30 minutes, respectively. Additionally, it was observed that the membranes displayed dark bacterial inhibition. These unique features of the examined nanofibers render them a potential photodynamic antibacterial nanofiber membrane for efficient wound healing treatment and practical antibacterial uses.

Synthesis, photo-physicochemical and biological properties of novel tetrahydropyrimidone-substituted metallo-phthalocyanines.

In this study, new peripherally substituted symmetric zinc and magnesium phthalocyanines (4 and 5) were successfully prepared by cyclotetramerization of the tetrahydropyrimidone (THPM)-linked phthalonitrile 3. The identity of the compounds were confirmed primarily through spectroscopic analysis including NMR, FT-IR, UV-Vis and MALDI-TOF mass spectroscopy. The photophysical and photochemical properties of the synthesized phthalocyanines (Pcs) were examined using UV-Vis absorption and fluorescence emission spectroscopy techniques. The quantum yields of singlet oxygen were found to be 0.50 and 0.33 for compounds 4 and 5 in DMSO, respectively. In addition to photo-physicochemical properties, the enhanced biological activities of compounds 4 and 5 were investigated using a range of biological assays, namely, antibiofilm, microbial cell viability, antioxidant, DNA cleavage, antimicrobial and photodynamic antimicrobial assays. The maximum DPPH inhibition of 4 and 5 was detected as 40.46% and 25.76% at 100 mg L-1, respectively. Fragmentation of the DNA molecule was observed at concentrations of 25 mg L-1, 50 mg L-1 and 100 mg L-1 for 4 and 5. Additionally, effective inhibition of microbial cell viability was observed with the targeted Pcs. The antibiofilm properties of these compounds were found to be concentration-dependent. The biofilm inhibition activities of 4 and 5 were found to be 96.01% and 92.04% for S. aureus, while they were 95.42% and 91.27%, for P. aeruginosa, respectively. The antimicrobial activities of 4 and 5 on different microorganisms were evaluated using the microdilution assay. In the case of photodynamic antimicrobial treatment, the newly synthesized Pcs showed more effective antimicrobial inhibition compared to the control. These findings suggest that compounds 4 and 5 can be used as promising photodynamic antimicrobial agents for the treatment of many diseases, particularly infectious diseases.

Lysosome-targeted Aza-BODIPY photosensitizers for anti-cancer photodynamic therapy

Developing effective near-infrared (NIR) photosensitizers (PSs) has been an attractive goal of photodynamic therapy (PDT) for cancer treatment. In this study, we synthesized N, N-diethylaminomethylphenyl-containing Aza-BODIPY photosensitizers and comprehensively investigated their photophysical/photochemical properties, as well as cell-based and animal-based anti-tumor studies. Among them, BDP 1 has strong NIR absorption at 680 nm and higher singlet oxygen yield in PBS which showed favorable pH-activatable and lysosome-targeting ability. BDP 1 could be easily taken up by tumor cells and showed negligible dark activity (IC50 > 50 μM), however strong phototoxicity upon exposure to light irradiation. The acceptable fluorescence emission from BDP 1 allowed convenient in vivo fluorescence imaging for organ distribution studies in mice. After PDT treatment with upon single time PDT treatment at the beginning using relatively low light dose (54 J/ cm2), BDP 1 (2 mg/kg, 0.1 mL) was found to have strong efficacy to inhibit tumor growth and even to ablate off tumor without causing body weight loss. Therefore, pH-activatable and lysosome-targeted PS may become an effective way to develop potent PDT agent.

Near-Infrared-II-Activatable Self-Assembled Manganese Porphyrin-Gold Heterostructures for Photoacoustic Imaging-Guided Sonodynamic-Augmented Photothermal/Photodynamic Therapy.

Porphyrins and their derivatives are widely used as photosensitizers and sonosensitizers in tumor treatment. Nevertheless, their poor water solubility and low chemical stability reduce their singlet oxygen (1O2) yield and, consequently, their photodynamic therapy (PDT) and sonodynamic therapy (SDT) efficiency. Although strategies for porphyrin molecule assembly have been developed to augment 1O2 generation, there is scope for further improving PDT and SDT efficiencies. Herein, we synthesized ordered manganese porphyrin (SM) nanoparticles with well-defined self-assembled metalloporphyrin networks that enabled efficient energy transfer for enhanced photocatalytic and sonocatalytic activity in 1O2 production. Subsequently, Au nanoparticles were grown in situ on the SM surface by anchoring the terminal alkynyl of porphyrin to form plasmonic SMA heterostructures, which showed the excellent near-infrared-II (NIR-II) region absorption and photothermal properties, and facilitated electron-hole pair separation and transfer. With the modification of hyaluronic acid (HA), SMAH heterostructure nanocomposites exhibited good water solubility and were actively targeted to cancer cells. Under NIR-II light and ultrasound (US) irradiation, the SMAH generates hyperthermia, and a large amount of 1O2, inducing cancer cell damage. Both in vitro and in vivo studies confirmed that the SMAH nanocomposites effectively suppressed tumor growth by decreasing GSH levels in SDT-augmented PDT/PTT. Moreover, by utilizing the strong absorption in the NIR-II window, SMAH nanocomposites can achieve NIR-II photoacoustic imaging-guided combined cancer treatment. This work provides a paradigm for enhancing the 1O2 yield of metalloporphyrins to improve the synergistic therapeutic effect of SDT/PDT/PTT.

Insight into enhanced photogeneration mechanism of reactive intermediates from dissolved black carbon by co-pyrolysis of plastics and biomass

The dissolved black carbon (DBC) derived from co-pyrolysis of plastic and biomass be released into aquatic environment. DBC was an important photoactive constituent, however, the photochemical activity of DBC from the co-pyrolysis plastic and biomass remains unclear. Herein three popular plastic wastes (polystyrene, PS; polylactic acid, PLA; plastic mulch film, PMF) and pine needle biomass prepared co-pyrolysis biochar, and effects of co-pyrolysis plastics on DBC’s photogeneration ability of reactive intermediates, affecting pollutant photodegradation, were investigated. In comparison to individual DBC, the mixed DBC from co-pyrolysis biochar had a lower molecular weight and more oxygen-containing groups. Quantum yields of singlet oxygen (1O2) and triplet state DBC (3DBC*) from mixed DBC were higher, especially PMF-DBC since its lower aromaticity and molecular weight connected with its higher E2/E3 and lower SUVA254 values. Steady-state photochemical experiment demonstrated 3DBC* formation rates for mixed DBC were lower than individual DBC, while the second-order reaction rate constants of 3DBC* with 2,4,6-trimethylphenol for mixed DBC were higher than that of individual DBC. Quenching experiment by sorbic acid to distinguish high/low-energy triplets revealed that contributions of low-energy triplets to 3DBC* and 1O2 generation decreased relative to individual DBC, indicating the transformation of reductive groups to oxidative groups, which was supported by the phototransformation kinetics. Quantum yields of 3DBC* and 1O2 were positively linear correlations with E2/E3 using twenty DBC samples. These findings are helpful in understanding DBC’s photochemical activity from co-pyrolysis of plastics and biomass, especially in aquatic environments adjacent to soil amended by biochar.

Synthesis of novel cationic photosensitizers derived from chlorin for application in photodynamic therapy of cancer.

Background Chlorins (dihydroporphyrins) are tetrapyrrole-based compounds that are more effective in photodynamic therapy than porphyrins. The instability of the compounds and their oxidation to porphyrin limits the use of these compounds. However, the design and synthesis of new stable chlorin-based cationic photosensitizers with the potential for use in cancer photodynamic therapy can be interesting. Methods In this research, new tetracationic meso substituted chlorins were designed, synthesized, and characterized. After determining the chemical structure and spectroscopic properties of five new photosensitizers, their phototoxicity on breast cancer cell lines (MCF-7) was investigated under optimized conditions in terms of factors such as photosensitizer concentrations and light intensity. Results The results of cytotoxicity assayed by the MTT method showed that the synthesized compounds, even up to the concentration of 50 μM had very low toxicity in the absence of light, which indicates their safety under dark conditions. Compounds A1 and A3 with the best physicochemical properties such as solubility, high absorption intensity in the effective range of photodynamic therapy, and the high quantum yield of singlet oxygen, had a good toxic effect (IC50=0.5 μM) on the cancer cells (MCF-7) in the presence of laser light. Conclusion According to the obtained results, compounds A1 and A3 have the potential to continue research on PDT for confirmation and use in treatment.

Toluidine blue O photosensitizer combined with caffeic acid improves antibacterial performance by increasing the permeability of cell membrane

Photodynamic therapy has always been an antibacterial tool for solving multi-drug resistant bacteria problem, but the side effects and the low efficiency due to the high aggregation and low solubility of photosensitizers limit its application. Due to the anti-inflammatory effect of caffeic acid, two novel photosensitizers (CA-1-TBO, CA-TBO) were synthesized by conjugating caffeic acid with toluidine blue O (TBO). The structures have been characterized by 1HNMR and high-resolution mass spectrometry. The UV-vis absorption, fluorescence spectra and the octanol-water partition coefficient of two photosensitizers were measured to evaluate their photophysical properties and hydrophilic/hydrophobic properties. Compared with parent TBO, the two modified photosensitizers have shown a higher quantum yield and kinetics constants of singlet oxygen, which has been supported by the simulation results of density functional theory. As drug-resistant representatives of gram-positive and gram-negative bacteria, respectively, S. aureus and P. aeruginosa have been used for in vitro antibacterial experiments. The sterilization efficiencies of the two modified photosensitizers far exceed that of parent TBO. The results of the octanol-water partition coefficient and fluorescence quantification showed that modified photosensitizers CA-1-TBO and CA-TBO could be more accumulated than parent TBO. Based on scanning electron microscopy images, protein gel electrophoresis, and the conductivity of the bacterial solution, the possible mechanism of improved antibacterial photodynamic efficiencies could be induced by membrane permeability due to the caffeic acid effect. The findings demonstrate the significant potential of natural phenolic compounds in the development of photosensitizer molecules with characteristics such as more efficient, biocompatible and less side effects.

Defect-rich platinum-zinc oxide heterojunction as a potent ROS amplifier for synergistic sono-catalytic therapy.

Sonodynamic therapy (SDT) is a physical therapy that utilizes critical sonosensitizers triggered by ultrasound to achieve an effective non-invasive tumor treatment. However, the inadequate sonodynamic efficacy and low responsive activities of traditional inorganic sonosensitizers have hindered its practical application. Here, we rationally design a platinum-zinc oxide (PtZnO) sonosensitizer to significantly enhance the efficacy of SDT through its inherent bandgap structure and dual-nanozyme activities. The PtZnO possesses a narrow bandgap (2.89eV) and an appropriate amount of oxygen defects, which promote the efficiency of electrons and holes separation and the generation of reactive oxygen species (ROS) under US irradiation. Simultaneously, the PtZnO exhibits both catalase-like and peroxidase-like activities, which effectively catalyze endogenous H2O2 into a large number of O2 and toxic hydroxyl radicals (•OH), thus achieving an efficient enhancement of SDT and catalytic therapy. Moreover, the PtZnO has significant glutathione consumption performance, further amplifying the oxidative stress. Ultimately, the PtZnO achieves a triple ROS amplification effect, with the yields of singlet oxygen (1O2) and •OH reaching 859.1% and 614.4%, respectively, inducing a highly effective sono-catalytic therapy with a remarkable tumor inhibition rate of 98.1%. This study expands the application of ZnO semiconductor heterojunctions in the nanomedicine area, and the simple yet efficient design of the PtZnO provides a strategy for the development of sonosensitizers. STATEMENT OF SIGNIFICANCE: A platinum-zinc oxide (PtZnO) heterojunction sonosensitizer is constructed with dual-nanozyme activities and achieves a triple ROS amplification effect, leading to an efficient synergistic sono-catalytic therapy. The PtZnO owns an inherent narrow bandgap and abundant oxygen defects, thus exhibiting an efficient sonosensitizer performance. It also possesses both catalase-like and peroxidase-like activities, which effectively catalyze the endogenous H2O2 into a large quantity of O2 and toxic hydroxyl radicals, thereby enhancing the SDT and catalytic therapy. Furthermore, its prominent glutathione consumption performance further amplifies oxidative stress. The yields of singlet oxygen and hydroxyl radicals reach up to 859.1% and 614.4%, respectively, inducing a highly effective sono-catalytic therapy with an impressive tumor inhibition rate of 98.1%.

Synthesis, Photophysical Properties, and Toxicity of o-Xylene-Bridged Porphyrin Dimers

In this work, a number of new porphyrin dimers coupled with spacers based on α,α’-dibromo-o-xylene were synthesized and characterized by 1H, 13C NMR, 1H-1H COSY NMR, UV-vis-spectroscopy, and MALDI-TOF mass spectrometry. The initial A3B-type hydroxy-substituted porphyrins form dimer structures with high yields of 80–85%, while the use of amino-substituted porphyrins as starting compounds leads to the heterocyclization and formation of N-heterocycle fused porphyrins. For porphyrin dimers, photophysical properties and quantum yields of singlet oxygen were investigated. The peripheral alkoxy-substituents increase fluorescence quantum yield in comparison with the unsubstituted compounds. Also, it was found that dimers are characterized by lower singlet oxygen quantum yields compared to the corresponding monomers. Model aggregation experiments in micellar systems demonstrate stabilization of the photoactive monomolecular form of all the porphyrins, using nonionic surfactant Triton X-100. Cytotoxicity of received dimers shows high inhibition against HEK293T cells in the absence of light.