Image: A composite image of HeLa cells stained sequentially with antibodies to five different proteins.

UW Bioengineering Associate Professor Xiaohu Gao’s lab has demonstrated a new method to speed up biological assays. The researchers’ solution could reduce time waiting for an assay to produce results from hours and days to mere minutes. The research team, which included Junwei Li and Pavel Zrazhevskiy, published their work Jan. 8 in the journal Small.  The research was also featured in UW Today.

Typical biological assays use molecules that detect specific proteins or pieces of DNA, which provide a visible marker or indicator when they successfully bind. However, large detector molecules have difficulty moving through the solution in which they are suspended and binding to their targets at the bottom of a petri dish or plate.

This “diffusion limitation” problem results in a long wait time for results. Researchers have proposed different techniques for speeding up the diffusion process, but their methods have yielded only minor improvements.

Dr. Gao and his team decided to explore a new approach to this diffusion limitation problem. Instead of waiting for the detector molecules to diffuse through the solution and bind to their targets, they sealed and inverted the sample, draining the solution. They replaced the solution, and repeated the process several times.

This “cyclic solution draining and replenishing” process, which could be compared to a washing machine cycle or making a cup of tea, was tested with ELISA and immunofluorescence microscopy staining techniques.

The researchers discovered that their protocol dramatically reduced reaction times, in one case from one hour to seven minutes. The researchers propose that this method could speed up experiments in the lab and reduce wait times for medical diagnostics.