Melahat Sevgül BAKAY, Tuğçe POLAT, Adil DENİZLİ, Feride Şermin UTKU

Kolin Tespiti İçin Moleküler Baskılama Tabanlı Biyosensör Geliştirilmesi

Biyolojik sensörün kısaltması olarak kullanılan biyosensörler, maddelerin sıvı ya da gaz ortamda nicel veya nitel tayinini sahip olduğu biyolojik tanıma bölgeleri sayesinde yapabilen ve elde ettiği verileri tespit edilebilir sinyallere çeviren sistemlerdir. Biyosensörler, uygun tanıma bölgeleri aracılığıyla fiziksel değişiklikleri (yoğunluk, kütle, derişim vb.) tespit edebilmekte ve bunları elektriksel veya optik büyüklüklerle (akım, gerilim, empedans vb.) ilişkilendirmektedir. Bu çalışmada, E-1M, E-3M ve E-5M olmak üzere 3 farklı derişimde moleküler baskılanmış, farklı sayıda kolin tanıma bölgelerine sahip, kalem grafit elektrotlar (PGE), elektrokimyasal biyosensörler olarak kullanılmıştır. Elektrot yüzeyindeki kolin reseptörü konsantrasyonundaki artışın, PGE yüzeyine bağlı kolindeki artışla ilişkili olması ve dolayısıyla elektriksel değişikliklere yol açması beklenmektedir. Çalışma, üç elektrotlu hücrede, referans elektrot olarak Ag/AgCl, karşı elektrot olarak platin tel ve çalışma elektrotu olarak PGE kullanılarak gerçekleştirilmiştir. Elektrotların açık hücre potansiyeli, dönüşümsel voltametri ve elektrokimyasal empedans ölçümleri, 5mM K3[FeCN6]-3/-4 redoks çifti içeren 10 mM fosfat tampon çözeltisi (PBS) içerisinde alınmıştır. Çözelti içerisindeki kolinin, kolin baskılanmış PGE'ler üzerindeki tamamlayıcı tanıma alanlarına bağlanmasıyla beklendiği gibi PGE'lerde akım, voltaj ve empedans değişimleri gözlenmiştir. Baskılanan molekül konsantrasyonunun artışıyla bağıntılı olarak tespit aralığında da bir artış gözlenmiştir. Sonuç olarak, E-1M kolin baskılanan PGE, 7.2 nM-72 pM tespit aralığındaki kolin konsantrasyonunda en yüksek farklılaşmayı göstermiştir.

Anahtar Kelimeler:

Biyosensör, elektrokimyasal empedans spektroskopisi, kolin, moleküler baskılama, PGE elektrot

Molecularly Imprinted Polymer Based Biosensor for Choline

Biosensors are systems that can perform a quantitative and/or qualitative analysis of substances in a liquid or gas environment through their biological recognition sites and transform the acquired data into detectable signals. Biosensors are able to detect physical changes (i.e. as density, mass concentration, etc.) by means of recognition sites and correlate them with electrical or optical quantities (i.e. current, voltage and impedance). In this study, three molecularly imprinted pencil graphite electrodes (PGE) with differing numbers of choline recognition sites, at E-1 M, E-3 M and E-5 M concentration, were used as electrochemical biosensors. An increase in choline receptor concentration on the electrode surface was expected to correlate with an increase in PGE surface bound choline and thus lead to electrical changes. The study was conducted in a three-electrode cell with Ag/AgCl as the reference electrode, platinum wire as the counter electrode and PGE as the working electrode. Cyclic voltammetry and electrochemical impedance measurements were conducted in 10 mM phosphate buffer solution (PBS) containing 5mM K3[FeCN6]-3/-4 redox pair. As expected, as increasing amount of choline was bound to the complementary recognition sites on choline imprinted PGEs, a correlating change in current, voltage and impedance on PGEs was observed. The dynamic detection range for choline expanded as the choline concentration imprinted on the PGE electrode increased. Using the E-1 M PGE electrode, 72 pM limit of detection, up to 7.2 nM limit of linearity was attained.

Keywords:

Biosensor, electrochemical impedance spectroscopy, choline, molecularly imprinted polymer, PGE electrode,

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