A. Baingane, N. Mburu, C. Animanshaun, G. Slaughter
University of Maryland Baltimore County,
Keywords: multi-walled carbon nanotubes, glucose, lactate, biosensing, organ preservation
Summary:Organ preservation plays a major role in improving the clinical outcome of transplantation. Extracorporeal perfusion systems have been developed for solid-organ transplants (e.g. liver) and recently, investigators have demonstrated incremental improvements in preserving porcine vascularized composite allografts (VCA) viability through ex vivo perfusion. Yet, there is a burgeoning need for novel technologies capable of non-invasive, real-time monitoring of the tissue viability prior to transplantation, which would significantly increase the efficacy and availability of life-changing VCA. Thereby, following tissue procurement, lactate, a key biomarker of stress increases and the main source of metabolically-produce acid responsible for tissue acidosis. Lactate levels have also been found to correlate with the severity of injury and decrease in oxygen availability, making lactate a surrogate for oxygen debt. Small molecules such as lactate and glucose exists in equilibrium between the interstitial and vascular compartments when systemic levels are elevated. Interstitial levels of these metabolites should thus be reflective of systemic levels when tissue hypoxia occurs and can correlate to their levels in extracorporeal fluids (e.g., perfusate). The ability to monitor these metabolites in vitro and ex vivo is possible, but current methods are unreliable because they suffer from deleterious effects of interferences and fouling. Here we report on the development of a dual-implantable self-powered biosensing system for temporary placement underneath tissue bed to continuously monitor metabolites non-invasively for periods varying from several minutes to 72 hours. The self-powered biosensing system is constructed from two 500 um x 500 um massively dense mesh network of multi-walled carbon nanotubes (MWCNTs) biofuel cells employing pyroquinoline quinone glucose dehydrogenase (PQQ-GDH) as the biocatalyst for the glucose oxidation and D-Lactate dehydrogenase (D-LDH) as the biocatalyst for lactate oxidation. A common platinized MWCNTs electrode served as the cathode for the reduction of molecular oxygen. Two 1 uF capacitors functioning as transducers were coupled with an energy amplification circuit to amplify the power output from each of the biofuel and charge the corresponding capacitor. The charging/discharging frequency of the capacitors constituted the biosensors. The biosensors displayed the levels of lactate and glucose and these results showed excellent comparison to systemic levels of lactate and whole organ oxygen debt. The device development and integration challenges will be discussed in the paper.