Too big to bind? Atomic Force Microscopy and novel techniques for cell sorting in the development of cellular therapies

Research into large scale stem cell and cellular therapy purification is likely to become a significant challenge for the bioprocessing community. Current purification techniques such as fluorescence or magnetic cell sorting are only suitable for small scales of operation and for future exploitation of the technology larger scale techniques are needed. Of particular interest would be a simple, scalable purification technique for separating undifferentiated cells from a mixed cell population at varying degrees of differentiation, allowing therapies based on differentiated lineages to be “cleared” of potentially teratoma-forming pluripotent cells. Similarly, any technique that uses non-invasive or non-modifying properties to categorise cells phenotypically would be a powerful tool in other areas of biology and medicine.

Whilst research groups have identified the need for scalable suspension culture of stem cells to allow their full therapeutic potential to be realised, until recently very little attention has been paid to the downstream processing aspect.

We have used atomic force microscopy (AFM) to investigate physical properties of different cell types such as elasticity, topography and surface charge. By identifying significant differences in physical properties of cells during phenotypic transitions, we can develop more simplistic, robust and scalable purification techniques than those currently based upon complex antigen intereactions.

By studying variations in elasticity and surface charge properties of different cell types we are able to design separation devices based upon defined channels and charged porous surfaces which selectively purify a single cell phenotype from a mixed cell population.