Photosensitizer Molecules Research Articles

A smart small molecule as specific fluorescent probe for sensitive recognition of mitochondrial DNA G-Quadruplexes

G-quadruplex (G4) has become an essential target for the therapy of human genetic diseases (cancer included) with important biological functions for regulation and monitoring. In contrast, little information about G-quadruplexes in mitochondria is known due to the limited development of fluorescent ligands for mitochondrial DNA (mtDNA) G4 detection, urging the design of fluorogenic detection ligands. Herein, we designed and synthesized a robust aggregation-induced emission ligand SPN for recognition of mtDNA G4s, which integrates a G4-active photosensitizer (BZT-triphenylamine) molecule and a mitochondrial targeting functional group (lipophilic triphenylphosphonium cation). Using SPN as the mtDNA G4s sensor, we surprisingly found that SPN could achieve sensitive recognition, sensing, and stabilization of the G4s with the detection limit as low as 0.89 nM. SPN can be highly colocalized with mitochondria, allowing monitoring of mtDNA G4s effectively in vitro. Remarkably, the fluorescence intensity in cancer cells is significantly stronger than that in normal cells, suggesting the potential applications of SPN in cancer diagnosis. This study provides a promising example of designing a fluorescent probe targeting and sensing mtDNA G4s and offers a feasible chemical tool for investigating mtDNA G4s.

The Antimicrobial Photoinactivation Effect on Escherichia coli through the Action of Inverted Cationic Porphyrin-Cyclodextrin Conjugates.

Photodynamic action has been used for diverse biomedical applications, such as treating a broad range of bacterial infections. Based on the combination of light, dioxygen, and photosensitizer (PS), the photodynamic inactivation (PDI) approach led to the formation of reactive oxygen species (ROS) and represented a non-invasive, non-toxic, repeatable procedure for pathogen photoinactivation. To this end, different tetrapyrrolic macrocycles, such as porphyrin (Por) dyes, have been used as PSs for PDI against microorganisms, mainly bacteria. Still, there is significant room for improvement, especially new PS molecules. Herein, unsymmetrical new pyridinone (3–5) and thiopyridyl Pors (7) were prepared with α-, β-, or γ-cyclodextrin (CD) units, following their quaternization to perform the corresponding free-base Pors (3a–5a and 7a), and were compared with the already-known Pors 6a and 8a, both bearing thiopyridinium and CD units. These water-soluble porphyrins were evaluated as PSs, and their photophysical and photochemical properties and photodynamic effects on E. coli were assessed. The presence of one CD unit and three positive charges on the Por structure (3a–5a and 7a) enhanced their aqueous solubility. The photoactivity of the cationic Pors 3a–5a and 6a–8a ensured their potential against the Gram-negative bacterium E. coli. Within each series of methoxypyridinium vs thiopyridinium dyes, the best PDI efficiency was achieved for 5a with a bacterial viability reduction of 3.5 log10 (50 mW cm−2, 60 min of light irradiation) and for 8a with a total bacterial viability reduction (>8 log10, 25 mW cm−2, 30 min of light irradiation). Here, the presence of the methoxypyridinium units is less effective against E. coli when compared with the thiopyridinium moieties. This study allows for the conclusion that the peripheral charge position, quaternized substituent type/CD unit, and affinity to the outer bacterial structures play an important role in the photoinactivation efficiency of E. coli, evidencing that these features should be further addressed in the pursuit for optimised PS for the antimicrobial PDI of pathogenic microorganisms.

Photobiocidal-triboelectric nanolayer coating of photosensitizer/silica-alumina for reusable and visible-light-driven antibacterial/antiviral air filters

Outbreaks of airborne pathogens pose a major threat to public health. Here we present a single-step nanocoating process to endow commercial face mask filters with photobiocidal activity, triboelectric filtration capability, and washability. These functions were successfully achieved with a composite nanolayer of silica-alumina (Si-Al) sol–gel, crystal violet (CV) photosensitizer, and hydrophobic electronegative molecules of 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOTES). The transparent Si-Al matrix strongly immobilized the photosensitizer molecules while dispersing them spatially, thus suppressing self-quenching. During nanolayer formation, PFOTES was anisotropically rearranged on the Si-Al matrix, promoting moisture resistance and triboelectric charging of the Si-Al/PFOTES-CV (SAPC)-coated filter. The SAPC nanolayer stabilized the photoexcited state of the photosensitizer and promoted redox reaction. Compared to pure-photosensitizer-coated filters, the SAPC filter showed substantially higher photobiocidal efficiency (∼99.99 % for bacteria and a virus) and photodurability (∼83 % reduction in bactericidal efficiency for the pure-photosensitizer filter but ∼0.34 % for the SAPC filter after 72 h of light irradiation). Moreover, after five washes with detergent, the SAPC filter maintained its photobiocidal and filtration performance, proving its reusability potential. Therefore, this SAPC nanolayer coating provides a practical strategy for manufacturing an antimicrobial and reusable mask filter for use during the ongoing COVID-19 pandemic.

The growth of Escherichia coli cultures under the influence of pheomelanin nanoparticles and a chelant agent in the presence of light.

Growing concern of antibiotic resistance has increased research efforts to find nonspecific treatments to inhibit pathogenic microorganisms. In this regard, photodynamic inactivation is a promising method. It is based on the excitation of a photosensitizer molecule (PS) with UV-Vis radiation to produce reactive oxygen species. The high reactivity of such species nearby the PS leads to oxidation of bacterial cell walls, lipid membranes (lipid peroxidation), enzymes, and nucleic acids, eventually producing cell death. In the last decade, many studies have been carried out with different photosensitizers to suppress the growth of bacteria, fungi, viruses, and malignant tumors. Here, our main motivation is to employ pheomelanin nanoparticles as sensitizers for inhibiting the growth of the Gram-negative bacteria E. coli, exposed to blue and UVA radiation. In order to perform our experiments, we synthesized pheomelanin nanoparticles from L-DOPA and L-cysteine through an oxidation process. We carried out experiments at different particle concentrations and different energy fluences. We found that cultures exposed to UVA at 166 μg/mL and 270 J/cm2, in conjunction with ethylenediaminetetraacetic acid (EDTA) as an enhancer, decreased in the viable count 5 log10. Different reactive oxygen species (singlet oxygen, hydroxyl radicals, and peroxynitrates) were detected using different procedures. Our results suggest that the method reported here is effective against E. coli, which could encourage further investigations in other type of bacteria.

Photosensitive Alignment: Advanced Electronic Paper-Based Devices

In this review we describe the reversible photoalignment effect imposed on the director in nematic liquid crystals that provides an approach for fabrication of advanced optically addressed devices. Several new concepts have been developed to render photosensitive materials during the past decade. Functional soft azo dye compounds exhibiting distinct functionalities in response to polarized light are highly desirable for fabrication of optically rewritable electronic paper. An optically rewritable element base using simple and inexpensive materials can potentially enable the development of novel environmentally friendly, paper-like gadgets with improved functionality over regular electronic paper. We argue that an optically rewritable technique is relevant for some applications, where conventional paper might be irrelevant. In particular, we have tested and discussed several techniques of color and 3D image formation. This strategy for fabrication of novel devices offers versatile methods for visualization. We also show that the intensity modulation of the irradiation light has a potential to generate improved grayscale visualization. This principle is based on the statistical distribution control of photosensitive azo dye molecules, driven by the incident polarized light. Additionally, we discuss the functional characteristics of the developed prototypes.

BODIPY Catalyzes Proximity‐Dependent Histidine Labelling

AbstractThe novel function of BODIPY, a widely used fluorescent probe, as a catalyst for the chemical labelling of histidine is revealed. Singlet oxygen (1O2) produced by the photosensitizer property of BODIPY oxidises histidine residues, and the histidine oxidised by 1O2 is trapped by the nucleophile 1‐methyl‐4‐arylurazole (MAUra). The simple chemical structure of BODIPY facilitates easier modification compared to other photosensitizer molecules and allows catalysis of protein/peptide‐labelling with higher histidine selectivity compared to the ruthenium complex. Owing to the short life of 1O2, the reaction was selectively completed in close proximity with BODIPY. Site‐selective functionalization of the target/antibody was successfully achieved using ligand‐conjugated BODIPY.

Amphiphilic Protoporphyrin IX Derivatives as New Photosensitizing Agents for the Improvement of Photodynamic Therapy.

Photodynamic therapy (PDT) is a non-invasive therapeutic modality based on the interaction between a photosensitive molecule called photosensitizer (PS) and visible light irradiation in the presence of oxygen molecule. Protoporphyrin IX (PpIX), an efficient and widely used PS, is hampered in clinical PDT by its poor water-solubility and tendency to self-aggregate. These features are strongly related to the PS hydrophilic–lipophilic balance. In order to improve the chemical properties of PpIX, a series of amphiphilic PpIX derivatives endowed with PEG550 headgroups and hydrogenated or fluorinated tails was synthetized. Hydrophilic–lipophilic balance (HLB) and log p-values were computed for all of the prepared compounds. Their photochemical properties (spectroscopic characterization, photobleaching, and singlet oxygen quantum yield) were also evaluated followed by the in vitro studies of their cellular uptake, subcellular localization, and photocytotoxicity on three tumor cell lines (4T1, scc-U8, and WiDr cell lines). The results confirm the therapeutic potency of these new PpIX derivatives. Indeed, while all of the derivatives were perfectly water soluble, some of them exhibited an improved photodynamic effect compared to the parent PpIX.

Molecular dynamics simulations and quantitative calculations on photo-responsive behavior of wormlike micelles constructed by gemini surfactant 12–3-12·2Br− and cinnamates with different ortho-substituents

Photo-responsive wormlike micelles constructed by photo-sensitive molecules and surfactants have attracted widespread attention from researchers. The subtle structural changes in photo-sensitive molecules have a significant effect on the photo-responsive behavior of wormlike micelles, while the underlying mechanism of this effect has not been fully investigated. In this work, photo-responsive wormlike micelles were constructed by Gemini surfactant trimethylene-1, 3-bis (dodecyldimethylammonium bromide) and three cinnamates with different ortho-substituents. The effects of ortho-substituents in cinnamates on the photo-responsive behavior of prepared micelles were explored in details by combining the experimental methods with multi-scale modelling. The experimental results have shown that the wormlike micelles containing different cinnamates exhibit different photo-responsive behaviors and the one containing trans-OMCA shows the best photo-responsiveness (viscosity decrease from 1.63 Pa·s to 0.10 Pa·s with morphology transition from wormlike micelles to spherical micelles) due to the highest conversion fraction (0.88) of the trans-OMCA and forward rate constants (1.09) speed under UV irradiation, which have been reconfirmed by quantitative calculation. Furthermore, the effect of UV irradiation time on the morphology of micelles were studied and the conformational transformation behaviors of wormlike micelles under different UV irradiation time were successfully simulated by adjusting the ratio of cis/trans-isomer. The quantitative calculation illustrates that the existence of methoxy and hydroxyl expands the difference in steric hindrance, hydrophilicity and the electrostatic distribution before and after UV irradiation, and increases the reaction equilibrium constant (methoxy is more effective), thereby enhancing photo-responsive ability of wormlike micelles. The present work provides a comprehensive understanding of photo-responsive morphology transition mechanism of wormlike micelles and the effects of structure of photo-sensitive molecule on the photo-responsiveness of wormlike micelles and thus can find a concrete way to optimize the photo-responsive self-assembly system containing surfactants and photo-sensitive molecule, which is of great importance for the design of smart responsive systems and expansion of their applications.

Study of energy transfer processes between rare earth ions and photosensitizer molecules for photodynamic therapy with IR-excitation

Today, photodynamic therapy is one of the most promising minimally invasive methods of treatment of various diseases, including cancer. The main limitation of this method is the insufficient penetration into the tissue of laser radiation used to activate photosensitizer molecules, which makes it difficult to carry out therapy in the treatment of large or deep-seated tumors. In this regard, there is a great interest in the development of new strategies for photodynamic therapy using infrared radiation for excitation, the wavelengths of which fall into the “transparency window” of biological tissues. In this work, it was proposed to use upconversion NaGdF4 :Yb:Er nanoparticles (UCNP), which absorb infrared excitation and serve as a donor that transfers energy to the photosensitizer. Photosens and phthalosens were chosen as the most promising photosensitizers for the study. The aim of this work was to study the energy transfer processes between upconversion nanoparticles doped with rare-earth ions and photosensitizer molecules. in order to excite photosensitizers with IR radiation and carry out photodynamic therapy of deep-seated neoplasms. Using spectroscopic and time-resolved methods, it has been demonstrated that there is an efficient energy transfer between upconversion particles and photosensitizers phthalosens and photosens. The calculated efficiency of energy transfer by the Foerster mechanism was 41% for the UCNP + photosens system and 69% for the UCNP + phthalosens system. It has been experimentally and theoretically proved that there is a binding of photosensitizer molecules with UCNP by means of surfactants, leading to a reduction in the distance between them, due to which effective nonradiative energy transfer is realized. The generation of singlet oxygen by the phthalosens photosensitizer upon excitation by means of energy transfer from UCNP, excited at 980 nm wavelength of, has been demonstrated.

Review on recent trends and prospects in π‐conjugated luminescent aggregates for biomedical applications

AbstractMetal‐free organic molecules with structurally diverse aggregation‐induced emission (AIE) behavior and new functional photophysical properties reveal unique structure–property relationships, especially bright luminescence, and have attracted extensive attention in the past few decades. Despite tremendous progress on fluorescent molecules development, the extended π‐conjugated organic AIE probes with their nanorange self‐assembly, coassembly, unique morphology, high biocompatibility, and light‐harvesting capabilities enable them as potential candidates in numerous translational application perspectives. In particular, a few important classes of AIE light up small molecules, supramolecules, oligomers, polymers, including nanoparticles and photosensitizer molecules, with their emerging properties of thermally activated delayed fluorescence, room temperature phosphorescence, including emission switching stimuli‐responsive behavior and multifunctional properties, have been boosted by the rare features of aggregation at their condensed or solid states. This review highlights salient features of AIE‐based emitters, encompassing molecular design strategies, stimulating photophysical properties, mechanistic aspects, and their efficacy in various electronic and biomedical applications, broadly covering properties of small molecules to oligomers, macromolecules to polymers.

Advances in Management of Bladder Cancer-The Role of Photodynamic Therapy.

Photodynamic therapy (PDT) is a non-invasive and modern form of therapy. It is used in the treatment of non-oncological diseases and more and more often in the treatment of various types of neoplasms in various locations including bladder cancer. The PDT method consists of local or systemic application of a photosensitizer, i.e., a photosensitive compound that accumulates in pathological tissue. Light of appropriate wavelength is absorbed by the photosensitizer molecules, which in turn transfers energy to oxygen or initiates radical processes that leads to selective destruction of diseased cells. The technique enables the selective destruction of malignant cells, as the photocytotoxicity reactions induced by the photosensitizer take place strictly within the pathological tissue. PDT is known to be well tolerated in a clinical setting in patients. In cited papers herein no new safety issues were identified. The development of anti-cancer PDT therapies has greatly accelerated over the last decade. There was no evidence of increased or cumulative toxic effects with each PDT treatment. Many modifications have been made to enhance the effects. Clinically, bladder cancer remains one of the deadliest urological diseases of the urinary system. The subject of this review is the anti-cancer use of PDT, its benefits and possible modifications that may lead to more effective treatments for bladder cancer. Bladder cancer, if localized, would seem to be a good candidate for PDT therapy since this does not involve the toxicity of systemic chemotherapy and can spare normal tissues from damage if properly carried out. It is clear that PDT deserves more investment in clinical research, especially for plant-based photosensitizers. Natural PS isolated from plants and other biological sources can be considered a green approach to PDT in cancer therapy. Currently, PDT is widely used in the treatment of skin cancer, but numerous studies show the advantages of related therapeutic strategies that can help eliminate various types of cancer, including bladder cancer. PDT for bladder cancer in which photosensitizer is locally activated and generates cytotoxic reactive oxygen species and causing cell death, is a modern treatment. Moreover, PDT is an innovative technique in oncologic urology.

Near-Infrared Light-Triggered Generation of Reactive Oxygen Species and Induction of Local Hyperthermia from Indocyanine Green Encapsulated Mesoporous Silica-Coated Graphene Oxide for Colorectal Cancer Therapy

Near-infrared (NIR) light-mediated photothermal therapy (PTT) and photodynamic therapy (PDT) have widely been used for cancer treatment applications. However, a number of limitations (e.g., low NIR absorption capacity of photothermal agents, insufficient loading efficiency of photosensitive molecules) have hindered the widespread use of NIR-mediated cancer therapy. Therefore, we developed a mesoporous silica-coated reduced graphene oxide (rGO) nanocomposite that could provide a high encapsulation rate of indocyanine green (ICG) and enhance PTT/PDT efficiency in vitro and in vivo. The ICG-encapsulated nanocomposite not only enhances the photothermal effect but also generates a large number of tumor toxic reactive oxygen species (ROS). By conjugation of polyethylene glycol (PEG) with folic acid (FA) as a tumor targeting moiety, we confirmed that ICG-encapsulated mesoporous silica (MS)-coated rGO nanocomposite (ICG@MS-rGO-FA) exhibited high colloidal stability and intracellular uptake in folate receptor-expressing CT-26 colorectal cancer cells. Upon NIR laser irradiation, this ICG@MS-rGO-FA nanocomposite induced the apoptosis of only CT-26 cells via enhanced PTT and PDT effects without any damage to normal cells. Furthermore, the ICG@MS-rGO-FA nanocomposite revealed satisfactory tumor targeting and biocompatibility in CT-26 tumor-bearing mice, thereby enhancing the therapeutic effects of PTT and PDT in vivo. Therefore, this tumor-targeted ICG@MS-rGO-FA nanocomposite shows a great potential for phototherapy applications.

Tailoring Aggregation Extent of Photosensitizers to Boost Phototherapy Potency for Eliciting Systemic Antitumor Immunity.

Phototherapy is effective for triggering the immunogenic cell death (ICD) effect. However, its efficacy is limited by low 1 O2 generation and photothermal conversion efficacy due to two irreconcilable obstacles, namely the aggregation-caused-quenching (ACQ) effect and photobleaching. In this work, a discretely integrated nanofabrication (DIN) platform (Pt-ICG/PES) is developed by facile coordination coassembly of cisplatin (Pt), photosensitizer molecules (indocyanine green (ICG)), and polymeric spacer (p(MEO2 MA-co-OEGMA)-b-pSS (PES)). By controlling the ICG/PES feeding ratio, the aggregation of ICG can be easily tailored using PES as an isolator to balance the ACQ effect and photobleaching, thereby maximizing the phototherapy potency of Pt-ICG/PES. With the optimized ratio of each component, Pt-ICG/PES integrates the complementarity of photodynamic therapy, photothermal therapy, and chemotherapeutics to magnify the ICD effect, exerting a synergistic antitumor immunity-promoting effect. Additionally, temperature-sensitive PES enables photothermally guided drug delivery. In a tumor-bearing mouse model, Pt-ICG/PES elicits effective release of danger-associated molecular patterns, dendritic cell maturation, cytotoxic T lymphocytes activation, cytokine secretion, M2macrophage repolarization, and distal tumor suppression, confirming the excellent in situ tumor ICD effect as well as robust systematic antitumor immunity. Ultimately, a versatile DIN strategy is developed to optimize the phototherapeutic efficacy for improving antitumor effects and strengthening systemic antitumor immunity.

A Novel NIR Fluorescent Nanoprobe Targeting HER2-Positive Breast Cancer: Tra-TTR-A.

TTRE, a photosensitizer molecule, has excellent biofluorescence imaging performance and effective antitumor properties for breast cancer. However, its application in breast cancer treatment is limited due to poor tumor selectivity and lack of targeting ability. In this study, TTRE and trastuzumab were combined to synthesize Tra-TTR-A, a novel near-infrared fluorescent nanoprobe for HER2 positive breast cancer. The targeting and antitumor abilities of Tra-TTR-A in breast cancer were also investigated. Like TTRE, Tra-TTR-A has a stable structure with remarkable optical properties and in vivo imaging capacity. However, Tra-TTR-A not only inhibits tumor growth by generating reactive oxygen species but also kills tumor cells by trastuzumab. In this study, Tra-TTR-A, a new type of near-infrared fluorescent nanoprobe that targets HER2-positive breast cancer, was successfully synthesized. Tra-TTR-A could be used in in vivo imaging, targeted photodynamic therapy, and diagnosis and treatment for breast cancer.

BaGdF5 Nanophosphors Doped with Different Concentrations of Eu3+ for Application in X-ray Photodynamic Therapy.

X-ray photodynamic therapy (XPDT) has been recently considered as an efficient alternative to conventional radiotherapy of malignant tissues. Nanocomposites for XPDT typically consist of two components—a nanophosphor which re-emits X-rays into visible light that in turn is absorbed by the second component, a photosensitizer, for further generation of reactive oxygen species. In this study, BaGdF5 nanophosphors doped with different Eu:Gd ratios in the range from 0.01 to 0.50 were synthesized by the microwave route. According to transmission electron microscopy (TEM), the average size of nanophosphors was ~12 nm. Furthermore, different coatings with amorphous SiO2 and citrates were systematically studied. Micro-CT imaging demonstrated superior X-ray attenuation and sufficient contrast in the liver and the spleen after intravenous injection of citric acid-coated nanoparticles. In case of the SiO2 surface, post-treatment core–shell morphology was verified via TEM and the possibility of tunable shell size was reported. Nitrogen adsorption/desorption analysis revealed mesoporous SiO2 formation characterized by the slit-shaped type of pores that should be accessible for methylene blue photosensitizer molecules. It was shown that SiO2 coating subsequently facilitates methylene blue conjugation and results in the formation of the BaGdF5: 10% Eu3+@SiO2@MB nanocomposite as a promising candidate for application in XPDT.

Latest trends on photodynamic disinfection of Gram-negative bacteria: photosensitizer's structure and delivery systems.

Antimicrobial resistance is threatening to overshadow last century's medical advances. Etiological agents of previously eradicated infectious diseases are now resurgent as multidrug-resistant strains, especially for Gram-negative strains. Finding new therapeutic solutions is a real challenge for our society. In this framework, Photodynamic Antimicrobial ChemoTherapy relies on the generation of toxic reactive oxygen species in the presence of light, oxygen, and a photosensitizer molecule. The use of reactive oxygen species is common for disinfection processes, using chemical agents, such as chlorine and hydrogen peroxide, and as they do not have a specific molecular target, it decreases the potential of tolerance to the antimicrobial treatment. However, light-driven generated reactive species result in an interesting alternative, as reactive species generation can be easily tuned with light irradiation and several PSs are known for their low environmental impact. Over the past few years, this topic has been thoroughly studied, exploring strategies based on single-molecule PSs (tetrapyrrolic compounds, dipyrrinate derivatives, metal complexes, etc.) or on conjunction with delivery systems. The present work describes some of the most relevant advances of the last 6years, focusing on photosensitizers design, formulation, and potentiation, aiming for the disinfection of Gram-negative bacteria.

Exploratory insight into the stability of Rhodamine B and crude aqueous spinach extract-based photogalvanic cells: Comparing photo-stability of electrolytes for solar power and storage

All promising solar cell devices including the photo-galvanic cells have to be sustainable and durable in nature to meet the long-term energy needs of society. Photo-galvanic cells are characterized by the two electrodes dipped in the electrolyte solution (consisting of the dye/pigment photo-sensitizer, surfactant, reductant, alkali, and water) capable of simultaneous solar energy conversion and storage. The dye/pigment molecules are prone to photo-decay. In the present work, the photogalvanic cells have been studied with respect to the photo-stability of the electrolyte based on Rhodamine B dye sensitizer and crude aqueous spinach extract sensitizer separately and consequent electrical output over a long time. It has been observed that the photo-sensitizer molecules undergo photo-decay, but, despite this decay, the cell even with the photo-decayed electrolytes has a promising capacity to produce power with storage. The results show a photo-decay of electrolytes based on both the artificial/synthetic dye materials and natural pigment materials.

Silk Fibroin/Poly(vinyl Alcohol) Microneedles as Carriers for the Delivery of Singlet Oxygen Photosensitizers.

Photodynamic therapy (PDT) is a medical treatment in which a combination of a photosensitizing drug and visible light produces highly cytotoxic reactive oxygen species (ROS) that leads to cell death. One of the main drawbacks of PDT for topical treatments is the limited skin penetration of some photosensitizers commonly used in this therapy. In this study, we propose the use of polymeric microneedles (MNs) prepared from silk fibroin and poly(vinyl alcohol) (PVA) to increase the penetration efficiency of porphyrin as possible applications in photodynamic therapy. The microneedle arrays were fabricated from mixtures in different proportions (1:0, 7:3, 1:1, 3:7, and 0:1) of silk fibroin and PVA solutions (7%); the polymer solutions were cast in polydimethylsiloxane (PDMS) molds and dried overnight. Patches containing grids of 10 × 10 microneedles with a square-based pyramidal shape were successfully produced through this approach. The polymer microneedle arrays showed good mechanical strength under compression force and sufficient insertion depth in both Parafilm M and excised porcine skin at different application forces (5, 20, 30, and 40 N) using a commercial applicator. We observe an increase in the cumulative permeation of 5-[4-(2-carboxyethanoyl) aminophenyl]-10,15,20-tris-(4-sulphonatophenyl) porphyrin trisodium through porcine skin treated with the polymer microneedles after 24 h. MNs may be a promising carrier for the transdermal delivery of photosensitizers for PDT, improving the permeation of photosensitizer molecules through the skin, thus improving the efficiency of this therapy for topical applications.

Photodynamic inactivation of Escherichia coli bacteria by cationic photosensitizers

The aim of this work is the study of antibacterial photodynamic inactivation (APDI) of Escherichia coli (on the example of a model E. coli K12 TG1), the influence of the charge of photosensitizer (PS) molecules on the efficiency of binding with these Gram-negative bacteria. The results obtained confirm that PSs based on polycationic phthalocyanines and synthetic bacteriochlorins provide effective photodynamic inactivation of E. coli, much higher than monocationic methylene blue and electro-neutral bacteriochlorin derivative. The efficiency of APDI, assessed by the intensity of bioluminescence of model E. coli K12 TG1 bacteria, correlates with the charge of PS molecules and the efficiency of electrostatic binding of PS to bacterial cells.

Functionalized Nanoparticles Activated by Photodynamic Therapy as an Antimicrobial Strategy in Endodontics: A Scoping Review.

The eradication of endodontic pathogens continues to be the focus of the search for new root canal system (RCS) disinfection strategies. This scoping review provides a comprehensive synthesis of antimicrobial photodynamic therapy (aPDT) using nanoparticles (NPs) as an alternative to optimize RCS disinfection. A systematic search up to March 2021 was carried out using the MEDLINE, EMBASE, Scopus, Lilacs, Central Cochrane Library, and BBO databases. We included studies focused on evaluating the activation of NPs by aPDT in inoculated root canals of human or animal teeth or bacterial cultures in the laboratory. The selection process and data extraction were carried out by two researchers independently. A qualitative synthesis of the results was performed. A total of seventeen studies were included, of which twelve showed a substantial antibacterial efficacy, two assessed the substantivity of the disinfection effect, and three showed low cytotoxicity. No adverse effects were reported. The use of functionalized NPs with photosensitizer molecules in aPDT has been shown to be effective in reducing the bacteria count, making it a promising alternative in endodontic disinfection. Further studies are needed to assess the development of this therapy in in vivo conditions, with detailed information about the laser parameters used to allow the development of safe and standardized protocols.