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The use of templates to assist and possess a control over the synthesis of nanomaterials has been an attractive option to achieve this goal. Here we have used sodium dodecyl sulfate (SDS) to act as a template for the low temperature synthesis of cobalt oxide (Co3O4) nanostructures. The use of SDS has led to tune the morphology, and the product was in the form of "cotton-like" nanostructures instead of connected nanowires. Moreover, the variation of the amount of the SDS used was found to affect the charge transfer process in the Co3O4. Using Co3O4 synthesized using the SDS for sensing of cholesterol was investigated. The use of the Co3O4 synthesized using the SDS was found to yield an improved cholesterol biosensor compared to Co3O4 synthesized without the SDS. The improvement of the cholesterol sensing properties upon using the SDS as a template was manifested in increasing the sensitivity and the dynamic range of detection. The results achieved in this study indicate the potential of using template assisted synthesis of nanomaterials in improving some properties, e. g., cholesterol sensing.

WOS: 000379755400003, This study reports the fabrication of an amperometric cholesterol biosensor based on cholesterol oxidase (ChOx), SnO(2)NPs and Nafion-modified carbon paste enzyme electrodes (CPE/SnO(2)NPs-ChOx/Naf). The electrochemical characterisations of BCPE and CPE/SnO(2)NPs were performed using CV and EIS. The determination of cholesterol was carried out by electrochemical oxidation of H2O2 at 0.6 V vs. Ag/AgCl. The CPE/SnO(2)NPs-ChOx/Naf presented a linear range from 0.20 mu mol L-1 to 4.95 mu mol L-1 with a low limit of detection (0.04 mu mol L-1). In addition, the optimal values for pH and temperature were found to be 7.5 and 35 degrees C, respectively. The CPE/SnO(2)NPs-ChOx/Naf was used for the determination of cholesterol in serum samples and good results were obtained. (C) 2016 Institute of Chemistry, Slovak Academy of Sciences, Ankara University Research Fund (BAP)Ankara University, The authors wish to thank the Ankara University Research Fund (BAP) for the financial support received.

Cholesterol biosensor was fabricated by co-immobilizing cholesterol esterase and cholesterol oxidase in polyvinyl formal membrane and by mounting over the sensing part of oxygen electrode. The immobilized enzymes membrane was characterized by atomic force microscopy. The biosensor showed the linearity for 100-450 mg dl-1 cholesterol acetate. The minimum detection limit of the cholesterol was 50 mg dl-1. The effects of temperature, pH and the stability of immobilized enzymes were also studied. A good correlation was found among cholesterol values obtained by colorimetric, Enzo-kit and auto analyzer method. The shelf-life of the biosensor was more than three month at 4ºC and enzyme membrane can be re-used 20 times without any significant loss in enzyme activity.

A simple and robust cholesterol biosensor was designed by immobilizing cholesterol oxidase (ChOx) onto a conducting polymer modified graphite electrode. For this purpose, monomer, (Z)-4-(4-(9H-carbazol-9-yl) benzylidene) 2 (4 nitrophenyl) oxazol-5(4H)-one (CBNP), was synthesized and electrochemically polymerized on an electrode to achieve an effective immobilization platform for enzyme immobilization. After electropolymerization of the monomer (CBNP), electrochemical and spectroelectrochemical properties were investigated. Through the presence of nitro group on the polymer backbone hydrogen-bonding between enzyme molecules and polymer was achieved. Moreover, strong pi-pi stacking between aromatic moities in the polymer and aromatic residues of the enzyme enables a sensitive and reliable biosensor by conserving the crucial structure of biological molecules during the enzymatic reaction. The efficient interaction of the enzyme with the polymer coated surface brings easy and long-life detection of the substrate, cholesterol. After successful immobilization of ChOx with the help of glutaraldehyde as the crosslinking agent, amperometric biosensor responses were recorded at -0.7 V vs Ag wire in phosphate buffer (pH 7.0). K-M(app) (37.3 mu M), I-max (3.92 mu A), LOD (0.4063 mu M) and sensitivity (1.49 pA mu M-1 cm(-2)) values were determined. Finally, the prepared biosensor was successfully applied for determination of cholesterol content in real blood samples. (C) 2015 Elsevier B.V. All rights reserved.

Cholesterol determination in body is important in diagnosis of diseases like coronary heart disease, arteriosclerosis, diabetes, and obstructive jaundice. This research aims at developing fluorimetric cholesterol biosensors based on self-assembled mesoporous alginate-silica (Algilica) microspheres. For preparing the biosensor, Pt-(II)-octaethylporphine (PtOEP; oxygen sensitive metalloporphyrin) dye has been loaded in the Algilica microspheres using the solvent-mediated precipitation method. Cholesterol oxidase (ChOx) was then covalently conjugated to PtOEP/Algilica microspheres using EDC and NHS reagents. PtOEP dye and enzyme encapsulation, activity and stability were then analyzed. Layer-by-layer self-assembly was finally performed using PAH and PSS polyelectrolytes to minimize leaching of the biosensor components. The prepared biosensor exhibited linearity over a range of 0.77-2.5mM O(2) (KSV: 0.097/mM of O(2)) obtained using from Stern-Volmer plots. The biosensor response to standard cholesterol displayed a linear analytical range from 1.25 to 10mM of cholesterol with regression coefficient of 0.996 (1.25-3.75 mM), 0.976 (1.25-6 mM), and 0.959 (1.25-10mM) and response time of 10 min. Thus, the prepared cholesterol biosensor shows great potential in the diagnosis of hypercholesterolemia. Biotechnol. Bioeng. 2011; 108: 2011-2021. (C) 2011 Wiley Periodicals, Inc.

Background & objectives: The use of epoxy resin membrane as a support for immobilization of enzyme has resulted into improved sensitivity and stability of biosensors for uric acid, ascorbic acid and polyphenols. The present work was aimed to prepare an improved amperometric biosensor for determination of serum cholesterol required in the diagnostics and management of certain pathological conditions. Methods: Epoxy resin membrane with immobilized cholesterol oxidase was mounted on the cleaned platinum (Pt) electrode with a parafilm to construct a working electrode. This working electrode along with Ag/AgCl as reference and Ag wire as an auxiliary electrode were connected through a three terminal electrometer to construct a cholesterol biosensor. Results: The sensor showed optimum response within 25 sec at pH 7.0 and 45°C. The linear working range of biosensor was 1.0 to 8.0 mM cholesterol. Km and Imax for cholesterol were 5.0 mM and 9.09 μA, respectively. The biosensor measured serum cholesterol. The minimum detection limit of the sensor was 1.0 mM. The mean analytical recoveries of added cholesterol in serum (2.84 and 4.13 mM) were 91.4±2.8 and 92.3±3.1 per cent (n=6), respectively. Within and between assay coefficient of variation (CV) were