Estradiol detection in water samples related to aquaculture exploiting plasmonic spoon-shaped biosensors.

A polymeric multimode waveguide, characterized by a pioneering spoon-shaped geometry and featuring a built-in measuring cell [1], was herein proposed to devise a Surface Plasmon Resonance (SPR) platform to monitor the specific receptor-analyte interaction for estradiol identification in water samples. The fabrication process to realize the biosensor consists of two steps. At first, a gold deposition on the spoon-shaped waveguide surface was realized through a sputter coater machine to obtain the SPR platform. Then, the functionalization of the SPR sensitive surface with a specific estrogen receptor (αER), able to recognize the estradiol, was performed through an immobilization process of the receptor to a Self-Assembled Monolayer (SAM) produced on the gold surface. The biosensor response performances were tested in physiological conditions (phosphate buffer, 10 mM, pH 7.4) and in different real water matrices related to fish aquaculture (freshwater and seawater). The estradiol concentration was monitored in all matrices between 360 fM – 36 nM. A limit of detection (LOD) equal to about 0.1 pM was obtained for all the explained conditions. The proposed biosensor experimentally tested showed a high sensitivity for the detection of low concentrations of analyte, and the comparison between the parameters obtained for the measurements in different matrices demonstrated that the matrix variation did not significantly influence the platform’s response. As a result, the experimental outcomes supported the possibility of using the αER-based biosensor for the quantitative determination of estradiol in different real water samples (freshwater and seawater) in the range of concentration requested by a real scenario, without any sample pre-treatment (i.e. preconcentration or extraction).