Use of microchip-based hydrodynamic focusing to measure the deformation-induced release of ATP from erythrocytes

In order to understand the role that erythrocytes play in conditions such as pulmonary hypertension, in vitro mimics of the microcirculation are needed. This paper describes the use of microchip-based hydrodynamic focusing to develop a mimic that allows both mechanical deformation of erythrocytes and quantification of the adenosine triphosphate (ATP) that is subsequently released in response to this deformation. In this mimic, two sheathing streams of a luciferin/luciferase mixture are used to focus and deform a central fluid flow of an erythrocyte sample. The focusing width is changed by simply manipulating the sheath flow rate. This allows a variety of cross-sectional areas to be studied using single point chemiluminescent detection. It was shown that increasing the sheath flow rate does result in elevated levels of ATP release. For example, one sample of rabbit erythrocytes released 0.80 (± 0.13) µM ATP when focused to a cross-section of 3480 µm2, while focusing the same sample to a smaller cross-section (1160 µm2) led to a release of 6.43 (± 0.40) µM ATP. In addition, two different inhibitors, diamide and glibenclamide, were used to ensure a lack of cell lysis. This approach can be used to examine a wide range of deformation forces in a high throughput fashion and will be of interest to researchers studying the mechanisms leading to vasodilation in the microvasculature.