z Materials Science inc. Nanomaterials & Polymers Surface Plasmon Resonance Nanosensors for Detecting Amoxicillin in Milk Samples with Amoxicillin Imprinted Poly (hydroxyethyl methacrylate-N-methacryloyl-(L)- glutamic acid) Sona Faalnouri, Duygu Çimen, Nilay Bereli, and Adil Denizli* [a] In this study, SPR based nanosensors were prepared for the detection of amoxicillin (AMOX) in milk samples with using molecular imprinting technique. This study developed to determine the amoxicillin (AMOX) from the commercial and local milk samples. For determination of amoxicillin, polymeric film and nanoparticles consisting of poly(hydroxyethyl meth- acrylate-N-methacryloyl-(L)- glutamic acid) were synthesized onto the surface of the SPR chip by ultra violet polymerization. The characterization of the polymeric film and nanoparticles were determined by zeta sizer, ellipsometry, contact angle and atomic force microscopy measurements. The range of linearity was measured as 0.1-200ng/mL for amoxicillin (AMOX) imprinted polymeric film and nanoparticles based SPR nano- sensors. The limit of detection for AMOX imprinted polymeric film and nanoparticles based SPR nanosensors were found as 0.0012 ng/mL and 0.0009 ng/mL, respectively. To show the selectivity of surface plasmon resonance nanosensors compet- itive adsorption of amoxicillin (AMOX), ampicillin (AMP), cephalexin (CEP) and cholesterol (KOL) were investigated. According to the results, AMOX imprinted SPR nanosensors have exhibited low-detection limit, high sensitivity and selectiv- ityfordetectionofantibioticinmilksamples. 1. Introduction Antibiotics are antimicrobial drugs used to kill or prevent the growth of bacterias. [1,2] Amoxicillin (AMOX) is a semi-synthetic antibiotic used to treat many bacterial infections. Amoxicillin has also been described as an antibiotic with higher absorption in humans and animals. [3–6] Improper use of antibiotics leads to residues in foodstuffs. According to European Union maximum residue limit of amoxicillin for milk is 4.0 μg/kg. [7] It is very substantial to detect antibiotic residues both in water and in daily consumption products such as meat, milk and eggs. [8–14] Analytical methods such as spectroscopy, [15,16] chromatography [17,18] and electrochemical methods [19,20] have beenusedtodeterminetheamountofantibiotics.Someofthe methods used for the determination of antibiotics are very accurate and sensitive, but also have the disadvantages of being routine in control procedures. Therefore, it is important to find an easy method for the determination of antibiotics in food samples to be precise and specific. Molecularly imprinted polymer (MIP) method employs a functional monomer and a cross-linker, making the polymerization surrounding the mold molecule in the solvent. [21–23] The objective of the MIP technique is to specific regions for target molecule in the polymer and therefore increase the selectivity of the molecule. [24,25] Due to these superior properties, MIP method is widely used in many different fields such as separation, drug and chemical determination, catalysis based on sensor. [26,27] Sensors produced from molecularly printed polymers have been widely used in recent years due to their selectivity and specificity. [28] Sensors are an analytical device that converts a measurable signal directly proportional to chemical concen- trations with the physical converter suitable for biological active elements. Sensors are used in different areas such as public health, environmental activities and food safety. [29–31] Amoxicillin imprinted polymeric film and nanoparticles consist- ing of poly(hydroxyethyl methacrylate-N-methacryloyl-(L)-glu- tamic acid) poly(HEMAGA) were prepared for the determination of amoxicillin in the milk samples. Therefore, both AMOX imprinted polymeric film and nanoparticles were prepared by molecular imprinting (MIP) method. The size of amoxicillin imprinted poly(HEMAGA) nanoparticles were characterized by zeta-sizer and atomic force microscopy (AFM) and than were dropped onto the SPR chip surface by ultraviolet polymer- ization. Characterization of SPR nanosensors was performed by atomic force microscopy (AFM), ellipsometer and contact angle measurements. The isotherm models were applied to exper- imental data to examine the interaction between AMOX and the AMOX imprinted SPR nanosensors. Also, kinetic studies were performed with amoxicillin (AMOX), ampicillin (AMP), cephalexin (CEP) and cholesterol (KOL) solutions to determine the selectivity of AMOX imprinted SPR nanosensors. Amoxicillin was determined for both local and commercial milk samples by using AMOX imprinted SPR nanosensors. [a] S. Faalnouri, D. Çimen, N. Bereli, Prof. Adil Denizli Hacettepe University, Department of Chemistry, Beytepe, Ankara, Turkey Tel: + 903122977983 Fax: + 903122992163 E-mail: denizli@hacettepe.edu.tr Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.202000621 ChemistrySelect Full Papers doi.org/10.1002/slct.202000621 4761 ChemistrySelect 2020, 5,4761–4769 ©2020Wiley-VCHVerlagGmbH&Co.KGaA,Weinheim