Photodynamic Mechanism Research Articles

Photoinactivation mechanism of hypericin nanoencapsulated in P123 against Microsporum canis.

Aim: To evaluate the photodynamic mechanism of hypericin nanoencapsulated in P123 copolymer micelles against Microsporum canis in vitro.Material & methods: Antifungal susceptibility tests were performed, including the determination of the minimum fungicidal concentration and time-kill curve. Flow cytometry was used to evaluate the internalization of P123-Hyp in conidia and the activation of PDT type I and II mechanisms via the detection of reactive oxygen species (ROS), as well as to assess changes in the cell membrane using propidium iodide (PI) and cell morphology.Results: P123-Hyp-PDT exerted a fungistatic action on fungus, maintaining this action up to 24h after exposure, corroborating the PS internalization results, which showed satisfactory uptake of P123-Hyp from a concentration of 3.125μmol/l. Among the ROS studied, singlet oxygen was detected. Furthermore, the increased fluorescence intensity of PI in treated cells indicated necrotic cell death, while the size and granularity of the cells were also altered.Conclusion: Our results show, for the first time, a proposal for the mechanism of action of P123-Hyp-mediated PDT against M. canis, proving that it has a prolonged action on the fungus through activation of the type II photodynamic pathway, which resulted in disruption of the plasma membrane and cellular alterations.

Effect of gum Arabic on antifungal photodynamic activity of curcumin against Botrytis cinerea spores

This study investigated the effect of gum Arabic on curcumin's phototoxicity against Botrytis cinerea, a significant cause of postharvest losses in horticultural produce. Curcumin-loaded nanoparticle suspensions and emulsions stabilized with gum Arabic were prepared and their absorbance, fluorescence emission, physicochemical properties, antimicrobial photodynamic activity (using response surface methodology (RSM)), and reactive oxygen species (ROS) generation (via electron paramagnetic resonance (EPR) spectroscopy) were evaluated. Fluorescence emission exhibited a blue shift (510–550 nm) in both formulations, with emulsions showing higher intensities due to a more hydrophobic environment. Gum Arabic concentration significantly influenced the physicochemical properties of both suspensions, with nanoparticle size decreasing from 572.80 nm to 202.80 nm as gum Arabic concentration increased from 0.5 % to 2.5 % (at 65 μM curcumin). Nanoparticle suspensions demonstrated higher antimicrobial efficacy, reducing B. cinerea spores by 0.39–3.40 log10(CFU.ml−1), compared to 0.00–0.46 log10(CFU.ml−1) in emulsions. The phototoxic effect was dependent on curcumin concentration and light irradiance, as demonstrated by RSM. EPR confirmed the generation of superoxide anion and hydroxyl radicals in both formulations, which indicated a Type I photodynamic mechanism, with nanoparticle suspensions having a sustained ROS generation. Overall, gum Arabic did not impair curcumin's antifungal photodynamic activity, making it as a promising stabiliser for curcumin-based treatments.

Disinfection of bacteria and viruses under near infrared light by tunable self-assembled nanomaterial NH2-MIL-101-xAu based on photothermal and photodynamic mechanisms

In response to the threat posed by multi-drug resistant "superbugs", a synergistic approach of photothermal therapy (PTT) and photodynamic therapy (PDT) has been developed. In this work, NH2-MIL-101-xAu was prepared by introducing Au nanoparticles on the surface of NH2-MIL-101 n-type semiconductor by means of self-assembly. The introduction of Au nanoparticles greatly improves the light absorption and utilization of nanomaterials. Based on the surface plasma response (SPR), NH2-MIL-101-xAu has an efficient photothermal conversion ability, and under the irradiation of 808 nm (1 W/cm2), NH2-MIL-101–5.0Au (0.50 mg/mL) can be heated to 60℃ in 3 min. And the synergistic effect of plasma-induced interfacial charge-transfer transition and Schottky barriers dramatically enhances the photogenerated carrier separation of NH2-MIL-101-xAu, which in turn generates a large number of reactive oxygen species (ROS). Under the experimental conditions, NH2-MIL-101-xAu with the synergistic effect of PTT and PDT had the sterilization rate of 99.99999 % against Escherichia coli and Staphylococcus aureus, and the inactivation rate of Bacteriophage MS2 was more than 99.9 %. This study shows that NH2-MIL-101-xAu possessing a high degree of tunability is an effective PTT and PDT synergistic means of destroying pathogens, which is very helpful in the application of eliminating drug-resistant bacteria.

Preparation and exploration of anti-tumor activity of Poria cocos polysaccharide gold nanorods

With the continuous advancement of nanotechnology, the application of gold nanorods (AuNRs) functionalized with polysaccharides in the realm of cancer photothermal therapy is garnering increasing attention. To harness photothermal therapy for cancer treatment, FLP-MPBA-AuNRs were successfully synthesized in this study for the first time, utilizing Poria cocos polysaccharides (FLP), mercaptophenylboronic acid (MPBA), and gold nanorods (AuNRs). FLP-MPBA-AuNRs are a nanomaterial characterized by a unique rod-shaped structure, featuring a long diameter of 29.3 nm and a short diameter of 6.5 nm, which conferred exceptional photothermal stability and remarkable photothermal conversion efficiency. Under near-infrared light irradiation, FLP-MPBA-AuNRs elicited significant photothermal effects, effectively curtailing the proliferation of various cancer cells. Additionally, FLP-MPBA-AuNRs impeded cancer progression by inducing cell apoptosis and releasing reactive oxygen species (ROS). Furthermore, FLP-MPBA-AuNRs suppressed the metastasis and growth of cancer cells in zebrafish models. In summary, FLP-MPBA-AuNRs showcased immense potential in cancer therapy by inhibiting tumor cell growth through photothermal and photodynamic mechanisms.

Insight into the photodynamic mechanism and protein binding of a nitrosyl iron−sulfur [Fe2S2(NO)4]2− cluster

Iron−sulfur cluster conversion and nitrosyl modification are involved in regulating their functions and play critical roles in signaling for biological systems. Hereby, the photo-induced dynamic process of (Me4N)2[Fe2S2(NO)4] was monitored using time-resolved electron paramagnetic resonance (EPR) spectra, MS spectra and cellular imaging methods. Photo-irradiation and the solvent affect the reaction rates and products. Spectroscopic and kinetic studies have shown that the process involves at least three intermediates: spin-trapped NO free radical species with a gav at 2.040, and two other iron nitrosyl species, dinitrosyl iron units (DNICs) and mononitrosyl iron units (MNICs) with gav values at 2.031 and 2.024, respectively. Moreover, the [Fe2S2(NO)4]2- cluster could bind with ferritin and decompose gradually, and a binding state of dinitrosyl iron coordinated with Cys102 of the recombinant human heavy chain ferritin (rHuHF) was finally formed. This study provides insight into the photodynamic mechanism of nitrosyl iron − sulfur clusters to improve the understanding of physiological activity.

Photo-sensitive Antibacterial Activity of o-Phenylenediamine Carbon Dots

Carbon dots (CDs) are among the famous nanoparticles that have been widely developed due to high biocompatibility, low toxicity, ease of preparation, excellent photoluminescent properties, and outstanding application in biomedicine. Among the various biomedical activities of CDs, they can be applied as antibacterial agents because of their photodynamic properties. Photodynamic therapy (PDT) has been considered an alternative antibacterial agent because of its non-invasive nature and minimal side effects, especially in terms of improving antibacterial activity against multidrug resistant bacteria when compared with traditional antibiotics. In this research, we developed CDs from o-phenylenediamine (OP). The o-phenylenediamine CDs (OPCDs) were synthesized via a hydrothermal method at 180°C for 3 h. After that, they revealed a spherical shape with a size range of 16.38 ± 2.64 nm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of OPCDs against Staphylococcus aureus (S. aureus) for both light exposure and without light exposure groups were significantly greater than the OP solution because the OPCDs could generate reactive oxygen species (ROS) via a photodynamic mechanism leading to the bacteria cell death. Therefore, the created OPCDs may have the capability to be utilized for treating skin infections caused mainly by S. aureus. In conclusion, OPCDs could be proposed as nanomaterials that enhance antibacterial activity and provide photodynamic properties.

Indocyanine green based photodynamic therapy for keloids: Fundamental investigation and clinical improvement

BackgroundKeloid, a prevalent pathological skin lesion, presents significant challenges in terms of treatment efficacy. Photodynamic therapy (PDT), an increasingly popular adjuvant treatment, has shown significant potential in the management of various disorders, including cancer. However, the therapeutic potential of indocyanine green-mediated photodynamic therapy (ICG-PDT) for keloids has not yet been demonstrated. MethodsIn this study, we divided the experimental groups into control group, Photothermal Therapy group, Photodynamic Therapy group, and Combined Therapy group. The in vitro investigation aimed to optimize the clinical application of PDT for keloid treatment by elucidating its underlying mechanism. Subsequently, on this basis, we endeavored to manage a clinical case of keloid by employing surgical intervention in conjunction with modified ICG-PDT. ResultsOur investigation revealed an unexpected outcome that ICG-PDT maximally inhibited the cellular activity and migration of keloid fibroblasts only when photodynamic mechanism took effect. Additionally, the induction of autophagy and apoptosis, as well as the inhibition of collagen synthesis, were particularly evident in this experimental group. Furthermore, the above therapeutic effect could be achieved at remarkably low drug concentrations. Building upon the aforementioned experimental findings, we successfully optimized the treatment modality for the latest case and obtained a more favorable treatment outcome. ConclusionsThis study investigated the mechanism of ICG-PDT treatment and optimized the in vivo treatment regimen, demonstrating the significant therapeutic potential of ICG-PDT treatment in clinical keloid treatment.

Recent Development of Copper (II) Complexes of Polypyridyl Ligands in Chemotherapy and Photodynamic Therapy.

Cancer is a deadly disease associated with abnormal cell growth and invasion to various parts of the body. Many drugs such as cisplatin and carboplatin have been used for the treatment of cancer over the years. However, a lack of selectivity toward cancer cells and associated side effects with current treatment options has fueled continued efforts throughout the world to find better anticancer drugs. Over the past decades, copper-containing compounds have shown excellent anticancer activity. Cu(II) complexes are well studied and show broad-spectrum pharmacological activity. The redox activity of copper ions contributes to cytotoxic activity in combination with ligands that possess bioactivity. Binding of copper with various types of bidentate, tridentate, and tetradentate ligands can activate the processes of necrosis, apoptosis, and angiogenesis. Copper induces the formation of reactive oxygen species to cleave DNA. Similarly, light-assisted excitation of Cu(II) complexes in the red region of the electromagnetic spectrum helps produce different reactive species, thereby inducing anticancer activity through a photodynamic mechanism. In general, in vivo and in vitro studies have demonstrated that the administration of copper ions is effective against various cancer cell lines. Herein we discuss the past ten years of research into copper complexes of terpyridine-, 2,2'-bipyridine-, and 1,10-phenanthroline-based ligands as potential anticancer agents. The aspects of chemotherapy by redox-mediated pathways and photodynamic therapy using light-assisted excitation are reviewed, with a focus on mechanisms of activity, details of important experimental procedures, as well as drawbacks in the design of copper-containing drugs.

Insights into the Photodynamics of Fluorescence Emission and Singlet Oxygen Generation of Fluorogen Activating Protein-Malachite Green Systems.

The self-assembled fluorogen activating protein (FAP)-malachite green (MG) complex is a well-established protein-ligand system, which can realize binding-caused fluorescence turn-on of MG and singlet oxygen (1 O2 ) generation by MG iodination. To clarify the mechanism of fluorescence activation and 1 O2 generation, the photodynamics of different halogen-substituted MG derivatives and their corresponding FAP-MG complexes were studied by femtosecond transient absorption spectroscopy and theoretical computations. The results show that the rotation of MG is restricted by FAP binding, which prevents a rapid internal conversion to allow a longer lifetime for the excited MG to undergo fluorescence emission and intersystem crossing. Moreover, these FAP-MG complexes exhibit notably varied fluorescence quantum yields (ΦFL ) and 1 O2 yields. The study on the decay pathways indicates that such an anti-heavy atom effect predominately stems from the lifetimes of the excited-state species. The photodynamic mechanism study here will lead to more advanced FAP-MG systems with high spatiotemporal resolution.

Tuning the Molecular Structure of Corroles to Enhance the Antibacterial Photosensitizing Activity.

The increase in the antibiotic resistance of bacteria is a serious threat to public health. Photodynamic inactivation (PDI) of micro-organisms is a reliable antimicrobial therapy to treat a broad spectrum of complex infections. The development of new photosensitizers with suitable properties is a key factor to consider in the optimization of this therapy. In this sense, four corroles were designed to study how the number of cationic centers can influence the efficacy of antibacterial photodynamic treatments. First, 5,10,15-Tris(pentafluorophenyl)corrole (Co) and 5,15-bis(pentafluorophenyl)-10-(4-(trifluoromethyl)phenyl)corrole (Co-CF3) were synthesized, and then derivatized by nucleophilic aromatic substitution with 2-dimethylaminoethanol and 2-(dimethylamino)ethylamine, obtaining corroles Co-3NMe2 and Co-CF3-2NMe2, respectively. The straightforward synthetic strategy gave rise to macrocycles with different numbers of tertiary amines that can acquire positive charges in an aqueous medium by protonation at physiological pH. Spectroscopic and photodynamic studies demonstrated that their properties as chromophores and photosensitizers were unaffected, regardless of the substituent groups on the periphery. All tetrapyrrolic macrocycles were able to produce reactive oxygen species (ROS) by both photodynamic mechanisms. Uptake experiments, the level of ROS produced in vitro, and PDI treatments mediated by these compounds were assessed against clinical strains: methicillin-resistant Staphylococcus aureus and Klebsiella pneumoniae. In vitro experiments indicated that the peripheral substitution significantly affected the uptake of the photosensitizers by microbes and, consequently, the photoinactivation performance. Co-3NMe2 was the most effective in killing both Gram-positive and Gram-negative bacteria (inactivation > 99.99%). This work lays the foundations for the development of new corrole derivatives having pH-activable cationic groups and with plausible applications as effective broad-spectrum antimicrobial photosensitizers.

Light-Activated Antibacterial Polymeric Surface Based on Porphycene

A photoactivatable antimicrobial polymeric surface based on a porphycene derivate was efficiently prepared and evaluated to kill pathogenic microorganisms. The development of this self-sterilizing material consisted in the electrochemical polymerization of a peripherally tetra-substituted porphycene bearing benzyl-carbazole groups (Pc-Cbz). The latter were used as electropolymerizable centers, while the porphycene core triggered the photodynamic action. The electrodeposited photodynamic films (P-Pc-Cbz) were obtained in a reproducible and controllable manner. Electrochemistry studies combined with spectroscopic measurements demonstrated that the porphycene core remains unaffected after the electrodeposition process. Moreover, it retains its spectroscopic and photodynamic properties within the polymeric matrix. The photoactive layers were photostable and able to produce reactive oxygen species (ROS) by both photodynamic mechanisms. Also, the antimicrobial efficiency of P-Pc-Cbz was evaluated against two antibiotic-resistant strains (methicillin-resistant Staphylococcus aureus and Escherichia coli), exhibiting an antimicrobial action higher than 99.998% over these Gram-positive and Gram-negative bacteria. This work represents the first electropolymerization of a porphycene derivative and the first porphycene-based photobiocidal surface. P-Pc-Cbz shows great potential as an efficient self-sterilizing coating activated by visible light.

Development of Biotechnological Photosensitizers for Photodynamic Therapy: Cancer Research and Treatment-From Benchtop to Clinical Practice.

Photodynamic therapy (PDT) is a noninvasive therapeutic approach that has been applied in studies for the treatment of various diseases. In this context, PDT has been suggested as a new therapy or adjuvant therapy to traditional cancer therapy. The mode of action of PDT consists of the generation of singlet oxygen (¹O2) and reactive oxygen species (ROS) through the administration of a compound called photosensitizer (PS), a light source, and molecular oxygen (3O2). This combination generates controlled photochemical reactions (photodynamic mechanisms) that produce ROS, such as singlet oxygen (¹O2), which can induce apoptosis and/or cell death induced by necrosis, degeneration of the tumor vasculature, stimulation of the antitumor immune response, and induction of inflammatory reactions in the illuminated region. However, the traditional compounds used in PDT limit its application. In this context, compounds of biotechnological origin with photosensitizing activity in association with nanotechnology are being used in PDT, aiming at its application in several types of cancer but with less toxicity toward neighboring tissues and better absorption of light for more aggressive types of cancer. In this review, we present studies involving innovatively developed PS that aimed to improve the efficiency of PDT in cancer treatment. Specifically, we focused on the clinical translation and application of PS of natural origin on cancer.

Porphycenes as broad-spectrum antimicrobial photosensitizers. Potentiation with potassium iodide

Two novel meso-tetrasubstituted porphycenes (Pc-Cbz and Pc-NEt2) have been synthesized by palladium-catalyzed Suzuki cross-coupling reactions over 9,10,19,20-tetrakis(4-iodophenyl)porphycene. Pc-Cbz contains four carbazole groups on the periphery of the tetrapyrrolic macrocycle. Instead, Pc-NEt2 presents four basic tertiary amine substituents, which can be protonated at physiological pH, acquiring four positive charges. Both photosensitizers (PSs) were designed to evaluate the effect of different substitution patterns on the photodynamic inactivation of microorganisms. Their absorption and fluorescence properties were almost unmodified regardless of the substituent groups on the periphery. The characteristic red emission makes them promising fluorescent probes for cell imaging. Moreover, both macrocycles were able to generate reactive oxygen species by both photodynamic mechanisms under aerobic light irradiation. The photokilling action of these PSs was assessed in vitro against Candida albicans (yeast), Staphylococcus aureus (Gram-positive bacterium), and Escherichia coli (Gram-negative bacterium). Our results demonstrate that the peripheral substitution significantly affected the photoinactivation performance. Thus, Pc-NEt2 was more effective than Pc-Cbz in killing microorganisms using lower concentrations and shorter irradiation periods, evidencing that external substitution is a main structural feature. Also, the photoinactivation efficiency mediated by these porphycenes was potentiated by adding KI. Under these conditions, a complete eradication of all pathogenic microorganisms was obtained by combining Pc-NEt2 and KI. Therefore, Pc-NEt2 can be used as an effective broad-spectrum antimicrobial PS. Accordingly, this work stands out as a promising starting point for the design of new porphycene-based PSs for photodynamic inactivation (PDI) of microorganisms. Our outcomes also disclose that the combination of these PSs with KI is an important factor in order to improve the PDI treatments and the current antimicrobial therapies.

Antibacterial and Antibiofilm Potency of XF Drugs, Impact of Photodynamic Activation and Synergy With Antibiotics

With increasing incidence of antimicrobial resistance, there is an urgent need for novel and effective antibacterials. Destiny Pharma plc have developed a series of porphyrin-based XF drugs, some with dual mechanisms of antibacterial action. An innate mechanism acts through binding to the outer bacterial membrane and a separate, light-activated, photodynamic (PD) mechanism, acts via the generation of reactive oxygen species. This study aimed to assess the innate and PD associated antibacterial activity of XF drugs against planktonic bacteria, their biofilms and combinational effects with conventional antibiotics. Minimum inhibitory concentrations (MICs) were determined for 3 XF drugs against 114 bacterial isolates. MICs for XF-73 and XF-70 were determined (± PD). DPD-207 was designed to not exhibit PD action due to its structure. XF-drugs (± PD) were further assessed for synergy with conventional antibiotics (using a checkerboard assay) and antibiofilm activity against susceptible strains. XF drugs were innately active against all tested Gram-positive isolates. PD action significantly increased bacterial susceptibility to XF-73 and XF-70 for all Gram-positive isolates. Generally, the XF drugs exhibited higher MICs against Gram-negative isolates, however PD significantly enhanced potency, particularly for XF-70. XF-73 and XF-70 exhibited synergy with ertapenem against a methicillin resistant Staphylococcus aureus (MRSA) strain (± PD) and XF-73 with polymyxin B (± PD) against Pseudomonas aeruginosa. No antagonism was seen between the XF drugs and any of the 5 antibiotics tested. The antibiofilm effect of XF drugs was also observed for all Staphylococcus isolates tested. Generally, PD did not enhance activity for other bacterial isolates tested with the exception of XF-73 against Acinetobacter baumannii biofilms. XF drugs exhibited significant antimicrobial activity against Gram-positive bacteria, with PD enhancement of bacterial susceptibility. Additionally, XF drugs displayed synergy with conventional antibiotics and demonstrated antibiofilm effects.

Radiationless mechanism of UV deactivation by cuticle phenolics in plants

Hydroxycinnamic acids present in plant cuticles, the interphase and the main protective barrier between the plant and the environment, exhibit singular photochemical properties that could allow them to act as a UV shield. Here, we employ transient absorption spectroscopy on isolated cuticles and leaf epidermises to study in situ the photodynamics of these molecules in the excited state. Based on quantum chemical calculations on p-coumaric acid, the main phenolic acid present in the cuticle, we propose a model in which cuticle phenolics display a photoprotective mechanism based in an ultrafast and non-radiative excited state deactivation combined with fluorescence emission. As such, the cuticle can be regarded as the first and foremost protective barrier against UV radiation. This photostable and photodynamic mechanism seems to be universal in land plants giving a special role and function to the presence of different aromatic domains in plant cuticles and epidermises.

Cover Feature: BOPHY‐Fullerene C60 Dyad as a Photosensitizer for Antimicrobial Photodynamic Therapy (Chem. Eur. J. 5/2022)

A heavy-atom-free BOPHY-based photosensitizer (PS) has been obtained as a mixture of two atropisomers. The BOPHY core works as a visible light-harvesting center and donor antenna, while a fullerene C60 acceptor acts as an effective spin converter and triggers photodynamic action. The dyad is capable of producing reactive oxygen species (ROS) by both photodynamic mechanisms. In-vitro studies indicate that the dyad photokills microorganisms after visible light irradiation. More information can be found in the Research Article by D. A. Heredia et al. (DOI: 10.1002/chem.202103884).

Direct Detection of the Photorearrangement Reaction of Quinoline-Protected Dialkylanilines.

ABSTRACTThe photolysis reactions of (8‐cyano‐7‐hydroxyquinolin‐2‐yl)methyl (CyHQ)‐caged amines have been investigated using time‐resolved spectroscopy methods. Unexpectedly, an unconventional Hofmann‐Martius rearrangement reaction with high yield and regioselectivity occurred during the photolysis of some CyHQ‐protected dialkylanilines (such as compounds 1a and 2a). To have more insights into the mechanism of this unexpected photorearrangement reaction, we characterized the reaction intermediates directly using time‐resolved spectroscopy. Our new results showed that the anionic form of compound 1a was photoexcited to the singlet excited state, then a heterolytic cleavage of the C‐N bond took place to give CyHQ+ and the corresponding aniline. Thereafter, the recombined intermediate 6 was found to appear in about 19.7 and 44.3 ps for 1a (A) and 2a (A), respectively, before the generation of an ortho‐substituted aniline (1b and 2b) via the excited‐state deprotonation of 6. Thus, a logical photodynamic mechanism of this photoinduced Hofmann‐Martius rearrangement reaction was deduced. This new insight into the reaction mechanisms may be helpful for the design of novel related photoactivatable aniline molecules and for understanding other similar photorearrangement reaction mechanisms.

TB@PLGA Nanoparticles for Photodynamic/Photothermal Combined Cancer Therapy with Single Near-Infrared Irradiation.

BackgroundPhototherapy has significant potential as an effective treatment for cancer. However, the application of a multifunctional nanoplatform for photodynamic therapy (PDT) and photothermal therapy (PTT) at a single excitation wavelength remains a challenge.Materials and MethodsThe double emulsion solvent evaporation method was used to prepare toluidine blue@poly lactic-co-glycolic acid (TB@PLGA) nanoparticles (NPs). The biocompatibility of TB@PLGA NPs was evaluated, and a 660 nm luminescence was used as the light source. The photothermal effect, photothermal stability, and singlet oxygen yield of NPs in an aqueous solution verified the feasibility of NPs as a PTT/PDT synergistic therapy drug.ResultsTB@PLGA NPs were successfully prepared and characterized. In vitro experiments demonstrated that TB@PLGA NPs can cause massive necrosis of tumor cells and induce apoptosis through a photodynamic mechanism under 660 nm laser irradiation. The TB@PLGA NPs also achieved optimal tumor inhibition effect in vivo.ConclusionThe TB@PLGA NPs prepared in this study were applied as a dual-mode phototherapeutic agent under single laser irradiation. Both in vitro and in vivo experiments demonstrated the good potential of PTT/PDT for tumor inhibitors.

Nanoparticles of water-soluble dyads based on amino acid fullerene C60 derivatives and pyropheophorbide: Synthesis, photophysical properties, and photodynamic activity

Synthesis, spectral properties, and photodynamic activity of water-soluble amino acid fullerene C60 derivatives (AFD) and four original AFD-PPa dyads, obtained by covalent addition of dye pyropheophorbide (PPa) to AFD, were studied. In aqueous solution, these AFD-PPa dyads form nanoassociates as a result of self-assembly. In this case, a significant change in the absorption spectra and strong quenching of the dye fluorescence in the structure of the dyads were observed. A comparison of superoxide or singlet oxygen generation efficiency of the studied compounds in an aqueous solution showed the photodynamic mechanism switching from type II (singlet oxygen generation of the native dye) to I type (superoxide generation of dyads). All dyads have pronounced phototoxicity on cells Hela with IC50 9.2 µM, 9.2 µM, 12.2 µM for dyads Val-C60-PPa, Ala-C60-PPa and Pro-C60-PPa, respectively. Such facilitation of type I photodynamic mechanism could be perspective against hypoxic tumors.

Photodynamic Therapy for Advanced Rectal Cancer: A Case Report

Objective: To investigate the potential value of PDT(photodynamic therapy) in the treatment of rectal cancer by reviewing the diagnosis and treatment process of a patient with advanced rectal cancer who lost the opportunity of surgery. Methods: Select the case data of a patient receiving photodynamic therapy in our hospital, and analyze the photodynamic mechanism, safety and efficiency, and discuss the efficacy of photodynamic therapy. Results: After the patient received photodynamic therapy, re-examination of the endoscopy showed that the intestinal cavity was smoother than before, the bowel was difficult, and the symptoms of blood in the stool improved. Conclusion: Photodynamic therapy can be used as a radical or palliative treatment for clinical tumor treatment. Because of its advantages of minimally invasive, tissue-specific, repetitive and synergistic radiotherapy and chemotherapy, it plays an important role in early or middle-advanced colorectal cancer and is worthy of clinical promotion.