Search Results (169)

Hybrid nanomaterials that integrate surface functionality, colloidal stability, and efficient electron-transfer pathways are highly attractive for improving electrochemical sensing performance. Herein, we report the fabrication and evaluation of polyethyleneimine-functionalized gallium nitride nanoparticles (GaN) decorated with gold nanoparticles (GaN-PEI-Au) as a tunable electrode modifier for enhanced differential pulse voltammetry (DPV) detection of erythromycin. Branched polyethyleneimine was employed as a multifunctional interfacial layer to stabilize GaN dispersions, introduce amine-rich surface chemistry, and enable in situ gold nanoparticle formation at the GaN-PEI. The optimized GaN-PEI-Au material exhibited high colloidal stability, a characteristic Au localized surface plasmon resonance in the ~520–525 nm range, and well-defined Au nanoparticles attached to the GaN surface. When applied as an electrode coating, GaN-PEI-Au significantly enhanced the erythromycin oxidation response compared to bare Au and GaN-PEI interfaces, consistent with synergistic increases in electroactive surface area and interfacial charge-transfer efficiency. Under optimized DPV conditions, GaN-PEI-Au-modified electrodes enabled quantitative erythromycin determination with a linear range of 5 nM–2 µM (R² = 0.990), sensitivity of 1.32 × 10⁻³ µA nM⁻¹, and a limit of detection of 52.5 nM, while maintaining stable baseline behavior during repeated scans. The reported GaN-PEI-Au nanocomposites represent a robust platform for sensitive electrochemical detection of pharmaceutical compounds. Full article

Diflubenzuron (DFB), a benzoylurea insecticide widely used in fruits, vegetables, cereals, and edible fungi, is increasingly detected in food. It has been linked to endocrine disruption, hematological effects, developmental toxicity, DNA damage, and ecological risks in aquatic organisms. These concerns, together with strict maximum residue limits, highlight the need for rapid, field-deployable detection methods. Herein, we developed a quantitative colloidal gold lateral-flow immunoassay for rapid DFB detection within 10 min. The optimized assay achieved a limit of detection (LOD) of 0.02 ng mL⁻¹, a limit of quantification (LOQ) of 0.067 ng mL⁻¹, and a linear range of 0.07–100 ng mL⁻¹ (R² = 0.9998), with high selectivity. Validation in eight food matrices (milk, chicken, mushrooms, pear, Chinese cabbage, rice, dried chili, and peanut) showed recoveries of 97.6–110.0% with RSDs of 2.1–4.9%. Results were consistent with LC-MS analysis, demonstrating that this assay provides a sensitive, practical, and rapid tool for screening DFB residues. Full article

Conventional immunochromatographic assays (ICAs) face limitations in sensitivity and dynamic range, hindering their application in on-site, class-specific screening of sulfonylurea (SU) adulteration in functional foods. To address this, a signal amplification strategy was developed by engineering high-density platinum nanozymes on a mesoporous metal–organic framework (PCN-224). The mesoporous architecture of PCN-224 facilitated high-density and stable loading of catalytically active Pt sites. The established PCN-224@Pt-based ICA achieved detection limits of 0.52–7.94 μg/kg in tea and 0.69–7.02 μg/kg in capsules, with linear ranges of 1.69–513.01 μg/kg and 2.05–716.47 μg/kg, respectively. Compared with traditional colloidal gold immunochromatographic assays (CG-ICAs), sensitivity was improved by up to 57-fold, while the linear detection range was expanded by over 5-fold relative to the previously reported PCN-224@PDA- ICA. The method demonstrated recovery rates of 81.8–119.8% and coefficients of variation between 2.5% and 11.4%. Validation against LC-MS/MS using 20 real samples showed excellent agreement (R² > 0.99). This work not only provides a sensitive and rapid tool for the surveillance of SU adulteration in functional foods but also establishes a generalizable nanozyme design strategy applicable to enhancing the performance of a wide range of ICA-based detection platforms. Full article

Conventional colorimetric lateral flow immunoassays (LFIAs) often suffer from insufficient sensitivity for detecting trace low-molecular-weight contaminants like mycotoxins. The development of colorimetric probes with a high molar extinction coefficient is therefore critical for enhancing detection performance. Although silver nanoparticles (AgNPs) exhibit an extremely high molar extinction coefficient, their practical application in LFIA is hindered by inherent chemical instability and suboptimal visual contrast. To address these limitations, we have engineered robust and high-performance polydopamine-functionalized AgNPs (Ag@PDA NPs) as advanced LFIA signal probes, which were successfully used for detecting aflatoxin B₁ (AFB₁) in maize. The multifunctional PDA nanoshell effectively shields the Ag core from oxidation and other destabilizing factors, ensuring superior long-term stability and significantly enhancing colorimetric contrast. Moreover, it improves the colloidal hydrophilicity, enabling faster and more uniform migration kinetics along the test strip. Leveraging these engineered properties, the developed assay achieved a limit of detection (LOD) of 0.23 ng mL⁻¹ for AFB₁ in buffer, representing a remarkable 2.17-fold sensitivity enhancement over conventional colloidal gold-based LFIAs. Validation in spiked maize samples confirmed high reliability, with recoveries ranging from 95.70% to 119.28% and precision (inter-/intra-assay CVs) below 13.03%. Full article

Pseudomonas aeruginosa is an important waterborne pathogen that is harmful to food safety and human health. Therefore, the detection of Pseudomonas aeruginosa has become an essential item in food sampling. This article constructs a fluorescent aptamer sensor based on Tb-MOFs, using Tb-MOFs as the fluorescence signal source, colloidal gold (AuNPs) as the signal conversion switch, and aptamers as the target recognition element, to establish a quantitative detection method for Pseudomonas aeruginosa. The constructed sensor exhibits a good linear relationship within the concentration range of Pseudomonas aeruginosa from 1 to 10⁶ CFU/mL, with a detection limit of 0.63 CFU/mL. Moreover, the sensor was also applied to the detection of Pseudomonas aeruginosa in actual samples of bottled drinking water and orange juice. The fluorescent aptasensor based on Tb-MOFs provides a rapid and sensitive new sensing method for the detection of Pseudomonas aeruginosa in food. Full article

The fungal pathogen Metschnikowia bicuspidata causes “milky disease” in the Chinese mitten crab (Eriocheir sinensis), which poses substantial challenges to sustainable aquaculture development considering the current lack of effective treatment interventions. To address this issue, in laboratory validation, we developed two rapid recombinase polymerase amplification (RPA) detection methods for M. bicuspidata in E. sinensis targeting the histone acetyltransferase B-type subunit 2 gene (HAT-B2): an electrophoretic assay (RPA-AGE) and a colloidal gold lateral flow dipstick assay (RPA-LFD). We optimized RPA-AGE and RPA-LFD protocols for specific pathogen detection. Target detection was achieved within 35 min using RPA-AGE (30 min amplification at 37 °C followed by 5 min agarose gel electrophoresis), whereas RPA-LFD provided results in 15 min with high specificity (10 min amplification at 37 °C plus 5 min strip reading). Both methods exhibited exclusive specificity to M. bicuspidata, with no cross-reactivity with six pathogens, including Escherichia coli, Staphylococcus aureus, Aeromonas hydrophila, Candida albicans, Saccharomyces cerevisiae, and Microsporidia sp. The detection sensitivity of both platforms reached 4.8 copies/μL in laboratory validation. For field testing, the detection results from 30 field samples showed that although the 70% detection rate was lower than the 83.3% achieved by quantitative PCR, these approaches surpassed the detection rate of conventional PCR (53.3%). Notably, the RPA-LFD platform is applicable under field conditions as no specialized equipment is required. These rapid, sensitive, and specific detection systems provide practical tools for the early diagnosis and containment of M. bicuspidata infections in aquaculture settings. Full article

We report a novel dual-receptor lateral flow biosensor (LFB) for the rapid, sensitive, and visual detection of MCF-7 breast cancer cells as a model for circulating tumor cells (CTCs). The biosensor employs a MUC1-specific aptamer conjugated to colloidal gold nanoparticles as the detection probe and an anti-MUC1 antibody immobilized at the test line as the capture probe, forming a unique “aptamer–cell–antibody” sandwich complex upon target recognition. This design enables instrument-free, visual readout within minutes, achieving a detection limit of 675 cells. The assay also demonstrates robust performance in spiked human blood samples, highlighting its potential as a simple, cost-effective dual-mode point-of-care testing (POCT) platform. This platform supports both rapid visual screening and optional strip-reader-based quantification, making it suitable for early detection and monitoring of breast cancer CTCs. Full article

Objectives: This study evaluated the analytical and clinical performance of a novel NS1 rapid diagnostic test in a dengue-endemic setting in Thailand. Methods: The K-Dengue NS1 Ag test (K.Bio Sciences, Pathumthani, Thailand) was developed. Analytical performance included determination of LOD, reproducibility, and evaluation against potentially cross-reactive pathogens and interfering substances. Unlike conventional assays employing 40 nm colloidal gold, this test incorporates 80 nm gold nanospheres to enhance detection sensitivity. The LOD was determined by serial dilution of recombinant NS1 proteins representing all four dengue virus serotypes. Clinical performance was assessed using 185 archived plasma samples collected between January 2024 and February 2025 from two tertiary care hospitals in Thailand, with a commercial NS1 ELISA serving as the reference standard. Results: The K-Dengue NS1 test demonstrated serotype-specific limits of detection (LODs) for recombinant NS1 antigen, 2.9 ng/mL (DENV-1), 0.5 ng/mL (DENV-2), 25.2 ng/mL 27 (DENV-3), and 4.5 ng/mL (DENV-4). Cross-reactivity testing revealed no false positives against closely related arboviruses or common co-infections, and no interference was observed from frequently encountered pathogens or biochemical substances. In clinical evaluation, the assay achieved a sensitivity of 98.08% (51/52), a specificity of 100% (133/133), and an overall accuracy of 99.37%. Importantly, sensitivity was significantly higher in primary infections (100.00%) than in secondary infections (93.3%, p = 0.288). Conclusions: In this clinically oriented evaluation, the K-Dengue NS1 rapid test showed high specificity and good sensitivity, particularly in primary dengue infections. While the assay may be useful as part of early diagnostic workflows in comparable healthcare settings, reduced sensitivity in secondary infections indicates that negative NS1 results should be interpreted with caution and, where appropriate, supplemented with additional diagnostic methods. Full article

The unique physicochemical properties of gold nanoparticles (GNPs) have made them versatile tools for biomedical applications, such as imaging, therapy, and drug delivery. The surface modification of GNPs with polymers or biomolecules can enhance their colloidal stability and facilitate internalization into cells. However, the efficient and biocompatible delivery to the central nervous system remains a major challenge, as many existing nanocarriers show poor capacity to cross the blood-brain barrier. We developed a method to coat GNPs with linear polyethyleneimine (GNP@PEI) through a chemical reduction bottom-up approach, in which linear PEI hydrochloride acts simultaneously as a reducing and stabilizing agent of colloidal dispersion. This strategy yielded monodisperse spherical GNP@PEI nanoparticles with an average diameter of 50 nm. The physicochemical profile, biocompatibility, and capacity for neural uptake of this potentially brain-targeted nanoplatform were then evaluated. GNP@PEI nanoparticles exhibited high biocompatibility in several primary neural cultures and cell lines, with cellular uptake showing clear cell-type-dependent differences. In vivo studies carried out in a murine model demonstrated that after the intranasal or intraperitoneal administrations of GNP@PEI nanoparticles, detectable levels of gold were found in several organs, including the brain. Collectively, these findings highlight the potential of GNP@PEI as a promising nanoplatform for brain-targeted delivery and for advancing the development of therapeutic strategies for neurological disorders. Full article

The extensive use of sulfathiazole in poultry farming has raised growing concerns regarding its residues in poultry-derived products, posing risks to human health and food safety. To overcome the limitations of conventional detection methods and address the analytical challenges posed by inherent complexity of chicken blood matrix for the detection of sulfathiazole residues in chicken blood, a rapid and sensitive surface-enhanced Raman spectroscopy (SERS) method was developed for detecting sulfathiazole residues in chicken blood. Four colloidal substrates, i.e., gold colloid A, gold colloid B, gold colloid C, and silver colloids, were synthesized and evaluated for their SERS enhancement capabilities. Key parameters, including electrolyte type (NaCl solution), colloidal substrate type (gold colloid A), volume of gold colloid A (550 μL), volume of NaCl solution (60 μL), and adsorption time (14 min), were systematically optimized to maximize SERS intensities at 1157 cm⁻¹. Furthermore, a genetic algorithm-support vector regression (GA-SVR) model integrated with adaptive iteratively reweighted penalized least squares (air-PLS) and multiplicative scatter correction (MSC) preprocessing demonstrated superior predictive performance with a prediction set coefficient of determination (R²_p) value of 0.9278 and a root mean square error of prediction (RMSEP) of 3.1552. The proposed method demonstrated high specificity, minimal matrix interference, and robustness, making it suitable for reliable detection of sulfathiazole residues in chicken blood and compliant with global food safety requirements. Full article

Zearalenone (ZEN), a stable mycotoxin with estrogenic activity produced by various Fusarium species, poses a serious food safety risk. To facilitate the rapid, sensitive, on-site detection of ZEN in maize and ensure consumer dietary safety, a colloidal gold immunochromatographic assay (CG-ICA) based on a monoclonal antibody was established. ZEN was converted via oxime derivatization into hapten ZAN-O, which was conjugated to a carrier protein to prepare an immunogen for producing a highly specific and sensitive monoclonal antibody. Then, the antibody was conjugated into colloidal gold nanoparticles (AuNPs) and used as capture bioprobes of the CG-ICA test strip. The highly sensitive and specific detection platform was established through systematic optimization of pH value, coating antigen concentration, antibody-labeling dosage, incubation time, and strip assembly conditions. Under optimized conditions, the strip exhibited a detection limit of 11.79 pg/mL and an IC₅₀ of 99.06 pg/mL, with a linear detection range of 13.40–732.48 pg/mL. In addition, the anti-interference capability assay demonstrated that the developed test strip possessed excellent specificity. In spiked maize samples, the CG-ICA test strip demonstrated recoveries ranging from 85.36% to 98.86%, with relative standard deviations (RSDs) below 10%. Thus, the CG-ICA strip provides a rapid, sensitive, and robust on-site tool for ZEN screening in maize, and can be adapted to other hazards by simply switching the antibody. Full article

Gold nanoparticles (AuNPs) are widely employed in biosensors; however, conventional synthesis methods require additional surface modification to confer colloidal stability and bioconjugation capability. Here, we report a facile strategy to synthesize carboxymethyl dextran (CMD)-coated AuNPs (AuNP@CMD) that simultaneously serve as a plasmonic label, a stabilizing agent, and a functional scaffold. The CMD was prepared directly via partial carboxymethylation of dextran in a one-pot reduction of HAuCl₄, enabling the synthesis of AuNP@CMD with tunable particle sizes and excellent colloidal stability for at least one month at 4 °C. The CMD coating on AuNPs can prevent nanoparticle aggregation, suppress nonspecific adsorption, and introduce surface carboxyl groups for conjugation of bioprobes. Such characteristics are important to develop plasmonic nanoparticle-linked sorbent assays as an alternative to the conventional colorimetric enzyme-linked immunosorbent assay. When applied to a fiber-optic nanogold-linked sorbent assay, AuNP@CMD enabled ultrasensitive detection of a single-stranded DNA, achieving a detection limit at the femtomolar (fM) concentration level without nucleic acid amplification. Full article

Comprehensive studies of Famille rose porcelains, particularly ruby-back pieces, are rare and have generally not addressed the vibrational signatures arising from gold nanoparticles. Due to the high cultural and material value of these artifacts, a strictly non-invasive approach combining X-ray fluorescence (XRF) and Raman (micro-)spectrometry must be employed. If the conservation of porcelain does not pose any difficulties, fakes exist and they must be identified. Preliminary studies show that the presence of metal nanoparticles generates plasmon-related fluorescence. Our results confirm that plasmon fluorescence is more effective than pXRF for detecting colloidal gold, whereas pXRF efficiently identifies associated elements such as arsenic, tin, and, newly observed, antimony; the presence of iron is difficult to demonstrate due to its ubiquitous occurrence. Yellow and green hues, distinct from those produced by Cu²⁺ ions alone, are mainly due to simple tin yellow (PbSnO₃), while the cobalt used originates from a mixture of European smalt (rich in arsenic and potassium) and Asian ores (rich in manganese). Minimal variability was observed among egg-shell porcelains with similar decorations and dimensions, suggesting a common workshop or standardized raw materials and procedures. Two other egg-shell plates employ a different gold preparation technique (addition of Sn and Sb rather than As), which is visually evident in the ruby color. Full article

The porcine epidemic diarrhea virus (PEDV) has inflicted substantial economic losses on the swine industry, underscoring the need for sensitive point-of-care diagnostics. While lateral flow immunoassays (LFIA) offer rapidity and ease of use, traditional labels like colloidal gold suffer from limited sensitivity. Herein, we developed an aggregation-induced emission (AIE)-based LFIA, termed PED-ALFIA, for the highly sensitive detection of the PEDV antigen. PED-ALFIA exhibited a detection limit of 2.44 × 10² TCID₅₀/mL, which represents a 256-fold improvement in sensitivity over commercial colloidal gold kits and a 4-fold enhancement compared to our previously developed PED-TRFIA. The assay showed no cross-reactivity with other common swine viruses and demonstrated high reproducibility. When tested on clinical samples (n = 42), results showed 100% concordance with qPCR. Utilizing a portable fluorescence reader, the assay can be completed within 10 min, establishing PED-ALFIA as a sensitive, specific, and rapid on-site tool for the early diagnosis of PEDV. Full article

This study establishes a detection method based on image recognition to interpret and quantitatively analyze fluorescent rapid test kits for influenza. The method operates in a dark chamber equipped with a UV-LED, where the fluorescence of the test kit is excited by the UV-LED and subsequently captured using a camera module. The captured images are processed by segmenting the regions of interest (ROI), converting them to grayscale images, and analyzing the grayscale value distributions to identify the control (C) and test (T) line regions. By comparing the values of the C and T lines, the concentration is determined to achieve quantitative analysis. In the linearity validation experiments, the concentrations of influenza A (H1N1) specimens are 2, 4, 6, 8, and 10 ng/mL, achieving a coefficient of determination (R²) of 0.9923. For influenza B (Yamagata) specimens, concentrations of 6, 8, 10, 12.5, and 25 ng/mL resulted in an R² of 0.9878. The established method enables the detection of both influenza A (H1N1) and influenza B (Yamagata), replacing visual qualitative interpretation with quantitative analysis. Currently, the detection method developed in this paper is designed for use exclusively in a dark chamber and is specifically applied to fluorescent rapid tests. It cannot be directly used with conventional colloidal gold-based rapid test reagents. In the future, the proposed detection approach could be integrated with neural networks to enable its application to non-fluorescent rapid test interpretation and to operate beyond the dark chamber environment, for example by utilizing smartphone imaging for result interpretation under normal lighting conditions. Full article