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Öğe A review of aptamer-conjugated nanomaterials for analytical sample preparation: Classification according to the utilized nanomaterials(Elsevier B.V., 2024) Uğurlu, Özge; Man, Ezgi; Gök, Oğuz; Ülker, Gözde; Soytürk, Hakan; Özyurt, CananBackground: Sample extraction before detection is a critical step in analysis. Since targets of interest are often found in complex matrices, the sample can not be directly introduced to the analytical instrument. Nanomaterials with unique physical-chemical properties are excellent supports for use in sorbent-based extraction. However, they lack selectivity and thus need to be functionalized with target-capturing molecules. Antibodies and molecularly imprinted polymers (MIPs) can be used for this purpose, but they have some problems that limit their practical applications. Hence, functionalization of nanomaterials for selectivity remains a problem. Results: Nucleic acid aptamers are affinity reagents that can provide superiority to antibodies since they can be selected in vitro and at a lower cost. Moreover, aptamers can be chemically synthesized and easily modified with different functional groups. Hence, aptamers are good candidates to impart selectivity to the nanomaterials. Recent studies focus on the integration of aptamers with magnetic nanoparticles, carbon-based nanomaterials, metal-organic frameworks, gold nanoparticles, gold nanorods, silica nanomaterials, and nanofibers. The unique properties of nanomaterials and aptamers make the aptamer-conjugated nanomaterials attractive for use in sample preparation. Aptamer-functionalized nanomaterials have been successfully used for selective extraction of proteins, small molecules, and cells from different types of complex samples such as serum, urine, and milk. In particular, magnetic nanoparticles have a wider use due to the rapid extraction of the sample under magnetic field. Significance: In this review, we aim to emphasize how beneficial features of nanomaterials and aptamers could be combined for extraction or enrichment of the analytes from complex samples. We aim to highlight that the benefits are twofold in terms of selectivity and efficiency when employing nanomaterials and aptamers together as a single platform.Öğe An ultrasensitive and disposable electrochemical aptasensor for prostate-specific antigen (PSA) detection in real serum samples(Springer Science and Business Media Deutschland GmbH, 2023) Özyurt, Canan; Uludağ, İnci; Sezgintürk, Mustafa KemalIn this study, we constructed a disposable indium tin oxide polyethylene terephthalate film (ITO-PET)-based electrochemical aptasensor for analyzing prostate-specific antigen (PSA), one of the most important biomarkers of prostate cancer. Because of their clinical importance, building PSA biosensing systems with high sensitivity and stability is essential. However, it still presents significant difficulties, such as low detection limits. We designed a platform to covalently bind the amino-terminated aptamer by modifying the ITO-PET surface with carboxyethylsilanetriol (CTES) to obtain a self-assembled monolayer (SAM). We also evaluated the potential for use in real human serum samples by investigating the optimal operating conditions and analytical performance characteristics of the developed biosensor. The design we present here exhibits excellent precision, with a limit of detection (LOD) as low as 8.74 fg/mL PSA. The broad linear detection range of the biosensor under optimal conditions was determined as 1.0-1500 fg/mL. The dissociation constant (Kd) for the aptamer was also calculated as 46.28 ± 5.63 nM by evaluating the impedimetric response as a function of PSA concentration. The aptasensor displayed considerable repeatability (1.3% RSD) and reproducibility (7.51% RSD) and good storage stability (98.34% of the initial activity for 8 weeks). Additionally, we demonstrated that the technique we developed was quite efficient in estimating the kinetics of aptamer-analyte interactions by determining the Kd and single-frequency impedance (SFI) data. In conclusion, we proposed a selective and sensitive biosensor with the potential for clinical application and superior performance in real serum samples.Öğe Biosensing strategies for diagnosis of prostate specific antigen(Elsevier B.V., 2022) Özyurt, Canan; Uludağ, İnci; Sezgintürk, Mustafa KemalAlmost from the time of its discovery, the prostate specific antigen (PSA) has been one of the most accurate and most extensively studied indicators of prostate cancer (PC). Because of advancements in biosensing systems and technology, PSA analysis methods have been substantially updated and enhanced as compared to their first instances. With the development of techniques in biosensor technology, the number of PSA biosensors that can be used in the biomedical sector is increasing year by year. Many different recognition elements and transducers have been used in the development of biosensor systems that exhibit high sensitivity, selectivity, and specificity. Here in this review, we provide a current overview of the different approaches to PSA detection.Öğe Lab-on-a-chip systems for cancer biomarker diagnosis(Elsevier B.V., 2023) Özyurt, Canan; Uludağ, İnci; İnce, Bahar; Sezgintürk, Mustafa KemalLab-on-a-chip (LOC) or micro total analysis system is one of the microfluidic technologies defined as the adaptation, miniaturization, integration, and automation of analytical laboratory procedures into a single instrument or “chip”. In this article, we review developments over the past five years in the application of LOC biosensors for the detection of different types of cancer. Microfluidics encompasses chemistry and biotechnology skills and has revolutionized healthcare diagnosis. Superior to traditional cell culture or animal models, microfluidic technology has made it possible to reconstruct functional units of organs on chips to study human diseases such as cancer. LOCs have found numerous biomedical applications over the past five years, including integrated bioassays, cell analysis, metabolomics, drug discovery and delivery systems, tissue and organ physiology and disease modeling, and personalized medicine. This review provides an overview of the latest developments in microfluidic-based cancer research, with pros, cons, and prospects.Öğe Nucleic Acid and Peptide Aptamers as Potential Antiviral Drugs(Bentham Science Publishers, 2021) Evran, Serap; Uğurlu, Özge; Man, Ezgi; Gültan, Merve; Özyurt, CananAptamers with target-specific binding properties have emerged as an alternative to antibodies. Nucleic acid aptamers are short single-stranded oligonucleotides that can fold into unique three-dimensional structures. Nucleic acid aptamers are selected from random libraries in vitro by using the SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technology. Likewise, peptide aptamers are short peptides that can be selected in vitro by using different strategies including phage display, ribosome display, or mRNA display. Aptamers are superior to antibodies with regard to ease of production, high stability, small size, and low cost. Therefore, aptamers find broad use in different biotechnological and therapeutic applications. Among them, aptamer use in virus detection and antiviral therapy is one of the attractive applications. The present Covid-19 pandemic and life-threatening viral infections reveal the need for rapid therapeutic solutions that can efficiently target viral mechanisms. In this respect, the chapter is mainly focused on aptamers with antiviral activity, as well as the use of aptamers in viral detection platforms. First, we summarize aptamer selection technologies that can be performed in vitro. Among them, we briefly explain ribosome display, mRNA display and SELEX (Systematic Evolution of Ligands by Exponential Enrichment) technologies. Then, we review aptamers targeting viral proteins and viral invasion mechanisms. In addition, we give an overview of aptamers developed against viruses. We also discuss the major hurdles in aptamer use, as well as the strategies to improve the drug potential of aptamers. © 2021 Bentham Science Publishers.Öğe The use of aptamers for environmental biosensors(Elsevier, 2024) Özyurt, Canan; Ince, Bahar; Uludağ, Inci; Sezgintürk, Mustafa KemalIn recent years, the development of innovative technologies has revolutionized the field of biosensing, offering new possibilities to detect and monitor environmental pollutants with unique sensitivity and specificity. Environmental biosensors have become crucial tools in addressing the growing concerns about pollution, contamination, and the overall health of our ecosystems. These biosensors play a significant role in detecting and monitoring various pollutants, including organic pollutants, heavy metals, pathogens, and endocrine-disrupting chemicals. Recent developments in biosensing technologies have led to the emergence of electrochemical aptasensors as a promising approach to detecting and monitoring environmental pollutants. Aptasensors, which utilize aptamers as biorecognition elements, offer numerous advantages over traditional analytical techniques. These advantages include high sensitivity, rapid response, low cost, and compatibility with portable and miniature devices. By combining the unique properties of aptamers with the sensitivity and simplicity of electrochemical sensing, aptasensors have the potential to revolutionize environmental monitoring. This chapter primarily focuses on using electrochemical aptasensors to detect and analyze environmental pollutants within the past 3 years. This work aims to serve as a valuable resource for future research endeavors by comprehensively examining various design methodologies’ analytical and technical intricacies with merits and drawbacks. © 2024 Elsevier Inc. 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