Search Results (94)

The search for effective and reliable methods of photosensitization of oxide-based semiconductor materials is of great significance for their use in photocatalytic reactions of hydrogen production and environmental remediation under natural sunlight. The present study is focused on partial substitution of titanium with manganese in the structure of layered perovskite-like titanate Na₂La₂Ti₃O₁₀, which was employed to yield a series of photocatalytically active materials, Na₂La₂Mn_xTi_3−xO₁₀ (x = 0.002–1.0), as well as their protonated forms H₂La₂Mn_xTi_3−xO₁₀ and nanosheets. It was established that the manganese cations Mn⁴⁺ are embedded in the middle sublayer of oxygen octahedra in the perovskite slabs La₂Mn_xTi_3−xO₁₀²⁻ and that the maximum achievable manganese content x in the products is ≈0.9. The partial cationic substitution in the perovskite sublattice led to a pronounced contraction of the optical band gap from 3.20 to 1.35 eV (depending on x) and, therefore, allowed the corresponding photocatalysts to utilize not only ultraviolet, but also visible and near-infrared light with wavelengths up to ≈920 nm. The materials obtained were tested as photocatalysts of hydrogen evolution from aqueous methanol, and the greatest activity in this reaction was demonstrated by the samples with low manganese contents (x = 0.002–0.01). However, the materials with greater substitution degrees may be of high interest for use in other photocatalytic processes and, especially, in thermophotocatalysis due to their improved ability to absorb the near-infrared part of solar radiation. Full article

Photooxidation imposes structural damage on proteins, and the amino acid tryptophan (Trp) is a key target for protein oxidation. The Trp radical cation (Trp^•⁺), as an oxidative product, can be reduced by plant phenols (φ-OH), a category of dietary phytochemicals essential for human health. This work is intended to investigate the efficacy of φ-OH regeneration of Trp from Trp^•⁺ as a function of φ-OH concentration and environmental pH. We have examined, by using laser flash photolysis, six different kinds of φ-OH in the aqueous system consisting of Trp and riboflavin as a photosensitizer. Taking syringic acid (Syr) as an example, upon systematically varying the pH from 2 to 10, the partition of Syr phenolate, Syr-O²⁻, increases from 0% to 70% and, accordingly, the rate of Trp regeneration increases from 4.8 × 10⁶ M⁻¹·s⁻¹ to 1.7 × 10⁸ M⁻¹·s⁻¹. It is found that the regeneration rate correlates with the driving force of the electron transfer (ET) reaction between φ-OH and Trp^•+, which can be well accounted for by Marcus’s ET theory (R² = 0.89). The λ = 0.43 ± 0.08 eV for the reorganization energy for ET from the plant phenols to the Trp^•⁺. The effects of φ-OH concentration, environmental pH, and ET driving force on the Trp regeneration reaction herein revealed are significant for enlightening further study of protein (anti)oxidation. Full article

Porphyrins serve as photosensitizers (PS) in the realm of cancer photodynamic therapy (PDT). Upon excitation by laser light, porphyrins are capable of converting molecular oxygen into highly cytotoxic singlet oxygen (¹O₂). However, the rigid π-conjugated structure of porphyrins frequently results in the formation of aggregates in aqueous solutions, which leads to the self-quenching of the excited state. Cucurbit[n]urils exhibit the capacity to stably bind with porphyrins via host–guest interactions, effectively inhibiting their aggregation and potentially enhancing the therapeutic efficacy of PDT. In this study, water-soluble tetramethyl cucurbit[6]uril (TMeQ[6]) was selected as the host, while four propionic acid group-appended porphyrin cationic (TPPOR) was utilized as guests to construct a supramolecular photosensitizer (TPPOR-2TMeQ[6]) in a molar ratio of 2:1. Further experimental findings demonstrate that the presence of TMeQ[6] inhibits the aggregation of TPPOR through non-covalent interactions. This inhibition reduces the energy difference between the excited singlet and triplet states, thereby enhancing the conversion efficiency of ¹O₂. Moreover, TPPOR-2TMeQ[6] exhibits favorable biocompatibility and minimal dark toxicity against breast cancer cells (4T1). Upon intracellular excitation, the levels of reactive oxygen species (ROS) significantly increase, inducing oxidative stress in 4T1 cells and leading to apoptosis. Consequently, the findings of this study suggest that the enhanced photosensitization achieved through this supramolecular approach is likely to promote the anticancer therapeutic effects of PDT, thereby broadening the application prospects of porphyrins within PDT systems. Full article

The development of biomaterials with gradient surface modification capable of spatially controlled cell adhesion and migration is of great importance for tissue engineering and regeneration. In this study, we proposed a method for the covalent modification of PLA-based materials with a cationic polypeptide (polylysine, PLys) via a thiol-ene click reaction carried out under a light gradient. With this aim, PLA-based films were fabricated and modified with 2–aminoethyl methacrylate (AEMA) as a double bond source. The latter was introduced by reacting pre-formed and activated surface carboxyl groups with the amino group of AEMA. The success of the modification was confirmed by ¹H NMR, Raman and X-ray photoelectron spectroscopy data. A further photoinduced thiol-ene click reaction in the presence of a photosensitive initiator as a radical source was further optimized using cysteine. For grafting of PLys via the thiol-ene click reaction, PLys with a terminal thiol group was synthesized by ring-opening polymerization using Cys(Acm) as an amine initiator. Deprotection of the polypeptide resulted in the formation of free thiol groups of Cys-PLys. Successful gradient grafting of Cys-PLys was evidenced by covalent staining with the fluorescent dye Cy3-NHS. In addition, PLys gradient-dependent adhesion and migration of HEK 293 cells on PLys-PLA-based surfaces was confirmed. Full article

Photodynamic therapy is expected to be a less invasive treatment, and strategies for targeting mitochondria, the main sources of singlet oxygen, are attracting attention to increase the efficacy of photodynamic therapy and reduce its side effects. To date, we have succeeded in encapsulating the photosensitizer rTPA into MITO-Porter (MP), a mitochondria-targeted Drug Delivery System (DDS), aimed at mitochondrial delivery of the photosensitizer while maintaining its activity. In this study, we report the results of our studies to alleviate rTPA aggregation in an effort to improve drug efficacy and assess the usefulness of modifying the rTPA side chain to improve the mitochondrial retention of MITO-Porter, which exhibits high therapeutic efficacy. Conventional rTPA with anionic side chains and two rTPA analogs with side chains that were converted to neutral or cationic side chains were encapsulated into MITO-Porter. Low-MP (MITO-Porter with Low Drug/Lipid) exhibited high drug efficacy for all three types of rTPA, and in Low-MP, charged rTPA-encapsulated MP exhibited high drug efficacy. The cellular uptake and mitochondrial translocation capacities were similar for all particles, suggesting that differences in aggregation rates during the incorporation of rTPA into MITO-Porter resulted in differences in drug efficacy. Full article

The global antibiotic resistance crisis has drawn attention to the development of treatment methods less prone to inducing drug resistance, such as antimicrobial photodynamic therapy (aPDT). However, there is an increasing demand for new photosensitizers capable of efficiently absorbing in the near-infrared (NIR) region, enabling antibacterial treatment in deeper sites. Additionally, advanced strategies need to be developed to avert drug resistance stemming from prolonged exposure. Herein, we have designed a conjugated oligoelectrolyte, namely TTQAd, with a donor-acceptor-donor (D-A-D) backbone, enabling the generation of reactive oxygen species (ROS) under NIR light irradiation, and cationic adamantaneammonium groups on the side chains, enabling the host-guest interaction with curcubit[7]uril (CB7). Due to the amphiphilic nature of TTQAd, it could spontaneously form nanoassemblies in aqueous solution. Upon CB7 treatment, the positive charge of the cationic adamantaneammonium group was largely shielded by CB7, leading to a further aggregation of the nanoassemblies and a reduced antibacterial efficacy of TTQAd. Subsequent treatment with competitor guests enables the release of TTQAd and restores its antibacterial effect. The reversible supramolecular switch for regulating the antibacterial effect offers the potential for the controlled release of active photosensitizers, thereby showing promise in preventing the emergence of drug-resistant bacteria. Full article

Employing naturally extracted dyes and their derivatives as photosensitizers towards the construction of dye-sensitized solar cells (DSSCs) has been recently emerging for establishing sustainable energy conversion devices. In this present work, Rhodobacter Sphaeroides Photobacteria (Rh. Sphaeroides) was used as a natural source from which Bacteriopheophytine-a (Bhcl) dye was extracted. Further, two cationic derivatives of Bhcl, viz., Guanidino-bacteriopheophorbide-a (Gua-Bhcl) and (2-aminoethyl)triphenylphosphono-bacteriopheophorbide-a (2AETPPh-Bhcl) were synthesized. The thus obtained Bhcl, Gua-Bhcl and 2AETPPh-Bhcl were characterized using liquid chromatography–mass spectrometry (LC–MS) and their photophysical properties were investigated using excitation and emission studies. All three near-infrared (NIR) responsive dyes were employed as natural sensitizers towards the construction of DSSC devices, using platinum as a photocathode, dye-sensitized P25-TiO₂ as a photoanode and I⁻/I₃⁻ as an electrolyte. DSSCs fabricated using all three dyes have shown reasonably good photovoltaic performance, among which 2AETPPh-Bhcl dye has shown a relatively higher power conversion efficiency (η) of 0.38% with a short circuit photocurrent density (J_SC) of 1.03 mA cm⁻². This could be attributed to the dye’s natural optimal light absorption in the visible and NIR region and uniform dispersion through the electrostatic interaction of the cationic derivatives on the TiO₂ photoanode. Furthermore, the atomic force microscopy studies and electrochemical investigations using cyclic voltammetry, electrochemical impedance spectroscopy and Bode’s plot also supported the enhancement in performance attained with 2AETPPh-Bhcl dye. Full article

The most important area of modern pharmacology is the targeted delivery of drugs, and one of the most promising classes of chemical compounds for creating drugs of this kind are the photochromic spiropyrans, capable of light-controlled biological activity. This work is devoted to the synthesis and study of the photochromic properties of new triphenylphosphonium salts of spiropyrans. It was found that all the synthesized cationic spiropyrans have high photosensitivity, increased resistance to photodegradation and the ability for photoluminescence. Full article

In this investigation, a multifunctional visible-light TX-based photosensitizer containing a siloxane moiety (TXS) was designed with a good overall yield of 54%. The addition of a siloxane moiety enabled the incorporation of a TX photosensitizer into a siloxane network by photoinduced sol–gel chemistry, thus avoiding its release. Both liquid ¹H and solid-state ²⁹Si NMR measurements undeniably confirmed the formation of photoacids resulting from the photolysis of the TXS/electron acceptor molecule (Iodonium salt), which promoted the photoinduced hydrolysis/condensation of the trimethoxysilane groups of TXS, with a high degree of condensation of its inorganic network. Notably, the laser flash photolysis, fluorescence, and electron paramagnetic resonance spin-trapping (EPR ST) experiments demonstrated that TXS could react with Iod through an electron transfer reaction through its excited states, leading to the formation of radical initiating species. Interestingly, the TXS/Iod was demonstrated to be an efficient photoinitiating system for free-radical (FRP) and cationic (CP) polymerization under LEDs@385, 405, and 455 nm. In particular, whatever the epoxy monomer mixtures used, remarkable final epoxy conversions were achieved up to 100% under air. In this latter case, we demonstrated that both the photoinduced sol–gel process (hydrolysis of trimethoxysilane groups) and the cationic photopolymerization occurred simultaneously. Full article

Photodynamic inactivation (PDI) is an emerging therapeutic approach that can effectively inactivate diverse microbial forms, including vegetative forms and spores, while preserving host tissues and avoiding the development of resistance to the photosensitization procedure. This study evaluates the antifungal and sporicidal photodynamic activity of two water-soluble amphiphilic tetra- and octa-β-substituted zinc(II) phthalocyanine (ZnPc) dyes with dimethylaminopyridinium groups at the periphery (ZnPcs 1, 2) and their quaternized derivatives (ZnPcs 1a, 2a). Tetra(1, 1a)- and octa(2, 2a)-β-substituted zinc(II) phthalocyanines were prepared and assessed as photosensitizers (PSs) for their effects on Fusarium oxysporum conidia. Antimicrobial photoinactivation experiments were performed with each PS at 0.1, 1, 10, and 20 µM under white light irradiation at an irradiance of 135 mW·cm^–2, for 60 min (light dose of 486 J·cm⁻²). High PDI efficiency was observed for PSs 1a, 2, and 2a (10 µM), corresponding to inactivation until the method’s detection limit. PS 1 (20 µM) also achieved a considerable reduction of >5 log₁₀ in the concentration of viable conidia. The quaternized PSs (1a, 2a) showed better PDI performance than the non-quaternized ones (1, 2), even at the low concentration of 1 µM, and a light dose of 486 J·cm⁻². These cationic phthalocyanines are potent photodynamic drugs for antifungal applications due to their ability to effectively inactivate resistant forms, like conidia, with low concentrations and reasonable energy doses. Full article

Singlet oxygen (¹O₂), representing an important reactive oxygen species, has promising applications in biomedical, material, and environmental sciences. Photosensitized production of ¹O₂ using organic dyes is highly desirable and the exploration of highly efficient photosensitizers has received considerable attention. Herein, two tridentate Pt(II) complexes, i.e., cationic 1(PF₆) and neutral 2, modified with the ethynylnaphthalimide chromophore, were designed and prepared for the application in ¹O₂ generation. Spectroscopic studies and computational results suggest that 1(PF₆) and 2 display the lowest-energy absorption bands centered at 435–465 nm with the molar extinction coefficients of 0.6–3.2 × 10⁴ M⁻¹ cm⁻¹, originating from the singlet ligand-to-ligand charge transfer (¹LLCT) and a mixture of ¹LLCT and singlet ligand-centered (LC) transitions, respectively. Moreover, they show similar phosphorescence at 620–640 nm assigned to the Pt-perturbed triplet LC emission of the ethynylnaphthalimide moiety. Thanks to the relatively long phosphorescence lifetimes, these complexes exhibit O₂-dependent phosphorescence intensities with good reversibility and stability. They are able to behave as efficient triplet photosensitizers to promote the ¹O₂ generation with high quantum yields (84–89%). This work indicates that the combination of an organic chromophore with Pt(II) complexes provides an effective method to obtain photosensitizers for ¹O₂ generation. Full article

During the last decades, multicomponent photoinitiating systems have been the focus of intense research efforts, especially for the design of visible light photoinitiating systems. Although highly reactive three-component and even four-component photoinitiating systems have been designed, the complexity to elaborate such mixtures has incited researchers to design monocomponent Type II photoinitiators. Using this approach, the photosensitizer and the radical/cation generator can be combined within a unique molecule, greatly simplifying the elaboration of the photocurable resins. In this field, sulfonium salts are remarkable photoinitiators but these structures lack absorption in the visible range. Over the years, various structural modifications have been carried out in order to redshift their absorptions in the visible region. In this work, an overview of the different sulfonium salts activable under visible light and reported to date is proposed. Full article

Antimicrobial photodynamic inactivation is considered a promising antimicrobial approach that may not develop resistance in the near future. Here, we investigate the influence of the photosensitizer chlorophyllin (CHL) and the cationic permeabilizer polyethylenimine (PEI), exposed to a red light-emitting diode, on the human pathogen Pseudomonas aeruginosa free-living planktonic cells, the sessile biofilm and persister cells. The broth microdilution checkerboard method was used to test antimicrobial susceptibility. As a substrate for biofilms, the Calgary biofilm device was used, and the quantification of the biofilm biomass was carried out using a crystal violet assay. Serine hydroxamate was used for the induction of persisters. Our findings reveal that PEI ameliorates the antimicrobial activity of CHL against P. aeruginosa planktonic and biofilm states, and the concentration required to eradicate the bacteria in the biofilm is more than fourfold that is required to eradicate planktonic cells. Interestingly, the persister cells are more susceptible to CHL/PEI (31.25/100 µg mL⁻¹) than the growing cells by 1.7 ± 0.12 and 0.4 ± 0.1 log₁₀ reduction, respectively, after 15 min of illumination. These data demonstrate that CHL excited with red light together with PEI is promising for the eradication of P. aeruginosa, and the susceptibility of P. aeruginosa to CHL/PEI is influenced by the concentrations and the exposure time. Full article

Photodynamic therapy facilitates the selective destruction of cancer tissue by utilizing a photosensitizer drug, the light near the absorbance wavelength of the drug, and oxygen. Methylene Blue, 5-aminolevulinic acid (the precursor of the photosensitizer, protoporphyrin IX), porphyrin, Foscan, Chlorin e6, and HPPH have been used successfully as photosensitizers in the treatment of oral verrucous hyperplasia, oral leukoplakia, oral lichen planus, and head and neck squamous cell carcinoma. “Theranostic” liposomes can deliver a contrast agent for magnetic resonance imaging and a photosensitizer for the image-guided photodynamic therapy of head and neck cancer. Liposomes incorporating photosensitizers can be targeted to cell surface markers overexpressed on cancer cells. Novel porphyrinoids have been developed in our laboratories that are highly effective as photosensitizers. Tribenzoporphyrazines encapsulated in cationic liposomes have produced IC₅₀ values up to 50 times lower compared to the free photosensitizers. It is anticipated that targeting these drugs to cancer stem cells, using upconversion nanoparticles for the near-infrared irradiation of tumors to activate the photosensitizers, and overcoming tumor hypoxia will enhance the efficacy of photodynamic therapy of tumors accessible to light sources. Full article

The straightforward synthesis of three cationic boron-dipyrromethene (BODIPY) derivatives and their mitochondria-targeting and photodynamic therapeutic (PDT) capabilities are reported. Two cancer cell lines (HeLa and MCF-7) were used to investigate the PDT activity of the dyes. Compared to their non-halogenated counterparts, halogenated BODIPY dyes exhibit lower fluorescence quantum yields and enable the efficient production of singlet oxygen species. Following LED light irradiation at 520 nm, the synthesized dyes displayed good PDT capabilities against the treated cancer cell lines, with low cytotoxicity in the dark. In addition, functionalization of the BODIPY backbone with a cationic ammonium moiety enhanced the hydrophilicity of the synthesized dyes and, consequently, their uptake by the cells. The results presented here collectively demonstrate the potential of cationic BODIPY-based dyes as therapeutic drugs for anticancer photodynamic therapy. Full article