Quantum Dot-Based Immunoassays: Unraveling Sensitivity Discrepancies and Charting Future Frontiers

Abstract

The 2023 Nobel Prize in Chemistry honors the groundbreaking contributions of Alexei Ekimov, Louis Brus, and Moungi Bawendi to the field of quantum dots (QDs). In this spirit, we developed a direct competitive QD fluorescence immunoassay (dc-QD-FLISA) to detect aristolochic acid type I (AAI), a potent carcinogen found in herbal remedies. Unexpectedly, the dc-QD-FLISA exhibited lower sensitivity than that of an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA), contrary to our initial expectations. This discrepancy in the sensitivity prompted a comprehensive analysis of the entire experimental process. We propose that steric hindrance between QDs and antigen-binding sites on antibodies may significantly diminish the binding efficiency, reducing sensitivity within the dc-QD-FLISA method. Furthermore, issues such as buffer conditions, antibody handling, and separation methods are also contributing factors. We recommend site-directed QD modification and stringent consideration of the experimental conditions. This study not only provides insights into QD-based immunoassays but also highlights the need for future advancements in immunoassay technology in terms of augmenting sensitivity and specificity, potentially revolutionizing disease diagnosis, biomarker discovery, and biomedical research.

Highly Specific Aptamer–Antibody Birecognized Sandwich Module for Ultrasensitive Detection of a Low Molecular Weight Compound

“…If the second antibody is linked to an enzyme in the enzyme-linked immunosorbent assay (ELISA), the presence of the target can be readily detected within dozens of minutes. , Thus, ELISA as a standardized diagnostic method has been widely used in the past decade due to simple operation, short time, and low cost. Despite these attributes, the false negatives caused by low valence of the antibody and the false positives caused by the complex environment of the sample reduce the credibility of ELISA. , Meanwhile, the enzymatic coloration reaction in the ELISA determines its detection limit at the nanomolar level, rendering ELISA already unable to meet the current demand. , More importantly, the assay is more suitable for the detection of macromolecular weight targets (proteins) rather than low molecular weight compounds (mycotoxins), since two antibodies with large steric hindrance are difficult to simultaneously bind to a small molecule target. Thus, the false negatives are significantly aggravated once the micromolecule is set as the target in ELISA. , Meanwhile, a nucleic-acid-based aptamer, a specific sequence recognizing a target molecule, can directly bind low molecular compounds via the flexible structure .…”