Abstract
Molecular biomarkers are very important in biology, biotechnology and even in medicine, but it is quite hard to convert biology-related signals into measurable data. For this purpose, amperometric biosensors have proven to be particularly suitable because of their specificity and sensitivity. The operation and shelf stability of the biosensor are quite important features, and storage procedures therefore play an important role in preserving the performance of the biosensors. In the present study two different designs for both glucose and lactate biosensor, differing only in regards to the containment net, represented by polyurethane or glutharaldehyde, were studied under different storage conditions (+4, −20 and −80 °C) and monitored over a period of 120 days, in order to evaluate the variations of kinetic parameters, as VMAX and KM, and LRS as the analytical parameter. Surprisingly, the storage at −80 °C yielded the best results because of an unexpected and, most of all, long-lasting increase of VMAX and LRS, denoting an interesting improvement in enzyme performances and stability over time. The present study aimed to also evaluate the impact of a short-period storage in dry ice on biosensor performances, in order to simulate a hypothetical preparation-conservation-shipment condition.
Highlights
Amperometric biosensors, a category of chemical sensors, combine the specificity of biological recognition procedures with high sensitivity [1], linked to the validity of electrochemical techniques
The second was a lactate biosensor that employs the capability of lactate oxidase (LOx) to selectively transform L-lactate as follows: L-Lactate + FAD+ -LOx → Pyruvate + FADH2 -LOx
While at +4 ◦ C this parameter suffered a general decrease, at −20 ◦ C the phenomenon was partially attenuated, producing higher values compared to +4 ◦ C data
Summary
Amperometric biosensors, a category of chemical sensors, combine the specificity of biological recognition procedures with high sensitivity [1], linked to the validity of electrochemical techniques. Biosensors hold a biological element, represented by tissues or receptors, nucleic acids, antibodies, proteins or even whole cells, but more often enzymes, for the selective recognition of the studied compounds. In the case of amperometric biosensors, an enzymatic reaction usually generates an electrical signal that is proportional to the studied-compound concentration [1,2]. The first one was a glucose biosensor that exploits the capability of glucose oxidase (GOx) to selectively convert D-glucose as follows: β-D-Glucose + FAD+ -GOx → D-Glucono-δ-Lactone + FADH2 -GOx. FADH2 - GOx + O2 → FAD+ -GOx + H2 O2. The second was a lactate biosensor that employs the capability of lactate oxidase (LOx) to selectively transform L-lactate as follows: L-Lactate + FAD+ -LOx → Pyruvate + FADH2 -LOx. FADH2 -LOx + O2 → FAD+ -LOx + H2 O2. In a 1999 paper [11], Gibson defined the biosensor stability as the feature depending mainly on the enzyme immobilization procedures on the biosensor active surface
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