Light Exposure Time Research Articles

Enhanced Singlet Oxygen Generation in Aggregates of Naphthalene-Fused BODIPY and Its Application in Photodynamic Therapy.

Several reports are available on aggregation-induced emission and its applications in biomedical imaging and other material sciences. However, enhancement of singlet oxygen generation in nanoaggregates is rarely reported. Here, we report the synthesis of Naph-BODIPY Br2, which absorbs at 661 nm (monomer) with a high molar absorption coefficient. The presence of bromine promotes intersystem crossing, thereby enhancing the singlet oxygen quantum yield (ΦΔ ∼ 0.50 in methanol). In order to increase hydrophilicity, we developed Naph-BODIPY Br2 nanoaggregates (∼100 nm), which demonstrated aggregation-induced properties and exhibited a bathochromic shift with an absorption maximum at 757 nm. The bathochromic shift in the UV-vis spectra due to aggregation is corroborated by TD-DFT analysis. The computational data also confirm the presence of a low-lying triplet state, which enhances the generation of singlet oxygen, making it effective for photodynamic therapy. These aggregates showed excellent singlet oxygen generation in aqueous media, compared to their monomeric form and standard methylene blue. Their hydrophilic nature and high singlet oxygen generation enabled significant phototoxicity against human carcinoma cells with IC50 values of 4.06 ± 0.01 and 4.09 ± 0.1 μM, respectively, for MCF-7 and A549 cells upon 5 min exposure to light. Moreover, their phototoxicity further increases with an increasing exposure time of light for both cell lines. Notably, Naph-BODIPY Br2 nanoaggregates exhibited nearly zero dark cell toxicity and effectively induced apoptosis in cancer cells upon light activation, highlighting their potential as powerful photosensitizers for photodynamic cancer therapy.

Photodynamic therapy‐induced precise attenuation of light‐targeted semicircular canals for treating intractable vertigo

AbstractVertigo is a common symptom of various diseases that affects a large number of people worldwide. Current leading treatments for intractable peripheral vertigo are to intratympanically inject ototoxic drugs such as gentamicin to attenuate the semicircular canal function but inevitably cause hearing injury. Photodynamic therapy (PDT) is a noninvasive therapeutic approach by precisely targeting the diseased tissue. Here, we developed a PDT‐based method for treating intractable peripheral vertigo in a mouse model using a polymer‐coated photosensitizer chlorin e6 excited by red light. We found that a high dose of PDT attenuated the function of both semicircular canals and otolith organs and damaged their hair cells. Conversely, the PDT exerted no effect on hearing function or cochlear hair‐cell viability. These results suggest the therapeutic potential of PDT for treating intractable peripheral vertigo without hurting hearing. Besides, the attenuation level and affected area can be precisely controlled by adjusting the light exposure time. Furthermore, we demonstrated the potential of this therapeutic approach to be minimally invasive with light irradiation through bone results. Thus, our PDT‐based approach for attenuating the function of the semicircular canals offers a basis for developing a less‐invasive and targeted therapeutic option for treating vertigo.

Antibacterial effect of semiconductor laser radiation against the strains of S. aureus and P. aeruginosa, leading pathogens in osteomyelitis

Introduction The study of the antibacterial effect of photodynamic therapy against the leading pathogens of chronic osteomyelitis is one of the promising directions today.Purpose of the work was to evaluate the antibacterial effect against the strains of Staphylococcus aureus and Pseudomonas aeruginosa with the ALOD-01 laser system in the presence of photodithazine.Materials and methods The object of the study was 24-hour archival cultures of gram-positive and gram-negative microorganisms belonging to two taxa: Staphylococcus aureus (25923), Pseudomonas aeruginosa (27853). The antibacterial effect after the exposure to laser radiation in the presence of photodithazine on the microbial cells of the studied cultures was assessed by the absence of microorganism growth in the area of the light beam.Results Laser exposure in combination with photodithazine (concentration 0.5–1.0 mg/ml) on S. aureus for two minutes at 200–300 J achieved a bactericidal effect in the beam area. A bactericidal effect on the entire surface of the Petri dish was achieved with light exposure of 400 J for 5 minutes and a photodithazine concentration of 1.0 mg/ml. Laser exposure for 2 minutes in the presence of photodithazine at a concentration of 0.5 mg/ml and 1 mg/ml did not have an antibacterial effect on P. aeruginosa strains. Continuous growth of microorganisms was observed on the dish. Increasing the light dose and exposure time contributed to a decrease in the growth of microbial cells. A bactericidal effect was obtained only in the center of the dish in treating the bacterial suspension with photodithazine at a concentration of 5 mg/ml.Discussion The effectiveness of PDT depends on the type of microorganisms, the anatomical location of the infection site, as well as the properties of the photosensitizer and the laser used. Depending on the structure of the cell wall, different susceptibility of bacteria to photodynamic effects is observed.Conclusion S. aureus strains can be successfully photoinactivated using photodithazine. For P. aeruginosa strains, it was not possible to find a regime in which microbial cell growth was absent throughout the dish. The photodynamic reaction occurs only when adequate doses of light energy act on the photosentisizer in the presence of oxygen in the medium, while the photodynamic damage is local and the bactericidal effect is limited by the zone of light exposure.

Digital Light Processing Followed by Pressureless Sintering of Metal-Reinforced Ceramics: Adjustment of Process Parameters and Correlation with Composites Properties

AbstractDigital light processing (DLP) belongs to additive manufacturing techniques and is frequently used in shaping ceramics. The paper concerns the adjustment of the DLP method to metal-reinforced ceramics, especially dispersions containing high concentrations of Al2O3 (45 vol%) and molybdenum or nickel particles (0.5 vol%). Different glycol acrylates, deflocculants (polyelectrolytes and diammonium hydrogen citrate), and photoinitiators (Omnirad group) were examined regarding their influence on the rheological properties of the dispersions and the cure depth under the external halide UV lamp and LED projector built into the 3D printer. In the examined systems, the cationic polyelectrolyte KD1 dissolved in 2-butanone allowed to obtain dispersions of the lowest viscosity. Printing parameters (light exposure time, single layer height) were matched, and the properties of the materials were examined. The Vickers hardness of the sintered bodies equalled 19.4 GPa, 14.5 GPa and 17.3 GPa for Al2O3, Al2O3-Ni and Al2O3-Mo samples, respectively. The microstructure was analyzed using SEM, followed by EDS and XRD. The addition of only 0.5 vol% of Ni has improved the fracture toughness of alumina by up to 36–40% (according to Niihara and Anstis equations). The exemplary objects in the form of cog wheels were printed and densified at 1550 °C in a reductive atmosphere of Ar/H2.

Naphthalene Monoanhydride and Perylene Composites for Efficient Photocatalytic Hydrogen Evolution and Metal-Free Heterogeneous Oxidative Amidation.

This study explores the synthesis of two visible light active organic chromophore-based composites using naphthalene monoanhydride (Np) and 1,7-dibromoperylene monoanhydride diester (PMDE). These chromophores feature favorable optical and electronic properties and polyaromatic skeletons with anhydride functionalities that facilitate π-π interactions between the chromophore and polymeric carbon nitride (CN) or covalent connections of chromophores with NH2 groups of CN. Accordingly, heterogeneous chromophore-CN composite photocatalysts namely, Np/CN(c) and PMDE/CN(c) were prepared by adopting in situ calcination (c) and composites Np/CN(a) and PMDE/CN(a) were prepared by ex situ physical adsorption (a) methods. In situ prepared Np/CN(c) and PMDE/CN(c) composites exhibited H2 evolution rates (HER) of 1069 and 705 μmol h-1 g-1, respectively, which are significantly higher than ex situ Np/CN(a) and PMDE/CN(a) composites with HER of 465 and 252 μmol h-1 g-1, respectively. These rates are 10, 7, 4.8, and 2.5 times higher than the bulk-CN, indicating the potential of these composites for efficient photocatalytic H2 evolution. Surface area normalized HER enhancements were 3.8, 5.3, 6.6, and 4.2 times higher for Np/CN(c), PMDE/CN(c), Np/CN(a), and PMDE/CN(a) respectively compared to bulk-CN. These composite photocatalysts exhibited excellent stabilities under prolonged photoirradiation, with H2 evolution consistently increasing with the light exposure time. Additionally, these metal-free heterogeneous composites demonstrated efficient photocatalytic activities towards oxidative amidation of aromatic aldehydes, with up to 80% product yields, establishing the prospects of combining homogeneous and heterogeneous entities in a metal-free active material in solar energy harvesting.

Enhancing pigment production with cyanobacteria-rich microbiomes: Effect of light quality and exposure time

Cyanobacteria-rich microbiomes may stand as a cost-effective source of pigments, as they exhibit improved stability in comparison to monocultures and do not require sterile media to grow. However, these bioproduct sources have not been thoroughly optimized for pigment production. The aim of the present study was to evaluate the effects of light quality and exposure time on pigment concentration and population distribution in 6 microbiomes rich in Synechococcus sp. and Synechocystis sp. A multivariable experimental design was implemented for selecting the optimal culture conditions in terms of light quality (white, red, green and blue) and exposure time (4 and 6 days). As a result, differential light quality exposures did not favor the growth of one species over another. Green light had a significantly positive effect on phycobiliprotein content in all microbiomes, with up to a 2.3-fold increase as compared to white light. Indeed, 4 days of exposure induced a change in phycobiliprotein composition in 5 microbiomes. Microbiome M11 was the best phycobiliprotein producer (content up to 145.5 mg gDW−1). Meanwhile, carotenoid contents above 1.8 mg gDW−1 were attained in all the microbiomes under optimized conditions. In conclusion, light quality modulation is a promising approach to stimulate the production of pigments in cyanobacteria-rich microbiomes.

Toxicological assessment of reactive blue 19 dye aqueous solutions under UV-LED light

Abstract The dye-contaminated industrial effluent causes serious health issues when it gets mixed with underground water without primary treatment. The current project was designed to treat reactive blue-19 dye aqueous solutions in the presence of hydrogen peroxide (H2O2) and titanium dioxide (TiO2) under UV-LED light. The characterization of the photocatalyst was carried out via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) for structure, purity, and surface study. The effect of various factors such as pH, TiO2 dose, UV-LED light exposure time, H2O2, and dye concentration, on the degradation rate and cytotoxicity reduction was evaluated and optimized through the Response Surface Methodology (RSM). The maximum degradation of dye solution and chemical oxygen demand (COD) reduction was achieved at 98.81 and 86.22 %, respectively for 50 ppm solution, using UV-LED/H2O2(3 %)/TiO2(6 g/L) hybrid process. The toxicity evaluation through the Allium cepa test demonstrated a 62.40, 65.2, and 56.97 % increase in root length (RL), root count (RC), and mitotic index (MI), respectively, following treatment with the UV-LED/H₂O₂/TiO₂ combined process for 150 min. The hemolytic and brine shrimp tests revealed a reduction in toxicity up to 92.18 and 84.08 %, respectively, after applying the same treatment. Additionally, the Ames test indicated up to 80.94 % reduction in mutagenicity for TA98 and an 84.04 % reduction for TA100 strain when dye samples were treated with UV-LED light in the presence of H₂O₂ and TiO₂ for 150 min. The findings suggested that UV-LED light in conjunction with H2O2 and TiO2 can be a useful tool for the degradation and detoxification of toxic pollutants found in textile wastewater.

Effect of Ultraviolet-C Light Exposure Time on the Dimensional Stability of Addition Silicone Dental Impressions: An In Vitro Study.

To compare the effect of different ultraviolet-C (UV-C) light exposure times on the dimensional stability of addition silicone dental impressions. The dimensional stability of the addition silicone dental impressions was assessed by measuring specific dimensions on dental casts that were recovered from an upper acrylic resin model of dental implants. The impressions were reproduced using a customized tray adapted in a three-point simplex dental articulator permitting only opening and closing movements. Addition silicone dental impressions were divided into five groups (N = 12) according to the UV-C light exposure time. Group A was untreated; group B received 10 minutes; group C, 20 minutes; group D, 30 minutes; and group E, 40 minutes. All the impressions were poured with type IV dental stone and the internal edges of the upper silicone retainers of impression copings were used as five reference points (E, D, C, B, and A) to determine six linear measurements between ED, CB, EA, AD, EB, and CD points using a traveling microscope of 0.001 mm accuracy. One-way analysis of variance (ANOVA) was used for the statistical analysis (p < 0.05). Expansion and contraction were noted among ED, CB, EA, and EB measurements, whereas only expansion was noted among AD and CD measurements. The ANOVA analysis showed there was no significant difference in the arithmetic means for the measurements between and within group A and the other groups (p > 0.05). The UV-C light exposure time of 10, 20, 30, and 40 minutes did not have any negative effect on the dimensional stability of the addition silicone dental impressions evaluated. In the daily routine dental practice, dental impressions need to be washed and disinfected immediately after making to prevent cross-infections. The UV-C light has been proposed as a promising method for disinfection, but only a few studies have been published about its effect on the dimensional stability of dental silicones. How to cite this article: Bravo-Cueto AG, Tinedo-López PL, Malpartida-Carrillo V. Effect of Ultraviolet-C Light Exposure Time on the Dimensional Stability of Addition Silicone Dental Impressions: An In Vitro Study. J Contemp Dent Pract 2024;25(6):507-513.

An optimised molecular-based method for ecological study of tardigrades in soils

To improve approaches for studying soil tardigrades, we compared three tardigrade extraction methods, including centrifugal flotation, Baermann funnel, and Whitehead tray, and found that the Whitehead tray method outperformed the two others. We optimised the Whitehead tray extraction condition under various soil pre-treatment processes, sample sizes, light exposure, and extraction time. We found that extending light exposure of non-sieved soils facilitates the extraction of tardigrades. We sequenced the DNA extracted from isolated tardigrade individuals and environmental soil samples, and found that tardigrade DNA extracts yielded a 173-fold increase in the proportion of tardigrade sequences and a 12-fold improvement in the estimation of tardigrade diversity.

Gelatin methacryloyl biomaterials and strategies for trophoblast research

Rising maternal mortality rates in the U.S. are a significant public health issue that must be addressed; however, much of the basic science information required to target pregnancy-related pathologies have not yet been defined. Placental and blastocyst implantation research are challenging to perform in humans because of the early time frame of these processes in pregnancy and limited access to first trimester tissues. As a result, there is a critical need to develop model systems capable of studying these processes in increasing mechanistic detail. With the recent passing of the FDA Modernization Act 2.0 and advances in tissue engineering methods, three-dimensional microphysiological model systems offer an exciting opportunity to model early stages of placentation. Here, we detail the synthesis, characterization, and application of gelatin methacryloyl (GelMA) hydrogel platforms for studying trophoblast behavior in three-dimensional hydrogel systems. Photopolymerization strategies to fabricate GelMA hydrogels render the hydrogels homogeneous in terms of structure and stable under physiological temperatures, allowing for rigorous fabrication of reproducible hydrogel variants. Unlike other natural polymers that have minimal opportunity to tune their properties, GelMA hydrogel properties can be tuned across many axes of variation, including polymer degree of functionalization, gelatin bloom strength, light exposure time and intensity, polymer weight percent, photoinitiator concentration, and physical geometry. In this work, we aim to inspire and instruct the field to utilize GelMA biomaterial strategies for future placental research. With enhanced microphysiological models of pregnancy, we can now generate the basic science information required to address problems in pregnancy.

Towards accurate modelling of rock surface exposure dating using luminescence to estimate post-exposure erosion rate

Depth-dependent luminescence in the top few millimetres of rock surface emerges as a potential tool to estimate rock surface exposure age and post-exposure erosion rate. It relies on the principle that the luminescence depth profile (LDP) propagates deeper with the time of sunlight exposure and moves to shallower depth with the erosion rate. The propagation of LDP is generally assumed to follow the first-order kinetic (FOK) model, except for a few recent studies. The FOK model predicts an exponential decay of infrared stimulated luminescence (IRSL) signal with light exposure time, which rarely corroborates experimental observation; IRSL signal decay is much slower than exponential decay. The faster decay of IRSL, predicted by the FOK model, results in faster propagation of LDP and thus always underestimates the exposure age and translates into a higher erosion rate. Interestingly, the slower-than-exponential decay of the IRSL signal can be better explained by general order kinetics (GOK). Thus, recent studies on rock surface luminescence dating have employed the GOK model. However, the GOK model is yet to be explored to predict post-exposure erosion rates. Here, we apply the GOK model and theoretically demonstrate the impact of the order of kinetics on the calibration and propagation of LDP in the presence of erosion and how the LDP's transient to steady state transition depends on the order of kinetics. We have performed a series of synthetic tests to assess the impact of selecting an incorrect model on the prediction of erosion rate. Finally, using the revised rate equation, the erosion rates are recalculated for natural samples (data available in the literature: Lehmann et al. (2019b)) and the impact of GOK on the predicted erosion rate is discussed.

Research on the mechanism of natural antibacterial properties of Calotropis gigantea fiber

This research explores the antibacterial mechanism of Calotropis gigantea (CG) fiber through systematic antimicrobial testing and microstructural characterizations on different types of dried CG fibers. Different temperatures and light exposure times were employed to prepare a series of fiber samples. Standard antimicrobial tests were conducted, revealing that both light exposure time and drying temperature significantly influenced the fiber's antibacterial properties against Escherichia coli. Prolonged light exposure time and drying temperatures notably suppressed the antibacterial efficacy. Chemical composition, surface morphology, and thermal stability were further investigated using various techniques, including laser microscopy, Raman, FTIR, and X-ray photoelectron spectroscopies, as well as thermogravimetric-differential thermal analysis. The results revealed a minor role of surface profile and lignin in the variation of antibacterial properties of CG fiber, which should mainly be associated with the alteration of flavonoids, despite the presence of distinct mass losses and decomposition temperature shifts after fiber drying. This study not only unveils and confirms the resource and mechanism of the antimicrobial activity of Calotropis gigantea fiber but also provides insights to guide future optimization of processes and control of microstructure. These findings hold promise for the development of Calotropis gigantea fiber applications in antibacterial products.

Ekstraksi berbantu gelombang ultrasonik dan fotodegradasi senyawa antosianin pada tangkai parijoto (Medinilla speciosa Blume)

Parijoto is an endemic plant widely found on the slopes of Mount Muria, Kudus Regency, Central Java. The local community often consumes parijoto fresh fruit and processes parijoto fruit such as syrup, dodol, candy, and tea. So far, the Parijoto stalk, which weighs 18.19% of the total weight of the parijoto stalk and fruit, has not been widely used, but it has great potential as a source of anthocyanin. Anthocyanin compounds have low stability to temperature and light. For this reason, extraction with a relatively low temperature and faster than conventional methods is required, one of which is Ultrasonic-assisted extraction. Ultrasonic waves produce cavitation bubbles, facilitating solvent penetration so that cell bioactive components can be extracted more effectively. This study aimed to determine the effect of ultrasonic wave-assisted extraction time of parijoto stalk anthocyanin and examine the effect of various light exposure intensities and exposure times (photodegradation) on Parijoto stalk anthocyanin extract. Ultrasonic-assisted extraction of parijoto stalk anthocyanins used a completely randomized design (CRD) with extraction time (5, 10, 15, 20, and 25 minutes) and three treatment repetitions. In photodegradation using a factorial complete randomized design with the treatment of light exposure intensity (2037 lux, 4259 lux, 6482 lux, and 9259 lux) and exposure time (6, 12, 18, and 24 hours). The results showed that the longer the extraction, up to 20 minutes, the total anthocyanin levels, redness (a*), and yellowness (b*) increased while lightness (L*) decreased. The higher the light intensity of the fluorescent lamp and the longer the light exposure, the lower the total anthocyanin content with a lower half-life. Ultrasonic-assisted extraction have proven to be quite effective for the anthocyanin extraction but need to attention with time and light exposure intensity.

Clinical trial of two-step photodynamic therapy for reduced pain in the treatment of precancerous squamous lesions (Actinic keratoses)

BackgroundPain associated with aminolevulinic acid photodynamic therapy (ALA-PDT) for the treatment of facial dermatoses results in low patient compliance. Two-step photodynamic therapy (two-step PDT) may improve comfort by optimizing light amplitude and exposure time. ObjectiveTo investigate the efficacy of two-step PDT in reducing the pain generated during the treatment of facial skin disorders. MethodsTwenty-six patients with AK were randomly divided into two groups; the experimental group was treated with two-step photodynamic therapy and the control group was treated with conventional photodynamic therapy. The pain intensity of the patients at different times was assessed using the pain numerical rating scale (NRS). ResultsA total of 26 patients completed three ALA-PDT treatments, 13 and 13 patients in each group, respectively. The mean NRS scores of patients in the experimental group (3.28±1.41, 3.33±1.43, 3.42±1.78) were lower than those of the control group (5.00±1.94, 5.09±1.86, 4.86±1.64) on each occasion. The incidence of certain adverse reactions was lower in the experimental group than in the control group. There was no difference between the two groups in terms of clinical outcome, recurrence rate and patient satisfaction. ConclusionTwo-step photodynamic therapy can reduce pain and the incidence of some adverse reactions, but does not affect clinical efficacy, recurrence rate and patient satisfaction.

Exploring the Evolution of Sleep Patterns From Infancy to Adolescence.

Sleep is a critical component of healthy development, particularly during the formative years from infancy through adolescence. Sleep undergoes continuous change throughout life characterized by frequent awakenings and a high proportion of rapid eye movement (REM) sleep during infancy, changes in sleep architecture, an increase in non-rapid eye movement (NREM) sleep during adolescence, and an eventual decrease in REM sleep in old age. Adequate sleep is therefore essential for cognitive development, especially between ages 10 and 16. Sleep deprivation may negatively affect academic performance, attention regulation, and emotional well-being. Biological factors, such as hormonal changes during puberty, significantly influence sleep patterns, leading to later bedtimes and a tendency for chronic sleep deprivation in adolescents. Environmental factors, including light exposure and screen time, also play a critical role in regulating sleep. This paper examines the evolution of sleep patterns across infancy and adolescence, describing changes in sleep architecture, timing, and regulation. The influence of biological, environmental, and socio-cultural factors on sleep is explored, highlighting how these factors collectively shape sleep behaviors and health outcomes. It also addresses the profound role sleep plays in cognitive development, brain maturation, and emotional well-being. The importance of understanding sleep patterns and their developmental trajectories to address sleep-related issues is emphasized. Promoting healthy sleep from an early age can enhance cognitive and emotional outcomes, contributing to better academic performance and overall well-being in children and adolescents. The findings advocate for further standardized sleep intervention programs globally to prioritize sleep health and support optimal development.

Photon-assisted electron depopulation of 4H-SiC/SiO2 interface states in n-channel 4H-SiC metal–oxide–semiconductor field effect transistors

4H-SiC/SiO2 interface states play a major role in the performance and reliability of modern 4H-SiC metal–oxide–semiconductor field effect transistors (MOSFETs). To gain new insights into these interface states, we developed a cryogenic measurement technique that uses photon-assisted electron depopulation to probe device performance limiting 4H-SiC/SiO2 interface states. This technique enables the characterization of shallow as well as deep states at the 4H-SiC/SiO2 interface of fully processed devices using a cryogenic probe station. Our method is performed on n-channel 4H-SiC MOSFET test structures with deposited oxide and postoxidation anneal. We identify conditions under which the electrons remain trapped at 4H-SiC/SiO2 interface states and trigger the controlled photon-assisted electron depopulation within a range of photon energies. This allows us to prove the presence of near interface traps, which have previously been found in thermally grown 4H-SiC MOS structures. Our results are supported by device simulations. Additionally, we study the impact of irradiation intensity and light exposure time on the photon-induced processes.

Light Exposure in Young University Students: Effect on Ocular Surface Health

Purpose: The ocular surface is the first structure to absorb light and transfer it to retina to form images. However, the effect of different wavelengths and light exposure timing could harm the eye. The current study aims to measure light exposure and its correlation to the ocular surface. Study Design: Cross sectional observational. Place and Duration of Study: Qassim University, from March to September 2023. Methods: Light sensor buttons (RGB) were used in the current study (LYS technologies); 53 subjects were asked to wear them on the collar for one week, followed by a visit to the optometry clinic for an eye examination by bio-microscopy and Schirmer I test. Consequently, readings from Kerato-graph 5M were obtained. Lastly, participants were asked to fill out a validated Arabic OSDI questionnaire. Results: Results of the dry eye symptoms scale revealed that 24.5% had mild symptoms, and 20.8% of participants reported severe dry eye symptoms. A negative correlation between the Schirmer test and OSDI scores was found. Blue light exposure at night was negatively correlated to tear meniscus height (P &lt;0.05). Moreover, tear meniscus height was lower in participants with higher exposure to the red component of light during the day and higher melanotic lux in the daytime (P&lt;0.05). Tear breakup time was lower in patients exposed to higher melanopic lux during nighttime (p&lt;0.05). Conclusion: Light exposure habits are associated with some dry eye parameters. Moreover, light at night, especially melanopic lux wave-length is a risk factor for developing dry eye disease.

Fine-tuning of membrane permeability by reversible photoisomerization of aryl-azo derivatives of thymol embedded in lipid nanoparticles

Responsiveness of liposomes to external stimuli, such as light, should allow a precise spatial and temporal control of release of therapeutic agents or ion transmembrane transport. Here, some aryl-azo derivatives of thymol are synthesized and embedded into liposomes from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine to obtain light-sensitive membranes whose photo-responsiveness, release behaviour, and permeability towards Cl- ions are investigated. The hybrid systems are in-depth characterized by dynamic light scattering, atomic force microscopy and Raman spectroscopy. In liposomal bilayer the selected guests undergo reversible photoinduced isomerization upon irradiation with UV and visible light, alternately. Non-irradiated hybrid liposomes retain entrapped 5(6)-carboxyfluorescein (CF), slowing its spontaneous leakage, whereas UV-irradiation promotes CF release, due to guest trans-to-cis isomerization. Photoisomerization also influences membrane permeability towards Cl- ions. Data processing, according to first-order kinetics, demonstrates that Cl- transmembrane transport is enhanced by switching the guest from trans to cis but restored by back-switching the guest from cis to trans upon illumination with blue light. Finally, the passage of Cl- ions across the bilayer can be fine-tuned by irradiation with light of longer λ and different light-exposure times. Fine-tuning the photo-induced structural response of the liposomal membrane upon isomerization is a promising step towards effective photo-dynamic therapy.

Extraction and characterization of carotenoid pigments with antioxidant and antibacterial potential from marine yeast Rhodotorula sp. KSB1.

Pigments are coloring agents used widely in different industrial sectors. There is a demand for using natural pigments rather than synthetic dyes because of the health hazards caused by synthetic dyes. Many natural pigments have different medicinal activities which can contribute to the nutritional value of the product. This study was carried forward with marine yeasts which can produce pigments. A total of 4 marine yeast isolates were recovered from the mangrove area of Sundarbans, West Bengal, India. Among them, the isolate KSB1 produced 856µg/g total concentration of carotenoid pigment and the dry mass weight was 3.56g/L. The stability of the extracted pigments was checked using temperature, pH, UV light exposure time, and different saline conditions. The pigments were characterized using HPLC and FTIR analysis. All of the extracted pigments showed good antioxidant activity in DPPH, metal chelating, and reducing power assay. The pigments were also found to have good antibacterial activity against the bacterial pathogens Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli. Carotenoid pigment from KSB1 was found to have maximum activity in all the pathogens. The cytogenotoxicity using onion roots and phytotoxicity analysis indicated that the pigments were non-toxic and safe for cells. Finally, the potential marine yeast was identified using 18s rRNA sequencing and identified as Rhodotorula sp. KSB1 (Accession no. MH782232).

Evaluation of quantification methods to determine photodynamic action on mono- and dual-species bacterial biofilms.

The effect of photodynamic inactivation (PDI) sensitized by 5,10,15,20-tetra(4-N,N,N-trimethylammoniophenyl)porphyrin (TMAP4+) on different components of mono- and dual-species biofilms of Staphylococcus aureus and Escherichia coli was determined by different methods. First, the plate count technique showed that TMAP4+-PDI was more effective on S. aureus than E. coli biofilm. However, crystal violet staining revealed no significant differences between before and after PDI biofilms of both bacteria. On the other hand, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method indicated a reduction in viable cells as the light exposure time increases in both, mono- and dual-species biofilms. Furthermore, it was determined that as the irradiation time increases, the amount of extracellular polymeric substances present in the biofilms decreased. This effect was presented in both strains and in the mixed biofilm, being more evident in S. aureus mono-specie biofilm. Finally, scanning electron microscopy analysis showed a decrease in the number of cells forming the biofilm after photosensitization treatments. This information makes it possible to determine whether the photodynamic action is based on damage to metabolic activity, extracellular matrix and/or biomass, which may be useful in establishing a fully effective PDI protocol for the treatment of microorganisms growing as biofilms.