Development of a surface plasmon resonance based immunosensor for diclofenac quantification in water

A Surface Plasmon Resonance (SPR) biosensor based on an inhibition immunoassay was developed for the detection of diclofenac (DCF) in aqueous solution. Due to the small size of DCF, an hapten-protein conjugate was produced by coupling DCF to bovine serum albumin (BSA). DCF-BSA conjugate formation was confirmed via MALDI-TOF mass spectrometry. The resulting conjugate was immobilized onto the surface of a sensor fabricated via e-beam deposition of a 2 nm chromium adhesion layer followed by a 50 nm gold layer onto precleaned BK7 glass slides. Immobilization onto the nano thin gold surface was accomplished by covalent amide linkage through a self-assembled monolayer. Samples were composed of a mixture of antibody at a fixed concentration and DCF at different known concentrations in deionized water, causing the inhibition of anti-DCF on the sensor. The DCF-BSA was obtained with a ratio of 3 DCF molecules per BSA. A calibration curve was performed using concentrations between 2 and 32 μg L−1. The curve was fitted using the Boltzmann equation, reaching a limit of detection (LOD) of 3.15 μg L−1 and limit of quantification (LOQ) of 10.52 μg L−1, the inter-day precision was calculated and an RSD value of 1.96% was obtained; and analysis time of 10 min. The developed biosensor is a preliminary approach to the detection of DCF in environmental water samples, and the first SPR biosensor developed for DCF detection using a hapten-protein conjugate. [Display omitted] •An SPR immunosensor was developed to detect diclofenac in water samples.•The configuration of the immunosensor involves the conjugation of diclofenac and BSA as a carrier protein.•This is the first SPR immunosensor for diclofenac that uses the target analyte conjugated to a protein.•The obtained results are comparable with the only other work published for diclofenac detection using SPR.•The development of this kind of biosensors could help to star regulating the discharge of diclofenac in water.