Fullerene Based Sensor and Biosensor Technologies

Sensor and biosensor technologies have shown rapid progress in recent years. These technologies use nanomaterials that have an important place in immobilization materials for recognition analyte molecules. Although fullerenes among these materials have attracted much attention in recent years, their number of studies is less than other carbon-based nanomaterials. Thanks to its completely closed structure and at least 30 double bonds, it can be modified from 30 points, which provides a great advantage. At these points, thanks to the ability to modify amine, thiol, carboxyl or metallic groups, modification residues can be created for all kinds of immobilization. According to the zero-dimensional nanomaterial class, fullerenes provide an extremely large surface area. Therefore, it provides more biological or non-biological recognition receptors immobilized on this surface area. Moreover, increasing the surface area with more recognition agent also increases the sensitivity. This is the most important parameter of sensor technologies, which is provided by fullerenes. In this book chapter, the development of fullerene-modified sensor and biosensor technologies are explained with examples, and fullerene modifications are given in figures as fullerene derivatives. Contribution was made in the method development stage by giving comparison of fullerene type sensor and biosensor systems

Molecularly Imprinted Sensors — New Sensing Technologies

In this chapter we discus molecular imprinting technology (MIT), molecular imprinted polymers (MIPs), and their compatibility on a proper transducer to construct a sensing system. Molecularly imprinted sensors (MISens), in other words, artificial receptor-based sensors synthesized in the presence of the target molecule, are capable of sensing target molecules by using their specific cavities and are compatible with the target molecule. This MIP technology is a viable alternative of artificial receptor technology, and the sensor technology is capable of detecting any kind of molecule without pre-analytic preparations. In this chapter, you can find examples, sensor construction techniques and fundamentals of MIP and sensor combinations to look forward in your studies. For sensor technology, we explained and discussed the new sensing technologies of MIP-based electrochemical, optical (especially surface plasmon resonance, SPR), and piezoelectric techniques. Therefore, this chapter presents a short guideline of MISens

Nucleic Acids for Electrochemical Biosensor Technology

Biosensor technology has developed extremely rapidly in recent years. This technology brings along precise measurements as well as specific measurements. Thanks to its ability to be miniaturized and be easily accessible to the end user, it is one-step ahead of other similar methods. The selectivity of biological molecules and the sensitivity of electrochemical methods enable the continuous evolvement of these new technologies. In this chapter, the use of nucleic acids as both recognition agents and target molecules, the way they are used in biosensor technology and their electrical properties are explained in detail with examples. Aptamers, which are synthetic nucleic acids, and their use in electrochemical biosensor systems with different electrochemical and immobilization methods have been compared extensively

Tümör tanı ve izlemi için dolaşımdaki serbest DNA'nın tayinine yönelik spesifik bir biyosensör sistemi geliştirilmesi

Dünya çapında ölüme yol açan nedenler arasında kanser, kalp hastalıklarından sonra ikinci sırayı almaktadır. Kanser tedavilerindeki önemli gelişmelere rağmen, morbidite ve mortalite hala çok yüksektir. Bu kapsamda, halihazırda kullanılan kan biyobelirteçleri yanı sıra "sıvı biyopsi" olarak tanımlanan ve tümör dokusundan salınan dolaşımdaki hücre dışı tümör DNA’sını (circulating tumor DNA-ctDNA) saptamaya yönelik kan tabanlı analizler noninvaziv, spesifik, pratik ve ekonomik olmaları nedeniyle son yıllarda ilgi çekmektedirler. Bu çalışmada ctDNA’nın doğrudan tespiti için, grafen oksit ekran baskılı elektrotlar (GPHOXE), biyolojik tanıma reseptörü olarak dCas9 proteinleri ve sgRNA ile modifiye edilmiştir. Biyosensörün temelinde yer alan diziye özgü tanımanın örnekte hedeflediği yapı ise, meme kanserinde en sık görülen tümöre bağlı mutasyon olan PIK3CA ekson 9 mutasyonudur. Geliştirilen sistemde, CRISPR-dCas9-sgRNA ile modifiye edilmiş elektrotların yüzeyinde bu mutasyonun varlığında gerçekleşen bağlanma ise, elektrokimyasal impedans spektroskopisi (Electrochemical Impedance Spectroscopy-EIS) ile analiz edilmiştir. Tek nükleotit uyuşmazlığı da dahil olmak üzere hedef mutasyon dışındaki ctDNA dizileri için son derece seçici özellik gösteren sistemin ölçüm süresi son derece hızlı (40 saniye) olarak saptanmıştır. Analiz, 120 bp ctDNA'lar için 2-20 nM arasında doğrusal saptama sınırlarında olup en düşük tespit limiti (LOD) 0,65 nM ve en düşük tayin limiti (LOQ) 1,92 nM olarak hesaplanmıştır. Gerçek kan örneklerinde seçicilik ve tekrarlanabilirlik çalışmaları yapılmış ve geri elde oranı % 96'dan yüksek olmuştur. Aynı metot, doğrulama amaçlı olarak altın elektrot ile de denenmiş ve ctDNA analizi başarı ile yapılabilmiştir. Sonuç olarak bu tez çalışmasında grafen oksit elektrotlarda geliştirilen ve altın elektrot ile doğrulama çalışmaları yapılan dCas9 temelli impedimetrik biyosensör sistemi, ctDNA ölçümünde yüksek seçicilik, hız, tekrar üretilebilirlik ve ekonomik olma avantajları sağlamaktadır. Ön çalışmaları sağlam verilerle kanıtlanmış olan bu düzeneğin geliştirilerek multipleks bir sistem çerçevesinde diğer önemli mutasyonlara yönelik olarak da uygulanması, kanserin erken teşhisinde umut verici bir alan olarak ortaya çıkmaktadır.Among the causes of death worldwide, cancer is the second leading cause of death, following coronary diseases. Despite significant improvements in cancer treatments, morbidity and mortality rates are still very high. Thus, in addition to the currently used blood biomarkers, circulating extracellular tumor DNA (ctDNA), have attracted attention in recent years. These analysis are defined as "liquid biopsy" and their non-invasive, specific, practical and economical nature is well appreciated. There are increasing numbers of publications showing that ctDNA accurately demonstrates tumor burden and treatment response, reduces the need for harmful adjuvant chemotherapy, and allows recurrence to be detected more quickly. In this study, graphene oxide screen printed electrodes (GPHOXE) were modified with dCas9 proteins and sgRNA as biorecognition receptor for direct detection of ctDNA. The sequence-specific recognition targeted PIK3CA exon 9 mutation which is the most common tumor-related mutation in breast cancer. With electrodes modified with CRISPR-dCas9-sgRNA, the presence of the mutation was analyzed by EIS. The system is highly selective for the PIK3CA exon 9 mutation containing ctDNA and eliminates other mutations, including even single nucleotide mismatch. The measurement time is determined to be extremely fast (40 seconds). The analysis was carried out in a linear detection range between 2 and 20 nM for 120 bp ctDNAs. The lower limit of detection (LOD) was 0.65 nM and the lower limit of quantification (LOQ) was 1.92 nM. Selectivity and reproducibility studies were performed on real blood samples, and the recovery was higher than 96%. An alternative modification procedure was performed on gold electrodes for verification purposes and ctDNA analysis was successfully performed on this platform as well. In conclusion, the dCas9 based impedimetric biosensor system, which was developed on graphene oxide electrodes and verified with gold electrode, provided advantages like high selectivity, fast detection, reproducibility and economic efficiency in ctDNA analysis. The development of this novel biosensor, whose preliminary studies have been proven with solid data, and its application for other important mutations within the framework of a multiplex system, is a promising area in the early diagnosis of cancer

A short footnote: Circuit design for faradaic impedimetric sensors and biosensors

WOS: 000339994900059Electrochemical impedance spectroscopy (EIS) is an electrochemical surface characterization technique and has been widely used in biosensor and chemical sensors, also provides label free detection. This technique is used as faradaic and non-faradaic measurement. The advantage of the sensitivity of faradaic impedance spectroscopy becomes useful and preferred technique. In this review we tried to answer these questions: how Nyquist plots are fitted in proper circuit and how a proper circuit element is chosen in fitting and impedance calculation steps. Nyquist plot can become very confusing to fit on a proper circuit modal and calculation of impedance (Z). Z is called in other word as electron transfer resistance (R-et), additionally electrolyte interface impedance (R-s), capacitance (C) and Warburg impedance (W) are the other elements. These all circuit elements must be constructed in a proper order to fit Nyquist plot into a good circuit model. Therefore it is very important to examine Nyquist plot for accurate calculation. (C) 2014 Elsevier B.V. All rights reserved