Transdermal Micro-Implantable Metabolite Sensor with Optical Communication

Early warning of impending shock, organ failure, and hypoperfusion are critical to implementing an effective treatment approach in emergency medicine. However, vital signs often do not change until a patient is already in critical condition, and it is too late to intervene effectively. Blood lactate levels have been suggested as a more sensitive parameter for measuring a patient's condition, because lactate levels change early during life-threatening situations such as hemorrhagic shock and sepsis. In fact, frequent serial measurements of lactate over the course of treatment that guide a goal-directed therapy have been shown to decrease mortality rates significantly. Unfortunately, lactate guided treatment is rarely practiced due to the logistical burden of taking serial measurements using point-of-care devices or as part of a lab panel. To address this unmet need, a microchip device to continuously monitor lactate for the duration of inpatient care has been developed. It was found that the microchip could be made such that it is implanted just under the skin surface and an optical probe is used to measure the reported response on the skin surface by passing and receiving light through skin. The microchip responds to changes in lactate concentration by utilizing an enzyme with high specificity and selectivity for lactate. A molecule that reports the enzyme-mediated response is embedded in the microchip. Manufacturing techniques have been developed to reproduce the microchips effectively, and the chips have been tested for use and accuracy in rabbit models of cyanide poisoning, where lactate levels change rapidly. The microchip platform has the ability to be loaded with alternate chemistries for detecting other bio-analytes, such as glucose, oxygen, CO2, pH, etc. An optical probe suitable for passing light through skin and receiving the microchip light emission for use in animal studies was created along with software to analyze the emission signals. When calibrations of implanted chip response to lactate were compared to gold-standard blood lactate measurements across the physiological and pathological range in 12 separate models of cyanide poisoning in rabbits the average error was 11%