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    Amperometric immunosensor developed for sensitive detection of SARS-CoV-2 spike S1 protein in combined with portable device
    (Elsevier, 2022) Erdem, Arzum; Senturk, Huseyin; Yildiz, Esma; Maral, Meltem
    In this present study, an amperometric immunosensor was developed based on disposable screen-printed carbon electrode (SPCE) for specific and sensitive detection of SARS-CoV-2 S1 protein. Anti-SARS-CoV-2 S1 monoclonal antibody was firstly immobilized onto the electrode surface. Then, the sandwich complex was formed by addition of S1 protein, secondary antibody and HRP-IgG, respectively. Chronoamperometry measurements were done in the presence of TMB mediator and the detection of SARS-CoV-2 S1 protein was performed by using 10 mu L sample. The limit of detection (LOD) was found to be 0.19 ng/mL (equals to 24.7 amol in 10 mu L sample) in the linear range of 0.5-10 ng/mL obtained in buffer medium. The applicability of this assay was investigated in the linear range of 0.5-3 ng/mL S1 protein in artificial saliva medium with the LOD as 0.13 ng/mL (equals to 16.9 amol in 10 mu L sample). The selectivity study was examined in the presence of Hemagglutinin antigen (HA) in both mediums; buffer and artificial saliva while resulting with the successful discrimination between S1 protein and HA. The one of ultimate goals of our study is to present the possible implementation of this assay to point of care (POC) analysis. Under this aim, this assay was performed in combination with a portable device that is the commercial electrochemical analyzer. Amperometric detection of S1 protein in the range of 0.5-5 ng/mL was also successfully performed in artificial saliva medium with a resulting LOD as 0.15 ng/mL (equals to 19.5 amol in 10 mu L sample). In addition, a selectivity study was similarly carried out by portable device.
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    Amplified electrochemical DNA-sensing of nanostructured metal oxide films deposited on disposable graphite electrodes functionalized by chemical vapor deposition
    (Elsevier Science Sa, 2009) Mathur, Sanjay; Erdem, Arzum; Cavelius, Christian; Barth, Sven; Altmayer, Jessica
    Metal oxide nanostructures offer interesting possibilities to design functional surfaces for biosensing applications, for instance, through higher surface area leading to enhanced immobilization of biomolecules, which increases the detection limit. Herein, an amplified electrochemical sensing method has been presented for the detection of DNA based on the readout resulting from chemical oxidation of guanine on nanoscaled metal oxides (TiO(2), SnO(2) and Fe(3)O(4)) obtained by chemical vapor deposition (CVD) onto pencil graphite electrode (PGE) as electrochemical transducer. The proposed strategy is suitable to produce cost-effective disposable sensor elements enabling quantitative detection of nanomolar concentrations of DNA. When preparing these metal oxide surfaces by CVD onto PGEs, the various experimental conditions; such as, the effect of different concentrations of 20 mer-bases DNA oligonucleotide (ODN20), and the surface pretreatment steps were Studied to obtain better surface properties for DNA immobilization. The detection limit estimated for signal-to-noise ratios >3 corresponds to 21.3, 519 and 45.8 nmole/ml ODN20 concentrations for PGEs modified with TiO(2), SnO(2) and Fe(3)O(4) films, respectively. The electrochemical detection of DNA onto metal oxide@PGEs is discussed together with the application potential. (c) 2008 Elsevier B.V. All rights reserved.
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    Aptasensor platform based on carbon nanofibers enriched screen printed electrodes for impedimetric detection of thrombin
    (Elsevier Science Sa, 2015) Erdem, Arzum; Congur, Gulsah; Mayer, Guenter
    Herein, impedimetric detection of THR could be achieved using an aptasensing platform based on carbon nano-fibers enriched screen-printed electrodes (CNF-SPE). The resistance to charge transfer (R-ct) was recorded using electrochemical impedance spectroscopy (EIS) technique before/after the immobilization of amino-modified DNA aptamer (APT) selective to thrombin (THR) onto the surface of CNF-SPEs and the specific interaction between APT and THR. The selectivity of the aptasensor was also tested in the presence of a random DNA oligonucleotide and a DNA aptamer that were different from THR specific APT. The impedimetric aptasensing of target protein was also explored in the fetal bovine serum (FBS) medium at different concentration levels of THR. Additionally, the selectivity of the aptasensor was tested against bovine serum albumin (BSA) and protein C (PC) in FBS medium. This CNF-SPE based aptasensor platform allows a reliable, sensitive and selective impedimetric monitoring of THR. (C) 2015 Elsevier B.V. All rights reserved.
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    Aptasensor platform based on electrochemical Paper-Based analytical device for histamine detection
    (Elsevier, 2024) Eksin, Ece; Erdem, Arzum
    This paper outlines a simple, affordable, and highly flexible rapid prototyping technique for creating electrochemical paper-based analytical devices (ePADs). The craft cutter printer used for ePAD fabrication offers high flexibility and simplicity, eliminating the need for specialized equipment such as a wax printer by generating both electrode patterns and hydrophilic barriers. The ePAD was utilized to construct an aptasensor for the determination of histamine, which is essential for several physiological functions, including gastric secretion, narcolepsy, cell differentiation, cell growth, neurotransmission, and neuromodulation. Following the preparation of an ePAD with a unique design specific to this work, surface characterization was conducted using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A single-use aptasensor was created by immobilizing histamine-specific aptamer onto the working electrode surface of the ePAD. By optimizing all experimental parameters, histamine detection was successfully performed using the differential pulse voltammetry (DPV) technique. The reproducibility and selectivity of the aptasensor were examined, and its potential applicability to real samples was tested in an artificial saliva. These findings suggest that the ePAD-based aptasensor provides a cost-effective and reliable method for histamine detection, with potential applications in various bioanalytical contexts.
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    Carbon Nanotubes Modified Graphite Electrodes for Monitoring of Biointeraction Between 6-Thioguanine and DNA
    (Wiley-V C H Verlag Gmbh, 2017) Unal, Didem Nur; Eksin, Ece; Erdem, Arzum
    In this present study, single-walled carbon nanotubes (SWCNT) modified disposable pencil graphite electrodes (SWCNT-PGEs) were developed for the electrochemical monitoring of anticancer drug, and its interaction with double stranded DNA (dsDNA). Under this aim, SWCNT-PGEs were applied for the first time in the literature to analyse of 6-Thioguanine (6-TG), and also to investigate its interaction with DNA by voltammetric and impedimetric methods. The surface morphologies of PGE and SWCNT-PGE were explored using scanning electron microscopy (SEM) and electrochemical characterization of unmodified/modified electrodes was performed by cyclic voltammetry (CV). Experimental parameters; such as, the concentration of 6-TG and its interaction time with dsDNA were optimized by using differential pulse voltammetry (DPV). Additionally, the interaction of 6-TG with dsDNA was studied in case of different interaction times by electrochemical impedance spectroscopy (EIS) in contrast to voltammetric results. The detection limit of 6-TG was found to be 0.25 mu M by SWCNT-PGE.
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    Carbon quantum dot modified electrodes developed for electrochemical monitoring of Daunorubicin-DNA interaction
    (Elsevier Science Sa, 2020) Eksin, Ece; Senturk, Huseyin; Zor, Erhan; Bingol, Haluk; Erdem, Arzum
    The carbon quantum dot (cQD) modified disposable pencil graphite electrodes were developed for the first time in this study for electrochemical monitoring of drug-DNA interaction. the biomolecular interaction between calf thymus double stranded DNA (ctDNA) and an anthracycline antineoplastic drug, Daunorubicin (DNR) was investigated by differential pulse voltammetry (DPV) technique. For this purpose, experimental conditions, such as, the concentration of ctDNA, concentration of DNR and interaction time were optimized. Under optimum conditions, the detection limits of DNR and ctDNA were found to be 0.02 mu g/mL and 0.89 mu g/mL, respectively. the effect of interaction time between DNR and ctDNA was explored upon to the changes at both DNR and guanine oxidation signals. Drug-DNA interaction process was also examined by electrochemical impedance spectroscopy (EIS) technique.
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    Carboxylated-Graphene Decorated Pencil Graphite Electrode as a Platform for Voltammetric Detection of DNA
    (Electrochemical Soc Inc, 2017) Zor, Erhan; Eksin, Ece; Findik, Mukerrem; Bingol, Haluk; Erdem, Arzum
    Continuous technology miniaturization using nanoscale materials allows the design of DNA sensing platforms with not only far larger surface areas but alsomore effective characteristics. We herein synthesized benzoic acid-functionalized graphene oxide (GOB), characterized by FT-IR, XPS, Raman Spectroscopy, TGA, SEM, TEM techniques and then it was utilized as a supporting material. Due to the benzoic acid groups available on the surface of GOB, fsDNA was directly immobilized onto the disposable pencil graphite electrode (PGE). The limit of detection (LOD) for fish sperm DNA (fsDNA) concentration was estimated to be 1.11 mu g/mL by using differential pulse voltammetry (DPV) technique. It can be assumed that this simple modification protocol offers an alternative for the quick and robust monitoring of sequence-specific nucleic acids avoiding the need of complex or expensive requirements, and it can pave the way for new opportunities to design more novel DNA sensing strategies and applications on disposable platforms. (c) 2017 The Electrochemical Society. All rights reserved.
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    Characterization of poly(vinylferrocenium) coated surfaces and their applications in DNA sensor technology
    (Springer, 2010) Kuralay, Filiz; Erdem, Arzum; Abaci, Serdar; Ozyoruk, Haluk; Yildiz, Attila
    Poly(vinylferrocenium) (PVF+) modified gold (Au) electrode was developed in this study for the electrochemical sensing of deoxyribonucleic acid (DNA) hybridization based on the oxidation signals of polymer and guanine, and also for the electrochemical investigation of interaction of anticancer drug, mitomycin C (MC) and DNA immobilized onto PVF+ modified Au electrode. PVF+ modified Au electrode was prepared by electrooxidation of poly(vinylferrocene) PVF at +0.7 V versus Ag/AgCl reference electrode. The polymer modified electrode and DNA immobilized polymer modified electrode were characterized by X-ray photoelectron (XPS), Fourier transform infrared-attenuated total reflentance (FTIR-ATR) and alternating current (AC) impedance spectroscopy. For application studies, differential pulse voltammetry (DPV) technique was used.
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    Characterization of redox polymer based electrode and electrochemical behavior for DNA detection
    (Elsevier Science Bv, 2009) Kuralay, Filiz; Erdem, Arzum; Abaci, Serdar; Ozyoruk, Haluk; Yildiz, Attila
    Characterization of redox polymer, poly(vinylferrocenium) perchlorate (PVF+ClO4-) coated as a film on Pt electrodes, and the detection of DNA based on the electrochemical behavior of the polymer were described in this study. PVF+ClO4- Modified electrodes were prepared by the electrooxidation of poly(vinylferrocene) (PVF), and DNA immobilized polymer modified electrode was then prepared. The characterization of the polymer modified electrodes were performed by scanning tunneling Microscopy (STM), Raman spectroscopy and alternating current (AC) impedance. The effects of DNA concentration. pH, and polymer films in various thicknesses based on the electrode response were also investigated. The electrochemical behavior of DNA modified polymer electrode by using double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) was compared. DNA hybridization was also investigated. (C) 2009 Elsevier B.V. All rights reserved.
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    Chitosan-carbon Nanofiber Modified Single-use Graphite Electrodes Developed for Electrochemical Detection of DNA Hybridization Related to Hepatitis B Virus
    (Wiley-V C H Verlag Gmbh, 2016) Eksin, Ece; Erdem, Arzum
    Chitosan (CHIT) and carbon nanofiber (CNF) modified pencil graphite electrodes (PGEs) were developed for the first time in the present study for enhanced monitoring of DNA hybridization. CHIT-CNF modified PGE, CHIT modified PGE and unmodified PGE were firstly characterized by scanning electrone microscopy (SEM), and the electrochemical behaviour of each electrode was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The optimization of experimental studies; CNF concentration, or DNA probe concentration was performed by differential pulse voltammetry (DPV) technique. The sequence-selective DNA hybridization related to Hepatitis B virus (HBV) was then performed in the case of hybridization between HBV probe and its target DNA, or different non-complementary DNA sequences (NC1 and NC2), and also the hybridization case in the mixture samples containing both target and NC sequences in the ratio of 1: 1. CHIT-CNF-PGEs presented very effective discrimination of HBV DNA hybridization, which also presented high sensitivity and better reproducibility due to the unique chemical and structural properties of CNF.
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    Chitosan-ionic liquid modified single-use sensor for electrochemical monitoring of sequence-selective DNA hybridization
    (Elsevier Science Bv, 2014) Erdem, Arzum; Muti, Mihrican; Mese, Fehmi; Eksin, Ece
    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. (C) 2013 Elsevier B.V. All rights reserved.
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    Chitosan/Nitrogen Doped Reduced Graphene Oxide Modified Biosensor for Impedimetric Detection of microRNA
    (Wiley-V C H Verlag Gmbh, 2018) Eksin, Ece; Bikkarolla, Santosh Kumar; Erdem, Arzum; Papakonstantinou, Pagona
    The development of a low-cost and disposable biosensor platform for the sensitive and rapid detection of microRNAs (miRNAs) is of great interest for healthcare, pharmaceuticals, and medical science. We designed an impedimetric biosensing platform using Chitosan (CHIT)/nitrogen doped reduced graphene oxide (NRGO) conductive composite to modify the surface of pencil graphite electrodes (PGE) for the sensitive detection of miRNAs. An initial optimisation protocol involved investigation of the effect of NRGO concentration and miR 660DNA probe concentration on the response of the modified electrode. After the optimization protocol, the sequence-selective hybridization between miR 660 DNA probe and its RNA target was evaluated by measuring changes on charge transfer resistance, R-ct values. Moreover, the selectivity of impedimetric biosensor was tested in the presence of non-complementary miRNA (NC) sequences, such as miR 34a and miR16. The hybridization process was examined both in phosphate buffer (PBS) and in PBS diluted fetal bovine serum (FBS:PBS) solutions. The biosensor demonstrated a detection limit of 1.72g/mL in PBS and 1.65g/mL in FBS:PBS diluted solution. Given the easy, quick and disposable attributes, the proposed conductive nanocomposite biosensor platform shows great promise as a low-cost sensor kit for healthcare monitoring, clinical diagnostics, and biomedical devices.
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    Cobalt Phthalocyanine-Ionic Liquid Composite Modified Electrodes for the Voltammetric Detection of DNA Hybridization Related to Hepatitis B Virus
    (Mdpi, 2021) Yarali, Ece; Erdem, Arzum
    In this study, cobalt phthalocyanine (CoPc) and ionic liquid (IL) modified pencil graphite electrodes (PGEs) were designed and implemented to detect sequence-selective DNA hybridization related to the Hepatitis B virus (HBV). The surface characterization of CoPc-IL-PGEs was investigated by scanning electron microscopy (SEM), and the electrochemical behavior of electrodes were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The voltammetric detection of hybridization was investigated by evaluating the guanine oxidation signal, measured by differential pulse voltammetry (DPV) technique. The implementation of our biosensor to serum samples was also examined using fetal bovine serum (FBS). The detection limit was established as 0.19 mu g/mL in phosphate buffer solution (PBS) (pH 7.40) and 2.48 mu g/mL in FBS medium. The selectivity of our assay regarding HBV DNA hybridization in FBS medium was tested in the presence of other DNA sequences. With this aim, the hybridization of DNA probe with non-complementary (NC) or mismatched DNA sequence (MM), or in the presence of mixture samples containing DNA target NC (1:1) or DNA target MM (1:1), was studied based on the changes in guanine signal.
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    The Comparison of Electrochemical Assay and Agarose Gel Electrophoresis for the Determination of DNA Damage Induced by Kainic Acid
    (Wiley-V C H Verlag Gmbh, 2009) Karadeniz, Hakan; Armagan, Guliz; Erdem, Arzum; Turunc, Ezgi; Caliskan, Ayfer; Kanit, Lutfiye; Yalcin, Ayfer
    A possible DNA damage after interaction of kainic acid (KA) with calf thymus double stranded DNA and genomic DNA was herein determined in in vitro and in vivo conditions using; electrochemical assay and agarose gel electrophoresis. The changes in guanine signal were detected as an indicator of DNA damage in genomic DNA samples isolated from 1 or 10 mg/kg KA-treated animals. The decreased levels of guanine signal were found as 29% and 33% by 1 and 10 mg/kg KA treatment when compared to controls, respectively. The results of gel electrophoresis confirmed DNA damage obtained in identical samples by electrochemical method.
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    The Comparison of Electrochemical Assay and Agarose Gel Electrophoresis for the Determination of DNA Damage Induced by Kainic Acid
    (Wiley-V C H Verlag Gmbh, 2009) Karadeniz, Hakan; Armagan, Guliz; Erdem, Arzum; Turunc, Ezgi; Caliskan, Ayfer; Kanit, Lutfiye; Yalcin, Ayfer
    A possible DNA damage after interaction of kainic acid (KA) with calf thymus double stranded DNA and genomic DNA was herein determined in in vitro and in vivo conditions using; electrochemical assay and agarose gel electrophoresis. The changes in guanine signal were detected as an indicator of DNA damage in genomic DNA samples isolated from 1 or 10 mg/kg KA-treated animals. The decreased levels of guanine signal were found as 29% and 33% by 1 and 10 mg/kg KA treatment when compared to controls, respectively. The results of gel electrophoresis confirmed DNA damage obtained in identical samples by electrochemical method.
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    Cost-Effective Cholesterol Monitoring by Enzyme-Based Electrochemical Assay
    (Wiley-V C H Verlag Gmbh, 2024) Eksin, Ece; Senturk, Huseyin; Erdem, Arzum
    Herein we present a practical, disposable, enzyme-based electrochemical biosensor to revolutionize a rapid and precise measurement of cholesterol level in saliva. To create a biosensor that can measure cholesterol levels, cholesterol oxidase (ChOx) was immobilized on disposable pencil graphite electrode (PGE) via EDC/NHS chemistry. This ChOx-PGE biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). Various critical experimental parameters, including nafion concentration, enzyme concentration, enzyme-cholesterol interaction time, were optimized ensuring consistency and precision in our results and maintained constant throughout the experiments. Under optimum conditions, the detection limit was found to be 62 mu M and the sensitivity of the sensor was calculated as 1112.8 Ohm mM-1 cm-2. The potential interferences such as glucose, ascorbic acid, uric acid, cysteine was selected to test the selectivity and no significant response was observed. Finally, the proposed biosensor was effectively employed to measure cholesterol level in saliva. This biosensor boasts a rapid response time of just 20 minutes and achieves a remarkable detection limit of 95 mu M for salivary cholesterol, surpassing existing techniques. Our assay not only offers an innovative solution for cholesterol monitoring but also opens new horizons in point-of-care diagnostics with its disposable and practical design. We report a practical, disposable, enzyme-based electrochemical assay for measuring salivary cholesterol levels. Electrochemical impedance spectroscopy is used for the sensing of cholesterol after its interaction with cholesterol oxidase onto PGE surface. The proposed biosensor ensures a rapid response time (20-minute) and low detection limit (95 mu M). This approach promises a practical, point-of-care diagnostic solution for cholesterol monitoring.image
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    CUPRAC colorimetric and electroanalytical methods determining antioxidant activity based on prevention of oxidative DNA damage
    (Academic Press Inc Elsevier Science, 2017) Uzunboy, Seda; Cekic, Sema Demirci; Eksin, Ece; Erdem, Arzum; Apak, Resat
    An unbalanced excess of oxygen/nitrogen species (ROS/RNS) can give oxidative hazard to DNA and other biomacromolecules under oxidative stress conditions. While the 'comet' assay for measuring DNA damage is neither specific nor practical, monitoring oxidative changes on individual DNA bases and other oxidation products needs highly specialized equipment and operators. Thus, we developed a modified CUPRAC (cupric ion reducing antioxidant capacity) colorimetric method to determine the average total damage on DNA produced by Fenton oxidation, taking advantage of the fact that the degradation products of DNA but not the original macromolecule is CUPRAC responsive. The DNA protective effects of water-soluble antioxidants were used to devise a novel antioxidant activity assay, considered to be physiologically more realistic than those using artificial probes. Our method, based on the measurement of DNA oxidative products with CUPRAC colorimetry proved to be 2 orders-of-magnitude more sensitive than the widely used TBARS (thiobarbituric acid-reactive substances) colorimetric assay used as reference. Additionally, the DNA damage was electrochemically investigated using pencil graphite electrodes (PGEs) as DNA sensor platform in combination with differential pulse voltammetry (DPV). The interaction of the radical species with DNA in the absence/presence of antioxidants was detected according to the changes in guanine oxidation signal. (C) 2016 Elsevier Inc. All rights reserved.
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    Dendrimer enriched single-use aptasensor for impedimetric detection of activated protein C
    (Elsevier Science Bv, 2014) Erdem, Arzum; Congur, Gulsah
    A novel impedimetric aptasensor for detection of human activated protein C (APC) was introduced for the first time in the present study. An enhanced sensor response was obtained using poly(amidoamine) (PAMAM) dendrimer having 16 succinamic acid surface groups (generation 2, G2-PS), that was modified onto the surface of screen printed graphite electrode (G2-PS/SPE). An amino modified DNA aptamer was then immobilized onto the surface of G2-PS modified SPE. The selective interaction of APT with its cognate protein, APC was investigated using different electrochemical techniques; differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The microscopic characterization was consecutively performed before/after each modification/interaction step using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The selectivity of aptasensor was tested in the presence of numerous proteins; protein C, thrombin, bovine serum albumin, factor Va and chromogenic substrate in different buffer mediums. The APC detection in the artificial serum; fetal bovine serum (FBS) was also performed impedimetrically. This dendrimer modified aptasensor technology brings several advantages: being single-use, fast screening with low-cost per measurement and resulting in sensitive detection of APC with the detection limits of 0.74 mu g/mL (0.46 pmol in 35 mu L sample) in buffer medium, and 2.03 mu g/mL (1.27 pmol in 35 mu L sample) in serum. (C) 2014 Elsevier B.V. All rights reserved.
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    Dendrimer modified 8-channel screen-printed electrochemical array system for impedimetric detection of activated protein C
    (Elsevier Science Sa, 2014) Erdem, Arzum; Congur, Gulsah
    The 8-channel screen-printed electrochemical array system (MULTI-SPE8) was developed as an impedimetric aptasensor, and applied for monitoring the interaction between DNA aptamer (DNA-APT) and its cognate protein, human activated protein C (APC), which is the key enzyme of the protein C pathway. Poly(amidoamine) (PAMAM) dendrimer having 16 succinamic acid surface groups (generation 2, G2-PS) was utilized in order to modify the surface of each carbon-based working electrode in MULTI-SPE8, and accordingly, an enhanced sensor response was recorded. Amino linked DNA-APT was then immobilized onto the surface of G2-PS/MULTI-SPE8, and its interaction with APC was explored. After the optimization of the experimental conditions; such as G2-PS, DNA-APT and APC concentration, the selectivity of the electrochemical aptasensor array system was tested in the presence of numerous biomolecules: protein C (PC), thrombin (THR), bovine serum albumin (BSA), factor Va (FVa) and chromogenic substrate (KS) in buffer media, or in the artificial serum: fetal bovine serum (FBS). The dendrimer-modified aptasensor technology based on MULTI-SPE8 has several advantages, such as disposable, fast screening of analyte at eight channels in one batch with low cost per measurement and resulting in a sensitive and selective indirect method for the analysis of APC, with the detection limits of 1.81 mu g/mL (0.64 pmol in 20 mu L sample) in buffer solution and 0.02 mu g/mL (8.22 fmol in 20 mu L sample) in diluted FBS. (C) 2014 Elsevier B.V. All rights reserved.