Sensitive detection of Escherichia coli in diverse foodstuffs by electrochemical aptasensor based on 2D porphyrin-based COF.

The two-dimensional porphyrin-based covalent organic framework (denoted by Tph-TDC-COF) was used as the sensitive layerto build an aptamer-based electrochemical sensor for the detection of Escherichia coli (E.coli). Tph-TDC-COF produced with 5,10,15,20-tetrakis(4-aminophenyl)-21H, 23H-porphine (Tph) and [2,2'-bithiophene]-2,5'-dicarbaldehyde (TDC) as building blocks exhibited a highly conjugated structure, outstanding conductivity, large specific surface area, and strong bioaffinity towards aptamers. The adoption of Tph-TDC-COF-modified electrode resulted in improved sensing performance and increased anchoring affinity toward the E.coli-targeted aptamer. Under optimal conditions, the Tph-TDC-COF-based electrochemical aptasensor demonstrated an extremely low detection limit of 0.17 CFU mL-1 for E.coli detection within a linear range of 10 to 1 × 108 CFU mL-1, accompanied by good stability, excellent reproducibility and regeneration ability, and wide practical applications. The current electrochemical aptasensing technique has the potential to be extended to detect different foodborne bacteria using specific aptamer, therefore widening the application of COFs in biosensing and food safety fields.

Hierarchical CoCoPBA@PCN-221 nanostructure for the highly sensitive detection of deoxynivalenol in foodstuffs.

An electrochemical impedimetric immunosensor was constructed based on a hierarchical nanostructured CoCo Prussian blue analogue entrapped by a Zr-based porphyrin MOF (denoted by CoCoPBA@PCN-221) for the sensitive detection of deoxynivalenol (DON). Given that CoCoPBA@PCN-221 demonstrated a hierarchical nanostructure, large specific surface area, and the synergistic effect between mixed metal valence states (Co2+/Co3+) and Zr clusters, it thus displayed a high binding interaction with the DON-targeted antibody. Compared with CoCoPBA and PCN-221, CoCoPBA@PCN-221 showed a superior stabilization ability toward the antibody-antigen complex in aqueous solution. Under optimum conditions, the CoCoPBA@PCN-221-based impedimetric immunosensor exhibited a good linear range from 1 fg mL-1 to 1 ng mL-1, and an ultralow detection limit of 0.14 fg mL-1, accompanied by high selectivity, reproducibility, stability, and applicability in foodstuffs. This method allows the integration of MOFs with cascading properties for applications in the biosensing and food safety fields.