Mihrican Muti

Chitosan-graphene oxide based aptasensor for the impedimetric detection of lysozyme.

An impedimetric detection of lysozyme (LYS) was performed for the first time in this study at the surface of chitosan-graphene oxide (CHIT-GO) modified sensor based on the specific interaction process between DNA aptamer and its cognate protein, LYS. The amino linked DNA aptamer (APT) was covalently immobilized without using any chemical agents onto the surface of pencil graphite electrode (PGE). These PGEs are inexpensive and simple to use, and thus, they can be furtherly developed for a single-use application in a portable protein chip device. The electrochemical impedance spectroscopy (EIS) technique was used herein to analyze (i) the surface characterization of unmodified PGE and CHIT-GO modified PGE, and also (ii) the interaction between APT and LYS. The limit of detection (DL) was found as 0.38 μg/mL (equals to 28.53 nM). This impedimetric LYS aptasensor exhibited a higher selectivity toward thrombin and bovine serum albumin, even in the mixture samples.

Electrochemical monitoring of indicator-free DNA hybridization by carbon nanotubes–chitosan modified disposable graphite sensors

Single walled carbon nanotubes (SWCNT)-chitosan (CHIT) modified pencil graphite electrodes (PGEs) were developed for monitoring of DNA hybridization. SWCNT-chitosan modified PGE (CNT-CHIT-PGE), Chitosan modified PGE (CHIT-PGE) and unmodified PGE (bare-PGE) were firstly characterized by using scanning electron microscopy (SEM), and their electrochemical behaviors were investigated using electrochemical impedance spectroscopy (EIS). The concentrations of CHIT, carbon nanotube (CNT) and also amino linked DNA probe etc. were respectively optimized in order to obtain the better working conditions of CNT-CHIT modified PGE in DNA analysis. The sequence selective DNA hybridization related to Hepatitis B virus (HBV) was then explored in the case of hybridization between amino linked HBV probe and its complementary (target), or noncomplementary (NC), or mismatch (MM) sequences, and also hybridization in mixture sample.

Preparation and characterization of zinc oxide nanoparticles and their sensor applications for electrochemical monitoring of nucleic acid hybridization.

In this study, ZnO nanoparticles (ZNP) of approximately 30 nm in size were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), Braun-Emmet-Teller (BET) N2 adsorption analysis and transmission electron microscopy (TEM). ZnO nanoparticles enriched with poly(vinylferrocenium) (PVF+) modified single-use graphite electrodes were then developed for the electrochemical monitoring of nucleic acid hybridization related to the Hepatitis B Virus (HBV). Firstly, the surfaces of polymer modified and polymer-ZnO nanoparticle modified single-use pencil graphite electrodes (PGEs) were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was also investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Subsequently, the polymer-ZnO nanoparticle modified PGEs were evaluated for the electrochemical detection of DNA based on the changes at the guanine oxidation signals. Various modifications in DNA oligonucleotides and probe concentrations were examined in order to optimize the electrochemical signals that were generated by means of nucleic acid hybridization. After the optimization studies, the sequence-selective DNA hybridization was investigated in the case of a complementary amino linked probe (target), or noncomplementary (NC) sequences, or target and mismatch (MM) mixture in the ratio of (1:1).

Tin oxide nanoparticles-polymer modified single-use sensors for electrochemical monitoring of label-free DNA hybridization.

In this study, SnO(2) nanoparticles (SNPs)-poly(vinylferrocenium) (PVF(+)) modified single-use graphite electrodes were developed for electrochemical monitoring of DNA hybridization. The surfaces of polymer modified and polymer-SNP modified pencil graphite electrodes (PGEs) were firstly characterized by using SEM analysis. The electrochemical behaviours of these electrodes were also investigated using the differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The polymer-SNP modified PGEs were then tested for the electrochemical sensing of DNA based on the changes at the guanine oxidation signals. Experimental parameters, such as; different modifications in DNA oligonucleotides, DNA probe concentrations were examined to obtain more sensitive and selective electrochemical signals for nucleic acid hybridization. After optimization studies, DNA hybridization was investigated in the case of complementary of hepatitis B virus (HBV) probe, mismatch (MM), and noncomplementary (NC) sequences.

Single-walled carbon nanotubes-polymer modified graphite electrodes for DNA hybridization

Single-walled carbon nanotubes (SWCNT)-poly(vinylferrocenium) (PVF(+)) modified pencil graphite electrodes (PGEs) were developed in our study for the electrochemical monitoring of a sequence-selective DNA hybridization event. Firstly, SWCNT-PVF(+) modified PGE, PVF(+) modified PGE and unmodified PGE were characterized using scanning electron microscopy (SEM). The electrochemical behavior of these electrodes was then investigated using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The SWCNT-PVF(+) modified PGEs were optimized for improved DNA sensing ability by measuring the guanine oxidation signal. In order to obtain the full coverage immobilization of the DNA probe following the optimum working conditions, the effect of amino-linked, thiol-linked and, bare oligonucleotides (ODNs), and the concentration of the DNA probe on the response of the modified electrode were examined. After optimization studies, the sequence-selective DNA hybridization was evaluated in the case of hybridization between an amino-linked probe and its complementary (target), a noncomplementary (NC) sequence, calf thymus double stranded DNA (dsDNA), and target/mismatch (MM) mixtures in the ratio of 1:1. SWCNT-PVF(+) modified PGEs presented very effective discrimination of DNA hybridization owing to their superior selectivity and sensitivity.

Electrochemical behaviour of carbon paste electrodes enriched with tin oxide nanoparticles using voltammetry and electrochemical impedance spectroscopy.

The effect of the SnO(2) nanoparticles (SNPs) on the behaviour of voltammetric carbon paste electrodes were studied for possible use of this material in biosensor development. The electrochemical behaviour of SNP modified carbon paste electrodes (CPE) was first investigated by using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The performance of the SNP modified electrodes were compared to those of unmodified ones and the parameters affecting the response of the modified electrode were optimized. The SNP modified electrodes were then tested for the electrochemical sensing of DNA purine base adenine to explore their further development in biosensor applications.

Chitosan–ionic liquid modified single-use sensor for electrochemical monitoring of sequence-selective DNA hybridization

Chitosan-(CHIT) and ionic liquid- (1-butyl-3-methylimidazolium hexafluorophosphate (IL)) modified single-use graphite electrodes (PGEs) were developed for the first time in the present study for the enhanced monitoring of DNA, and also for sequence-selective DNA hybridization by measuring the guanine oxidation signal. The electrochemical behaviour of the CHIT-IL modified electrodes was first investigated (with unmodified electrodes as controls) using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Sequence-selective DNA hybridization related to Hepatitis B virus (HBV) was also evaluated in the case of hybridization between amino-linked HBV probe and its complementary (target), a noncomplementary (NC) sequence, single base mismatch (MM), and also in the medium of target/mismatch (MM) mixtures (1:1). CHIT-IL modified PGEs presented a very effective discrimination of DNA hybridization owing to their superior selectivity and sensitivity.

Electrochemical polymerized 5-amino-2-mercapto-1,3,4-thiadiazole modified single use sensors for detection of quercetin.

In this study, electrochemical polymerized 5-amino-2-mercapto-1,3,4-thiadiazole (poly-AMT)-modified single-use graphite electrodes were fabricated for electrochemical monitoring of bisflavonoid, quercetin. The surfaces of p-AMT modified pencil graphite electrodes (PGEs) were firstly characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) analysis. The conditions for electrochemical polymerization by using cyclic voltammetry (CV), such as scan rate and different potential cycles were optimized. Electrochemical behaviors of these electrodes were also investigated using differential pulse voltammetry (DPV) and EIS. A six-fold increase at quercetin signal was obtained by using p-AMT modified PGEs compared to unmodified electrodes.

5-Amino-2-mercapto-1,3,4-thidiazole modified single-use sensors for electrochemical DNA analysis

In this study, single-use graphite electrodes modified with 5-amino-2-mercapto-1,3,4-thidiazole (AMT) were fabricated for electrochemical monitoring of DNA. The surfaces of AMT modified pencil graphite electrodes (PGEs) were characterized by scanning electron microscopy (SEM). Electrochemical behaviors of these electrodes were investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The effects of pretreatment of PGE and immobilization time and concentration of AMT were studied to facilitate an effective immobilization on PGE surface. The efficiency of immobilization is verified by measuring the oxidation signals of either AMT itself or adenine base of DNA, immobilized onto AMT modified electrodes.

Electrochemical monitoring of the interaction between anticancer drug and DNA in the presence of antioxidant

The aim of this work is to find out the effect of antioxidant onto the interaction of DNA-anticancer drug, daunorubicin. Daunorubicin (DNR) is an anti-cancer drug which is used for the treatment of certain cancers including the treatment of leukemia. The treatments of patients, who suffer from cancer, become generally complicated if they take some antioxidant-containing supplement during chemotherapy. In this study, the interaction performance between DNR and DNA was investigated both in the presence and absence of antioxidant, caffeic acid, as the first time in the literature. Interaction performances were evaluated by observing both guanine (1.0V) and DNR (0.5V) oxidation signal in the same potential window.