Characterization of HRP-based amperometric biosensor by using screen printed electrodes

---

Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Erciyes Üniversitesi, Fen Bilimleri Enstitüsü, --, Türkiye

Tezin Onay Tarihi: 2019

Tezin Dili: İngilizce

Öğrenci: MAHMOOD TAHA NOORI AL-SADOON

Asıl Danışman (Eş Danışmanlı Tezler İçin): Ebru Saatçi

Özet:

Immunosensors are examples of highly specific biosensors with excellent selective

properties based on antigen-antibody interaction. In electrochemical immunosensors,

the resulting current is the result of a function of either the concentration of direct

electroactive species or the production or consumption rates in the biocatalytic

material. When compared to other methods, high precision is a good alternative

because of its advantages such as wide linear range of use, high stability, fast

response and economic advantages. In immunosensors, classical ELISA methods are

adapted on the biosensor.

The most commonly used enzyme in immunosensors is horseradish peroxidase

(HRP). Different substrates of HRP are used in amperometric measurements. The

HRP substrate, 2,2'-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium

salt (ABTS), yields the oxidation and reduction peaks against the reciprocal

voltammetry Ag/AgCl reference. Another HRP substrate, TMB (3,3)-5,5-

Tetramethylbenzidine dihydrochloride) is used to determine the immobilized antigen

concentration. The signal on the sensor generates an electroactive signal. Thus, it is

used in the electrochemical determination by the amperometric biosensor.

Recently magnetic micro beads (MBs) are very attractive in the development and

fabrication of sensors and biosensors for several applications. Screen-printing is one

of the most promising approaches towards simple, rapid and inexpensive production

of biosensors. The combination of these materials are very promising for the

development of amperometric immunosensors.

In this study, conjugated enzyme (HRP) and its substrates (ABTS and TMB) were

compared with amperometric measurements to understand their effects on

immunosensor development. For this reason, avidin-HRP binded biotin-IgG

antibodies were immobilized on protein G-coated magnetic beads. From that point

onward, ABTS or TMB was added to MB mixture and a constant potential was

applied to the system. Measurrment are performed by using Dropsens 8x SPE carbon

electrodes. For ABTS, the range of IgG antibody concentration was found between

5-360 ng / ml. For TMB, the IgG antibody linear standard curve was drawn and with

the short biosensor detection time, the detection limit range was found between 0.1-

20 ng / ml.