Optical Density Measurements Research Articles

Measurement of optical density in a narrow wavelength band: a method for correcting the results of indirect measurements

The issues of correspondence of the results of direct and indirect measurements of optical density in a narrow wavelength band are considered. The optical density in a narrow wavelength band was measured by filtering the luminous flux according to the international standard ISO 5-3:2009 “Photography and graphic technology – Density measurements. Part 3: Spectral conditions” (direct measurement) and spectral method (indirect measurement). In order to ensure the uniformity of optical density measurements in a narrow wavelength band and establish the traceability of measurement results to the State Primary Standard of optical density units GET 206-2016, the degree of conformity of the results obtained by two methods was investigated. The techniques of measuring optical density in a narrow wavelength band for each method are described. The method of fi ltering the luminous flux was implemented using GET 206-2016, namely using a complex for measuring diffuse optical transmittance density. The Cary 7000 spectrophotometer (Agilent, USA) was used to implement the spectral method. Data on measuring the optical density of glass light fi lters by two methods are presented. A method for correcting the results of spectral measurements has been developed and a correction to the results of spectral measurements has been determined. The developed method and the correction make it possible to establish the correspondence of the results of spectral measurements to the results of measurements by fi ltering the luminous fl ux. Also, the described method for correcting the results of spectral measurements makes it possible to establish the traceability of the results of optical density measurements by the spectral method to the measurement results using GET 206-2016.

Developing a novel radiosensitive metal ion-loaded PVA/NBT film as medical low-dose X-ray dosimeter

The hazards associated with ionizing radiation exposure has spurred the advancement of reliable and precise dosimetry techniques. Currently, there still lacks a viable and efficient dosimetry methods for measuring radiation expo-sure within low dosage ranges. This raises a concern in certain domains, such as radiodiagnostics and practitioners that employ low-dose X-ray radiation. Hence, this study aims to produce PVA/NBT film dosimeters that are capable in effectively detecting low dosages of X-ray radiation. Moreover, PVA/NBT films loaded by various metal ions will also be studied. The films were synthesized by the solvent casting method. The films were subjected to X-ray irradiation with a dosage ranging from 0 to 2.626 mGy. The films were further examined through EDX analysis, UV–Vis spectroscopy, optical density measurement, FTIR spectroscopy, and SEM analysis. It was observed that X-ray radiation exposure caused a broadening in the UV–Vis absorbance spectrum, which enhances its light absorption capability and making it more opaque. Furthermore, the careful selection of metal ion enhanced the film's ability in detecting X-ray radiation. Silver-loaded films were proven to significantly enhance the linearity and sensitivity of the PVA/NBT dosimeter film. These findings showed that silver-loaded PVA/NBT films exhibit a promising prospect for further applications in the domain of medical radiation.

Exploring the interactions of JAK inhibitor and S1P receptor modulator drugs with the human gut microbiome: Implications for colonic drug delivery and inflammatory bowel disease

The gut microbiota is a complex ecosystem, home to hundreds of bacterial species and a vast repository of enzymes capable of metabolising a wide range of pharmaceuticals. Several drugs have been shown to affect negatively the composition and function of the gut microbial ecosystem. Janus Kinase (JAK) inhibitors and Sphingosine-1-phosphate (S1P) receptor modulators are drugs recently approved for inflammatory bowel disease through an immediate release formulation and would potentially benefit from colonic targeted delivery to enhance the local drug concentration at the diseased site. However, their impact on the human gut microbiota and susceptibility to bacterial metabolism remain unexplored. With the use of calorimetric, optical density measurements, and metagenomics next-generation sequencing, we show that JAK inhibitors (tofacitinib citrate, baricitinib, filgotinib) have a minor impact on the composition of the human gut microbiota, while ozanimod exerts a significant antimicrobial effect, leading to a prevalence of the Enterococcus genus and a markedly different metabolic landscape when compared to the untreated microbiota. Moreover, ozanimod, unlike the JAK inhibitors, is the only drug subject to enzymatic degradation by the human gut microbiota sourced from six healthy donors. Overall, given the crucial role of the gut microbiome in health, screening assays to investigate the interaction of drugs with the microbiota should be encouraged for the pharmaceutical industry as a standard in the drug discovery and development process.

Silicon-infused bacterial cellulose: in situ bioprocessing for tailored strength and surface characteristics

In this study we investigate the use of in situ bioprocessing for the production and surface modification of bacterial cellulose (BC) with silicon additives. The surface properties and tensile strength of the BC were studied and compared with plain BC. The effect the modification exhibited on the survivability of the bacteria was assessed by optical density measurements and found that the addition of the modification marginally slowed growth in the case of Tetramethyl orthosilicate (TMOS) and did not affect the growth in the case of Tetraethyl orthosilicate (TEOS). Characterisation of the modified BC was carried out using FTIR, EDX and confirmed the presence of silicon in the material. The width of fibres in the microstructure of BC was measured using SEM. Two different silicon modifications were used to modify the BC, it was shown that the TMOS modification decreased the tensile strength but that the TEOS increased the tensile strength of the BC fibres compared to plain BC. In addition, we found that the washing conditions of 1% NaOH (w/v), industrial methylated spirit (IMS), and deionised water (DI) showed some impact on the properties of the samples, particularly the IMS produced a reduced contact angle in the modified samples. However, the contact angle increased in the case of TEOS modification with the NaOH wash. In conclusion this study shows a novel method of modifying BC materials in-situ using silicon additives for increased tensile strength and the potential for tuneable hydro interactions.

Schizosaccharomyces pombe as a predictor toxicity tool

The fission yeast Schizosaccharomyces pombe is frequently used as a genetically manipulable model system, offering valuable understandings into cellular mechanisms. In the present study, a comprehensive step-by-step methodology for the research of the action mechanisms and detoxification by efflux pumps is showed. The protocol involves the thawing and culture of yeast cells in liquid medium under controlled conditions to ensure exponential growth. After that, a dose-response assessment is carried out by culturing wild-type cells in liquid medium, followed by exposure to increasing concentrations of the toxic substances. Optical density measurements are taken spectrophotometrically after exposure, and the process is repeated at least three times for quantitative analysis. Subsequently, defective mutants are selected to explore specific mechanisms of action or detoxification by efflux pumps, with cultures prepared and treated similarly to the wild type. Optical density measurements are again taken after exposure for quantitative analysis. This methodology ensures robust and reproducible results for the research toxic substances effects on S. pombe.-Schizosaccharomyces pombe is an adequate tool to evaluate contaminants toxicity.-Dose-responses curves are obtained on wild type to evaluate toxicity mechanisms.-This methodology ensures robust and reproducible results for the research toxic substances effects on S. pombe.

Omics-based analysis of Akkermansia muciniphila cultivation in food-grade media.

Background and Aim: Over the past years, the gut microbiota and its correlation to health and disease has been studied extensively. In terms of beneficial microbes, an increased interest in Akkermansia muciniphila (A. muciniphila) has been observed since its discovery. Direct evidence for the role of A. muciniphila in host health has been provided in both mice and human studies. However, for human interventions with A. muciniphila cells, industrial-scale fermentations are needed, and hence, the used cultivation media should be free of animal-derived components, food-grade, non-allergenic and allow for efficient growth to high densities to provide cost-effective production platforms. In this study, we assessed the growth and performance of A. muciniphila in batch bioreactors using newly developed plant-based media. Methods: The bioreactors were supplemented with varying carbon sources, including different ratios of N-acetylglucosamine (GlcNAc) and glucose. We monitored the growth of A. muciniphila in the plant-based medium using optical density (OD600) measurements and microscopy. In addition, we used a combination of biochemical analysis as well as transcriptional and proteomics analysis to gain detailed insight into the physiology. Results: Comparisons between growth on these media and that on mucin revealed differences at both transcriptome and proteome levels, including differences in the expression of glycosyltransferases, signaling proteins, and stress response. Furthermore, elongated cells and higher OD600 values were observed using the plant-based media as compared to cultivation media containing mucin. Conclusion: These differences do not hamper growth, and therefore, our data suggest that the food-grade medium composition described here could be used to produce A. muciniphila with high yields for therapeutic purposes.

National standards of optical density units: principles of optical scheme design, constructive and metrological characteristics

The current state of metrological support for precision optical density measurements is described. In order to analyze the principles of building optical schemes, structural, constructive and functional features of the blocks included in the standards, and metrological characteristics of national standards of optical density units, high-precision optical density measuring instruments developed by national metrological institutes of Russia, Germany, China, and the USA are considered. The equations of optical density measurements are presented, which are a mathematical model of the process of measuring the optical transmittance density of materials. The principles of operation of optical transmittance density unit standards based on light fl fi ration are described. The data of studies of geometric and spectral characteristics of fi national standards of optical density units of four countries are presented, as well as optical schemes and characteristics of standards in the following areas are analyzed: compliance with international standards; features of optical schemes; methods of fi the luminous fl and creating scattered radiation; features of object positioning; type of radiation receiver; metrological characteristics. Information is provided on the participation of national standards in international comparisons. The metrological characteristics of these national standards are summarized in a table. Taking into account and using the considered features of optical schemes, design solutions in conjunction with the metrological characteristics of the described devices contributes to an increase in the level of development while improving the State primary standard of the unit of optical density GET 206-2016.

Induction into viable but non culturable state and outgrowth heterogeneity of Listeria monocytogenes is affected by stress history and type of growth

Exposure to sublethal stresses related to food-processing may induce a heterogenous mixture of cells that co-exist, comprising healthy, sublethally injured, dormant and dead cells. Heterogeneity in survival capacity and dormancy of single cells may impede the detection of foodborne pathogens. In this study, we exposed Listeria monocytogenes Scott A strain, to peracetic acid (PAA; 20–40 ppm) and to acidic conditions (hydrochloric (HCl) and acetic (AA) acid, adjusted to pH 2.7–3.0, to evaluate the resuscitation capacity and outgrowth kinetics of metabolically active cells in two different media. Injury and the viable-but-non-culturable (VBNC) status of cells were assessed by flow cytometry using CFDA (metabolically active) and PI (dead) staining. Stressed CFDA+PI− cells were sorted on Tryptic Soy (TS) Agar or in TS broth, both supplemented with 0.6 % Yeast Extract (TSAYE or TSBYE), to evaluate culturability. Resuscitation capacity of CFDA+PI−sorted cells (10 events/well) was monitored by visual inspection on TSAYE and by optical density measurement in TSBYE for 5 days. Sorting of L. monocytogenes viable cells (CFDA+PI−) in Ringer's solution on TSAYE and TSBYE showed 100 % recovery in both media (control condition), while the mean lag time in TSBYE was 9.6 h. Treatment with 20 ppm PAA for 90 and 180 min resulted in 74.79 % and 85.82 % of non-culturable cells in TSBYE and increased the average lag time to 41.7 h and 43.8 h, respectively, compared to the control (9.6 h). The longest average lag time (79.5 h) was detected after treatment with 30 ppm PAA for 90 min, while at the same condition sorting of CFDA+PI− cells resulted in 95.05 % and 93.94 % non-culturable cells on TSAYE and TSBYE, respectively. The highest percentage of wells with non-culturable cells (96.17 %) was detected on TSAYE after treatment with 40 ppm PAA for 30 min. Fractions of VBNC cells were detected in TSBYE after treatment with HCl pH 3.0 for 60 and 240 min, and in TSAYE and TSBYE after exposure to AA pH 2.7. Treatment with AA pH 2.7 for 150–300 min increased the range of recorded lag time values compared to 60 min, from 8.6 h up to 13.3 h, as well as the mean lag times in TSBYE. Modelling of the outgrowth kinetics comparing the two types of stress (oxidative vs acid) and the two systems of growth (colonial vs planktonic) revealed that low starting concentrations hindered the detection of viable L. monocytogenes cells, either due to VBNC induction or cell heterogeneity.

Straightforward microwave-assisted synthesis of ultrasmall gold nanoparticles acnhored on reduced graphene oxide for enhanced antibacterial application

Graphene derivative materials, such as graphene oxide (GO) and reduced graphene oxide (rGO), have garnered significant attention from scientists for over two decades due to their distinctive characteristics and versatile applications across various fields, particularly in biomedical applications. Incorporating gold nanoparticles (AuNPs) into rGO sheets as rGO-Au nanocomposites further enhances its performance in biomedical applications. This study presents a rapid and efficient method for synthesizing ultrasmall AuNPs anchored on reduced graphene oxide (rGO-Au) using microwave irradiation and ascorbic acid. The optimum microwave treatment was 4 min, ensuring the highest GO reduction degree. Structural characterization by TEM reveals a distinctive architecture with ultrasmall AuNPs (average size of 2.2 nm) distributed on the rGO sheets. Interestingly, while the synthesized rGO-Au did not exhibit any antibacterial activities against both Escherichia coli and Staphylococcus aureus in disk diffusion assays, it demonstrated bacteriostatic effect at remarkably low concentrations when assessed by optical density measurement. The effective concentration of rGO-Au to inhibit E. coli growth was determined to be 2.5 ppm, while for S. aureus, it was 5 ppm, resulting in growth inhibition of 53.1% and 50.0%, respectively. These findings provide a straightforward synthesis route for rGO-Au nanocomposites and underscore the importance of AuNPs’ size and quantity in modulating antibacterial properties.

Novel technique for the ultra-sensitive detection of hazardous contaminants using an innovative sensor integrated with a bioreactor

This study introduces an evaluation methodology tailored for bioreactors, with the aim of assessing the stress experienced by algae due to harmful contaminants released from antifouling (AF) paints. We present an online monitoring system equipped with an ultra-sensitive sensor that conducts non-invasive measurements of algal culture's optical density and physiological stage through chlorophyll fluorescence signals. By coupling the ultra-sensitive sensor with flash-induced chlorophyll fluorescence, we examined the dynamic fluorescence changes in the green microalga Chlamydomonas reinhardtii when exposed to biocides. Over a 24-h observation period, increasing concentrations of biocides led to a decrease in photosynthetic activity. Notably, a substantial reduction in the maximum quantum yield of primary photochemistry (FV/FM) was observed within the first hour of exposure. Subsequently, we detected a partial recovery in FV/FM; however, this recovery remained 50% lower than that of the controls. Integrating the advanced submersible sensor with fluorescence decay kinetics offered a comprehensive perspective on the dynamic alterations in algal cells under the exposure to biocides released from antifouling coatings. The analysis of fluorescence relaxation kinetics revealed a significant shortening of the fast and middle phases, along with an increase in the duration of the slow phase, for the coating with the highest levels of biocides. Combining automated culturing and measuring methods, this approach has demonstrated its effectiveness as an ultrasensitive and non-invasive tool for monitoring the physiology of photosynthetic cultures. This is particularly valuable in the context of studying microalgae and their early responses to various environmental conditions, as well as the potential to develop an AF system with minimal harm to the environment.

Exploring Potential Applications of α and β Polymorphs of Bi2O3 Nanoparticles

AbstractIn this investigation, we successfully synthesized bismuth oxide (Bi2O3) nanoparticles (NPs) via simple combustion method using Artocarpous heterophyllus (Jackfruit) extract as fuel. Both α and β polymorphs of bismuth oxide NPs was prepared using same Artocarpous heterophyllus fuel but there is a variation in the addition of fuel in the range of 1 mL–6 mL. The prepared NPs were characterized by utilizing spectroscopic techniques. The photocatalytic efficiencies were found to be 84 %, 93 % for both α, β forms respectively. Methylene blue dye exhibits effective degradation for β‐phase compared to α‐phase. Furthermore, Electrochemical impedance spectroscopy and sensing (CV) activities were performed. The bismuth oxide modified electrodes exhibits better sensing activity towards dopamine, ascorbic acid, lead nitrate, and results obtained from EIS data revealed the super capacitor characteristics of Bi2O3 nanoparticles. This extensive investigation assessed the effectiveness of Aspergillus Niger‐fighting drugs, as well as the antibacterial effects of synthesized nanoparticles on Staphylococcus Aureus and Escherichia Coli. Measurements of optical density were used to establish the MIC values for antifungals. The protein 4XUY has a strong binding affinity of −6.4 Kcal/mol, with four important hydrogen bond interactions (LYS51, HIS84, ASN131, and GLU238) revealed by molecular docking research. These results expand our knowledge of the therapeutic uses of bismuth oxide nanoparticles by highlighting their potential as effective antibacterial agents and by providing insightful information about how they work against pathogenic microorganisms.

Enhancing Antimicrobial Performance of Gauze via Modification by Ag-Loaded Polydopamine Submicron Particles.

Silver nanoparticles (AgNPs) are known for their antibacterial properties and their ability to promote wound healing. By incorporating silver nanoparticles into medical gauze, the resulting composite material shows promise as an advanced wound dressing. However, clinical applications are hindered by challenges related to the stability of silver nanoparticle loading on the gauze as nanoparticle leaching can compromise antibacterial efficacy. In this study, silver nanoparticles were immobilized onto polydopamine (PDA) submicron particles, which were then used to modify medical gauze. Energy dispersive spectroscopy (EDS) was employed to analyze the elemental distribution on the modified gauze, confirming successful surface modification. The antibacterial properties of the modified gauze were assessed using a laser scanning confocal microscope (CLSM). The results demonstrated a significant reduction in the adhesion rates of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by 99.1% and 63%, respectively, on the PDA-Ag-modified gauze. Optical density (OD) measurements at 590 nm indicated that the modified gauze effectively inhibited biofilm formation, underscoring its potent antimicrobial capabilities. Further antibacterial efficacy was evaluated by diluting and plating co-cultured bacterial solutions with the modified dressing, followed by 24 h incubation and colony counting. The gauze exhibited an antibacterial efficiency of 99.99% against E. coli and 99.8% against S. aureus. Additionally, cell compatibility tests, involving the co-culture of PDA-Ag composites with human cells, demonstrated excellent biocompatibility. These findings suggest that PDA-Ag-modified medical gauze holds significant potential for the treatment of infected wounds, offering a promising solution to improve wound care through enhanced antimicrobial activity and biocompatibility.

Carrier Based Liquid Bioformulation of Salt-Tolerant Pgpr Bacillus Species for Prolonged Survivability

Salinity has emerged as one of the agricultural plants' most severe environmental stresses. Recently, a plant growth-promoting rhizobacteria (PGPR) is being touted as a means of solving yield and environmental issues worldwide. However, multi-strain salt-tolerant rhizobacteria have a short shelf life due to their structural and cellular components, therefore, they need to be supplemented with a liquid carrier material to serve as a shelter and energy source for the bacteria for longer survival. The present study has been undertaken to develop a liquid biofertilizer formulation from multi-strain salt-tolerant PGPR – UPMR, UPMRE6, and a mixed strain of UPMRB9 and UPMRE6 using an optimum amount of cell protectants, namely glycerol (5 mM), trehalose (10 mM), and polyvinyl pyrrolidone (PVP) at 1%. The shelf-life was assessed through measurements of optical density and bacterial biomass to determine the bacterial population and growth trend at monthly intervals. After three months of incubation, the optical density was the highest in the mixed strain treatment supplemented with trehalose with 1.3% and 2.2% increase relative to the UPMRE6 and UPMRB9, respectively, using the same cell protectants. Similarly, bacterial biomass production was the highest in the mixed strains treatment amended with trehalose (0.025 g/mL), with 13.64% and 38.89% increment followed by UPMRE6 and UPMRB9, respectively. Irrespective of the type of protectants used and PGPR type, the optical density and bacterial biomass generally decreased long incubation period. The results demonstrated that the use of 10 mM trehalose has the potential to extend the bacterial shelf life with the slightest cell loss.

Screening of phosphate solubilizing Aspergillus spp. from soil samples

Phosphorus (P) is a naturally existing element crucial for plant growth among the 17 essential elements. It's integral to various biomolecules like nucleic acids, coenzymes, phosphoproteins, and phospholipids, playing key roles in cellular processes and structural integrity. Its presence is fundamental for sustaining healthy plant growth and ecosystem balance. Rhizosphere soil samples from medicinal plants at Shree Shivaji College Akola were collected aseptically. Phosphate Solubilizing Fungi (PSF) were isolated using Pikovskya’s agar medium, characterized microscopically, and screened for phosphate solubilization potentials. % Solubilization Efficiency was determined, and quantitative estimation of phosphate solubilization was conducted by ammonium molybdate method by using KH2PO4 as standard for determination. Fourteen Aspergillus spp. isolates from soil were screened for phosphate solubilization on PVK medium. Results showed varied solubilization indices and efficiencies across different time intervals, with pH changes observed during solubilization. Optical density measurements provided insights into concentration variations among isolates.

Effect of <i>Meloidogyne incognita</i> infection on the accumulation of phenolic compounds in plants of the genus Mint (Mentha L.)

The purpose of the research is to compare the accumulation of phenolic compounds of different species and varieties of mint, zoned in Central Russia against the background of plant infection by Meloidogyne incognita.Materials and methods. Plants were grown from cuttings in a growing experiment in open ground. Mentha × piperita L. (varieties: Tik-Tak, Orange, Minneola, Mojito, Mitchum, Chocolate), M. spicata L. (varieties Morocco, Crispa) and M. longifolia L. (Longifolia) were taken for the study. A month later, the rooted plants were infected at the rate of 1000 sp. infective larvae of M. incognita per plant. After 8 weeks leaves were fixed in ethanol. The total content of phenolic compounds (PC), phenylpropanoids, flavonoids and catechins was studied using a spectrophotometer. The determination of the total content of PС was carried out using the Folin-Cecolte reagent with measurement at 725 nm, phenylpropanoids – by direct measurement of optical density at 330 nm, flavonoids – by reaction with aluminum chloride at 415 nm, the total content of flavans (catechins - flavan-3-ols), their oligomeric forms – proanthocyanidins, as well as leukoanthocyanidins were assessed by reaction with vanillin at 500 nm.Results and discussion. It has been shown that the accumulation of phenols is related to the species of plants. The varieties Mentha × piperita L. in most cases contained more phenols than M. spicata L. and M. longifolia L. A significant number of PC was noted in the violet-colored varieties Mitchum, Chocolate and Orange. The total content of PC almost completely correlates with the content of their precursors – phenylpropanoids. In terms of the content of flavonoids, the Mitchum variety stands out noticeably, and in terms of the content of catechins, the Orange variety stands out. Nematode infection in most varieties causes a noticeable increase in the total accumulation of soluble PC, phenylpropanoids and flavans, but leads to a decrease in the content of flavonoids.

Estimation of differential pathlength factor from NIRS measurement in skeletal muscle

The utilization of continuous wave (CW) near-infrared spectroscopy (NIRS) device to measure non-invasively muscle oxygenation in healthy and disease states is limited by the uncertainties related to the differential path length factor (DPF). DPF value is required to quantify oxygenated and deoxygenated heme groups’ concentration changes from measurement of optical densities by NIRS. An integrated approach that combines animal and computational models of oxygen transport and utilization was used to estimate the DPF value in situ. The canine model of muscle oxidative metabolism allowed measurement of both venous oxygen content and tissue oxygenation by CW NIRS under different oxygen delivery conditions. The experimental data obtained from the animal model were integrated in a computational model of O2 transport and utilization and combined with Beer-Lambert law to estimate DPF value in contracting skeletal muscle. A 2.1 value was found for DPF by fitting the mathematical model to the experimental data obtained in contracting muscle (T3) (Med.Sci.Sports.Exerc.48(10):2013–2020,2016). With the estimated value of DPF, model simulations well predicted the optical density measured by NIRS on the same animal model but with different blood flow, arterial oxygen contents and contraction rate (J.Appl.Physiol.108:1169–1176, 2010 and 112:9–19,2013) and demonstrated the robustness of the approach proposed in estimating DPF value. The approach used can overcome the semi-quantitative nature of the NIRS and estimate non-invasively DPF to obtain an accurate concentration change of oxygenated and deoxygenated hemo groups by CW NIRS measurements in contracting skeletal muscle under different oxygen delivery and contraction rate.

Design strategies based on UV-C LED characterization to enhance Escherichia coli inactivation

This research is focused on the development of a UV-C LED lamp designed for effective water disinfection, tackling as a primary issue the low quantum efficiency and significant self-heating due to elevated operating currents which reduce the LED performance. By conducting thorough characterization and employing strategies including aluminum heat sinks and varied electrical biasing methods such as constant current, PWM, and high-current short-time pulses. The study assesses the disinfection potential against pathogenic bacteria such as Escherichia coli and Salmonella. Results indicate successful E. coli inactivation within agar mediums and notable growth suppression in Mueller-Hinton culture mediums, as confirmed through optical density measurements. Therefore, this investigation underlines the importance of optimized operational strategies to enhance UV-C LED lamps' disinfection capabilities.

Effects of copper and bismuth dopants on PVA/NBT film as an X-ray dosimeter

Low-dose X-rays in the order of milligrays (mGy) are employed in diagnostic radiology. This poses a challenge, considering commercially used dosimeters have limitations in detecting low-dose X-rays. Accordingly, the goal of this research was to fabricate a nitro blue tetrazolium-doped polyvinyl alcohol (PVA/NBT) film dosimeter that could respond to low-dose X-rays while also investigating the effects of introducing copper(II) and bismuth(III) ions on the film's detecting ability. The films were synthesized by the solvent casting method and then exposed to X-ray radiation at doses in the range of 0–2.626 mGy. Optical density and UV–Vis transmittance measurements were carried out to identify changes in the film's optical characteristics brought on by X-ray radiation. In addition, changes in the film's surface morphology and chemical structure were examined by scanning electron microscopy (SEM) and FTIR spectroscopy. According to the results of the optical density measurement, introducing copper(II) ions to the film increased its sensitivity and response linearity. In contrast, the opposite was shown in the case of bismuth(III)-doped films. According to FTIR analysis, film X-ray irradiation caused the PVA to degrade. The development of grain structures on the film surface might be related to the reduction of the copper(II) and bismuth(III) ions. This study discovered that copper(II) ion-doped PVA/NBT film has promising low-dose X-ray detection properties.

Visual pigment concentration and photoreceptor outer segment length in the human retina.

The Beer-Lambert law suggests that visual pigment optical density (OD) should be linearly related to the length of photoreceptor outer segments (POSs). Mammalian studies indicate that visual pigment concentration increases with POS length, but the nature of this relationship may vary due to factors such as visual pigment packing density or retinal eccentricity, and may not necessarily be linearly related. The purpose of this study was to establish the relationship between OD and POS length in humans. Spectral domain optical coherence tomography (OCT) was used to image POS, and imaging retinal densitometry (IRD) was used to measure OD at corresponding locations in 19 healthy participants (age range 25-82 years). POS length and OD measurements were extracted from OCT and IRD images at 23 discrete locations spanning the central 9° of the retina. The averaged data from all participants were fitted with models based on the Beer-Lambert law to establish the relationship between OD and POS length. Visual pigment OD increased monotonically with POS length, but the relationship was non-linear, and a straight-line fit, based on a simple interpretation of the Beer-Lambert law, provided a poor description. A model allowing for different rod and cone visual pigment concentrations provided a superior fit. Specifically, the data were well described by a model where the molar concentration of visual pigment in cones and rods were 3.8 × 10-3 mol/L and 1.8 × 10-3mol/L, respectively. In accordance with the Beer-Lambert law, the results indicate that OD increases monotonically with POS length in humans, but the precise relationship is dependent on photoreceptor type. These results suggest that visual pigment concentration in rods is only about 48% of that found in cones. This may be due to the ubiquitous nature of artificial light that works to reduce the concentration of rhodopsin in rod photoreceptors.

Amoxicillin/clavulanate in combination with rifampicin/clarithromycin is bactericidal against Mycobacterium ulcerans.

Buruli ulcer (BU) is a skin neglected tropical disease (NTD) caused by Mycobacterium ulcerans. WHO-recommended treatment requires 8-weeks of daily rifampicin (RIF) and clarithromycin (CLA) with wound care. Treatment compliance may be challenging due to socioeconomic determinants. Previous minimum Inhibitory Concentration and checkerboard assays showed that amoxicillin/clavulanate (AMX/CLV) combined with RIF+CLA were synergistic against M. ulcerans. However, in vitro time kill assays (TKA) are a better approach to understand the antimicrobial activity of a drug over time. Colony forming units (CFU) enumeration is the in vitro reference method to measure bacterial load, although this is a time-consuming method due to the slow growth of M. ulcerans. The aim of this study was to assess the in vitro activity of RIF, CLA and AMX/CLV combinations against M. ulcerans clinical isolates by TKA, while comparing four methodologies: CFU enumeration, luminescence by relative light unit (RLU) and optical density (at 600 nm) measurements, and 16S rRNA/IS2404 genes quantification. TKA of RIF, CLA and AMX/CLV alone and in combination were performed against different M. ulcerans clinical isolates. Bacterial loads were quantified with different methodologies after 1, 3, 7, 10, 14, 21 and 28 days of treatment. RIF+AMX/CLV and the triple RIF+CLA+AMX/CLV combinations were bactericidal and more effective in vitro than the currently used RIF+CLA combination to treat BU. All methodologies except IS2404 quantitative PCR provided similar results with a good correlation with CFU enumeration. Measuring luminescence (RLU) was the most cost-effective methodology to quantify M. ulcerans bacterial loads in in vitro TKA. Our study suggests that alternative and faster TKA methodologies can be used in BU research instead of the cumbersome CFU quantification method. These results provide an in vitro microbiological support to of the BLMs4BU clinical trial (NCT05169554, PACTR202209521256638) to shorten BU treatment.