Microfluidic technologies for nucleic acid analysis in liquid biopsies

Nucleic acids (NAs), such as DNA, RNA, and microRNAs, a type of non-coding RNA, are circulating in the blood at low concentration. Their presence is the result of several metabolic phenomena associated to in particular cell death or secretion. Alterations of the genetic material of cancer cells or metabolic deregulations are therefore conveyed with the blood stream away from the tumoral tissue, so that circulating NAs constitute excellent biomarkers obtained from non-invasive liquid biopsies. Circulating NAs present an interesting potential for the early detection or follow up of e.g. pancreatic cancer [1], for which the late detection results in a high mortality rate (nearly 100%). Therefore pancreatic cancer is in need for early detection methods which will allow the therapy to start before the metastasis stage of the disease [2]. The low amount of circulating NAs in liquid biopsies is however the major obstacle for their use as routine biomarkers, for its processing is time-consuming.

Our work aims to develop a lab on a chip for the manipulation of low NAs concentrations (>1pg/mL) in a short analysis time (<5 min) and for the detection of cancer biomarkers. A first step of sample preparation allows the enrichment (up to 1000x/min) and size sorting of the biomarker (20-50000 base pairs) [3]. A later step allows the optical detection of specific mutations through the use of molecular beacon probes. In addition, our technology is compatible with the handling of complex biological samples such as blood plasma. The development of an integrated platform combining sample preparation and detection is attractive to provide doctors and biologists a reliable, cheap, and ready to use diagnostic tool.

REFERENCES:

  1. "Detection of Circulating Tumor DNA in Early- and Late-Stage Human Malignacies”, B. Bettegowda et al., Science Translational Medecine (2014).

2.   “Written in blood”, E. Yong, Nature (2014).

3.    “DNA separation and enrichment using electro-hydrodynamic bidirectional flows in viscoelastic liquids”, H. Ranchon et al., Lab on a Chip (2016).

Figure legend: The upper panel sketches the microfluidic technology for DNA enrichment and separation. The microchannel comprises a funnel, in which the transport of DNA molecules is arrested at a position dependent of its size, as shown by the fluorescence micrograph below.