Nanomaterials-based
immunochromatographic assays (ICAs) have gained
great commercial success in real-life point-of-care testing (POCT).
Exploring novel carriers of ICAs with improved signaling and sustained
activity favors the development of sensitive POCT. Herein a potent
signal biotag, colored Staphylococcus aureus (SA),
was created for ICA carriers through a mild self-assembly strategy,
providing high luminance and abundant specific binding sites for immobilization
of monoclonal antibodies (mAbs). The biocompatible SA-dyes (SADs)
retained both an intact surface structure for mAbs labeling (Fc portion)
and the superior bioactivity of immobilized mAbs (affinity constant
was about 109 M–1), thus waiving the
intrinsic limitations of traditional nanomaterials and endowing high
sensitivity. Proof-of-concept was demonstrated by employing Congo
red- or/and fluorescein isothiocyanate-embedded SA (SACR, SAFITC,
and SACR–SAFITC) as ICA carriers to detect zearalenone (ZEN)
through colorimetric or/and fluorimetric signals. Furthermore, the
ICAs satisfied the clinical requirement perfectly, including limit
of detection (0.013 ng/mL, which was at least an 85-fold improvement
over that of traditional gold nanoparticles-based ICA), linearity
(R
2 > 0.98), reproducibility (RSD <
8%), selectivity, and stability. Importantly, the proposed biosensors
could be well-applied in four real samples for ZEN monitoring with
satisfactory recoveries, correlating well with the results from liquid
chromatography–tandem mass spectrometry (LC-MS). This work
also proved a universal design for tailoring coloration bands for
SAD–ICA detection of multiple analytes.
The rapid detection of toxins is of great significance to food security and human health. In this work, a dual-modality immunochromatographic test (DICT) mediated by Staphylococcus aureus (SA)-biosynthesized polymer dots (SABPDs) was constructed for sensitive monitoring of zearalenone (ZEN) in agro products. The SABPDs as potent microorganism nanoscaffolds with excellent solubility, brightness, and stability were ingeniously fabricated employing hydroquinone and SA as precursors in the Schiff base reaction and a self-assembly technique. Thanks to the fact that they not only preserved an intact microsphere for loading Fc regions of monoclonal antibodies (mAbs) and the affinity of their labeled mAbs to antigen but also generated superb colorimetric−fluorescent dual signals, the versatile SABPDs manifested unique possibilities as the new carriers for dual-readout ICT with remarkable enhancement in sensitivity in ZEN screening (limit of detection = 0.036 ng/mL, which was 31-fold lower than that of traditional gold nanoparticlebased ICT). Ultimately, the proposed immunosensor performed well in millet and corn samples with satisfactory recoveries, demonstrating its potential for point-of-care testing. This work offers a bio-friendly strategy for biosynthesizing cell-based PD vehicles with bimodal signals for food safety analysis.
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