Femtosecond pulsed laser photodynamic therapy activates melanin and eradicates malignant melanoma.

Photodynamic therapy (PDT) relies on a series of photophysical and photochemical reactions leading to cell death. While effective for various cancers, PDT has been less successful in treating pigmented melanoma due to high light absorption by melanin. Here, this limitation is addressed by 2-photon excitation of the photosensitizer (2p-PDT) using ~100 fs pulses of near-infrared laser light. A critical role of melanin in enabling rather than hindering 2p-PDT is elucidated using pigmented and non-pigmented murine melanoma clonal cell lines in vitro. The photocytotoxicities were compared between a clinical photosensitizer (Visudyne) and a porphyrin dimer (Oxdime) with ~600-fold higher σ2p value. Unexpectedly, while the 1p-PDT responses are similar in both cell lines, 2p activation is much more effective in killing pigmented than non-pigmented cells, suggesting a dominant role of melanin 2p-PDT. The potential for clinical translational is demonstrated in a conjunctival melanoma model in vivo, where complete eradication of small tumors was achieved. This work elucidates the melanin contribution in multi-photon PDT enabling significant advancement of light-based treatments that have previously been considered unsuitable in pigmented tumors.

Photodynamic treatment of malignant melanoma with structured light: in silico Monte Carlo modeling.

In this report, we propose a novel strategy for the photodynamic approach to the treatment of melanoma, aiming to mitigate the excessive absorption and consequent thermal effects. The cornerstone of this approach is an innovative structured illumination technique that optimizes light delivery to the tissue. The methodology of this in silico study involves the development of an optical model of human skin with the presence of melanoma and an accurate simulation technique of photon transport within the complex turbid scattering medium. To assess the effectiveness of our proposed strategy, we introduced a cost function reflecting the irradiated volume and optical radiation absorption within the target area/volume occupied by malformation. By utilizing the cost function, we refine the offset illumination parameters for a variety of target system parameters, ensuring increased efficiency of photodynamic therapy. Our computer simulation results introduce a promising new path towards improved photodynamic melanoma treatments, potentially leading to better therapeutic outcomes and reduced side effects. Further experimental validation is needed to confirm these theoretical advancements, which could contribute towards revolutionizing current melanoma photodynamic treatment methodologies.

Photoantimicrobial chitosan-gelatin-pomegranate peel extract films for strawberries preservation: From microbiological analysis to in vivo safety assessment.

This study aimed to investigate the application of biopolymeric materials (chitosan, gelatin, and pomegranate peel extract as photosensitizer) and antimicrobial photodynamic therapy (aPDT) on the physicochemical and microbial safety of strawberries. The photosensitizer potential of the materials was confirmed by a light-dose-dependent photobleaching profile. The application of light (525 nm; 50 J cm-2) decreased by >2 log CFU mL-1 the survival of Staphylococcus aureus on the surface of the photoactive-biopolymeric films. Moreover, the materials did not present in vivo cytotoxicity using Danio rerio (Zebrafish) as well as cytophytotoxic, genotoxic, or mutagenic potentials against Allium cepa plant model, which points out their safety to be used as films without posing a risk to the humans and the environment. The photoactive-polymeric coatings were able to maintain the strawberries weight, and the association with green light was 100 % effective in delaying fungal contamination. These coated-strawberries presented a significant reduction in S. aureus survival after light application (5.47-4.34 log CFU mL-1). The molecular level analysis of the photoactive compound cyanidin-3-glucoside indicates absorption on UV-Vis consistent with aPDT action. Therefore, this study showed that the antimicrobial effects of aPDT combined with photoactive-biopolymeric coatings were enhanced, while the quality of the strawberries was maintained.

Recovering the susceptibility of antibiotic-resistant bacteria using photooxidative damage.

Multidrug-resistant bacteria are one of the most serious threats to infection control. Few new antibiotics have been developed; however, the lack of an effective new mechanism of their action has worsened the situation. Photodynamic inactivation (PDI) can break antimicrobial resistance, since it potentiates the effect of antibiotics, and induces oxidative stress in microorganisms through the interaction of light with a photosensitizer. This paper addresses the application of PDI for increasing bacterial susceptibility to antibiotics and helping in bacterial persistence and virulence. The effect of photodynamic action on resistant bacteria collected from patients and bacteria cells with induced resistance in the laboratory was investigated. Staphylococcus aureus resistance breakdown levels for each antibiotic (amoxicillin, erythromycin, and gentamicin) from the photodynamic effect (10 µM curcumin, 10 J/cm2) and its maintenance in descendant microorganisms were demonstrated within five cycles after PDI application. PDI showed an innovative feature for modifying the degree of bacterial sensitivity to antibiotics according to dosages, thus reducing resistance and persistence of microorganisms from standard and clinical strains. We hypothesize a reduction in the degree of antimicrobial resistance through photooxidative action combats antibiotic failures.

Synergic vascular photodynamic activity by methylene blue-curcumin supramolecular assembly.

A supramolecular assembly was obtained by combining methylene blue (MB) with a natural plant extract, curcumin (Curc), in a stoichiometric ratio of 1:4 in aqueous solution (90% PBS + 10% ethanol) at room temperature. The MB-Curc supramolecular assembly was evidenced by absorption and fluorescence spectroscopies, and the stoichiometry and bonding constant were obtained using Cielens model. Its stability and photostability were evaluated by chromatographic analysis and UV-Vis absorption. The MB-Curc avoids the aggregation of both isolated compounds and efficiently produces singlet oxygen (ΦΔ= 0.52 ± 0.03). Its potential for photodynamic antiangiogenic treatments was evaluated through the vascular effect observed in chicken chorioallantoic membrane (CAM) assay. The results showed intense damage in CAM vascular network by MB-Curc after irradiation, which is higher than the effect of isolated compounds, indicating a synergistic vascular effect. This combination can be essential to prevent cancer revascularization after photodynamic application and improve the efficacy of this approach. The characteristics exhibited by MB-Curc make it a potential candidate for use in cancer treatments through photodynamic antiangiogenic therapy.

Structural basis of antibacterial photodynamic action of curcumin against S. aureus.

Antimicrobial photodynamic therapy (aPDT) is an alternative tool to commercial antibiotics for the inactivation of pathogenic bacteria (e.g., S. aureus). However, there is still a lack of understanding of the molecular modeling of the photosensitizers and their mechanism of action through oxidative pathways. Herein, a combined experimental and computational evaluation of curcumin as a photosensitizer against S. aureus was performed. The radical forms of keto-enol tautomers and the energies of curcumin's frontier molecular orbitals were evaluated by density functional theory (DFT) to point out the photodynamic action as well as the photobleaching process. Furthermore, the electronic transitions of curcumin keto-enol tautomers were undertaken to predict the transitions as a photosensitizer during the antibacterial photodynamic process. Moreover, molecular docking was used to evaluate the binding affinity with the S. aureus tyrosyl-tRNA synthetase as the proposed a target for curcumin. In this regard, the molecular orbital energies show that the curcumin enol form has a character of 4.5% more basic than the keto form - the enol form is a more promising electron donor than its tautomer. Curcumin is a strong electrophile, with the enol form being 4.6% more electrophilic than its keto form. In addition, the regions susceptible to nucleophilic attack and photobleaching were evaluated by the Fukui function. Regarding the docking analysis, the model suggested that four hydrogen bonds contribute to the binding energy of curcumin's interaction with the ligand binding site of S. aureus tyrosyl-tRNA synthetase. Finally, residues Tyr36, Asp40, and Asp177 contact curcumin and may contribute to orienting the curcumin in the active area. Moreover, curcumin presented a photoinactivation of 4.5 log unit corroborating the necessity of the combined action of curcumin, light, and O2 to promote the photooxidation damage of S. aureus. These computational and experimental data suggest insights regarding the mechanism of action of curcumin as a photosensitizer to inactivate S. aureus bacteria.

Nanostructure-Driven Indocyanine Green Dimerization Generates Ultra-Stable Phototheranostics Nanoparticles.

Indocyanine green (ICG) is the only near-infrared (NIR) dye approved for clinical use. Despite its versatility in photonic applications and potential for photothermal therapy, its photobleaching hinders its application. Here we discovered a nanostructure of dimeric ICG (Nano-dICG) generated by using ICG to stabilize nanoemulsions, after which ICG enabled complete dimerization on the nanoemulsion shell, followed by J-aggregation of ICG-dimer, resulting in a narrow, red-shifted (780 nm→894 nm) and intense (≈2-fold) absorbance. Compared to ICG, Nano-dICG demonstrated superior photothermal conversion (2-fold higher), significantly reduced photodegradation (-9.6 % vs. -46.3 %), and undiminished photothermal effect (7 vs. 2 cycles) under repeated irradiations, in addition to excellent colloidal and structural stabilities. Following intravenous injection, Nano-dICG enabled real-time tracking of its delivery to mouse tumors within 24 h by photoacoustic imaging at NIR wavelength (890 nm) distinct from the endogenous signal to guide effective photothermal therapy. The unprecedented finding of nanostructure-driven ICG dimerization leads to an ultra-stable phototheranostic platform.

Organ-on-a-Chip for Drug Screening: A Bright Future for Sustainability? A Critical Review.

Globalization has raised concerns about spreading diseases and emphasized the need for quick and efficient methods for drug screening. Established drug efficacy and toxicity approaches have proven obsolete, with a high failure rate in clinical trials. Organ-on-a-chip has emerged as an essential alternative to outdated techniques, precisely simulating important characteristics of organs and predicting drug pharmacokinetics more ethically and efficiently. Although promising, most organ-on-a-chip devices are still manufactured using principles and materials from the micromachining industry. The abusive use of plastic for traditional drug screening methods and device production should be considered when substituting technologies so that the compensation for the generation of plastic waste can be projected. This critical review outlines recent advances for organ-on-a-chip in the industry and estimates the possibility of scaling up its production. Moreover, it analyzes trends in organ-on-a-chip publications and provides suggestions for a more sustainable future for organ-on-a-chip research and production.

Photoantibacterial Poly(vinyl)chloride Films Applying Curcumin Derivatives as Bio-Based Plasticizers and Photosensitizers.

Herein we describe the design of natural curcumin ester and ether derivatives and their application as potential bioplasticizers, to prepare photosensitive phthalate-free PVC-based materials. The preparation of PVC-based films incorporating several loadings of newly synthesized curcumin derivatives along with their standard solid-state characterization is also described. Remarkably, the plasticizing effect of the curcumin derivatives in the PVC material was found to be similar to that observed in previous PVC-phthalate materials. Finally, studies applying these new materials in the photoinactivation of S. aureus planktonic cultures revealed a strong structure/activity correlation, with the photosensitive materials reaching up to 6 log CFU reduction at low irradiation intensities.

Self-Disinfecting Urethral Catheter to Overcome Urinary Infections: From Antimicrobial Photodynamic Action to Antibacterial Biochemical Entities.

Medical-device-related infections are considered a worldwide public health problem. In particular, urinary catheters are responsible for 75% of cases of hospital urinary infections (a mortality rate of 2.3%) and present a high cost for public and private health systems. Some actions have been performed and described aiming to avoid it, including clinical guidelines for catheterization procedure, antibiotic prophylaxis, and use of antimicrobial coated-urinary catheters. In this review paper, we present and discuss the functionalization of urinary catheters surfaces with antimicrobial entities (e.g., photosensitizers, antibiotics, polymers, silver salts, oxides, bacteriophage, and enzymes) highlighting the immobilization of photosensitizing molecules for antimicrobial photodynamic applications. Moreover, the characterization techniques and (photo)antimicrobial effects of the coated-urinary catheters are described and discussed. We highlight the most significant examples in the last decade (2011-2021) concerning the antimicrobial coated-urinary catheter and their potential use, limitations, and future perspectives.

Physicochemical mechanisms of bacterial response in the photodynamic potentiation of antibiotic effects.

Antibiotic failures in treatments of bacterial infections from resistant strains have been a global health concern, mainly due to the proportions they can reach in the coming years. Making microorganisms susceptible to existing antibiotics is an alternative to solve this problem. This study applies a physicochemical method to the standard treatment for modulating the synergistic response towards circumventing the mechanisms of bacterial resistance. Photodynamic inactivation protocols (curcumina 10 µM, 10 J/cm2) and their cellular behavior in the presence of amoxicillin, erythromycin, and gentamicin antibiotics were analyzed from the dynamics of bacterial interaction of a molecule that produces only toxic effects after the absorption of a specific wavelength of light. In addition to bacterial viability, the interaction of curcumin, antibiotics and bacteria were imaged and chemically analyzed using confocal fluorescence microscopy and Fourier-transform infrared spectroscopy (FTIR). The interaction between therapies depended on the sequential order of application, metabolic activity, and binding of bacterial cell surface biomolecules. The results demonstrated a potentiating effect of the antibiotic with up to to 32-fold reduction in minimum inhibitory concentrations and mean reductions of 7 log CFU/ml by physicochemical action at bacterial level after the photodynamic treatment. The changes observed as a result of bacteria-antibiotic interactions, such as membrane permeabilization and increase in susceptibility, may be a possibility for solving the problem of microbial multidrug resistance.

Antimicrobial curcumin-mediated photodynamic inactivation of bacteria in natural bovine casing.

BACKGROUND: Outbreaks related to food contamination by resistant microorganisms is a worldwide concern that, motivates industries and research institutions to search for affordable solutions. Among the solutions that have been proposed, Photodynamic Inactivation (PDI) of microorganisms has gained prominence, among other aspects, because it is easy to apply and does not generate microbial resistance. METHODS: In this study, we used the association between curcumin solubilized with Tween and light in the photodynamic inactivation process, using light-emitting diodes with a wavelength of 430 nm for decontamination S. Typhimurium and K. pneumoniae from bovine casings used as wrappers for meat products. The result was verified by counting and comparing the number of colony-forming units of the treatment concerning the negative control. RESULTS: The solubilizer, Tween 80, used does not change the optical absorption of curcumin. An optical fluence of 150J/cm2 induces a microbial log reduction of 3.8±0.2 and 2.7±0.1 for S. Typhimurium, and K. pneumoniae contaminated guts, respectively. For the 200µM concentration of curcumin, the PDI provided a microbial log reduction of 3.16±0.03 for S. Typhimurium. For K. pneumoniae, the minimal inhibitory concentration of curcumin occurs up to 12.5µM, causing an microbial log reduction of 2.08±0.03. CONCLUSION: Both curcumin and tween are already used as additives in food production and do not pose health risks at the concentrations used. Furthermore, in the case of the material studied, the addition of curcumin favors the organoleptic quality associated with the color of the food, unlike the green or blue photossensitizers. The results pave the way for possible application of curcumin in finished meat products.

Environmentally Safe Photodynamic Control of Aedes aegypti Using Sunlight-Activated Synthetic Curcumin: Photodegradation, Aquatic Ecotoxicity, and Field Trial.

This study reports curcumin as an efficient photolarvicide against Aedes aegypti larvae under natural light illumination. Larval mortality and pupal formation were monitored daily for 21 days under simulated field conditions. In a sucrose-containing formulation, a lethal time 50 (LT50) of 3 days was found using curcumin at 4.6 mg L-1. This formulation promoted no larval toxicity in the absence of illumination, and sucrose alone did not induce larval phototoxicity. The photodegradation byproducts (intermediates) of curcumin were determined and the photodegradation mechanisms proposed. Intermediates with m/z 194, 278, and 370 were found and characterized using LC-MS. The ecotoxicity of the byproducts on non-target organisms (Daphnia, fish, and green algae) indicates that the intermediates do not exhibit any destructive potential for aquatic organisms. The results of photodegradation and ecotoxicity suggest that curcumin is environmentally safe for non-target organisms and, therefore, can be considered for population control of Ae. aegypti.

Breaking down antibiotic resistance in methicillin-resistant Staphylococcus aureus: Combining antimicrobial photodynamic and antibiotic treatments.

The widespread use of antibiotics drives the evolution of antimicrobial-resistant bacteria (ARB), threatening patients and healthcare professionals. Therefore, the development of novel strategies to combat resistance is recognized as a global healthcare priority. The two methods to combat ARB are development of new antibiotics or reduction in existing resistances. Development of novel antibiotics is a laborious and slow-progressing task that is no longer a safe reserve against looming risks. In this research, we suggest a method for reducing resistance to extend the efficacious lifetime of current antibiotics. Antimicrobial photodynamic therapy (aPDT) is used to generate reactive oxygen species (ROS) via the photoactivation of a photosensitizer. ROS then nonspecifically damage cellular components, leading to general impairment and cell death. Here, we test the hypothesis that concurrent treatment of bacteria with antibiotics and aPDT achieves an additive effect in the elimination of ARB. Performing aPDT with the photosensitizer methylene blue in combination with antibiotics chloramphenicol and tetracycline results in significant reductions in resistance for two methicillin-resistant Staphylococcus aureus (MRSA) strains, USA300 and RN4220. Additional resistant S. aureus strain and antibiotic combinations reveal similar results. Taken together, these results suggest that concurrent aPDT consistently decreases S. aureus resistance by improving susceptibility to antibiotic treatment. In turn, this development exhibits an alternative to overcome some of the growing MRSA challenge.

Scaled up and telescoped synthesis of propofol under continuous-flow conditions.

Herein we report a machine-assisted and scaled-up synthesis of propofol, a short-acting drug used in procedural sedation, which is extensively in demand during this COVID-19 pandemic. The continuous-flow protocol proved to be efficient, with great potential for industrial translation, reaching a production up to 71.6 g per day with process intensification (24 h-continuous experiments). We have successfully telescoped a continuous flow approach obtaining 5.74 g of propofol with productivity of 23.0 g/day (6 h-continuous experiment), proving the robustness of the method in both separated and telescoped modes. Substantial progress was also achieved for the in-line workup, which provides greater safety and less waste, also relevant for industrial application. Overall, the synthetic strategy is based on the Friedel-Crafts di-isopropylation of low-cost p-hydroxybenzoic acid, followed by a decarboxylation reaction, giving propofol in up to 84% overall yield and very low by-product formation. The continuous flow synthesis of propofol 3 is presented as a two-step protocol. The isopropylated intermediate 2 was obtained from 4-hydroxybenzoic acid (1) in up 43.8 g, 85% yield and 30 min residence time. Propofol 3 was then obtained in 71.6 g, 87% yield, and 16 min residence time. A safe and cost-competitive machine-assisted protocol is described with a process intensification demonstration (24 h experiments) and a telescoped process intensification (6 h).

Photodisinfection of material surfaces and bacterial skin infections by a detergent loaded with curcumin.

The development of technologies and therapeutic strategies is needed to combat skin infections and pathogenic microorganisms present on material surfaces that are still responsible for serious public health problems. In this study, detergents loaded with curcumin were prepared by a simple approach and characterized by UV-vis spectroscopy and fluorescence spectroscopy. Their antibacterial photodynamic effects were evaluated against Staphylococcus aureus in planktonic medium and in vivo (skin infection model), and showed a reduction up to 8 logs and 2 logs, respectively. Additionally, the curcumin-detergents were applied on photodisinfection of material surfaces such as wood, rubber, and stainless steel resulting in an efficient photoinactivation up to 3 logs. These developed detergents loaded with curcumin can improve the decontamination of material surfaces and skin infections (in vivo) when illuminated.

Synergic dual phototherapy: Cationic imidazolyl photosensitizers and ciprofloxacin for eradication of in vitro and in vivo E. coli infections.

The emergence of new microorganisms with resistance to current antimicrobials is one of the key issues of modern healthcare that must be urgently addressed with the development of new molecules and therapies. Photodynamic inactivation (PDI) in combination with antibiotics has been recently regarded as a promising wide-spectrum therapy for the treatment of localized topical infections. However, further studies are required regarding the selection of the best photosensitizer structures and protocol optimization, in order to maximize the efficiency of this synergic interaction. In this paper, we present results that demonstrate the influence of the structure of cationic imidazolyl-substituted photosensitizers and light on the enhancement of ciprofloxacin (CIP) activity, for the inactivation of Escherichia coli. Structure-activity studies have highlighted the tetra cationic imidazolyl porphyrin IP-H-Me4+ at sub-bactericide concentrations (4-16 nM) as the most promising photosensitizer for combination with sub-inhibitory CIP concentration (<0.25 mg/L). An optimized dual phototherapy protocol using this photosensitizer was translated to in vivo studies in mice wounds infected with E. coli. This synergic combination reduced the amount of photosensitizer and ciprofloxacin required for full E. coli inactivation and, in both in vitro and in vivo studies, the combination therapy was clearly superior to each monotherapy (PDI or ciprofloxacin alone). Overall, these findings highlight the potential of cationic imidazolyl porphyrins in boosting the activity of antibiotics and lowering the probability of resistance development, which is essential for a sustainable long-term treatment of infectious diseases.

Formulations of curcumin and d-mannitol as a photolarvicide against Aedes aegypti larvae: Sublethal photolarvicidal action, toxicity, residual evaluation, and small-scale field trial.

Dengue, Zika, chikungunya, and yellow fever are arboviruses transmitted by Aedes aegypti mosquito. In this regard, a number of techniques have emerged aiming to combat its proliferation. Elimination of Aedes aegypti larvae by photodynamic action has been reported as an efficient approach. In this regard, this study was aimed at synthetize and characterize formulations with different proportions (w/w) of the plant-based photolarvicidal curcumin and d-mannitol (CCD 1-4) and their evaluation on sublethal photolarvicidal efficiency, photodegradation profile,solubility, internalization, elimination time, persistence in simulated field, growth of microorganisms in water and the toxicity using an animal models (Zebrafish). CCD 3 (curcumin:d-mannitol 50:50 w/w) showed the best efficacy (LC50-24h = 0.01 mg/L), and also presented the shortest internalization and longest elimination time, 60 min and 8 days, respectively. This formulation caused an extrusion into the intestine and peritrophic membrane. Moreover, CCD 3 showed a photodegradation of 50% (in 24 h) under white fluorescent lamps. In a small-scale field trial, CCD 3 had a residual time of 14 days and abnormal microbial growth was not observed. Finally, CCD 3 did not present any toxicity in Zebrafish, after exposition for 24 h at 100 mg/L. Overall, these results raise the possibility of reducing virus transmission through the controlled photoinactivation of Aedes aegypti larvae using a non-toxic plant-based formulated photolarvicide.

Tumor radiosensitization by photobiomodulation.

PURPOSE: To investigate the safety of photobiomodulation therapy (PBM) in tumors and its potential as a radiosensitizer when combined with radiotherapy. METHODS: We have performed in vitro experiments in A431 cells to assess proliferation and cell cycle after PBM, as well as clonogenic assay and H2AX-gamma immunolabeling to quantify double strand breaks after the combination of PBM and radiation. In vivo experiments in xenografts included Kaplan-Meier survival analysis, optical coherence tomography (OCT) and histological analysis. RESULTS: PBM did not induce proliferation in vitro, but increased the G2/M fraction by 27% 24h after illumination, resulting in an enhancement of 30% in radiation effect in the clonogenic assay. The median survival of the PBM-RT group increased by 4 days and the hazard ratio was 0.417 (CI 95%: 0.173-1.006) when compared to radiation alone. OCT analysis over time demonstrated that PBM increases tumor necrosis due to radiation, and histological analysis showed that illumination increased cell differentiation and angiogenesis, which may play a role in the synergetic effect of PBM and radiation. CONCLUSION: PBM technique may be one of the most appropriate approaches for radiosensitizing tumors while protecting normal tissue because of its low cost and low training requirements for staff.