Browsing by Author "Turan, Eylem"

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Construction of a Sensitive and Selective Plasmonic Biosensor for Prostate Specific Antigen by Combining Magnetic Molecularly-Imprinted Polymer and Surface-Enhanced Raman Spectroscopy
(Elsevier, 2022) Turan, Eylem; Zengin, Adem; Suludere, Zekiye; Kalkan, Nurhan Onal; Tamer, Ugur
Selective and sensitive detection of cancer biomarkers in serum samples is critical for early diagnosis of cancer. Prostate specific antigen is an important biomarker of prostate cancer, which ranks high among cancer-related deaths of men over 50 years old. Herein, a novel analytical method was introduced for detection of PSA by combining high selectivity of molecularly-imprinted polymers and high sensitivity of surface-enhanced Raman spectroscopy (SERS). Firstly, magnetic nanoparticles were grafted with an imprinted layer by using tannic acid as a functional monomer, diethylenetriamine as a cross-linker and prostate specific antigen as a template molecule. Detailed surface characterization and re-binding experiment results indicated that the imprinting of the antigen was successful with an imprinting factor of 5.58. The prepared magnetic molecularly imprinted polymers (MMIPs) were used as an antibody-free capture probe and labeled with gold nanoparticles that were modified with anti-PSA and a Raman reporter, namely 5,5'-dithiobis-(2-nitrobenzoic acid). Thus, a plasmonic structure (sandwich complex) was formed between MMIP and the SERS label. The limit of detection and limit of quantification of the designed sensor were 0.9 pg/mL and 3.2 pg/mL, respectively. The sensor also showed high recovery rates (98.0-100.1% for healthy person and 99.0-101.3% for patient) with low standard deviations (less than 4.3% for healthy person and less than 3.3% for patient) for PSA in serum samples. Compared with the traditional immunoassays, the proposed method has several advantages like low cost, reduced detection procedure, fast response, high sensitivity and selectivity. It is believed that the proposed method can be potentially used for selective and sensitive determination of tumor marker of prostate cancer in clinical applications.
A Fluorescent Artificial Receptor With Specific Imprinted Cavities To Selectively Detect Colistin
(Springer Heidelberg, 2020) Turan, Eylem; Zengin, Adem
A novel and facile fluorescent artificial receptor on the basis of the molecularly imprinted polymer-coated graphene quantum dots was engineered successfully to detect colistin. The colistin imprinted graphene quantum dots (CMIP-GQDs) was synthesized by vinyl-based radical polymerization between functional monomers and crosslinker at around the template molecule on the surface of graphene quantum dots. The size of bare, CNIP-GQDs, and CMIP-GQDs was about 4.8 +/- 0.6 nm, 18.4 +/- 1.7 nm, and 19.7 +/- 1.3 nm, respectively. The CMIP-GQDs, which showed the strong fluorescence emission at 440 nm with the excitation wavelength fixed at 380 nm, had excellent selectivity and specificity to rapidly recognize and detect colistin. The linear range of fluorescence quenching of this fluorescent artificial receptor for detection colistin was 0.016-2.0 mu g mL(-1) with a correlation coefficient (R-2) of 0.99919, and the detection limit was 7.3 ng mL(-1) in human serum samples. The designed receptor was successfully applied to detect colistin in human serum samples and it achieved excellent recoveries shifted from 93.8 to 105%.
Selective Extraction and Determination of Citrinin in Rye Samples by a Molecularly Imprinted Polymer (Mip) Using Reversible Addition Fragmentation Chain Transfer Precipitation Polymerization (Raftpp) With High-Performance Liquid Chromatography (Hplc) Detection
(Taylor & Francis inc, 2021) Meydan, Ismet; Bilici, Mustafa; Turan, Eylem; Zengin, Adem
Citrinin (CIT) is a mycotoxin naturally in many foods that causes carcinogenic and mutagenic effects in the human body. A novel method was developed for the selective quantification of citrinin in rye samples. Citrinin-imprinted spheres were fabricated through reversible addition fragmentation chain transfer (RAFT) precipitation polymerization (RAFTPP) in the presence of 2-hydroxymethacrylate (HEMA, functional monomer), ethylene glycol dimethacrylate (EGDMA, cross-linker), citrinin (template), 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CTA, RAFT agent), azobisisobutyronitrile (AIBN, initiator), and acetonitrile (ACN, porogen). The imprinted polymers were shown to be spherical with a high surface area and a porous structure. The rebinding properties of citrinin to the imprinted spheres were also examined in detail. The maximum adsorption capacity, equilibration time, and imprinting factor were 38.6 mg g(-1), 90 min, and 3.89, respectively. In addition, the citrinin-imprinted spheres were regenerated at least 10 times without change in the adsorption capacity. The citrinin-imprinted particles were used to selectively remove and determine the analyte in rye extract. The calibration relationship was linear between 1 and 100 mu g kg(-1) with a limit of detection of 0.35 mu g kg(-1). The method also had high recoveries (98 to 100.0%) and low relative standard deviations (less than 4.1%). Therefore, the imprinted spheres are suitable for the selective determination of citrinin in rye extracts.
Surface Molecularly-Imprinted Magnetic Nanoparticles Coupled With Sers Sensing Platform for Selective Detection of Malachite Green
(Elsevier Science Sa, 2020) Ekmen, Elvan; Bilici, Mustafa; Turan, Eylem; Tamer, Ugur; Zengin, Adem
Herein, a novel analytical method was reported for sensitive and selective quantification of malachite green (MG) in tap water and carp samples based on a combination of surface-enhanced Raman spectroscopy (SERS) and molecular imprinting technology. For this purpose, surface molecularly-imprinted magnetic nanoparticles (MIP@Fe3O4 NPs) were synthesized through recently developed living/controlled radical polymerization mechanism referred to as reversible chain transfer catalyzed polymerization (RTCP). Surface characterization of MIP@Fe3O4 NPs was carried out in detail by using the combination of several analytical techniques and the results showed the presence of a thin polymer layer on the nanoparticles. Rebinding properties, selectivity and reusability of the nanoparticles were investigated and the obtained results indicated the prepared nanoparticles had excellent selectivity, high adsorption capacity, fast adsorption kinetics and multiple-uses with an imprinting factor of 3.86. Then, silver dendrites (Ag NPs) were deposited on silicon wafers and used as SERS sensing platform. Moreover, surface properties of the SERS substrate were also investigated in detail in terms of stability, reusability and homogeneity. After that, the eluted MG from the imprinted nanoparticles was dropped on the sensing platform and SERS analysis was carried out. Under optimized conditions, limit of detection and limit of quantification were determined to be 1.50 pM and 4.96 pM for tap water, respectively and 1.62 pM and 5.38 pM for carp samples, respectively within acceptable recovery rates and standard deviations. The overall results indicated that the proposed method can be effectively used for the quantification of trace amounts of MG in tap water and carp samples. Moreover, the proposed method is promising for development of new ways to prepare MIPs via surface-initiated RTCP.