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

Kolin Tespiti İçin Moleküler Baskilama Tabanli 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-1 M, E-3 M ve E-5 M olmak üzere 3 farklı derişimde moleküler baskılanmış, farklı sayıda kolin tanıma bölgelerine sahip, kalem grafit elektrotlar, elektrokimyasal biyosensörler olarak kullanılmıştır. Elektrot yüzeyindeki kolin reseptörü derişimindeki artışın, elektrod yüzeyinebağlı 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 içerisinde alınmıştır. Çözelti içerisindeki kolinin, kolin baskılanmış elektrodlar üzerindeki tamamlayıcı tanıma alanlarına bağlanmasıyla, elektrodlarda beklenen akım, voltaj ve empedans değişimleri gözlenmiştir. Baskılanan molekül derişiminin artışıyla bağıntılı olarak, tespit aralığında da bir artış gözlenmiştir. Sonuç olarak, E-1 M kolin baskılanan PGE, 7.2 nM-72 pM tespit aralığındaki kolin konsantrasyonunda en yüksek farklılaşmayı göstermiştir.

Molecularly Imprinted Polymer Based Biosensor For Choline

Biosensors are systems that can perform quantitative and/or qualitative analysis of substances in liquid or gasenvironment 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 recognitionsites and correlate them with electrical or optical quantities (i.e. current, voltage and impedance). In this study,three molecularly imprinted pencil graphite electrodes with differing numbers of choline recognition sites, at E-1M, E-3 M and E-5 M concentration, were used as electrochemical biosensors. An increase in choline receptorconcentration on the electrode surface was expected to correlate with an increase in PGE surface bound cholineand thus lead to electrical changes. The study was conducted in a three-electrode cell with Ag/AgCl as thereference electrode, platinum wire as the counter electrode and PGE as the working electrode. Cyclicvoltammetry and electrochemical impedance measurements were conducted in 10 mM phosphate buffer solutioncontaining 5mM K3[FeCN6]-3/-4redox pair. As expected, as increasing amount of choline was bound to thecomplementary recognition sites on choline imprinted electrodes, a correlating change in current, voltage andimpedance was observed. The dynamic detection range for choline expanded as the choline concentrationimprinted on the electrodes increased. Using the E-1 M PGE electrode, 72 pM limit of detection, up to 7.2 nMlimit of linearity was attained.

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