Enrofloxacin (ENR) and its metabolite Ciprofloxacin (CIP) are both a class of fluoroquinolone antibiotics effective against a broad-spectrum microbial infection. Recent surge in the consumption of CIP and ENR has been linked to increased cases of drug-resistant pathogens. This is due to the fact that the antibiotic residues remain in milk, meat, soil and environmental water for a prolonged duration. Although gold standard methods such as LC-MS are sensitive, they suffer from expensive operation and maintenance cost, and would need dedicated facilities and tedious sample preparation steps. Such limitations make on site detection impossible for regulatory bodies in developing countries. To address this issue, we developed a portable device that can detect the presence of CIP and ENR antibiotics in the range of parts per billion (ppb) concentrations accurately. It consists of a polyaniline (PAni) coated U-bent optical fiber with anti-ENR/CIP antibody immobilized on the polymer surface. The sensor relies on the principle of evanescent wave absorbance by antigen-antibody complex. The sensor showed limit of detection (LOD) of 1 ppb with a linear range of operation from 1 ppb to 500 ppb (R2 = 0.96-0.99) in lake water, waste water treatment plant effluent, urine, blood serum, milk and meat samples. The recovery of the sensor ranges from 88% to 120% indicating reasonable accuracy. The sensor has excellent selectivity towards CIP and ENR and showed stability for four weeks indicating its field deployability and robustness. The portable sensor is scalable and contract has been given to an industry partner to mass manufacture the device.
Keywords: Antibiotic biosensors; Evanescent wave; Fiber optic biosensor; Fluoroquinolone; Portable biosensor; Wastewater.
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