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Optical sensors are demonstrating the largest potential for Lab-on-a-chip (LOC) systems to perform sensitive, quantitative, and fast sensing for healthcare and environmental monitoring. Among all options, biosensors based on refractometric sensing schemes combine high sensitivity with label-free detection, however, most of them still have not yet been miniaturized in LOC devices for the analysis of biological targets. Here, we demonstrate for the first time a fully miniaturized optical biosensor based on plasmonic-sensing that enables quantitative detection of biological analytes that are potentially found in milk (lactoferrin, streptomycin). The sensor relies on the unprecedented combination of i) miniaturized, monolithically integrated, and cost-effective optical transduction elements such as organic light-emitting diodes and organic photodiodes, and ii) immunoassay-based bio-recognition elements, for highly sensitive and specific localized surface plasmon resonance (LSPR) based detection via a nanostructured plasmonic grating. The sensor is also equipped with portable read-out electronics and microfluidic circuitry, allowing fast, reproducible and reliable functioning. The quantitative response is calibrated through reference samples and it allows reaching a limit of detection of 10-4 refractive index units (RIU) as LSPR sensor. The quantitative and analyte-specific detection is demonstrated for lactoferrin in the laboratory, giving a sensitivity as low as 9 ug/mL. The presented work opens the way for the universal application of optical biosensors in LOC devices, for on-site food analysis, and health monitoring, among others.
This work received funding from the European Union's Horizon 2020 research and
innovation programme under grant agreement no. 780839 (MOLOKO) and no. 101016706 (h-ALO).
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