Optical biosensors for probing at the cellular level: a review of recent progress and future prospects.

New approaches are required to understand the complex processes taking place in the smallest unit of life. Recent years have seen an increasing activity in the use of optical devices and techniques for the investigation of the properties of single cells and also populations of cells including cell to cell communication. This article reviews relevant optical technologies to date as well as new advances in biosensor development, and goes on to explore reported applications in detection of biotargets and cellular signalling pathways inside individual living cells.