Evaluation of theophylline imprinted polypyrrole film

• Affinity properties of theophylline imprinted (MIP) polypyrrole (Ppy) film were evaluated.
• The equilibrium constant Kd of MIP–Ppy/theophylline was determined.
• Gibbs free energy change (ΔG°) of MIP–Ppy/theophylline complex dissociation was calculated.

In this study some affinity and dielectric properties of molecularly imprinted (MIP) conducting polymer—polypyrrole (Ppy) based thin films were evaluated. Films of polypyrrole molecularly imprinted with theophylline (MIP–Ppy) and non-imprinted polypyrrole (NIP–Ppy) were formed on boron doped silicon (Si) substrates in order to evaluate the efficiency of Ppy to bind theophylline. The substrates were modified with boron-doped oxygen terminated nanocrystalline diamond (B:NCD:O) The dielectric properties of B:NCD:O/Ppy-based multi-layered structures were analyzed using spectroscopic ellipsometry and spectrophotometric techniques. Electrochemical impedance spectroscopy was applied for the investigation of kinetics of theophylline interaction with MIP–Ppy and NIP–Ppy. The sensitivity of molecularly imprinted and non-imprinted polymer films was analyzed by injection of different theophylline concentrations. Assuming that Ppy film electrical capacitance change is a result of Ppy dielectric constant change induced by absorbed theophylline molecules, the electrical capacitance change (ΔC) kinetics at different concentrations of theophylline was analyzed using first pseudo order kinetic equation. The dissociation equilibrium constant KD of MIP–Ppy/theophylline complex at room temperature was calculated as 1.7 × 10−8 M, and Gibbs free energy change (ΔG) of MIP–Ppy/theophylline complex formation was calculated as −43.5 kJ/mol. It was concluded that molecularly imprinted polypyrrole thin film could be used for the detection of theophylline.

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