Cancer Biomarkers Detected Directly In Blood

The device identifies cancer biomarkers, which are biological indicators of the disease that often circulate in the blood prior to the appearance of symptoms.

Scientists at the Shanghai Institute of Microsystem and Information Technology (China) have developed a simple, power-free, whole blood, immunoassay, microfluidic system. The procedure integrates plasma extraction with on-chip nanoenzyme-linked immunosorbent assay (ELISA) for a highly sensitive immunoassay. This device uses a pre-degassed polydimethylsiloxane (PDMS) bulk containing mesh-shaped chambers as a suction pump to drive the fluid motion in the chip's microchannels during plasma separation and immunoassay. The system is powered by the pre-degassed bulk PDMS without using external power sources which would be useful for point-of-care diagnosis.

Carcino-embryonic antigen (CEA) and serum cytokeratin fragment 21-1 (CYFRA21-1) were used as model cancer biomarkers to demonstrate the ability of this system to directly detect these biomarkers in whole blood. To develop a simple and portable method, the investigators integrated the plasma separation and biomarker detection with microfluidic methods that combined ELISA and silver signal amplification. In contrast to most other microfluidic assays, they adopted reduction of silver ions onto gold nanoparticles in the ELISA procedure that allowed the signal to be amplified on a solid substrate under continuous fluid flow. The silver amplification readout was monitored using an optical microscope.

The authors concluded that the advantages of this biosensor over other currently available rapid tests for cancer biomarkers is that it can be operated without special equipment, with minimal training, and the cost of reagents is low. The device has potential for point-of-care applications because it is fast, disposable and easy to use and has a low sample volume and low cost. The device allows users to read results with the naked eye or a digital camera, eliminating the need for any expensive and complicated equipment, which makes it suitable for use in low technology, rural or field conditions.

Gang Li, PhD, a senior author of the study said, “Our device is well suited to helping early diagnosis in resource-limited settings where no mechanical pumps or power sources are readily available because it is portable, affordable, sensitive, and specific, and delivered by technology with a user-friendly analytical platform.” He noted that the specialized pump could be prepared in advance and stored in an airtight package. The study was published on May 23, 2013, in the journal Biomicrofluidics.

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Shanghai Institute of Microsystem and Information Technology