Next generation pathogen detection with lab-on-a-chip platforms

Taking a sample could be as simple as a fingerprick of blood, as is common in blood sugar monitoring. 

The metal microdiscs sputtered on a glass slide at MCN. The posts are 5 µm in diameter and 300 nm high. 

The schematic drawing of the pathogen detection: DNA extraction, purification, amplification and detection. 

March 2015

Detection of pathogens is of critical importance for disease diagnosis, food safety control, water quality monitoring and homeland security. Traditional detection methods, such as colony counting following cell culture, polymerase chain reaction (PCR) and enzyme immunoassay, have been extensively employed to pathogen detection. But they require special laboratories, trained professionals and hours, if not days, to achieve the required analysis.

The portable lab on a chip platform developed in this project enables the detection of multiple pathogens within 30 minutes, with only a tiny sample, such as a drop of blood or saliva. The detection process is as easy as blood sugar monitoring used daily by diabetics: drop the sample on a disposable microchip, measuring just 5cm x 7cm x 0.4 cm, insert the chip into the reader and read the results after half an hour. It is fully automatic and no longer relies on sophisticated equipment and trained professionals. Furthermore, it not only greatly reduces the complexity and detection time but dramatically increases detection sensitivity. It holds great potential to benefit the medical clinics, food industries, as well as departments of environmental monitoring and homeland security.

Led by Dr. Yonggang Zhu, CSIRO researchers from multiple disciplines have been collaborating with industry partners to develop a lab-on-a-chip platform with three key capabilities including automatic liquid handling, sample processing and individual bead trapping and imaging. The liquid handling system is applied to load the samples (such as blood, saliva, urine, etc.) and reagents are placed into a microwell for further processing. Then magnetic microbeads and an electromagnetic/acoustic system are applied to mix and capture the analyte. Finally, the microbeads coupled with analyte are individually captured and imaged by fluorescence microscopy or Surface Enhanced Raman Spectroscopy (SERS).

The core component of this platform is the microfluidic chip with microchannels, a microwell and metal microstructures for the sample processing and detection. It is fabricated using the photolithography facilities and sputtering tools at MCN.

Proof of concept studies have shown successful detection of DNA from E. Coli (bacteria) using this lab on a chip platform. DNA was lysed from whole E. Coli cells and purified on the chip within 15 minutes. Then the small number of DNA molecules were amplified in situ for a further 15 minutes. Following the amplification, concentrated DNA molecules weres able to be detected using fluorescence microscopy.

Future work will focus on the optimisation of the platform in terms of hardware, detection methods and software to further shorten the detection time, reduce the detection limit (therefore detecting fewer pathogens in a given volume) and increase its ability in detecting multiple pathogens.