A vinyl sulfone clicked carbon dot-engineered microfluidic paper-based analytical device for fluorometric determination of biothiols Fernández Mateo, Fernando Ortiz Gómez, Inmaculada Ortega Muñoz, Mariano Marín-Sánchez, Antonio Orbe Payá, Ignacio De Hernández Mateo, Fernando Capitán Vallvey, Luis Fermín Santoyo González, Francisco Salinas Castillo, Alfonso Microfluidic paper-based device Off-on assay Carbon dots This study was supported by projects from the Spanish MINECO (CTQ2017-86125 and CTQ2016-78754-C2-1-R). The project was also partially supported by the European Regional Development Funds (ERDF). A microfluidic paper-based analytical device integrating carbon dot (CDs) is fabricated and used for a fluorometric off-on assay of biothiols. Vinyl sulfone (VS) click immobilization of carbon dots (CDs) on paper was accomplished by a one-pot simplified protocol that uses divinyl sulfone (DVS) as a homobifunctional reagent. This reagent mediated both the click oxa-Michael addition to the hydroxyl groups of cellulose and ulterior covalent grafting of the resulting VS paper to NH2-functionalized CDs by means of click aza-Michael addition. The resulting cellulose nanocomposite was used to engineer an inexpensive and robust microfluidic paper-based analytical device (μPAD) that is used for a reaction-based off-on fluorometric assay of biothiols (GSH, Cys, and Hcy). The intrinsic blue fluorescence of CDs (with excitation/emission maxima at 365/450 nm) is turned off via the heavy atom effect of an introduced iodo group. Fluorescence is turned on again due to the displacement of iodine by reaction with a biothiol. The increase in fluorescence is related to the concentration over a wide range (1 to 200 μM for GSH and 5–200 μM for Cys and Hcy, respectively), and the assay exhibits a low detection limit (0.3 μM for GSH and Cys and 0.4 μM for Hcy). The method allows for rapid screening and can also be used in combination with a digital camera readout 2026-01-28T09:36:14Z 2026-01-28T09:36:14Z 2020 journal article Published version: Ortiz-Gomez, I., Ortega-Muñoz, M., Marín-Sánchez, A. et al. A vinyl sulfone clicked carbon dot-engineered microfluidic paper-based analytical device for fluorometric determination of biothiols. Microchim Acta 187, 421 (2020). https://doi.org/10.1007/s00604-020-04382-9 https://hdl.handle.net/10481/110401 10.1007/s00604-020-04382-9 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Springer Nature