Yüzey Plazmon Rezonans (SPR) Temelli Aflatoksin Sensörlerin Hazırlanması

Abstract

Mycotoxins are toxic metabolites produced by various groups of fungi that pollute different types of agricultural products before and after harvest storage. Aflatoxins (AFs) are mycotoxins that harm human and animal health. AFs are highly toxic and carcinogenic secondary metabolites that are naturally produced by fungi species, especially Aspergillus flavus and Aspergillus parasiticus. AFs display mutagenic, teratogenic and highly hepatotoxic and hepatocarcinogenic effects. It is categorized as a Group I carcinogen by the International Agency for Research on Cancer (IARC). AFs are divided into various types; aflatoxin B1, B2, M1 and M2. Aflatoxin B1 (AFB1) is very common in agricultural products and has the highest toxicity among aflatoxins. Aflatoxin M1 (AFM1), the hydroxylated metabolite of AFB1, is found in animal tissues and liquids (milk and urine). Due to their extremely high toxicity and carcinogenicity, control of maximum aflatoxin residue levels in foodstuffs is carried out by many countries. Aflatoxins are high risk mycotoxins and therefore significant research should be conducted on a wide variety of analytical and high-precision assay techniques that can be useful and practical. Label free optical biosensors are an interesting option for the detection of many analytes because they offer several advantages such as high sensitivity, direct and real-time measurement. Since sensor response is related to the size of the analyte, immobilization strategies have recently been developed to overcome some limitations in this area by designing label free optical sensors for small molecules. The surface plasmon resonance (SPR) sensor system is a powerful optical-based tool for monitoring biomolecular interactions. SPR-based biosensors are widely used to simple and directly detection biospecific interactions in real time without chemical labeling. Molecular imprinting technology was first proposed by Wulff and Sarhan in 1972. The technology includes polymerization around a template molecule followed by removal of the template from the respective matrices to leave selective recognition sites. Molecularly imprinted polymers have been used in many scientific and technical fields as molecular recognition materials due to their stability, cost effective, high affinity and superior substrate recognition capabilities and ease of preparation. In this thesis, molecularly imprinted based surface plasmon resonance (SPR) nanosensors have been prepared for fast and sensitive detection of AFB1 and AFM1 in food. A sensitive and selectively imprinted optical sensor for the detection of AFB1 and AFM1 was prepared by embedding modification of gold nanoparticles (AuNPs) on the gold chip surface and designing a thin imprinted polymer film. Low molecular weight mycotoxins were detected by enhanced the sensitivity of the polymer film conjugated with gold nanoparticles. N-methacryloyl-L-phenylalanine (MAPA) as a functional monomer is utilized in the polymer film based on poly(2-hydroxyethyl methacrylate). The effectiveness of the gold nanoparticles amplification strategy is discussed. Highly sensitive detection of AFB1 and AFM1 in milk for ~8 minutes analysis time was performed in the SPR nanosensor. The detection limit (LOD) values determined for AFB1 and AFM1 were 1.04 pg.mL-1 and 0.4 pg.mL-1, respectively. Also, AFB1 determination was carried out in corn and peanut samples contaminated with AFB1. In a random dairy farmer milk and raw milk samples, AFM1 determination was performed. Repeatability and storage stability of the aflatoxin imprinted sensors were investigated. The polymer film of the designed chips was calculated using Scatchard, Langmuir, Freundlich and Langmuir-Freundlich adsorption isotherms to determine the surface homogeneity. Adsorption behavior in both AFB1 and AFM1 imprinted nanofilm-coated chips was found to fit with the Langmuir model.