Photophysics and photochemistry of photodynamic therapy: fundamental aspects

Multicationic ruthenium phthalocyanines as photosensitizers for photodynamic inactivation of multiresistant microbes

Four photosensitizers PS1a-PS4a consisting in multicationic ruthenium(II) phthalocyanines (RuPcs) have been evaluated in photodynamic inactivation (PDI) of multiresistant microorganisms. The RuPcs, bearing from 4 to 12 terminal ammonium salts, have been designed to target the microorganisms cytoplasmic cell membrane and display high singlet oxygen quantum yields. In addition, PS3a and PS4a were conceived to exhibit multi-target localization by endowing them with amphiphilic character, using two different structural approaches. Under low light regimes, the two hydrophilic PS1a and PS2a, as well as the amphiphilic PS3a show much stronger response against Gram-positive MRSA than that observed for the typical phthalocyanines designed for PDI, namely zinc(II) and palladium(II) complexes, as well as free-base Pcs. Besides, PS1a, PS2a and PS3a show remarkably high activity against the Gram-negative E. coli, although weak fungicidal character against fluconazole-resistant C. albicans. Contrasting, the structurally different, amphiphilic PS4a shows only slight activity for Gram-positive bacteria, despite its ability to cross cell membrane and reach internal organelles. Still, PS4a shows a positive synergistic effect against MRSA when combined with doxycycline, exhibiting an increased activity from about 1.5 to about 4.9 log reduction under the light dose of 30 J/cm2 and the 0.125 mg/L subinhibitory dose of doxycycline.

Single-Photon DNA Photocleavage up to 905 nm by a Benzylated 4-Quinolinium Carbocyanine Dye

This paper describes the DNA interactions of near-infrared (NIR) benzylated 4-quinolinium dicarbocyanine dyes containing a pentamethine bridge meso-substituted either with a bromine (4) or hydrogen (5) atom. In pH 7.0 buffered aqueous solutions, the 4-quinolinium dyes absorb light that extends into the near-infrared range up to ∼950 nm. The unique direct strand breakage of pUC19 DNA that is sensitized by irradiating either dicarbocyanine with an 850 nm LED laser constitutes the first published example of DNA photocleavage upon single-photon chromophore excitation at a wavelength greater than 830 nm. Brominated dye 4, which is more stable than and achieves DNA strand scission in higher yield than its hydrogen-bearing counterpart 5, cleaves plasmid DNA under 830 and 905 nm laser illumination. The addition of increasing amounts of DNA to aqueous pH 7.0 solutions converted an aggregated form of dye 4 to a monomer with bathochromic absorption that overlaps all three laser emission wavelengths. No induced circular dichroism and fluorescence signals were detected when DNA was present, pointing to possible external binding of the dye to the DNA. Experiments employing radical-specific fluorescent probes and chemical additives showed that brominated dye 4 likely breaks DNA strands by photosensitizing hydroxyl radical production. Micromolar concentrations of the dye were relatively nontoxic to cultured Escherichia coli cells in the dark but dramatically reduced survival of the cells under 830 nm illumination. As NIR light wavelengths deeply penetrate biological tissues, we envisage the future use of carbocyanine dyes as a sensitizing agent in phototherapeutic applications.

Photoantimicrobial anthraquinones in Australian fungi of the genus Cortinarius

Dermocyboid Cortinarius species of both hemispheres are usually intensely colored and known to contain anthraquinones. Australian dermocyboid fungi have distinct evolutionary histories which are clearly different from Northern Hemisphere species of similar appearance. Allopatric speciation often results in different metabolic adaptations. We were especially interested in the diversity of anthraquinonic pigments and in their photoantimicrobial potential. In this study 33 dried samples from eighteen Australian dermocyboid Cortinarius taxa were extracted with methanol and analyzed via HPLC-DAD-MS. The 9,10-dimethylanthracene (DMA) assay was used to measure the extracts' ability to produce singlet oxygen after irradiation. Furthermore, a photoantimicrobial screening method based on the protocols of Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility (EUCAST), employing the common human pathogens Candida albicans, Escherichia coli, and Staphylococcus aureus was used to identify photoantimicrobials. Based on chromatography, mass spectrometry, and UV/Vis data, peaks were annotated according to literature and in-house data. A chemotaxonomic pigment analysis was established to cluster the species according to their major anthraquinones and to allow identification of the groups by a minimum number of pigments. In agreement with the recorded pigment pattern of the photoactive anthraquinones, nine Cortinarius species (C. alienatus, C. atropurpureus, C. austrovenetus, C. basirubescens, C. canarius, C. clelandii 2, C. globuliformis, C. persplendidus 1, C. sp. "honey pileus 1") showed at least 70 % inhibition of Staphylococcus aureus (Gram-positive bacteria) growth under light irradiation (λ = 428 / 478 nm, H = 30 J/cm2, c = 50 μg/mL, pre-illumination time (tPI) = 60 min) in the photoantimicrobial screening. The extracts of three species (C. alienatus, C. austrovenetus, and C. clelandii 2) showed additional photoactivity against Candida albicans (yeast) under the same conditions. Several relevant (photo)antimicrobials were identified: Emodin, dermocybin, skyrin, physcion (synonym: parietin), 7,7'-biphyscion, and hypericin; From the photoactive extracts, that were not reported to contain photoactive compounds before, austrocortinin and xanthorin were isolated and used for further testing. For austrocortinin a singlet oxygen yield of 0.03 (reference: [Ru(bpy3)Cl2], d4-MeOH) was detected. Accordingly, the anthraquinone did not show activity in the photoantimicrobial assay. Xanthorin, with a singlet oxygen yield of 0.10, led to an inhibition of growth of 78.1 % against Staphylococcus aureus (4.00 μg/mL, λ = 428 nm, 30 J/cm2, tPI = 60 min).

AIEgen-self-assembled nanoparticles with anti-PD-L1 antibody functionalization realize enhanced synergistic photodynamic therapy and immunotherapy against malignant melanoma

Immune checkpoint inhibitors (ICIs) become integral in clinical practice, yet their application in cancer therapy is constrained by low overall response rates and the primary resistance of cancers to ICIs. Herein, this study proposes aggregation-induced emission (AIE)-based nanoparticles (NPs) for a more effective and synergistic approach combining immunotherapy and photodynamic therapy (PDT) to achieve higher responses than anti-PD-L1 monotherapy. The TBP@aPD-L1 NPs are constructed by functionalizing azide group-modified TBP-2 (TBP-N3) with anti-PD-L1 antibodies via the DBCO-S-S-PEG2000-COOH linker. The anti-PD-L1 target the tumor cells and promote the TBP-N3 accumulation in tumors for enhanced PDT. Notably, the TBP-N3, featuring aggregation-induced emission, boosts reactive oxygen species (ROS) generation through both type I and type II processes for enhanced PDT. The TBP@aPD-L1-mediated PDT induces more powerful effects of direct tumor cell-killing and further elicits effective immunogenic cell death (ICD), which exerts anti-tumor immunity by activating T cells for ICI treatment and reshapes the tumor immune microenvironment (TIME), thereby enhancing the efficacy of PD-L1 blockade of anti-PD-L1. Consequently, TBP@aPD-L1 NPs demonstrated significantly enhanced inhibition of tumor growth in the mouse model of malignant melanoma (MM). Our NPs act as a facile and effective drug delivery platform for enhanced immunotherapy combined with enhanced PDT in treating MM.

Analysis of Singlet Oxygen Luminescence Generated By Protoporphyrin IX

The effectiveness of photodynamic therapy (PDT) for cancer treatment relies on the generation of cytotoxic singlet oxygen (1O2) in type II PDT. Hence, monitoring of 1O2 generation during PDT enables optimal treatment delivery to the tumor target with reduced off-target effects. Direct 1O2 observation by measuring its luminescence at 1270 nm remains challenging due to the very weak signal. This study presents 1O2 luminescence measurements using a time-resolved singlet oxygen luminescence detection system (TSOLD) applied to protoporphyrin IX (PpIX) in different solvents (ethanol and acetone) and biological media (bovine serum albumin and agarose-based solid phantom). The compact experimental setup includes a nanosecond diode laser with a function generator, a cuvette with photosensitizer solution, optical filtering and mirrors, an InGaAs single-photon avalanche diode detector, and time-tagger electronics. Increasing the concentration of PpIX in these media from 1 to 10 µg/g resulted in a 3-5 × increase in the 1O2 luminescence signal. Furthermore, increasing light scattering in the sample using Intralipid from 0.1 to 1% led to a decrease in the 1O2 luminescence signal and lifetime. These results confirm the marked effect of the microenvironment on the 1O2 signal and, hence, on the photodynamic efficacy.

Impact of the hydrophilic-lipophilic balance of free-base and Zn(II) tricationic pyridiniumporphyrins and irradiation wavelength in PDT against the melanoma cell lines

The amphiphilic and asymmetric structure of porphyrins, when used as photosensitizers (PSs) for photodynamic therapy (PDT), has been shown through numerous previous studies to be a very important property that facilitates their entry into cells, which improves their efficiency in PDT. In this work, two groups of cationic AB3 pyridiniumporphyrins, free-base and chelated with Zn(II), both substituted with alkyl chains of various lengths, were studied in PDT on melanoma cell lines. The aim was to investigate the impact of hydrophilic-lipophilic balance and Zn(II) chelation, and the importance of matching the irradiation wavelength to the optical properties of the PS on in vitro PDT efficiency. Therefore, spectroscopic studies, singlet oxygen production and lipophilicity as well as cellular uptake, localization and cytotoxicity studies of the two series of porphyrins were performed. In both series of porphyrins, the longest alkyl chain (17 C-atoms long) enables the greatest internalization of the PS. Chelation with Zn(II) resulted in better physicochemical properties, but slower cellular internalization. As expected, free-base porphyrins were more PDT efficient than their Zn(II) complexes after 30-min photoactivation by low-fluence (2 mW/cm2) red light (643 nm). However the use of orange light (606 nm) with the same fluence rate was more suitable for Zn(II) porphyrins and resulted in similar overall toxicity to their free-base analogues with similar lipophilicity. Although the highest phototoxicity was achieved with the PSs carrying the longest alkyl chain, TMPyP3-C13H27 and Zn(II)-TMPyP3-C13H27 proved to be the most promising candidates for use in PDT as they exhibit high phototoxicity, but also greater selectivity towards melanoma cell lines (MeWo and A375) compared to fibroblasts (HDF).

Microtubule-Targeting NAP Peptide-Ru(II)-polypyridyl Conjugate As a Bimodal Therapeutic Agent for Triple Negative Breast Carcinoma

Triple-negative breast cancer (TNBC) poses significant treatment challenges due to its high metastasis, heterogeneity, and poor biomarker expression. The N-terminus of an octapeptide NAPVSIPQ (NAP) was covalently coupled to a carboxylic acid derivative of Ru(2,2'-bipy)32+ (Rubpy) to synthesize an N-stapled short peptide-Rubpy conjugate (Ru-NAP). This photosensitizer (PS) was utilized to treat TNBC through microtubule (MT) targeted chemotherapy and photodynamic therapy (PDT). Ru-NAP formed more elaborate molecular aggregates with fibrillar morphology as compared to NAP. A much higher binding affinity of Ru-NAP over NAP toward β-tubulin (KRu-NAP: (6.8 ± 0.55) × 106 M-1; KNAP: (8.2 ± 1.1) × 104 M-1) was observed due to stronger electrostatic interactions between the MT with an average linear charge density of ∼85 e/nm and the cationic Rubpy part of Ru-NAP. This was also supported by docking, simulation, and appropriate imaging studies. Ru-NAP promoted serum stability, specific binding of NAP to the E-site of the βIII-tubulin followed by the disruption of the MT network, and effective singlet oxygen generation in TNBC cells (MDA-MB-231), causing cell cycle arrest in the G2/M phase and triggering apoptosis. Remarkably, MDA-MB-231 cells were more sensitive to Ru-NAP compared to noncancerous human embryonic kidney (HEK293 cells) when exposed to light (LightIC50Ru-NAP[HEK293]: 17.2 ± 2.5 μM, compared to LightIC50Ru-NAP[MDA-MB-231]: 32.5 ± 7.8 nM, DarkIC50Ru-NAP[HEK293]: > 80 μM, compared to DarkIC50Ru-NAP[MDA-MB-231]: 2.9 ± 0.5 μM). Ru-NAP also effectively inhibited tumor growth in MDA-MB-231 xenograft models in nude mice. Our findings provide strong evidence that Ru-NAP has a potential therapeutic role in TNBC treatment.

Prediction of Pt, Ir, Ru, and Rh complexes light absorption in the therapeutic window for phototherapy using machine learning

Effective light-based cancer treatments, such as photodynamic therapy (PDT) and photoactivated chemotherapy (PACT), rely on compounds that are activated by light efficiently, and absorb within the therapeutic window (600-850 nm). Traditional prediction methods for these light absorption properties, including Time-Dependent Density Functional Theory (TDDFT), are often computationally intensive and time-consuming. In this study, we explore a machine learning (ML) approach to predict the light absorption in the region of the therapeutic window of platinum, iridium, ruthenium, and rhodium complexes, aiming at streamlining the screening of potential photoactivatable prodrugs. By compiling a dataset of 9775 complexes from the Reaxys database, we trained six classification models, including random forests, support vector machines, and neural networks, utilizing various molecular descriptors. Our findings indicate that the Extreme Gradient Boosting Classifier (XGBC) paired with AtomPairs2D descriptors delivers the highest predictive accuracy and robustness. This ML-based method significantly accelerates the identification of suitable compounds, providing a valuable tool for the early-stage design and development of phototherapy drugs. The method also allows to change relevant structural characteristics of a base molecule using information from the supervised approach.Scientific Contribution: The proposed machine learning (ML) approach predicts the ability of transition metal-based complexes to absorb light in the UV-vis therapeutic window, a key trait for phototherapeutic agents. While ML models have been used to predict UV-vis properties of organic molecules, applying this to metal complexes is novel. The model is efficient, fast, and resource-light, using decision tree-based algorithms that provide interpretable results. This interpretability helps to understand classification rules and facilitates targeted structural modifications to convert inactive complexes into potentially active ones.

ROS-mediated Therapeutics Combined with Metal-based Porphyrin Nanoparticles and their Applications in Tumor Treatment

High concentrations of reactive oxygen species (ROS) can disrupt cell structure and induce apoptosis and necrosis of tumor cells. Photodynamic therapy (PDT) and chemodynamic therapy (CDT) are two cancer treatments mediated by reactive oxygen species. Oxygen molecules (O2) are one of the indispensable factors in PDT and hypoxic tumor sites limit its application. However, another ROS-mediated method, CDT, can generate •OH and O2in situ by Fenton reaction or Fenton-like reaction. Synergistic PDT/CDT therapy is a strategy to overcome the limitations of tumor microenvironment therapy. In this review, PDT and CDT therapies are briefly introduced, with an emphasis on metal-basrd porphyrin nanoparticles constructed in different ways for PDT/CDT dual-mode therapy. By introducing the history and latest design schemes of the treatment model, it provides ideas for researchers engaged in ROS-mediated cancer therapies.

Unravelling the modes of phototoxicity of NIR absorbing chlorophyll derivative in cancer cells under normoxic and hypoxic conditions

The efficacy of photodynamic treatment (PDT) against deep-seated tumor is hindered by low penetration depth of light as well as hypoxic conditions which prevails in tumor. To overcome this limitation, Near-infrared (NIR) absorbing photosensitizers have been investigated actively. In the present study we evaluated the PDT efficacy of an NIR absorbing chlorophyll derivative 'Cycloimide Purpurin-18 (CIPp-18)' in Human Breast carcinoma (MCF-7) and cervical adenocarcinoma (Hela) cells under normoxic and hypoxic conditions. PDT with CIPp-18 (2.0 µM, 3 h) and NIR light (700 ± 25 nm, 0.36-1.4 J /cm2) induced potent phototoxicity in both the cell lines. Under hypoxic conditions, PDT induced ~ 32% and 42% phototoxicity at LD50 and LD70 light dose, respectively, which corresponds to phototoxic dose under normoxia. CIPp-18 in neat buffer (pH 7.4) showed generation of singlet oxygen (1O2) as well as superoxide (O2·-) radicals. Studies on ROS generation in cells using fluorescence probes and the effect of mechanistic probes of 1O2 (Sodium Azide, Histidine, D2O) and free radicals (DMSO, Mannitol, Cyanocobalamin, SOD-PEG) on phototoxicity show that 1O2 plays major role in phototoxicity under normoxia. Whereas, under hypoxic conditions, PDT led to no significant generation of ROS and phototoxicity remained unaffected by cyanocobalamin, a quencher of O2·-. Moreover, CIPp-18 showed localization in cell membrane and PDT led to more pronounced loss of membrane permeability in cells under hypoxia than for normoxia. These results demonstrate that CIPp-18 is suitable for PDT of cancer cells under hypoxia and also suggest that phototoxicity under hypoxia is mediated via ROS-independent contact-dependent mechanism.

Shift of cell-death mechanisms in primary human neutrophils with a ruthenium photosensitizer

Primary human neutrophils are the most abundant human white blood cells and are central for innate immunity. They act as early responders at inflammation sites, guided by chemotactic gradients to find infection or inflammation sites. Neutrophils can undergo both apoptosis as well as NETosis. NETosis is a form of neutrophil cell death that releases chromatin-based extracellular traps (NETs) to capture and neutralize pathogens. Understanding or controlling the balance between these cell-death mechanisms is crucial. In this study, the chemical synthesis and biologic assessment of a ruthenium complex as a light-activated photosensitizer that creates reactive oxygen species (ROS) in primary human neutrophils is reported. The ruthenium complex remains non-toxic in the dark. However, upon exposure to blue light at 450 nm, it exhibits potent cytotoxic effects in both cancerous and non-cancerous cell lines. Interestingly, the metal complex shifts the cell-death mechanism of primary human neutrophils from NETosis to apoptosis. Cells irradiated directly by the light source immediately undergo apoptosis, whereas those further away from the light source perform NETosis at a slower rate. This indicates that high ROS levels trigger apoptosis and lower ROS levels NETosis. The ability to control the type of cell death undergone in primary human neutrophils could have implications in managing acute and chronic infectious diseases.

Engineering Radiocatalytic Nanoliposomes with Hydrophobic Gold Nanoclusters for Radiotherapy Enhancement

Chemoradiation therapy is on the forefront of pancreatic cancer care, and there is a continued effort to improve its safety and efficacy. Liposomes are widely used to improve chemotherapy safety, and may accurately deliver high-Z element- radiocatalytic nanomaterials to cancer tissues. In this study, the interaction between X-rays and long-circulating nanoliposome formulations loaded with gold nanoclusters is explored in the context of oxaliplatin chemotherapy for desmoplastic pancreatic cancer. Hydrophobic gold nanoclusters stabilized with dodecanethiol (AuDDT) are efficiently incorporated in nanoliposomal bilayers. AuDDT-nanoliposomes significantly augmented radiation-induced •OH production, which is most effective with monochromatic X-rays at energies that exceed the K-shell electron binding energy of Au (81.7 keV). Cargo release assays reveal that AuDDT-nanoliposomes can permeabilize lipid bilayers in an X-ray dose- and formulation-dependent manner. The radiocatalytic effect of AuDDT-nanoliposomes significantly augments radiotherapy and oxaliplatin-chemoradiotherapy outcomes in 3D pancreatic microtumors. The PEGylated AuDDT-nanoliposomes display high tumor accumulation in an orthotopic mouse model of pancreatic cancer, showing promise for nanoliposomes as carriers for radiocatalytic nanomaterials. Altogether, compelling proof for chemo-radiation dose-enhancement using AuDDT-nanoliposomes is presented. Further improving the nanoliposomal loading of high-Z elements will advance the safety, efficacy, and translatability of such chemoradiation dose-enhancement approaches.

A Comprehensive Study of Reactive Oxygen Species Explicit Dosimetry for Pleural Photodynamic Therapy

Photodynamic therapy (PDT) relies on the interactions between light, photosensitizers, and tissue oxygen to produce cytotoxic reactive oxygen species (ROS), primarily singlet oxygen (1O2) through Type II photochemical reactions, along with superoxide anion radicals (O2•-), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH) through Type I mechanisms. Accurate dosimetry, accounting for all three components, is crucial for predicting and optimizing PDT outcomes. Conventional dosimetry tracks only light fluence rate and photosensitizer concentration, neglecting the role of tissue oxygenation. Reactive oxygen species explicit dosimetry (ROSED) quantifies the reacted oxygen species concentration ([ROS]rx) by explicit measurements of light fluence (rate), photosensitizer concentration, and tissue oxygen concentration. Here we determine tissue oxygenation from non-invasive diffuse correlation spectroscopy (DCS) measurement of tumor blood flow using a conversion factor established preclinically. In this study, we have enrolled 24 pleural PDT patients into the study. Of these patients, we are able to obtain data on 20. Explicit dosimetry of light fluence, Photofrin concentration, and tissue oxygenation concentrations were integrated into the ROSED model to calculate [ROS]rx across multiple sites inside the pleural cavity and among different patients. Large inter- and intra-patient heterogeneities in [ROS]rx were observed, despite identical 60 J/cm2 light doses, with mean [ROS]rx,meas of 0.56 ± 0.26 mM for 13 patients with 21 sites, and [ROS]rx,calc1 of 0.48 ± 0.23 mM for 20 patients with 76 sites. This study presented the first comprehensive analysis of clinical ROSED in pleural mesothelioma patients, providing valuable data on future ROSED based pleural PDT that can potentially produce uniform ROS and thus improve the PDT efficacy for Photofrin-mediated pleural PDT.

Curcumin-based residue-free and reusable photodynamic inactivation system for liquid foods and its application in freshly squeezed orange juice

To enhance curcumin's application in photodynamic inactivation (PDI) of liquid foods, a supramolecular complex of biotin-modified β-cyclodextrin and curcumin (Biotin-CD@Cur) was synthesized. This complex significantly improves curcumin's solubility, stability, and PDI efficiency. Following PDI, Biotin-CD@Cur can be magnetically separated from the liquid matrix using streptavidin-coated magnetic beads (SA-MBs). Leveraging the reversible binding between streptavidin and biotin, Biotin-CD@Cur and SA-MBs fully dissociate in ultrapure water at 70 °C, enabling reuse. Antibacterial tests in freshly squeezed orange juice demonstrated that a low dose of 1.5 J/cm2 from a 420 nm LED array and 10 μg/mL of Biotin-CD@Cur achieved log reductions of 3.287 ± 0.015 for Staphylococcus aureus and 2.961 ± 0.011 for Listeria monocytogenes, while preserving the juice's flavor and nutritional contents. The PDI system remained effective for at least four cycles. Ultra-performance liquid chromatography and atomic absorption spectroscopy confirmed no residues of system components in the juice after magnetic separation.

A Highly Charged Positive Cage Causes Simultaneous Enhancement of Type‐II and O2‐Independent‐Type‐I Photodynamic Therapy via One‐/Two‐Photon Stimulation and Tumor Immunotherapy via PANoptosis and Ferroptosis

To solve the oxygen dependence problem of photodynamic therapy (PDT), it is critical to explore photosensitizers that do not rely on O2 molecule to generate reactive oxygen species (ROS). Herein, a stable cationic metal‐organic cage [Pd6(RuLoz3)8](BF4)28 (MOC‐88) that possesses high +28 charges is designed. The cage‐confined positive microenvironment enables efficient generation of hydroxyl radicals and improved yield of the singlet oxygen under one‐/two‐photon excitation, showing excellent performance to concurrently enhance Type‐II and O2‐independent‐Type‐I PDT. Moreover, the effective ROS production and robust lipid peroxidation trigger a series of signaling pathways (inflammasome, cyclic guanosine monophosphate–adenosine monophosphate synthase stimulator of interferon genes, and NF‐κB) to evoke PANoptosis and ferroptosis in tumor cells, enabling MOC‐88 to simultaneously cause the loss of cell membrane integrity, release a series of inflammatory cytokines and damage‐associated molecular patterns, stimulate the maturation and antigen presentation ability of dendritic cells, and ultimately activate T‐cell‐dependent adaptive immunity in vivo to inhibit tumor growth.

Advances and perspectives in use of semisolid formulations for photodynamic methods

Although nearly 30 years have passed since the introduction of the first clinically approved photosensitizer for photodynamic therapy, progress in developing new pharmaceutical formulations remains unsatisfactory. This review highlights that despite years of research, many recurring challenges and issues remain unresolved. The paper includes an analysis of selected essential studies involving aminolevulinic acid and its derivatives, as well as other photosensitizers with potential for development as medical products. Among various possible vehicles, special attention is given to gelatin, alginates, poly(ethylene oxide), polyacrylic acid, and chitosan. The focus is particularly on infectious and cancerous diseases. Key aspects of developing new semi-solid drug forms should prioritize the creation of easily manufacturable and biocompatible preparations for clinical use. At the same time, new formulations should preserve the primary function of photosensitizers, which is the generation of reactive oxygen species capable of destroying pathogenic cells or tumors. Additionally, the use of adjuvant properties of carriers, which can enhance the effectiveness of macrocycles, is emphasized, especially in chitosan-based antibacterial formulations. Current research indicates that many promising dyes and macrocyclic compounds with high potential as photosensitizers in photodynamic therapy remain unexplored in formulation and development work. This review outlines potential new and previously explored pathways for advancing photosensitizers as active pharmaceutical ingredients (APIs).

A comprehensive review of Co3O4 nanostructures in cancer: Synthesis, characterization, reactive oxygen species mechanisms, and therapeutic applications

Nanotechnology involves creating, analyzing, and using tiny materials. Cobalt oxide nanoparticles (Co3O4 NPs) have several medicinal uses due to their unique antifungal, antibacterial, antioxidant, anticancer, larvicidal, anticholinergic, antileishmanial, wound healing, and antidiabetic capabilities. Cobalt oxide nanoparticles (Co3O4 NPs) with attractive magnetic properties have found widespread use in biomedical applications, including magnetic resonance imaging, magnetic hyperthermia, and magnetic targeting. The high surface area of Co3O4 leads to unique electrical, optical, catalytic, and magnetic properties, which make it a promising candidate for biomedical bases. Additionally, cobalt nanoparticles with various oxidation states (i.e., Co2+, Co3+, and Co4+) are beneficial in numerous utilizations. Co3O4 nanoparticles as a catalyzer accelerate the conversion rate of hydrogen peroxide (H2O2) to harmful hydroxyl radicals (•OH), which destroy tumor cells. However, it is also possible to enhance the generation of reactive oxygen species (ROS) and successfully treat cancer by combining these nanoparticles with drugs or other nanoparticles. This review summarizes the past concepts and discusses the present state and development of using Co3O4 NPs in cancer treatments by ROS generation. This review emphasizes the advances and current patterns in ROS generation, remediation, and some different cancer treatments using Co3O4 nanoparticles in the human body. It also discusses synthesis techniques, structure, morphological, optical, and magnetic properties of Co3O4 NPs.

Unveiling the potential of photodynamic therapy with nanocarriers as a compelling therapeutic approach for skin cancer treatment: current explorations and insights

Skin carcinoma is one of the most prevalent types of carcinomas. Due to high incidence of side effects in conventional therapies (radiotherapy and chemotherapy), photodynamic therapy (PDT) has gained huge attention as an alternate treatment strategy. PDT involves the administration of photosensitizers (PS) to carcinoma cells which produce reactive oxygen species (ROS) on irradiation by specific wavelengths of light that result in cancer cells' death via apoptosis, autophagy, or necrosis. Topical delivery of PS to the skin cancer cells at the required concentration is a challenge due to the compounds' innate physicochemical characteristics. Nanocarriers have been observed to improve skin permeability and enhance the therapeutic efficiency of PDT. Polymeric nanoparticles (NPs), metallic NPs, and lipid nanocarriers have been reported to carry PS successfully with minimal side effects and high effectiveness in both melanoma and non-melanoma skin cancers. Advanced carriers such as quantum dots, microneedles, and cubosomes have also been addressed with reported studies to show their scope of use in PDT-assisted skin cancer treatment. In this review, nanocarrier-aided PDT in skin cancer therapies has been discussed with clinical trials and patents. Additionally, novel nanocarriers that are being investigated in PDT are also covered with their future prospects in skin carcinoma treatment.

Isolation, Identification, and Biological Activities of a New Chlorin e6 Derivative

Chlorin e6 is a well-known photosensitizer used in photodynamic diagnosis and therapy. A method for identifying and purifying a novel process-related impurity during the synthesis of chlorin e6 has been developed. Its structure was elucidated using NMR and HRMS. This new impurity is formed from chlorophyll b rather than chlorophyll a, which is the source of chlorin e6. The intermediates formed during chlorin e6 synthesis were monitored using HPLC-mass spectrometry. This new impurity was identified as rhodin g7 71-ethyl ester, the structure of which remains unknown to date. The cytotoxic effects of this novel compound in both dark and light conditions were studied against five cancer cell lines (HT29, MIA-PaCa-2, PANC-1, AsPC-1, and B16F10) and a normal cell line (RAW264.7) and compared to those of chlorin e6. Upon irradiation using a laser at 0.5 J/cm2, rhodin g7 71-ethyl ester demonstrated higher cytotoxicity (2-fold) compared to chlorin e6 in the majority of the cancer cell lines. Furthermore, this new compound exhibited higher dark cytotoxicity compared to chlorin e6. Studies on singlet oxygen generation, the accumulation in highly vascular liver tissue, and the production of reactive oxygen species in MIA-PaCa-2 cancer cells via rhodin g7 71-ethyl ester correspond to its higher cytotoxicity as a newly developed photosensitizer. Therefore, rhodin g7 71-ethyl ester could be employed as an alternative or complementary agent to chlorin e6 in the photodynamic therapy for treating cancer cells.

Fly into the light: eliminating Drosophila melanogaster with chlorophyllin-based Photodynamic Inactivation

Fruit flies spoil crops in agricultural settings. As conventional pesticides may generate negative off-target effects on humans or the environment, existing treatment methods need eco-friendly and safe alternatives. Photodynamic Inactivation (PDI) is based on the photosensitizer-mediated and light-induced overproduction of reactive oxygen species in targets. We here explore the potential of PDI for the control of fruit fly pests. Drosophila melanogaster serves as well-established model organism in this study. Two distinct experimental approaches are presented: the feed assay, in which fruit flies are provided with sodium magnesium chlorophyllin (Chl, approved as food additive E140) along with sucrose (3%) as their food, and the spray assay, where the photosensitizer is sprayed onto the insects. We show that PDI based on Chl can induce moribundity rates of Drosophila melanogaster of more than 99% with 5 mM Chl and LED illumination (395 nm, 8 h incubation in the dark, radiant exposure 78.9 J/cm2) with the feed assay. If the radiant exposure is doubled to 157.8 J/cm2, 88% of insects are killed by PDI based on 1 mM Chl. The photoactive compound is also effective if presented on strawberries without addition of sucrose with somewhat lower moribundity (71% at 5 mM Chl). Spraying Chl onto insects is less effective than feeding the photosensitizer: 5 mM Chl resulted in 79.5% moribundity (drug to light interval 8 h, radiant exposure 78.9 J/cm2), but if 5 h of sun light (532 J/cm2) and overnight (14 h) dark incubation is used for activation of Chl, more than 95% of insects are killed. As conclusion, Chl serves as effective photoinsecticide against Drosophila melanogaster if a drug to light interval of 8 h is maintained. Feeding the photoactive compound together with sucrose is more effective than spraying it onto insects and increasing the radiant exposure allows for lowering the photosensitizer concentration. Photodynamic Inactivation might therefore represent an eco-friendly addition to the farmers armamentarium against (semi-transparent) insects.

In vitro modeling of recurrent Dermatofibrosarcoma Protuberans: Assessment of 5-aminolevulinic acid photodynamic therapy efficacy

BACKGROUND

Dermatofibrosarcoma Protuberans (DFSP) is a rare, low-grade malignant tumor of the dermis with a high recurrence rate post-surgery. Current treatments, including surgery, radiotherapy, and targeted therapy, have limitations. Photodynamic therapy (PDT) with 5-aminolevulinic acid (5-ALA) is a promising non-invasive approach, but its efficacy in DFSP treatment remains underexplored.

METHODS

This study aimed to evaluate the anti-tumor efficacy of 5-ALA PDT using an in vitro model derived from a recurrent DFSP patient. The cells were treated with varying concentrations of 5-ALA and exposed to red light, followed by assessments of cell viability, proliferation, apoptosis, migration, invasion, angiogenesis, and expression of DFSP-related genes and proteins.

RESULTS

5-ALA PDT significantly reduced DFSP cell viability in a dose-dependent manner and induced apoptosis. It also effectively inhibited cell proliferation, migration, and invasion, as well as suppressed angiogenic activity in conditioned media. Furthermore, 5-ALA PDT downregulated the expression of COL1A1 and PDGFRB, key genes in DFSP pathogenesis.

CONCLUSIONS

The findings provide the first evidence of 5-ALA PDT's in vitro anti-tumor efficacy against DFSP, suggesting its potential as a novel therapeutic approach for DFSP. Further studies are warranted to explore the clinical utility of 5-ALA PDT in preventing DFSP recurrence.

Cytotoxic and Immunomodulatory Effects of Hypericin as a Photosensitizer in Photodynamic Therapy Used on Skin Cell Cultures

Determination of the hypericin-photodynamic (HY-PDT) effect on the secretion of cytokines secreted by the skin cells, may be the basis for using the immunomodulatory effect of photodynamic action in the treatment of inflammatory skin diseases. The study aimed to evaluate the cytotoxic and immunomodulatory effects of hypericin (HY) in photodynamic therapy (PDT) performed in vitro on cultures of selected skin cell lines. The study used two human cell lines, primary dermal fibroblast (HDFa) and primary epidermal keratinocytes (HEKa). The MTT test was used to define the metabolic activity of treated cells. Cell supernatants subjected to sublethal PDT were assessed to determine the interleukins: IL-2, IL-8, IL-10, IL-11, IL-19, IL-22, and metalloproteinase 1 (MMP-1). The results confirm the destructive effect of HY-PDT and the immunomodulatory effects of sublethal doses on the selected skin cells, depending on the concentration of HY and the light doses. No statistically significant differences were noted in IL-2 and IL-10 concentration after HY-PDT for HEKa and HDFa lines. After using HY-PDT, the concentration of IL-8, MMP-1, IL-22, and IL-11 significantly decreased in the HEKa line. Moreover, the concentration of IL-19 and MMP-1 significantly decreased in the HDFa line. The concentration of IL-11 in the HDFa line after using only the HY, without the light, increased but decreased after HY-PDT. Our experiment confirmed that HY-PDT has not only a cytotoxic effect but, used in sublethal doses, also presents immunomodulatory properties. These may be an advantage of HY-PDT when used in the treatment of persistent skin inflammation, connected with the release of pro-inflammatory cytokines resistant to conventional treatment methods.

Nanobody-mediated targeting of zinc phthalocyanine with polymer micelles as nanocarriers

Photodynamic therapy (PDT) is a suitable alternative to currently employed cancer treatments. However, the hydrophobicity of most photosensitizers (e.g., zinc phthalocyanine (ZnPC)) leads to their aggregation in blood. Moreover, non-specific accumulation in skin and low clearance rate of ZnPC leads to long-lasting skin photosensitization, forcing patients with a short life expectancy to remain indoors. Consequently, the clinical implementation of these photosensitizers is limited. Here, benzyl-poly(ε-caprolactone)-b-poly(ethylene glycol) micelles encapsulating ZnPC (ZnPC-M) were investigated to increase the solubility of ZnPC and its specificity towards cancers cells. Asymmetric flow field-flow fractionation was used to characterize micelles with different ZnPC-to-polymer ratios and their stability in human plasma. The ZnPC-M with the lowest payload (0.2 and 0.4% ZnPC w/w) were the most stable in plasma, exhibiting minimal ZnPC transfer to lipoproteins, and induced the highest phototoxicity in three cancer cell lines. Nanobodies (Nbs) with binding specificity towards hepatocyte growth factor receptor (MET) or epidermal growth factor receptor (EGFR) were conjugated to ZnPC-M to facilitate cell targeting and internalization. MET- and EGFR-targeting micelles enhanced the association and the phototoxicity in cells expressing the target receptor. Altogether, these results indicate that ZnPC-M decorated with Nbs targeting overexpressed proteins on cancer cells may provide a better alternative to currently approved formulations.

Effects of Nanobubbles on Photochemical Processes of Levofloxacin Photosensitizer

Photodynamic therapy (PDT) stands as an efficacious modality for the treatment of cancer and various diseases, in which optimization of the electron transfer and augmentation of the production of lethal reactive oxygen species (ROS) represent pivotal challenges to enhance its therapeutic efficacy. Empirical investigations have established that the spontaneous initiation of redox reactions associated with electron transfer is feasible and is located in the gas-liquid interfaces. Meanwhile, nanobubbles (NBs) are emerging as entities capable of furnishing a plethora of such interfaces, attributed to their stability and large surface/volume ratio in bulk water. Thus, NBs provide a chance to expedite the electron-transfer kinetics within the context of PDT in an ambient environment. In this paper, we present a pioneering exploration into the impact of nitrogen nanobubbles (N2-NBs) on the electron transfer of the photosensitizer levofloxacin (LEV). Transient absorption spectra and time-resolved decay spectra, as determined through laser flash photolysis, unequivocally reveal that N2-NBs exhibit a mitigating effect on the decay of the LEV excitation triplet state, thereby facilitating subsequent processes. Of paramount significance is the observation that the presence of N2-NBs markedly accelerates the electron transfer of LEV, albeit with a marginal inhibitory influence on its energy-transfer reaction. This observation is corroborated through absorbance measurements and offers compelling evidence substantiating the role of NBs in expediting electron transfer within the ambit of PDT. The mechanism elucidated herein sheds light on how N2-NBs intricately influence both electron-transfer and energy-transfer reactions in the photosensitizer LEV. These findings not only contribute to a nuanced understanding of the underlying processes but also furnish novel insights that may inform the application of NBs in the realm of photodynamic therapy.

Application of photosensitive dental materials as a novel antimicrobial option in dentistry: A literature review

The formation of dental plaque is well-known for its role in causing various oral infections, such as tooth decay, inflammation of the dental pulp, gum disease, and infections of the oral mucosa like peri-implantitis and denture stomatitis. These infections primarily affect the local area of the mouth, but if not treated, they can potentially lead to life-threatening conditions. Traditional methods of mechanical and chemical antimicrobial treatment have limitations in fully eliminating microorganisms and preventing the formation of biofilms. Additionally, these methods can contribute to the development of drug-resistant microorganisms and disrupt the natural balance of oral bacteria. Antimicrobial photodynamic therapy (aPDT) is a technique that utilizes low-power lasers with specific wavelengths in combination with a photosensitizing agent called photosensitizer to kill microorganisms. By inducing damage through reactive oxygen species (ROS), aPDT offers a new approach to addressing dental plaque and associated microbial biofilms, aiming to improve oral health outcomes. Recently, photosensitizers have been incorporated into dental materials to create photosensitive dental materials. This article aimed to review the use of photosensitive dental materials for aPDT as an innovative antimicrobial option in dentistry, with the goal of enhancing oral health.

Photodynamic therapy successfully treats refractory onychomycosis caused by Trichosporon asahii: a case report

Onychomycosis, a fungal infection affecting the nail, is characterized by discoloration and thickening of the nail plate and is the most prevalent nail infection globally. We present a case of onychomycosis caused by Trichosporon asahii, a less common etiology. Notably, the patient was successfully treated with a non-traditional antibacterial approach, photodynamic therapy, which has been infrequently documented in the literature for such infections.

A novel investigational preclinical model to assess fluence rate for dental oral craniofacial tissues

OBJECTIVE

Photodynamic Therapy (PDT) and Photobiomodulation (PBM) are recognized for their potential in treating head and neck conditions. The heterogeneity of human tissue optical properties presents a challenge for effective dosimetry. The porcine mandible cadaver serves as an excellent model and has several similarities to human tissues of the dental oral craniofacial complex. This study aims to validate a novel modeling system that will help refine PDT and PBM dosimetry for the head and neck region.

METHODS AND MATERIALS

Light transmission was analyzed through several tissue combinations at distances of 2 mm to 10 mm. Maximum light fluence rates (mW/cm2) were compared across tissue types to reveal the effects of tissue heterogeneity.

RESULTS

The study revealed that light fluence is affected by tissue composition, with dentin/enamel showing reduced transmission and soft tissue regions exhibiting elevated values. The porcine model has proven to be efficient in mimicking human tissue responses to light, enabling the potential to optimize future protocols.

CONCLUSION

The porcine mandible cadaver is a novel model to understand the complex interactions between light and tissue. This study provides a foundation for future investigations into dosimetry optimization for PDT and PBM.

Perspectives in the treatment of antibiotic-resistant bacterial infections with active photodynamic partners within the framework of the EURESTOP COST Action (CA21145)

The European Network for diagnosis and treatment of antibiotic-resistant bacterial infections-EURESTOP COST Action CA21145 focuses on tackling the burden of antimicrobial resistance (AMR) and has gathered many members working on photodynamic approaches. This European consortium is presented here in the One Health context, to highlight the potential of antimicrobial photodynamic therapy (aPDT) in the fight against AMR.

Three-dimensional printing of the human lung pleural cavity model for PDT malignant mesothelioma

OBJECTIVE

The primary aim was to investigate emerging 3D printing and optical acquisition technologies to refine and enhance photodynamic therapy (PDT) dosimetry in the management of malignant pleural mesothelioma (MPM).

MATERIALS AND METHODS

A rigorous digital reconstruction of the pleural lung cavity was conducted utilizing 3D printing and optical scanning methodologies. These reconstructions were systematically assessed against CT-derived data to ascertain their accuracy in representing critical anatomic features and post-resection topographical variations.

RESULTS

The resulting reconstructions excelled in their anatomical precision, proving instrumental translation for precise dosimetry calculations for PDT. Validation against CT data confirmed the utility of these models not only for enhancing therapeutic planning but also as critical tools for educational and calibration purposes.

CONCLUSION

The research outlined a successful protocol for the precise calculation of light distribution within the complex environment of the pleural cavity, marking a substantive advance in the application of PDT for MPM. This work holds significant promise for individualizing patient care, minimizing collateral radiation exposure, and improving the overall efficiency of MPM treatments.

Photodynamic antibacterial activity of oxidase-like nanozyme based on long-lived room-temperature phosphorescent carbon dots

In this study, a novel long-lived room-temperature phosphorescent (RTP) carbon dots (P-CDs) with the properties of ultraviolet/visible (UV/Vis) light photoresponsive oxidase-like nanozyme were synthesized from diethylenetriaminepentaacetic acid and through a one-step hydrothermal method. P-CDs were used as a light-driven oxidative-like enzyme for antimicrobial studies. The results showed that under UV/Vis light irradiation, P-CDs could efficiently convert O2 into 1O2, and the strong oxidizing property of 1O2 greatly enhanced the growth inhibition of P-CDs on Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). Meanwhile, P-CDs exhibited good photodynamic antifungal properties against Botrytis cinerea (B. cinerea). Then the P-CDs were made into P-CDs/PVA films, which effectively prolonged the preservation period of fruits under photodynamic antibacterial action. The good biocompatibility and efficient photosensitive oxygen activation can make P-CDs a more practically useful oxidase-like nanozyme.

Ir(III) Half-Sandwich Photosensitizers with a π-Expansive Ligand for Efficient Anticancer Photodynamic Therapy

One approach to reduce the side effects of chemotherapy in cancer treatment is photodynamic therapy (PDT), which allows spatiotemporal control of the cytotoxicity. We have used the strategy of coordinating π-expansive ligands to increase the excited state lifetimes of Ir(III) half-sandwich complexes in order to facilitate the generation of 1O2. We have obtained derivatives of formulas [Cp*Ir(C∧N)Cl] and [Cp*Ir(C∧N)L]BF4 with different degrees of π-expansion in the C∧N ligands. Complexes with the more π-expansive ligand are very effective photosensitizers with phototoxic indexes PI > 2000. Furthermore, PI values of 63 were achieved with red light. Time-dependent density functional theory (TD-DFT) calculations nicely explain the effect of the π-expansion. The complexes produce reactive oxygen species (ROS) at the cellular level, causing mitochondrial membrane depolarization, cleavage of DNA, nicotinamide adenine dinucleotide (NADH) oxidation, as well as lysosomal damage. Consequently, cell death by apoptosis and secondary necrosis is activated. Thus, we describe the first class of half-sandwich iridium cyclometalated complexes active in PDT.

Review of three-dimensional spheroid culture models of gynecological cancers for photodynamic therapy research

Photodynamic therapy (PDT) is a specific cancer treatment with minimal side effects. However, it remains challenging to apply PDT clinically, partially due to the difficulty of translating research findings to clinical settings as the conventional 2D cell models used for in vitro research are accepted as less physiologically relevant to a solid tumour. 3D spheroids offer a better model for testing PDT mechanisms and efficacy, particularly on photosensitizer uptake, cellular and subcellular distribution and interaction with cellular oxygen consumption. 3D spheroids are usually generated by scaffold-free and scaffold-based methods and are accepted as physiologically relevant models for PDT anticancer research. Scaffold-free methods offer researchers advantages including high efficiency, reproducible, and controlled microenvironment. While the scaffold-based methods offer an extracellular matrix-like 3D scaffold with the necessary architecture and chemical mediators to support the spheroid formation, the natural scaffold used may limit its usage because of low reproducibility due to patch-to-patch variation. Many studies show that the 3D spheroids do offer advantages to gynceologcial cancer PDT investigation. This article will provide a review of the applications of 3D spheroid culture models for the PDT research of gynaecological cancers.

Light-Responsive and Dual-Targeting Liposomes: From Mechanisms to Targeting Strategies

In recent years, nanocarriers have played an ever-increasing role in clinical and biomedical applications owing to their unique physicochemical properties and surface functionalities. Lately, much effort has been directed towards the development of smart, stimuli-responsive nanocarriers that are capable of releasing their cargos in response to specific stimuli. These intelligent-responsive nanocarriers can be further surface-functionalized so as to achieve active tumor targeting in a sequential manner, which can be simply modulated by the stimuli. By applying this methodological approach, these intelligent-responsive nanocarriers can be directed to different target-specific organs, tissues, or cells and exhibit on-demand controlled drug release that may enhance therapeutic effectiveness and reduce systemic toxicity. Light, an external stimulus, is one of the most promising triggers for use in nanomedicine to stimulate on-demand drug release from nanocarriers. Light-triggered drug release can be achieved through light irradiation at different wavelengths, either in the UV, visible, or even NIR region, depending on the photophysical properties of the photo-responsive molecule embedded in the nanocarrier system, the structural characteristics, and the material composition of the nanocarrier system. In this review, we highlighted the emerging functional role of light in nanocarriers, with an emphasis on light-responsive liposomes and dual-targeted stimuli-responsive liposomes. Moreover, we provided the most up-to-date photo-triggered targeting strategies and mechanisms of light-triggered drug release from liposomes and NIR-responsive nanocarriers. Lastly, we addressed the current challenges, advances, and future perspectives for the deployment of light-responsive liposomes in targeted drug delivery and therapy.

Nano-phototherapy: Favorable prospects for cancer treatment

Nanotechnology-based phototherapies have drawn interest in the fight against cancer because of its noninvasiveness, high flexibility, and precision in terms of cancer targeting and drug delivery based on its surface properties and size. Phototherapy has made remarkable development in recent decades. Approaches to phototherapy, which utilize nanomaterials or nanotechnology have emerged to contribute to advances around nanotechnologies in medicine, particularly for cancers. A brief overviews of the development of photodynamic therapy as well as its mechanism in cancer treatment is provided. We emphasize the design of novel nanoparticles utilized in photodynamic therapy while summarizing the representative progress during the recent years. Finally, to forecast important future research in this area, we examine the viability and promise of photodynamic therapy systems based on nanoparticles in clinical anticancer treatment applications and briefly make mention of the elimination of all reactive metabolites pertaining to nano formulations inside living organisms providing insight into clinical mechanistic processes. Future developments and therapeutic prospects for photodynamic treatments are anticipated. Our viewpoints might encourage scientists to create more potent phototherapy-based cancer therapeutic modalities. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Ruthenium(II) polypyridyl complexes as emerging photosensitisers for antibacterial photodynamic therapy

Photodynamic therapy (PDT) has recently emerged as a potential valuable alternative to treat microbial infections. In PDT, singlet oxygen is generated in the presence of photosensitisers and oxygen under light irradiation of a specific wavelength, causing cytotoxic damage to bacteria. This review highlights different generations of photosensitisers and the common characteristics of ideal photosensitisers. It also focuses on the emergence of ruthenium and more specifically on Ru(II) polypyridyl complexes as metal-based photosensitisers used in antimicrobial photodynamic therapy (aPDT). Their photochemical and photophysical properties as well as structures are discussed while relating them to their phototoxicity. The use of Ru(II) complexes with recent advancements such as nanoformulations, combinatory therapy and photothermal therapy to improve on previous shortcomings of the complexes are outlined. Future perspectives of these complexes used in two-photon PDT, photoacoustic imaging and sonotherapy are also discussed. This review covers the literature published from 2017 to 2023.

A telluroviologen-anchored tetraphenylporphyrin as sonosensitizer for periodontitis sonodynamic therapy

Periodontitis is a chronic disease caused by bacteria (e.g. Porphyromonas gingivalis, P.gingivalis) that currently lacks effective non-invasive treatment options. Sonodynamic therapy (SDT) is an emerging non-invasive antimicrobial therapeutic strategy. Since ultrasonic tooth cleaning is widely used in dental treatments, SDT has significant potential for the facile implementation of treat periodontitis. However, hypoxia in periodontitis severely limits the effectiveness of traditional sonosensitizers. To address this issue, we have developed a new sonosensitizer termed as TPP-TeV, which combines the traditional sonosensitizer tetraphenylporphyrin (TPP) with a new photosensitizer telluroviologen (TeV). Under ultrasound radiation, TPP-TeV can produce numerous cationic free radicals (TPP-TeV•), which subsequently generate ROS free radicals (O2•-, •OH) efficiently via electron transfer mechanism, resulting in the effective killing of anaerobic P.gingivalis both in vivo and in vitro. As a result, the dental environment is improved, and the inhibition rate of alveolar bone loss reaches 80 %. The introduction of tellurium into the viologen molecule induces changes in its reduction potential, resulting in increased rigidity of the molecule. This modification systematically reduces the biotoxicity of our novel sonosensitizer by 75 % at 50 μM based on bacterial experiments. These promising findings could potentially establish new options for sonodynamic therapy (SDT) in periodontitis clinical treatments.

Immunomodulatory Effect of Hypericin-Mediated Photodynamic Therapy on Oral Cancer Cells

In 2020, there were 377,713 new oral and lip cancer diagnoses and 177,757 deaths. Oral cancer is a malignancy of the head and neck region, and 90% of cases are squamous cell carcinomas (OSCCs). One of the alternative methods of treating pre-cancerous lesions and oral cancer is photodynamic therapy (PDT). In addition to the cytotoxic effect, an important mechanism of PDT action is the immunomodulatory effect. This study used the OSCC (SCC-25) cell line and the healthy gingival fibroblast (HGF-1) line. A compound of natural origin-hypericin (HY)-was used as the photosensitizer (PS). The HY concentrations of 0-1 µM were used. After two hours of incubation with PS, the cells were irradiated with light doses of 0-20 J/cm2. The MTT test determined sublethal doses of PDT. Cell supernatants subjected to sublethal PDT were assessed for interleukin 6 (IL-6), soluble IL-6 receptor alpha (sIL-6Ralfa), sIL-6Rbeta, IL-8, IL-10, IL-11 IL-20, IL-32, and Pentraxin-3 using the Bio-Plex ProTM Assay. The phototoxic effect was observed starting with a light dose of 5 J/cm2 and amplified with increasing HY concentration and a light dose. HY-PDT affected the SCC-25 cell secretion of sIL-6Rbeta, IL-20, and Pentraxin-3. HY alone increased IL-8 secretion. In the case of HGF-1, the effect of HY-PDT on the secretion of IL-8 and IL-32 was found.

Density Functional Theory-Guided Photo-Triggered Anticancer Activity of Curcumin-Based Zinc(II) Complexes

Photodynamic therapy (PDT) has evolved as a new therapeutic modality for cancer treatment with fewer side effects and drug resistance. Curcumin exhibits PDT activity, but its low bioavailability restricts its clinical application. Here, the bioavailability of curcumin was increased by its complex formation with the Zn(II) center. For a structure-activity relationship study, Zn(II)-based complexes (1-3) comprising N^N-based ligands (2,2'-bipyridine in 1 and 2 or 1,10-phenanthroline in 3) and O^O-based ligands (acetylacetone in 1, monoanionic curcumin in 2 and 3) were synthesized and thoroughly characterized. The X-ray structure of the control complex, 1, indicated a square pyramidal shape of the molecules. Photophysical and TD-DFT studies indicated the potential of 2 and 3 as good visible light type-II photosensitizers for PDT. Guided by the TD-DFT studies, the low-energy visible light-triggered singlet oxygen (1O2) generation efficacy of 2 and 3 was explored in solution and in cancer cells. As predicted by the TD-DFT calculations, these complexes produced 1O2 efficiently in the cytosol of MCF-7 cancer cells and ultimately displayed excellent apoptotic anticancer activity in the presence of light. Moreover, the molecular docking investigation showed that complexes 2 and 3 have very good binding affinities with caspase-9 and p-53 proteins and could activate them for cellular apoptosis. Further molecular dynamics simulations confirmed the stability of 3 in the caspase-9 protein binding site.

Photobiomodulation effect of infra-red laser on the level of gonad maturity in the Simese Catfish (Pangasianodon hypophthalmus)

The purpose of this study is to determine how photo biomodulation therapy utilizing infrared diode laser irradiation (975.2 nm) affects the gonadal maturity level (GML) of male Siamese catfish (Pan-gasianodon hypothalamus). The interest in applying laser therapy in medicine and dentistry has remarkably increased in the last decade. Different types of lasers are available, and their usage is well-defined by different parameters, such as wavelength, energy density, power output, duration of radiation, power density and radiation mode. Infrared diode laser irradiation is used at the reproductive point (governor's vessel), situated 2/3 of the way between the anus and the pectoral fin. This study examined the metrics GML, gonads somatic index, and hepatosomatic index. The treatments were Control+ (ovaprim), Control- (without the treatment), P1 (0.2 J/cm2), P2 (0.4 J/cm2), P3 (0.6 J/cm2), and P4 (0.8 J/cm2). Therapy with infrared diode laser irradiation can modify gonad maturity (GML), gonadosomal index, and hepatosomatic index in male Siamese catfish. The photobiomodulation effect of an infrared laser stimulated the gonadal maturation of Siamese catfish. This is based on the values of wavelength (nm), power (mW), beam area (cm2), time (s), radiation mode (rad) and energy dose (J/cm2) in Control- (no treatment), control+ (ovaprim), P1, P2, P3, and P4. The increase in the observed parameter values is due to the vitellogenesis process. The fish gonads at the GML IV had the highest GML at P2 (dose 0.4 J/cm2), with a GSI value of 1.02% and an HSI value of 1.46%. According to the study's findings, photo biomodulation therapy with infrared diode laser exposure at a dose of 0.4 J/cm2 is the best way to increase the gonad maturity of male Siamese catfish.

Cellular Mechanisms of Singlet Oxygen in Photodynamic Therapy

In this review, we delve into the realm of photodynamic therapy (PDT), an established method for combating cancer. The foundation of PDT lies in the activation of a photosensitizing agent using specific wavelengths of light, resulting in the generation of reactive oxygen species (ROS), notably singlet oxygen (1O2). We explore PDT's intricacies, emphasizing its precise targeting of cancer cells while sparing healthy tissue. We examine the pivotal role of singlet oxygen in initiating apoptosis and other cell death pathways, highlighting its potential for minimally invasive cancer treatment. Additionally, we delve into the complex interplay of cellular components, including catalase and NOX1, in defending cancer cells against PDT-induced oxidative and nitrative stress. We unveil an intriguing auto-amplifying mechanism involving secondary singlet oxygen production and catalase inactivation, offering promising avenues for enhancing PDT's effectiveness. In conclusion, our review unravels PDT's inner workings and underscores the importance of selective illumination and photosensitizer properties for achieving precision in cancer therapy. The exploration of cellular responses and interactions reveals opportunities for refining and optimizing PDT, which holds significant potential in the ongoing fight against cancer.

Riboflavin-Vancomycin Conjugate Enables Simultaneous Antibiotic Photo-Release and Photodynamic Killing against Resistant Gram-Positive Pathogens

Decades of antibiotic misuse have led to alarming levels of antimicrobial resistance, and the development of alternative diagnostic and therapeutic strategies to delineate and treat infections is a global priority. In particular, the nosocomial, multidrug-resistant "ESKAPE" pathogens such as Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus spp (VRE) urgently require alternative treatments. Here, we developed light-activated molecules based on the conjugation of the FDA-approved photosensitizer riboflavin to the Gram-positive specific ligand vancomycin to enable targeted antimicrobial photodynamic therapy. The riboflavin-vancomycin conjugate proved to be a potent and versatile antibacterial agent, enabling the rapid, light-mediated, killing of MRSA and VRE with no significant off-target effects. The attachment of riboflavin on vancomycin also led to an increase in antibiotic activity against S. aureus and VRE. Simultaneously, we evidenced for the first time that the flavin subunit undergoes an efficient photoinduced bond cleavage reaction to release vancomycin, thereby acting as a photoremovable protecting group with potential applications in drug delivery.

Virtual screening of pyrazole derivatives of usnic acid as new class of anti-hyperglycemic agents against PPARγ agonists

The finest sources of therapeutic agents are natural products, and usnic acid is a secondary metabolite derived from lichen that has a wide range of biological actions, including anti-viral, anti-cancer, anti-bacterial, and anti-diabetic (hyperglycemia). Based on the hyperglycemia activity of UA, this work seeks to identify new anti-hyperglycemia medicines by virtual screening of pyrazole derivatives of UA. Seven hit compounds (Compounds 1, 5, 6, 7, 17, 18 and 33), which finally go through docking-based screening to produce the lead molecule, were identified by the physicochemical attributes, drug-likeliness, and ADMET prediction. The docking score for the chosen compounds containing PPARγ agonists ranged from -7.6 to -9.2 kcal/mol, whereas the docking goal for compounds 5, 6, and 7 was -9.2 kcal/mol. Based on the binding energy and bound amino acid residues as well as compared to the reference compound, compound-6 considered as lead compound. Furthermore, the MD simulation of 3CS8-Compound-6 and 3CS8-Rosiglitazone complexes were performed to verify the stability of these complexes and the binding posture acquired in docking experiments. The compound-6 had strong pharmacological characteristics, bound to the PPARγ agonist active site, and was expected to reduce the activity of the receptor, according to the virtual screening results. It must be justified to conduct both in-vitro and in-vivo experiments to examine the efficacy of this compound.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-023-00176-y.

Type-I Photosensitizer-Triggered Controllable Carbon Monoxide Release for Effective Treatment of Staph Skin Infection

Staphylococcus aureus (S. aureus) infection is a major infectious skin disease that is highly resistant to conventional antibiotic treatment and host immune defense, leading to recurrence and exacerbation of bacterial infection. Herein, we developed a photoresponsive carbon monoxide (CO)-releasing nanocomposite by integrating anion-π+ type-I photosensitizer (OMeTBP) and organometallic complex (FeCO) for the treatment of planktonic S. aureus and biofilm-associated infections. After optimizing the molar ratio of FeCO and OMeTBP, the prepared nanoparticles, OMeTBP@FeCONPs, not only ensured sufficient loading of CO donors and efficient CO generation but also showed negligible free ROS leakage under light irradiation, which helped to avoid tissue damage caused by excessive ROS. Both in vitro and in vivo results demonstrated that OMeTBP@FeCONPs could effectively inhibit S. aureus methicillin-resistant S. aureus (MRSA), and bacterial biofilm. Our design has the potential to overcome the resistance of conventional antibiotic treatment and provide a more effective option for bacterial infections.

New Hybrid Compound Candidate as Photothermal Agent Based on DPP Derivatives and Toluidine Blue: A Theoretical Perspective

In this article, the synthesis of a new hybrid compound, candidate as photothermal agent, is proposed, based on TDPP (3,6-di(thiophene-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione) and toluidine blue. Electronic structure calculations at the DFT, TD-DFT and CCSD level of theories were performed to obtain ground and excited states molecular structures, photophysical properties and absorption spectrum of the hybrid and the starting compounds. Additionally, ADMET calculations were performed to predict the pharmacokinetic, metabolic and toxicity properties of the proposed compound. The results showed that the proposed compound is a strong candidate for photothermal agent since (1) it absorbs close to the near-infrared region, (2) it has low fluorescence and intersystem crossing rate constants, (3) it has accessible conical intersection with low energy barrier, (4) the compound shows lower toxicity than the well know compound toluidine blue, which is used in photodynamic therapy, (5) the compound does not show carcinogenic potential, and (6) it obeys the Lipinski's rule of five, used as a reference for the design of new pharmaceuticals.

In Situ Bioconjugation of a Maleimide-Functionalized Ruthenium-Based Photosensitizer to Albumin for Photodynamic Therapy

Maleimide-containing prodrugs can quickly and selectively react with circulating serum albumin following their injection in the bloodstream. The drug-albumin complex then benefits from longer blood circulation times and better tumor accumulation. Herein, we have applied this strategy to a previously reported highly phototoxic Ru polypyridyl complex-based photosensitizer to increase its accumulation at the tumor, reduce off-target cytotoxicity, and therefore improve its pharmacological profile. Specifically, two complexes were synthesized bearing a maleimide group: one complex with the maleimide directly incorporated into the bipyridyl ligand, and the other has a hydrophilic linker between the ligand and the maleimide group. Their interaction with albumin was studied in-depth, revealing their ability to efficiently bind both covalently and noncovalently to the plasma protein. A crucial finding is that the maleimide-functionalized complexes exhibited significantly lower cytotoxicity in noncancerous cells under dark conditions compared to the nonfunctionalized complex, which is a highly desirable property for a photosensitizer. The binding to albumin also led to a decrease in the phototoxicity of the Ru bioconjugates in comparison to the nonfunctionalized complex, probably due to a decreased cellular uptake. Unfortunately, this decrease in phototoxicity was not compensated by a dramatic increase in tumor accumulation, as was demonstrated in a tumor-bearing mouse model using inductively coupled plasma mass spectrometry (ICP-MS) studies. Consequently, this study provides valuable insight into the future design of in situ albumin-binding complexes for photodynamic therapy in order to maximize their effectiveness and realize their full potential.

Recent advances in bacterial cellulose-based antibacterial composites for infected wound therapy

Wound infection arising from pathogenic bacteria brought serious trouble to the patient and medical system. Among various wound dressings that are effective in killing pathogenic bacteria, antimicrobial composites based on bacterial cellulose (BC) are becoming the most popular materials due to their success in eliminating pathogenic bacteria, preventing wound infection, and promoting wound healing. However, as an extracellular natural polymer, BC is not inherently antimicrobial, which means that it must be combined with other antimicrobials to be effective against pathogens. BC has many advantages over other polymers, including nano-structure, significant moisture retention, non-adhesion to the wound surface, which has made it superior to other biopolymers. This review introduces the recent advances in BC-based composites for the treatment of wound infection, including the classification and preparation methods of composites, the mechanism of wound treatment, and commercial application. Moreover, their wound therapy applications include hydrogel dressing, surgical sutures, wound healing bandages, and patches are summarized in detail. Finally, the challenges and future prospects of BC-based antibacterial composites for the treatment of infected wounds are discussed.

Photobleaching Kinetics and Effect of Solvent in the Photophysical Properties of Indocyanine Green for Photodynamic Therapy

Indocyanine green is an attractive molecule for photodynamic therapy due to its near infrared absorption, resulting in a higher tissue penetration. However, its quantum yields of the triplet and singlet state have been reported to be low and then, reactive oxygen species are unlikely to be formed. Aiming to understand the ICG role in photodynamic response, its photobleaching behavior in solution has been studied under distinct conditions of CW laser irradiation at 780 and 808 nm, oxygen saturations and solvents. Sensitizer bleaching and photoproduct formation were measured by absorption spectroscopy and analyzed using the PDT bleaching macroscopic model to extract physical parameters. ICG photobleaching occurs even at lower oxygen concentrations, indicating that the molecule presents more than one way of degradation. Photoproducts were produced even in solution of less than 4 % oxygen saturation for both solvents and excitation wavelengths. Also, the amplitude of absorption related to J-dimers was increased during irradiation, but only in 50 % PBS solution. The formation of photoproducts was enhanced in the presence of J-type dimers under low oxygen concentration, and the quantum yields of triplet and singlet states were one order of magnitude and two times higher, respectively, when compared to ICG in distilled H2 O.

Theranostic imaging and multimodal photodynamic therapy and immunotherapy using the mTOR signaling pathway

Tumor metastases are considered the leading cause of cancer-associated deaths. While clinically applied drugs have demonstrated to efficiently remove the primary tumor, metastases remain poorly accessible. To overcome this limitation, herein, the development of a theranostic nanomaterial by incorporating a chromophore for imaging and a photosensitizer for treatment of metastatic tumor sites is presented. The mechanism of action reveals that the nanoparticles are able to intervene by local generation of cellular damage through photodynamic therapy as well as by systemic induction of an immune response by immunotherapy upon inhibition of the mTOR signaling pathway which is of crucial importance for tumor onset, progression and metastatic spreading. The nanomaterial is able to strongly reduce the volume of the primary tumor as well as eradicates tumor metastases in a metastatic breast cancer and a multi-drug resistant patient-derived hepatocellular carcinoma models in female mice.

Cyclodextrin: A prospective nanocarrier for the delivery of antibacterial agents against bacteria that are resistant to antibiotics

Supramolecular chemistry introduces us to the macrocyclic host cyclodextrin, which has a hydrophobic cavity. The hydrophobic cavity has a higher affinity for hydrophobic guest molecules and forms host-guest complexation with non-covalent interaction. Three significant cyclodextrin kinds are α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. The most often utilized is β-cyclodextrin (β-CD). An effective weapon against bacteria that are resistant to antibiotics is cyclodextrin. Several different kinds of cyclodextrin nanocarriers (β-CD, HP-β-CD, Meth-β-CD, cationic CD, sugar-grafted CD) are utilized to enhance the solubility, stability, dissolution, absorption, bioavailability, and permeability of the antibiotics. Cyclodextrin also improves the effectiveness of antibiotics, antimicrobial peptides, metallic nanoparticles, and photodynamic therapy (PDT). Again, cyclodextrin nanocarriers offer slow-release properties for sustained-release formulations where steady-state plasma antibiotic concentration is needed for an extended time. A novel strategy to combat bacterial resistance is a stimulus (pH, ROS)-responsive antibiotics released from cyclodextrin carrier. Once again, cyclodextrin traps autoinducer (AI), a crucial part of bacterial quorum sensing, and reduces virulence factors, including biofilm formation. Cyclodextrin helps to minimize MIC in particular bacterial strains, keep antibiotic concentrations above MIC in the infection site and minimize the possibility of antibiotic and biofilm resistance. Sessile bacteria trapped in biofilms are more resistant to antibiotic therapy than bacteria in a planktonic form. Cyclodextrin also involves delivering antibiotics to biofilm and resistant bacteria to combat bacterial resistance.