Surface Plasmon Resonance (SPR) Detection of Theophylline via Electropolymerized Molecularly Imprinted Polythiophenes

A facile approach to tailor-made, highly selective, and robust ultrathin sensor film for theophylline detection was demonstrated by an electropolymerized molecularly imprinted polymer (E-MIP) film of a terthiophene derivative. The method involved direct electropolymerization of the H-bond complexing terthiophene monomer. A key enabling step in sensor fabrication is the use of an electrochemically mediated washing step of the template. The formation of the E-MIP film was monitored by in situ electrochemical surface plasmon resonance (EC-SPR) spectroscopy, allowing real-time observation of the simultaneous changes in electrochemical and optical properties of the film. Surface characterization techniques for the electropolymerized films include atomic force microscopy (AFM), ellipsometry, static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance (QCM). A linear calibration curve (R = 0.994) of the E-MIP/SPR sensor for theophylline detection was obtained with a 10-50 mu M-1 range and a limit of detection (LOD) of 3.36 mu M-1 The fabricated E-MIP sensor film showed a homogeneous surface coverage, high sensitivity, long-term stability, and strong selectivity toward the imprinted template molecule. This indicated the formation of precise and stable cavities that retained the exact memory of the size, shape, and orientation of the functional groups during the templating electropolymerization steps.