Preparation and characterization of molecular imprinted polymers for determination of melatonin

Melatonin is an effective hormone against diseases such as the immune system, cancer, and depressive syndromes. It also helps regulate the neuroendocrine system and the sleeping pattern. Melatonin and its analogues are also widely used in cosmetics as moisturizing, anti-wrinkle, actinic damage inhibitor. At the same time, the extraction of melatonin from natural sources with high purity and selectivity by a fast, low-cost method becomes very important, especially due to its use in the medical and cosmetic industries. Several quantitative assay methods such as radioimmunological method (RIA), enzyme-mediated immunosorbent assay (ELISA), high performance liquid chromatography (HPLC) with electrochemical and fluorescence detector and gas chromatography-mass spectrometry (GC-MS) are used for melatonin. Liquid-liquid extraction is extensively used in extractions of melatonin in plants. However, because of the low yield in liquid-liquid extraction, solid phase extraction is more advantageous than other extraction methods because it has properties such as high sample volume, easy analyte retrieval, high recovery, fast sample loading, low organic solvent requirement. The sorbent to be used as the solid phase sorbent should have properties such as quantitative adhesion, desorption, high capacity, renewability and easy availability. Due to these properties, molecularly imprinted polymers have been used in biomedical and biotechnology applications in recent years. For this purpose, a novel affinity sorbent [poly (ethylene glycol dimethacrylate-N-methacryloyl-L-tryptophan methyl ester) (p (EGDMA-MATRP) microspheres] for the determination and extraction of melatonin was first developed using ethylene glycol dimethacrylate (EGDMA) and N-methacryloyl-L-tryptophan methyl ester (MATrp) monomers. The adsorption parameters (temperature, time, pH, initial concentration etc.) were determined using p (EGDMA-MATrp) microspheres characterized by Fourier Transfer Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Differential Thermal Analysis- Thermo-Gravimetric Analysis (DTA-TGA) were optimized. Re-usability was determined by determining the appropriate desorption agent for desorption of adsorbed melatonin in the developed sorbent. Applicability of the developed sorbentine lime melatonin for extraction before extraction by high performance liquid chromatography (HPLC) was determined.