Maximum Fluorescence Intensity Research Articles

Photolysis of tolfenamic acid in aqueous and organic solvents: a kinetic study.

Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug that was studied for its photodegradation in aqueous (pH 2.0-12.0) and organic solvents (acetonitrile, methanol, ethanol, 1-propanol, 1-butanol). TA follows first-order kinetics for its photodegradation, and the apparent first-order rate constants (k obs) are in the range of 0.65 (pH 12.0) to 6.94 × 10-2 (pH 3.0) min-1 in aqueous solution and 3.28 (1-butanol) to 7.69 × 10-4 (acetonitrile) min-1 in organic solvents. The rate-pH profile for TA photodegradation is an inverted V (∧) or V-top shape, indicating that the cationic form is more susceptible to acid hydrolysis than the anionic form of TA, which is less susceptible to alkaline hydrolysis. The fluorescence behavior of TA also exhibits a V-top-shaped curve, indicating maximum fluorescence intensity at pH 3.0. TA is highly stable at a pH range of 5.0-7.0, making it suitable for formulation development. In organic solvents, the photodegradation rate of TA increases with the solvent's dielectric constant and solvent acceptor number, indicating solute-solvent interactions. The values of k obs decreased with increased viscosity of the solvents due to diffusion-controlled processes. The correlation between k obs versus ionization potential and solvent density has also been established. A total of 17 photoproducts have been identified through LC-MS, of which nine have been reported for the first time. It has been confirmed through electron spin resonance (ESR) spectrometry that the excited singlet state of TA is converted into an excited triplet state through intersystem crossing, which results in an increased rate of photodegradation in acetonitrile.

Optical responsive asphalt coating with temperature-sensitive TiO2 quantum dots: Formula and temperature adaptability

The application of conventional asphalt contributes to extremely high pavement temperature in hot season as its black color entails large solar absorption. In this study, optical responsive asphalt is proposed to control pavement temperature, which is developed by introducing temperature-sensitive TiO2 quantum dots (TiO2 QDs) into traditional asphalt. Temperature-sensitive TiO2 QDs are prepared by blending thermochromic polymer and TiO2 quantum dots with varied concentrations. Optical characterizations on temperature-sensitive TiO2 QDs have demonstrated that peak value of solar absorption in temperature-sensitive TiO2 QDs at 45 °C is 14.29 %–22.86 % higher than that at 15 °C; the maximum fluorescent intensity of temperature-sensitive TiO2 QDs at 45 °C is 8.5 % higher than that at 15 °C. The results from optical characterizations on temperature-sensitive TiO2 QDs modified asphalt show that the incorporation of temperature-sensitive TiO2 quantum dots endows asphalt low solar reflectance at high temperature and high solar absorption at low temperature. Fluorescent intensity of modified asphalt at 45 °C is increased by 21.6 %, 10.2 % and 5.7 % than that at 15 °C for asphalt containing 5 %, 10 %, and 20 % temperature-sensitive TiO2 QDs, respectively. Indoor solar radiation simulation tests have revealed that compared with traditional asphalt, temperature-sensitive TiO2 QDs modified asphalt coating could yield cooling effectiveness of 6.4 °C at high temperature. Meanwhile, outdoor solar radiation test indicates TiO2 QDs modified asphalt coating could realize warming effectiveness of 0.7 °C at low temperature. The outcomes on temperature-sensitive TiO2 QDs modified asphalt with temperature-adaptability properties makes an advancement in functional pavement.

Rapid detection of spermine by using a cost-effective carbon nanostructured aptasensor

Spermine is a polyamine that participates in ion channel regulation and cell proliferation. It is considered a biomarker for pancreatic cancer. In this study, a carbon nanostructure-based aptasensor has been developed to rapidly detect spermine in solution by relying on Förster resonance energy transfer (FRET). The FRET donor, carbon quantum dots (CDs), are bioconjugated to aptamers specific for spermine. CDs have an average diameter of 5.0 ± 2.5 nm and have the maximum fluorescence intensity emitting at 510 nm when excited at 400 nm. Due to the π-π* interaction between DNA-based aptamer and GO, a FRET quencher, CDs bioconjugated with aptamer (CDs-aptamer) can directly attach on the surface of GO, resulting in significant FRET quenching. In the presence of spermine, GO and CDs-Aptamer separate, and the fluorescence intensity of CDs is restored. The restored fluorescence intensity of CD-aptamer can be observed when the concentration of spermine increases from 0.1 to 250 nM. The sensing system in this study could be a cost-effective, user-friendly method to quickly detect spermine, a biomarker for pancreatic cancer.

Impacts of mixed ferrous sulfate-biochar additives on humification and bacterial community during electric field-assisted aerobic composting

This study assessed the impact of nine mixed ferrous sulfates and biochars on electric field-assisted aerobic composting (EAC), focusing on the spectroscopy of dissolved organic matter (DOM) and microbial communities. Adding 1.05% ferrous sulfate and 5.25% biochar to EAC increased the specific ultraviolet absorbances at 254 and 280 nm by 142.3% and 133.9% on day 35, respectively. This ratio accelerated the early response of carboxyl groups (—COOH) and lignin (CꘌC), enhancing the relative abundance of Thermobifida (4.0%) and Thermopolyspora (4.3%). The condition contributed to humus precursor formation on day 5, increasing the maximum fluorescence intensity of the humus-like component by 74.2% compared to the control on day 35. This study is the first to develop a combined and efficient organic and inorganic additive by multiple-variable experimentation for DOM humification. Consequently, it optimizes EAC for solid waste recycling.

Turn-Off Fluorescence Sensor for the Detection of Ferric Ion in Water Using Green Synthesized Wrightia coccinea Carbon Quantum Dot.

The current study report that the production of carbon quantum dots from Wrightia coccinea (WC) leaves using an eco-friendly, one-pot process. The structural, morphological, and optical characteristics of the CDs made from W. coccinea leaves by hydrothermal treatment at 200°C for six hours were assessed using a variety of spectroscopic and electron microscopy techniques. The average size of CD was found to be approximately 5nm using transmission electron microscopy (TEM) and the quantum yield of the produced CD was 15.6%. The synthesized CDs demonstrated extraordinary sensing capacity with a detection limit of 0.511µM for ferric ion detection. The impact of varying pH levels on the fluorescence behavior of CD was thoroughly investigated. The maximum fluorescence intensity was examined at pH 3. Therefore, to detect Fe3+ ions as best as possible, the pH of the entire solution was adjusted to a value of 3. Furthermore, the pH-dependent fluorescence feature of CDs can be exploited by pH-sensitive fluorescence sensors. In the future, this might provide an added advantage for pH-based fluorescence sensor applications.

Studies of Protein Binding to Biomimetic Membranes Using a Group of Uniform Materials Based on Organic Salts Derived From 8-Anilino-1-naphthalenesulfonic Acid.

Tuning the 8-anilino-1-naphthalenesulfonic acid (ANS) structure usually requires harsh conditions and long reaction times, which can result in low yields. Herein, ANS was modified to form an ANS group of uniform materials based on organic salts (GUMBOS), prepared with simple metathesis reactions and distinct cations, namely tetrabutylammonium (N4444), tetrahexylammonium (N6666), and tetrabutylphosphonium (P4444). These ANS-based GUMBOS were investigated as fluorescent probes for membrane binding studies with four proteins having distinct physicochemical properties. Liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine were employed as membrane models as a result of their ability to mimic the structure and chemical composition of cell membranes. Changes in fluorescence intensity were used to monitor protein binding to liposomes, and adsorption data were fitted to a Freundlich-like isotherm. It was determined that [N4444][ANS] and [P4444][ANS] GUMBOS have enhanced optical properties and lipophilicity as compared to parent ANS. As a result, these two GUMBOS were selected for subsequent protein-membrane binding studies. Both [N4444][ANS] and [P4444][ANS] GUMBOS and parent ANS independently reached membrane saturation within the same concentration range. Furthermore, distinct fluorescence responses were observed upon the addition of proteins to each probe, which demonstrates the impact of properties such as lipophilicity on the binding process. The relative maintenance of binding cooperativity and maximum fluorescence intensity suggests that proteins compete with ANS-based probes for the same membrane binding sites. Finally, this GUMBOS-based approach is simple, rapid, and involves relatively small amounts of reagents, making it attractive for high-throughput purposes. These results presented herein can also provide relevant information for designing GUMBOS with ameliorated properties.

Real-time identification of life-threatening necrotizing soft-tissue infections using indocyanine green fluorescence imaging.

Necrotizing soft-tissue infections (NSTIs) are life-threatening infections with a cumulative case fatality rate of 21%. The initial presentation of an NSTI is non-specific, frequently leading to misdiagnosis and delays in care. No current strategies yield an accurate, real-time diagnosis of an NSTI. A first-in-kind, observational, clinical pilot study tested the hypothesis that measurable fluorescence signal voids occur in NSTI-affected tissues following intravenous administration and imaging of perfusion-based indocyanine green (ICG) fluorescence. This hypothesis is based on the established knowledge that NSTI is associated with local microvascular thrombosis. Adult patients presenting to the Emergency Department of a tertiary care medical center at high risk for NSTI were prospectively enrolled and imaged with a commercial fluorescence imager. Single-frame fluorescence snapshot and first-pass perfusion kinetic parameters-ingress slope (IS), time-to-peak (TTP) intensity, and maximum fluorescence intensity (IMAX)-were quantified using a dynamic contrast-enhanced fluorescence imaging technique. Clinical variables (comorbidities, blood laboratory values), fluorescence parameters, and fluorescence signal-to-background ratios (SBRs) were compared to final infection diagnosis. Fourteen patients were enrolled and imaged (six NSTI, six cellulitis, one diabetes mellitus-associated gangrene, and one osteomyelitis). Clinical variables demonstrated no statistically significant differences between NSTI and non-NSTI patient groups (). All NSTI cases exhibited prominent fluorescence signal voids in affected tissues, including tissue features not visible to the naked eye. All cellulitis cases exhibited a hyperemic response with increased fluorescence and no distinct signal voids. Median lesion-to-background tissue SBRs based on snapshot, IS, TTP, and IMAX parameter maps ranged from 3.2 to 9.1, 2.2 to 33.8, 1.0 to 7.5, and 1.5 to 12.7, respectively, for the NSTI patient group. All fluorescence parameters except TTP demonstrated statistically significant differences between NSTI and cellulitis patient groups (). Real-time, accurate discrimination of NSTIs compared with non-necrotizing infections may be possible with perfusion-based ICG fluorescence imaging.

Activation of Piezo-1 Prevents Human Microvascular Endothelial Dysfunction During Acute Inhibition of Ceramide Formation

Despite the well-known damaging effects of elevated intracellular ceramides on human microvascular function, our recent work has shown that inhibition of ceramide formation through neutral sphingomyelinase (NSmase) promotes endothelial dysfunction in arterioles from healthy adults, manifested as endothelial production of hydrogen peroxide (H2O2), rather than nitric oxide (NO), in response to flow (flow-induced dilation; FID). Recent evidence suggests that ceramide prevents inactivation of Piezo-1, a shear-sensitive Ca2+ channel and inhibition of Piezo-1 reduces endothelial nitric oxide synthase (eNOS) activation in response to flow. Together, we hypothesized that ceramide-induced Piezo-1 activation is required to maintain NO-mediated FID in human microvessels and thus agonism of Piezo-1 during NSmase inhibition will prevent endothelial dysfunction. Arterioles (100-250μm) from healthy adults were dissected from discarded surgical adipose tissue. Vessels were cannulated in organ chambers, pre-constricted with endothelin-1, and changes in internal diameter in response to increases in flow were measured with videomicroscopy. Peroxy yellow 1 (PY1) fluorescent probe was used to assess endothelial H2O2 production in human umbilical vein endothelial cells (HUVECs). Mean% maximal dilation or fluorescent intensity±SE with two-way repeated measures ANOVA is reported. FID was preserved with Piezo-1 agonism (Yoda-1, 1μM, 30min) during NSmase inhibition (GW4869 4μM, 30min; 73±16.8, n=4 vs control 73±8.2, n=9; p>0.05), however FID was diminished in the presence of the eNOS inhibitor L-NAME (100μM; -2.6±11.3, n=5; p<0.05). A similar switch to NO-mediated FID was seen with C2-ceramide (5μM)+GW4869 (70.1±9.7 vs +L-NAME -3±9.7, n=4 both; p<0.05). NSmase inhibition increased H2O2 production in HUVECs (5.2±7.4 vs 83.0±31.6, n=6; p<0.05), an effect that was diminished with Yoda-1 (5.1±7.5, n=4; p<0.05) and C2-ceramide (10.7±9.2, n=5; p<0.05). These data suggest a role for Piezo-1 in NSmase-induced NO-signaling and provide mechanistic insight into how ceramide may exert beneficial effects within the human microvasculature. This research is supported by the National Institute of Health (NHLBI) R01HL160752 (JKF) and the American Heart Association (AHA) Predoctoral Fellowship 909315 (GSK). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Carbon Dots Modified Multi Dopants Nitrogen and Boron for an Early Detection of Lead in the Environment.

The remarkable optical properties and strong biocompatibility of carbon dots make them highly promising for applications in biochemical sensing and environmental testing. These carbon dots possess a surface that is easily modifiable. In this study, carbon dots have been successfully synthesized and modified by the addition of N and B dopants using the microwave method, along with the functionalization of their surface functional groups with bovine serum albumin (BSA). The maximum fluorescence intensity of N, B-CDs is observed at 462nm when excited at a wavelength of 352nm. N, B-CDs have a spherical size with a diameter ranging from 2 to 6nm, confirmed by UV-Vis absorption spectra and the presence of functional groups in the FT-IR absorption patterns. BSA-functionalized N, B-CDs as the fluorescent probe demonstrate great potential as a sensor for Pb(II) ions in water, with a very low detection limit of 1.05µg/L. This research could contribute to the development of fluorescence nanosensors.

Osteochondral fluid transport in an ex vivo system

ObjectiveAlterations to fluid transport from bone-to-cartilage may contribute to the development of osteoarthritis. Larger biological molecules found in bone may transport from bone-to-cartilage (e.g., insulin, 5kDa). However, many questions remain about fluid transport between these tissues. The objectives of this study were to (1) test for diffusion of 3kDa molecular tracers from bone-to-cartilage and (2) assess potential differences in bone-to-cartilage fluid transport between different loading conditions. DesignOsteochondral cores extracted from bovine femurs (N=10 femurs, 10 cores/femur) were subjected to either no-load (i.e., pure diffusion), pre-load only, or cyclic compression (5±2% or 10±2% strain) in a two-chamber transport system. The bone was placed into the bone compartment followed by a 3kDa dextran tracer, and tracer concentrations in the cartilage compartment were measured every 5 minutes for 120 minutes. Tracer concentrations were analyzed for differences in beginning, peak and equilibrium concentrations, loading effects, and time-to-peak tracer concentration. ResultsPeak tracer concentration in the cartilage compartment was significantly higher compared to beginning and equilibrium tracer concentrations indicating fluid transport from bone-to-cartilage. Cartilage-compartment tracer concentration, and maximum fluorescent intensity was influenced by strain magnitude. No time-to-peak relationship was found when comparing strain magnitudes impact on cartilage-compartment tracer concentration. ConclusionThis study shows that osteochondral fluid transport occurs from bone-to-cartilage with 3kDa dextran molecules. These are much larger molecules to move between bone and cartilage than previously reported. Further, these results demonstrate the potential for cyclic compression to impact osteochondral fluid transport. Determining the baseline osteochondral fluid transport in healthy tissues is crucial to elucidating the potential mechanisms of progression and onset of osteoarthritis.

Controlling Anti-Penetration Performance by Post-Grafting of Fluorinated Alkyl Chains onto Polystyrene-block-poly(vinyl methyl siloxane).

Polydimethylsiloxane (PDMS) has been widely used as a surface coating material, which has been reported to possess dynamic omniphobicity to a wide range of both polar and nonpolar solvents due to its high segmental flexibility and mobility. However, such high flexibility and mobility also enable penetration of small molecules into PDMS coatings, which alter the chemical and physical properties of the coating layers. To improve the anti-penetration properties of PDMS, a series of fluorinated alkyl segments are grafted to a diblock copolymer of polystyrene-block-poly(vinyl methyl siloxane) (PS-b-PVMS) using thiol-ene click reactions. This article reports the chemical characterization of these model fluorosilicone block copolymers and uses fluorescence measurements to investigate the dye penetration characteristics of polymer thin films. The introduction of longer fluorinated alkyl chains can gradually increase the anti-penetration properties as the time to reach the maximum fluorescence intensity (tpeak) gradually increases from 11 s of PS-b-PVMS to more than 1000 s of PS-b-P(n-C6F13-VMS). The improvement of anti-penetration properties is attributed to stronger inter-/intrachain interactions, phase segregation of ordered fluorinated side chains, and enhanced hydrophobicity caused by the grafting of fluorinated alkyl chains.

Exploring optical descriptors for rapid estimation of coastal sediment organic carbon and nearby land-use classifications via machine learning models

This study utilizes ultraviolet and fluorescence spectroscopic indices of dissolved organic matter (DOM) from sediments, combined with machine learning (ML) models, to develop an optimized predictive model for estimating sediment total organic carbon (TOC) and identifying adjacent land-use types in coastal sediments from the Yellow and Bohai Seas. Our results indicate that ML models surpass traditional regression techniques in estimating TOC and classifying land-use types. Penalized Least Squares Regression (PLR) and Cubist models show exceptional TOC estimation capabilities, with PLR exhibiting the lowest training error and Cubist achieving a correlation coefficient 0.79. In land-use classification, Support Vector Machines achieved 85.6 % accuracy in training and 92.2 % in testing. Maximum fluorescence intensity and ultraviolet absorbance at 254 nm were crucial factors influencing TOC variations in coastal sediments. This study underscores the efficacy of ML models utilizing DOM optical indices for near real-time estimation of marine sediment TOC and land-use classification.

Application of cationic dye pyronin G (Y) for quantitative photometric and fluorimetric determination of higher carboxylic acids in dairy products using extraction

In this work we propose to use a heptane-ethanol extract of the ionic associate of higher carboxylic acids with a cationic dye – pyronin G (Y) for quantitative extraction-photometric and extraction-fluorimetric determination of carboxylic acids in dairy products. The resulting ion associate is characterized by a maximum of optical density at 510 nm and intense of fluorescence with a maximum at 566 nm. The maximum optical density and fluorescence intensity of the ion associate is observed during its extraction with octanol/heptane from aqueous solutions with pH = 11.25. The quantum yield of ionic associates of higher carboxylic acids with pyronine G (Y) relative to the standard solution of fluorescein was calculated. A technique has been developed for the extraction-fluorimetric determination of hydrophobic acids in milk and cheese. The method has been tested in the determination of carboxylic acids content in milk and cheese samples. The content of higher carboxylic acids, determined by the method with pyronin G, in milk was (6.6 ± 0.15) · 10–4 M, in cheese – (1.1 ± 0.10) · 10–3 mol/kg. The obtained results of extraction-photometric and extraction-fluorimetric determination of carboxylic acids in dairy products make it possible to recommend the developed method in the practice of institutions of the corresponding profile.

An ultra-sensitive SARS-CoV-2 antigen optical biosensor based on angiotensin converting enzyme 2 (ACE-2) functionalized magnetic-fluorescent silica nanoparticles.

This work reports on the design and synthesis of an angiotensin-converting enzyme 2 (ACE-2) functionalized magnetic fluorescent silica nanoparticles (Fe-FSNP) as a biosensing platform to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen. Iron oxide (Fe3O4) nanoparticles were synthesized via ultrasonic-assisted coprecipitation and then coated with fluorescent silica nanoparticles (FSNP) through thesol-gelmethod forming the Fe-FSNP samples. Silica obtained from local geothermal powerplant was used in this work and Rhodamine B was chosen as the incorporated fluorescent dye, hence this reports for the first time ACE-2 was immobilized on the natural silica surface. The Fe-FSNP nanoparticle consists of a 18-25 nm magnetic core and a silica shell with a thickness of 30 nm as confirmed from the transmission electron microscopy image. Successful surface functionalization of the Fe-FSNP with ACE-2 as bioreceptor was conducted through hydrosylilation reaction and confirmed through the Fourier transform infrared spectroscopy. The detection of SARS-Cov-2 antigen by Fe-FSNP/ACE2 was measured through the change in its maximum fluorescence intensity at 588 nm where fluorescence- quenching had occurred. The biosensing platform showed a rapid response at 30 min with a linear range of 10-6to 10-2μg ml-1. The magnetic-fluorescent properties of the nanoparticle enables an ultra-sensitive detection of SARS-Cov-2 antigen with the limit of detection as low as 2 fg ml-1.

The impact of ageing on the distribution of preformed anti-HLA and anti-MICA antibody specificities in recipients from eastern China prior to initial HSCT

BackgroundWith the development of Hematopoietic Stem Cell Transplantation (HSCT) technology, increasing numbers of elderly patients were undergoing allogeneic HSCT and elderly patients with hematologic malignancies could benefit most from it. Preformed donor-specific human leukocyte antigen (HLA) antibodies (DSA) were associated with graft failure in HLA-mismatched allogeneic HSCT and the absence of DSA was the main criterion of selecting the donor. Except for sensitization events such as transfusion, pregnancy or previous transplantation, ageing affects the humoral immune response both quantitatively and qualitatively. To evaluate the prevalence and distribution of anti-HLA and antibodies of MHC class I chain related antigens A (MICA) specificities in different age groups before initial HSCT would provide HLA and MICA specific antibody profiles under the impact of ageing, which could provide meaningful information in the process of selecting suitable HLA-mismatched donors by avoiding preformed DSA.ResultsThere were no significant differences in the distribution of anti-HLA class I, class II and anti-MICA antibodies among the three age groups in this study except that a significant lower negative ratio of anti-HLA class I, class II antibodies and higher positive rate of MICA antibodies with maximum mean fluorescent intensity (MFI) > 5000 in the elderly than in young age group. The distribution of antibody specificities against HLA -A, -B, -C, -DR, -DQ, -DP and MICA antigens in the three age groups were generally consistent. The anti-HLA class I antibody specificities with higher frequencies were A80,A68;B76,B45;Cw17, which were unlikely to become DSA in Chinese. Anti-HLA class II antibody specificities were more likely to become potential DSA than class I.DR7, DR9, DQ7, DQ8 and DQ9 were most likely to become potential DSA.ConclusionsThe prevalence of anti-HLA and anti-MICA antibodies increased slightly as age increased. While ageing had a small impact on the distribution of antibody specificity frequencies against HLA-A, -B, -C, -DR,-DQ, -DP and MICA antigens in recipients awaiting initial HSCT from East China. The risk of developing preformed DSA was basically consistent in the three age groups and the elderly group might be more favorable in HLA-mismatched HSCT due to higher positive rate of anti-MICA antibody.

Heat-induced gelation of egg white proteins depending on heating temperature: Insights into protein structure and digestive behaviors in the elderly in vitro digestion model

This study investigated the effects of heating temperature of egg white gels (EWGs) on the digestive characteristics by heating egg white (EW) to reach 75 °C (EWG-75) and 95 °C (EWG-95). The gel protein structure showed a decrease in the maximum tryptophan fluorescence intensity and a significant increase in the surface hydrophobicity of EWGs compared to EW (P < 0.05). The total and reactive free sulfhydryl groups were higher in the EWGs than in the EW (P < 0.05). While the proportions of α-helical and β-sheet structures remained similar in EW and EWG-75 (P > 0.05), EWG-95 exhibited a notable decrease in α-helix content (P < 0.05) and an increase in β-sheet content (P < 0.05). Furthermore, EWG-95 displayed higher hardness and cohesiveness than EWG-75 (P < 0.05). In the adult and elderly in vitro digestion models, EWG-95 exhibited the highest protein digestibility (50.44 % and 54.65 % in the models of elderly and adult subjects, respectively) after GI digestion (P < 0.05), followed by EWG-75 and EW. The electrophoretogram of the digesta revealed more intense protein bands in the elderly digestion model, particularly in the gastric digesta of EW, indicating slower digestion compared to the adult model. Therefore, EW should be appropriately heated before consumption, especially for elderly individuals, to facilitate efficient protein digestion and absorption.

Preparation and Evaluation of Liposomes Containing Ethanol and Propylene Glycol as Carriers for Nicotine.

Nicotine is a fat-soluble substance that is easily absorbed through the skin and mucosal tissues of the human body. However, its properties, such as light exposure, heat decomposition, and volatilization, restrict its development and application in external preparations. This study focused on the preparation of stable nicotine-encapsulated ethosomes. During their preparation, two water-phase miscible osmotic promoters, ethanol and propylene glycol (PG), were added to obtain a stable transdermal delivery system. Skin nicotine delivery was enhanced through the synergistic action of osmotic promoters and phosphatidylcholine in binary ethosomes. Various characteristics of the binary ethosomes were measured, including the vesicle size, particle size distribution, and zeta potential. In order to optimize the ratio of ethanol and PG, the skin permeability test was performed on mice in vitro in a Franz diffusion cell to compare cumulative skin permeabilities. The penetration depth and fluorescence intensity of rhodamine-B-entrapped vesicles in isolated mouse skin samples were observed using laser confocal scanning microscopy. When ethanol:PG was used in a ratio of 5:5 (w/w), binary ethosomes were found to be the most stable, had the highest encapsulation rate (86.13 ± 1.40), smallest particle size (106.0 ± 11.0) nm, maximum transdermal depth (180 μm), and maximum fluorescence intensity (160 AU). Nicotineencapsulated ethosomes (ethanol: PG = 5:5, w/w) were an efficient and stable transdermal delivery system. The nicotine-encapsulated ethosomes containing ethanol and PG are considered to be safe and reliable as a transdermal administration agent, which does not irritate the skin.

Three Novel Rhodamine 6G-Based Colorimetric and Fluorescent pH Switches.

Three rhodamine 6G derivatives (REHA, RETA and REDA) were designed and synthesized by connecting rhodamine 6G and 3-methyl-2-thiophenal with hydrazine hydrate, ethylenediamine and diethylenetriamine, respectively. In CH3CN/H2O (50/50, v/v), the absorbance of REHA, RETA and REDA at 528nm was suddenly enhanced by 3.2, 3.8 and 7.2 times within the pH range of 3.03-2.31, 3.05-2.32 and 3.06-2.34, respectively, and the solution changed from colorless to pink. Meanwhile, the maximal fluorescence intensity sharply increased by 53.9, 26.6 and 24.9 times in the pH range of 3.86-3.46, 3.88-3.47 and 3.89-3.48, respectively, and the solution changed from dark to bright yellow-green fluorescence. REHA, RETA and REDA can act as highly selective and sensitive colorimetric and fluorescent pH switches with good recyclability and anti-interference ability. The response mechanism of REHA, RETA and REDA to pH was studied by 1H NMR spectroscopy, and their application in indicating small pH changes in dyeing wastewater was investigated.

The bacterial influencing mechanisms of salinity fluctuations in a brackish-water lake on the dissolved organic matter characteristics of pore water

The dissolved organic matter (DOM) components in lake water have been widely studied; however, few previous studies have considered the growth of Phragmites australis in brackish lakes. It has not been well understood how salinity variations influence the DOM compositions in pore water and its bacterial mechanisms in lakes with Phragmites australis. This experiment included three salinity groups (1,200 mg/L, 3,600 mg/L, and 6,000 mg/L) to study the interactions between bacteria and DOM in pore water under a salinity gradient. The results showed that the maximum fluorescence intensity (Fmax) of DOM measured by excitation-emission fluorescence spectroscopy decreased with increasing salinity. Higher salinity reduced the Fmax of protein-like substances and resulted in DOM becoming more aromatic. Salinity affected DOM composition due to the responses of functional bacterial communities. Thiobacillus was salt-tolerant and dominated in the sediments, and its relative abundance was negatively correlated with the Fmax of protein-like components. The relative abundance of Flavobacterium showed a positive correlation with salinity and a negative correlation with the Fmax of the fulvic acid-like component. Pseudomonas, Brevundimonas, and Polaromonas were negatively correlated with salinity and the Fmax of the fulvic acid-like component, while being positively correlated with the Fmax of tyrosine-like and aromatic protein substances. Higher salinity inhibited the metabolism gene modules of tryptophan and tyrosine. The results of this study may offer a novel perspective on comprehending the biochemical cycling of fluorescent DOM, encompassing tryptophan-like, tyrosine-like, and fulvic acid-like components in brackish lakes with fluctuating salinity.

Assessment of the correlation between optical properties and CQD preparation approaches

Various production procedures, for carbon quantum dots (CQDs), are still being extensively researched to understand the nature of CQD luminescence. This study compares and examines the impact of chemical as well as green methods on the structural and optical properties of CQDs. We present a straightforward, cost-effective bottom-up method for producing fluorescent CQDs from lemon peels (L-CQDs), orange juice (O-CQDs), and citric acid (C-CQDs) without having to deal with time-consuming or ineffective post-processing processes. The proposed green synthesis has no toxic by-products, and the residual resources utilized promote the large-scale production of CQDs. X-ray diffraction, high-resolution transmission electron microscopy, FTIR, Raman, DLS, and UV–Vis spectroscopy are utilized to investigate the structure and optical characteristics of the prepared CQDs. The as-prepared CQDS possess small particle sizes of 5.6 nm, 6.2 nm, and 1.1 nm for L-CQDs, O-CQDs, and C-CQDs samples, respectively. FTIR results reveal the coexistence of carboxylic and hydroxyl groups on the surface of the CQDs, as also supported by zeta-potential values. Maximal fluorescence intensity was reached at excitation wavelengths of 365, 250, and 280 nm with an emission color of blue, indigo, and light blue for L-CQDs, O-CQDs, and C-CQDs, respectively. The presented approaches show a high quantum yield of 88% for O-CQDs, 49% for L-CQDs, and 37% for C-CQDs. Due to their minuscule particle size, perfect water solubility, high stability, and tunable luminescence properties, the prepared CQDs are preferred for potential applications in multicolor imaging, metal ion sensing, and wastewater technologies.