Mohammad Hossein Pournaghi-Azar

Development of an electrochemical DNA biosensor for direct detection and discrimination of HCV core/E1 region corresponding double-stranded DNA (ds-DNA) using a peptide nucleic acid (PNA) oligomer as the probe is described. The PNA probe is a cysteine conjugated 20-mer PNA oligomer, complementary to HCV core/E1 universal region, which is a consensus sequence in almost all HCV genotypes and is not present in other organisms. The significant variation in differential pulse voltammetric response of methylene blue (MB) on the probe modified gold electrode (AuE) upon hybridization with complementary double-stranded oligonucleotide (ds-oligonucleotide) following PNA/ds-DNA hybrid formation is the principle of target ds-DNA detection. No significant variations in MB signal following interaction of the probe with non-complementary and single-base mismatch (SBM) ds-DNAs was observed. This is due to the lack of hybridization between the probe and the non-complementary and SBM ds-DNA samples. Diagnostic performance of the biosensor is described and the detection limit of fully match target ds-DNA was found to be 9.63 × 10⁻¹² M and 4.97 × 10⁻¹² M for 2 h and 20 h hybridization times, respectively. The relative standard deviation over three independently probe modified electrodes measured at 100 pM of target ds-DNA was 2.9% and 2.4% for 2 h and 20 h hybridization times indicating a remarkable reproducibility of the detection method.

In the present work an aluminum electrode was modified with thin layer of metallic palladium. The ability of the electrode for electrooxidation and subsequent differential pulse voltammetric determination of paracetamol (PCT), ascorbic acid (AA) and codeine (CO) was evaluated. The results obtained indicated that a linear range from 0.1–3 mM and a detection limit of 5 μM for both three compounds is accessible. The peak separation of AA, PCT and CO is more than 300 mV large enough, allowed simultaneous determination of these compounds. The proposed method was applied for determination of AA, PCT and CO in some real samples.

Development of an electrochemical DNA biosensor for the direct detection and discrimination of double-stranded oligonucleotide (dsDNA) corresponding to hepatitis C virus genotype 3a, without its denaturation, using a gold electrode is described. The electrochemical DNA sensor relies on the modification of the gold electrode with 6-mercapto-1-hexanol and a self-assembled monolayer of 14-mer peptide nucleic acid probe, related to the hepatitis C virus genotype 3a core/E1 region. The increase of differential pulse voltammetric responses of methylene blue, upon hybridization of the self-assembled probe with the target ds-DNA to form a triplex is the principle behind the detection and discrimination. Some hybridization experiments with non-complementary oligonucleotides were carried out to assess whether the developed DNA sensor responds selectively to the ds-DNA target. Diagnostic performance of the biosensor is described and the detection limit was found to be 1.8 × 10⁻¹² M in phosphate buffer solution, pH 7.0. The relative standard deviation of measurements of 100 pM of target ds-DNA performed with three independent probe-modified electrodes was 3.1%, indicating a remarkable reproducibility of the detection method. Figure Development of an electrochemical DNA biosensor for the direct detection and discrimination of double-stranded oligonucleotide (dsDNA) corresponding to hepatitis C virus genotype 3a without its denaturation using a gold electrode is described. The Electrochemical DNA sensor relies on the modification of gold electrode with 6-mercapto-1-hexanol and self-assembled monolayer of 14-mer peptide nucleic acid probe, related to the hepatitis C virus genotype 3a core/E1 region. The increase of differential pulse voltammetric responses of methylene blue, upon hybridization of the self-assembled probe with the target ds-DNA to form a triplex is the principal of the detection and discrimination. Some hybridization experiments with non-complementary oligonucleotides were carried out to assess whether the suggested DNA sensor responds selectively to the ds-DNA target. Diagnostic performance of the biosensor is described and the detection limit was found to be 1.84 × 10⁻¹² M, in phosphate buffer solution, pH 7.0. The relative standard deviation over three independently probe modified electrodes measured at 100 pM of target ds-DNA was 3.1 % indicating a remarkable reproducibility of the detection method.