Colorimetric and electrochemical (dual) thrombin assay based on the use of a platinum nanoparticle modified metal-organic framework (type Fe-MIL-88) acting as a peroxidase mimic.

An electrochemical and colorimetric dual-readout method is described for the determination of thrombin. A platinum nanoparticle (Pt NP) modified metal organic framework (MOF) acts as a peroxidase (POx) mimic that causes the formation of a blue product from 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide, with an absorption maximum at 650 nm. In addition, gold nanoparticles enrich initiators that trigger the hybridization chain reaction for dual signal amplification to generate an electrochemical current typically measured at 0.31 V (from -0.5 to -0.1 V) and allow quantitation of thrombin with high sensitivity and over a wide detection range. The colorimetric and electrochemical (dual) thrombin assay produces two kinds of signals which warrants accuracy, diversity, and an option for visual inspection. The dual-channel sensor allows for the quantitative determination of thrombin with a low detection limit (0.33 fM) for the electrochemical method and 0.17 pM for the colorimetric method) and over a wide detection range (1 fM to 10 nM for electrochemical method and 0.5 pM to 1 nM for colorimetric method). The electrochemical detection limit is lower than that of colorimetry, and the linear range is wider, which is more suitable for further quantitative analysis of the target. Graphical abstract Schematic representation of a colorimetric and electrochemical (dual) thrombin assay based on the use of a platinum nanoparticle modified metal-organic framework for color development and hybridization chain reaction for electrochemical signal. C-TBA: complementary sequences of thrombin aptamer, TBA: thrombin aptamer, I-Au NPs: initiators enriched by gold nanoparticles, S-AuE: sensing gold electrode, RS-AuE: reacted sensing gold electrode, TB: thrombin, MB: Methylene Blue, HCR: hybridization chain reaction.