Metal–Organic Framework-Mediated Bioorthogonal Reaction to Immobilize Bacteria for Ultrasensitive Fluorescence Counting Immunoassays

Abstract

Ultrasensitive quantification of protein biomarkers has significant implications in disease diagnosis. Herein, we report a fluorescent bacteria counting immunoassay (FBCIA) strategy for protein biomarker detection based on a cascade signal conversion and amplification strategy including the copper metal−organic framework (Cu-MOF)-mediated Cu(I)-catalyzed azide−alkyne cycloaddition (CuAAC) for fluorescent bacteria immobilization that converted the concentration of target protein to countable bacterial number and the further self-proliferation of bacteria to amplify the detectable bacterial number. The developed lowbackground and enzyme-free cascade methodology achieved highly sensitive detection of carcinoembryonic antigen (CEA) and prostate-specific antigen (PSA) with detection limits down to 0.8 pg/mL and 64.5 fg/mL, respectively. On top of that, we also developed a smartphone device for visualizing individual bacteria and point-of-care counting of the resulting bacteria for the detection of clinical samples. The good consistency between FBCIA and clinical enzyme-linked immunosorbent assay (ELISA) validated the high reliability and promising potential of our developed platform in clinical applications.

Sensitivity enhancement of a Cu (II) metal organic framework-acetylene black-based electrochemical sensor for ultrasensitive detection of imatinib in clinical samples

“…CuMOF related characteristic absorbance peak was at about 258 nm in the ultraviolet-visible (UV-vis) patterns ( Gao et al, 2023 ). And introduction of AB made the new absorption peak exhibited a positive shift from 258 to 284 nm, indicating that CuMOF-AB nanocomposites had successfully formed ( Figure 2D ).…”

Engineering of CuMOF-SWCNTs@AuNPs-Based Electrochemical Sensors for Ultrasensitive and Selective Monitoring of Imatinib in Human Serum

“…SWCNT-COOH exhibited high absorption over a wide wavelength range (250–850 nm). The broad peak at around 255 nm was related to the characteristic peak of CuMOF, which is displayed in curve (b) . For comparison, as shown in the UV–vis spectra of curve (c), CuMOF-SWCNTs@AuNPs produced a stronger absorption peak near 255 nm with the addition of SWCNTs@AuNPs.…”

“…The broad peak at around 255 nm was related to the characteristic peak of CuMOF, which is displayed in curve (b). 31 For comparison, as shown in the UV–vis spectra of curve (c), CuMOF-SWCNTs@AuNPs produced a stronger absorption peak near 255 nm with the addition of SWCNTs@AuNPs. Moreover, according to the AuNP-related characteristic absorbance peak at 540 nm ( Figure 2 B inset), it could be reasonably deduced that the hybrid structure of the CuMOF-SWCNTs@AuNPs was fabricated.…”

Click Reaction-Mediated Fluorescent Immunosensor Based on Cu-MOF Nanoparticles for Ultrasensitive and High-Throughput Detection of Aflatoxin B1 in Food Samples

“…Second, to obtain an excellent analytical performance, the enzyme requires a certain amount of time to catalyze the conversion of nonreducing substrates into reducing substrates, which cannot meet the demand for rapid analysis. Most of all, the click reaction is performed by direct reduction of the obtained amount of Cu­(II) to Cu­(I), which lacks the signal amplification process with a limited signal output . Immunoassays have more breadth of detection objects, − and the introduction of the enzyme-free click reaction strategy as a signal amplification strategy into immunoassays can largely expand its application. − …”

“…Most of all, the click reaction is performed by direct reduction of the obtained amount of Cu(II) to Cu(I), which lacks the signal amplification process with a limited signal output. 21 Immunoassays have more breadth of detection objects, 22−24 and the introduction of the enzyme-free click reaction strategy as a signal amplification strategy into immunoassays can largely expand its application. 25 Therefore, the key aspect of using the CuAAC strategy to enhance the sensitivity of the immunoassay should be how to achieve efficient unification between the high loading of Cu(II) and the binding of biorecognition molecules.…”