A U-bent fiberoptic absorbance biosensor array (ArFAB) for multiplexed analyte detection

Compact and dip-type U-bent fiber optic sensor (U-FOS) probes exhibit remarkably high evanescent wave absorbance (EWA) sensitivity and are highly suitable for label-free multiplexed detection of proteins, virii and bacteria by exploiting their intrinsic optical absorption property in the UV region. Here, we show the design and development of a novel EWA based eight-channel array fiber optic absorbance biosensor (ArFAB) using U-FOS probes for multi-analyte detection or multi-sample analysis in real-time. A proof-of-concept ArFAB is designed to consist of a UV LED (λmax = 285 nm) and a highly sensitive CMOS linear image sensor coupled to a sensor probe module through fan-out (1-to-8) and parallel (8 nos) fiber bundles respectively. The sensor probe module is designed to hold and efficiently couple the light to/from 8 U-FOS probes with the help of ceramic ferrules and mating sleeves. The CMOS line sensor, with 8 coupling fibers equidistantly placed along its length, distinctly quantifies the intensity response from each of the eight U-FOS probes. The ArFAB was systematically validated for reproducible optical intensity measurements and label-free multiplexed detection of proteins and bacteria was realized. Moreover, a novel sandwich immunoassay with plasmonic labels for immunoglobulin G (IgG) with picomolar analyte detection limits at 280 nm wavelength is demonstrated. With mass-producible U-FOS probes and a low-cost optoelectronic instrumentation that can be easily customized for LSPR or any other sensing phenomenon, the ArFAB is highly promising for cost-effective biomolecular interactions, and cell analyses and clinical diagnostic applications.