| 1. |
- Alpeeva, IS, et al.
(författare)
-
Bi-enzyme alcohol biosensors based on genetically engineered alcohol oxidase and different peroxidases
- 2005
-
Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 152:1-2, s. 21-27
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the development of a bi-layer bi-enzyme biosensor architecture using different peroxidases and alcohol oxidase from Hansenula polymorpha C-105 as biological recognition elements. The sensor architecture comprises a first layer containing either horseradish peroxidase or royal palm tree peroxidase crosslinked with an Osmium complex-modified redox hydrogel. On top, a second layer was formed by electrochemically induced precipitation of a cathodic electrodeposition paint simultaneously entrapping alcohol oxidase isolated from a genetically modified strain of Hansenula polymorpha C-105. The sensor architecture was optimized with respect to effective electron transfer and stability of the enzyme. The main characteristics of the biosensors are an apparent maximal current I-max(app) of 572-940 nA, an apparent Michaelis constant K-M(app) of 9.5 mM, a sensitivity of 60-98 nA mM(-1) and an improved operational stability represented by a deactivation constant of 1.5-2.0 x 10(-4) min(-1).
|
|
| 2. |
- Augustsson, Per, et al.
(författare)
-
Buffer medium exchange in continuous cell and particle streams using ultrasonic standing wave focusing
- 2009
-
Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 164:3-4, s. 269-277
-
Tidskriftsartikel (refereegranskat)abstract
- A microfluidic strategy to perform buffer exchange of particle and cell suspensions in a continuous flow format on, chip is presented. Ultrasonic standing wave technology is utilized to confine particulate matter to the centre of a buffer exchange channel while particle free buffer is sequentially aspirated via capillaries that branch off from the buffer exchange channel. At each such branch, clean buffer is supplied at an equal flow-rate from a capillary at the opposing channel wall, generating a sideways translation of the original buffer, laminated with a wash buffer stream. Each such junction increases the buffer exchange ratio accordingly. The reported buffer exchange system provides means to adjust buffer exchange conditions on-line by tuning the ratio of the cross-flow wash buffer relative the sample suspension flow, rate. The system performance was evaluated using 5 mu m polystyrene microbeads and a dye as the model contaminant. Wash efficiencies up to 96.4% were accomplished with a 0.2% solid content bead suspension, using eight cross-flow junctions, effectively exchanging the carrier buffer twice. The corresponding data for erythrocyte washing was recorded to be 98.3% at a haematocrit of 2%.
|
|
| 3. |
- Liu, Y, et al.
(författare)
-
Rapid fluorometric screening of antibiotics in seafood
- 2006
-
Ingår i: Microchimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 153:3-4, s. 133-137
-
Tidskriftsartikel (refereegranskat)abstract
- Simple and rapid fluorometric screening methods have been developed based on the competitive binding between the target and an intercalating fluorophore dye to double-stranded-DNA (dsDNA). In this study, the long-wavelength fluorescente dye TOTO-3 was employed as the indicator. Compounds that interact with dsDNA will affect the binding of TOTO-3 to the nucleic acid thereby changing the fluorescence intensity. The analyte concentration is indirectly determined by the decrease in fluorescence intensity. A fiber optic fluorescence screening system was developed for rapid and convenient sample processing. Lambda DNA (48.5kb) was chosen as a suitable sensing nucleic acid material. Detection of sulfathiazole and chloramphenicol in shrimps using this method was studied in the range of 0.5-25ng mL(-1) of sulfathiazole and of 1-50ng mL(-1) of chloramphenicol. Detection limits of 0.5ng mL(-1) of sulfathiazole and 1ng mL(-1) of chloramphenicol were achieved. This approach is useful as a routine test in the monitoring of antibiotics in the environment or aquaculture products. The easy operation and the rapid and sensitive detection make this a potential high-throughput screening method.
|
|
| 4. |
- Muresan, Laura, et al.
(författare)
-
Amine oxidase amperometric biosensor coupled to liquid chromatography for biogenic amines determination
- 2008
-
Ingår i: MICROCHIMICA ACTA. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 163:3-4, s. 219-225
-
Konferensbidrag (refereegranskat)abstract
- A selective and sensitive method is presented for biogenic amines (BA) determination. The novelty consists in coupling a highly selective electrochemical biosensor to a weak acid cation-exchange column for online detection of amines. A bienzyme design, based on a recently isolated amine oxidase from grass pea and commercial horseradish peroxidase, was used for the biosensor construction. The enzymes were co-immobilized on the surface of a graphite electrode together with the electrochemical mediator (Os-redox polymer). The electrochemical detection was performed at a low applied potential (-50 mV vs. Ag/AgCl, KCl0.1 M), where biases from interferences are minimal. The separation and determination of six BA, with relevance in food analysis (tyramine, putrescine, cadaverine, histamine, agmatine and spermidine), were investigated. Irrespective of the BA nature, the amine oxidase-based biosensor showed a linear response up to 5 mM, and its sensitivity decreases in the following order: cadaverine, putrescine, spermidine, agmatine, histamine and tyramine. The approach was used to estimate the BA content in fish samples, after their extraction with methanesulfonic acid.
|
|
| 5. |
- Winquist, Fredrik
(författare)
-
Voltammetric electronic tongues – basic principles and applications
- 2008
-
Ingår i: Microchimica Acta. - : Institutionen för fysik, kemi och biologi. - 0026-3672 .- 1436-5073. ; 163:1-2, s. 3-10
-
Tidskriftsartikel (refereegranskat)abstract
- This review examines basic principles and applications of voltammetric electronic tongues. It is introduced by a description of the concept of electronic tongues or taste sensors followed by a general overview of electrochemical measurement principles that have been used for electronic tongues. A special emphasis is given on measurement principles for voltammetric electronic tongues, also including pulse voltammetry and variable reduction. Applications of voltammetric electronic tongue are described, such as in the food industry, environmental analysis, paper and pulp industry, household appliances and agriculture. Future developments of the concept, such as self polishing or miniaturized devices are also described. Finally, a continuous measurement system for chemical oxygen demand (COD), which has been commercialized, is depicted.
|
|
