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Öğe A Bottom-Up Approach for Developing Aptasensors for Abused Drugs: Biosensors in Forensics(Mdpi, 2019) Aydindogan, Eda; Balaban, Simge; Evran, Serap; Coskunol, Hakan; Timur, SunaAptamer-based point-of-care (POC) diagnostics platforms may be of substantial benefit in forensic analysis as they provide rapid, sensitive, user-friendly, and selective analysis tools for detection. Aptasensors have not yet been adapted commercially. However, the significance of the applications of aptasensors in the literature exceeded their potential. Herein, in this review, a bottom-up approach is followed to describe the aptasensor development and application procedure, starting from the synthesis of the corresponding aptamer sequence for the selected analyte to creating a smart surface for the sensitive detection of the molecule of interest. Optical and electrochemical biosensing platforms, which are designed with aptamers as recognition molecules, detecting abused drugs are critically reviewed, and existing and possible applications of different designs are discussed. Several potential disciplines in which aptamer-based biosensing technology can be of greatest value, including forensic drug analysis and biological evidence, are then highlighted to encourage researchers to focus on developing aptasensors in these specific areas.Öğe Doping amaçlı kullanılan maddelerin analizine yönelik yenilikçi elektrokimyasal biyosensör sistemlerinin geliştirilmesi(Ege Üniversitesi, Fen Bilimleri Enstitüsü, 2020) Balaban, Simge; Timur, SunaTez çalışmasında doping maddelerinin yerinde analizine imkan sunabilecek test kitlerinin tasarlanması ve kromatografik metotlarla doğrulama yapılabilmesi için metot optimizasyonu yapılması hedeflenmiştir. Uygun yüzey kimyası kullanılarak model olarak seçilen dehidroepiandrosteron 3-sülfat (DHEA-S) doping maddesine yönelik, yenilikçi biyosensör metodolojileri için test yüzeyi oluşturulmuştur ve doping standardının teste uygulanması ile çalışma performansları araştırılmıştır. DHEA-S biyosensör sistemi olarak tez kapsamında antikor temelli bir elektrokimyasal biyosensör sistemi geliştirilmiştir. Elektrokimyasal biyosensör sistem için altın elektrotlar kullanılmıştır. Elektrot yüzeyleri ilk olarak sisteamin ile kaplanmış ardından çapraz bağlayıcı olarak glutaraldehit kullanımı ile DHEA antikorları yüzeye immobilize edilmiştir. Modifikasyon adımları, elektrokimyasal teknikler ile görüntülenmiş ve onaylanmıştır. Biyosensör sistemi için lineer çalışma aralığı 2,5-100 ng/mL olarak, dedeksiyon limiti (LOD) ise 3,971 ng/mL olarak belirlenmiştir. Geliştirilen biyosensörün seçimliliğinin belirlenmesi için kolesterol, DHEA, bovin serum albümin gibi girişimci moleküller kullanılmıştır. Ayrıca, sentetik serum ve idrar numunelerinde standart katma yöntemi ile denemeler gerçekleştirilmiş ve başarılı sonuçlar elde edilmiştir. Seçilen doping maddesinin analizinin gerçekleştirilmesi amacıyla pratik, yenilikçi, uygun maliyetli, portatif olarak tasarlanmış olan biyosensör sistemi tez çalışmasının çıktılarını oluşturmaktadır.Öğe An Electrochemical Biosensor Platform for Testing of Dehydroepiandrosterone 3-Sulfate (DHEA-S) as a Model for Doping Materials(Wiley-V C H Verlag Gmbh, 2019) Balaban, Simge; Durmus, Ceren; Aydindogan, Eda; Gumus, Zinar Pinar; Timur, SunaEndogenous steroids such as dehydroepiandrosterone (DHEA) and dehydroepiandrosterone 3-sulfate (DHEA-S) have commonly used as doping materials by athletes and to date novel techniques are needed for detection of these molecules. In this study, antibody-based electrochemical biosensor has developed for testing level of the DHEA-S. For this aim, gold surfaces were initially modified with cysteamine (Cys) and then, DHEA-S antibody was immobilized on the surface via glutaraldehyde (GA) as a crosslinking agent. The stepwise modification of electrode surface was monitored by using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Linear range was determined as 2.5-100 ng/mL DHEA-S using differential pulse voltammetry (DPV) technique, as well. Moreover, repeatability (+/- S.D.), coefficient of variation (%) and limit of detection (LOD) values were calculated as 0.033, 1.030 and 3.971, respectively. Also, DHEA-S in synthetic serum and urine samples were successfully determined with standard addition method and confirmation analysis were performed with liquid chromatography quadrupole-time of flight mass spectrometry (LC-QTOF/MS) system. The selectivity was studied with the addition of some interfering molecules (testosterone, bovine serum albumin (BSA), cholesterol, uric acid, lactic acid, codein (COD), ascorbic acid, DHEA). Consequently, this work is proposed as practical, innovative and cost-effective technique that can be easily adapted for the miniaturized form for the analysis of other doping substances as well as DHEA-S for the future works.Öğe An Electrochemical Biosensor Platform for Testing of Dehydroepiandrosterone 3-Sulfate (DHEA-S) as a Model for Doping Materials(Wiley-V C H Verlag Gmbh, 2020) Balaban, Simge; Durmus, Ceren; Aydindogan, Eda; Gumus, Zinar Pinar; Timur, SunaEndogenous steroids such as dehydroepiandrosterone (DHEA) and dehydroepiandrosterone 3-sulfate (DHEA-S) have commonly used as doping materials by athletes and to date novel techniques are needed for detection of these molecules. In this study, antibody-based electrochemical biosensor has developed for testing level of the DHEA-S. For this aim, gold surfaces were initially modified with cysteamine (Cys) and then, DHEA-S antibody was immobilized on the surface via glutaraldehyde (GA) as a crosslinking agent. The stepwise modification of electrode surface was monitored by using various electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Linear range was determined as 2.5-100 ng/mL DHEA-S using differential pulse voltammetry (DPV) technique, as well. Moreover, repeatability (+/- S.D.), coefficient of variation (%) and limit of detection (LOD) values were calculated as 0.033, 1.030 and 3.971, respectively. Also, DHEA-S in synthetic serum and urine samples were successfully determined with standard addition method and confirmation analysis were performed with liquid chromatography quadrupole-time of flight mass spectrometry (LC-QTOF/MS) system. The selectivity was studied with the addition of some interfering molecules (testosterone, bovine serum albumin (BSA), cholesterol, uric acid, lactic acid, codein (COD), ascorbic acid, DHEA). Consequently, this work is proposed as practical, innovative and cost-effective technique that can be easily adapted for the miniaturized form for the analysis of other doping substances as well as DHEA-S for the future works.Öğe in vitro Selection of Aptamer for Imidacloprid Recognition as Model Analyte and Construction of a Water Analysis Platform(Wiley-V C H Verlag Gmbh, 2020) Bor, Gulsah; Man, Ezgi; Ugurlu, Ozge; Ceylan, Ayse Elcin; Balaban, Simge; Durmus, Ceren; Timur, SunaPesticide use in agriculture is one of the threats to water safety. Therefore, detection of pesticide residues is crucial for human health. Compared to conventional chromatographic methods, aptasensors are promising tools for fast, cheap and sensitive detection of environmental contaminants. To the best of our knowledge, such an aptasensor has not been reported for imidacloprid (Imi) which is one of the most widely used pesticides. in order to meet this demand, we initially selected two novel aptamers designated as 'Apta-1' and 'Apta-2' by graphene oxide-SELEX (GO-SELEX) method. Then, these aptamers were used to fabricate the gold electrode-based aptasensor platforms and characterized by using electrochemical methods such as cyclic voltammetry, and electrochemical impedance spectroscopy as well as X-Ray photoelectron spectroscopy. It was found that the limit of detection value of Apta-1 based sensor for the Imi was found better than Apta-2 based system, although linear ranges were similar. Based on that finding, Apta-1 based system was further tested against possible interference molecules. the proposed platform was successfully used for detection of very low concentrations of Imi in the range of ng/mL. Thus, it eliminates the need for sample pre-treatment and enables a practical analysis in real wastewater samples.Öğe Laser-scribed Graphene Electrodes as an Electrochemical Immunosensing Platform for Cancer Biomarker 'eIF3d'(Wiley-V C H Verlag Gmbh, 2021) Balaban, Simge; Beduk, Tutku; Durmus, Ceren; Aydindogan, Eda; Salama, Khaled Nabil; Timur, SunaeIF3d is a protein biomarker which has a potential for the diagnosis of various cancers. Herein, a bio-platform was constructed for eIF3d sensing by using LSG and surface functionalization with anti eIF3d antibody via EDC/NHS chemistry. Following the surface modifications, XPS and several electrochemical methods were used. Difference in the signals were related to biomarker amounts between 75-500 ng/mL. LOD was calculated as 50.4 ng/mL. Selectivity of biosensor was tested by using of various interference molecules. EIF3d was also successfully detected in synthetic biological samples. Thus, to the best of our knowledge, this study is one of the rare studies on use of LSGs in immunosensor studies.Öğe Sensor Platform with a Custom-Tailored Aptamer for Diagnosis of Synthetic Cannabinoids(Wiley-V C H Verlag Gmbh, 2020) Balaban, Simge; Man, Ezgi; Durmus, Ceren; Bor, Gulsah; Ceylan, Ayse Elcin; Gumus, Z. Pinar; Timur, SunaSynthetic cannabinoids (SCs) are the large group of abused drugs and detection of them is still a challenge. Hence, new methods for analysis of SCs are being investigated. We aimed to develop a novel system for selective analysis of SCs. First, various custom-tailored aptamers against the target SCs were selected through GO-SELEX process. Toggling between different SC analytes during successive rounds of selection was performed to generate cross-reactive aptamers. Then, the amino-capped aptamers were synthesized and easily attached to the cysteamine-covered gold electrodes. Analytical parameters and selectivity of the aptasensors were compared by using electrochemical techniques. After comparison of the analytical features and selectivity towards target analytes, one of the aptamers designated as Apta-1 was chosen for further measurements. the aptasensor was tested by using differential pulse voltammetry technique against JWH-018 (5-pentanoic acid), selected as a model for SCs. the linearity and limit of detection were determined as 0.01-1.0 ng/mL and 0.036 ng/mL. Finally, sample application in synthetic urine samples was successfully performed with standard addition method, as confirmed by LC-QTOF/MS. JWH-018 (4-hydroxypentyl), JWH-073 (3-hydroxybutyl), JWH-250 (5-hidroxypentyl) and HU-210 were used to test the selectivity of the aptasensor and the system was shown to recognize all these SCs. Also other illegal drugs did not significantly interfere with the signal responses.