Electrochemical Study of Enzymatic Glucose Sensors Biocatalyst: Thermal Degradation after Long-Term Storage

Abstract

The thermal degradation related to stability in long-term storage of a carbon nanotube-based biosensor has been investigated. The effect of storage temperature on detachment and denaturation of glucose oxidase (GOx) biocatalyst has been proved. The carbon nanotubes (CNTs) coated with polyethyleneimine (PEI) as entrapping polymer to attract more GOx to form a durable and layered CNT/PEI/GOx structure is used for long-term storage to minimize GOx detachment from the structure and minimize the possibility of enzyme and protein denaturation. After 120 days, the glucose response of the CNT/PEI/GOx biosensor stored under 4°C is preserved up to 66.7% of its initial value, while under a 25 °C storage the response is maintained up to 41.7%. The enzyme coverage activity of CNT/PEI/GOx stored at 4 °C and 25 °C has decreased by 31.1% and 51.4%, respectively. Denaturation and detachment of GOx are the common causes of thermal degradation in biosensors under improper storage temperatures, but the presence of PEI in the structure can slow-down these phenomena. Moreover, the electrons transfer constant of CNT/PEI/GOx biocatalyst stored at 4 °C and 25 °C were 7.5 ± 0.5 s−1 and 6.6 ± 0.3 s−1, respectively, indicating that also electrons mobility is damaged by detachment and denaturation of enzyme protein and the detection of glucose from the glucose oxidation reaction (GOR) is compromised.

Recent advances in flexible sweat glucose biosensors

“…It is an attractive alternative technology to use nano-materials instead of enzymes to detect glucose [94][95][96][97]. Although the enzyme-based glucose biosensors have excellent selectivity and sensitivity, there are shortcomings such as high cost, insufficient long-term stability caused by denaturation, and limited environmental conditions (temperature, pH, and humidity) [98][99][100][101]. The mechanism of the non-enzymatic biosensor is shown in figure 7(a).…”

“…The mechanism of the non-enzymatic biosensor is shown in figure 7(a). Nano-materials have significant advantages, lower cost, long-term stability, and low response time [95][96][97][99][100][101][102]. Nano-materials like noble metals (e.g.…”

Soft Materials for Wearable/Flexible Electrochemical Energy Conversion, Storage, and Biosensor Devices

“…Even if from the conceptual point of view, the selection of the enzymes and cofactors related to the target substrate in the physiological fluid to be exploited is the first step, this is a tied choice because the most convenient combinations of enzymes, cofactors, and substrates are already known, and the choice is limited [194]. It should be also stated that these delicate biotic components, due to their easy degradation, leaking, long-term stability, and denaturation issues [195,196], must be applied to the EFC as the last ones by steps and procedures not involving warm temperatures, extreme pHs, and aggressive washings. Impregnation, layer-by-layer, air-drying, and weak interaction-based orientation methods are used for the fixation of enzymes [197,198].…”

Gold Nanoparticles in Porous Silicon Nanotubes for Glucose Detection

“…However, the devices have not gone through the process of being classified as medical devices by the FDA [5]. One of the main disadvantages of this method is that the enzymes used are susceptible to environmental conditions, such as temperature and humidity, which can significantly affect the shelf life of the devices [6]. This method also requires a painful finger prick to acquire the blood needed for the test.…”