Lab-on-a-chip technology for determination of protein isoform profiles

A new microfluidics device that uses immobilized antibodies and carbon nanostrings as detection agents can identify slight variations in protein composition, known as protein isoforms, that could indicate the presence of cancer. The device generates results in as little as 15 minutes.

Maria Lönnberg, Ph.D., and Jan Carlsson, Ph.D., of Uppsala University in Sweden, developed a lab-on-a-chip device to separate proteins based on slight variations in the sugar molecules that are attached to the majority of human proteins. These changes in sugar modification alter the net charge of a protein, a fact that the two investigators take advantage of by creating ion-exchange chromatography columns within the channels of a microfluidic device.

As a protein solution flows through the ion-exchange column, those molecules with a slightly greater charge move more slowly than those with a slightly smaller charge. Once separated, the proteins pass over a second region of the chip containing immobilized antibodies, which capture the proteins. Following this capture step, a solution containing a second antibody, this one linked to carbon nanostrings, is injected into the capture chamber. This detection antibody binds to any captured protein, producing a visible black stain within the device channels. Though easily seen with the naked eye, the researchers use an image scanner in order to quantify the amount of each trapped isoform.

Use of an image scanner also increases the number of individual proteins that can be detected, with the investigators noting that their device was capable of making 944 measurements on a single biological sample on one chip. The results of these experiments appear in the Journal of Chromatography A.

This work is detailed in a paper titled, “Lab-on-a-chip technology for determination of protein isoform profiles.” An abstract of this paper is available through PubMed. View abstract.

http://nano.cancer.gov