Dilek Demirkol - Academia.edu (original) (raw)
Papers by Dilek Demirkol
Macromolecular Bioscience, 2015
Materials Science and Engineering: C, 2014
Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. ... more Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. To obtain immobilization platforms for both pyranose oxidase (PyOx) and Gluconobacter oxydans, the graphite electrode surface was modified with the polymer of 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) which has free amino groups on the surface for further bioconjugation reactions with the biomolecules. Initially, the electrode surface was covered with HKCN via electropolymerization. Then, either PyOx or G. oxydans cell was stabilized using glutaraldehyde as a cross-linker. After optimization of biosensors, analytical characterization and surface imaging studies were investigated. The change of current depends on glucose concentration between 0.05-1.0 mM and 0.25-2.5 mM with HKCN/PyOx and HKCN/G. oxydans biosensors in batch systems. Also, the calibration graphs were obtained for glucose in FIA mode, and in this case, linear ranges were found to be 0.01-1.0 mM and 0.1-7.5 mM for HKCN/PyOx and HKCN/G. oxydans, respectively.
A novel ferrocenyldithiophosphonate (TPFc) functionalized monomer and its conductive copolymer we... more A novel ferrocenyldithiophosphonate (TPFc) functionalized monomer and its conductive copolymer were
synthesized, characterized and its potential use for biosensor applications was investigated. The structure of
copolymer (P(TPFc-co-TPA)) which has free amino and ferrocene (Fc) groups was characterized by various
techniques such as NMR and cyclic voltammetry. Afterwards, covalent immobilization of glucose oxidase
(GOx) was carried out with glutaraldehyde using the amino groups on both the conducting copolymer
and GOx. Fc on the backbone played a role as redox mediator during the electrochemical
measurements. Therefore, the proposed copolymer P(TPFc-co-TPA) served as a functional platform for
stable biomolecule immobilization and for obtaining the oxygen free mediated electrochemical
responses. The current signals were recorded using glucose as substrate, at +0.45 V vs. Ag/AgCl in Naacetate
buffer (pH 4.5; 50 mM). Additionally, Kapp
m (20.23 mM), Imax (3.03 mA) and sensitivity values were determined. Finally, the biosensor was successfully applied to glucose analysis
in various beverages and the results were compared with data obtained from the spectrophotometric
glucose detection kit as a reference method.
Langmuir, 2015
A robust drug delivery system based on nano-sized amphiphilic star-hyperbranched block copolymer,... more A robust drug delivery system based on nano-sized amphiphilic star-hyperbranched block copolymer, namely poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (Arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulted peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-Maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (Doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin αvβ3 receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition towards U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin αvβ3 receptor expressing tumor cells.
Sensors and Actuators B: Chemical, 2013
RSC Adv., 2014
Here we report the synthesis, characterization and application of calixarene (Calix) modified mon... more Here we report the synthesis, characterization and application of calixarene (Calix) modified montmorillonite (Mt) as a platform for bio-applications such as biomolecule immobilization and biosensing technologies. This modification enhanced the biomolecule immobilization capability of Mt.
Talanta, 2011
An electrochemical biosensor for detection of fructose in food samples was developed by immobiliz... more An electrochemical biosensor for detection of fructose in food samples was developed by immobilization of fructose dehydrogenase (FDH) on cysteamine and poly(amidoamine) dendrimers (PAMAM)-modified gold electrode surface. Electrochemical analysis was carried out by using hexacyanoferrate (HCF) as a mediator and the response time was 35s at +300 mV vs. Ag/AgCl. Moreover, some parameters such as pH, enzyme loading and type of PAMAM (Generations 2, 3 and 4) were investigated. Then, the FDH biosensor was calibrated for fructose in the concentration range of 0.25-5.0mM. To evaluate its utility, the FDH biosensor was applied for fructose analysis in real samples. Finally, obtained data were compared with those measured with HPLC as a reference method.
Sensors and Actuators B: Chemical, 2014
Microchimica Acta, 2011
We describe a microbial sensor based on Pseudomonas fluorescens cells that was prepared by modify... more We describe a microbial sensor based on Pseudomonas fluorescens cells that was prepared by modifying graphite electrodes with chitosan and carbon nanotubes. Chronoamperometry was performed at +0.3 V in the presence of hexacyanoferrate as a mediator and revealed a good response to glucose which is linear in the 1.0 to 5.0 mM concentration range. Linearity was defined by the equation of y=102.120x−13.279 (R 2 =0.998) (y shows current density as nA.cm −2 and x shows glucose concentration in mM). The effect of the CNTs on the response was compared to that of electrodes made without CNTs.
Materials Science and Engineering: C, 2011
A series of well-defined amphiphilic graft copolymers with hydrophobic polysulfone (PSU) as backb... more A series of well-defined amphiphilic graft copolymers with hydrophobic polysulfone (PSU) as backbones and hydrophilic poly(ethylene glycol) (PEG) as side chains were synthesized and characterized. For this purpose, PSUs were converted to azido-functionalized polymers ...
Materials Science and Engineering: C, 2013
An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated b... more An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated by construction of gold nanoparticles (AuNPs) on the surface of polyamidoamine dendrimer (PAMAM) modified gold electrode. Glucose oxidase (GOx) was used as a model enzyme and was immobilized onto the gold surface forming a self assembled monolayer via FcSH and cysteamine. Cyclic voltammetry and amperometry were used for the characterization of electrochemical response towards glucose substrate. Following the optimization of medium pH, enzyme loading, AuNP and FcSH amount, the linear range for the glucose was studied and found as 1.0 to 5.0 mM with the detection limit (LOD) of 0.6 mM according to S/N=3. Finally, the proposed Au/AuNP/(FcSH+Cyst)/PAMAM/GOx biosensor was successfully applied for the glucose analysis in beverages, and the results were compared with those obtained by HPLC.
Journal of Polymer Science Part A: Polymer Chemistry, 2011
Journal of Materials Chemistry, 2012
Herein, the phase-transfer reaction of quantum dots (QDs) with amine-terminated polyamidoamine (P... more Herein, the phase-transfer reaction of quantum dots (QDs) with amine-terminated polyamidoamine (PAMAM) dendrimers with controllable ligand molar ratios was achieved. The unique properties of PAMAM allowed us to build up structurally and electrostatically stabilized water soluble QD complexes. Synthesized conjugates were characterized in terms of fluorescence and UV-Vis profiles, hydrodynamic size, number of surface dendrimer groups, and stability. Cytotoxic effects of conjugates for MCF-7, A-549 and HEP-G2 cancer cells were assessed based on cell viability using MTT assay. Cytotoxicity results were expressed as no observable adverse effect concentration (NOAEC), 50% inhibitory concentration (IC 50 ) and total lethal concentration (TLC) values (mM). Furthermore, HER2 receptor-mediated targeting efficiency of antibody labelled P/QDs conjugates was evaluated by successful staining of MCF-7 cells with bioconjugates. Uniquely, effective cell internalization was achieved with well-characterized antibody coupled P/QDs in contrast to antibody free P/QDs conjugates. Fluorescence microscopy images demonstrated that the designed PAMAM-derivatized QDs nanoparticles show great potential in the areas of cellular imaging and targeted therapy.
Journal of Macromolecular Science, Part A, 2011
Journal of Macromolecular Science, Part A, 2013
Accumulation of cholesterol in human blood can cause several health problems such as heart diseas... more Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-cop-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H 2 O 2 at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.
Food Chemistry, 2011
Gold nanoparticle (AuNP) modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)b... more Gold nanoparticle (AuNP) modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH 2 ) was used as the biosensing platform for glucose analysis. Electrochemical measurements were carried out by following the consumed oxygen due to the enzymatic reaction of glucose oxidase (GOx) at À0.7 V vs Ag/AgCl. Optimisation of pH, enzyme loading, stability experiments were carried out. Effect of NP was investigated by monitoring the signal responses at different AuNP sizes and amounts. A linear relation of y = 1.597x + 0.264 (R 2 = 0.993) was found for glucose concentrations between 0.002 and 5.0 mM. The analytical characteristics of the system were also evaluated for glucose determination in flow injection analysis (FIA) mode. Finally, the system was checked for glucose detection on real samples.
Food Analytical Methods, 2012
An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) in... more An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) inhibitor. LOX was immobilized in carbon paste electrode and the amperometric detection of hydroperoxy linoleic acid due to the enzymatic reaction using linoleic acid as a substrate was monitored at +0.9 V versus Ag/AgCl. The decrease in biosensor response in the presence of caffeic acid was found to be correlated with the inhibitor concentration. Diode array detector and LOX biosensor was used as an electrochemical detector for the analysis of this compound. All data were given as a comparison of two systems.
Food Analytical Methods, 2012
... Chim Acta 572:248252 Jia J, Tang M, Chen X, Qi L, Dong S (2003) Biosens Bioelectron 18:1023... more ... Chim Acta 572:248252 Jia J, Tang M, Chen X, Qi L, Dong S (2003) Biosens Bioelectron 18:10231029 Kara S, Keskinler ... AN (2001) Biosens Bioelectron 16:10011007 Mulchandani P, Chen W, Mulchandani A (2006) Anal Chim Acta 568:217221 Odaci D, Timur S, Telefoncu ...
Dyes and Pigments, 2011
Optical glucose oxidase (GOx) arrays based on pH sensitive fluorescent dye (2-(4-tolyl)-4-[4-(1,4... more Optical glucose oxidase (GOx) arrays based on pH sensitive fluorescent dye (2-(4-tolyl)-4-[4-(1,4,7,10tetraoxa-13-azacyclopentadecyl)benzylidene]-5-oxazolone) (CPO) has been constructed. The arrays were prepared by spotting of CPO and GOx together with tetraethoxysilane (TEOS)/Chitosan (CHIT) mixture via a microarrayer. After optimization studies, analytical characterization of enzyme arrays were carried out. The fluorescence intensity of the system was linearly correlated to glucose concentration in the range of 1.0e30.0 mM (in potassium phosphate buffer; 2.5 mM at pH 7.0). Furthermore, the developed arrays were used to analyze glucose in some beverages and HPLC was used as a reference method for independent glucose analysis.
Colloids and Surfaces B: Biointerfaces, 2014
We describe here the synthesis, characterization, bioconjugation, and application of water-solubl... more We describe here the synthesis, characterization, bioconjugation, and application of water-soluble thioglycolic acid TGA-capped CdTe/CdS quantum dots (TGA-QDs) for targeted cellular imaging. Antihuman epidermal growth factor receptor 2 (HER2) antibodies were conjugated to TGA-QDs to target HER2-overexpressing cancer cells. TGA-QDs and TGA-QDs/anti-HER2 bioconjugates were characterized by fluorescence and UV-Vis spectroscopy, X-ray diffraction (XRD), hydrodynamic sizing, electron microscopy, and gel electrophoresis. TGA-QDs and TGA-QDs/anti-HER2 were incubated with cells to examine cytotoxicity, targeting efficiency, and cellular localization. The cytotoxicity of particles was measured using an MTT assay and the no observable adverse effect concentration (NOAEC), 50% inhibitory concentration (IC 50 ), and total lethal concentration (TLC) were calculated. To evaluate localization and targeting efficiency of TGA-QDs with or without antibodies, fluorescence microscopy and flow cytometry were performed. Our results indicate that antibody-conjugated TGA-QDs are well-suited for targeted cellular imaging studies.
Macromolecular Bioscience, 2015
Materials Science and Engineering: C, 2014
Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. ... more Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. To obtain immobilization platforms for both pyranose oxidase (PyOx) and Gluconobacter oxydans, the graphite electrode surface was modified with the polymer of 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) which has free amino groups on the surface for further bioconjugation reactions with the biomolecules. Initially, the electrode surface was covered with HKCN via electropolymerization. Then, either PyOx or G. oxydans cell was stabilized using glutaraldehyde as a cross-linker. After optimization of biosensors, analytical characterization and surface imaging studies were investigated. The change of current depends on glucose concentration between 0.05-1.0 mM and 0.25-2.5 mM with HKCN/PyOx and HKCN/G. oxydans biosensors in batch systems. Also, the calibration graphs were obtained for glucose in FIA mode, and in this case, linear ranges were found to be 0.01-1.0 mM and 0.1-7.5 mM for HKCN/PyOx and HKCN/G. oxydans, respectively.
A novel ferrocenyldithiophosphonate (TPFc) functionalized monomer and its conductive copolymer we... more A novel ferrocenyldithiophosphonate (TPFc) functionalized monomer and its conductive copolymer were
synthesized, characterized and its potential use for biosensor applications was investigated. The structure of
copolymer (P(TPFc-co-TPA)) which has free amino and ferrocene (Fc) groups was characterized by various
techniques such as NMR and cyclic voltammetry. Afterwards, covalent immobilization of glucose oxidase
(GOx) was carried out with glutaraldehyde using the amino groups on both the conducting copolymer
and GOx. Fc on the backbone played a role as redox mediator during the electrochemical
measurements. Therefore, the proposed copolymer P(TPFc-co-TPA) served as a functional platform for
stable biomolecule immobilization and for obtaining the oxygen free mediated electrochemical
responses. The current signals were recorded using glucose as substrate, at +0.45 V vs. Ag/AgCl in Naacetate
buffer (pH 4.5; 50 mM). Additionally, Kapp
m (20.23 mM), Imax (3.03 mA) and sensitivity values were determined. Finally, the biosensor was successfully applied to glucose analysis
in various beverages and the results were compared with data obtained from the spectrophotometric
glucose detection kit as a reference method.
Langmuir, 2015
A robust drug delivery system based on nano-sized amphiphilic star-hyperbranched block copolymer,... more A robust drug delivery system based on nano-sized amphiphilic star-hyperbranched block copolymer, namely poly(methyl methacrylate-block-poly(hydroxylethyl methacrylate) (PMMA-b-PHEMA) is described. PMMA-b-PHEMA was prepared by sequential visible light induced self-condensing vinyl polymerization (SCVP) and conventional vinyl polymerization. All of the synthesis and characterization details of the conjugates are reported. To accomplish tumor cell targeting property, initially cell-targeting (Arginylglycylaspactic acid; RGD) and penetrating peptides (Cys-TAT) were binding to each other via the well-known EDC/NHS chemistry. Then, the resulted peptide was further incorporated to the surface of the amphiphilic hyperbranched copolymer via a coupling reaction between the thiol (-SH) group of the peptide and the hydroxyl group of copolymer by using N-(p-Maleinimidophenyl) isocyanate as a heterolinker. The drug release property and targeting effect of the anticancer drug (Doxorobucin; DOX) loaded nanostructures to two different cell lines were evaluated in vitro. U87 and MCF-7 were chosen as integrin αvβ3 receptor positive and negative cells for the comparison of the targeting efficiency, respectively. The data showed that drug-loaded copolymers exhibited enhanced cell inhibition towards U87 cells in compared to MCF-7 cells because targeting increased the cytotoxicity of drug-loaded copolymers against integrin αvβ3 receptor expressing tumor cells.
Sensors and Actuators B: Chemical, 2013
RSC Adv., 2014
Here we report the synthesis, characterization and application of calixarene (Calix) modified mon... more Here we report the synthesis, characterization and application of calixarene (Calix) modified montmorillonite (Mt) as a platform for bio-applications such as biomolecule immobilization and biosensing technologies. This modification enhanced the biomolecule immobilization capability of Mt.
Talanta, 2011
An electrochemical biosensor for detection of fructose in food samples was developed by immobiliz... more An electrochemical biosensor for detection of fructose in food samples was developed by immobilization of fructose dehydrogenase (FDH) on cysteamine and poly(amidoamine) dendrimers (PAMAM)-modified gold electrode surface. Electrochemical analysis was carried out by using hexacyanoferrate (HCF) as a mediator and the response time was 35s at +300 mV vs. Ag/AgCl. Moreover, some parameters such as pH, enzyme loading and type of PAMAM (Generations 2, 3 and 4) were investigated. Then, the FDH biosensor was calibrated for fructose in the concentration range of 0.25-5.0mM. To evaluate its utility, the FDH biosensor was applied for fructose analysis in real samples. Finally, obtained data were compared with those measured with HPLC as a reference method.
Sensors and Actuators B: Chemical, 2014
Microchimica Acta, 2011
We describe a microbial sensor based on Pseudomonas fluorescens cells that was prepared by modify... more We describe a microbial sensor based on Pseudomonas fluorescens cells that was prepared by modifying graphite electrodes with chitosan and carbon nanotubes. Chronoamperometry was performed at +0.3 V in the presence of hexacyanoferrate as a mediator and revealed a good response to glucose which is linear in the 1.0 to 5.0 mM concentration range. Linearity was defined by the equation of y=102.120x−13.279 (R 2 =0.998) (y shows current density as nA.cm −2 and x shows glucose concentration in mM). The effect of the CNTs on the response was compared to that of electrodes made without CNTs.
Materials Science and Engineering: C, 2011
A series of well-defined amphiphilic graft copolymers with hydrophobic polysulfone (PSU) as backb... more A series of well-defined amphiphilic graft copolymers with hydrophobic polysulfone (PSU) as backbones and hydrophilic poly(ethylene glycol) (PEG) as side chains were synthesized and characterized. For this purpose, PSUs were converted to azido-functionalized polymers ...
Materials Science and Engineering: C, 2013
An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated b... more An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated by construction of gold nanoparticles (AuNPs) on the surface of polyamidoamine dendrimer (PAMAM) modified gold electrode. Glucose oxidase (GOx) was used as a model enzyme and was immobilized onto the gold surface forming a self assembled monolayer via FcSH and cysteamine. Cyclic voltammetry and amperometry were used for the characterization of electrochemical response towards glucose substrate. Following the optimization of medium pH, enzyme loading, AuNP and FcSH amount, the linear range for the glucose was studied and found as 1.0 to 5.0 mM with the detection limit (LOD) of 0.6 mM according to S/N=3. Finally, the proposed Au/AuNP/(FcSH+Cyst)/PAMAM/GOx biosensor was successfully applied for the glucose analysis in beverages, and the results were compared with those obtained by HPLC.
Journal of Polymer Science Part A: Polymer Chemistry, 2011
Journal of Materials Chemistry, 2012
Herein, the phase-transfer reaction of quantum dots (QDs) with amine-terminated polyamidoamine (P... more Herein, the phase-transfer reaction of quantum dots (QDs) with amine-terminated polyamidoamine (PAMAM) dendrimers with controllable ligand molar ratios was achieved. The unique properties of PAMAM allowed us to build up structurally and electrostatically stabilized water soluble QD complexes. Synthesized conjugates were characterized in terms of fluorescence and UV-Vis profiles, hydrodynamic size, number of surface dendrimer groups, and stability. Cytotoxic effects of conjugates for MCF-7, A-549 and HEP-G2 cancer cells were assessed based on cell viability using MTT assay. Cytotoxicity results were expressed as no observable adverse effect concentration (NOAEC), 50% inhibitory concentration (IC 50 ) and total lethal concentration (TLC) values (mM). Furthermore, HER2 receptor-mediated targeting efficiency of antibody labelled P/QDs conjugates was evaluated by successful staining of MCF-7 cells with bioconjugates. Uniquely, effective cell internalization was achieved with well-characterized antibody coupled P/QDs in contrast to antibody free P/QDs conjugates. Fluorescence microscopy images demonstrated that the designed PAMAM-derivatized QDs nanoparticles show great potential in the areas of cellular imaging and targeted therapy.
Journal of Macromolecular Science, Part A, 2011
Journal of Macromolecular Science, Part A, 2013
Accumulation of cholesterol in human blood can cause several health problems such as heart diseas... more Accumulation of cholesterol in human blood can cause several health problems such as heart disease, coronary artery disease, arteriosclerosis, hypertension, cerebral thrombosis, etc. Therefore, simple and fast cholesterol determination in blood is clinically important. In this study, two types of amperometric cholesterol biosensors were designed by physically entrapping cholesterol oxidase in conducting polymers; thiophene capped poly(ethyleneoxide)/polypyrrole (PEO-co-PPy) and 3-methylthienyl methacrylate-cop-vinyl benzyloxy poly(ethyleneoxide)/polypyrrole (CP-co-PPy). PEO-co-PPy and CP-co-PPy were synthesized electrochemically and cholesterol oxidase was immobilized by entrapment during electropolymerization. The amperometric responses of the enzyme electrodes were measured by monitoring oxidation current of H 2 O 2 at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for both entrapment supports. Km values were found as 1.47 and 5.16 mM for PEO-co-PPy and CP-co-PPy enzyme electrodes, respectively. By using these Km values, it can be observed that ChOx immobilized in PEO-co-PPy shows higher affinity towards the substrate.
Food Chemistry, 2011
Gold nanoparticle (AuNP) modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)b... more Gold nanoparticle (AuNP) modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH 2 ) was used as the biosensing platform for glucose analysis. Electrochemical measurements were carried out by following the consumed oxygen due to the enzymatic reaction of glucose oxidase (GOx) at À0.7 V vs Ag/AgCl. Optimisation of pH, enzyme loading, stability experiments were carried out. Effect of NP was investigated by monitoring the signal responses at different AuNP sizes and amounts. A linear relation of y = 1.597x + 0.264 (R 2 = 0.993) was found for glucose concentrations between 0.002 and 5.0 mM. The analytical characteristics of the system were also evaluated for glucose determination in flow injection analysis (FIA) mode. Finally, the system was checked for glucose detection on real samples.
Food Analytical Methods, 2012
An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) in... more An inhibition based biosensing system was developed for the caffeic acid as lipoxygenase (LOX) inhibitor. LOX was immobilized in carbon paste electrode and the amperometric detection of hydroperoxy linoleic acid due to the enzymatic reaction using linoleic acid as a substrate was monitored at +0.9 V versus Ag/AgCl. The decrease in biosensor response in the presence of caffeic acid was found to be correlated with the inhibitor concentration. Diode array detector and LOX biosensor was used as an electrochemical detector for the analysis of this compound. All data were given as a comparison of two systems.
Food Analytical Methods, 2012
... Chim Acta 572:248252 Jia J, Tang M, Chen X, Qi L, Dong S (2003) Biosens Bioelectron 18:1023... more ... Chim Acta 572:248252 Jia J, Tang M, Chen X, Qi L, Dong S (2003) Biosens Bioelectron 18:10231029 Kara S, Keskinler ... AN (2001) Biosens Bioelectron 16:10011007 Mulchandani P, Chen W, Mulchandani A (2006) Anal Chim Acta 568:217221 Odaci D, Timur S, Telefoncu ...
Dyes and Pigments, 2011
Optical glucose oxidase (GOx) arrays based on pH sensitive fluorescent dye (2-(4-tolyl)-4-[4-(1,4... more Optical glucose oxidase (GOx) arrays based on pH sensitive fluorescent dye (2-(4-tolyl)-4-[4-(1,4,7,10tetraoxa-13-azacyclopentadecyl)benzylidene]-5-oxazolone) (CPO) has been constructed. The arrays were prepared by spotting of CPO and GOx together with tetraethoxysilane (TEOS)/Chitosan (CHIT) mixture via a microarrayer. After optimization studies, analytical characterization of enzyme arrays were carried out. The fluorescence intensity of the system was linearly correlated to glucose concentration in the range of 1.0e30.0 mM (in potassium phosphate buffer; 2.5 mM at pH 7.0). Furthermore, the developed arrays were used to analyze glucose in some beverages and HPLC was used as a reference method for independent glucose analysis.
Colloids and Surfaces B: Biointerfaces, 2014
We describe here the synthesis, characterization, bioconjugation, and application of water-solubl... more We describe here the synthesis, characterization, bioconjugation, and application of water-soluble thioglycolic acid TGA-capped CdTe/CdS quantum dots (TGA-QDs) for targeted cellular imaging. Antihuman epidermal growth factor receptor 2 (HER2) antibodies were conjugated to TGA-QDs to target HER2-overexpressing cancer cells. TGA-QDs and TGA-QDs/anti-HER2 bioconjugates were characterized by fluorescence and UV-Vis spectroscopy, X-ray diffraction (XRD), hydrodynamic sizing, electron microscopy, and gel electrophoresis. TGA-QDs and TGA-QDs/anti-HER2 were incubated with cells to examine cytotoxicity, targeting efficiency, and cellular localization. The cytotoxicity of particles was measured using an MTT assay and the no observable adverse effect concentration (NOAEC), 50% inhibitory concentration (IC 50 ), and total lethal concentration (TLC) were calculated. To evaluate localization and targeting efficiency of TGA-QDs with or without antibodies, fluorescence microscopy and flow cytometry were performed. Our results indicate that antibody-conjugated TGA-QDs are well-suited for targeted cellular imaging studies.