Abstract
A novel disposable electrochemical biosensor based on immobilized calf thymus double-stranded DNA (dsDNA) on the carbon-based screen-printed electrode (SPE) is developed for rapid biorecognition of carrageenan by using methylene blue (MB) redox indicator. The biosensor protocol for the detection of carrageenan is based on the concept of competitive binding of positively charged MB to the negatively charged dsDNA and carrageenan. The decrement in the MB cathodic peak current (ipc) signal as a result of the released MB from the immobilized dsDNA, and attracted to the carrageenan can be monitored via differential pulse voltammetry (DPV). The biosensor showed high sensitivity and selectivity to carrageenan at low concentration without interference from other polyanions such as alginate, gum arabic and starch. Calibration of the biosensor with carrageenan exhibited an excellent linear dependence from 1–10 mg L−1 (R2 = 0.98) with a detection limit of 0.08 mg L−1. The DNA-based carrageenan biosensor showed satisfactory reproducibility with 5.6–6.9% (n = 3) relative standard deviations (RSD), and possessing several advantages such as simplicity, fast and direct application to real sample analysis without any prior extensive sample treatments, particularly for seaweeds and food analyses.
Highlights
Carrageenans are used in a variety of commercial applications because of their excellent physical properties, especially as thickening, stabilizing and gelling agents in dairy food products such as frozen desserts
In view of the innate net negative charge along the sugar-phosphate backbone of DNA molecule, and the well-established accumulation of methylene blue (MB) with the double-stranded DNA, in this paper, we introduce a novel voltammetric DNA biosensor for carrageenan detection based on the competitive electrostatic interaction of dsDNA and carrageenan towards binding with MB
The differential pulse voltammetry (DPV) peak current increased sharply with a positive shifting of the DPV peak potential is typical for the intercalation of MB with dsDNA30
Summary
Carrageenans are used in a variety of commercial applications because of their excellent physical properties, especially as thickening, stabilizing and gelling agents in dairy food products such as frozen desserts. In view of the complexities in chemical compositions of foods, they often require extensive sample preparation and purification procedures in order to eliminate interferences prior to analysis of carrageenan can be carried out[7,8,9,10] using conventional methods such as chromatographic techniques[11,12,13,14,15,16]. MB interacts electrostatically with carrageenan at low concentrations through cationic alkylamino functional group of MB and anionic ester sulphate group in the carrageenan molecule. This basic dye has been used since 1930 by Ewe[19] for the identification and differentiation between carrageenan and other natural gums from plants.
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