Plucking proteins from single cells

As part of a £5 million initiative of the Engineering and Physical Sciences Research Council, scientists in the UK have developed a microfluidic tool to mine proteins from cells.

The system, developed by Mark Neil, Oscar Ces and their colleagues at Imperial College London, uses oil droplets to solubilise and extract proteins from targeted points on a cell's plasma membrane. The spatially selective sampling is done without solubilising the whole membrane and so doesn't destroy the cell, meaning that the scientists can follow single cells to study how protein levels vary in both space and time.

By trapping their microtools with laser beams (red curves) the UK team can target single cells

Ces explains that the initiative, called the Single Cell Proteomics project, is a five and a half year multidisciplinary research collaboration whose aim is to create a suite of technologies to study proteins in single cells. 'Integrating the different technologies required to undertake single cell analysis is challenging,' he says, 'and there are few combinations of researchers with the combined know-how at present.'

"The team plans to look at how changes in protein levels in the plasma membrane affect signalling pathways involved in cancer growth."

The team's droplets are called smart droplet microtools (SDMs). They consist of detergent-coated oil droplets optically trapped, or controlled, using two laser beams. The SDMs can be manipulated using a microfluidic device to enable interactions between the cells and the droplets. Ces explains that protein transfers from a cell to an SDM through interactions with the detergent. It can then be analysed, with the SDM effectively acting as a storage vessel for the protein.

Adam Woolley, an expert in microfluidic systems for bioanalysis, at Brigham Young University in Provo, US, comments: 'This work showcases a clever combination of optical trapping with microfluidic manipulation of droplets and cells. The approach looks to be especially promising for the spatially localised characterisation of cell membrane components, particularly if methods can be developed to enable quantitation of targeted compounds.'

The team now plans to develop the technology for tackling key biological questions, such as how changes in protein levels in the plasma membrane affect signalling pathways involved in cancer growth. Ces suggests that the SDMs could ultimately be used to deliver material to single cells. 'We believe the platform has a great deal of potential,' he says.

Katherine Davies

http://www.rsc.org/Publishing/Journals/cb/Volume/2009/3/plucking_proteins_from_single_cells.asp