Effect of spermidine and its metabolites on the activity of pea seedlings diamine oxidase and the problems of biosensing of biogenic amines with this enzyme

Spermidine is one of the several biogenic amines, produced during the microbial decarboxylation of proteins. Individual biogenic amines in the formed mixtures are frequently analyzed with oxygen sensor based biosensors, as their content serves as a good biomarker for the determination of food quality. In these biosensors, diamine oxidase from pea seedlings (PSAO), catalyzing the oxidation of various biogenic amines by dissolved oxygen is commonly used for the bio-recognition of amines. However, in the presence of spermidine and/or its metabolite 1,3-diaminopropane, the activity of PSAO and the sensitivity of PSAO-based biosensors decrease due to inhibition. The inhibition constant of soluble spermidine, acting as an inhibiting substrate toward PSAO, was found to be (40±15) mM in freshly prepared solution and (0.28±0.05) mM in solution, incubated 30 days at room temperature. The inhibition constant of 1,3-diaminopropane, acting as a competitive inhibitor, was (0.43±0.12) mM as determined through the oxidation reaction of cadaverine. The metabolic half-life of soluble spermidine was 7 days at room temperature and 186 days at 4 °C. The kinetic measurements were carried out with an oxygen sensor; the composition of the solution of degraded spermidine was analyzed with MS.

Determination of antibiotic residues and their interaction in milk with lactate biosensor

Milk and dairy products are among the most important foodstuffs and the quality of raw milk is of significant importance from the point of view of human health. For rapid determination of chloramphenicol and penicillin residues in raw milk, lactate oxidase-based amperometric biosensor was used. The concentration of antibiotic residuals was determined by two characteristic reaction parameters, calculated from the biosensor transient response with the dynamic biosensor model. Both chloramphenicol and penicillin caused the decrease of the value of the kinetic parameter, but they changed the total signal change parameter in different ways. The shift of the combined total signal change parameter at the simultaneous presence of these antibiotics indicated their antagonistic effect. Due to the respiration process of bacteria in raw milk, the dynamics of the biosensor signal was different in warm and cold seasons. The respiration characteristics were added to the biosensor model as a negative linear time-depending factor. The reaction characteristic parameters, obtained with this complemented model, showed excellent alignment in different conditions and allowed to detect antibiotic residues and their interaction in raw milk.

Survey of the year 2003 commercial optical biosensor literature

In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.