| 1. |
- Karimian, Najmeh, et al.
(författare)
-
An ultrasensitive molecularly-imprinted human cardiac troponin sensor
- 2013
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 50, s. 492-498
-
Tidskriftsartikel (refereegranskat)abstract
- Cardiac troponin T (TnT) is a highly sensitive cardiac biomarker for myocardial infarction. In this study, the fabrication and characterisation of a novel sensor for human TnT based on a molecularly-imprinted electrosynthesised polymer is reported. A TnT sensitive layer was prepared by electropolymerisation of o-phenylenediamine (o-PD) on a gold electrode in the presence of TnT as a template. To develop the molecularly imprinted polymer (MIP), the template molecules were removed from the modified electrode surface by washing with alkaline ethanol. Electrochemical methods were used to monitor the processes of electropolymerisation, template removal and binding. The imprinted layer was characterised by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). The incubation of the MIP-modified electrode with respect to TnT concentration resulted in a suppression of the ferro/ferricyanide redox process. Experimental conditions were optimised and a linear relationship was observed between the peak current of [Fe(CN)(6)](3-)/[Fe (CN)(6)](4-) and the concentration of TnT in buffer over the range 0.009-0.8 ng/mL, with a detection limit of 9 pg/mL. The TnT MIP sensor was shown to have a high affinity to TnT in comparison with nonimprinted polymer (NIP) electrodes in both buffer and blood serum.
|
|
| 2. |
- Naseer, Rashda, et al.
(författare)
-
Redox, surface and electrocatalytic properties of layer-by-layer films based upon Fe(III)-substituted crown polyoxometalate [P8W48O184Fe16(OH)(28)(H2O)(4)](20-)
- 2014
-
Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 134, s. 450-458
-
Tidskriftsartikel (refereegranskat)abstract
- The electrocatalytic ability of the iron-substituted crown-type polyoxometalate (POM) Li4K16[P8W48O184Fe16(OH)(28)(H2O)(4)]center dot 66H(2)O center dot 2KCl (P8W48Fe16) towards the reduction of both nitrite and hydrogen peroxide reduction has been studied in both the solution and immobilized states for the POM. P8W48Fe16 was surface immobilised onto carbon electrode surfaces through employment of the layer-by-layer technique (LBL) using pentaerythritol-based Ru(II)-metallodendrimer [RuD](PF6)(8) as the cationic layer within the resulting films. The constructed multilayer films have been extensively studied by various electrochemical techniques and surface based techniques. Cyclic voltammetry and impedance spectroscopy have been utilized to monitor the construction of the LBL film after the deposition of each monolayer. The electrochemical behaviour of both a cationic and anionic redox probes at the LBL films has been undertaken to give indications as to the films porosity. The elemental composition and the surface morphology of the LBL films was conifmrde through the employment of AFM, XPS and SEM.
|
|
| 3. |
- Sekretaryova, Alina, et al.
(författare)
-
A highly sensitive and self-powered cholesterol biosensor
- 2014
-
Ingår i: 24<sup>th </sup>Anniversary World Congress on Biosensors – Biosensors 2014. - : Elsevier.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Blood cholesterol is a very important parameter for the assessment of atherosclerosis and other lipid disorders. The total cholesterol concentration in human blood should be less than 5.17 mM. Concentrations in the range 5.17 – 6.18 mM are considered borderline high risk and levels above 6.21 mM, high risk. Cholesterol determination with high accuracy is therefore necessary in order to differentiate these levels for medical screening or diagnosis. Several attempts to develop highly sensitive cholesterol biosensors have been described, but, to the best of our knowledge, this is the first report of a self-powered cholesterol biosensor, i.e. a device delivering the analytical information from the current output of the energy of the biocatalytic conversion of cholesterol, without any external power source. This is particularly relevant to the development of inexpensive screening devices based on printed electronics. We present two complementary bioelectrocatalytic platforms suitable for the fabrication of a self-powered biosensor. Both are based on cholesterol oxidase (ChOx) immobilisation in a sol-gel matrix, as illustrated in Fig. 1 [1]. Mediated biocatalytic cholesterol oxidation [2] was used as the anodic reaction and electrocatalytic reduction of hydrogen peroxide on Prussian Blue (PB) as the cathodic reaction. Due to a synergistic effect in the self-powered cholesterol biosensor, the analytical parameters of the overall device exceeded those of the individual component half-cells, yielding a sensitivity of 0.19 A M-1 cm-2 and a dynamic range that embraces the free cholesterol concentrations found in human blood. Thus, we have demonstrated the novel concept of highly sensitive cholesterol determination using the first self-powered cholesterol biosensor. This configuration is particularly promising for incorporation in emerging plastic- and paper-based analytical instruments for decentralised diagnostics and mobile health.
|
|
| 4. |
- Sekretaryova, Alina, et al.
(författare)
-
Cholesterol Self-Powered Biosensor
- 2014
-
Ingår i: Analytical Chemistry. - : American Chemical Society. - 0003-2700 .- 1520-6882. ; 86:19, s. 9540-9547
-
Tidskriftsartikel (refereegranskat)abstract
- Monitoring the cholesterol level is of great importance, especially for people with high risk of developing heart disease. Here we report on reagentless cholesterol detection in human plasma with a novel single-enzyme, membrane-free, self-powered biosensor, in which both cathodic and anodic bioelectrocatalytic reactions are powered by the same substrate. Cholesterol oxidase was immobilized in a sol-gel matrix on both the cathode and the anode. Hydrogen peroxide, a product of the enzymatic conversion of cholesterol, was electrocatalytically reduced, by the use of Prussian blue, at the cathode. In parallel, cholesterol oxidation catalyzed by mediated cholesterol oxidase occurred at the anode. The analytical performance was assessed for both electrode systems separately. The combination of the two electrodes, formed on high surface-area carbon cloth electrodes, resulted in a self-powered biosensor with enhanced sensitivity (26.0 mA M-1 cm(-2)), compared to either of the two individual electrodes, and a dynamic range up to 4.1 mM cholesterol. Reagentless cholesterol detection with both electrochemical systems and with the self-powered biosensor was performed and the results were compared with the standard method of colorimetric cholesterol quantification.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Sekretaryova, Alina, 1989-
(författare)
-
Novel reagentless electrodes for biosensing
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Analytical chemical information is needed in all areas of human activity including health care, pharmacology, food control and environmental chemistry. Today one of the main challenges in analytical chemistry is the development of methods to perform accurate and sensitive rapid analysis and monitoring of analytes in ‘real’ samples. Electrochemical biosensors are ideally suited for these applications.Despite the wide application of electrochemical biosensors, they have some limitations. Thus, there is a demand on improvement of biosensor performance together with a necessity of simplification required for their mass production. In this thesis the work is focused on the development of electrochemical sensors with improved performance applicable for mass production, e.g. by screen printing.Biosensors using immobilized oxidases as the bio-recognition element are among the most widely used electrochemical devices. Electrical communication between redox enzymes and electrodes can be established by using natural or synthetic electron carriers as mediators. However, sensors based on soluble electronshuttling redox couples have low operational stability due to the leakage of water-soluble mediators to the solution. We have found a new hydrophobic mediator for oxidases – unsubstituted phenothiazine. Phenothiazine and glucose oxidase, lactate oxidase or cholesterol oxidase were successfully co-immobilized in a sol-gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively. All elaborated biosensors with phenothiazine as a mediator exhibited long-term operational stability. A kinetic study of the mediator has shown that phenothiazine is able to function as an efficient mediator in oxidase-based biosensors.To improve sensitivity of the biosensors and simplify their production we have developed a simple approach for production of graphite microelectrode arrays. Arrays of microband electrodes were produced by screen printing followed by scissor cutting, which enabled the realization of microband arrays at the cut edge. The analytical performance of the system is illustrated by the detection of ascorbic acid through direct oxidation and by detection of glucose using a phenothiazine mediated glucose biosensor. Both systems showed enhanced sensitivity due to improved mass transport. Moreover, the developed approach can be adapted to automated electrode recovery.Finally, two enzyme-based electrocatalytic systems with oxidation and reduction responses, respectively, have been combined into a fuel cell generating a current as an analytical output (a so-called self-powered biosensor). This was possible as a result of the development of the phenothiazine mediated enzyme electrodes, which enabled the construction of a cholesterol biosensor with self-powered configuration. The biosensor generates a current when analyte (cholesterol) is added to the cell. The biosensor has been applied for whole plasma analysis.All developed concepts in the thesis are compatible with a wide range of applications and some of them may even be possible to realize in a fully integrated biosensor unit based on printed electronics.
|
|
| 8. |
- Sekretaryova, Alina, et al.
(författare)
-
Unsubstituted phenothiazine as a superior water-insoluble mediator for oxidases
- 2014
-
Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 53, s. 275-282
-
Tidskriftsartikel (refereegranskat)abstract
- The mediation of oxidases glucose oxidase (GOx), lactate oxidase (LOx) and cholesterol oxidase (ChOx) by a new electron shuttling mediator, unsubstituted phenothiazine (PTZ), was studied. Cyclic voltammetry and rotating-disk electrode measurements in nonaqueous media were used to determine the diffusion characteristics of the mediator and the kinetics of its reaction with GOx, giving a second-order rate constant of 7.6×103–2.1×104 M−1 s−1 for water–acetonitrile solutions containing 5–15% water. These values are in the range reported for commonly used azine-type mediators, indicating that PTZ is able to function as an efficient mediator. PTZ and GOx, LOx and ChOx were successfully co-immobilised in sol–gel membrane on a screen-printed electrode to construct glucose, lactate and cholesterol biosensors, respectively, which were then optimised in terms of stability and sensitivity. The electrocatalytic oxidation responses showed a dependence on substrate concentration ranging from 0.6 to 32 mM for glucose, from 19 to 565 mM for lactate and from 0.015 to 1.0 mM for cholesterol detection. Oxidation of substrates on the surface of electrodes modified with PTZ and enzyme membrane was investigated with double-step chronoamperometry and the results showed that the PTZ displays excellent electrochemical catalytic activities even when immobilised on the surface of the electrode.
|
|
| 9. |
- Sekretaryova, Alina, et al.
(författare)
-
Unsubstitutedand insoluble phenothiazine as an electron-transfer mediator in enzymaticelectrochemical biosensors
- 2013
-
Ingår i: <em>Nano-scaled arrangements of proteins, aptamers, andother nucleic acid structures – and their potential applications</em> , COST Thematic Workshop, 8-9 October 2013, Helmholtz Zentrum fürUmweltforschung, Leipzig, Germany. - Leipzig : Helmholtz Zentrum für Umweltforschung. ; , s. O1-
-
Konferensbidrag (refereegranskat)
|
|
| 10. |
|
|
