An investigation into the possible use of glucose oxidase catalysed enzymatic reaction to generate heat for warming blanket

Abstract

Hypothermia is a medical condition in which the human body’s core temperature is 35°C or lower, well below the nominal temperature of around 37°C. Accidental/unintentional hypothermia is generally divided into mild, moderate and severe. Severe hypothermia patients are re-warmed using active internal/external methods. There is a market for portable non-electric based warming blanket in pre-hospital treatment but such product is not currently available. In this project, feasibility of glucose oxidase (GOX) based reaction is examined for use in an active warming blanket. GOX was chosen because the enzyme and its substrates are readily available, relatively cheap, safe and have relatively long shelf-life; essential for subsequent commercialization. In addition, GOX from Aspergillus niger is a well characterised glycoprotein, its catalyzed reaction: the oxidation of D-glucose (C6H12O6) to D-gluconolactone (C6H10O6) and hydrogen peroxide, releases significant amount of energy (200 kJ mol-1) which is necessary for the application examined here. GOX is Generally Regarded As Safe (GRAS) and is the basis of many industrial applications. In depth study was conducted to understand the various fundamental properties which govern the glucose oxidase catalyzed enzymatic reaction. The result shows that there were two pH optimums as well as increasing temperature optimum at decreasing pH. Thermostability of GOX increases from pH 3.8 to 7.5 as well as in the presence of sodium chloride and/or glucose. Stabilization due to dissolved sodium chloride and glucose are cumulative because they act via different mechanism and was demonstrated with fluorescence emission. Upon drying, GOX activity decreases 60% immediately and gradually decreases further over longer time. Unexpectedly, additions of thermo-stabilizers do not increase the stability of dried GOX but actually accelerates its rate of degradation over time. These findings are important factors to consider when the proposed warming blanket utilizing GOX is ready for commercial use. To examine the heat transfer characteristics and performance of GOX reaction, a simple experimental model was built. The model consists of a reaction chamber where the reaction mixture is pumped into a prototype blanket insulated by polystyrene box. Fitting the experimental data into a hypothetical naked human model covered only with the prototype blanket, shows that the warming blanket concept utilizing the GOX heat generation reaction is feasible only if the reaction rate and/or scale of reaction is increased several times.