Label free capacitive immunosensor for detecting calpastatin--a meat tenderness biomarker.

An immunological capacitive biosensor for calpastatin was developed, optimized and applied for the analysis of meat extract samples. Anti-calpastatin antibody was immobilized on a gold electrode modified with a self-assembled monolayer of mercaptoundecanoic acid and Protein A from Staphylococcus aureus, and the obtained immunosensor was inserted as the working electrode in an electrochemical cell of a flow injection system. The dynamic range of the sensor was 20 to 160 ng/mL calpastatin.

Monitoring of glucose and glutamate using enzyme microstructures and scanning electrochemical microscopy.

Glucose oxidase and glutamate oxidase lines, with typical width of 100 microm, were patterned on gold surfaces using a micro-dispensing system, by shooting 100 pl droplets of the corresponding enzyme solutions. The probe of a scanning electrochemical microscope (SECM) was then carefully positioned in the close proximity of the enzyme microstructure and poised to +600 mV vs. Ag/AgCl, KCl 0.

Intact and permeabilized cells of the yeast Hansenula polymorpha as bioselective elements for amperometric assay of formaldehyde.

Intact and permeabilized yeast cells were tested as the biorecognition elements for amperometric assay of formaldehyde (FA). For this aim, the mutant C-105 (gcr1 catX) of the methylotrophic yeast Hansenula polymorpha with a high activity of AOX was chosen. Different approaches were used for monitoring FA-dependent cell response including analysis of their oxygen consumption rate by the use of a Clark electrode, as well as assay of oxidation of redox mediator at a screen-printed platinum electrode covered by cells entrapped in Ca-alginate gel.

Simultaneous detection of L-glutamate and nitric oxide from adherently growing cells at known distance using disk shaped dual electrodes.

An ex vivo system for simultaneous detection of nitric oxide (NO) and L-glutamate using integrated dual 250 microm platinum disk electrodes modified individually with suitable sensing chemistries has been developed. One of the sensors was coated with an electrocatalytic layer of Ni tetrasulfonate phthalocyanine tetrasodium salt (Ni-TSPc) covered by second layer of Nafion, which stabilises on the one hand the primary oxidation product NO(+) and prevents interferences from negatively charged compounds such as NO(2)(-). For glutamate determination, the second electrode was modified with a crosslinked redox hydrogel consisting of Os complex modified poly(vinylimidazol), glutamate oxidase and peroxidase.

A new enzymo-chemical method for simultaneous assay of methanol and formaldehyde.

A new enzymo-chemical method for the simultaneous assay of methanol and formaldehyde in mixtures is described which exploits alcohol oxidase (AO) and aldehyde-selective reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH). The enzyme is used for methanol oxidation to formaldehyde and MBTH plays a double role: 1) at the first step of reaction, it forms a colorless azine adduct with pre-existing and enzymatically formed formaldehyde and masks it from oxidation by AO; 2) at the second step of reaction, non-enzymatic oxidation of azine product to cyanine dye occurs in the presence of ferric ions in acid medium. Pre-existing formaldehyde content is assayed by colorimetric reaction with MBTH without treating samples by AO, and methanol content is determined by a gain in a colored product due to methanol-oxidising reaction.