Extreme Physiological State: Development of Tissue Lactate Sensor

Lactate is one of the most important biomarkers of tissue oxygenation and thus of paramount importance for sports and health care applications. Lactate levels provide information on anaerobic threshold which is very important for tailoring training programs in endurance sports. In this contribution we present an implantable amperometric lactate sensor for continuous in vivo monitoring. A needle based construction is used where a sensing platinum wire is inserted into a stainless steel tube that serves as a combined counter and reference electrode allowing for easy insertion, small size and minimally invasive procedure. The sensing enzyme layer is sandwiched between two polymer membranes which allow high selectivity, a wide lactate linear range and biocompatibility. The sensors have been fully evaluated in vitro and tested in vivo in rats. The measured values of tissue lactate obtained with our sensors were compared with lactate levels measured in blood by the commercial Lactate Pro analyzer. The obtained concentrations were in the same range, however, no clear correlation between blood and tissue values was found. Coldsterilisation by gamma radiation, required for human studies, is currently being investigated. This work will provide valuable information on lactate levels in different physiological compartments and increase our understanding of physiological processes related to endurance sports.