Water-soluble Photosensitizer Research Articles

Highly Efficient, Noble-Metal-Free, Fully Aqueous CO2 Photoreduction Sensitized by a Robust Organic Dye.

The development of efficient, selective, and durable CO2 photoreduction systems presents a long-standing challenge in full aqueous solutions owing to the presence of scarce CO2 and the fierce competition against H2 evolution, which is even more challenging when noble metals are not utilized. Herein, we present the facile decorations of four phosphonic acid groups on a donor-acceptor-type organic dye to obtain a water-soluble photosensitizer (4P-DPAIPN), which succeeds the excellent photophysical and photoredox properties of its prototype, exhibiting long-lived delayed fluorescence (>10 μs) in aqueous solutions. Combining 4P-DPAIPN with a cationic cobalt porphyrin catalyst has accomplished record-high apparent quantum yields of 9.4-17.4% at 450 nm for CO2-to-CO photoconversion among the precedented systems (maximum 13%) in fully aqueous solutions. Remarkable selectivity of 82-93% and turnover number of 2700 for CO production can also be achieved with this noble-metal-free system, outperforming a benchmarking ruthenium photosensitizer and a commercial organic dye under parallel conditions. Such high performances of 4P-DPAIPN can be well maintained under real sunlight. More impressively, no significant decomposition of 4P-DPAIPN was detected during the long-term photocatalysis. Eventually, the photoinduced electron transfer pathways were proposed.

Hypoxia mitigation by manganese-doped carbon dots for synergistic photodynamic therapy of oral squamous cell carcinoma.

Photodynamic therapy (PDT) is widely used for cancer treatment due to its non-invasive and precise effectiveness, however, hypoxia in the tumor microenvironment greatly limits the efficacy of photodynamic therapy. Compared with conventional photosensitizers, carbon dots (CDs) have great potential. Therefore, developing a water-soluble, low-toxicity photosensitizer based on CDs is particularly important, especially one that can enhance the photodynamic efficacy using the tumor microenvironment to produce oxygen. Herein, manganese-doped carbon dot (Mn-CDs, ∼2.7nm) nanoenzymes with excellent biocompatibility were prepared by a solvothermal method using ethylenediaminetetraacetic acid manganese disodium salt hydrate and o-phenylenediamine as precursors. TEM, AFM, HR-TEM, XRD, XPS, FT-IR, ζ potential, DLS, UV-Vis, and PL spectra were used to characterize the Mn-CDs. Cancer resistance was assessed using the CCK-8 kit, calcein AM versus propidium iodide (PI) kit, and the Annexin V-FITC/PI cell apoptosis assay kit. The obtained Mn-CDs have excellent near-infrared emission properties, stability, and efficient 1O2 generation. Notably, the manganese doping renders CDs with catalase (CAT)-like activity, which leads to the decomposition of acidic H2O2 in situ to generate O2, enhancing the PDT efficacy against OSCC-9 cells under 635nm (300mW·cm-2) irradiation. Thus, this work provides a simple and feasible method for the development of water-soluble photosensitizers with oxygen production, presenting good biosafety for PDT in hypoxic tumors.

Development of water-soluble phenazine-2,3-diol-based photosensitizers for singlet oxygen generation.

Phenazine-2,3-diol-based dyes, KY-1Na and KY-2Na bearing one and two carboxylic acid sodium salts, respectively, have been newly developed as water-soluble photosensitizers (PSs) possessing the ability to generate singlet oxygen (1O2). In order to evaluate the solubility of KY-1Na and KY-2Na in water, the hydrophobicity/hydrophilicity of the two PSs was investigated by experimental measurement of the logarithms (log Po/w) of the 1-octanol/water partition coefficient (Po/w) for the PS. The log Po/w values of both KY-1Na and KY-2Na were determined to be -0.9, indicating that both the PSs are more hydrophilic than Rose Bengal (-0.6) and have hydrophilicity equivalent to methylene blue (-0.9). Both the PSs in water show a broad photoabsorption band in the range of 500 to 600 nm. Thus, we estimated the 1O2 quantum yields (ΦΔ) of KY-1Na and KY-2Na in water by using 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA) as a water-soluble 1O2 scavenger. It was found that in water the ΦΔ value (0.19) of KY-2Na is higher than that of KY-1Na (0.06). Density functional theory (DFT) calculations suggested that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributions for the molecular structure of KY-2Na are adequately separated, leading to a decrease in the energy gap (ΔEST) between the singlet state (S1) and the triplet state (T1) that causes efficient intersystem crossing (ISC), compared to that for the molecular structure of KY-1Na. Indeed, time-dependent DFT (TD-DFT) calculations demonstrated that the ΔEST(S1-T1) value (0.82 eV) of KY-2Na is smaller than that (0.98 eV) of KY-1Na, resulting in a relatively high ΦΔ value of KY-2Na. Consequently, we demonstrate that phenazine-2,3-diol-based PSs bearing carboxylic acid salts possess high solubility and moderate 1O2 generation ability in water.

Supramolecular and base-induced singlet oxygen generation enhancement of a water-soluble phthalocyanine

Investigation into the reactive oxygen species (ROS) generating abilities of photosensitizers outside of in-vitro/vivo conditions is a crucial element in the wider study of photodynamic therapy (PDT) in clinical settings. Zinc(II) phthalocyanine tetrasulfonic acid (ZnPcTS) is a water-soluble photosensitizer that can generate ROS as singlet oxygen (SO) under irradiation in the red and far-red region of the electromagnetic spectrum. The incorporation of ZnPcTS into nano-fibers of a bis-imidazolium hydrogel was demonstrated and the material was characterized with photophysical, rheological, and microscopy techniques. This supramolecular material containing ZnPcTS (named ZnPcTS_nEqBase@Gels) was found to significantly enhance the SO generation rate with respect to that of ZnPcTS in an aqueous solution. The effect is attributed mainly to reduced aggregation within the gel microenvironment compared with a solution. Furthermore, the preparation of ZnPcTS_nEqBase@Gels was carried out in the presence of varying amounts (0, 1, 2, 3, 4 eq.) of NaOH to improve the dissolution of ZnPcTSby ensuring full deprotonation of the sulfonate. The gel material containing 4 equivalents of NaOH per phthalocyanine was found to have a significantly greater SO-generating ability than the corresponding material containing no base. This phenomenon was shown to be partially a consequence of reduced aggregation as observed in the spectroscopic characterization. The enhancement in SO generation induced by this type of hybrid material makes it an attractive candidate to be used in different applications when efficient SO production is required.

Cage-modified hypocrellin against multidrug-resistant Candida spp. with unprecedented activity in light-triggered combinational photodynamic therapy.

Infections caused by multidrug-resistant fungi pose a devastating threat to human health worldwide, making new antifungal strategies urgently desired. Antimicrobial photodynamic therapy (aPDT) has gained increasing attention due to its potential in fighting against fungal infection. However, the preparation of highly efficient and water-soluble photosensitizers (PSs) for this purpose remains a challenge. Herein, we present a new strategy to prepare powerful PSs for efficient aPDT by introducing a porous cage compound, which could facilitate the transportation of O2 and reactive oxygen species (ROS). Specifically, the natural PS hypocrellin A (HA) was attached to a novel organic cage compound (covalent organic polyhedra 1 tied, COP1T) with polyethylene glycol (PEG) chains to improve its water solubility. It was found that the resulting COP1T-HA exhibited in vitro antifungal efficiency several folds higher compared to the free HA in fighting against four types of multidrug-resistant fungal planktonic cells and biofilms, including the "super fungus" Candida auris. Interestingly, the red-shift of COP1T-HA adsorption led to the realization of phototheranostic aPDT for cage-modified HA or derivatives. Additionally, COP1T-HA exhibited good biocompatibility, excellent disinfection capacity and wound healing efficiency without obvious toxic effects in vivo of rat model. With further development and optimization, COP1T-HA has great potential to become a new class of antifungal agent to fight against drug-resistant pathogens.

Gold Nanoparticle Embedded Stimuli-Responsive Functional Glycopolymer: A Potential Material for Synergistic Chemo-Photodynamic Therapy of Cancer Cells.

Photodynamic therapy has emerged as a noninvasive treatment modality for several types of cancers. However, conventional hydrophobic photosensitizers (PS) suffer from low water solubility and poor tumor-targeting ability. Therefore, PS modified with glycopolymers can offer adequate water solubility, biocompatibility, and tumor-targeting ability due to the presence of multiple sugar units. In this study, a well-defined block copolymer poly(3-O-methacryloyl-d-glucopyranose)-b-poly(2-(4-formylbenzoyloxy)ethylmethacrylate) (PMAG-b-PFBEMA) containing pendant glucose and aldehyde units is synthesized via reversible addition-fragmentation chain transfer polymerization method. A water-soluble PS (toluidine blue O; TBO) and a potent anticancer drug, Doxorubicin (Dox) are introduced to the polymer backbone via acid-labile Schiff-base reaction (PMAG-b-PFBEMA_TBO_Dox). The PMAG-b-PFBEMA_TBO_Dox is then anchored on the surface of gold nanoparticles (AuNPs)via electrostatic interaction. This hybrid system exhibits excellent reactive oxygen species (ROS) generating ability under exposure of 630nm light-emitting diode along with triggered release of Dox under the acidic pH of tumor cells. The in vitro cytotoxicity study on human breast cancer cell line, MDA MB 231, for this hybrid system shows promising results due to the synergistic effect of ROS and Dox released. Thus, this glycopolymer-based dual (chemo-photodynamic) therapy model can work as potential material for future therapeutics.

Photoactivated multifunctional nanoplatform based on lysozyme-Au nanoclusters-curcumin conjugates with FRET effect and multiamplified antimicrobial activity

Photodynamic therapy is a promising alternative to antibiotics in the treatment of bacterial infection, which has the advantages of less side effects, no drug resistance and accurate treatment. However, most photosensitizers (PSs) have some disadvantages, such as poor water solubility, serious self-quenching, poor stability and so on. Therefore, solving the limitations of traditional photosensitizers has become a hot issue in photodynamic therapy. On this basis, the lysozyme (Lys)-gold nanocluster (AuNCs)-curcumin (Cur) conjugate was used as a new type of water-soluble photosensitizer and combined with the bacterial surface through electrostatic interaction to form a bacterial surface enriched in PSs. At the same time, real-time bacterial imaging can be achieved by using the fluorescence properties of Lys-AuNCs-Cur. Under 405 nm light and dark conditions, the inactivation effect of Lys-AuNCs-Cur on Staphylococcus aureus and Escherichia coli was higher than that of free Cur. Moreover, Lys-AuNCs-Cur can also produce enough ROS to kill methicillin-resistant Staphylococcus aureus. The excellent antibacterial properties of nanoparticles may be attributed to the synergism of antibacterial protein lysozyme and AuNCs-Cur nanocomplexes and the increase of 1O2 production. The results of scanning electron microscope and fluorescence microscopic imaging showed that the cell membrane of E. coli and S. aureus was seriously damaged, and facilitated penetration of Lys-AuNCs-Cur nanocomplexes into the bacteria through the damaged cell membrane, and improve the photoinactivation efficiency of bacteria. More importantly, nanoparticles exhibited almost negligible dark cytotoxicity. The coupling of Cur and gold nanoclusters can significantly improve the stability of free curcumin molecules and the ability to generate ROS. Therefore, this work is of great significance for the development of new antimicrobial agents against bacterial infection.

Water-soluble porphyrin photosensitizers containing electron-withdrawing and electron-donating groups for photodynamic therapy

Photodynamic therapy is used to treat a variety of cancers. In this paper, water-soluble porphyrin photosensitizers (H2P1[Formula: see text]H2P3) for photodynamic therapy were synthesized, containing three groups -CH3, -CN, and -CF3. Density functional theory is used to optimize the structure of H2P1-H2P3 and calculate the [Formula: see text]E value. The smaller the value of [Formula: see text]E, the more favorable the electron transfer and thus the higher activity of the porphyrin photosensitizers. Due to the electron-withdrawing groups of -CN and -CF3, H2P2 and H2P3 have lower [Formula: see text]E values, higher reactive oxygen species yields compared with H2P1. The H2P2 porphyrin photosensitizers showed positive photodynamic therapeutic activity against hepatocellular carcinoma cells (HepG2) and good compatibility with human umbilical vein endothelial cells (HUVECs) by cellular anticancer activity assay. The anti-cancer mechanism of PSs was explained by living and dead cell staining experiment and intracellular reactive oxygen species experiment. PSs produced reactive oxygen species (ROS) in cancer cells under light irradiation, which induced cancer cell apoptosis.

Coupling BODIPY with nitrogen-doped graphene quantum dots to address the water solubility of photosensitizers

Water-soluble photosensitizers based on covalently grafted nitrogen-doped graphene quantum dot–BODIPY for cellular imaging and photodynamic therapy.

(Keynote) Bio-Inspired Nano-Architectures for Artificial Photosynthesis

The perfect machinery of Natural Photosynthesis, powering our daily life with solar energy, is shaped by a modular network of photocomplexes, where molecular/nano-range order and distances are precisely tuned on membrane-bound compartments.1 Along these guidelines, the current frontier of Artificial Photosynthesis looks at a multi-component, interconnected system, where the cross-talk of photo-active and catalytic building blocks implements function and optimization/repair strategies.1 The expectation for man-made systems is to dissect the photosynthetic complexity and replicate its core-apparatus under a totally artificial environment, using cost-efficient synthetic strategies.2-4 In this scenario supramolecular strategies can play a crucial role to boost photo-assisted catalysis by a tailored interplay of non-covalent interactions, including hydrogen bonding, hydrophobic and electrostatic forces. Building on these concepts we report herein the functional characterization of photosynthetic nano-patterns emerging from the combination of water soluble photosensitizers with oxygenic polyoxometalates (POMs) known as the inorganic analogs of the natural PSII-OEC.5 A. Sartorel, M. Prato, M. Bonchio et. al., Energy Environ. Sci. 2012, 5, 5592.S. Piccinin, A. Sartorel, M. Bonchio, S. Fabris et. al. PNAS 2013, 110, 4917.A. Sartorel, M. Bonchio et al., J. Am. Chem. Soc. 2009, 131, 16051.F. Toma, M. Prato, M. Bonchio, et al. Nature Chemistry 2010, 2, 826.M. Bonchio, A. Sartorel, M. Prato et al. Nature Chemistry 2019, 11, 146.

Computational prediction of photosensitizers’ toxicity

The percentage of failures in late pharmaceutical development due to toxicity has increased dramatically over the last decade or so, resulting in increased demand for new methods to rapidly and reliably predict the toxicity of compounds. Today, computational toxicology can be used in every phase of drug discovery and development, from profiling large libraries early on, to predicting off-target effects in the mid-discovery phase, and to assess potential mutagenic impurities in development and degradants as part of life-cycle management. In this study, for the first time, in silico approaches were used to analyze the possible dark toxicity of photosensitive systems based on chlorin e6 and assessed possible toxicity of these compositions. By applying quantitative structure-activity relationship models (QSARs) and modeling adverse outcome pathways (AOPs), a potential toxic effect of water-soluble (chlorin e6 and chlorin e6 aminoamid) and hydrophobic (tetraphenylporphyrin) photosensitizers (PS) was predicted. Particularly, PSs’ protein binding ability, reactivity to form peptide adducts, glutathione conjugation, activity in dendritic cells, and gene expression activity in keratinocytes were explored. Using a metabolism simulator, possible PS metabolites were predicted and their potential toxicity was assessed as well. It was shown that all tested porphyrin PS and their predicted metabolites possess low activity in the mentioned processes and therefore are unable to cause significant adverse toxic effects under dark conditions.

Balanced Intersystem Crossing in Iodinated Silicon-Fluoresceins Allows New Class of Red Shifted Theranostic Agents.

Iodination of the silicon-fluorescein core revealed a new class of highly cytotoxic, red-shifted and water-soluble photosensitizer (SF-I) which is also fairly emissive to serve as a theranostic agent. Singlet oxygen generation capacity of SF-I was evaluated chemically, and up to 45% singlet oxygen quantum yield was reported in aqueous solutions. SF-I was further tested in triple negative breast (MDA MB-231) and colon (HCT-116) cancer cell lines, which are known to have limited chemotherapy options as well as very poor prognosis. SF-I induced efficient singlet oxygen generation and consequent photocytotoxicity in both cell lines upon light irradiation with a negligible dark toxicity while allowing cell imaging at the same time. SF-I marks the first ever example of a silicon xanthene-based photosensitizer and holds a lot of promise as a small-molecule-based theranostic scaffold.

Metal-Free Nanoassemblies of Water-Soluble Photosensitizer and Adenosine Triphosphate for Efficient and Precise Photodynamic Cancer Therapy.

Engineering photosensitizers into stimuli-responsive supramolecular nanodrugs allows enhanced spatiotemporal delivery and controllable release of photosensitizers, which is promising for dedicated and precise tumor photodynamic therapy. Complicated fabrication for nanodrugs with good tumor accumulation capability and the undesirable side-effects caused by the drug components retards the application of PDT in vivo. The fact that extracellular adenosine triphosphate (ATP) is overexpressed in tumor tissue has been overlooked in fabricating nanomedicines for tumor-targeting delivery. Hence, herein we present metal-free helical nanofibers formed in aqueous solution from the coassembly of a cationic porphyrin and ATP as a nanodrug for PDT. The easily accessible and compatible materials and simple preparation enable the nanodrugs with potential in PDT for cancer. Compared to the cationic porphyrin alone, the porphyrin-ATP nanofibers exhibited enhanced tumor-site photosensitizer delivery through whole-body blood circulation. Overexpressed extracellular ATP stabilizes the porphyrin-ATP nanodrug within tumor tissue, giving rise to enhanced uptake of the nanodrug by cancer cells. The enzyme-triggered release of photosensitizers from the nanodrugs upon biodegradation of ATP by intracellular phosphatases results in good tumor therapeutic efficacy. This study demonstrates the potential for employing the tumor microenvironment to aid the accumulation of nanodrugs in tumors, inspiring the fabrication of smart nanomedicines.

Highly Efficient Water-Soluble Photosensitizer Based on Chlorin: Synthesis, Characterization, and Evaluation for Photodynamic Therapy.

The clinical applications of many photosensitizers (PSs) are limited because of their poor water solubility, weak tissue penetration, low chemical purity, and severe toxicity in the absence of light. We designed a novel chlorin-based PS (designated as HPS) to achieve fluorescence image-guided photodynamic therapy (PDT) with efficient ROS generation. In addition to its simple fabrication process, HPS has other advantages such as excellent water solubility, strong NIR absorption, and high biocompatibility upon chemical functionalization for enhanced phototherapy. HPS exhibited high photodynamic performance against lung cancer and breast cancer cells by generating a large amount of singlet oxygen (1O2) under 654 nm laser irradiation. HPS accumulated into multiple organelles such as mitochondria and the endoplasmic reticulum and triggered cell apoptosis by laser exposure. In the tumor-bearing mice, in vivo, HPS showed an optimal half-life in circulation and achieved fluorescence-image-guided PDT within the irradiation window, resulting in effective tumor growth inhibition and the prolonged survival of animals. Moreover, the antitumor PDT effect of HPS was close to the clinical trial phase II stage of HPPH even at the low dosage of 0.32 mg/kg (under 75 J/cm2 laser), while the systemic safety of HPS was much higher. In conclusion, HPS is a novel water-soluble chlorin derivative with excellent PDT potential for clinical transformation.

Water Solubilization and Thermal Stimuli-Triggered Release of Porphyrin Derivatives Using Thermoresponsive Polysaccharide Hydroxypropyl Cellulose for Mitochondria-Targeted Photodynamic Therapy.

With minimal invasiveness and spatiotemporal therapeutic effects, photodynamic therapy is one of the most elegant strategies for achieving effective tumor therapy. Herein, a facile preparation and thermal process-triggered release of water-soluble photosensitizer 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP) has been developed using a thermoresponsive polysaccharide, hydroxypropyl cellulose. Current systems using hydroxypropyl cellulose enable manipulation of the loading capacity of THPP into a polymer matrix and the size of the complex by varying the temperature of the solution in preparation. Furthermore, current systems have enabled the release of THPP using a heating process, mimicking the surrounding of mitochondria, and have resulted in THPP potency as a mitochondria-targeted photodynamic therapy.

Fatty Acid Conjugates of Toluidine Blue O as Amphiphilic Photosensitizers: Synthesis, Solubility, Photophysics and Photochemical Properties†.

Toluidine blue O (TBO) is a water-soluble photosensitizer that has been used in photodynamic antimicrobial and anticancer treatments, but suffers from limited solubility in hydrophobic media. In an effort to incrementally increase TBO's hydrophobicity, we describe the synthesis of hexanoic (TBOC6) and myristic (TBOC14) fatty acid derivatives of TBO formed in low to moderate percent yields by condensation with the free amine site. Covalently linking 6 and 14 carbon chains led to modifications of not only TBO's solubility, but also its photophysical and photochemical properties. TBOC6 and TBOC14 derivatives were more soluble in organic solvents and showed hypsochromic shifts in their absorption and emission bands. The solubility in phosphate buffer solution was low for both TBOC6 and TBOC14, but unexpectedly slightly greater in the latter. Both TBOC6 and TBOC14 showed decreased triplet excited-state lifetimes and singlet oxygen quantum yields in acetonitrile, which was attributed to heightened aggregation of these conjugates particularly at high concentrations due to the hydrophobic "tails." While in diluted aqueous buffer solution, indirect measurements showed similar efficiency in singlet oxygen generation for TBOC14 compared to TBO. This work demonstrates a facile synthesis of fatty acid TBO derivatives leading to amphiphilic compounds with a delocalized cationic "head" group and hydrophobic "tails" for potential to accumulate into biological membranes or membrane/aqueous interfaces in PDT applications.

Photoinactivation of Escherichia coli with Water-Soluble Ammonium-Substituted Phthalocyanines.

Zinc(II) phthalocyanines (Pcs) peripherally decorated with 2,4,6-tris(dimethylaminomethyl)phenoxy groups (Pcs 1 and 3) and the corresponding quaternized derivatives (Pcs 2 and 4) were synthesized and their photodynamic inactivation (PDI) efficiency against recombinant bioluminescent Escherichia coli was examined. The photophysical data revealed that the presence of the ammonium units on the Pc structures promotes a redshift of the absorption bands when compared with the corresponding nonquaternized ones. The ammonium-substituted Pcs 2 and 4 showed excellent stability in dimethylformamide, moderate photostability, and increased efficiency to generate singlet oxygen (1O2). The water-soluble photosensitizers 2 and 4 at 5.0 μM exhibited a high photodynamic inactivation (PDI) efficiency against planktonic bioluminescent E. coli, reaching the detection limit of the methodology (a decrease of ∼4 log in the bioluminescence signal) after 210 min and 150 min under red light, delivered at a fluence rate of 135 mW·cm-2, respectively. Moreover, for the first time, it was accessed with the combined action of KI with ammonium-substituted Pcs. The addition of potassium iodide significantly improved the efficacy of Pc 2, which could reach the same inactivation rate after a short period of 5 min under the same irradiation conditions. The use of KI potentiates the PDI efficacy probably because of the generation of additional highly cytotoxic species during the photodynamic process which begins with the reaction of 1O2 with KI producing peroxyiodide species. The results of this work show that Pcs 2 and 4, with or without KI, can be considered as promising Pc dyes for the PDI of Gram-negative bacteria.

Synthesis of pH-Responsive Glycopolymer with End Group Zinc(II) Phthalocyanines as Potential Photosensitizer

A novel end-functionalized glycopolymer poly (3-O-methacryloyl-D-glucofuranose) -b-poly (2-Diethylaminoethyl Methacrylate) (PMAGlc-b-PDEA-ZnTAPc) with zinc (II) teraamaninophthalocyanine was synthesized. First, a pH-responsive copolymer PMAIpG-b-PDEA was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Then PMAIpG-b-PDEA reacted with ZnTAPc and deprotected to form a water-soluble and pH-responsive photosensitizer. The structure of the PMAGlc-b-PDEA-ZnTAPc was characterized by 1H NMR and GPC. The photophysical properties were evaluated by UV-Vis and fluorescence spectra. The PMAGlc-b-PDEA-ZnTAPc can generate singlet oxygen species with good singlet oxygen quantum yields (Φ△=0.38), which is believed to be the major cytotoxic reactive oxygen species (ROS) for photodynamic therapy. The ZnPc functionalized glycopolymer will be used as a potential photosensitizer in the fields of photodynamic therapy.

Unsymmetrical cationic porphyrin-cyclodextrin bioconjugates for photoinactivation of Escherichia coli.

Photodynamic inactivation (PDI) of microorganisms has been used for the treatment of bacterial infection. PDI is based on the combination of three non-toxic elements: a photosensitizer (PS), light and molecular oxygen, which lead to the formation of reactive oxygen species (ROS) that cause lethal oxidative damage into the target pathogenic bacteria. For that, clinical approved tetrapyrrolic macrocycles, with particular emphasis on photoactive porphyrin (Por) dyes, have been used as PS in PDI for different biomedical applications. Two novel unsymmetrical free-base thiopyridyl Pors conjugated with α- or γ-CD units (Pors 2 and 3) were prepared and the corresponding cationic ones (Pors 2a and 3a) were assessed as water-soluble photosensitizer (PS) agents by photophysical, photochemical and E. coli photobiological studies. The presence of the CD unit and the positive charges on the Por periphery (2a and 3a) enhance their solubility in aqueous media. The photoactivity of the two cationic Pors 2a and 3a ensures their potential as PDI drugs against Gram-negative bacteria model, a bioluminescent E. coli, which the best PDI efficiency was determined for Por 3a that achieved the highest bacterial reduction of 4.0 log10 (ANOVA, p < 0.0001), reaching the detection limit of the method after 15 min.

Self-assembling nanostructures of water-soluble fullerene[60]–chlorin e6 dyads: Synthesis, photophysical properties, and photodynamic activity

The synthesis of water-soluble dyads PFD-Chl(1), PFD-Chl(Zn) and PFD-Chl(2) based on a polyanionic fullerene[60] derivative PFD covalently linked to chlorin e6 was described. Photophysical properties, generation of superoxide and singlet oxygen in water and liposomes, and photodynamic activity on HeLa cancer cells of obtained dyads were analyzed. The significant influence of linker length between fullerene[60] core and dye, presence of metal (Zn) atom in chlorin moiety on photophysical properties, and photodynamic activity of the dyads was demonstrated. All dyads exhibit quenching of chlorin fluorescence by 7–120 times due to the electron transfer from the dye to fullerene and they formed nanoassociates in aqueous solutions with an effective radius in the range of 30–500 nm due to their pronounced amphiphilic properties. Such nanoassociates were able to effectively interact with membranes of liposomes, which led to a sharp increase of fluorescence signal. This effect could be applied for the design of various fullerene-based nanoscale switch-off systems. The dyad PFD-Chl(1) – with the shortest linker and metal-free dye – had the superoxide generation efficiency 5.6 and 3.4 times higher compared to free chlorin Се6 in water and liposomes, respectively, while its singlet oxygen generation was reduced. The phototoxicity of this dyad in HeLa cells was almost equal to that of the native chlorin, despite the reduction of singlet oxygen generation efficiency. Upon the incorporation of zinc atom into a chlorin moiety of this dyad, photodynamic activity and phototoxicity of PFD-Chl(Zn) dyad became negligible. The PFD-Chl(2) dyad – with the longest linker and metal-free chlorin – had about two times lower photodynamic activity and phototoxicity compared to Ce6 due to weak interaction between fullerene core and the dye. A significant increase of the type I pathway efficiency, demonstrated in the PFD-Chl(1) dyad, could be applied for the creation of photosensitizers, highly effective against hypoxic tumors. The demonstrated approach opens up vast opportunities for a directional design of highly efficient fullerene-based water-soluble photosensitizers for photodynamic therapy.