Single-cell Clinical Chemistry: Exploring Glucose Uptake Kinetics and HbA1c Levels in Individual Red Blood Cells.

Single-molecule techniques have been a primary focus of many advances in biophysics over the last decades. However, the fact that many related technologies such as microfluidics, confocal microscopy, etc. are becoming standard laboratory tools makes it possible to pursue other goals such as single cell measurements. If single molecules are the building blocks of matter, single cells are the building blocks of biology, and the individual detection thereof offers similar benefits. Currently, most blood work is cuvette-based, averaging tens of millions of blood cells to obtain a single ensemble value. Measuring single blood cells yields a distribution of values, which provides more information about a given patient as well as how that patient may differ from the general populace. All of which is important in an era of big data which increasingly inclines medicine towards a more personalized approach. Our work focuses on the relationship between glucose, red blood cells (RBCs) and glycated hemoglobin, as quantifying the interplay of these parameters is important for a better understanding of diabetes. Using a microfluidic perfusion system allows the placement of RBCs and control over the solutions to which they are exposed. Using confocal microscopy and image analysis, we are able to observe the kinetics of fluorescently-labeled glucose passing into and out of individual RBCs and extract the relevant information, such as glucose influx and efflux rates, intracellular vs blood glucose levels, and more. Overall, we seek to quantify the relationship between bloodstream and intracellular glucose levels to inform a more personalized, and perhaps improved, diagnostic strategy for diabetes. We are also currently developing methods for quantifying %HbA1c at the single cell level utilizing Raman microscopy and mass spectrometry.