"Three-in-One" Multifunctional Hollow Nanocages with Colorimetric Photothermal Catalytic Activity for Enhancing Sensitivity in Biosensing.

Immunochromatographic assays (ICAs) have been widely used in the field detection of mycotoxin contaminants. Nevertheless, the lack of multisignal readout capability and the ability of signaling tags to maintain their biological activity while efficiently loading antibodies remain a great challenge in satisfying diverse testing demands. Herein, we proposed a novel three-in-one multifunctional hollow vanadium nanomicrosphere (high brightness-catalytic-photothermal properties)-mediated triple-readout ICA (VHMS-ICA) for sensitive detection of T-2. As the key to this biosensing strategy, vanadium was used as the catalytic-photothermal characterization center, and natural polyphenols were utilized as the bridging ligands for coupling with the antibody while self-assembling with formaldehyde cross-linking into a hollow nanocage-like structure, which offers the possibility of realizing a three-signal readout strategy and improving the coupling efficiency to the antibody while preserving its biological activity. The constructed sensors showed a detection limit (LOD) of 2 pg/mL for T-2, which was about 345-fold higher than that of conventional gold nanoparticle-based ICA (0.596 ng/mL). As anticipated, the detection range of VHMS-ICA was extended about 8-fold compared with the colorimetric signal alone. Ultimately, the proposed immunosensor performed well in maize and oat samples, with satisfactory recoveries. Owing to the synergistic and complementary interactions between distinct signaling modes, the establishment of multimodal immunosensors with multifunctional tags is an efficient strategy to satisfy diversified detection demands.

Trifunctional Nanocomposites with Colorimetric Magnetic Catalytic Activities Labels in Sandwich Immunochromatographic Detection of Escherichia coli O157:H7.

The emergence of nanoenzymes has catalyzed the robust advancement of the lateral flow immunoassay (LFIA) in recent years. Among them, multifunctional nanocomposite enzymes with core-shell architectures are considered preferable for promoting the sensing ability due to their good biocompatibility, precise control over size, and surface properties etc. Herein, we developed a dual-channel ensured lateral flow immunoassay (DFLIA) platform utilizing a magnetic, colorimetric, and catalytic multifunctional nanocomposite enzyme (Fe3O4@TCPP@Pd) [TCPP, Tetrakis (4-carboxyphenyl) porphyrin] for the ultrasensitive and highly accurate rapid detection of Escherichia coli O157:H7 (E. coli O157:H7). Fe3O4@TCPP@Pd-mAb exhibits superior performance compared to traditional AuNPs, including enhanced sensitivity and an extended linear detection range, benefiting from its high brightness signal, strong magnetic separation ability, and high peroxidase activity (Vmax = 2.32 µM S1-). Moreover, the Fe3O4@TCPP@Pd-labeled mAb probe exhibited exceptional stability and high affinity toward E. coli O157:H7 (with an affinity constant of approximately 1.723 × 109 M-1), indicating its potential for the efficient capture of the pathogen. Impressively, the developed Fe3O4@TCPP@Pd-DFLIA achieved ultrasensitive detection for E. coli O157:H7 with pre- and postcatalytic naked-eye detection sensitivities of 255 cfu/mL and 77 cfu/mL, respectively, representing an approximately 41-fold improvement over the conventional AuNP-based LFIA and also possessed good specificity and reproducibility [relative standard deviation (RSD) < 10%]. Additionally, the established DFLIA exhibited satisfactory recoveries in detecting pork and milk samples, further validating the reliability of this platform for immunoassays and demonstrating its potential for utilization in bioassays and clinical diagnostics.

Novel Dumbbell-like CeVO4 Carrier-Based Immunochromatographic Assay for Highly Sensitive T-2 Toxin Detection in Food Samples.

Improving the sensitivity of immunochromatographic assays (ICAs) lies in the signal strength and probe activity of the labeled tracers, and the color properties and structure of the labeled tracers are key factors affecting the biological activity. In this study, cerium vanadate (CeVO4) of different sizes and shapes (230, 1058, and 710 nm) was synthesized to investigate its impact on the performance of ICA for T-2 detection. The prepared CeVO4 possessed outstanding stability, a large specific surface area, superior biocompatibility, and high compatibility with T-2 mAb (affinity constant was 3.14 × 108 M-1). As labeling probes for competitive ICA, the results showed that 1058 nm of CeVO4 as labels exhibited the best detection performance, with a limit of detection (LOD) of 0.079 ng/mL, which was substantially 19-fold less than the average of gold nanoparticle ICA. Additionally, CeVO4-ICA was effectively used to detect T-2 toxin, and the recovery rate for spiking corn and oatmeal samples was determined to be 81.27-115.44% (relative standard deviation <9.16%). The above information demonstrates the efficiency and applicability of CeVO4-ICA as a technique for quick and thorough identification of T-2 toxin residues in food.

A Versatile PdRu Bimetallic Nanoenzyme-Integrated Enzyme-Linked Immunosorbent Assay for Highly Sensitive Escherichia coli O157:H7 Detection.

Nanozymes have drawn much attention as an enzyme mimetic with low cost and stability in enhancing analytical performance. Herein, a peroxidase-mimicking nanozyme-improved enzyme-linked immunosorbent assay (ELISA) was developed employing the bimetallic PdRu nanozyme to replace the natural enzymes as a catalytic carrier for the sensing of Escherichia coli O157:H7 (E. coli O157:H7). The PdRu nanozyme displayed ultrahigh catalytic activity, possessing a catalytic rate that was 5-fold higher than horseradish peroxidase (HRP). In addition, PdRu exhibited great biological affinity with antibody (affinity constant was about 6.75 × 1012 M) and high stability. All those advantages ensure the successful establishment and the construction of a novel colorimetric biosensor for E. coli O157:H7 detection. PdRu-based ELISA not only achieved an ultrasensitive detection sensitivity (8.7 × 102 CFU/mL) by approximately 288-fold as compared to the traditional HRP-based ELISA and also possessed satisfactory specificity and reproducibility (relative standard deviation (RSD) < 10%). Furthermore, the feasibility of PdRu-ELISA was further evaluated by detecting E. coli O157:H7 in actual samples with satisfactory recoveries, indicating its potential for applications in bioassays and clinical diagnostics.

Ultrabright Fluorescent Nanorod-Based Immunochromatographic with Low Background for Advancing Detection Performance.

Nanomaterials-based immunochromatographic assays (ICAs) are of great significance in point-of-care testing (POCT), yet it remains challenging to explore low background platforms and high chromogenic intensity probes to improve detection performance. Herein, we reported a low interference and high signal-to-noise ratio fluorescent ICA platform based on ultrabright persistent luminescent nanoparticles (PLNPs) Zn2GeO4: Mn, which could produce intense photoluminescence at 254 nm excitation to reduce background interference from ICA substrates and samples. The prepared immunosensor was successfully applied in T-2 toxin detection with a remarkable limit of detection of 0.025 ng/mL, which was 22-fold more sensitive compared with that of traditional gold nanoparticles. Ultimately, a portable 3D-printed detection device equipped with a smartphone analyzing application was fabricated for quantitative readout in POCT, achieving favorable recoveries in practical sample detection. This work provides a creative attempt for ultrabright PLNP-based low background ICA, and it also guarantees its feasibility in practical POCT.

Bioinspired Core-shell nanospheres integrated in multi-signal immunochromatographic sensor for high throughput sensitive detection of Bongkrekic acid in food.

Nowadays, notable progress has been achieved in detecting foodborne toxins by employing nanoenzyme-based lateral flow immunoassay (NLFIA) sensors in point-of-care testing (POCT). It continues to be a major challenge to maximize the enzyme-like performance of nanozymes for educe any potential uncertainties in catalytic process. In this study, we employed a facile and efficient self-assembly approach to fabricate nucleoid-shell structured biomimetic nanospheres CuS@Au-Pt (CAP), which demonstrates enhanced brightness of the colorimetric signal, excellent affinity, and excellent peroxidase activity. The integration of CAP with a competitive-assay NLFIA platform enabled sensitive immunochromatographic detection of bongkrekic acid (BA), with LOD as low as 0.66 ng/mL. After signal amplification through enzyme-like reaction, the detection range was extended around 1-fold. Additionally, CAP-NLFIA effectively detected BA with a recovery rate of 80.96-119.36% for real samples. The study proposes using CAP as a signal reporter in a dual-readout LFIA, which can establish a high throughput sensitive detection platform.