Person:

Matoori, Simon

In emergency medicine, blood lactate levels are commonly measured to assess the severity and response to treatment of hypoperfusion-related diseases (e.g., sepsis, trauma, cardiac arrest). Clinical blood lactate testing is conducted with laboratory analyzers, leading to a delay of three hours between triage and lactate result. Here we describe a fluorescence-based blood lactate assay, which could be utilized for bedside testing, based on measuring the hydrogen peroxide generated by the enzymatic oxidation of lactate. To establish a hydrogen peroxide assay, near-infrared cyanine derivatives were screened and sulfo-cyanine 7 was identified as a new HRP substrate, which loses its fluorescence in presence of HRP and hydrogen peroxide. As hydrogen peroxide is rapidly cleared by erythrocytic catalase and glutathione peroxidase, sulfo-cyanine 7, HRP, and lactate oxidase were encapsulated in a liposomal reaction compartment. In lactate-spiked bovine whole blood, the newly developed lactate assay exhibited a linear response in a clinically relevant range after 10 min. Substituting lactate oxidase with glucose and alcohol oxidase allowed for blood glucose, ethanol, and methanol biosensing, respectively. This easy-to-use, rapid, and versatile assay may be useful for the quantification of a variety of enzymatically oxidizable metabolites, drugs, and toxic substances in blood and potentially other biological fluids.