Integrated acoustofluidic sorting and characterisation for the enrichment of stem cell populations

After injury the body can become unable to fully repair itself. Regenerative medicine – where the patient’s own cells are used to enhance repair – requires quick provision of the right kind of cells. The use of ultrasound to characterise and sort cells on the basis of physical parameters such as size, density and compressibility (stiffness) is an area of increasing research interest. This is a gentle, non-contact method which does not require extensive biochemical preparation of samples.

Recently, fat tissue has been found to be an abundant source of stem cells – cells which can develop (differentiate) into a range of other cell types and which are essential for the body’s repair. To speed up clinical usefulness, however, it is necessary to select cells furthest along the path toward the desired type, such as Schwann cells, which actively support nerve repair. Levels of cell differentiation have recently been correlated to stiffness, which is measureable by ultrasound because this partially determines how sound waves bounce back.

The aim of this project, then, is the efficient mechanical sorting and analysis, through ultrasound, of potentially useful stem cells which could be used to repair damaged nerves. Initially, the type of ultrasound probe used to look at the cells will be similar to, though smaller than, probes used in hospitals. This work will take place alongside computational modelling, in order to understand how differences in stiffness correlate to the reflected signals. Results will be compared to standard laboratory tests normally used to determine the physical and biochemical characteristics of cells.
A new type of ultrasonic sensing will then be explored. This is based on the same principle as the cell manipulation techniques, such that, after integration with the sorting element, cells can be moved, grouped and analysed on the same device. The impact of this work ranges from regenerative medicine to diagnostics and cancer research (metastasis in ovarian cancer has been linked to increased cell compressibility) and it is potentially highly significant in reducing reliance on biochemical labelling, which can negatively affect cellular health and function, particularly of fragile entities such as stem-cells.