Search

Palladium nanoparticles (PdNPs) are composed mainly of inert noble metals, and their outstanding properties have attracted wide attention. PdNPs are not only capable of mimicking the oxidase-like characteristics of natural bio-enzymes, but they also present a clear black band in the test zone. In this work, the synthesized PdNPs promoted a transformation of colorless tetramethylbenzidine (TMB) to a blue oxidation product of TMB, providing a Km value of 0.09 mM for TMB, and revealing the good catalytic performance of the synthesized PdNPs. For both signal generation and amplification, PdNPs effectively replaced natural bio-enzymes as a new labeling tag. Thus, the PdNP-based enzyme-free single-step immunoassays were successfully developed for efficient and sensitive detection of glycocholic acid (GCA). Under optimal conditions, a noticeable linear relationship was identified by the enzyme-linked immunosorbent assay (ELISA) over a range of 8–2390 ng/mL, while the visual limit of detection (vLOD) in the constructed lateral flow immunoassay (LFA) was 10 ng/mL for GCA. The recovery rate in spiked urine samples obtained by the ELISA ranged from 84.2 to 117.9%, which was consistent with the results in LFA. The present work demonstrates the potential of PdNPs as labeling matrices in enzyme-free single-step immunoassays. [ABSTRACT FROM AUTHOR]

Platinum nanoflowers (PtNFs) were utilized in a competitive enzyme-linked immunosorbent assay (ELISA) and in a lateral flow immunoassay (LFIA) for superior peroxidase-like activity and intense brown color, respectively. PtNFs were linked to the polyclonal antibody (pAb) to form the pAb-PtNFs probes for the dual immunoassay. Based on optimized pAb-PtNF probes, both enzyme-linked immunosorbent assay (PtNFs-ELISA) and lateral flow immunoassay (PtNFs-LFIA) perform very well. The absorbance at 450 nm decreases linearly in the DHEA concentration range 2.1 to 118.1 ng mL−1, and the limit of detection is 1.3 ng mL−1 and the IC50 value is 15.7 ng mL−1 of PtNFs-ELISA. The visual cut-off value of PtNFs-LFIA is 10.0 ng mL−1. The average recoveries from spiked samples range from 95.0 to 108.9% with a coefficient of variation below 12.2%. Excellent recoveries and correlation between the two methods were observed. Furthermore, the designed immunosensors exhibited good selectivity, confirming a broad development prospect in DHEA monitoring. [ABSTRACT FROM AUTHOR]

In this work, three fluorescein-labeled DiBP derivatives (tracers) with different chemical structures and spacer bridges were synthesized and purified by thin-layer chromatography (TLC). Compared with the heterologous tracer, the homologous tracer exhibited more affinity to the antibody. What is more, the tracer concentration and the antibody dilution were further evaluated to improve the sensitivity of fluorescence polarization immunoassay (FPIA). On the basis of sensitive antibody and tracer, a rapid and specific FPIA has been established for the detection of DiBP contamination in the romaine lettuce, which has rarely been reported before. Under the optimal conditions, the developed FPIA showed a good detection range from 8.82 to 2152.84 ng/mL, with a detection limit of 1.77 ng/mL. In addition, the cross-reactivity to several compounds structurally related to DiBP was less than 7.37 %. Therefore, DiBP contamination in spiked romaine lettuce samples was detected by FPIA, with the recovery from 88.28 to 119.11 %. Moreover, when compared with high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA), the results analyzed by the developed FPIA shows a strong reliability and a high correlation value of 0.978 and 0.980, respectively. Thus, this data, combined with rapidity and simplicity of the assay, demonstrates that the established FPIA is a suitable method for high throughput screening of DiBP contamination in the romaine lettuce. [ABSTRACT FROM AUTHOR]