Reduction In Fluorescence Intensity Research Articles

Synthesis and Characterization of a Magnetic Molecular Imprinted Polymer for Tetracycline Quantification in Food Samples

AbstractIn the present work, we synthesized and tested a magnetic molecularly imprinted polymer (mag‐MIP) sensor for the detection of tetracycline in food samples. High‐performance liquid chromatography (HPLC) and spectrofluorometry were employed for tetracycline determination. The mag‐MIP was polymerized on the surface of Fe3O4@SiO2 magnetic nanoparticles using the following substances: 4 mmol of methacrylic acid as the functional monomer, 20 mmol of ethylene glycol dimethacrylate (EGDMA) as the cross‐linking agent, 82.5 mg of benzoyl peroxide as the radical initiator, and 30 ml of acetonitrile as the solvent. The physicochemical characteristics of the proposed mag‐MIP, including adsorption capabilities and selectivity, were studied and compared with those of a magnetic non‐molecularly imprinted polymer (mag‐NIP). The analytical curve was constructed in the range of 1.0×10−5–8.0×10−5 mol L−1, LOD: 3.3×10−6, LOQ: 1.1×10−5 mol L−1. The results obtained from the adsorption analysis showed that the highest adsorption capacity of the mag‐MIP at equilibrium was 8.247 mg g−1 and that the tetracycline adsorption process followed the Langmuir adsorption isotherm model and pseudo‐second‐order reaction kinetics. The proposed mag‐MIP also exhibited good results when subjected to fluorescence analysis; an increase in tetracycline concentration resulted in an increase in the adsorption capacity, and this led to the effective removal of tetracycline with the reduction of fluorescence intensity. The applicability of the proposed mag‐MIP was evaluated in honey, cow milk, and egg samples through recovery tests conducted using samples containing spiked tetracycline concentration at two different concentration levels (1.7×10−5 and 2.5×10−5 mol L−1), where we obtained recovery percentages in the range of 73.2–87.2 % (HPLC) and 90.5–103.7 % (spectrofluorometry).

Evaluating the biomolecular interaction between delamanid/formulations and human serum albumin by fluorescence, CD spectroscopy and SPR: Effects on protein conformation, kinetic and thermodynamic parameters

Delamanid is an anti-tuberculosis drug used for the treatment of drug-resistant tuberculosis. Since delamanid has a high protein bound potential, even patients with low albumin levels should experience high and rapid delamanid clearance. However, the interaction between delamanid and albumin should be better controlled to optimize drug efficacy. This study was designed to evaluate the binding characteristics of delamanid to human serum albumin (HSA) using various methods: fluorescence spectroscopy, circular dichroism (CD), surface plasmon resonance (SPR), and molecular docking simulation. The fluorescence emission band without any shift indicated the interaction was not affected by the polarity of the fluorophore microenvironment. The reduction of fluorescence intensity at 344 nm was proportional to the increment of delamanid concentration as a fluorescence quencher. UV-absorbance measurement at the maximum wavelength (λmax, 280 nm) was evaluated using inner filter effect correction. The HSA conformation change was explained by the intermolecular energy transfer between delamanid and HSA during complex formation. The study, which was conducted at temperatures of 298 K, 303 K, and 310 K, revealed a static quenching mechanism that correlated with a decreased of bimolecular quenching rate constant (kq) and binding constant (Ka) at increased temperatures. The Ka was 1.75–3.16 × 104 M−1 with a specific binding site with stoichiometry 1:1. The negative enthalpy change, negative entropy change, and negative Gibbs free energy change demonstrated an exothermic-spontaneous reaction while van der Waals forces and hydrogen bonds played a vital role in the binding. The molecular displacement approach and molecular docking confirmed that the binding occurred mainly in subdomain IIA, which is a hydrophobic pocket of HSA, with a theoretical binding free energy of −9.33 kcal/mol. SPR exhibited a real time negative sensorgram that resulted from deviation of the reflex angle due to ligand delamanid-HSA complex forming. The binding occurred spontaneously after delamanid was presented to the HSA surface. The SPR mathematical fitting model revealed that the association rate constant (kon) was 2.62 × 108 s−1M−1 and the dissociation rate constant (koff) was 5.65 × 10−3 s−1. The complexes were performed with an association constant (KA) of 4.64 × 1010 M−1 and the dissociation constant (KD) of 2.15 × 10−11 M. The binding constant indicated high binding affinity and high stability of the complex in an equilibrium. Modified CD spectra revealed that conformation of the HSA structure was altered by the presence of delamanid during preparation of the proliposomes that led to the reduction of secondary structure stabilization. This was indicated by the percentage decrease of α-helix. These findings are beneficial to understanding delamanid-HSA binding characteristics as well as the drug administration regimen.

Comparing the Developmental Toxicity Delay and Neurotoxicity of Benzothiazole and Its Derivatives (BTHs) in Juvenile Zebrafish.

In this study, a semi-static water exposure method was employed to investigate the early developmental and neurotoxic effects of four benzothiazole substances (BTHs), namely benzothiazole (BTH), 2-mercaptobenzothiazole (MBT), 2-hydroxybenzothiazole (BTON), and 2-aminobenzothiazole (2-ABTH), on zebrafish at an equimolar concentration of 10 μM. The findings revealed that all four BTHs exerted certain impacts on early development in zebrafish. MBT stimulated spontaneous movement in juvenile zebrafish, whereas BTON inhibited such movements. Moreover, all four BTHs hindered the hatching process of zebrafish larvae, with MBT exhibiting the strongest inhibition at 24 h post-fertilization (hpf). Notably, MBT acted as a melanin inhibitor by suppressing melanin production in juvenile zebrafish eyes and weakening phototaxis. Additionally, both BTH and BTON exhibited significantly lower speeds than the control group and other test groups under conditions without bright field stimulation; however, their speeds increased to average levels after percussion stimulation, indicating no significant alteration in motor ability among experimental zebrafish groups. Short-term exposure to these four types of BTHs induced oxidative damage in zebrafish larvae; specifically, BTH-, MBT-, and BTON-exposed groups displayed abnormal expression patterns of genes related to oxidative damage. Exposure to both BTH and MBT led to reduced fluorescence intensity in transgenic zebrafish labeled with central nervous system markers, suggesting inhibition of central nervous system development. Furthermore, real-time quantitative PCR results demonstrated abnormal gene expression associated with neural development. However, no significant changes were observed in 2-ABTH gene expression at this concentration. Overall findings indicate that short-term exposure to BTHs stimulates neurodevelopmental gene expression accompanied by oxidative damage.

Linalool acts as a chemical chaperone by inhibiting amyloid-β aggregation

Linalool is a neuroprotective monoterpene found in essential oils from aromatic plants. Linalool's effectiveness in AD animal models has been established previously, but its mechanisms of action remain unclear. Therefore, this study aims to investigate whether linalool binds directly to the amyloid beta (Aβ) fibrils to understand it's role in preventing neurodegeneration. The anti-aggregation ability of Linalool was determined using Dithiothreitol (DTT), and thermal aggregation assays followed by Thioflavin T (ThT) binding assay. AD animals were treated with Linalool, and Thioflavin T staining was used to check the binding of linalool to Aβ fibrils in rat brain tissue sections. Preliminary studies revealed the anti-aggregation potential of linalool under the thermal and chemical stimulus. Further, in ThT binding assay Linalool inhibited Aβ aggregation, binding directly to Aβ fibrils. The reduced fluorescence intensity of ThT in AD brain tissues following linalool administration, highlights its neuroprotective potential as a therapeutic agent for AD.

Enzyme-free and label-free detection of HER2 in human serum based on Ag+-released hybridization chain reaction signal amplification

The overexpression of human epidermal growth factor receptor 2 (HER2) has been linked to aggressive breast cancer and worse clinical outcomes. However, accurately measuring HER2 remains challenging, due to its low serum content. Herein, we developed a novel method for HER2 detection in serum by the combination of aptamer with C-Ag+-C structure, Ag+-released hybridization chain reaction (Ag+-HCR) and coprecipitation of Ag+ and gold nanoparticles (AuNPs) in the solution including Eosin Y (EY) and AgI colloids. Following the aptamer bound to HER2, signal amplification occurred through the release of numerous Ag+ by Ag+-HCR. This process subsequently induced AuNPs aggregation on the surface of AgI colloids, resulting in reduced fluorescence intensity of EY in the supernatant. The reduced value of EY fluorescence intensity in the supernatant was proportional to the level of HER2. Under optimized reaction conditions, a wide detection range was obtained between 0.09 and 9000 pg/mL with a limit of detection of 11.7 fg/mL in diluted human serum, and 96 serum samples in a 96-well plate could be measured simultaneously by a microtiter plate reader within 2 h. Moreover, the quantitative results of HER2 were consistent with those obtained using the enzyme-linked immunosorbent assay kit (r = 0.9995). Therefore, leveraging the delicate design of Ag+-HCR signal amplification, this enzyme-free, label-free, and effective method has demonstrated to be capable of detecting HER2 in serum due to its high sensitivity. Remarkably, this method may be extended to detect other cancer-related proteins and genes by replacing the corresponding target sequences.

N-octylpyridine hydrogen sulphate ionic liquid for multifunctional fluorescent response in different solvents

Ionic liquids (ILs) have attracted considerable interest in the last two decades owing to their unique fluorescent properties. Herein, N-octylpyridine hydrogen sulphate ([OP]HSO4) was synthesised and characterised using 1H NMR and infrared spectroscopies. In addition, the fluorescence spectra of [OP]HSO4 in water, methanol, ethanol and acetonitrile were studied. In a single solvent, as the concentration of the solvent (methanol, ethanol or acetonitrile) increases, the fluorescence intensity of the IL first increases and then decreases. A similar trend was observed in their mixed solvents with water. Moreover, the fluorescence intensity of [OP]HSO4 decreases with increasing temperature. A fluorescence intensity reduction of only 4.46% for [OP]HSO4 after continuous scanning for 40 cycles under the maximum excitation state was analysed. The lack of photobleaching observed in [OP]HSO4 indicates its good photobleaching resistance.

High-fat diet enhances cell proliferation and compromises intestinal permeability in a translational canine intestinal organoid model

BackgroundEmerging evidence underscores the responsiveness of the mammalian intestine to dietary cues, notably through the involvement of LGR5 + intestinal stem cells in orchestrating responses to diet-driven signals. However, the effects of high-fat diet (HFD) on these cellular dynamics and their impact on gut integrity remain insufficiently understood. Our study aims to assess the multifaceted interactions between palmitic acid (PA), cell proliferation, and the intestinal epithelial barrier using a canine colonoid model. Canine models, due to their relevance in simulating human intestinal diseases, offer a unique platform to explore the molecular mechanisms underlying HFD derived intestinal dysfunction.ResultsCanine colonoids were subjected to PA exposure, a surrogate for the effects of HFD. This intervention revealed a remarkable augmentation of cell proliferative activity. Furthermore, we observed a parallel reduction in transepithelial electrical resistance (TEER), indicating altered epithelium barrier integrity. While E-cadherin exhibited consistency, ZO-1 displayed a noteworthy reduction in fluorescence intensity within the PA-exposed group.ConclusionsBy employing canine intestinal organoid systems, we provide compelling insights into the impact of PA on intestinal physiology. These findings underscore the importance of considering both cell proliferative activity and epithelial integrity in comprehending the repercussions of HFDs on intestinal health. Our study contributes to a deeper understanding of the consequences of HFD on intestinal homeostasis, utilizing valuable translational in vitro models derived from dogs.

Exquisite visualization of mitophagy and monitoring the increase of lysosomal micro-viscosity in mitophagy with an unusual pH-independent lysosomal rotor

BackgroundMitophagy plays indispensable roles in maintaining intracellular homeostasis in most eukaryotic cells by selectively eliminating superfluous components or damaged organelles. Thus, the co-operation of mitochondrial probes and lysosomal probes was presented to directly monitor mitophagy in dual colors. Nowadays, most of the lysosomal probes are composed of groups sensitive to pH, such as morpholine, amine and other weak bases. However, the pH in lysosomes would fluctuate in the process of mitophagy, leading to the optical interference. Thus, it is crucial to develop a pH-insensitive probe to overcome this tough problem to achieve exquisite visualization of mitophagy. ResultsIn this study, we rationally prepared a pH-independent lysosome probe to reduce the optical interference in mitophagy, and thus the process of mitophagy could be directly monitored in dual color through cooperation between IVDI and MTR, depending on Förster resonance energy transfer mechanism. IVDI shows remarkable fluorescence enhancement toward the increase of viscosity, and the fluorescence barely changes when pH varies. Due to the sensitivity to viscosity, the probe can visualize micro-viscosity alterations in lysosomes without washing procedures, and it showed better imaging properties than LTR. Thanks to the inertia of IVDI to pH, IVDI can exquisitely monitor mitophagy with MTR by FRET mechanism despite the changes of lysosomal pH in mitophagy, and the reduced fluorescence intensity ratio of green and red channels can indicate the occurrence of mitophagy. Based on the properties mentioned above, the real-time increase of micro-viscosity in lysosomes during mitophagy was exquisitely monitored through employing IVDI. Significance and noveltyCompared with the lysosomal fluorescent probes sensitive to pH, the pH-inert probe could reduce the influence of pH variation during mitophagy to achieve exquisite visualization of mitophagy in real-time. Besides, the probe could monitor the increase of lysosomal micro-viscosity in mitophagy. So, the probe possesses tremendous potential in the visualization of dynamic changes related to lysosomes in various physiological processes.

Antimicrobial Activity of 2-(Piperazin-1-yl)naphtho[2,3-d]thiazole-4,9-dione against Staphylococcus Strains.

There is an urgent need to discover and develop novel antibacterial agents. Accordingly, we synthesised 2-(piperazin-1-yl)naphtho[2,3-d]thiazole-4,9-dione (PNT), which exhibits antimicrobial activity. The aim of this study was to characterise PNT as an effective antimicrobial agent. Fluorescence microscopy was used to measure PNT's uptake into microbial cells (strains of Staphylococcus epidermidis, Staphylococcus aureus, and methicillin-resistant S. aureus (MRSA)), transmission electron microscopy (TEM) was used to investigate the influence of PNT on the configuration of microbial cells, and a DNA gyrase supercoiling assay was used to investigate whether PNT inhibits DNA gyrase. PNT was taken up by more than 50% of microbial cells within 30 min. Using TEM, hollowed-out bacterial cytoplasms were observed in the specimen treated with PNT, although there was no disintegration of the bacterial membrane. In the DNA gyrase supercoiling assay, a dose-dependent reduction in fluorescence intensity was observed as the concentration of PNT increased. This suggests that PNT is taken up by microbial cells, resulting in cell disruption, and it reveals that one of the mechanisms underlying the antimicrobial activity of PNT is the inhibition of DNA gyrase.

Generation of Autoantibodies in Metal-catalyzed Oxidatively Damaged DNA in Various Cancer Subjects.

Free radicals exist as unstable and highly reactive substances, occurring both in and outside the body. Free radicals are labeled as electron-hungry molecules formed from metabolism and endogenous burning of oxygen. They are transported in cells, upsetting the arrangement of molecules and instigating cellular injury. Hydroxyl radical (•OH) is one of the highly reactive free radicals, which damages the biomolecules in its close vicinity. In the present study, DNA was modified by the hydroxyl radical generated via the Fenton reaction. The •OH-oxidized/-modified DNA (Ox-DNA) was characterized by UV-visible and fluorescence spectroscopy. Thermal denaturation was performed to reveal the susceptibility of modified DNA toward heat. The role of Ox-DNA was also established in probing the presence of autoantibodies against Ox-DNA in the sera of cancer patients by direct binding ELISA. The specificity of autoantibodies was also checked by inhibition ELISA. In biophysical characterization, an increase in hyperchromicity and relative reduction of fluorescence intensity for Ox-DNA was reported compared to the native DNA analog. A thermal denaturation study revealed that Ox-DNA was highly susceptible to heat in comparison to the native conformers. The direct binding ELISA showed the prevalence of autoantibodies from cancer patient sera separated for immunoassay detection against the Ox-DNA. The generated autoantibodies against the Ox-DNA were detected as highly specific against bladder, head, neck, and lung cancer, which was further confirmed by the inhibition ELISA for the serum and IgG antibodies. The generated neoepitopes on DNA molecules are recognized as nonself by the immune system, which leads to the formation of autoantibodies in cancer patients. Therefore, our study confirmed that oxidative stress plays a role in the structural perturbation of DNA and makes it immunogenic.

Microfluidic fabrication of core–shell fucoxanthin nanofibers with improved environmental stability for reducing lipid accumulation in vitro

Fucoxanthin is a xanthophyll carotenoid that possesses potent antioxidant, anti-obesity, and anti-tumor properties. However, its limited solubility in water and susceptibility to degradation create challenges for its application. In this study, a microfluidic coaxial electrospinning technique was used to produce core–shell zein-gelatin nanofibers for encapsulating fucoxanthin, enhancing its bioavailability, and improving its stability. In comparison to uniaxially-loaded fucoxanthin nanofibers, the encapsulation efficiency of fucoxanthin reached 98.58 % at a core–shell flow rate ratio of 0.26:1, representing a 14.29 % improvement. The photostability of the nanofibers increased by 74.59 % after three days, UV stability increased by 38.82 % after 2 h, and temperature stability also significantly improved, demonstrating a protective effect under harsh environmental conditions (P < 0.05). Additionally, nanofibers effectively alleviated oleic acid-induced reactive oxygen species production and reduced fluorescence intensity by 54.76 %. MTT experiments indicated great biocompatibility of the nanofibers, effectively mitigating mitochondrial membrane potential polarization and lipid accumulation in HepG2 cells. Overall, the microfluidic coaxial electrospinning technique enables promising applications of fucoxanthin delivery in the food industry.

Water sensitive fluorescence tuning of V-shaped ESIPT fluorophores: Substituent effect and trace amount water sensing in DMSO

Highly sensitive nature of excited state intramolecular proton transfer (ESIPT) functionality in organic fluorophores made them potential candidates for developing environmental sensors and bioimaging applications. Herein, we report the synthesis of V-shaped Dapsone based Schiff base ESIPT derivatives (1–3) and water sensitive wide fluorescence tuning from blue to red in DMSO. Solid-state structural analysis confirmed the V-shaped molecular structure with intramolecular H-bonding and substituent dependent molecular packing in the crystal lattice. 1 showed strong solid-state fluorescence (λmax = 554 nm, Φf = 21.2 %) whereas methoxy substitution (2 and 3) produced tunable but significantly reduced fluorescence (λmax = 547 (2) and 615 nm (3), Φf = 2.1 (2) and 6.5 % (3)). Interestingly, aggregation induced emission (AIE) studies in DMSO-water mixture revealed water sensitive fluorescence tuning. The trace amount of water (less than 1 %) in DMSO converted the non-emissive 1–3 into highly emissive state due to keto tautomer formation. Further increasing water percentage produced deprotonated state of 1–3 in DMSO and enhanced the fluorescence intensity with red shifting of emission peak. At higher water fraction, 1–3 in DMSO produced aggregates and red shifted the emission with reduction of fluorescence intensity. The concentration dependent fluorescence study revealed the very low detection limit of water in DMSO. The limit of detection (LOD) of 1, 2 and 3 were 0.14, 1.04 and 0.65 % of water in DMSO. Hence, simple Schiff bases of 1–3 showed water concentration dependent keto isomer, deprotonated and aggregated state tunable fluorescence in DMSO. Further, scanning electron microscopic (SEM) studies of 1–3 showed water concentration controlled self-assembly and tunable fluorescence.

Exploration of the impact of graphene oxide, acetylenic gemini, and CTAT on the photophysical and aggregation properties of dipolar coumarin 153.

Advanced spectroscopic techniques have been utilized to study the interaction between the laser dye coumarin 153 (C153) and graphene oxide (GO) nanoparticles. GO was synthesized using a modified Hummers' method and characterized by UV-vis spectroscopy, Raman laser spectroscopy, FTIR-ATR spectroscopy, FESEM, HR-TEM, and XRD techniques. The GO@C153 composite was formed by mixing two aqueous solutions of GO and C153 due to their strong interaction through stacking and hydrophobic interactions. In this case, GO acts as an effective fluorescence quencher for C153 molecules, which undergo H-type aggregation in the presence of GO. The Stern-Volmer equation and time-dependent fluorescence studies were utilized to analyse the mechanism of fluorescence quenching. According to the findings, both static and dynamic quenching processes are responsible for the reduction in fluorescence intensity. The effect of surfactants (both cetyltrimethylammonium p-toluenesulfonate (CTAT) and synthesized N,N'-dihexadecyl-N,N,N',N'-tetramethyl-N,N'-but-2-ynediyl-di-ammonium chloride (16-4-16)) on the aggregation and photophysical properties of the dye was investigated using surface tensiometry, conductometry, UV-vis absorption spectroscopy, steady-state fluorescence measurements, DLS, and time-dependent fluorescence spectroscopy. Surfactants change the microenvironment of the C153 dye, leading to spectrum shifting and a higher quantum yield, which causes a rapid rise in fluorescence intensity in the micellar medium. It has been noted that in a micellar medium rather than in an aqueous one, the luminous intramolecular charge transfer (ICT) state of C153 stabilises. Lastly, we investigated the photophysical behavior of the GO-C153-micelle ternary system and discovered that, in the presence of a micellar medium, the quenched and blue-shifted (H-type aggregation) fluorescence peak of C153 (in the presence of GO) began to intensify once more. The main goal of this work is to create an effective and fairly cost powerful fluorescence sensor. Additionally, the ternary system (GO-C153-micelle) analytical idea can be employed to identify the onset of micelle formation. In wastewater treatment analysis, the GO-C153-surfactant ternary system concept can also be used to regenerate the adsorbent (in this case, GO) from dye molecules by allowing the dye molecules to exit the adsorbent and enter the micellar medium.

The influence of male HBV infection on sperm quality, embryonic development, and assisted reproductive outcomes.

What is the impact of male hepatitis B virus (HBV) infection on sperm quality, embryonic development, and assisted reproductive outcomes? Male HBV infection did not affect assisted reproductive outcomes, but HBV is capable of impairing human sperm and embryo formation in the early stages following fertilization. HBV is found in germ cells and early embryos of patients with HBV. HBV may impair human sperm function via increasing reactive oxygen species. We conducted a retrospective cohort study of 1581 infertile couples, including 496 male patients clinically confirmed to have hepatitis B infection, and a laboratory study of effects of HBV proteins on early embryos, using human embryonic stem cells (hESCs), human sperm, and golden hamster oocytes. In total, 1581 infertile couples (24-40 years of age) who were admitted to a reproductive medicine center to undergo ART for the first time from January 2019 to November 2021 were selected as the study subjects. The case group was composed of 469 couples with hepatitis B surface antigen (HBsAg)-seropositive men and seronegative women (368 for IVF and 101 for ICSI treatment). The negative control group was composed of 1112 couples where both men and women were seronegative for hepatitis B antigen. We divided these couples into three comparison groups (IVF/ICSI, IVF, and ICSI). IVF of human sperm and hamster oocytes was used to evaluate the influence of the HBV HBs protein on formation of 2-cell embryos. Mitochondrial membrane potential (MMP) of hESCs was assayed via a fluorescence intensity system. Immunofluorescence staining of the phosphorylated histone H2A.X was applied to identify DNA damage to hESCs caused by the HBV X (HBx) protein. Sperm concentration, total sperm number, and sperm with normal morphology were decreased in the couples with HBV-infected males in couples who were undergoing IVF/ICSI (male HBV(+) vs control: 469 vs 1112 individuals; sperm number, P < 0.01; normal sperm morphology, P < 0.01), IVF (368 vs 792; sperm number, P < 0.01; normal sperm morphology, P ≤ 0.05), and ICSI (101 vs 306; sperm number, P < 0.01; normal sperm morphology, P < 0.001). There was no significant difference in the number of embryo cleavages, blastocyst formation, biochemical pregnancy rate, clinical pregnancy rate, and live-birth rate between case and control groups. The 2PN fertilization rate in IVF/ICSI (P < 0.01) and ICSI (P < 0.05) couples, and the number of 2PN-fertilized oocytes in IVF (P < 0.001) couples were lower in couples with male HBV infection compared to control couples. HBV HBs protein reduced the MMP of human sperm and decreased 2-cell embryo formation in IVF of human sperm and zona-free-hamster oocyte. A reduction in fluorescence intensity and immunofluorescence staining of phosphorylated histone H2A.X indicated that HBx caused MMP impairment and DNA damage in human early embryonic cells, respectively. N/A. HBV can be examined in samples of sperm or discarded IVF early embryos from HBsAg-seropositive men and seronegative women. The hESC model in vitro may not fully mimic the natural embryos in vivo. This study furthers our understanding of the influence of male HBV infection on embryonic development. Our results suggest that a semen-washing process may be necessary for male patients with HBV undergoing ART to minimize the potential negative effects of HBV infection on the early embryo. This work was funded by grants from the National Natural Science Foundation of China, grant numbers 81870432 and 81570567 to X.Z., 81571994 to P.S., and 81950410640, the Natural Science Foundation of Guangdong Province, China (No. 2023A1515010660 to X.Z.), and the Li Ka Shing Shantou University Foundation (Grant No. L11112008). The authors have no conflicts of interest.

ZIF-8 coated flexible carbon cloth substrates for CO2 sensing applications

In this work, the application of Zeolitic Imidazolate Framework (ZIF-8) as a CO2 sensing material is investigated. The ball milling technique, a green and solvent-free alternative, was applied for synthesis and deposition on a sensing substrate, made of carbon cloth. The synthesized ZIF-8 via the ball milling exhibits excellent CO2 adsorption and detection characteristics, as demonstrated through fluorescence measurements with 82% reduction in fluorescence intensity upon CO2 exposure. To inspect the structural morphology, the crystallinity, and the pore size of the ZIF-8 sample, characterization tests including XRD, FTIR, BET, and FE-SEM were conducted. The characterization tests revealed the formation of a new phase of ZIF-8 (ZIF-L) using the ball milling procedure. Additionally, the MOF was coated on a carbon cloth substrate using ball milling at different milling speeds: 100 rpm, 300 rpm and 500 rpm. The MOF-coated substrates were characterized using SEM and EDS analysis to confirm the attachment of the MOF to the substrates. Gas chromatography tests were conducted to assess the capability of the coated substrates to absorb CO2. The sample, produced at a milling speed of 300 rpm, exhibited a favorable coating and CO2 adsorption with CO2 concentration reduction of 53.46%, thus, making it suitable for deployment as a sensing layer in miniature gas sensor.

The antifungal mechanism of Monarda citriodora essential oil, hexanal and their combined vapours on Aspergillus foetidus

BackgroundThe increased reliance on synthetic fungicides for managing postharvest pathogens resulted in the rise of fungicide-resistant pathogen strains. Previous studies have reported essential oils (EOs) as a promising alternative to synthetic fungicides. However, higher concentrations are required for their practical application, which can alter the taste profile of the stored produce. Synergistic combinations of EO volatiles can reduce the active concentrations, thereby mitigating undesirable taste profile changes. However, very few studies have emphasised the changes in the mode of action of EO volatiles when applied as a synergistic combination. This study aimed to decipher the mode of action of Monarda citriodora essential oil (MEO) and hexanal vapour combination (M + H) against the newly identified postharvest pathogen of apple Aspergillus foetidus. ResultsThe M + H vapour treatment synergistically inhibited the spore germination of A. foetidus at the concentration of 144.23 μL L−1 air (MEO) and 96.15 μL L−1 air (hexanal). Propidium Iodide staining and ergosterol content analysis revealed that vapours compromised the plasma membrane integrity. Hence, there was an extracellular leakage of cytoplasmic components, reduced extracellular pH and increased conductivity. Furthermore, calcofluor white staining showed reduced fluorescence intensity, indicating a compromised cell wall. Reduced chitin content in the cell walls of vapour treated mycelia authenticated the results. 2′,7′-Dichlorofluorescin diacetate (DCFDA) staining revealed the generation and accumulation of Reactive Oxygen Species (ROS) within the vapour treated mycelia. ConclusionThe accumulated ROS interferes with ergosterol and chitin synthesis leading to the collapse of the plasma membrane and cell wall; consequently, extracellular leakage occurs.

Cooperative & competitive binding of anti-myosin tail antibodies revealed by super-resolution microscopy

The MF30 monoclonal antibody, which binds to the myosin subfragment-2 (S2), was found to increase the extent of myofibril shortening. Yet, previous observations found no effect of this antibody on actin sliding over myosin during in vitro motility assays with purified proteins in which myosin binding protein C (MyBPC) was absent. MF30 is hypothesized to enhance the availability of myosin heads (subfragment-1 or S1) to bind actin by destabilizing the myosin S2 coiled-coil and sterically blocking S2 from binding S1. The mechanism of action likely includes MF30's substantial size, thereby inhibiting S1 heads and MyBPC from binding S2. Hypothetically, MF30 should enhance the ON state of myosin, thereby increasing muscle contraction. Our findings indicate that MF30 binds preferentially to the unfolded heavy chains of S2, displaying positive cooperativity. However, the dose-response curve of MF30's enhancement of myofibril shortening did not suggest complex interactions with S2. Single, double, and triple-stained myofibrils with increasing amounts of antibodies against myosin rods indicate a possible competition with MyBPC. Additional assays revealed decreased fluorescence intensity at the C-zone (central zone in the sarcomere, where MyBPC is located), where MyBPC may inhibit MF30 binding. Another monoclonal antibody named MF20, which binds to the light meromyosin (LMM) without affecting myofibril contraction, showed less reduction in fluorescence intensity at the C-zone in expansion microscopy than MF30. Expansion microscopy images of myofibrils labeled with MF20 revealed labeling of the A-band (anisotropic band) and a slight reduction in the labeling at the C-zone. The staining pattern obtained from the expansion microscopy image was consistent with images from photolocalization microscopy which required the synthesis of unique photoactivatable quantum dots, and Zeiss Airyscan imaging as well as alternative expansion microscopy digestion methods. Consistent with the hypothesis that MF30 competes with MyBPC binding to S2, cardiac tissue from MyBPC knockout mice was stained more intensely, especially in the C-zone, by MF30 compared to the wild type.

Effects of Cascading Optical Processes: Part III. Impacts on Spectroscopic Measurements of Fluorescent Samples.

Cascading optical processes involve sequential photon-matter interactions triggered by the same individual excitation photons. Parts I and II of this series explored cascading optical processes in scattering-only solutions (Part I) and solutions with light scatterers and absorbers but no emitters (Part II). The current work (Part III) focuses on the effects of cascading optical processes on spectroscopic measurements of fluorescent samples. Four types of samples were examined: (1) eosin Y (EOY), an absorber and emitter; (2) EOY mixed with plain polystyrene nanoparticles (PSNPs), which are pure scatterers; (3) EOY mixed with dyed PSNPs, which scatter and absorb light but do not emit; and (4) fluorescent PSNPs that are simultaneous light absorbers, scatterers, and emitters. Interference from both forward scattered and emitted photons can cause nonlinearity and spectral distortion in UV-vis extinction measurements. Sample absorption by nonfluorogenic chromophores reduces fluorescence intensity, while the effect of scattering on fluorophore fluorescence is complicated by several competing factors. A revised first-principles model is developed for correlating the experimental fluorescence intensity with the sample absorbance in solutions containing both scatterers and absorbers. The optical properties of fluorescent PSNPs of three different sizes were systematically investigated by using integrating-sphere-assisted resonance synchronous spectroscopy, linearly polarized resonance synchronous spectroscopy, UV-vis, and fluorescence spectroscopy. The insights and methodology provided in this work should help improve the reliability of spectroscopic analyses of fluorescent samples, where the interplay among light absorption, scattering, and emission can be complex.

Effects of epigallocatechin gallate, caffeine, and their combination on fat accumulation in high-glucose diet-fed Caenorhabditis elegans.

Epigallocatechin gallate (EGCG) and caffeine are inevitable to be ingested together in the process of drinking green tea. This study used Caenorhabditis elegans as an organism model to examine whether the binding of EGCG and caffeine could influence the fat-reduction effect. The results revealed that EGCG significantly reduced the Nile Red fluorescence intensity and the triglyceride/protein ratio of the C. elegans obesity model by 14.7% and 16.5%, respectively, while the effect of caffeine was not significant. Moreover, the degree of reduction in fluorescence intensity and triglyceride/protein ratio by EGCG+caffeine was comparable to that of EGCG. In the exploration of underlying mechanism, we found that EGCG and EGCG+caffeine treatments had no influence on food intake and energy expenditure of C. elegans. Their fat-reduction effects were dependent on the regulation of lipogenesis, as shown by the decreased expression of the sbp-1, fat-7, and daf-16 genes.

Fluorescence microscopy-based sensitive method to quantify dopaminergic neurodegeneration in a Drosophila model of Parkinson's disease.

Death of dopaminergic (DAergic) neurons in the substantia nigra pars compacta of the human brain is the characteristic pathological feature of Parkinson's disease (PD). On exposure to neurotoxicants, Drosophila too exhibits mobility defects and diminished levels of brain dopamine. In the fly model of sporadic PD, our laboratory has demonstrated that there is no loss of DAergic neuronal number, however, a significant reduction in fluorescence intensity (FI) of secondary antibodies that target the primary antibody-anti-tyrosine hydroxylase (TH). Here, we present a sensitive, economical, and repeatable assay to characterize neurodegeneration based on the quantification of FI of the secondary antibody. As the intensity of fluorescence correlates with the amount of TH synthesis, its reduction under PD conditions denotes the depletion in the TH synthesis, suggesting DAergic neuronal dysfunction. Reduction in TH protein synthesis is further confirmed through Bio-Rad Stain-Free Western Blotting. Quantification of brain DA and its metabolites (DOPAC and HVA) using HPLC-ECD further demonstrated the depleted DA level and altered DA metabolism as evident from enhanced DA turnover rate. Together all these PD marker studies suggest that FI quantification is a refined and sensitive method to understand the early stages of DAergic neurodegeneration. FI quantification is performed using ZEN 2012 SP2, a licensed software from Carl Zeiss, Germany. This method will be of good use to biologists, as it with few modifications, can also be implemented to characterize the extent of degeneration of different cell types. Unlike the expensive and cumbersome confocal microscopy, the present method using fluorescence microscopy will be a feasible option for fund-constrained neurobiology laboratories in developing countries.