Spectrophotometric Measurements Research Articles

Measurement of light absorption by chromophoric dissolved organic matter using a type-II liquid capillary waveguide: assessment of an achievable accuracy

Light absorption by chromophoric dissolved organic matter (CDOM) in the ocean is often measured using liquid waveguide capillary cells coupled to spectral array detectors. This type of optical setup is affected by several sources of uncertainties related to the waveguide and the detector. Uncertainties from the waveguide arise from errors in the effective path length and the effects of water salinity, while errors related to the detector are due to the non-linearity in the response, internal stray light, and wavelength accuracy. Here, uncertainties in the measurements of the spectral absorption coefficient of CDOM due to the optical setup itself were investigated in detail. The related systematic errors were very often significant (2–15%) and larger than expected from simple measurement uncertainty (±1%). However, they can be corrected by characterizing the detector’s response for non-linearity and stray light, regularly performing calibrations for the detector’s wavelength response, and routinely measuring the waveguide’s effective path length. Including such corrections and timely calibrations reduces the uncertainties related to the spectrophotometric measurements to about ±2%. Uncertainties related to the necessary handling of samples are not included here.

Investigation of optical properties of molybdenum trioxide (MoO3) thin films using neural networks

Nowadays, transition metal oxide, the semiconductor molybdenum trioxide (MoO3), is a favorable choice because it has several industrial applications and alluring qualities. It has a significant role as an industrial catalyst due to its electrochromic properties. The optical behavior of the MoO3 thin film onto various substrates of the powder of MoO3 was investigated. x-ray diffraction analysis revealed an orthorhombic structure. Measurements of the average crystallite size and dislocation density were obtained, which were 132.8 nm and 5.7× 10–4 nm−2, respectively. Spectrophotometric measurements of transmittance (T) and reflectance (R) at normal incidence in the 300–1400 nm wavelength range of the film onto various substrates were examined. The dispersion and indirect optical transitions and nonlinear optical parameters were identified for glass and quartz substrates. An estimation of the optical behavior of the MoO3 thin film using the artificial neural network (ANN) model was carried out. Experimental data were used as inputs. The optical characterization of ANN modeling outputs provides excellent results. Error values support the success of the modeling process, with a mean squared error value of < 10−1. Moreover, the theoretical equation describing the experimental results was obtained depending on the ANN model, representing the relation between the inputs and outputs. According to the findings of this research, the ANN model can be utilized as an efficient tool to simulate and predict the optical parameters of the MoO3 thin film. Additionally, it can establish strong connections between theoretical and experimental fields.

Lab-on kit: A 3D printed portable device for optical and electrochemical dual-mode detection

The hyphenation of electrochemical methods and optical methods in a single portable device is expected to be a challenging combination to enhance the information which can be gained on complex chemical systems. In this paper, a low-cost spectrophotometric device based on low-cost electronics integrated with an electroanalytical cell equipped with a screen printed electrode (SPE) and assembled exploiting a DIY approach, is presented. This easy to use device allowed spectrophotometric and electroanalytical measurements to be performed simultaneously providing simultaneous information and enabling concomitant comparison and autovalidation of the results collected. The analytical robustness and precision of the proposed system was successfully tested on solutions containing mixtures of Patent Blue (E-131) and Brilliant Blue (Erioglaucine E-133), two food dyes displaying optical and redox properties very similar to each other.

Mechanistic study of the acidic aqueous solution of chrome alum chemical dosimeter: Steady state, pulse radiolysis and conductivity studies

It is crucial to have an efficient and reliable approach to ensure an optimum traceability in high dose range and high dose rate dosimetry for radiation processing (food irradiation, surgery devices sterilization …). Chemical solution dosimeters are well suited for this purpose. By using γ-irradiation and pulse radiolysis, we evaluated the performances of the chrome alum KCr(SO4)2·12H2O based on the radiation induced oxidation of Cr3+ to Cr6+ in N2O-saturated aqueous solutions buffered at pH 4 by the hydroxyl radical (•OH). With combination of spectrophotometric and conductometric measurements, a mechanism has been put forward to elucidate the oxidation of Cr3+ leading to Cr6+. The suggested mechanism involves an initial adduct formation, [Cr3+ – •OH], that enables inner-sphere electron transfer. As far as dosimetry is concerned, this study showed that the absorbance at 350 nm of the radiation induced Cr6+ increases linearly with the dose with a yield of G (Cr6+) = 0.128 μmol J−1. No dose rate effect was observed up to 80 kGy min−1. This aqueous solution could be used for chemical dosimetry, mainly in the high dose range (up to 5 kGy) and high dose rate (up to 80 kGy min−1). The main advantage of using this aqueous solution is its equivalence to human tissue in terms of radiation absorption properties.

Testing the physical properties stability of Zinc (8-hydroxyquinoline) thin films toward stable photodetection performance: Effect of annealing

In this study, the effect of thermal annealing on the structural and optical properties of thermally evaporated zinc (8-hydroxyquinoline) (ZnQ2) thin films is discussed in detail. Differential scanning calorimetry analysis revealed the thermal stability of the ZnQ2 powder up to 540 K. Fourier transform infrared spectrometer characterizations revealed the stability of the ZnQ2 molecular structure up to 423 K. The annealing effect on the surface morphology of the ZnQ2 films was tracked using the field emission scanning electron microscope (FE-SEM) technique, which revealed grain growth up to 423 K achieving the highest surface smoothness. Moreover, UV–Vis-NIR spectrophotometric measurements were used to examine how annealing affects the optical characteristics of the prepared films. The optical bandgap of ZnQ2 augmented when the annealing temperature increased to 373 K. The dispersion parameters were estimated from the analysis of the complex refractive index following the single oscillator model. The behavior of nonlinear optical susceptibility suggested the validity of utilizing ZnQ2 thin films in IR and UV optical switching applications and UV photodetection applications.

Quality Assurance and In-vitro Bioequivalence Analysis of Amlodipine Besylate Tablets

The proliferation of generic brands in the local pharmaceutical market makes it increasingly difficult for health professionals and patients to choose the optimal drug. The study aimed to assess the physicochemical parameters of generic amlodipine besylate tablets utilizing in-vitro testing to eliminate health hazards and maximize safety. Five brands (A, B, C, D, and E) of amlodipine besylate tablets (5 mg) were examined for six in-vitro tests; thickness, hardness, friability, uniformity of weight, disintegration, dissolution, and thin layer chromatography (TLC). The dissolution test revealed that Brand D had the highest percentage of drug release at 5 minutes (106.2%), followed by Brand E (103.2%), A (70.7%), B (64.4%), and C (61.0%), respectively. The spectrophotometric measurement was carried out at 240 nm. All five brands satisfied the British Pharmacopeia standard for uncoated tablet weight homogeneity (less than 5% variance) and disintegration within 15 minutes. Brand A has the longest disintegration time (4.37 minutes), whereas Brand B has the shortest (3.05). Brand E had the maximum hardness of 8.7 kg/cm², and Brand B had the lowest hardness of 3 kg/cm². All five brands had a friability percentage of less than 1%, with bread B having the highest (0.91%) and brand E, lowest (0.10%), all tablets crumbled after 15 minutes. All brands passed the quality assessment test. Conclusion: The Quality Assurance and in-vitro bioequivalence assay methods used in this study are dependable, simple, and inexpensive, and they can be used consistently to evaluate amlodipine tablets and other solid-dosage pharmaceutical products.

French coastal network for carbonate system monitoring: the CocoriCO2 dataset

Abstract. Since the beginning of the industrial revolution, atmospheric carbon dioxide (CO2) concentrations have risen steadily and have induced a decrease of the averaged surface ocean pH by 0.1 units, corresponding to an increase in ocean acidity of about 30 %. In addition to ocean warming, ocean acidification poses a tremendous challenge to some marine organisms, especially calcifiers. The need for long-term oceanic observations of pH and temperature is a key element to assess the vulnerability of marine communities and ecosystems to these pressures. Nearshore productive environments, where a large majority of shellfish farming activities are conducted, are known to present pH levels as well as amplitudes of daily and seasonal variations that are much larger than those observed in the open ocean. Yet, to date, there are very few coastal observation sites where these parameters are measured simultaneously and at high frequency. To bridge this gap, an observation network was initiated in 2021 in the framework of the CocoriCO2 project. Six sites were selected along the French Atlantic and Mediterranean coastlines based on their importance in terms of shellfish production and the presence of high- and low-frequency monitoring activities. At each site, autonomous pH sensors were deployed, both inside and outside shellfish production areas, next to high-frequency CTD (conductivity–temperature–depth) probes operated through two operating monitoring networks. pH sensors were set to an acquisition rate of 15 min, and discrete seawater samples were collected biweekly in order to control the quality of pH data (laboratory spectrophotometric measurements) as well as to measure total alkalinity and dissolved inorganic carbon concentrations for full characterization of the carbonate system. While this network has been up and running for more than 2 years, the acquired dataset has already revealed important differences in terms of pH variations between monitored sites related to the influence of diverse processes (freshwater inputs, tides, temperature, biological processes). Data are available at https://doi.org/10.17882/96982 (Petton et al., 2023a).

Production of vitamin B12 via microbial strains isolated from marine and food sources in Egypt

Background Vitamin B12 is a very important water-soluble vitamin, which was first isolated from the liver as an anti-pernicious anemia factor. The sole source of vitamin B12 is the animal-based food. It has a complicated structure and requires expensive multi-steps to be synthesized chemically. Intriguingly, vitamin B12 can be produced through microbial fermentation by microorganisms in a cheap and more effective manner. Objective This study aims to isolate and characterize microorganisms that have the capability to produce vitamin B12. In addition, the current work aims to optimize the vitamin B12 production conditions by isolating strains using suitable waste materials to obtain a high vitamin B12 yield. Materials and methods Different bacterial and yeast isolates were isolated from marine and food samples using the pour-plate technique. These isolates were screened for vitamin B12 production using a specific growth medium that lacked vitamin B12 and a test indicator bacterium. The content of vitamin B12 was estimated using spectrophotometer measurement and high-performance liquid chromatography (HPLC). The isolates that showed high vitamin B12 productivity were identified using MALDI-TOF technique. The identified strains were implemented for the optimization of vitamin B12 production to reveal the most proper and optimum conditions for the production. Response surface methodology (RSM) was employed to enhance the production of vitamin B12 in a flask scale. Agro-industrial wastes such as molasses were used for vitamin B12 production using the most optimum conditions as determined by RSM. Results and conclusion Eighty-seven actinomycetes, bacterial, and yeast isolates were screened for vitamin B12 production. Out of these isolates, 15 showed high vitamin B12 productivity. We found that bacilli and yeast isolates were the most productive among the tested cocci and actinomycetes isolates. The highly productive Bacillus and yeast isolates were identified using the MALDI-TOF analysis. The isolates were identified as Candida pelliculosa, Geotrichum candidum, Bacillus subtilis and Bacillus sp. One strain of Candida pelliculosa (coded BYI), three strains of Geotrichum candidum (coded as MZYC, MZYD, and MZYG) were selected for studying the effect of sugar type and inoculum size on the yield of vitamin B12 production. Strain MZYD was selected for the statistical modelling using RSM to optimize seven factors for the vitamin B12 production. These factors included temperature, fermentation time, salt concentration, pH, sugar concentration, inoculum size, and aeration. Five factors i.e., temperature, pH, sugar concentration, and inoculum size were shown to significantly improve the vitamin B12 production. A maximum yield of 64.21 μg/100 ml was obtained using the optimized RSM conditions. These optimized conditions were used to produce vitamin B12 using molasses as a raw material for the microbial growth.

NOVEL APPROACH FOR ONE-POT SELF-ASSEMBLED MONOLAYER PREPARATION OF GOLD TIPPED CdSe/CdS NANORODS

In this study, CdSe/CdS nanorods (NRs) were synthesized via hot injection method to perform simultaneous self-assembly studies with gold tip formation on the nanorods. In this new approach, we propose and demonstrate reductant chemical and gold organosol-free synthesis of gold-tipped nanocrystals on the subphase. Instead of gold organosol usage, gold precursor was prepared by addition of gold source into subphase, and photocatalytic reduction of gold on the tip of nanorods was achieved by exciting the samples under UV-light excitation. Reduction of gold nanoparticles on the tip of NRs was also tried by heating effect, which results in nanopillar formation. The optical properties of these nanorods were determined by spectrophotometric measurements, and gold-tipped nanorods were imaged by TEM analysis. This method enables self-assembly of nanorods and following gold tip formation on the subphase, and it can pave the way to prepare well-defined metal-tipped oriented surfaces that can be used for optical and photocatalysis applications.

Study on the Optical and Gas-Sensing Performance of Zn-doped CuO Films

The pure copper oxide thin film was deposited on glass substrates by SILAR method with 30 cycles. To examine the doping effect, Zn-doped films at different doping ratios were prepared under the same conditions as the undoped film. The XRD, SEM and Raman measurements were performed to investigate the morphological and structural properties of the samples. Analysis showed increasing aggregation and amorphous structure with doping. The optical parameters were characterized by spectrophotometer measurement and relevant formulas. The band gap energies were determined to increase from 2.50 to 2.79 eV with the increasing Zn rate. The Hervé and Vandamme, Moss and Ravindra relations were used to determine the refractive index. The room temperature gas-sensing performance for the undoped and doped samples were reported and the responses for 5 ppm gas were calculated as 249 %, 800 %, 189 % and 15 % for the CuO, 1Zn:CuO, 3Zn:CuO and 5Zn:CuO, respectively. The response of CuO thin films changed with doping, and 1% Zn doping rate was determined as the optimal rate in this study.

Structural, Optical and Optoelectrical Properties of CuAlSnS4 Thin Films

The present study used chemical deposition to deposit thin copper aluminum tin sulfide (CATS4) layers onto clean glass substrates. X-ray diffraction analysis was utilized to explore the crystalline structure of the CATS4 films, which refers to the CATS4 films having a cubic crystal structure. Energy-dispersive X-ray analysis showed the presence of Cu, Al, Sn, and S peaks in the CATS4 films, and their atomic ratio is close to 1:1:1:4. Spectrophotometric measurements of optical transmittance and reflectance spanning the 400–2500 nm spectral range were performed to describe the optical properties of the CATS4 layers. The CATS4 films demonstrated a direct energy gap transition between 1.42 and 1.31 eV. Further, increasing the layer thickness enhanced the refractive index and Urbach energy of the CATS4 films. The inspected CATS4 films showed better optoelectrical properties with increasing thickness, including improved optical conductivity, optical resistivity, optical carrier concentration, relaxation time, and optical mobility. Increasing the thickness of the CATS4 films increased their nonlinear optical indices. Additionally, the hot probe apparatus verified the p-type semiconducting characteristics of CATS4 films.

Principles and Limitations of miRNA Purification and Analysis in Whole Blood Collected during Ablation Procedure from Patients with Atrial Fibrillation.

Background: MicroRNA (miRNA) have the potential to be non-invasive and attractive biomarkers for a vast number of diseases and clinical conditions; however, a reliable analysis of miRNA expression in blood samples meets a number of methodological challenges. In this report, we presented and discussed, specifically, the principles and limitations of miRNA purification and analysis in blood plasma samples collected from the left atrium during an ablation procedure on patients with atrial fibrillation (AF). Materials and Methods: Consecutive patients hospitalized in the First Department of Cardiology for pulmonary vein ablation were included in this study (11 with diagnosed paroxysmal AF, 14 with persistent AF, and 5 without AF hospitalized for left-sided WPW ablation-control group). Whole blood samples were collected from the left atrium after transseptal puncture during the ablation procedure of AF patients. Analysis of the set of miRNA molecules was performed in blood plasma samples using the MIHS-113ZF-12 kit and miScript microRNA PCR Array Human Cardiovascular Disease. Results: The miRNS concentrations were in the following ranges: paroxysmal AF: 7-23.1 ng/µL; persistent AF: 4.9-66.8 ng/µL; controls: 6.3-10.6 ng/µL. The low A260/280 ratio indicated the protein contamination and the low A260/A230 absorbance ratio suggested the contamination by hydrocarbons. Spectrophotometric measurements also indicated low concentration of nucleic acids (<10 ng/µL). Further steps of analysis revealed that the concentration of cDNA after the Real-Time PCR (using the PAXgene RNA Blood kit) reaction was higher (148.8 ng/µL vs. 68.4 ng/µL) and the obtained absorbance ratios (A260/A280 = 2.24 and A260/A230 = 2.23) indicated adequate RNA purity. Conclusions: Although developments in miRNA sequencing and isolation technology have improved, detection of plasma-based miRNA, low RNA content, and sequencing bias introduced during library preparation remain challenging in patients with AF. The measurement of the quantity and quality of the RNA obtained is crucial for the interpretation of an efficient RNA isolation.

Evaluation of Leaf Chlorophyll Content from Acousto-Optic Hyperspectral Data: A Multi-Crop Study

Chlorophyll plays a crucial role in the process of photosynthesis and helps to regulate plants’ growth and development. Timely and accurate evaluation of leaf chlorophyll content provides valuable information about the health and productivity of plants as well as the effectiveness of agricultural treatments. For non-contact and high-performance chlorophyll content mapping in plants, spectral imaging techniques are the most widely used. Due to agility and rapid random-spectral-access tuning, acousto-optical imagers seem to be very attractive for the detection of vegetation indices and chlorophyll content assessment. This laboratory study demonstrates the capabilities of an acousto-optic imager for evaluation of leaf chlorophyll content in six crops with different biophysical properties: Ribes rubrum, Betula populifolia, Hibiscus rosa-sinensis, Prunus padus, Hordeum vulgare and Triticum aestivum. The experimental protocol includes plant collecting, reference spectrophotometric measurements, hyperspectral imaging data acquisition, processing and analysis and building a multi-crop chlorophyll model. For 90 inspected samples of plant leaves, the optimal vegetation index and model were found. Obtained values of chlorophyll concentrations correlate well with reference values (determination coefficient of 0.89 and relative error of 15%). Applying a multi-crop model to each pixel, we calculated chlorophyll content maps across all plant samples. The results of this study demonstrate that acousto-optic imagery is very promising for fast chlorophyll content assessment and other laboratory spectral-index-based measurements.

Study of color degradation in package prints: Analyzing kinetics with principal component analysis

AbstractColor degradation is a pressing issue in various fields like food and medicine packaging, as well as printed materials, leading to a loss or distortion of vital information. Therefore, understanding how the color of package prints evolves over time is essential for product quality assessment and effective product life cycle management. This study focuses on investigating color changes in prints on blister foils, widely used in the medicine and packaging industries. To assess fading characteristics, samples printed via the gravure process have been exposed to a Xenon Test Chamber (B‐SUN). Spectrophotometric measurements of the prints have been conducted using a spectroradiometer, and the data have been analyzed using principal component analysis (PCA). The fading nature of cyan and black prints aligns with Type IV, while magenta and yellow prints correspond to Type II, as described by Giles. Notably, cyan and black inks demonstrated resistance toward fading at the end of the exposure, with a minor exception. The investigation involved curve fitting, revealing a consistent first‐order kinetic model governing fading rates throughout the exposure time. High R2 values (0.96–0.99) and low root means square error values (0.02–0.08) are observed across all cases. While color fading involves diverse kinetics, the fading rate consistently adheres to a singular first‐order kinetic path. The study highlights that yellow ink is most sensitive to light, followed by magenta ink. These findings offer valuable insights for optimizing packaging materials and ensuring product quality in industries reliant on printed materials. By mitigating color degradation, manufacturers can enhance the longevity and appeal of their products, reinforcing consumer trust and satisfaction. Furthermore, the effective utilization of PCA as a data analysis tool offers a valuable approach for future investigations in color science and related fields.

Impact of ZnO nanopriming on physiological and biochemical traits of wheat (Triticum aestivum L.) seedling

To ascertain the ideal dosage of ZnO NPs (Zinc Oxide Nanoparticles), we conducted an investigation on the priming effects of varying concentrations of ZnO NPs on germination and physio-biochemical parameters of wheat. In this study, ZnO NPs were synthesized and characterized for their physico-chemical properties followed by confirmation of the formation of ZnO NPs. Throughout this study, wheat seeds were subjected to ZnO NPs at various concentrations of 5, 50, 100, 250, and 500 ppm for a period of 4 h via continuous aeration. The primed seeds were sowed in plastic bags, allowed to grow for 21 days, following which comprehensive evaluations of physio-biochemical attributes were conducted. At 250 ppm, an impressive 100% of seeds successfully germinated compared to the control group. The examined physiological factors such as shoot length, root length, and fresh as well as dry weights of leaf and root tissues all exhibited notable increases with the ascending concentrations of ZnO NP up to 250 ppm. However, beyond this threshold, at 500 ppm, these parameters experienced a decline. Inductively coupled plasma atomic absorption spectrophotometer (ICP-AAS) measurements validated the progressive increase in Zinc content in the nanoprimed seedlings, further affirming the dose-dependent trend. Zinc oxide nanoparticles notably improved key biochemical features, including elevated levels of total chlorophyll, malondialdehyde (MDA), total protein, and the accumulation of osmolytes such as proline and glycine-betaine. Additionally, the presence of ZnO NPs led to increased activity of antioxidant enzymes like superoxide dismutase (SOD) and catalase in a dose-dependent mananer. Collectively, the amassed data underscores the efficacy of the 250 ppm ZnO NPs treatment, which emerged as superior in comparison to both the control group and other administered treatments. These findings underscore the potential of ZnO NPs at a concentration of 250 ppm as a valuable seed nanopriming agent, effectively enhanced germination and robust early-stage growth in young plants.

Modulation of Stem Cell Factor by Forskolin Inhibits the Progression of Tubule Interstitial Fibrosis

Purpose Forskolin is primarily found in the roots of the Coleus forskohlii plant, historically employed in Southeast Asian and Indian Ayurvedic medicine. Mast cells play a crucial role in fibrosis progression, yet their activation and inhibition in animal models are understudied; thus, we explored forskolin’s impact on kidney fibrosis. Materials and Methods Forskolin was evaluated in a mouse model for stem cell factor-induced histamine release, and plasma histamine levels were measured using the enzyme-linked immunosorbent assay. Kidney fibrosis was developed by unilateral ureteral obstruction (UUO). Renal function was assessed by spectrophotometric measurements of serum blood urea nitrogen (BUN) and creatinine. The gene expression of collagen, transforming growth factor-beta (TGF-β), α-smooth muscle actin (α-SMA), interleukin-1 beta (IL-1β), and mast cell protease-5 (MCPT-5) in the kidney was analyzed by reverse transcription polymerase chain reaction (RT-PCR). Histopathological changes in the renal tissues were examined by hematoxylin and eosin (H&amp;E) and Masson’s trichome stain. Results Our results showed that 3 mg/kg forskolin inhibited SCF-induced plasma histamine release in a mouse model. In the 7-day UUO model, forskolin significantly showed inhibition of serum creatinine and blood urea nitrogen compared with the disease group. Forskolin significantly inhibited elevated expression of collagen, TGF-β, α-SMA, IL-1β, and MCPT-5 in the kidneys. Histopathological observation of H&amp;E and Masson trichome-stained kidney forskolin demonstrated a reduction in inflammatory cells, pelvic and tubular dilation, and fibrosis. Conclusion Forskolin showed an anti-fibrotic effect in UUO-induced renal fibrotic mice. Most significantly, forskolin administration showed a decrease in the expression of the mast cell protease MCPT5 in the kidneys. These results imply that forskolin, through modifying SCF activity, may be a viable potential treatment for the attenuation of tubule-interstitial fibrosis.

An in vitro evaluation of the effects of fluoride, CPP-ACP, or resin infiltration on discoloration caused by pediatric supplements.

White spot lesions are more susceptible to staining agents due to their porous structure. This study examines the impact of white spot lesion treatments on discoloration caused by pediatric supplements. Three treatments (fluoride, casein phosphopeptide-amorphous calcium phosphate [CPP-ACP], resin infiltration), a control, and their respective syrup-based subgroups (iron and black elderberry syrups) were established, each with eight teeth. Artificial white spot lesions were induced, and weekly applications of fluoride varnish, daily applications of CPP-ACP paste, or a single resin infiltration procedure were performed on the white spot lesions within the treatment groups over 4 weeks. Simultaneously, samples were exposed daily to iron or black elderberry syrups. Spectrophotometer measurements were taken at baseline, after demineralization (T0), and after 1 (T1), 2 (T2), and 4 weeks (T4). ΔE00 values were calculated. Statistical analysis was conducted using a three-way mixed-design ANOVA, with the significance level set at P = .05. At T4, ΔE00 values from all groups exceeded the clinical acceptability limit of 1.8. At T2 and T4, the ΔE00 values obtained from the black elderberry syrup subgroups were significantly higher (P < .001). At T4, the highest ΔE00 values were seen in the CPP-ACP groups (P < .001). The lowest ΔE00 values at T2 and T4 were observed in the resin infiltration groups (P < .05). Supplements containing ferrous sulfate and black elderberry extract caused color changes in white spot lesions that exceeded the clinical acceptability limit. Resin infiltration of white spot lesions provides advantages over remineralization treatments, particularly in minimizing discoloration induced by pediatric supplements.

Discoloration and biosorption of Brilliant green dye in seawater using living biomass of the microalga Phaeodactylum tricornutum

Pollution by dyes is a serious environmental problem. Marine waters receive pollutants from many sources, however, there are few studies that deal with the elimination of pollutants from these environments. The search for effective, cheap, and ecological procedures to remove dyes from seawater is a current challenge. Biosorption meets these requirements, but it is necessary to find the best biosorbent for the operating conditions. Since microalgal biomass is considered a good biosorbent, the efficiency of living biomass from the marine microalga Phaeodactylum tricornutum to remove the Brilliant green dye from seawater was evaluated in this work. This dye showed spontaneous discoloration in seawater, showing a decrease in the amount of dye measured spectrophotometrically but not when measured by HPLC. Consequently, the difference between discoloration and true removal should be considered. It is shown that the determination of the biomass efficiency as biosorbent through spectrophotometric measurements could be wrong in some cases. Batch experiments were performed varying operational parameters, such as initial concentration of dye, contact time, and pH of the solution. At the lowest concentration of the dye (5 mg L-1), the algal biomass (0.4 g L-1) achieved total decolorization and removal (through biosorption) within 7 h, while at the highest concentration (200 mg L-1), discoloration was 96.3%, but removal was 32.6%. The spontaneous discoloration followed a pseudo-second-order kinetics. Pseudo-first-order kinetics and Langmuir isotherm best described the removal process, predicting a maximum biosorption capacity of 161.52±5.95 mg g-1. This natural biomass had a higher efficiency than other more complex biosorbents.

Biofilm formation by Staphylococcus pseudintermedius on titanium implants

Osteomyelitis often involves Staphylococcus spp. as the isolated genus in domestic animal cases. Implant-related infections, frequently associated with biofilm-forming microorganisms like staphylococci species, necessitate careful material selection. This study assessed biofilm formation by Staphylococcus pseudintermedius on titanium nuts used in veterinary orthopaedic surgery. Biofilm quantification employed safranin staining and spectrophotometric measurement, while bacterial counts were determined in colony-forming units (CFU). Scanning Electron Microscopy (SEM) evaluated the biofilm morphology on the surface of titanium nuts. All samples had CFU counts. Absorbance values that evidence biofilm formation were observed in seven of the eight samples tested. SEM images revealed robust bacterial colonization, and significant extracellular polymeric substance production, and the negative control displayed surface irregularities on the nut. Whole genome sequencing revealed accessory Gene Regulator (agr) type III in six samples, agr IV and agr II in two each. Genes encoding hlb, luk-S, luk-F, siet, se_int, and the icaADCB operon were identified in all sequenced samples. Other exfoliative toxins were absent. Biofilm formation by S. pseudintermedius was detected in all samples, indicating the susceptibility of orthopaedic titanium alloys to adhesion and biofilm formation by veterinary species. The biofilm formation capacity raises concerns about potential post-surgical complications and associated costs.

Metabolite profiling and in-silico studies show multiple effects of insecticidal actinobacterium on Spodoptera littoralis

The polyphagous pest, Spodoptera littoralis (Boisduval), poses a significant global economic threat by gregariously feeding on over a hundred plant species, causing substantial agricultural losses. Addressing this challenge requires ongoing research to identify environmentally safe control agents. This study aimed to elucidate the insecticidal activity of the metabolite (ES2) from a promising endophytic actinobacterium strain, Streptomyces sp. ES2 EMCC2291. We assessed the activity of ES2 against the eggs and fourth-instar larvae of S. littoralis through spectrophotometric measurements of total soluble protein, α- and β-esterases, polyphenol oxidase (PPO), and catalase enzyme (CAT). The assessments were compared to commercial Biosad® 22.8% SC. Untargeted metabolomics using LC-QTOF-MS/MS identified 83 metabolic compounds as chemical constituents of ES2. The median lethal concentration (LC50) of ES2 (165 mg/mL) for treated Spodoptera littoralis eggs showed significant differences in polyphenol oxidase and catalase enzymatic activities, while the LC50 of ES2 (695 mg/mL) for treated S. littoralis fourth instar larvae showed lower significance in α- and β-esterase activities. Molecular docking of ES2 identified seven potent biocidal compounds, showing strong affinity to PPO and catalase CAT proteins in S. littoralis eggs while displaying limited binding to alpha and beta esterase proteins in the larvae. The results contribute to the understanding of ES2 as a promising alternative biopesticide, providing insights for future research and innovative applications in sustainable pest management strategies.