A team of scientists from the University of Texas at Arlington and the Massachusetts Institute of Technology (MIT; Cambridge, MA) has overcome past limitations on quantitative microscopy through an opaque medium by using a combination of quantitative phase imaging and near-infrared (NIR) light.1 A decade-old "label-free" technique, quantitative phase imaging uses shifts in phases of light, instead of staining, to facilitate imaging.
The approach enables quantitative observation of cellular processes taking place in lab-on-a-chip devices. "To the best of our knowledge, this is the first demonstration of quantitative phase imaging of cellular structure and function in silicon environment," said Samarenda Mohanty, head of the Biophysics and Physiology Laboratory at UT Arlington.
The technology has potential application in drug development and disease diagnosis. "Silicon-based micro devices known as labs-on-a-chip are revolutionizing high-throughput analysis of cells and molecules for disease diagnosis and screening of drug effects. However, very little progress has been made in the optical characterization of samples in these systems," said Bipin Joshi, a recent graduate and lead author on the paper. "The technology we've developed is well suited to meet this need."
The researchers proved success in analyzing specimens through a silicon wafer in two instances. In one, they accomplished full-field imaging of the features of red blood cells to nanometer-thickness accuracy. In another, they observed dynamic variation of human embryonic kidney cells in response to change in salt concentration. Mohanty believes that the work could lead to noninvasive monitoring of neuronal activity.
"We envision that this significantly expands the visualization possible in silicon-based microelectronic and micromechanical devices," added Ishan Barman, now an assistant professor at Johns Hopkins University.
1. B. Joshi et al., Sci. Rep., 3, 2822 (2013); doi:10.1038/srep02822.