Enzymatic sensor of putrescine with optical oxygen transducer – mathematical model of responses of sensitive layer

Abstract

A biosensor for putrescine containing a sensing layer with an optical oxygen probe based on ruthenium complex and the enzyme diamine oxidase from pea is described. The diamine oxidase was pre-immobilised on broken micro-beads modified with a ferrofluid. The pre-immobilised enzyme and ruthenium complex were both incorporated into the UV-cured inorganic-organic hybrid polymer ORMOCER and deposited on a lens to form a sensitive layer of 210 µm in thickness. The sensitivity to the putrescine concentration determined under air saturation was between 3.50 µs L mmol −1 and 4.50 µs L mmol −1 in a hundred experiments conducted intermittently over a one year period. With the oxygen concentration increasing from 10 % to 100 % of DO (dissolved oxygen), the biosensor sensitivity decreased from 6.87 µs L mmol −1 to 0.70 µs L mmol −1 and its dynamic range increased from 0.10 mmol L −1 to 1.75 mmol L −1 . To estimate the behaviour of the putrescine sensor in parametric space, a mathematical model of the reaction-transport processes inside the sensing layer was developed. The model revealed the qualitative relations between the sensor analytical features, the characteristics of the sensitive layer and concentrations of substrates. The results of the mathematical modelling may serve as guidelines in the design of optodes for specific applications.

Analytical characteristics of a glucose sensor with an optical oxygen transducer for the monitoring of biotechnological processes

“…In order to estimate the qualitative and quantitative characteristics of GOR in the parameter space, we employed the mathematical model developed previously in our group [18]. The model consists of two reaction-diffusion equations for glucose and oxygen substrates:…”

“…The scheme of the spatial domain is plotted in figure 3. Three physically relevant dimensionless criteria were identified [18]:…”

“…Our previous work [18] has shown that the analytical characteristics of biosensors with enzyme oxidase and oxygen transducers are governed by the diffusion in the optically sensitive layers and amount of enzyme in these layers. The diffusion may be modified by adjusting the parameters of the layers, i.e.…”

“…In this work, the limits of the analytical characteristics of GOR were determined via the modification of the prep aration of optically sensitive layers and the measurement of glucose concentrations in aqueous solutions (c GS ) with dissolved oxygen (DO) from 0%-100%. In addition, a mathematical model based on reaction-diffusion equations [18] was adapted to the glucose oxidase kinetics and used for predictions of GOR characteristics in the parameter space. SEPA (200 mg) were activated by being stirred with glutaraldehyde (4.0 ml) for 4 h. The stirring velocity with a 1.0 cm long magnetic bar, was 20, 80 or 800 rpm.…”