Search Results (20)

A rapid, colorimetric sensor for histamine detection is presented using citrate-stabilized gold nanoparticles enhanced with Cu²⁺ coordination. The sensing mechanism involves dual recognition: protonated histamine first adsorbs electrostatically onto AuNP surfaces at pH 5.5, followed by Cu²⁺-mediated coordination between imidazole rings that induces interparticle coupling, resulting in a characteristic shift of the localized surface plasmon resonance from 520 to 620 nm. The optical response, measured as the absorbance ratio A₆₂₀/A₅₂₀, exhibits excellent linearity over the range of 1.25–10 μM with a detection limit of 0.95 μM and total assay time under 30 min. The dual-recognition mechanism provides high selectivity for histamine over structural analogs, including L-histidine, imidazole, and L-lysine. The metal ion-mediated colorimetric approach described here achieves sub-micromolar sensitivity in simple buffer solutions, which is comparable to the histamine level used in in vitro cell assays and food-related studies. Thus, the present system is best viewed as a mechanistic model that can inform the design of future biosensing and analytical methods, rather than as a fully optimized sensor for direct clinical measurements in complex biofluids. Full article

The presence of impurities such as Ca, Mg, and Al during the precipitation of rare earths (REs) using ammonium bicarbonate directly affects product purity. It is necessary to optimize precipitation methods and conditions to improve the separation efficiency between REs and impurities. In this study, RE (La and Ce) ions were precipitated using ammonium bicarbonate solution, and the separation efficiency of REs from Al, Fe, Ca, and Mg ions was investigated with or without the addition of triammonium citrate (TAC). The results showed that as long as the precipitation yield of REs was controlled below 94%, Ca and Mg ions would not enter the precipitation in the absence of other impurities, and the purity of the obtained rare earth oxides (RE₂O₃) was close to 100%. The presence of Al and Fe impurities would reduce the separation efficiency of REs from Ca and Mg. Therefore, Al and Fe must be separated before the precipitation of REs. First, Fe was completely precipitated by controlling the pH value to 4.12. Then, by filtering out the isolation and adjusting the pH value to 4.6, approximately 84% of Al³⁺ was precipitated, with a loss of REs of about 6%. Finally, the pH value was increased to 6.43, and REs were completely precipitated, yielding rare earth carbonate. The RE₂O₃ purity of its calcination product was 97.8% with Al and Mg contents of 1.05% and 0.21%, respectively, and no Ca or Fe was detected. This indicated that Mg can enter the product by co-precipitation with Al. To address this, a small amount of TAC was added during the pre-removal of Fe and Al to facilitate the complete removal of Al. By controlling the precipitation yield of REs at 94%, the purity of the final RE₂O₃ reached 99.6% with an Al content of 0.09%. Furthermore, using a continuous precipitation crystallization method, RE₂O₃ purity can be achieved at 99.8% with an Al content of 0.06%. Full article

This study aims to investigate the vibrational, structural, morphological, optical, and magnetic properties of Zn_1−xCo_xO with 0.00 ≤ x ≤ 0.05 prepared by the sol–gel method via an amorphous citrate precursor. FTIR spectroscopy was used to follow the thermal decomposition process of the ZnO precursor, identifying acetate zinc as the intermediate main component. XRD and FTIR-ATR techniques showed only the single wurtzite crystalline phase with the presence of oxygen deficiency and/or vacancies, and secondary phases were not detected. SEM micrographs showed agglomerated particles of irregular shape and size with a high distribution and evidenced particles of nanometric size with a morphology change for x = 0.05. We detected high–spin Co²⁺ ions located in the tetrahedral core and pseudo–octahedral surface sites, substituting Zn²⁺ ions. The energy band gap of the ZnO semiconductor decreased gradually when the Co doping concentration was increased. M vs. H for undoped ZnO nanoparticles exhibited a diamagnetic signal overlapped with a weak ferromagnetic signal at room temperature. Interestingly, temperature-dependent magnetization showed superparamagnetic behavior with a blocked state in the low temperature range. The Co–doped ZnO samples evidenced a weak ferromagnetic signal and a paramagnetic component, which increased with x. The saturation magnetization increased until x = 0.03 and then decreased for x = 0.05, while the coercive field gradually decreased. Full article

Surface-enhanced Raman scattering (SERS) is highly dependent on the adsorption of target molecules onto metallic surfaces, such as colloidal metallic nanoparticles. The selection of suitable substrates is crucial for optimizing SERS performance. Herein, we investigated the dependence of two pesticide SERS signals, thiabendazole (TBZ) and carbendazim (MBC), on both Ag nanoparticles (reduced by hydroxylamine—AgH or citrate—AgCT) and the aggregation conditions induced by adding different salts (NaCl, KCl or KNO₃). In addition to SERS experiments, in order to assess the induced aggregation of the Ag nanoparticles, UV-Vis absorption spectroscopy, dynamic light scattering (DLS) and zeta potential were employed. For AgH, the use of salts did not yield the greatest effect in the presence of TBZ, as only with the pesticide was it possible to achieve the highest aggregation and greater intensity of the SERS signal. In contrast, with the MBC pesticide, the KNO₃ salt promoted the greatest aggregation state and was crucial for obtaining the most amplified SERS signal. The thicker coating layer of AgCT prevented the adsorption of both pesticides on the surface of the nanoparticles, which was achievable using salts containing Cl⁻ ions. Additionally, to obtain the SERS signal of MBC with AgCT, besides the presence of chlorinated salts, other adjustments were necessary, such as changing both the pH of the medium (from pH 5.8 to pH 8, for which MBC is in its neutral form) and the laser lines (from 785 to 514.5 nm). These findings demonstrated that although the pesticide molecules belong to the same chemical functional group, their detection was strongly influenced by the surface of the silver nanoparticles and the salts added. This highlights the specific nuances in detection depending on the method of Ag synthesis and the nature of the aggregating agents used. Full article

Growth-retarded yaks are of a high proportion on the Tibetan plateau and reduce the economic income of farmers. Our previous studies discovered a maldevelopment in the ruminal epithelium of growth-retarded yaks, but the molecular mechanisms are still unclear. This study aimed to reveal how the proteomic profile in the ruminal epithelium contributed to the growth retardation of yaks. The proteome of the ruminal epithelium was detected using a high-resolution mass spectrometer. There were 52 proteins significantly differently expressed between the ruminal epithelium of growth-retarded yaks and growth-normal yaks, with 32 downregulated and 20 upregulated in growth-retarded yaks. Functional analysis showed the differently expressed proteins involved in the synthesis and degradation of ketone bodies (p = 0.012), propanoate metabolism (p = 0.018), pyruvate metabolism (p = 0.020), and mineral absorption (p = 0.024). The protein expressions of SLC26A3 and FTH1, enriched in the mineral absorption, were significantly downregulated in growth-retarded yaks. The key enzymes ACAT2 and HMGCS2 enriched in ketone bodies synthesis and key enzyme PCCA enriched in propanoate metabolism had lower protein expressions in the ruminal epithelium of growth-retarded yaks. The ATP concentration and relative mitochondrial DNA copy number in the ruminal epithelium of growth-normal yaks were dramatically higher than those of growth-retarded yaks (p < 0.05). The activities of citrate synthase (CS), the α-ketoglutarate dehydrogenase complex (α-KGDHC), isocitrate dehydrogenase (ICD) in the tricarboxylic acid cycle (TCA), and the mitochondrial respiratory chain complex (MRCC) were significantly decreased in ruminal epithelium of growth-retarded yaks compared to growth-normal yaks (p < 0.05). The mRNA expressions of COQ9, COX4, and LDHA, which are the encoding genes in MRCC I, IV and anaerobic respiration, were also significantly decreased in the ruminal epithelium of growth-retarded yaks (p < 0.05). Correlation analysis revealed that the average daily gain (ADG) was significantly positively correlated to the relative mitochondrial DNA copy number (p < 0.01, r = 0.772) and ATP concentration (p < 0.01, r = 0.728) in the ruminal epithelium, respectively. The ruminal weight was positively correlated to the relative mitochondrial DNA copy number (p < 0.05, r = 0.631) and ATP concentration in ruminal epithelium (p < 0.01, r = 0.957), respectively. The ruminal papillae had a significant positive correlation with ATP concentration in ruminal epithelium (p < 0.01, r = 0.770). These results suggested that growth-retarded yaks had a lower VFA metabolism, ketone bodies synthesis, ion absorption, and ATP synthesis in the ruminal epithelium; it also indicated that the growth retardation of yaks is related to the obstruction of cellular ATP synthesis in rumen epithelial cells. Full article

Here we report the synthesis of ultrasmall (2 nm in diameter) ATP-coated gold nanoparticles, ATP-NPs. ATP-NPs can be enlarged in a predictable manner by the surface-catalyzed reduction of gold ions with ascorbate, yielding uniform gold nanoparticles ranging in size from 2 to 5 nm in diameter. Using atomic force microscopy (AFM), we demonstrate that ATP-NPs can efficiently and selectively bind to a short non-hybridized 5A/5A region (composed of a 5A-nucleotide on each strand of the double helix) inserted into a circular double-stranded plasmid, Puc19. Neither small (1.4 nm in diameter) commercially available nanoparticles nor 5 nm citrate-protected ones are capable of binding to the plasmid. The unique ability to specifically target DNA regions characterized by local structural alterations of the double helix can pave the way for applications of the particles in the detection of genomic DNA regions containing mismatches and mutations that are common for cancer cells. Full article

A new sensing material, Pt(II)-5-(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin (Pt(II)-COOH-TPOPP), was synthesized and characterized. Polymeric membranes containing the porphyrin and three different plasticizers were used as an electroactive material for a new anion-selective sensor. The best composition of the membrane was the one plasticized with dioctylsebacate (DOS), the obtained sensor being citrate-selective in a linear range of 5 × 10⁻⁷–1 × 10⁻¹ M citrate. The slope was Nernstian (19.73 mV/decade) with good selectivity towards a number of interfering anions and a lifetime of five weeks. Full article

The surface tailored metal oxide nanostructures for the development of non-enzymatic sensors are highly demanded, but it is a big task due to the wide range of complexities during the growth process. The presented study focused on the surface modification of the heterogeneous morphology of cobalt oxide (Co₃O₄) prepared by the hydrothermal method. Further surface modification was conducted with the use of sodium citrate as a reducing and surface modifying agent for the Co₃O₄ nanostructures through the high density of oxygenated terminal groups from the citrate ions. The citrate ions enabled a significant surface modification of the Co₃O₄ nanostructures, which further improved the electrochemical properties of the Co₃O₄ material toward the design of the non-enzymatic ascorbic acid sensor in a phosphate buffer solution of pH 7.4. The morphology and crystal arrays of the Co₃O₄ nanostructures were studied by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. These physical characterizations showed the highly tailored surface features of Co₃O₄ nanostructures and a significant impact on the crystal properties. The electrochemical activity of Co₃O₄ was studied by chronoamperometry, linear sweep voltammetry, and cyclic voltammetry (CV) for the detection of ascorbic acid. The linear range of the proposed sensor was measured from 0.5 mM to 6.5 mM and a low limit of detection of 0.001 mM was also estimated. The presented Co₃O₄ nanostructures exhibited significant surface roughness and surface area, consequently playing a vital role toward the selective, sensitive, and stable detection of ascorbic acid. The use of a low cost surface modifying agent such as sodium citrate could be of great interest for the surface roughness and high surface area of nanostructured materials for the improved electrochemical properties for the biomedical, energy storage, and conversion systems. Full article

In the proposed method, microwave-assist heating and AgNO3/trisodium citrate were used to create the polyvinylpyrrolidone-capped silver nanoparticles (PVP-AgNPs) sensor. This sensor had a peroxidase-like activity that could catalytically oxidize O-phenylenediamine (OPD, colourless) into 2,3-diaminophenazine (ox-OPD, greenish-yellow colour) in the presence of H₂O₂, otherwise, in the presence of Hg²⁺, this pass has been effectively inhibited. The degree of colour fading was directly correlated with Hg²⁺ concentration. These results indicated the selectivity of Hg²⁺ ions toward PVP-AgNPs after establishing the PVP-AgNPs/OPD/H₂O₂ system. This selectivity was proved by the negative results obtained from other mon-, di-, and trivalent ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Co²⁺, Ni²⁺, Cd²⁺, and Cr³⁺, instead of Hg²⁺. Consequently, a reliable, selective, and eco-effective spectrophotometric approach was designed for the detection of Hg²⁺ in various types of water samples. LOD was extended to lower than 0.1 µM, and a fading in the obtained colour was shown by the naked eye at a concentration higher than 1.5 µM of Hg²⁺. The elemental details for preparing the used PVP-AgNPs, such as particle size, morphology, polydispersity index (PdI), and their UV-visible spectrum, were identified by SEM technique, TEM, UV-visible spectrophotometer, and zeta-sizer device. Thus, the peroxidase mimicking the activity of OPD/H₂O₂ was confirmed by a fluorescence technique. The greenness profile of this work was confirmed after applying a reported assessment tool. Full article

Urine citrate analysis is relevant in the screening and monitoring of patients with calcium nephrolithiasis. A sensitive, fast, easy, and low-maintenance ion chromatographic (IC) method with conductivity detection for the analysis of urine citrate is developed and validated. Its application on true samples is also reported. Sample urine is diluted with a water solution containing internal standard (IS) before the chromatographic assay. The isocratic chromatographic run time is twenty-five minutes, using sodium hydroxide aqueous solution as the mobile phase. The method is fully validated as a quantitative method to objectively demonstrate its applicability for the intended use. The analytical response is linear in the 0.08–10.4 mmol/L concentration range. Precision and accuracy studies carried out on spiked urine and internal quality control samples reveal an imprecision CV% lower than 11% and an accuracy between 85 and 103%. The stability of citrate in urine samples is also evaluated. An easy, rapid, and low-maintenance, cost-effective IC method for urinary citrate determination is developed and validated. Internal standardization improves reliability and precision. The method has been currently used in our laboratory over recent years to analyze more than 1000 samples per year. Full article

Background: Nanosilver possesses antiviral, antibacterial, anti-inflammatory, anti-angiogenesis, antiplatelet, and anticancer properties. The development of disinfectants, inactivated vaccines, and combined etiotropic and immunomodulation therapy against respiratory viral infections, including COVID-19, remains urgent. Aim: Our goal was to determine the SARS-CoV-2 molecular targets (genomic RNA and the structural virion proteins S and N) for silver-containing nanomaterials. Methods: SARS-CoV-2 gene cloning, purification of S2 and N recombinant proteins, viral RNA isolation from patients’ blood samples, reverse transcription with quantitative real-time PCR ((RT)²-PCR), ELISA, and multiplex immunofluorescent analysis with magnetic beads (xMAP) for detection of 17 inflammation markers. Results: Fluorescent Ag nanoclusters (NCs) less than 2 nm with a few recovered silver atoms, citrate coated Ag nanoparticles (NPs) with diameters of 20–120 nm, and nanoconjugates of 50–150 nm consisting of Ag NPs with different protein envelopes were constructed from AgNO₃ and analyzed by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), ultraviolet-visible light absorption, and fluorescent spectroscopy. SARS-CoV-2 RNA isolated from COVID-19 patients’ blood samples was completely cleaved with the artificial RNase complex compound Li⁺[Ag⁺₂Cys₂⁻(OH⁻)₂(NH₃)₂] (Ag-2S), whereas other Ag-containing materials provided partial RNA degradation only. Treatment of the SARS-CoV-2 S2 and N recombinant antigens with AgNO₃ and Ag NPs inhibited their binding with specific polyclonal antibodies, as shown by ELISA. Fluorescent Ag NCs with albumin or immunoglobulins, Ag-2S complex, and nanoconjugates of Ag NPs with protein shells had no effect on the interaction between coronavirus recombinant antigens and antibodies. Reduced production of a majority of the 17 inflammation biomarkers after treatment of three human cell lines with nanosilver was demonstrated by xMAP. Conclusion: The antiviral properties of the silver nanomaterials against SARS-CoV-2 coronavirus differed. The small-molecular-weight artificial RNase Ag-2S provided exhaustive RNA destruction but could not bind with the SARS-CoV-2 recombinant antigens. On the contrary, Ag⁺ ions and Ag NPs interacted with the SARS-CoV-2 recombinant antigens N and S but were less efficient at performing viral RNA cleavage. One should note that SARS-CoV-2 RNA was more stable than MS2 phage RNA. The isolated RNA of both the MS2 phage and SARS-CoV-2 were more degradable than the MS2 phage and coronavirus particles in patients’ blood, due to the protection with structural proteins. To reduce the risk of the virus resistance, a combined treatment with Ag-2S and Ag NPs could be used. To prevent cytokine storm during the early stages of respiratory infections with RNA-containing viruses, nanoconjugates of Ag NPs with surface proteins could be recommended. Full article

We developed a method based on surface-enhanced Raman spectroscopy (SERS) and a sample pretreatment process for rapid, sensitive, reproducible, multiplexed, and low-cost detection of illegal drugs in urine. The abuse of new psychoactive substances (NPS) has become an increasingly serious problem in many countries. However, immunoassay-based screening kits for NPS are usually not available because of the lack of corresponding antibodies. SERS has a great potential for rapid detection of NPS because it can simultaneously detect multiple kinds of drugs without the use of antibodies. To achieve highly sensitive SERS detection of drugs, sodium bromide was first employed to induce the rapid formation of Ag nanoclusters by aggregating silver nanoparticles (AgNPs) in the extracted sample solution. SERS measurements were performed immediately after the sample pretreatment without incubation. The three-dimensional SERS hot spots were believed to form significantly within the nanoclusters, providing strong SERS enhancement effects. The displacement of citrate molecules on the surfaces of the AgNPs by bromide ions helped increase the adsorption of drug molecules, increasing their areal density. We demonstrated the simultaneous detection of two kinds of NPS, methcathinone and 4-methylmethcathinone, in urine at a concentration as low as 0.01 ppm. Full article

The disruption of iron homeostasis is an important factor in the loss of mitochondrial function in neural cells, leading to neurodegeneration. Here, we assessed the protective action of gossypitrin (Gos), a naturally occurring flavonoid, on iron-induced neuronal cell damage using mouse hippocampal HT-22 cells and mitochondria isolated from rat brains. Gos was able to rescue HT22 cells from the damage induced by 100 µM Fe(II)-citrate (EC₅₀ 8.6 µM). This protection was linked to the prevention of both iron-induced mitochondrial membrane potential dissipation and ATP depletion. In isolated mitochondria, Gos (50 µM) elicited an almost complete protection against iron-induced mitochondrial swelling, the loss of mitochondrial transmembrane potential and ATP depletion. Gos also prevented Fe(II)-citrate-induced mitochondrial lipid peroxidation with an IC₅₀ value (12.45 µM) that was about nine time lower than that for the tert-butylhydroperoxide-induced oxidation. Furthermore, the flavonoid was effective in inhibiting the degradation of both 15 and 1.5 mM 2-deoxyribose. It also decreased Fe(II) concentration with time, while increasing O₂ consumption rate, and impairing the reduction of Fe(III) by ascorbate. Gos–Fe(II) complexes were detected by UV-VIS and IR spectroscopies, with an apparent Gos-iron stoichiometry of 2:1. Results suggest that Gos does not generally act as a classical antioxidant, but it directly affects iron, by maintaining it in its ferric form after stimulating Fe(II) oxidation. Metal ions would therefore be unable to participate in a Fenton-type reaction and the lipid peroxidation propagation phase. Hence, Gos could be used to treat neuronal diseases associated with iron-induced oxidative stress and mitochondrial damage. Full article

The use of silver nanoparticles stabilized with citrate and polyvinylpyrrolidone as a sensor for aluminum ions determination is proposed in this paper. These non-functionalized and specific nanoparticles provide a highly selective and sensitive detection system for aluminum in acidic solutions. The synthesized nanoparticles were characterized by transmission electron microscopy. Surface plasmon band deconvolution analysis was applied to study the interaction between silver nanoparticles and aluminum ions in solution. The interaction band in the UV-visible region was used as an analytical signal for quantitation purposes. The proposed detection system offers an effective AND wide linearity range (0.1–10³ nM), specificity for Al(III) in THE presence of other metallic ions in solution, as well as high sensitivity (limit of detection = 40.5 nM). The proposed silver-nanoparticles-based sensor WAS successfully used for detecting Al(III) in real water samples. Full article

A colorimetric sensor, based on the synergistic coordination effect on a gold nanoparticle (AuNP) platform has been developed for the determination of creatinine. The sensor selects citrate stabilized AuNPs as a platform, polyethylene glycol (PEG) as a decorator, and Hg²⁺ as a linkage to form a colorimetric probe system (PEG/Hg²⁻–AuNPs). By forming hydrogen bond between the oxygen-containing functional groups of PEG and citrate ions on the surface of AuNPs, this probe shows good stability. PEG coordinated with Hg²⁺ synergistically and specifically on the surface of dispersed AuNPs, and the existence of creatinine could induce the aggregation of AuNPs with a corresponding color change and an obvious absorption peak shift within 5 min. This PEG/Hg²⁺–AuNPs probe towards creatinine shows high sensitivity, and a good linear relationship (R² = 0.9948) was obtained between A_{620–522 nm} and creatinine concentration, which can achieve the quantitative calculations of creatinine. The limit of detection (LOD) of this PEG/Hg2+–AuNPs probe was estimated to be 9.68 nM, lower than that of many other reported methods. Importantly, the sensitive probe can be successfully applied in a urine simulating fluid sample and a bovine serum sample. The unique synergistic coordination sensing mechanism applied in the designation of this probe further improves its high selectivity and specificity for the detection of creatinine. Thus, the proposed probe may give new inspirations for colorimetric detection of creatinine and other biomolecules. Full article