Molecularly imprinted poly(diaminonaphthalene)/zinc oxide nanocomposite on Au/rGO for tobramycin detection: a...

Tobramycin (Tob) is used to treat serious infectious diseases, so careful monitoring of its concentration through a sensor that can detect small quantities of Tob in medicines and food is essential. Herein, novel molecularly imprinted (MI) poly(1,5-diaminonaphtalene)/zinc oxide (PDan/ZnO)) nanocomposite sensor with Tob recognition sites based on reduced graphene oxide modified gold electrode (Au/rGO) as molecular imprinted polymer nanocomposite (MIPN) was fabricated by in situ electropolymerization method. Besides MIPN, non-molecular imprinted polymer nanocomposite (Au/rGO/PDan/ZnO) as N-MIPN electrode was constructed and compared with MIPN. The N-MIPN and MIPN electrodes were characterized by physicochemical and electrochemical methods. To improve the performance and optimization of MIPN sensor during nanocomposite growth on the Au/rGO surface, atomic force microscopy (AFM), and field - emission scanning electron microscopy (FE-SEM) techniques were employed. The results revealed that among MIPN electrodes with various polymer nanocomposite thicknesses, MIPN-8 (8: number of growth cycle) by taking advantage of significant morphological properties including optimum height quantities distribution, non-typical surface texture, and remarkable roughness and fractal dimension (D_f) offered the optimum performance. To assess the detection capabilities of the developed MIPN-8 sensor, differential pulse voltammetry (DPV) measurements were carried out using varying concentrations of Tob under optimal conditions. The electrochemical MIPN-8 sensor exhibited a high sensitivity toward Tob with a limit of detection (LOD) of 4.210 × 10^-15 mol. L^-1 and limit of quantification (LOQ) of 1.276 × 10^-14 mol. L^-1. The selectivity of the sensor for Tob was around 2.34, 2.65, 7.42, 7.31, and 8.02 times more than that of Gentamicin (GM), Kanamycin (KAN), Chlortetracycline Hydrochloride (CTCH), Oxytetracycline Hydrochloride (OTCH), and Ziprasidone Hydrochloride (ZIP) antibiotics, respectively. The selectivity of the MIPN for the detection of the interference substances including the above antibiotics was examined. The MIPN-8 sensor showed good reproducibility with a relative standard deviation (RSD) of 1.59%. The MIPN-8 sensor performances for real samples, e.g., eye drops, chicken egg, and milk were investigated. Finally, the specific Gibbs binding energies and binding interactions of the MIPN-8 sensor with Tob target were studied by molecular dynamic (MD) simulation and the energy of adsorption was ∆G = - 11.47 ± 3.71 kCal.mol^-1 and for desorption was ∆G = - 7.56 ± 6.71 kCal.mol^-1.