Search Results (370)

This study investigates the effect of precursor pH (1.3, 2, 4, 6, 8, and 10) on the synthesis of gold nanoparticles (AuNPs) via a green synthesis approach using an aqueous extract of green tea (Camellia sinensis) leaves. The formation of AuNPs was monitored using UV-vis spectrophotometry and confirmed using transmission electron microscopy (TEM). The results confirmed that the morphology and size of the AuNPs are strongly dependent on the pH of the reaction medium. Based on spectral features, the color of the colloids, and TEM analysis, the synthesized samples were classified into three groups. The first (pH 8 and 10) contained predominantly spherical nanoparticles with an average diameter of ~18 nm, the second (pH 1.3 and 2) contained different shaped nanoparticles (20–250 nm in diameter), and the third (pH 4 and 6) contained flower-like nanostructures with a mean diameter of ~60 nm. UV-vis analysis revealed good stability of all AuNP colloids, except at pH 1.3, where a significant decrease in absorbance intensity over time was observed. These findings confirm that tuning the precursor pH allows for controlled manipulation of nanoparticle morphology and stability in green synthesis systems. Full article

Canine distemper, a fatal and highly transmissible disease caused by the canine distemper virus (CDV), poses a major threat to the companion animal industry. An urgent need exists for a rapid, specific, and simple method for the detection of this disease in order to improve its prevention and control. In this research, two monoclonal antibodies (mAbs), 1D3E9 and 1H9B7, were prepared, both of which specifically recognize the nucleoprotein (N protein) of CDV, and an immunochromatographic assay for CDV detection was subsequently developed using these mAbs. The results showed that both mAbs belong to the IgG1 subclass with kappa light chains. 1D3E9 was found to recognize the linear epitope ⁴¹⁰AGPKQSQITFLH⁴²¹, while 1H9B7 targeted the epitope ⁴⁵⁰HFNDERFPGH⁴⁵⁹. The test strips exhibited high specificity and good stability for up to two months when stored at 4, 25, and 37 °C. The assay exhibited a sensitivity of 10^2.39 TCID₅₀/0.1 mL. When compared with RT-PCR for detecting CDV in clinical samples, the concordance rate was 91.67%. Thus, this method shows great potential for facilitating rapid on-site detection of CDV and could be highly beneficial from the viewpoint of disease surveillance and control. Full article

In this study, a simple, mild, and eco-friendly cold plasma-solution interaction method is employed to rapidly prepare gold colloids. Through modification with multi-walled carbon nanotubes (MWCNTs), a non-enzymatic glucose-sensing electrode material is successfully fabricated. The prepared electrode material is characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results show that compared with the chemically reduced AuNPs-C-MWCNTs, the plasma-prepared AuNPs-P-MWCNTs exhibits enhanced glucose catalytic performance with a higher sensitivity of 73 μA·mM⁻¹·cm⁻² (approximately 3.2 times that of AuNPs-C-MWCNTs), lower response time of 2.1 s, and ultra-low detection limit of 0.21 μM. It also demonstrates excellent selectivity, reproducibility (RSD = 4.37%), repeatability (RSD = 3.67%), and operational stability (RSD = 4.51%). This improvement can be attributed to the smaller particle size and better dispersion of plasma-derived AuNPs on the surface of MWCNTs. Furthermore, the AuNPs-P-MWCNTs surface is enriched with oxygen-containing functional groups, which is conducive to the enhancement of the hydrophilicity of the electrode surface. These synergistic effects facilitate the AuNPs-catalyzed glucose oxidation reaction, ultimately leading to superior glucose catalytic performance. Full article

In the process of chicken breeding, there has been a great deal of abuse of antibiotics. Antibiotics can enter the human body along with the chicken meat, comprising a possible risk to human health. In this paper, principal component analysis (PCA)–linear discriminant analysis (LDA) was chosen to classify neomycin (NEO) and chloramphenicol (CAP) residues in chicken meat. A total of 400 chicken meat samples were used for the classification, of which 268 samples and 132 samples were used as the training sets and the test sets, respectively. The experimental condition of SERS spectrum collection was optimized, including the use of a gold colloid and active agent, and an improvement in the adsorption time. The optimal measurement conditions for the SERS spectra were an adsorption time of 4 min and the use of a 14th-generation gold colloid as the enhanced substrate without a surfactant. For three groups of different spectral preprocessing methods, the classification accuracies of PCA-LDA models for test sets were 78.79% for baseline correction, 84.85% for the second derivative and 100% for the second derivative combined with baseline correction. LDA was used to establish a classification model to realize the quick determination of NEO and CAP residues in chicken meat by SERS. The results showed that the characteristic peaks at 546 and 666 cm⁻¹ could be used to distinguish NEO and CAP residues in chicken meat. The classification model based on PCA-LDA had higher classification accuracy, sensitivity and specificity using a second derivative combined with baseline correction as the spectral preprocessing method, which shows that the SERS method based on PCA-LDA could be used to perform the classification of NEO and CAP residues in chicken meat quickly and effectively. It also verified the feasibility of PCA-LDA to effectively classify chicken meat samples into four types. This research method could provide a reference for the measurement of such antibiotic residues in chicken meat in the future. Full article

Background/Objectives: Lactic acid bacteria produce biofilms in meat products that contribute to the products’ deterioration, reduction in quality, and shortened shelf life. Although LAB are generally considered benign, certain strains create slime and cause significant drops in pH. The study’s goal was to identify and characterize LAB strains from sausage products that are capable of biofilm formation, and to evaluate the inhibitory effects of E. bicyclis methanol extract, its ethyl acetate fraction, and phloroglucinol, as well as to synthesize AuNPs, and assess their efficacy in controlling biofilm formation. Methods: Slime or biofilm-producing LAB bacteria were isolated from commercial sausages and identified using 16S rRNA gene sequencing. Lactobacillus sakei S10, which can tolerate high salt concentrations and cold temperatures, was chosen as a representative strain. The isolates were subsequently tested for hemolytic activity, salt and temperature tolerance, and carbohydrate consumption patterns. To evaluate antibiofilm potential, marine-derived compounds from Eisenia bicyclis, such as phloroglucinol (PG), crude methanolic extracts, ethyl acetate fractions, and gold nanoparticle (AuNP) formulations, were tested in situ on sausage surfaces against L. sakei S10 and common pathogens (Pseudomonas aeruginosa and Staphylococcus aureus). The biofilm-inhibitory effects of the extracts, PG, and PG-AuNPs were estimated using the colony-counting method. Results: The PG-AuNPs had an average particle size of 98.74 nm and a zeta potential of −29.82 mV, indicating nanoscale dimensions and considerable colloidal stability. Structural analysis confirmed their spherical form and crystalline structure, as well as the presence of phenolic groups in both reduction and stabilization processes. Among the studied treatments, the PG and PG-AuNPs had the strongest antibiofilm activities, dramatically lowering biofilm biomass, particularly for P. aeruginosa and L. sakei S10. However, the inhibitory effects were less prominent in in situ conditions than in in vitro testing, highlighting the complexity of real food matrices. Conclusions: The results of this study indicate that polyphenolic compounds obtained from marine sources, particularly in nano-formulated forms, have a great deal of potential as natural antibiofilm products. Enhancing the microbiological safety of processed meat products and extending their shelf life could be accomplished through the application of these polyphenolic compounds in food packaging or surface treatments. Full article

This study aimed to develop monoclonal antibodies (mAbs) against the gD protein of FHV-1 for rapid and specific virus detection. The gD protein, a highly conserved part of the FHV-1 envelope, is crucial for viral entry into host cells, making it an ideal detection target. We immunized BALB/c mice with an mRNA vaccine encoding the gD gene, achieving a serum antibody titer of 1:140,000 after three immunizations. The mice were then boosted with recombinant gD protein. Through cell fusion and multiple subcloning rounds, we obtained five hybridoma cell lines (D7, E4, E9, E10, and E19) that stably secrete anti-gD protein mAbs. Characterization by indirect immunofluorescence and Western blot showed that mAbs D7 and E4 have high specificity and strong binding activity against FHV-1, detectable at 2 μg/mL. These mAbs provide specific tools for FHV-1 detection and a basis for developing rapid diagnostic methods using ELISA, colloidal gold, and other technologies. Full article

Gold nanoparticles (AuNPs) were synthesised using ultrasonic spray pyrolysis (USP) with the addition of polyvinylpyrrolidone (PVP) as a stabilising agent and subsequently dried via lyophilisation. The resulting dried AuNPs were redispersed in ethanol and homogenised to ensure uniform dispersion. This AuNP dispersion was then deposited onto a ceramic substrate—aluminum oxide (Al₂O₃)—using plasma jet printing. Comprehensive characterisation of the dispersion, AuNPs, and the resulting printed lines was performed using the following methods: inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS), measurements of dispersion viscosity and printed line roughness. ICP-OES confirmed consistent gold content in the AuNP dispersion, while the SEM and EDS analyses revealed predominantly spherical AuNPs with minimal aggregation and similar size distributions. TEM, SAED, and STEM/EDS confirmed that the crystalline structure and elemental composition of the AuNPs had diverse morphologies and strong gold signals. The UV-Vis, DLS, and zeta potential measurements indicated moderate colloidal stability, and thermogravimetric analysis (TGA) verified the AuNPs dispersion’s composition. The AuNP dispersion exhibited thixotropic behaviour favourable for printing applications, while confocal microscopy confirmed smooth, uniform printed traces, with an average surface line roughness of 1.65 µm. The successful use of plasma printing with the AuNP dispersion highlights its potential for functional material applications in electronics. Full article

Background/Objectives: The COVID-19 pandemic has highlighted the urgent need for rapid, accurate, and accessible diagnostic testing to effectively manage and contain the spread of SARS-CoV-2. RT-PCR is widely recognized as the gold standard for SARS-CoV-2 detection due to its high sensitivity and specificity. However, RT-PCR testing requires specialized laboratory equipment, highly trained personnel, and extended processing times, which limits its feasibility for large-scale screening and point-of-care applications. This study aims to systematically evaluate the diagnostic performance of RT-PCR and a colloidal gold immunochromatographic assay (GICA). Methods: By comparing these two methods, we seek to determine a GICA’s effectiveness as a complementary or alternative diagnostic tool, particularly in resource-limited settings and scenarios requiring rapid, large-scale testing. We assessed the following key clinical parameters: sensitivity, specificity, NPV, PPV, and accuracy. Additionally, we investigated the correlation between GICA signal intensity and RT-PCR Ct values using regression analysis, receiver operating characteristic curve analysis, and the calculated area under the curve. Results: Our findings indicate that while RT-PCR exhibits superior sensitivity, GICA results demonstrate a strong correlation with RT-PCR results and provide a rapid, cost-effective alternative for SARS-CoV-2 detection. Unlike RT-PCR, which requires extensive resources and prolonged turnaround times, a GICA delivers results within 20 min, making it a viable option for decentralized testing and real-time public health interventions. Conclusions: These results suggest that a GICA can serve as a complementary diagnostic tool alongside RT-PCR, particularly in resource-limited settings and high-throughput screening scenarios. By integrating GICAs into broader testing strategies, healthcare systems can enhance early detection efforts, improve accessibility to diagnostics, and strengthen pandemic response measures. Full article

Toxoplasma gondii is a globally significant zoonotic pathogen responsible for severe parasitic diseases in humans and animals. This study aimed to design, develop, and evaluate a novel immunochromatographic test (ICT) using a recombinant MIC2-MIC3 fusion protein (rMIC2-MIC3) for detecting specific antibodies against T. gondii. The ICT demonstrated exceptional sensitivity, capable of detecting T. gondii-specific antibodies in sera diluted up to 1:8. Specificity evaluation confirmed no cross-reactivity with antibodies against other parasites, such as Neospora caninum, Cryptosporidium suis, Eimeria tenella, and Sarcocystis tenella. Stability tests revealed the test strips maintained full functionality after 12 weeks of storage at 24 °C. The coincidence rate of the colloidal gold test strips prepared in this study with a commercial ELISA kit was 94.59%. Comparisons with advanced serodiagnostic tools, such as chimeric antigen-based ELISAs and recombinant protein diagnostics, further highlighted its robustness and applicability. These findings underscore the potential of the rMIC2-MIC3-based ICT as a reliable, economical, and accessible diagnostic tool for toxoplasmosis in veterinary and human medicine. Full article

The optical detection of thioacetamide was investigated using a metalated porphyrin, Mn(III)-5,10,15,20-tetrakis-(3,4-dimethoxyphenyl)-21H,23H-porphyrin chloride (Mn-3,4-diMeOPP), a gold colloid solution (AuNPs), and a complex formed between them (Mn-3,4-diMeOPP–AuNPs) in order to select the most sensitive material and to achieve complementarity between methods. Mn-3,4-diMeOPP, AuNPs, and their complex were synthesized and characterized by means of UV–Vis, FT-IR spectrometry, and AFM investigations. It could be concluded that Mn-3,4-diMeOPP could detect/quantify thioacetamide (TAA) in the range 3.13 × 10⁻⁸ M–7.67 × 10⁻⁷ M in a linear fashion, with a 99.85% confidence coefficient. The gold colloidal particles alone could detect TAA in an extremely narrow concentration domain of 2–9.8 × 10⁻⁷ M, slightly complementary with that of Mn-3,4-diMeOPP. The complex between Mn-3,4-diMeOPP and gold colloid proved to be able to quantify TAA in the trace domain with concentrations of 1.99 × 10⁻⁸ M–1.76 × 10⁻⁷ M in a polynomial fashion, with the method being more difficult. A potential mechanism for TAA detection based on Mn-3,4-diMeOPP is discussed based on computational modeling. The distorted porphyrin conformation and its electronic configuration favor the generation of a grid of electrostatic interactions between porphyrin and TAA. Full article

Gold nanoparticles stabilized with polyamidoamine dendrimers are one of the potential candidates for use as a contrast agent in computed tomography and a drug delivery agent. This work demonstrates a rapid, two-step synthesis of such complexes, which are size-stable for up to 18 months. The first step of the synthesis involves a short sonication of gold (III) chloride hydrate with polyamidoamine dendrimers of the fourth generation, while the second step uses microwaves to reduce gold (III) chloride hydrate with sodium citrate. The developed synthesis method enables rapid production of spherical and monodisperse gold nanoparticles stabilized with polyamidoamine dendrimers. Physicochemical characterization of the gold nanoparticle-polyamidoamine dendrimers complexes was performed using ultraviolet-visible spectroscopy, dynamic light scattering technique, infrared spectroscopy, atomic force microscopy, and transmission electron microscopy. The toxicity of synthesized complexes on the breast cancer MCF-7 cell line has been studied using the tetrazolium salt reduction test. The produced gold nanoparticles revealed lower toxicity levels on the MCF-7 cell line after 18 months from synthesis compared with newly synthesized colloids. Synthesized gold nanoparticles stabilized with dendrimers and commercially available gold nanoparticles stabilized with sodium citrate show similar toxicity levels on breast cancer cells. Full article

E. coli O157:H7 contamination in food and the environment poses a serious threat to human health. Rapid and sensitive identification of foodborne pathogens remains challenging. Here, we prepared tungsten disulfide (WS₂)–Au nanocomposites coupled with the Raman signal molecule 5,5′-dithio-bis-(2-nitrobenzoic acid) (DTNB) and antibodies to replace the conventional colloidal gold nanoparticles and applied SERS-active nanotags in the SERS-ICA method for highly sensitive detection of E. coli O157:H7. The large surface area and numerous effective SERS hotspots of WS₂-Au nanotags provide superior SERS signals. Under optimized conditions, this ICA achieves the quantitative detection of E. coli O157:H7 in a broad linear range of 8 × 10²–8 × 10⁷ CFU/mL and at a low detection limit of 175 CFU/mL. In addition, the test strip indicates high specificity for E. coli O157:H7 identification, favorable reproducibility, and shows good accuracy in the detection of actual food samples, such as milk and pork. The proposed assay can be used for rapid qualitative and quantitative detection of E. coli O157:H7 and has great potential for field application. Full article

The clinical characteristics of multidrug-resistant tuberculosis (MDR-TB) patients with concurrent nontuberculous mycobacterial (NTM) infection present significant challenges to treatment. This study investigated the clinical characteristics of MDR-TB patients with concurrent NTM infection during treatment. A retrospective cohort study was conducted to collect the clinical data of MDR-TB patients who initiated treatment between January 2020 and December 2022. A total of 389 patients were analyzed, among which 111 patients who were lost to follow-up and 56 patients who missed etiological examination of tuberculosis during the visit period were excluded. A total of 222 patients with complete data were included in this study. The species identification method primarily employed molecular biology techniques, specifically the DNA microarray method and/or MPB64 antigen detection using the colloidal gold method. Patients whose sputum or bronchoalveolar lavage fluid cultures were positive and who were identified at least once as having NTM or as MPB64 negative were included in this study. Imaging data, comorbidities, pre-treatment infection, and nutritional indicators were analyzed during treatment. Among the 222 MDR-TB patients, no concurrent NTM cases were identified at the beginning of treatment. However, 19 cases (8.56%) were presumed to be NTM-positive during treatment, which appeared during anti-tuberculosis treatment from 2 to 12 months, averaging 6 (3, 12) months. Thirteen patients were only tested for MPB64, with five having two negative MPB64 tests. The symptoms of NTM-positive patients varied, and imaging findings were similar to those of MDR-TB but did not worsen. The emergence of presumed NTM-positive cases (8.56%) among MDR-TB patients during treatment highlights the need for monitoring, as symptoms and imaging findings may mimic MDR-TB without worsening. Early and repeated testing, including methods beyond MPB64, may be useful for more accurate diagnosis and tailored management. Full article

Controlling the stability of colloidal nanoparticles in multicomponent systems is crucial for advancing formulations and separation processes. This study investigates the selective agglomeration approach for binary colloidal mixtures, providing both fundamental insights into stability/agglomeration mechanisms and a scalable separation strategy. First, we established a binary model system comprising gold nanoparticles (Au NPs) and ZnS quantum dots (QDs) to assess interparticle interactions. UV-visible spectroscopy revealed that impurities released from ZnS QDs, particularly thiol-based ligands and unbound Zn ions, triggered the aggregation of Au NPs depending on their surface stabilizers. Functionalization of Au NPs with bis(p-sulfonatophenyl) phenylphosphine (BSPP) significantly enhanced colloidal stability, with unpurified BSPP-functionalized Au NPs exhibiting superior resistance to agglomeration. Building on these insights, we applied selective agglomeration to separate a complex colloidal system consisting of InP/ZnS core–shell QDs and ZnS byproducts, a critical challenge in QD synthesis that is particularly relevant for post-processing of samples that originate from large-scale flow synthesis. By systematically tuning the ethanol concentration as a poor solvent, we successfully achieved composition-dependent fractionation. Optical and spectroscopic analyses confirmed that coarse fractions were enriched in InP/ZnS QDs, while fines fractions mainly contained pure ZnS QDs, with absorption peaks at 605 nm and 290 nm, respectively. Photoluminescence spectra further demonstrated a redshift in the coarse fractions, correlating with an increase in particle size. These results underscore the potential of selective agglomeration as a scalable, post-synthesis classification method, offering a framework for controlling stability and advancing post-synthesis separation strategies in colloidal multicomponent systems. Full article

Actinobacillus pleuropneumoniae (APP) is a bacterial pathogen causing porcine pleuropneumonia, causing great economic loss to the global pig industry. Although natural apxIV contributes to the prevention and control of porcine pleuropneumonia, its isolation poses a great challenge, and recombinant soluble apxIV proteins tend to carry large molecular weight tags. The traditional serologic methods tend not to accurately detect the apxIV-partially deleted vaccine (GDV). In this study, we screened the soluble protein apxIVA N2 (756 bp) from six apxIV-truncated proteins and applied it to the enzyme-linked immunosorbent assay (ELISA) and colloidal gold immunochromatographic strip for detecting the samples vaccinated with APP GDV. The results indicate that N2 was close to the natural apxIV protein in terms of structure and function as it only contained a single His (0.86 kDa) tag and a single S (2 kDa) tag. Among the six candidate proteins, N2 exhibited the best performance in distinguishing APP-infected samples from those vaccinated with the APP GDV. Both ELISA and colloidal gold immunochromatographic strips based on this protein exhibited an excellent performance in detecting and distinguishing wild-strain-infected samples from those vaccinated with the subunit vaccine or the GDV. In addition, three monoclonal antibodies against different antigenic epitopes were identified using these truncated proteins. Our studies are of great significance for further research on APP, the differential diagnosis of wild strains and vaccine strains, and pig control breeding, exhibiting a broad application prospect in the on-site diagnosis of APP, particularly in remote areas lacking detection instruments and professionals. Full article