Top-Down Proteomics of a Drop of Blood for Diabetes Monitoring

[Image: see text] The most common markers for monitoring patients with diabetes are glucose and HbA1c, but additional markers such as glycated human serum albumin (HSA) have been identified that could address the glycation gap and bridge the time scales of glycemia between transient and 2–3 months. However, there is currently no technical platform that could measure these markers concurrently in a cost-effective manner. We have developed a new assay that is able to measure glucose, HbA1c, glycated HSA, and glycated apolipoprotein A-I (apoA-I) for monitoring of individual blood glycemia, as well as cysteinylated HSA, S-nitrosylated HbA, and methionine-oxidized apoA-I for gauging oxidative stress and cardiovascular risks, all in 5 μL of blood. The assay utilizes our proprietary multinozzle emitter array chip technology to enable the analysis of small volumes of blood, without complex sample preparation prior to the online and on-chip liquid chromatography–nanoelectrospray ionization mass spectrometry. Importantly, the assay employs top-down proteomics for more accurate quantitation of protein levels and for identification of post-translational modifications. Further, the assay provides multimarker, multitime-scale, and multicompartment monitoring of blood glycemia. Our assay readily segregates healthy controls from Type 2 diabetes patients and may have the potential to enable better long-term monitoring and disease management of diabetes.