A selective and regenerative elechtrochemical biosensor based aptamers for determination of homocysteine in biological samples

Homocysteine (HCys) is an amino acid with a free thiol (sulphydryl) group [1]. HCys is not found in the diet but is a mediator formed in the metabolism of methionine to cysteine [2]. Inhumans, normal levels of HCys in plasma are between 5 and 16 μM [3]. In higher concentrations of HCys are related to different diseases and its cause interesting in determination of HCys [4]. An electrochemical aptasensor was adopted as an analytical platform for the selective andsensitive HCys detection using the aptamer against HCys as the recognition probe in biological samples in presence of interferences such as cysteine and methionine. The HCys aptamer used in this study is a 66-mer truncated variant of DNA aptamer with binding constant of 600 nM forHCys [5]. The conditions for the immobilization of the aptamer and for binding of HCys have been here optimized. The assay protocol of the biosensor is shown in Fig. 1. Under optimized experimental conditions, the assay was linear in the ranges from 0.2 to 10 μM for HCysDetermination. The detection limit was 0.01 μM using 3sb/m. Repeatability of the aptasensor was estimated at 1.0 μM of HCys resulted in RSD of 5.2%. The results showed this proposal is simple, regenerative and cost effective and also has a good selectivity and sensitivity for electrochemical detection of HCys in biological samples.

Keywords:

Homocysteine , Aptamer , Aptasensor , Electrochemical Biosensor , Modify Electrode