Search

In this paper, five fluorescein-labeled dehydroepiandrosterone (DHEA) derivatives (tracers) with different chain lengths between the fluorescein and hapten were synthesized and featured so as to establish a fluorescence polarization immunoassay (FPIA) for DHEA detection in human urine samples with previously prepared polyclonal antibody against DHEA. The outcomes of the structure of tracer on FPIA sensitivity were investigated. Under the optimal condition, the fluorescence polarization value (FP) decreases linearly in DHEA concentration, ranging from 1.6 to 243.3 ng mL -1 , with the limit of detection of 1.1 ng mL -1 and IC 50 value of 25.1 ng mL -1 . Moreover, the developed FPIA was time-saving as it could complete the detection within 3 min. FPIA and commercial enzyme-linked immunosorbent assay kit were both applied to analyze the spiked human urine samples with DHEA. Excellent recoveries (92.1-108.0%) and satisfactory correlation coefficient (R 2  = 0.98) were acquired with the two methods, indicating that the developed FPIA was a fast and efficient screening immunoassay with accuracy and sensitivity for DHEA detection in human urine samples. Graphical abstract.

The traditional gold-nanoparticle-based lateral flow immunoassay (LFIA) cannot satisfy the requirements for the sensitive detection of dehydroepiandrosterone (DHEA) in human urine. To enhance the sensitivity of the LFIA, platinum-iridium nanocubes (Pt-Ir NCs) with high catalytic efficiency and stability were synthesized and labelled with polyclonal antibody (pAb) to form a pAb-Pt-Ir probe. For the detection of DHEA, a novel LFIA with Pt-Ir NCs as an optical label and an enhanced LFIA in which the peroxidase-like activity of the Pt-Ir NCs was triggered by the introduction of the chromogenic substrate 3-amino-9-ethyl-carbazole (AEC) were developed and compared with a LFIA with platinum nanocubes (PtNCs) as an optical label. The visual limit of detection was 0.5 ng mL-1 for Pt-Ir-LFIA and 0.05 ng mL-1 for AEC-enhanced Pt-Ir-LFIA, in comparison to 100 ng mL-1 for PtNCs-LFIA and 50 ng mL-1 for AEC-enhanced PtNCs-LFIA. The average recoveries from spiked urine samples ranged from 90.8% to 110.4%, with a coefficient of variation below 12.6%, suggesting the accuracy and reliability of our developed immunoassay. Achieving excellent sensitivity, specificity, and reproducibility, Pt-Ir-LFIA provided a promising platform for monitoring DHEA.

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 IC 50 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. Graphical Abstract.

Multimodal lateral flow immunoassay (LFIA) has displayed its potential to improve practicability and elasticity of point-of-care testing. Herein, multifunctional core-shell-shell Au@Pt@Ag NPs loaded with dual-layer Raman reporter molecules of 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB) with a characteristic combination of color-photothermal-Raman performance were constructed for colorimetric LFIA (CM-LFIA), photothermal LFIA (PT-LFIA) and surface-enhanced Raman scattering-based LFIA (SERS-LFIA), respectively. The highly specific nanoprobes, being obtained through the combination of the resulted dual-layer DTNB modified Au@Pt@Ag NPs with the antibody, were triumphantly utilized in exploring multimodal LFIA with one visual qualitative and two optional quantitative modes with excellent sensing sensitivity. Under optimal conditions, the limit of detection (LOD) for the model hazardous analyte dehydroepiandrosterone (DHEA) were 1.0 ng mL−1 for CM-LFIA, 0.42 ng mL−1 for PT-LFIA, and 0.013 ng mL−1 for SERS-LFIA, three of which were over 100-fold, 200-fold and 7 000-fold more sensitive than conventional visual AuNPs-based LFIA, respectively. In addition, the quantitative PT-LFIA and SERS-LFIA sensors worked well in spiked real samples with acceptable recoveries of 96.2 – 106.7% and 98.2 – 105.2%, respectively. This assay demonstrated that the developed multimodal LFIA had a great potential to be a powerful tool for accurate tracing hazardous analytes in complex samples. Scheme 1 Schematic illustration of synthesis of dual-layer DTNB modified Au@Pt@Ag NPs as the sensing probe (A), and the multimodal lateral flow immunoassay based on dual-layer DTNB modified Au@Pt@Ag NPs for dehydroepiandrosterone (DHEA) detection (B). [Display omitted] • Core-shell-shell Au@Pt@Ag NPs loaded with Raman molecules displayed excellent color, photothermal, and Raman performance. • Multifunctional Au@Pt@Ag NPs was used for multimodal lateral flow immunoassay (LFIA). • These multimodal LFIA displayed outstanding performance in terms of sensitivity, specificity, and accuracy. • Multimodal LFIA was a promising tool for sensing hazardous analytes. [ABSTRACT FROM AUTHOR]

Nanozymes are a type of artificial enzymes that can replace traditional natural enzymes for biotechnology to biosensing, biocatalysis, and biological imaging. Nevertheless, it is still a huge challenge in the pursuit of new mimic enzymes or multiple enzyme-like activities mimics. In this work, PtCu nanocages (PtCu NCs) with hollow interior and rough exterior was prepared. PtCu NCs displayed superior tetra-enzyme mimetic activities including peroxidase (POD)-, superoxide dismutase (SOD)-, catalase (CAT)- and ascorbic acid oxidase (AAO)-like activities. Meaningfully, attributed to the POD mimic activity, sensitive and convenient colorimetric biosensors for L -Cysteine (L -Cys), homocysteine (Hcy) and glutathione (GSH) were developed with wide linear range (LR) and low limit of detection (LOD) of 0.28 μM, 1.48 μM and 0.75 μM (S/N = 3), respectively. Moreover, based on the AAO mimic activity, the cascade reaction was proposed including the oxidation of ascorbic acid (AA) to dehydroascorbic acid (DHAA) by PtCu NCs and the formation of the fluorescent quinoxaline (DFQ) coming from the reaction between DHAA and o-phenylenediamine (OPD). A novel fluorescent biosensor for dehydroepiandrosterone (DHEA) was successfully constructed based on the immunoassay method combined with the cascade reaction for AA, with the LR of 0.6–464.9 ng·mL−1 and LOD of 0.5 ng·mL−1. These colorimetric and fluorescent biosensors displayed outstanding performance in terms of sensitivity, specificity, and accuracy for real samples, suggesting that PtCu NCs was a promising candidate for biosensing. Scheme 1 Schematic illustration of tetra-enzyme mimetic activities of PtCu NCs, and the principle for colorimetric sensor for biothiols and cascade reaction (A), the principle for fluorescent sensor for dehydroepiandrosterone (DHEA) (B). [Display omitted] • PtCu Nanocages displayed POD-, SOD-, CAT- and AAO-like activities. • Colorimetric sensors for biothiols were explored utilizing POD mimic of PtCu NCs. • Fluorescent sensor for DHEA was established based on AAO mimic of PtCu NCs. • These biosensors displayed outstanding performance in terms of sensitivity, specificity, and accuracy. • PtCu NCs was a promising candidate for biosensors. [ABSTRACT FROM AUTHOR]