Rapid label-free separation of stromal cell populations for autologous cell therapy in musculoskeletal diseases

The combination of autologous mesenchymal stromal cells (MSCs) with biomimetic scaffolds for tissue repair is a promising treatment strategy for musculoskeletal diseases. For this, the patients’ cells need to be harvested and concentrated intra-operatively. Current cell enrichment technologies are either limited by low selectivity, low throughput or by their intrinsic requirement for manipulation of the separated cells. By using surface acoustic waves dielectrophoresis (SAW-DEP), where virtual electrodes are created within a microfluidic channel using shear-horizontal surface acoustic waves generated on a piezoelectric material, cells can be separated with minimal manipulation. This technology has been previously shown to separate dead from alive dental pulp stromal cells in high conductivity fluids without the need for cell-labelling, and without heating or electrochemical reactions occurring. The aim of this thesis was to further the understanding of the SAW-DEP technology to increase the device’s throughput and determine its suitability to separate MSCs from other cell types found in bone marrow whilst maintaining their osteogenic potential. In order to understand better the underlying physics of SAW-DEP, the effect of parameters such as input power and channel height on the dielectrophoretic response of the system were investigated. These experiments showed that the throughput could be increased twenty-fold by exploiting the vertical dielectrophoretic forces in the channel using a multi-layered channel approach. The dielectric properties of MSCs and other white blood cells present in bone marrow were characterised and the differences found between the cell populations suggested that SAW-DEP has the potential to enrich MSC populations from bone marrow samples. The osteogenic potential of MSCs after exposure to SAW-DEP was assessed first in vitro and then in vivo by implanting human stem cell-seeded scaffolds into athymic rats with calvarial defects. The results showed the SAW-DEP exposure did not negatively affect the ability of MSCs to repair bone defects.