Development of molecularly imprinted polymer based optical sensors for the sensitive detection of benzyl penicillin in food samples

Penicillin is one of the most commonly used beta antibiotics and has long been widely used in the treatment of various bacterial infections in humans, livestock, poultry and aquaculture. Therefore, the detection of these antibiotic residues in food and the environment is vital for the protection of public health. In this study, selective and sensitive Penicillin G (PEN-G) antibiotic detection from both aqueous solution and milk samples using molecular imprinting technique was performed by surface plasmon resonance sensor. For this purpose, PEN-G imprinted poly(2-Hydroxyethyl methacrylate-N-methacroyl-(L)-cysteine methyl ester-gold nanoparticles-N- methacryloyl-L-phenylalanine methyl ester (MIP-AuNPs) nanosensor was prepared. Control experiments were carried out via the nanosensor without the addition of AuNPs (MIP) to examine the effect of gold nanoparticles (AuNPs) incorporated to increase the surface plasmon resonance signal response. Moreover, to evaluate the imprinting efficiency, non-imprinted (NIP-AuNPs) nanosensor was designed using the same polymerization recipe except the addition of the PEN-G molecule. Characterization studies of MIP-AuNPs, NIP-AuNPs and MIP nanosensors were performed with FTIR- ATR spectrophotometer. Also, MIP-AuNPs and NIP-AuNPs nanosensors were characterized by atomic force microscopy, ellipsometer and contact angle measurements. Imprinting efficiency (I.F 7.83) for the MIP-AuNPs nanosensor was determined by comparing it with the NIP-AuNPs nanosensor. Characterization studies of MIP-AuNPs, NIP-AuNPs and MIP nanofilms were performed with FTIR-ATR spectrophotometer. Also, MIP-AuNPs and NIP-AuNPs nanosensors were characterized by atomic force microscopy, ellipsometer and contact angle measurements. Imprinting efficiency (I.F 7.83) for the MIP-AuNPs nanosensor was determined by comparing it with the NIP-AuNPs nanosensor. The MIP-AuNPs nanosensor was 9.87 times more selective for the target PEN-G molecule than amoxicillin, and 16.78-times than ampicillin. A good linear relationship was obtained for the 0.01-5 ppb concentrations range with the correlation coefficients of 0.9992 for the MIP-AuNPs nanosensor. Repeatability studies of the MIP-AuNPs nanosensor were statistically analyzed for the 0.25 ppb PEN-G, and the percent relative standard deviation of the intra-assays (RSD) of less than 1.7% indicated a negligible loss of PEN-G sensing capability after four adsorption-desorption cycles with the same sensor. In addition, the amount of PEN-G in milk selected as a real food sample was measured by spiking 5 ppb PEN-G into the milk. Validation studies were performed by high performance liquid chromatography (HPLC) studies. Keywords: gold nanoparticles, molecularly imprinted polymer, nanosensor, benzylpenicillin, surface plasmon resonance.