Determination of Estradiol by Surface Plasmon Resonance Using a Molecularly Imprinted Film

A molecularly imprinted film was incorporated on a surface plasmon resonance sensor for the determination of estradiol. The nanometer-imprinted film was synthesized by a grafting approach. First, the gold sensor chip was modified using an iniferter of N,N-diethylaminodithiocarbamoylmethylstyrene to create the grafted surface. The molecularly imprinted film was grafted on the sensor by ultraviolet light-initiated copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of estradiol as the template. The template was removed to form a molecularly imprinted film with specific recognition sites for estradiol. This approach avoided self-aggregation in solution, and grafting polymerization was confined to the chip surface. The grafting was implemented with in situ monitoring by surface plasmon resonance that provided excellent control of the film thickness. Substrate surfaces modified with and without an estradiol-imprinted film were characterized by contact-angle measurements and scanning electron microscopy. The estradiol-imprinted film was incorporated on a surface plasmon resonance sensor for the determination of estradiol from 10⁻¹⁰ to 10⁻⁶ mol/L in phosphate-buffered saline. The lowest determined concentration was 10⁻¹⁰ mol/L. Testosterone was used as an analog; suitable selectivity and specificity were obtained for the determination of estradiol. Furthermore, this sensor possessed high reproducibility for analytical measurements.