Sensing molecules released from single cells without using labels

Although many bioanalytical methods study the average behavior of cells across a collection, biologists have started to realize that individual cells often act differently than their neighbors. To learn more about such heterogeneity, researchers need to perform single-cell analyses, but existing methods to do so usually require multiple steps and the addition of fluorescent labels. Now, a device combining microfluidics and nanophotonics may save time by isolating single cells and detecting cellular secretions without using labels (Small 2018, DOI: 10.1002/smll.201800698). The research is a collaboration between RMIT University and Swiss Federal Institute of Technology, Lausanne (EPFL), led by EPFL’s Hatice Altug. In the device, a microfluidic chamber isolates and houses a single lymphoma cell. Under the chamber, a biosensor chip coated with a gold film transmits light at a specific wavelength via plasmonic nanostructures. The chip is treated with antibodies that bind biomolecules called cytokines. As the antibodies capture cytokines released from the cell, the mass deposited on the chip increases, leading to a shift in the wavelength of the transmitted light. The researchers analyze the outgoing light and, using the degree of wavelength shift, calculate how many cytokine molecules were captured. Coauthor Xiaokang Li of EPFL, says that in principle the biosensor could also study other cell types by using chips coated with antibodies that bind molecules relevant to a given system.