Rose Bengal–Amphiphilic Peptide Conjugate for Enhanced Photodynamic Therapy of Malignant Melanoma

pH-Induced conversion of bolaamphiphilic vesicles to reduction-responsive nanogels for enhanced Nile Red and Rose Bengal delivery

This study details the preparation and investigation of molecular nanogels formed by the self-assembly of bolaamphiphilic dipeptide derivatives containing a reduction-sensitive disulfide unit. The described bolaamphiphiles, featuring amino acid terminal groups, generate cationic vesicles at pH 4, which evolve into gel-like nanoparticles at pH 7. The critical aggregation concentration has been determined, and the nanogels' size and morphology have been characterized through Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Circular Dichroism (CD) spectroscopy reveals substantial molecular reconfigurations accompanying the pH shift. These nanogels enhance the in vitro cellular uptake of the lipophilic dye Nile Red and the ionic photosensitizer Rose Bengal into Human colon adenocarcinoma (HT-29) cells, eliminating the need for organic co-solvents in the former case. Fluorescence measurements with Nile Red as a probe indicate the reduction-sensitive disassembly of the nanogels. In photodynamic therapy (PDT) applications, Rose Bengal-loaded nanogels demonstrate notable improvements, with flow cytometry analysis evidencing increased apoptotic activity in the study with HT-29 cells.

Naphtho[1,8-ef]isoindole-7,8,10(9H)-trione as Novel Theranostic Agents for Photodynamic Therapy and Multi-Subcellular Organelles Localization

A series of naphtho[1,8-ef]isoindole-7,8,10(9H)-trione derivatives as novel theranostic agents for photodynamic therapy and multi-subcellular organelles localization were designed and synthesized. Most of them possess moderate fluorescence quantum yield and long wavelength absorption simultaneously, which made them possible for dual effects of imaging and therapy. Notably, compounds 7 b and 7 d exhibited significant light-toxicity but slight dark-toxicity. Confocal fluorescence microscopy experiments demonstrated that compound 7 b can locate and image in special multi-subcellular organelles. All the research results implied that naphtho[1,8-ef] isoindole-7,8,10(9H)-trione derivatives can be applied as a new series of theranostic agents with the characteristics of photodynamic therapy and multi-subcellular organelles imaging.

Photo-sensitive peptide inducing targeted cross-linking in a one-step and reagent-, enzyme- and antibody-free detection of SARS-Cov-2 marker protein

Modern biosensing technology plays a crucial role in combating the spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). However, the associated assays remain costly, considering their extensive daily use. In response, we developed a simplified one-step SARS-CoV-2 protease assay that reduces both time and financial expenses. This approach eliminates the need for extra reagents, enzymes, or antibodies. The simplification involves a photo-sensitive Bengal red-tagged substrate peptide, allowing specific cross-linking upon protease-substrate recognition. This process forms a di-tyrosine product with a distinctive fluorescence signal readout, enabling the detection of SARS-CoV-2 in patient serum samples. This method anticipates a major reduction in assay costs in the near future.

Enhancing Precision in Photodynamic Therapy: Innovations in Light-Driven and Bioorthogonal Activation

Over the past few decades, photodynamic therapy (PDT) has evolved as a minimally invasive treatment modality offering precise control over cancer and various other diseases. To address inherent challenges associated with PDT, researchers have been exploring two promising avenues: the development of intelligent photosensitizers activated through light-induced energy transfers, charges, or electron transfers, and the disruption of photosensitive bonds. Moreover, there is a growing emphasis on the bioorthogonal delivery or activation of photosensitizers within tumors, enabling targeted deployment and activation of these intelligent photosensitive systems in specific tissues, thus achieving highly precise PDT. This concise review highlights advancements made over the last decade in the realm of light-activated or bioorthogonal photosensitizers, comparing their efficacy and shaping future directions in the advancement of photodynamic therapy.

Versatile Peptide-Based Nanosystems for Photodynamic Therapy

Photodynamic therapy (PDT) has become an important therapeutic strategy because it is highly controllable, effective, and does not cause drug resistance. Moreover, precise delivery of photosensitizers to tumor lesions can greatly reduce the amount of drug administered and optimize therapeutic outcomes. As alternatives to protein antibodies, peptides have been applied as useful targeting ligands for targeted biomedical imaging, drug delivery and PDT. In addition, other functionalities of peptides such as stimuli responsiveness, self-assembly, and therapeutic activity can be integrated with photosensitizers to yield versatile peptide-based nanosystems for PDT. In this article, we start with a brief introduction to PDT and peptide-based nanosystems, followed by more detailed descriptions about the structure, property, and architecture of peptides as background information. Finally, the most recent advances in peptide-based nanosystems for PDT are emphasized and summarized according to the functionalities of peptide in the system to reveal the design and development principle in different therapeutic circumstances. We hope this review could provide useful insights and valuable reference for the development of peptide-based nanosystems for PDT.

Larvicidal activity of the photosensitive insecticides, methylene blue and rose bengal, in Aedes aegypti and Anopheles gambiae mosquitoes

BACKGROUND

Insecticides are critical for controlling mosquito populations and mitigating the spread of vector-borne disease, but their overuse has selected for resistant populations. A promising alternative to classical chemical insecticides is photosensitive molecules - here called photosensitive insecticides or PSIs - that when ingested and activated by light, generate broadly toxic reactive oxygen species. This mechanism of indiscriminate oxidative damage decreases the likelihood that target site modification-based resistance evolves. Here, we tested whether the PSIs, methylene blue (MB) and rose bengal (RB), are viable insecticides across the mosquito lineage.

RESULTS

MB and RB are phototoxic to both Aedes aegypti and Anopheles gambiae at micromolar concentrations, with greatest toxicity when larvae are incubated in the dark with the PSIs for 2 h prior to photoactivation. MB is ten times more toxic than RB, and microscopy-based imaging suggests that this is because ingested MB escapes the larval gut and disperses throughout the hemocoel whereas RB remains confined to the gut. Adding food to the PSI-containing water has a bidirectional, concentration-dependent effect on PSI toxicity; toxicity increases at high concentrations but decreases at low concentrations. Finally, adding sand to the water increases the phototoxicity of RB to Ae. aegypti.

CONCLUSION

MB and RB are larvicidal via a light activated mechanism, and therefore, should be further investigated as an option for mosquito control. © 2023 Society of Chemical Industry.

A new ratiometric fluorescence nanosensor based on NaYF4:3%Er@NaYF4 upconversion nanoparticles for sensitive determination of Rose Bengal in water

Rose Bengal (RB) is used as a sensitizer in ambient water due to its property of catalyzing the production of singlet oxygen (1O2). However, this property also brings phototoxicity and carcinogenicity. The NaYF4:3%Er@NaYF4 core-shell upconversion nanoparticles (UCNPs) with higher upconversion efficiency was synthesized to detect RB in ambient water. Due to fluorescence resonance energy transfer (FRET) between RB and UCNPs, the upconversion fluorescence at 538 nm emitted by UCNPs was quenched by the RB, while the emission at 566 nm of RB raised. In the best conditions, the ratiometric emission intensity F566/F538 was positively proportional to RB concentration and the linear range was 0.04-15.0 μg·mL-1 (R2 = 0.996). The detection limit (S/N = 3) of RB was 2.46 ng·mL-1. The recoveries ranged from 99.0% to 105.6% (relative standard deviation 0.97-3.24%, n = 3) in tap water and 100.3%-104.9% (relative standard deviation 0.66-1.94%, n = 3) in lake water. This proposed method exhibits lower detection limit and larger linear, which possesses practical application value to the detection of RB in water.

Biocompatible metallosurfactant-based nanocolloid-loaded Rose Bengal with excellent singlet oxygen-induced phototoxicity efficiency against cancer cells

Photodynamic therapy (PDT) is facing challenges such as poor solubility, precise delivery, self-aggregation, and photobleaching of photosensitizers with cancer cells due to their less tendency to accumulate in tumor tissues. To address these challenges, we have explored a Rose Bengal (RB)-loaded metallocatanionic vesicles (MCVs) nanosystem for the phototoxicity of cancer cells. Different sets of MCVs were prepared by two different cationic single-chain metallosurfactants, i.e., hexadecylpyridinium trichlorocuprate (CuCPC I) and hexadecylpyridinium trichloroferrate (FeCPC I) in combination with anionic double-chain sodium bis(2-ethylhexyl)sulfosuccinate (AOT) surfactant in phosphate buffer saline of pH 7.4. The RB-loaded CuCPC I:AOT and FeCPC I:AOT vesicles enhanced the maximum singlet oxygen (¹O₂) generation by 1-fold and 3-fold, respectively, compared to pure RB. Upon irradiation with a 532 nm laser for 10 min, these RB-loaded CuCPC I:AOT and FeCPC I:AOT MCVs significantly decreased the metabolic activity of U-251 cells by 70% and 85% at MCVs concentration of 0.75 μM, respectively. Furthermore, RB-loaded MCVs showed the highest intracellular ¹O₂-mediated membrane damage and cell-killing effect as confirmed by singlet oxygen sensor green and differential nuclear staining assay, which is attributed to the cellular uptake profile of different RB-loaded MCVs fractions. Caspase 3/7 assay confirmed the apoptotic pathway of cell death by activating caspase. Therefore, the photoactivation of RB-loaded MCVs led to a significant reduction in the viability of U-251 cells (maximum 85%), which resulted in cell death. Our study demonstrated the advantage of using these dual-charge and biocompatible metallocatanionic vesicles as a promising delivery system of photodynamic therapy that can enhance ¹O₂ generation from PS and can be further utilized in photomedicine.

Fluorescence-Coupled Techniques for Determining Rose Bengal in Dermatological Formulations and Their Application to Ex Vivo Skin Deposition Studies

Rose Bengal (RB) is a fluorescent dye with several potential biomedical applications, particularly in dermatology. Due to RB's poor physicochemical properties, several advanced delivery systems have been developed as a potential tool to promote its permeation across the skin. Nevertheless, no validated quantitative method to analyse RB within the skin is described in the literature. Considering RB exhibits a conjugated ring system, the current investigation proposes fluorescence-based techniques beneficial for qualitatively and quantitatively determining RB delivered to the skin. Notably, the development and validation of a fluorescence-coupled HPLC method to quantify RB within the skin matrix are herein described for the first time. The method was validated based on the ICH, FDA and EMA guidelines, and the validated parameters included specificity, linearity, LOD, LLOQ, accuracy and precision, and carry-over and dilution integrity. Finally, the method was applied to evaluate RB's ex vivo permeation and deposition profiles when loaded into dermatological formulations. Concerning qualitative determination, multiphoton microscopy was used to track the RB distribution within the skin strata, and fluorescence emission spectra were investigated to evaluate RB's behaviour when interacting with different environments. The analytical method proved specific, precise, accurate and sensitive to analyse RB in the skin. In addition, qualitative side-analytical techniques were revealed to play an essential role in evaluating the performance of RB's dermatological formulation.

Chemical Control of Mosquitoes and the Pesticide Treadmill: A Case for Photosensitive Insecticides as Larvicides

Insecticides reduce the spread of mosquito-borne disease. Over the past century, mosquito control has mostly relied on neurotoxic chemicals-such as pyrethroids, neonicotinoids, chlorinated hydrocarbons, carbamates and organophosphates-that target adults. However, their persistent use has selected for insecticide resistance. This has led to the application of progressively higher amounts of insecticides-known as the pesticide treadmill-and negative consequences for ecosystems. Comparatively less attention has been paid to larvae, even though larval death eliminates a mosquito's potential to transmit disease and reproduce. Larvae have been targeted by source reduction, biological control, growth regulators and neurotoxins, but hurdles remain. Here, we review methods of mosquito control and argue that photoactive molecules that target larvae-called photosensitive insecticides or PSIs-are an environmentally friendly addition to our mosquitocidal arsenal. PSIs are ingested by larvae and produce reactive oxygen species (ROS) when activated by light. ROS then damage macromolecules resulting in larval death. PSIs are degraded by light, eliminating environmental accumulation. Moreover, PSIs only harm small translucent organisms, and their broad mechanism of action that relies on oxidative damage means that resistance is less likely to evolve. Therefore, PSIs are a promising alternative for controlling mosquitoes in an environmentally sustainable manner.

Targeting Microenvironment of Melanoma and Head and Neck Cancers in Photodynamic Therapy

Background:

Photodynamic therapy (PDT), in comparison to other skin cancers, is still far less effective for melanoma, due to the strong absorbance and the role of melanin in cytoprotection. The tumour microenvironment (TME) has a significant role in tumour progression, and the hypoxic TME is one of the main reasons for melanoma progression to metastasis and its resistance to PDT. Hypoxia is also a feature of solid tumours in the head and neck region that indicates negative prognosis.

Objective:

The aim of this study was to individuate and describe systematically the main strategies in targeting the TME, especially hypoxia, in PDT against melanoma and head and neck cancers (HNC), and assess the current success in their application.

Methods:

PubMed was used for searching, in MEDLINE and other databases, for the most recent publications on PDT against melanoma and HNC in combination with the TME targeting and hypoxia.

Results:

In PDT for melanoma and HNC, it is very important to control hypoxia levels, and amongst the different approaches, oxygen self-supply systems are often applied. Vascular targeting is promising, but to improve it, optimal drug-light interval, and formulation to increase the accumulation of the photosensitiser in the tumour vasculature, have to be established. On the other side, the use of angiogenesis inhibitors, such as those interfering with VEGF signalling, is somewhat less successful than expected and needs to be further investigated.

Conclusion:

The combination of PDT with immunotherapy by using multifunctional nanoparticles continues to develop and seems to be the most promising for achieving a complete and lasting antitumour effect.

Spectroscopy study of dimerization of fluorone dyes in AOT reverse micelles

The dimerization processes and its thermodynamic parameters of fluoronic dyes (fluorescein (F), eosin (E), erythrosine (ER), bengal rose (BR)) in reverse micelles of AOT with different hydrodynamic radius R_h are studied. The dimerization constants and its efficiency (the degree of dimerization of dye molecules (1-X)) were determined from the experimental data. It is found that an increase in the intercombination conversion due to the heavy atom effect leads to an increase of the value of (1-X). At the same time, the heavy atom effect affects the dye dimerization process for all the studied values of R_h. The linear dependence of (1-X) on R_h is observed. The slope of this dependence is affected by both the mass of the internal heavy atom and the charge of the anionic forms of dyes. It was found that there is a different structure of dye dimers for different R_h for all the studied systems - different angles α between the molecules in the dimer. A linear dependence of α on R_h is observed. At the same time, the growth gradients α(R_h) practically do not differ for F, E, and BR and they are of the greatest importance for the studied water-micellar solutions of dyes. The growth of α from R_h is insignificant for ER. The thermodynamic parameters (such as Gibbs potential ΔG, enthalpy (ΔH and entropy ΔS) were calculated from the experimentally measured dependences of the dimerization constant on the temperature. ΔH < 0 and ΔS < 0 in micellar solutions of the studied dyes at all values of R_h, that indicates that the dimerization reaction in the studied systems is controlled by enthalpy. The obtained linear relationship between TΔS and ΔH indicates the existence of enthalpy-entropy compensation in the dimeric reactions of the molecules of the studied dyes. The linear correlation observed between the values of TΔS and ΔH allowed us to establish that the higher the molecular weight of the halogen in the dye molecule, the more effectively an increase in ΔH contributes to the dimeric stability.

"On-Demand" Antimicrobial Photodynamic Activity through Supramolecular Photosensitizers Built with Rose Bengal and (p-Vinylbenzyl)triethylammomium Polycation Derivatives

The antimicrobial photodynamic activity (aPDA) in fungal and bacterial strains of supramolecular adducts formed between the anionic photosensitizer (PS) Rose Bengal (RB^2-) and aromatic polycations derived from (p-vinylbenzyl)triethylammonium chloride was evaluated. Stable supramolecular adducts with dissociation constants K_d ≈ 5 μM showed photosensitizing properties suitable for generating singlet oxygen (Φ_Δ = 0.5 ± 0.1) with the added advantage of improving the photostability of the xanthenic dye. However, the aPDA of both free and supramolecular RB^2- was highly dependent on the type of microorganism treated, indicating the importance of specific interactions between the different cell wall structures of the microbe and the PSs. Indeed, in the case of Gram-positive Staphylococcus aureus, the aPDA of molecular and supramolecular PSs was highly effective. Instead, in the case of Gram-negative Escherichia coli, only the RB^2-:polycation adducts showed aPDA, while RB^2- alone was inefficient, but in the case of Candida tropicalis, the opposite behavior was observed. Therefore, the present results indicate the potential of supramolecular chemistry to obtain aPDA à la carte depending on the target microbe and the PS properties.

Electrochemical benzylic C-H arylation of xanthenes and thioxanthenes without catalyst and oxidant

A catalyst-free and oxidant-free C-H arylation of xanthenes and thioxanthenes using electrochemistry has been developed, which affords a number of cross-coupling products in moderate to good yields. This method is...

Nanoparticle-Based Drug Delivery Systems for Photodynamic Therapy of Metastatic Melanoma: A Review

Metastatic melanoma (MM) is a skin malignancy arising from melanocytes, the incidence of which has been rising in recent years. It poses therapeutic challenges due to its resistance to chemotherapeutic drugs and radiation therapy. Photodynamic therapy (PDT) is an alternative non-invasive modality that requires a photosensitizer (PS), specific wavelength of light, and molecular oxygen. Several studies using conventional PSs have highlighted the need for improved PSs for PDT applications to achieve desired therapeutic outcomes. The incorporation of nanoparticles (NPs) and targeting moieties in PDT have appeared as a promising strategy to circumvent various drawbacks associated with non-specific toxicity, poor water solubility, and low bioavailability of the PSs at targeted tissues. Currently, most studies investigating new developments rely on two-dimensional (2-D) monocultures, which fail to accurately mimic tissue complexity. Therefore, three-dimensional (3-D) cell cultures are ideal models to resemble tumor tissue in terms of architectural and functional properties. This review examines various PS drugs, as well as passive and active targeted PS nanoparticle-mediated platforms for PDT treatment of MM on 2-D and 3-D models. The overall findings of this review concluded that very few PDT studies have been conducted within 3-D models using active PS nanoparticle-mediated platforms, and so require further investigation.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Efficient Photodynamic Therapy against Gram-Positive and Gram-Negative Bacteria Using Rose Bengal Encapsulated in Metallocatanionic Vesicles in the Presence of Visible Light

Significant consumption of antibiotics has generated multidrug resistance in bacteria, which is a major menace to human beings. Antibacterial photodynamic therapy (aPDT) is a progressing technique for inhibition of bacterial infection with minimal side effects. Metals and delivering agents play a major role in aPDT efficiency. Herein, we report a formulation to enrich the antibacterial photodynamic therapy utilizing metallocatanionic vesicles (MCVs) against both Gram-positive and Gram-negative bacteria. These MCVs were synthesized by utilizing iron-based double-chain metallosurfactant [FeCPC(II)] as a cationic surfactant and AOT, a double-chain anionic surfactant. These synthesized MCV fractions were characterized by distinct techniques like DLS, zeta potential, FE-SEM, confocal microscopy, SAXS, and UV-Visible spectroscopy. Polyhedral-shaped MCVs with a size of 200 nm were formed, wherein the charge and size of the catanionic vesicle can be controlled by varying the mixing ratios. Both Gram-positive bacteria, i.e., methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria, i.e., Escherichia coli (E. coli), were used for aPDT using Rose Bengal (RB) as a photosensitizer (PS) encapsulated in MCVs in the presence of a 532 nm wavelength laser. The aPDT against bacterial cells was evaluated for both dark and light toxicities. Pure MCVs also exhibited good antibacterial properties; however, much enhancement was observed in the presence of RB encapsulated in MCVs under light, where eradication of bacteria (E. coli and MRSA) was achieved in 30 min. The observations demonstrated that it is the presence of metal that enhances the singlet oxygen quantum yield of RB and MCVs help in retarding self-quenching and enhanced solubilization of RB. The cationic surfactant-rich fraction shows strong adhesion toward bacteria via electrostatic interactions. The outcome of this research shows that these newly fabricated metal-based metallocatanionic vesicles were effective against both Gram-positive and Gram-negative bacteria using aPDT and must be exploited for clinical applications as well as an alternative for antibiotics in the future.

Hydroxy-corrole and its gallium(III) complex as new photosensitizer for photodynamic therapy against breast carcinoma

Three mono-hydroxy corroles 1-3 and their gallium(III) complexes Ga1-3 were synthesized, and their photodynamic antitumour activities towards breast cancer cells were investigated. All corroles showed excellent cytotoxicity against the MDA-MB-231 and 4T1 cell lines upon light irradiation at 625 nm. Ga3 exhibited excellent phototoxicity and selectivity against MDA-MB-231 cells, with an IC₅₀ of 0.06 ± 0.03 μM and a selective index value of 1338.83 (relative to human normal Huvec cells). The performance of Ga3 was even better than that of the clinical photodynamic therapy drug m-THPC. A preliminary mechanistic investigation revealed that corrole 3 and Ga3 were mainly located in the cytoplasm. Upon irradiation, they could generate intracellular reactive oxygen to destroy the mitochondrial membrane potential and arrest the cell cycle at the sub-G1 phase. Flow cytometry revealed that corrole 3 and Ga3 induced cancer cell apoptosis after photodynamic treatment. Corrole 3 and Ga3 displayed negligible cytotoxicity in the dark. These results suggest that corrole 3 and Ga3 are promising candidates for use in the photodynamic therapy of breast cancer.

Oxidative Stress and Photodynamic Therapy of Skin Cancers: Mechanisms, Challenges and Promising Developments

Ultraviolet radiation is one of the most pervasive environmental interactions with humans. Chronic ultraviolet irradiation increases the danger of skin carcinogenesis. Probably, oxidative stress is the most important mechanism by which ultraviolet radiation implements its damaging effects on normal cells. However, notwithstanding the data referring to the negative effects exerted by light radiation and oxidative stress on carcinogenesis, both factors are used in the treatment of skin cancer. Photodynamic therapy (PDT) consists of the administration of a photosensitiser, which undergoes excitation after suitable irradiation emitted from a light source and generates reactive oxygen species. Oxidative stress causes a condition in which cellular components, including DNA, proteins, and lipids, are oxidised and injured. Antitumor effects result from the combination of direct tumour cell photodamage, the destruction of tumour vasculature and the activation of an immune response. In this review, we report the data present in literature dealing with the main signalling molecular pathways modified by oxidative stress after photodynamic therapy to target skin cancer cells. Moreover, we describe the progress made in the design of anti-skin cancer photosensitisers, and the new possibilities of increasing the efficacy of PDT via the use of molecules capable of developing a synergistic antineoplastic action.