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.

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.

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.

Avoiding ventilator-associated pneumonia: Curcumin-functionalized endotracheal tube and photodynamic action.

Hospital-acquired infections are a global health problem that threatens patients' treatment in intensive care units, causing thousands of deaths and a considerable increase in hospitalization costs. The endotracheal tube (ETT) is a medical device placed in the patient's trachea to assist breathing and delivering oxygen into the lungs. However, bacterial biofilms forming at the surface of the ETT and the development of multidrug-resistant bacteria are considered the primary causes of ventilator-associated pneumonia (VAP), a severe hospital-acquired infection for significant mortality. Under these circumstances, there has been a need to administrate antibiotics together. Although necessary, it has led to a rapid increase in bacterial resistance to antibiotics. Therefore, it becomes necessary to develop alternatives to prevent and combat these bacterial infections. One possibility is to turn the ETT itself into a bactericide. Some examples reported in the literature present drawbacks. To overcome those issues, we have designed a photosensitizer-containing ETT to be used in photodynamic inactivation (PDI) to avoid bacteria biofilm formation and prevent VAP occurrence during tracheal intubation. This work describes ETT's functionalization with curcumin photosensitizer, as well as its evaluation in PDI against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli A significant photoinactivation (up to 95%) against Gram-negative and Gram-positive bacteria was observed when curcumin-functionalized endotracheal (ETT-curc) was used. These remarkable results demonstrate this strategy's potential to combat hospital-acquired infections and contribute to fighting antimicrobial resistance.

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.

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.

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.

Carbon-Based Materials in Photodynamic and Photothermal Therapies Applied to Tumor Destruction.

Within phototherapy, a grand challenge in clinical cancer treatments is to develop a simple, cost-effective, and biocompatible approach to treat this disease using ultra-low doses of light. Carbon-based materials (CBM), such as graphene oxide (GO), reduced GO (r-GO), graphene quantum dots (GQDs), and carbon dots (C-DOTs), are rapidly emerging as a new class of therapeutic materials against cancer. This review summarizes the progress made in recent years regarding the applications of CBM in photodynamic (PDT) and photothermal (PTT) therapies for tumor destruction. The current understanding of the performance of modified CBM, hybrids and composites, is also addressed. This approach seeks to achieve an enhanced antitumor action by improving and modulating the properties of CBM to treat various types of cancer. Metal oxides, organic molecules, biopolymers, therapeutic drugs, among others, have been combined with CBM to treat cancer by PDT, PTT, or synergistic therapies.

Matter wave speckle observed in an out-of-equilibrium quantum fluid.

We report the results of the direct comparison of a freely expanding turbulent Bose-Einstein condensate and a propagating optical speckle pattern. We found remarkably similar statistical properties underlying the spatial propagation of both phenomena. The calculated second-order correlation together with the typical correlation length of each system is used to compare and substantiate our observations. We believe that the close analogy existing between an expanding turbulent quantum gas and a traveling optical speckle might burgeon into an exciting research field investigating disordered quantum matter.

Overall Results for a National Program of Photodynamic Therapy for Basal Cell Carcinoma: A Multicenter Clinical Study to Bring New Techniques to Social Health Care.

Along the past years, a national program to implement photodynamic therapy (PDT) for nonmelanoma skin cancer (NMSC) was performed over the Brazilian territory. Using a strategy involving companies, national bank, and medical partners, equipment, medication, and protocols were tested in a multicenter study. With results collected over 6 years, we could reach a great deal of advances concerning the use of PDT for skin cancer. We present the overall reached results of the program and discuss several aspects about it, including public politics of treatment. A discussion about advantages of this technique within conditions of health care is placed, comparing PDT with surgery, including an analysis about the implementation of PDT in countries in development as Brazil, considering not only technical but social aspects, as the distribution of medical doctor in the Brazilian territory. The program resulted in a huge dissemination of PDT in Brazil and many countries in Latin America, in a partnership among public politics, universities, companies, and hospitals and clinics and in the insertion of national technologies as option to treat NMSC. Consequence of the program is mainly the continuation of the use of PDT in Brazil and many countries in Latin America.

Photodynamic Therapy Versus Glucose for the Treatment of Telangiectasia: A Randomised Controlled Study in a Rabbit Ear Model.

OBJECTIVES: Telangiectasia is a common venous formation that mainly affects women and causes discomfort, including psychological distress. This study compared photodynamic therapy (PDT) with glucose for vessel sclerosis in a rabbit ear model. METHODS: Thirty-six ears of 18 rabbits were randomly divided into four groups: Group 1: only injection of Photogem (4 mg/mL); Group 2: only light (635 nm, 100 mW/cm2, 8 min, 48 J/cm2); Group 3: glucose 75% injection; Group 4: PDT procedure with injection of Photogem and illumination immediately after. Injections were made into the central ear artery. After injection or sham procedures, manual compression of the marginal vein was maintained for 8 min in all ears. Follow up was immediately after the procedures, and one and six days later. The percentage of length reduction of spider veins, the target vessels, was analysed in digital photographs with Image J software. Ear thermographs were made with a thermocamera device and average temperatures were collected for analysis. Ear biopsies were obtained after six days. Endothelium average, inflammation, fibrosis, necrosis, skin burn, and vascular thrombosis were assessed using a specific score. RESULTS: The mean vessel length reduction was 26% for Group 4, 2.4% for Group 3, .4% for Group 1, and 0 for Group 2, highlighting that in Group 4, the vessel lengths were significantly reduced compared with the other groups (p < .001). In the thermal analysis, in Group 3, the temperature was unchanged from the initial temperature and the central diameter vessel increased after six days, while, in Group 4, the temperature decreased and the vessels were not clearly detected, suggesting a reduction of the vessels and smaller infusion. Histology showed no difference among groups and one case of necrosis was found in Group 4. CONCLUSIONS: PDT was associated with significantly more target vessel sclerosis than glucose injection and controls.

Effect of the Curing Temperature of Dental Composites evaluated with a Fluorescent Dye.

AIM: With the development of the light-emitting diode (LED) to photo-activate composite resin, greater intensities could be reached without greater elevation of temperature in the mass of the composite resin and in the dental structure arisen from the irradiance in comparison to halogen equipments. This new scenario created a necessity to investigate the influence of temperature over the composite polymerization. MATERIALS AND METHODS: Several curing temperatures (Tcure- 0, 25, 50, 75, and 100°C) were used to polymerize a composite resin (Filtek Z250, 3M ESPE) for 40 and 60 s, using the halogen equipment Gnatus Optilight Digital (halogen) and two LEDs that use a new technology to assembly the diodes: LEC 1000 and bright LEC (MM Optics) (LED 1 and LED 2 respectively). The influence of curing temperature, added by the other variables studied, was evaluated using a methodology developed and improved at IFSC/USP, in which the penetration of a fluorescent dye in the body of the photopolymerized composite resin was quantified using fluorescence spectroscopy. RESULTS: According to the final data submitted to an analysis of variance, the presence of two groups of results could be verified: Between 0 and 25°C, both had a great percentage of the dye penetration compared with other Tcure with a variation in penetration from 69.26 ± 8.19% to 90.99 ± 3.38%. In this analysis, the effects of time and temperature were highly notable (p < 0.05) and the lesser value of dye penetration took place at 60 s of photoactivation This penetration was, in average, smaller with the Tcure of 25°C. The results showed that there was an interaction between the equipment and time and between time and temperature; the other group is regarding the Tcure was from 50, 75, and 100°C, despite the p = 0.05, the effect of temperature was notable. The penetration of the dye ranged from 8.87 ± 3.55 to 39.47 ± 8.9%. The effects of equipment and time were highly notable. The penetration with the time of 60 s was in average smaller. Except with the equipment LED 1, the percentages of the dye penetration were greater with the Tcure of 100°C. The smallest average was the Tcure of 50°C and 60 s of photoactivation. CONCLUSION: Based on the available data regarding the influence of curing temperature on the polymerization process of composite resins, was possible to concluded that small increments of heat increased the degree of conversion. We can assume that the energy supply through the generation of heat by the photopolymerizing devices can function as a heating medium for the reagent system by reducing its viscosity and increasing the mobility and agitation of its components. CLINICAL SIGNIFICANCE: The dentist must be aware of the effects that exist between the activation devices on the light output and their heat transmission to the composite and the tooth itself. This heat transmission might create a polymer with better characteristics.

Vortices and turbulence in trapped atomic condensates.

After more than a decade of experiments generating and studying the physics of quantized vortices in atomic gas Bose-Einstein condensates, research is beginning to focus on the roles of vortices in quantum turbulence, as well as other measures of quantum turbulence in atomic condensates. Such research directions have the potential to uncover new insights into quantum turbulence, vortices, and superfluidity and also explore the similarities and differences between quantum and classical turbulence in entirely new settings. Here we present a critical assessment of theoretical and experimental studies in this emerging field of quantum turbulence in atomic condensates.

Interstitial PDT using diffuser fiber-investigation in phantom and in vivo models.

Photodynamic therapy (PDT) has been used for local treatment of several types of tumors. Light penetration of biological tissue is one limiting factor in PDT, decreasing the success rates of the treatment of invasive and solid tumors. In those cases, a possible solution is to use interstitial PDT, in which both diffuser optical fibers are inserted into the tumor. The uniformity of the diffuser emission plays a crucial role in planning the delivery of the appropriate light fluence and in ensuring treatment success. In this study, we characterized a diffuser optical fiber concerning its homogeneity. We showed that the diffuser emission can be inhomogeneous and that the necrosis generated by interstitial PDT using such a diffuser for illumination is asymmetrical in volume as a result. This observation has relevant consequences in achieving success in PDT and phototherapies in general, as the delivered light fluence depends on adequate previous knowledge of the irradiation profile.

A Multicenter Clinical Study of Expected and Unexpected Side Reactions During and After Skin Cancer Treatment by Photodynamic Therapy.

Photodynamic therapy (PDT) has been widely used for oncologic indications, especially nonmelanoma skin cancer such as superficial and nodular basal cell carcinoma (BCC). We present a multicenter clinical study conducted between 2012 and 2014 analyzing the adverse reactions during and after PDT with a standardized protocol in 866 lesions. A total of 728 patients with positive clinical and histopathological diagnosis for BCC with up to 2 cm diameter were treated. The procedure consisted of curettage and topical application of cream containing 20% methyl 5-aminolevulinate. The illumination (630 nm and 150 J/cm2) was performed 3 hours after the cream application. The expected and unexpected effects observed were pain, healing, and inflammatory reactions. The pain intensity was correlated with the anatomical localization of the lesion. The patients reported a higher intensity of pain in lesions located on the head and neck rather than on the trunk and limbs. The number of sessions also influenced the pain response. A total of 83% of patients showed perfect healing and the other 17% presented abnormal healing. PDT plays an important role in BCC because of its low cost, ease of use, and low rate of side effects.

Longitudinal effect of curcumin-photodynamic antimicrobial chemotherapy in adolescents during fixed orthodontic treatment: a single-blind randomized clinical trial study.

White spot lesions are one of the concerns during the fixed orthodontic treatment. Thus, the aim of the present study was to evaluate the antimicrobial/anti-inflammatory effect of curcumin-photodynamic antimicrobial chemotherapy (c-PACT) and chlorhexidine varnish on the plaque accumulation and gingival bleeding in adolescents under fixed orthodontic treatment. A randomized clinical trial was performed with an initial number of 45 patients being distributed into three groups: group I-chlorhexidine varnish 2%, group II-placebo varnish, and group III-c-PACT (curcumin at 1.5 mg.mL(-1)) exposed to blue Light-emitting diode (LED) light at 450 nm (power density = 165 mW.cm(-2), fluency = 96 J.cm(-2), total dose = 150.7 J). The treatments were performed for four consecutive times with an interval of 1 week each. After the interventions, two calibrated examiners (Kappa value = 0.75) analyzed the dental plaque accumulation by plaque index (PI) and gingivitis condition by gingival bleeding index (GBI) with 1 and 3 months of follow-up after the treatments comprised a final sample of 35 patients. No significant difference was found to PI between the groups during baseline and 1-month period. Group III (1.52 ± 0.51) presented significance difference from group I (0.91 ± 0.75) and group II (1.03 ± 0.51) at 3 months of follow-up. In this same period, there was more plaque accumulation with significant statistical difference (P ≤ 0.05) in comparison to the other periods to all studied groups. There was a GBI reduction statistically significant to groups I and III at 1-month follow-up in comparison to other periods. No effect was verified to dental plaque accumulation after the photodynamic application mediated with curcumin activated with a blue LED light.

Comparative effects of photodynamic therapy mediated by curcumin on standard and clinical isolate of Streptococcus mutans.

AIM: The aim of this study was investigate the effect of photodynamic therapy (PDT) using curcumin (C) as a photosensitizing agent irradiated with an LED (L) in the blue wavelength as a light source on a standard and clinical isolate of Streptococcus mutans (S. mutans) in a planktonic suspension model. MATERIALS AND METHODS: Suspensions of both strains were divided into 4 groups as follows: absence of C and L (control group: C-L-), with C and without L (C group: C+L-), absence of C with L (L group: C-L+) and presence of C and L (PDT group: C+L+). Three different concentrations of curcumin (0.75 mg/ml, 1.5 mg/ml and 3 mg/ml) and three light fluences of studied light source (24, 48 and 72 J cm(-2)) were tested. Aliquots of each studied group was plated in BHI agar and submitted to colony forming units counting (CFU/ml) and the data transformed into logarithmical scale. RESULTS: A high photoinactivation rate of more than 70% was verified to standard S. mutans strain submitted to PDT whereas the clinical isolate showed a lower sensitivity to all the associations of curcumin and LED. A slight bacterial reduction was verified to C+L- and C-L+, demonstrating no toxic effects to the isolated application of light and photosensitizer to both S. mutans strains tested. CONCLUSION: Photodynamic therapy using a combination of curcumin and blue LED presented a substantial antimicrobial effect on S. mutans standard strain in a planktonic suspension model with a less pronounced effect on its clinical isolate counterparts due to resistance to this alternative approach. CLINICAL SIGNIFICANCE: Alternative antimicrobial approaches, as photodynamic therapy, should be encouraged due to optimal results against cariogenic bacteria aiming to prevent or treat dental caries.

Photobiological characteristics of chlorophyll a derivatives as microbial PDT agents.

Chlorin-e6 (chl-e6) and a hydrogenated derivative (chl-e6H) were semi-synthesized, and their photophysical properties and photodynamic activity against Escherichia coli, Staphylococcus aureus and Candida albicans evaluated. Methyl pheophorbide-a (Mepheo-a) was obtained from S. maxima using methanolic extraction with acid catalysis (CH3OH­H2SO4). Chlorin-e6 was prepared from Mepheo-a by basic hydrolysis with H2O­acetone and NaOH. Hydrogenated Chlorin-e6 was synthesized by a similar procedure starting from the hydrogenated methyl pheophorbide-a (Mepheo-aH). Photophysical studies were performed in order to determine the singlet oxygen quantum yield of chl-e6H which is higher than that of chl-e6. The microorganism inactivation of chl-e6 and chl-e6H was investigated at two concentrations and three fluence levels. Both chl-e6 and chl-e6H showed microorganism inactivation against Gram-positive bacteria and a fungus.

Validation of photodynamic action via photobleaching of a new curcumin-based composite with enhanced water solubility.

Motivated by the photochemical and photophysical properties of curcumin-based composites, the characteristics of a new curcumin-based water-soluble salt were investigated via absorption and fluorescence spectroscopy. Photobleaching was investigated using a set of LEDs in three different wavelengths (405 nm, 450 nm and 470 nm) to illuminate an aqueous solution of curcumin, evaluating its degradation for five different exposure times (0, 5, 15, 45 and 105 minutes). The results were compared with equivalent measurements of dark degradation and illumination in the presence of a singlet-oxygen quencher. Three solution concentrations (50, 100 and 150 µg/ml) were studied. To measure the fluorescence, it was used low power 405 nm excitation laser source. Time dependent photodegradation of curcumin was observed, as compared to the natural degradation of samples maintained on a dark environment. Two main absorption peaks were detected and their relation responded to both concentration and wavelength of the illumination source. A spectral correlation between absorption of curcumin and the emission bands of the sources showed an optimal spectral overlap for the 450 nm LED. For this source, photobleaching showed a less intense degradation on the presence of singlet oxygen quencher. This last result confirmed singlet oxygen production in vitro, indicating a strong potential of this composite to be used as a blue-light-activated photosensitizer.

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.