Development of a disposable electrochemical sensor for detection of cholesterol using differential pulse voltammetry.

In this study, a sensitive and selective electrochemical sensor was fabricated by using a screen printed carbon electrode (SPCE), multi-walled carbon nanotubes (MWCNTs) and ß-cyclodextrin (ß-CD) for detecting cholesterol. MWCNTs were functionalized with benzoic acid moiety by employing diazonium salt chemistry, and, subsequently, a thin film of functionalized CNTs were coated on the surface of SPCE. Afterwards, ß-CD was immobilized on functionalized MWCNTs modified SPCE which acts as a host to recognize guest (cholesterol) molecule specifically. Under the optimal experimental conditions and using differential pulse voltammetry (DPV) as transduction technique the sensor was able to detect cholesterol level ranges from 1 nM to 3 µM, with a detection limit of 0.5 nM. Specificity of the developed sensor towards target analyte (cholesterol) was confirmed in the presence of common interfering species including glucose, uric acid and ascorbic acid. The applicability of proposed sensor was also demonstrated for cholesterol determination in human serum samples with good recovery results (94-96%) and maximum RSD (relative standard deviation) of 4.5%.

Voltammetric detection of sequence-selective DNA hybridization related to Toxoplasma gondii in PCR amplicons.

This work describes the single-use electrochemical DNA biosensor technology developed for voltammetric detection of sequence selective DNA hybridization related to important human and veterinary pathogen; Toxoplasma gondii. In the principle of electrochemical label-free detection assay, the duplex of DNA hybrid formation was detected by measuring guanine oxidation signal occured in the presence of DNA hybridization. The biosensor design consisted of the immobilization of an inosine-modified (guanine-free) probe onto the surface of pencil graphite electrode (PGE), and the detection of the duplex formation in connection with the differential pulse voltammetry(DPV) by measuring the guanine signal. Toxoplasma gondii capture probe was firstly immobilized onto the surface of the activated PGE by wet adsorption. The extent of hybridization at PGE surface between the probe and the target was then determined by measuring the guanine signal observed at +1.0V. The electrochemical monitoring of optimum DNA hybridization has been performed in the target concentration of 40µg/mL in 50min of hybridization time. The specificity of the electrochemical biosensor was then tested using non-complementary, or mismatch short DNA sequences. Under the optimum conditions, the guanine oxidation signal indicating full hybridization was measured in various target concentration from 0.5 to 25µg/mL and a detection limit was found to be 1.78µg/mL. This single-use biosensor platform was successfully applied for the voltammetric detection of DNA hybridization related to Toxoplasma gondii in PCR amplicons.