Saniye Soylemez

Synthesis and characterization of conducting polymers containing polypeptide and ferrocene side chains as ethanol biosensors

A novel approach for the fabrication of a biosensor from a conducting polymer bearing polypeptide segments and ferrocene moieties is reported. The approach involves the electrochemical copolymerization of the electroactive polypeptide macromonomer and independently prepared ferrocene imidazole derivative of dithiophene, on the electrode surface. The polypeptide macromonomer was synthesized by the simultaneous formation of N-carboxyanhydride (NCA) and ring opening polymerization of N-Boc-L-lysine (α-amino acid of the corresponding NCA) using an amino functional bis-EDOT derivative (BEDOA-6) as an initiator. Alcohol oxidase was then covalently immobilized onto the copolymer coated electrode using glutaraldehyde as the crosslinking agent. The intermediates and final conducting copolymer before and after enzyme immobilization were fully characterized by FT-IR, 1H-NMR, GPC, cyclic voltammetry, SEM and EIS analyses. The newly designed biosensor which combined the advantages of each component was tested as an ethanol sensing system offering fast response time (9 s), wide linear range (0.17 mM and 4.25 mM) and low detection limit (0.28 mM) with a high sensitivity (12.52 μA mM−1 cm−2). Kinetic parameters KappM and Imax were 2.67 mM and 2.98 μA, respectively. The capability of the biosensor in determining ethanol content in alcoholic beverages was also demonstrated.

A Novel Acetylcholinesterase Biosensor: Core–Shell Magnetic Nanoparticles Incorporating a Conjugated Polymer for the Detection of Organophosphorus Pesticides

To construct a sensing interface, in the present work, a conjugated polymer and core-shell magnetic nanoparticle containing biosensor was constructed for the pesticide analysis. The monomer 4,7-di(furan-2-yl)benzo[c][1,2,5]thiadiazole (FBThF) and core-shell magnetic nanoparticles were designed and synthesized for fabrication of the biosensing device. The magnetic nanoparticles were first treated with silica and then modified using carboxyl groups, which enabled binding of the biomolecules covalently. For the construction of the proposed sensor a two-step procedure was performed. First, the poly(FBThF) was electrochemically generated on the electrode surface. Then, carboxyl group modified magnetic nanoparticles (f-MNPs) and acetylcholinesterase (AChE), the model enzyme, were co-immobilized on the polymer-coated surface. Thereby, a robust and novel surface, conjugated polymer bearing magnetic nanoparticles with pendant carboxyl groups, was constructed, which was characterized using Fourier transform infrared spectrometer, cyclic voltammetry, scanning electron microscopy, and contact angle measurements. This novel architecture was then applied as an immobilization platform to detect pesticides. To the best of our knowledge, a sensor design that combines both conjugated polymer and magnetic nanoparticles was attempted for the first time, and this approach resulted in improved biosensor characteristics. Hence, this approach opens a new perspective in the field of enzyme immobilization and sensing applications. Paraoxon and trichlorfon were selected as the model toxicants. To obtain best biosensor performance, optimization studies were performed. Under optimized conditions, the biosensor in concern revealed a rapid response (5 s), a low detection limit (6.66 × 10(-3) mM), and high sensitivity (45.01 μA mM(-1) cm(-2)). The KM(app) value of poly(FBThF)/f-MNPs/AChE were determined as 0.73 mM. Furthermore, there was no considerable activity loss for 10 d for poly(FBThF)/f-MNPs/AChE biofilm.

Development of a novel biosensor based on a conducting polymer.

A new type of amperometric cholesterol biosensor was fabricated to improve the biosensor characteristics such as sensitivity and reliability. For this purpose, a novel immobilization matrix 2-(4-fluorophenyl)-4,7-di(thiophene-2-yl)-1H-benzo[d]imidazole (BIPF) was electrochemically deposited on a graphite electrode and used as a matrix for the immobilization of cholesterol oxidase (ChOx). Due to strong π-π stacking of aromatic groups in the structures of polymer backbone and enzyme molecule, one can easily achieve a sensitive and reliable biosensor without using any membrane or covalent bond formation between the enzyme molecules and polymer surface. Moreover, through pendant fluorine group of the polymer, H-bond formation between with enzyme molecules and polymer was generated. Cholesterol was used as the substrate and amperometric response was measured in correlation with cholesterol amount, at -0.7 V vs. Ag/AgCl in phosphate buffer (pH 7.0). Consequently, optimum conditions for this constructed biosensor were determined. K(M)app, I(max), LOD and sensitivity values were investigated and calculated as 4.0 nM, 2.27 µA, 0.404 µM and 1.47 mA/mM cm(2), respectively. A novel and accurate cholesterol biosensor was developed for the determination of total cholesterol in food samples.

Development of an efficient immobilization matrix based on a conducting polymer and functionalized multiwall carbon nanotubes: synthesis and its application to ethanol biosensors

Material modification is one of the hot topics recently. Hereby a novel functional monomer, 2-(4-nitrophenyl)-4,7-di(thiophen-2-yl)-1H-benzo[d]imidazole (BIPN), was synthesized for matrix generation through electrochemical polymerization. Its conducting polymer was successfully used for the biolayer construction in the biosensor preparation. The electrochemical and morphological properties were improved by the introduction of carboxylic acid functionalized multiwall carbon nanotubes (f-MWCNTs). Carboxylic acid functionalization of MWCNTs was carried out via acid treatment. The electrode surface was modified with the polymer and f-MWCNTs during electropolymerization to achieve a perfect immobilization matrix for alcohol oxidase. In order to prepare a new alcohol biosensor, alcohol oxidase (AOx) was immobilized onto the modified electrode. The modified electrode was characterized by scanning electron microscopy (SEM), X-ray photoelectron microscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy techniques. Electrochemical responses of the enzyme electrodes were monitored at -0.7 V vs. Ag reference electrode by monitoring oxygen consumption in the presence of ethanol. Kinetic parameters, operational and storage stabilities were investigated. K, Imax, LOD and sensitivity were calculated as 16.946 mM, 3.31 μA, 0.806 mM and 476 μA mM-1 cm-2, respectively. Finally, this biosensor was applied to estimate the alcohol content in various beverages successfully.

A Novel and Effective Surface Design: Conducting Polymer/β-Cyclodextrin Host–Guest System for Cholesterol Biosensor

The combination of supramolecules and conducting polymers (CPs) has gained much attention for the development of new immobilization matrices for biomolecules. Herein, an amperometric biosensor based on a novel conducting polymer, poly(2-(2-octyldodecyl)-4,7-di(selenoph-2-yl)-2H-benzo[d][1,2,3]triazole)) (PSBTz) and β-cyclodextrin (β-CD) for the detection of cholesterol, was constructed. The PSBTz film with β-CD was deposited on a graphite electrode by electropolymerization technique to achieve a suitable matrix for enzyme immobilization. Moreover, to justify the immobilization, alkyl chain containing conducting polymer (PSBTz) was designed, synthesized and electrochemically polymerized on the transducer surface. Alkyl chains in the structure of SBTz and hydroxyl groups of β-CD contributed to effective immobilization while protecting the suitable orientation of the biomolecule. Cholesterol oxidase (ChOx) was covalently immobilized onto the modified surface using N,N′-carbonyldiimidazole (CDI) as the cross-linking agent. After successful immobilization, amperometric biosensor responses were recorded at −0.7 V vs Ag/AgCl in phosphate buffer (pH 7.0). The apparent Michaelis-Menten constant (KM(app)), maximum current (Imax), limit of detection (LOD), and sensitivity values were determined: 28.9 μM, 12.1 μA, 0.005 μM, and 5.77 μA/μM cm(2), respectively. The fabricated biosensor was characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. Finally, the prepared biosensor was successfully applied for the determination of cholesterol in blood samples.

Selenium containing conducting polymer based pyranose oxidase biosensor for glucose detection.

A novel amperometric pyranose oxidase (PyOx) biosensor based on a selenium containing conducting polymer has been developed for the glucose detection. For this purpose, a conducting polymer; poly(4,7-bis(thieno[3,2-b]thiophen-2-yl)benzo[c][1,2,5] selenadiazole) (poly(BSeTT)) was synthesized via electropolymerisation on gold electrode to examine its matrix property for glucose detection. For this purpose, PyOx was used as the model enzyme and immobilised via physical adsorption technique. Amperometric detection of consumed oxygen was monitored at -0.7 V vs Ag reference electrode in a phosphate buffer (50 mM, pH 7.0). K(M)(app), Imax, LOD and sensitivity were calculated as 0.229 mM, 42.37 nA, 3.3 × 10(-4)nM and 6.4 nA/mM cm(2), respectively. Scanning electron microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS) and cyclic voltammetry (CV) techniques were used to monitor changes in surface morphologies and to run electrochemical characterisations. Finally, the constructed biosensor was applied for the determination of glucose in beverages successfully.

A novel architecture based on a conducting polymer and calixarene derivative: its synthesis and biosensor construction

In this study, a novel amperometric glucose biosensor based on a selenium comprising conducting polymer and calixarene was developed. Firstly, poly(2-(2-octyldodecyl)-4,7-di(selenoph-2-yl)-2H-benzo[d][1,2,3]triazole), poly((SBTz)) was electrodeposited onto a graphite electrode by an electropolymerization technique. Then, a newly synthesized calixarene and gold nanoparticle (AuNP) mixture was used for the improvement of biosensor characteristics. GOx, as a model enzyme was immobilized on the modified electrode surface. The constructed surface serves as a sufficient immobilization platform for the detection of glucose. Calixarenes and their derivatives may be a favouring agent for enzyme immobilization due to their specific configurations. Moreover, through the covalent binding between the carboxylic groups of the calixarenes and amino groups of the biomolecule, effective enzyme immobilization can be achieved while protecting the well-ordered structure of the enzyme molecule. Amperometric detection was carried out following oxygen consumption at −0.7 V vs. the Ag reference electrode in phosphate buffer (50 mM, pH 6.5). The proposed biosensor showed a linear amperometric response for glucose within a concentration range of 0.005 to 0.5 mM (LOD: 0.004 mM). Kappm and sensitivity were calculated as 0.025 mM and 102 μA mM−1 cm−2, respectively. Scanning Electron Microscopy (SEM) was used to investigate the surface morphologies of successive modifications. Finally, the constructed biosensor was tested successfully to detect glucose in beverage samples.

A sepiolite modified conducting polymer based biosensor.

A conducting polymer modified with sepiolite was utilized in the construction of a highly sensitive and fast amperometric cholesterol biosensor. In this study a monomer; (10,13-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)dibenzo[a,c]phenazine (PHED)) was synthesized and then its polymer was coated on a graphite electrode by electropolymerization to obtain a matrix for enzyme immobilization. Cholesterol oxidase was immobilized onto polymer coated electrode by adsorption technique. Sepiolite was introduced for a successful immobilization of the cholesterol oxidase. Immobilized enzyme kinetic parameters (KM(app), Imax) were evaluated by Michaelis-Menten kinetics and calculated as 0.031 mM and 6.06 μA, respectively. LOD and sensitivity were estimated as 0.36 μM and 1.64 mA/mMcm(2). Characterization of designed biosensor was done to examine the effect of various factors such as enzyme amount, optimum pH and shelf-life. A novel accurate and inexpensive cholesterol biosensor was developed for the determination of total cholesterol in food samples.

A novel approach for the fabrication of a flexible glucose biosensor: The combination of vertically aligned CNTs and a conjugated polymer.

A novel flexible glucose biosensor using vertically aligned carbon nanotubes (VACNT) and a conjugated polymer (CP) was fabricated. A scaffold based on VACNT grown on aluminum foil (VACNT-Al foil) with poly (9,9-di-(2-ethylhexyl)-fluorenyl-2,7-diyl)-end capped with 2,5-diphenyl-1,2,4-oxadiazole (PFLO) was used as the immobilization matrix for the glucose biosensor. Glucose oxidase (GOx) was immobilized on a modified indium tin oxide (ITO) coated polyethylene terephthalate (PET) electrode surface. The biosensor response at a potential of -0.7V versus Ag wire was followed by the decrease in oxygen level as a result of enzymatic reaction. The biosensor exhibited a linear range between 0.02mM and 0.5mM glucose and kinetic parameters (KMapp, Imax, limit of detection (LOD) and sensitivity) were estimated as 0.193mM, 8.170μA, 7.035×10-3mM and 65.816μA/mMcm2, respectively. Scanning electron microscopy (SEM) was used for surface characterization. The constructed biosensor was applied to determine the glucose content in several beverages.

Construction and amperometric biosensing performance of a novel platform containing carbon nanotubes-zinc phthalocyanine and a conducting polymer

A novel glucose oxidase (GOx) based amperometric biosensor utilizing a conducting polymer (CP), multi walled carbon nanotubes (MWCNTs) and a novel water soluble zinc phthalocyanine (ZnPc) was constructed. For this purpose, a novel ZnPc was synthesized to examine the role of being a part of support material for enzyme deposition. High water solubility was achieved with the introduction of tetra quaternized imidazolyl moieties at the peripheral positions of phthalocyanine. In order to fabricate the proposed biosensor, a graphite electrode was firstly modified with poly[9,9-di-(2-ethylhexyl)- fluorenyl-2,7-diyl] end capped with N,N-Bis(4- methylphenyl)-4-aniline (PFLA) and MWCNTs. Then, GOx was co-immobilized with ZnPc onto the modified surface. To the best our knowledge, a sensor design which combines conjugated polymer/MWCNTs/ZnPc was attempted for the first time and this approach resulted in improved biosensor characteristics. The constructed biosensor showed a linear response for glucose between 0.025-1.0mM with a detection limit of 0.018mM. KMapp and sensitivity values were calculated as 0.53mM and 82.18μAmm-1cm-2, respectively. Moreover, scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques were used to investigate the surface modifications. Finally, fabricated biosensor was tested on beverages for glucose detection successfully.