Pinar Kara - Academia.edu (original) (raw)

Papers by Pinar Kara

Biosensors, 2021

The CRISPR-Cas9 system has facilitated the genetic modification of various model organisms and ce... more The CRISPR-Cas9 system has facilitated the genetic modification of various model organisms and cell lines. The outcomes of any CRISPR-Cas9 assay should be investigated to ensure/improve the precision of genome engineering. In this study, carbon nanotube-modified disposable pencil graphite electrodes (CNT/PGEs) were used to develop a label-free electrochemical nanogenosensor for the detection of point mutations generated in the genome by using the CRISPR-Cas9 system. Carbodiimide chemistry was used to immobilize the 5′-aminohexyl-linked inosine-substituted probe on the surface of the sensor. After hybridization between the target sequence and probe at the sensor surface, guanine oxidation signals were monitored using differential pulse voltammetry (DPV). Optimization of the sensitivity of the nanogenoassay resulted in a lower detection limit of 213.7 nM. The nanogenosensor was highly specific for the detection of the precisely edited DNA sequence. This method allows for a rapid and e...

Analytical and Bioanalytical Chemistry, 2020

In the present study, a sensitive electrochemical aptamer-based biosensing strategy for human non... more In the present study, a sensitive electrochemical aptamer-based biosensing strategy for human non-small cell lung cancer (NSCLC) detection was proposed using nanofiber-modified disposable pencil graphite electrodes (PGEs). The composite nanofiber was comprised of polyacrylonitrile (PAN) and polypyrrole (PPy) polymers, and fabrication of the nanofibers was accomplished using electrospinning process onto PGEs. Development of the nanofibers was confirmed using scanning electron microscopy (SEM). The high-affinity 5′-aminohexyl-linked aptamer was immobilized onto a PAN/PPy composite nanofibermodified sensor surface via covalent bonding strategy. After incubation with NSCLC living cells (A549 cell line) at 37.5°C, the recognition between aptamer and target cells was monitored by electrochemical impedance spectroscopy (EIS). The selectivity of the aptasensor was evaluated using nonspecific human cervical cancer cells (HeLa) and a nonspecific aptamer sequence. The proposed electrochemical aptasensor showed high sensitivity toward A549 cells with a detection limit of 1.2 × 10 3 cells/mL. The results indicate that our label-free electrochemical aptasensor has great potential in the design of aptasensors for the diagnostics of other types of cancer cells with broad detection capability in clinical analysis.

Electroanalysis, 2007

... The electrode was prepared by cutting the leads into 3 cm long sticks as described previously... more ... The electrode was prepared by cutting the leads into 3 cm long sticks as described previouslyOzkan et al. and Kara et al. [18, 20, 22]. 2.3.2.2. ... 1998, 70, 4670. [13] B. Meric, K. Kerman, D. Ozkan, P. Kara, S. Erensoy, US Akarca, M. Macsini, M. Ozsoz, Talanta 2002, 56, 837. ...

Analytical Methods, 2011

ABSTRACT In the presented study, a novel method is introduced that demonstrates the electrochemic... more ABSTRACT In the presented study, a novel method is introduced that demonstrates the electrochemical detection of influenza B virus based on DNA hybridisation. The detection utilised gold nanoparticles (AuNPs) and Meldola's Blue (MDB), which is utilised as an intercalator label. The developed methodology, combined with a disposable pencil graphite electrode (PGE) and differential pulse voltammetry (DPV), was performed using both synthetic oligonucleotides and polymerase chain reaction (PCR) amplicons. The electrochemical oxidation response of guanine (approximately +0.1 V) and the voltammetric reduction signal of MDB (approximately −0.2 V) were measured before and after hybridisation reactions between a single strand DNAprobe and its complementary target strain (synthetic target or denatured PCR samples). Before the immobilisation of the synthetic DNAprobe of influenza type B virus, the transducer surface was interacted with AuNPs solution using a simple wet adsorption method. AuNP immobilisation was confirmed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to characterise the recognition surface of the genosensor. After the interaction between the PGE and AuNPs, a thiol-linked DNAprobe was immobilised onto the nanoparticle-covered surface. When hybridisation occurred between the probe and its synthetic targets or specific PCR products, the highest MDB signal was observed. The probes were also challenged with equal quantities of non-complementary DNA at the PGE surface for the determination of biosensor selectivity. AuNP-coated electrodes showed high sensitivity and selectivity, specifically in real samples for the detection of the hybridisation reaction. The results obtained in the presented study indicated that the electrode surface area could be enhanced with AuNPs. The detection limit of the genosensor was found to be 54 picomoles for the synthetic target and 3.3 × 107 molecules for the real samples (PCR) in 30 μL of sample volume. Future prospects and analytical performance of the sensor is briefly discussed.

Instrumental methods of analysis modern trends and applications, 2005

Biosensors, 2021

Citation: Kivrak, E.; Pauzaite, T.; Copeland, N.A.; Hardy, J.G.; Kara, P.; Firlak, M.; Yardimci, ... more Citation: Kivrak, E.; Pauzaite, T.; Copeland, N.A.; Hardy, J.G.; Kara, P.; Firlak, M.; Yardimci, A.I.; Yilmaz, S.; Palaz, F.; Ozsoz, M. Detection of CRISPR-Cas9-Mediated Mutations Using a Carbon Nanotube-Modified Electrochemical Genosensor.

Analytica Chimica Acta, Aug 1, 2004

An electrochemical biosensor for the voltammetric detection of DNA sequences related to herpes si... more An electrochemical biosensor for the voltammetric detection of DNA sequences related to herpes simplex viruses (HSV) and discrimination of HSV Type I and Type II viruses from polymerase chain reaction (PCR) amplified real samples were described in this study. The biosensor relies on the covalent immobilization of the 22-mer single stranded oligonucleotides (probe) related to both HSV Type I and Type II sequences and hybridization of these oligonucleotides with their complementary and four bases mismatch containing (four bases MM) sequences at pencil graphite electrodes (PEGE). The extent of hybridization between probe and target sequences was determined by using differential pulse voltammetry (DPV) and Meldola Blue (MDB) was used as the hybridization indicator. As a result of the interaction between MDB and DNA at PEGE surface, the MDB signal observed from probe sequence before hybridization and after hybridization with four bases MM sequence is lower than that observed after hybridization with complementary sequence. The difference between the MDB signals obtained from probe modified, hybrid modified and four bases MM modified PEGE were used to detect and discriminate two types of HSV from PCR amplified real samples. Numerous factors affecting the target hybridization and indicator binding reactions are optimized to maximize the sensitivity.

Biosensors and Bioelectronics, Dec 15, 2010

A label-free bioelectronic detection of aptamer-thrombin interaction based on electrochemical imp... more A label-free bioelectronic detection of aptamer-thrombin interaction based on electrochemical impedance spectroscopy (EIS) technique is reported. Multiwalled carbon nanotubes (MWCNTs) were used as modifiers of screen-printed carbon electrotransducers (SPCEs), showing improved characteristics compared to the bare SPCEs. 5'amino linked aptamer sequence was immobilized onto the modified SPCEs and then the binding of thrombin to aptamer sequence was monitored by EIS transduction of the resistance to charge transfer (Rct) in the presence of 5 mM [Fe(CN)(6)](3-/4-), obtaining a detection limit of 105 pM. This study represents an alternative electrochemical biosensor for the detection of proteins with interest for future applications.

Electroanalysis

The response surface methodology (RSM) is used for optimization of foodborne pathogen detection b... more The response surface methodology (RSM) is used for optimization of foodborne pathogen detection based on label free electrochemical nucleic acid biosensors. Listeria monocytogenes amplicons obtained from food samples are used as model case. The extent of hybridization is determined by using guanine oxidation signals obtained with Differential Pulse Voltammetry and Electrochemical Impedance Spectroscopy. RSM is used to investigate the effects of hybridization parameters including target and salt concentration and hybridization time on the biosensor selectivity. The ratio of electrochemical transductions after hybridization with complementary and noncomplementary targets is the response of the statistical analysis obtaining a detection limit of 267 pM.

RSC Adv., 2014

A label and indicator free electrochemical DNA hybridization detection method based on MnO2-Nps/G... more A label and indicator free electrochemical DNA hybridization detection method based on MnO2-Nps/GCPE was developed. Compared to plain GCPE, a very robust and sensitive genosensor was obtained.

Electrochemical DNA Biosensors, 2012

Journal of Pharmaceutical and Biomedical Analysis, 2005

Electrochemical biosensor for the detection of DNA hybridization using the reduction signal of al... more Electrochemical biosensor for the detection of DNA hybridization using the reduction signal of alpha-naphthol is described. A pencil graphite electrode was used as a working electrode. Capture probes were covalently attached on to the pencil graphite electrode surface (PGE) at the 5' end amino group by using N-(dimethylamino)propyl-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (NHS) as a coupling agent on to PGE. After capture probe immobilization on to PGE surface; probe was hybridized with complementary biotinylated oligonucleotide. Alkaline phosphatase labeled with extravidin (Ex-AP) binds to biotinylated hybrid via biotin-avidin interaction. alpha-Naphthyl phosphate (alpha-NAP) was added and the reaction between alkaline phosphatase (AP) and alpha-NAP was occurred consequently as a substrate of AP, alpha-NAP reduction signal was obtained from this reaction, at -0.100 V by using differential pulse voltammetry (DPV). Other experimental parameters were studied such as; optimizations of hybridization time, and the concentrations of capture probe, biotinylated oligonucleotide and enzyme.

Journal of Pharmaceutical and Biomedical Analysis, 2002

The interaction of an alkylating agent, 4,4?-dihydroxy chalcone (DHC) with calf thymus double str... more The interaction of an alkylating agent, 4,4?-dihydroxy chalcone (DHC) with calf thymus double stranded DNA (dsDNA) and calf thymus single stranded DNA (ssDNA) was studied electrochemically based on the oxidation signals of guanine and adenine by using differential pulse voltammetry (DPV) at carbon paste electrode (CPE). As a result of the alkylation of DHC between the base pairs in dsDNA, the voltammetric signal of guanine and adenine greatly decreased. After the interaction of DHC with ssDNA, a higher decrease in the oxidation signals of guanine and adenine was observed under the same conditions. The partition coefficients of DHC at dsDNA and ssDNA modified CPEs were calculated. The interactions of DHC with synthetic polynucleotides, such as polyguanylic acid and polyadenylic acid were also observed. In addition, the detection limit and the reproducibility were determined by using DPV. The interaction of DHC with dsDNA in solution-phase was also investigated and the results were compared with the ones obtained by surface immobilized dsDNA. The application of electrochemical DNA biosensor for monitoring the DNA Á/alkylating agent interactions was explored. #

Electrochemistry Communications, 2005

A genomagnetic assay coupling of electrochemical monitoring for the detection of wild type hepati... more A genomagnetic assay coupling of electrochemical monitoring for the detection of wild type hepatitis B virus (HBV) DNA in polymerase chain reaction (PCR) amplicons has been described. The development of this technology combined with a disposable sensor, pencil graphite ...

Electrochemistry Communications, 2002

An electrochemical hybridization biosensor based on peptide nucleic acid (PNA) probes is presente... more An electrochemical hybridization biosensor based on peptide nucleic acid (PNA) probes is presented. PNA probes were attached covalently through a competition of free amines on the guanine bases and also at the 5 0 end of the probe, using N-(3-dimethylamino)propyl)-N 0 -ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) onto a carboxylate terminated alkanethiol self-assembled monolayer (SAM) preformed on a gold electrode (AuE). The covalently immobilized probe could selectively hybridize with the target DNA to form a hybrid on the surface despite the bases being attached to the SAM. The changes in the peak currents of methylene blue (3,7-bis(dimethylamino)phenothiazin-5-ium chloride, MB), an electroactive label, were observed upon hybridization of probe with the target. Effective discrimination against point mutation was also obtained. Performance characteristics of the sensor are described, along with future prospects. Ó

Bioelectrochemistry, 2002

Described here are the electrochemical parameters for MB on binding to DNA at hanging mercury dro... more Described here are the electrochemical parameters for MB on binding to DNA at hanging mercury drop electrode (HMDE), glassy carbon electrode (GCE), and carbon paste electrode (CPE) in the solution and at the electrode surface. MB, which interacts with the immobilized calf thymus DNA, was detected by using single-stranded DNA-modified HMDE or CPE (ssDNA-modified HMDE or CPE), bare HMDE or CPE, and double-stranded DNA-modified HMDE or CPE (dsDNA-modified HMDE or CPE) in combination with adsorptive transfer stripping voltammetry (AdTSV), differential pulse voltammetry (DPV), and alternating current voltammetry (ACV) techniques. The structural conformation of DNA and hybridization between synthetic peptide nucleic acid (PNA) and DNA oligonucleotides were determined by the changes in the voltammetric peak of MB. The PNA and DNA probes were also challenged with excessive and equal amount of noncomplementary DNA and a mixture that contained one-base mismatched and target DNA. The partition coefficient was also obtained from the signal of MB with probe, hybrid, and ssDNA-modified GCEs. The effect of probe, target, and ssDNA concentration upon the MB signal was investigated. These results demonstrated that MB could be used as an effective electroactive hybridization indicator for DNA biosensors. Performance characteristics of the sensor are described, along with future prospects. D 1567-5394/02/$ -see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 1 5 6 7 -5 3 9 4 ( 0 2 ) 0 0 1 3 1 -7

Bioelectrochemistry, 2005

Electrochemical DNA biosensors have become strong candidates for DNA based analysis. Allele-speci... more Electrochemical DNA biosensors have become strong candidates for DNA based analysis. Allele-specific genotyping is also one of the important research areas, where electrochemical approaches provide promising advances. Recently reported two methods based on electrochemical guanine and colloidal gold (Au) nanoparticle oxidation signals are reviewed and compared with the existing genotyping methods in this report. D

Electroanalysis

The response surface methodology (RSM) is used for optimization of foodborne pathogen detection b... more The response surface methodology (RSM) is used for optimization of foodborne pathogen detection based on label free electrochemical nucleic acid biosensors. Listeria monocytogenes amplicons obtained from food samples are used as model case. The extent of hybridization is determined by using guanine oxidation signals obtained with Differential Pulse Voltammetry and Electrochemical Impedance Spectroscopy. RSM is used to investigate the effects of hybridization parameters including target and salt concentration and hybridization time on the biosensor selectivity. The ratio of electrochemical transductions after hybridization with complementary and noncomplementary targets is the response of the statistical analysis obtaining a detection limit of 267 pM.

Journal of the Iranian Chemical Society, 2010

Biosensors, 2021

The CRISPR-Cas9 system has facilitated the genetic modification of various model organisms and ce... more The CRISPR-Cas9 system has facilitated the genetic modification of various model organisms and cell lines. The outcomes of any CRISPR-Cas9 assay should be investigated to ensure/improve the precision of genome engineering. In this study, carbon nanotube-modified disposable pencil graphite electrodes (CNT/PGEs) were used to develop a label-free electrochemical nanogenosensor for the detection of point mutations generated in the genome by using the CRISPR-Cas9 system. Carbodiimide chemistry was used to immobilize the 5′-aminohexyl-linked inosine-substituted probe on the surface of the sensor. After hybridization between the target sequence and probe at the sensor surface, guanine oxidation signals were monitored using differential pulse voltammetry (DPV). Optimization of the sensitivity of the nanogenoassay resulted in a lower detection limit of 213.7 nM. The nanogenosensor was highly specific for the detection of the precisely edited DNA sequence. This method allows for a rapid and e...

Analytical and Bioanalytical Chemistry, 2020

In the present study, a sensitive electrochemical aptamer-based biosensing strategy for human non... more In the present study, a sensitive electrochemical aptamer-based biosensing strategy for human non-small cell lung cancer (NSCLC) detection was proposed using nanofiber-modified disposable pencil graphite electrodes (PGEs). The composite nanofiber was comprised of polyacrylonitrile (PAN) and polypyrrole (PPy) polymers, and fabrication of the nanofibers was accomplished using electrospinning process onto PGEs. Development of the nanofibers was confirmed using scanning electron microscopy (SEM). The high-affinity 5′-aminohexyl-linked aptamer was immobilized onto a PAN/PPy composite nanofibermodified sensor surface via covalent bonding strategy. After incubation with NSCLC living cells (A549 cell line) at 37.5°C, the recognition between aptamer and target cells was monitored by electrochemical impedance spectroscopy (EIS). The selectivity of the aptasensor was evaluated using nonspecific human cervical cancer cells (HeLa) and a nonspecific aptamer sequence. The proposed electrochemical aptasensor showed high sensitivity toward A549 cells with a detection limit of 1.2 × 10 3 cells/mL. The results indicate that our label-free electrochemical aptasensor has great potential in the design of aptasensors for the diagnostics of other types of cancer cells with broad detection capability in clinical analysis.

Electroanalysis, 2007

... The electrode was prepared by cutting the leads into 3 cm long sticks as described previously... more ... The electrode was prepared by cutting the leads into 3 cm long sticks as described previouslyOzkan et al. and Kara et al. [18, 20, 22]. 2.3.2.2. ... 1998, 70, 4670. [13] B. Meric, K. Kerman, D. Ozkan, P. Kara, S. Erensoy, US Akarca, M. Macsini, M. Ozsoz, Talanta 2002, 56, 837. ...

Analytical Methods, 2011

ABSTRACT In the presented study, a novel method is introduced that demonstrates the electrochemic... more ABSTRACT In the presented study, a novel method is introduced that demonstrates the electrochemical detection of influenza B virus based on DNA hybridisation. The detection utilised gold nanoparticles (AuNPs) and Meldola's Blue (MDB), which is utilised as an intercalator label. The developed methodology, combined with a disposable pencil graphite electrode (PGE) and differential pulse voltammetry (DPV), was performed using both synthetic oligonucleotides and polymerase chain reaction (PCR) amplicons. The electrochemical oxidation response of guanine (approximately +0.1 V) and the voltammetric reduction signal of MDB (approximately −0.2 V) were measured before and after hybridisation reactions between a single strand DNAprobe and its complementary target strain (synthetic target or denatured PCR samples). Before the immobilisation of the synthetic DNAprobe of influenza type B virus, the transducer surface was interacted with AuNPs solution using a simple wet adsorption method. AuNP immobilisation was confirmed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to characterise the recognition surface of the genosensor. After the interaction between the PGE and AuNPs, a thiol-linked DNAprobe was immobilised onto the nanoparticle-covered surface. When hybridisation occurred between the probe and its synthetic targets or specific PCR products, the highest MDB signal was observed. The probes were also challenged with equal quantities of non-complementary DNA at the PGE surface for the determination of biosensor selectivity. AuNP-coated electrodes showed high sensitivity and selectivity, specifically in real samples for the detection of the hybridisation reaction. The results obtained in the presented study indicated that the electrode surface area could be enhanced with AuNPs. The detection limit of the genosensor was found to be 54 picomoles for the synthetic target and 3.3 × 107 molecules for the real samples (PCR) in 30 μL of sample volume. Future prospects and analytical performance of the sensor is briefly discussed.

Instrumental methods of analysis modern trends and applications, 2005

Biosensors, 2021

Citation: Kivrak, E.; Pauzaite, T.; Copeland, N.A.; Hardy, J.G.; Kara, P.; Firlak, M.; Yardimci, ... more Citation: Kivrak, E.; Pauzaite, T.; Copeland, N.A.; Hardy, J.G.; Kara, P.; Firlak, M.; Yardimci, A.I.; Yilmaz, S.; Palaz, F.; Ozsoz, M. Detection of CRISPR-Cas9-Mediated Mutations Using a Carbon Nanotube-Modified Electrochemical Genosensor.

Analytica Chimica Acta, Aug 1, 2004

An electrochemical biosensor for the voltammetric detection of DNA sequences related to herpes si... more An electrochemical biosensor for the voltammetric detection of DNA sequences related to herpes simplex viruses (HSV) and discrimination of HSV Type I and Type II viruses from polymerase chain reaction (PCR) amplified real samples were described in this study. The biosensor relies on the covalent immobilization of the 22-mer single stranded oligonucleotides (probe) related to both HSV Type I and Type II sequences and hybridization of these oligonucleotides with their complementary and four bases mismatch containing (four bases MM) sequences at pencil graphite electrodes (PEGE). The extent of hybridization between probe and target sequences was determined by using differential pulse voltammetry (DPV) and Meldola Blue (MDB) was used as the hybridization indicator. As a result of the interaction between MDB and DNA at PEGE surface, the MDB signal observed from probe sequence before hybridization and after hybridization with four bases MM sequence is lower than that observed after hybridization with complementary sequence. The difference between the MDB signals obtained from probe modified, hybrid modified and four bases MM modified PEGE were used to detect and discriminate two types of HSV from PCR amplified real samples. Numerous factors affecting the target hybridization and indicator binding reactions are optimized to maximize the sensitivity.

Biosensors and Bioelectronics, Dec 15, 2010

A label-free bioelectronic detection of aptamer-thrombin interaction based on electrochemical imp... more A label-free bioelectronic detection of aptamer-thrombin interaction based on electrochemical impedance spectroscopy (EIS) technique is reported. Multiwalled carbon nanotubes (MWCNTs) were used as modifiers of screen-printed carbon electrotransducers (SPCEs), showing improved characteristics compared to the bare SPCEs. 5'amino linked aptamer sequence was immobilized onto the modified SPCEs and then the binding of thrombin to aptamer sequence was monitored by EIS transduction of the resistance to charge transfer (Rct) in the presence of 5 mM [Fe(CN)(6)](3-/4-), obtaining a detection limit of 105 pM. This study represents an alternative electrochemical biosensor for the detection of proteins with interest for future applications.

Electroanalysis

The response surface methodology (RSM) is used for optimization of foodborne pathogen detection b... more The response surface methodology (RSM) is used for optimization of foodborne pathogen detection based on label free electrochemical nucleic acid biosensors. Listeria monocytogenes amplicons obtained from food samples are used as model case. The extent of hybridization is determined by using guanine oxidation signals obtained with Differential Pulse Voltammetry and Electrochemical Impedance Spectroscopy. RSM is used to investigate the effects of hybridization parameters including target and salt concentration and hybridization time on the biosensor selectivity. The ratio of electrochemical transductions after hybridization with complementary and noncomplementary targets is the response of the statistical analysis obtaining a detection limit of 267 pM.

RSC Adv., 2014

A label and indicator free electrochemical DNA hybridization detection method based on MnO2-Nps/G... more A label and indicator free electrochemical DNA hybridization detection method based on MnO2-Nps/GCPE was developed. Compared to plain GCPE, a very robust and sensitive genosensor was obtained.

Electrochemical DNA Biosensors, 2012

Journal of Pharmaceutical and Biomedical Analysis, 2005

Electrochemical biosensor for the detection of DNA hybridization using the reduction signal of al... more Electrochemical biosensor for the detection of DNA hybridization using the reduction signal of alpha-naphthol is described. A pencil graphite electrode was used as a working electrode. Capture probes were covalently attached on to the pencil graphite electrode surface (PGE) at the 5' end amino group by using N-(dimethylamino)propyl-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysulfosuccinimide (NHS) as a coupling agent on to PGE. After capture probe immobilization on to PGE surface; probe was hybridized with complementary biotinylated oligonucleotide. Alkaline phosphatase labeled with extravidin (Ex-AP) binds to biotinylated hybrid via biotin-avidin interaction. alpha-Naphthyl phosphate (alpha-NAP) was added and the reaction between alkaline phosphatase (AP) and alpha-NAP was occurred consequently as a substrate of AP, alpha-NAP reduction signal was obtained from this reaction, at -0.100 V by using differential pulse voltammetry (DPV). Other experimental parameters were studied such as; optimizations of hybridization time, and the concentrations of capture probe, biotinylated oligonucleotide and enzyme.

Journal of Pharmaceutical and Biomedical Analysis, 2002

The interaction of an alkylating agent, 4,4?-dihydroxy chalcone (DHC) with calf thymus double str... more The interaction of an alkylating agent, 4,4?-dihydroxy chalcone (DHC) with calf thymus double stranded DNA (dsDNA) and calf thymus single stranded DNA (ssDNA) was studied electrochemically based on the oxidation signals of guanine and adenine by using differential pulse voltammetry (DPV) at carbon paste electrode (CPE). As a result of the alkylation of DHC between the base pairs in dsDNA, the voltammetric signal of guanine and adenine greatly decreased. After the interaction of DHC with ssDNA, a higher decrease in the oxidation signals of guanine and adenine was observed under the same conditions. The partition coefficients of DHC at dsDNA and ssDNA modified CPEs were calculated. The interactions of DHC with synthetic polynucleotides, such as polyguanylic acid and polyadenylic acid were also observed. In addition, the detection limit and the reproducibility were determined by using DPV. The interaction of DHC with dsDNA in solution-phase was also investigated and the results were compared with the ones obtained by surface immobilized dsDNA. The application of electrochemical DNA biosensor for monitoring the DNA Á/alkylating agent interactions was explored. #

Electrochemistry Communications, 2005

A genomagnetic assay coupling of electrochemical monitoring for the detection of wild type hepati... more A genomagnetic assay coupling of electrochemical monitoring for the detection of wild type hepatitis B virus (HBV) DNA in polymerase chain reaction (PCR) amplicons has been described. The development of this technology combined with a disposable sensor, pencil graphite ...

Electrochemistry Communications, 2002

An electrochemical hybridization biosensor based on peptide nucleic acid (PNA) probes is presente... more An electrochemical hybridization biosensor based on peptide nucleic acid (PNA) probes is presented. PNA probes were attached covalently through a competition of free amines on the guanine bases and also at the 5 0 end of the probe, using N-(3-dimethylamino)propyl)-N 0 -ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) onto a carboxylate terminated alkanethiol self-assembled monolayer (SAM) preformed on a gold electrode (AuE). The covalently immobilized probe could selectively hybridize with the target DNA to form a hybrid on the surface despite the bases being attached to the SAM. The changes in the peak currents of methylene blue (3,7-bis(dimethylamino)phenothiazin-5-ium chloride, MB), an electroactive label, were observed upon hybridization of probe with the target. Effective discrimination against point mutation was also obtained. Performance characteristics of the sensor are described, along with future prospects. Ó

Bioelectrochemistry, 2002

Described here are the electrochemical parameters for MB on binding to DNA at hanging mercury dro... more Described here are the electrochemical parameters for MB on binding to DNA at hanging mercury drop electrode (HMDE), glassy carbon electrode (GCE), and carbon paste electrode (CPE) in the solution and at the electrode surface. MB, which interacts with the immobilized calf thymus DNA, was detected by using single-stranded DNA-modified HMDE or CPE (ssDNA-modified HMDE or CPE), bare HMDE or CPE, and double-stranded DNA-modified HMDE or CPE (dsDNA-modified HMDE or CPE) in combination with adsorptive transfer stripping voltammetry (AdTSV), differential pulse voltammetry (DPV), and alternating current voltammetry (ACV) techniques. The structural conformation of DNA and hybridization between synthetic peptide nucleic acid (PNA) and DNA oligonucleotides were determined by the changes in the voltammetric peak of MB. The PNA and DNA probes were also challenged with excessive and equal amount of noncomplementary DNA and a mixture that contained one-base mismatched and target DNA. The partition coefficient was also obtained from the signal of MB with probe, hybrid, and ssDNA-modified GCEs. The effect of probe, target, and ssDNA concentration upon the MB signal was investigated. These results demonstrated that MB could be used as an effective electroactive hybridization indicator for DNA biosensors. Performance characteristics of the sensor are described, along with future prospects. D 1567-5394/02/$ -see front matter D 2002 Elsevier Science B.V. All rights reserved. PII: S 1 5 6 7 -5 3 9 4 ( 0 2 ) 0 0 1 3 1 -7

Bioelectrochemistry, 2005

Electrochemical DNA biosensors have become strong candidates for DNA based analysis. Allele-speci... more Electrochemical DNA biosensors have become strong candidates for DNA based analysis. Allele-specific genotyping is also one of the important research areas, where electrochemical approaches provide promising advances. Recently reported two methods based on electrochemical guanine and colloidal gold (Au) nanoparticle oxidation signals are reviewed and compared with the existing genotyping methods in this report. D

Electroanalysis

The response surface methodology (RSM) is used for optimization of foodborne pathogen detection b... more The response surface methodology (RSM) is used for optimization of foodborne pathogen detection based on label free electrochemical nucleic acid biosensors. Listeria monocytogenes amplicons obtained from food samples are used as model case. The extent of hybridization is determined by using guanine oxidation signals obtained with Differential Pulse Voltammetry and Electrochemical Impedance Spectroscopy. RSM is used to investigate the effects of hybridization parameters including target and salt concentration and hybridization time on the biosensor selectivity. The ratio of electrochemical transductions after hybridization with complementary and noncomplementary targets is the response of the statistical analysis obtaining a detection limit of 267 pM.

Journal of the Iranian Chemical Society, 2010