MicroRNA are short, single-stranded, noncoding RNA molecules that help regulate gene expression. Cancer cells release microRNA in vesicles called exosomes to communicate with other cells. Capturing and deciphering these messages could lead to development of more precise and personalized cancer treatment.

Current techniques to detect and quantify exosomal microRNA, such as reverse transcription-polymerase chain reaction (RT-PCR), are slow and prone to biases. An article in Biomicrofluidics reports a new technique for detecting exosomal microRNA that is simpler, faster and more sensitive than conventional techniques without applying enzymatic amplification.

Ion concentration polarization (ICP) is an electrokinetic transport phenomenon that occurs near a permselective membrane in a microfluidic channel and is used for preconcentration of biomolecules by electrokinetic trapping. The new technique integrates an ICP-based microfluidic concentrator with a morpholino microarray. Morpholinos, which are synthetic nucleic acid analogs, act like capture probes for microRNA.

To test their technique, the authors created a concentrator device on a microfluidic chip. They printed an array of morpholinos on a glass slide, added a conductive polymer and applied an electrical voltage, inducing ICP. Their targets were microRNA-21 and microRNA-155, which are expressed in many cancers, including breast and lung cancer cells. During a concentration period of 30 minutes, the microRNA target molecules in the concentration plug rapidly hybridized with the immobilized morpholino probes located at the bottom of the microchannel.

Their new technique increased hybridization between microRNA and morpholinos, reducing detection time from about 24 hours to 30 minutes. Next, the researchers will apply their technique to exosomes extracted from breast cancer cells.

Source: “Rapid detection of exosomal microRNA biomarkers by electrokinetic concentration for liquid biopsy on chip,” by Lucia S. Cheung, Xi Wei, Diogo Martins, and Yong-Ak Song, Biomicrofluidics (2018). The article can be accessed at https://doi.org/10.1063/1.5009719.