“Bio-X” Detection Devices
 

The aim of this research is to develop DNA chip and nanodevices or a lab-on-a-chip that can detect biomolecules like DNA, RNA, antigen, protein and microbial cells or “bio-Xs”. 

A DNA microchip is a format that allows parallel nucleic acid hybridization of a high-density micro-array of at least hundreds (or thousands) of oligonucleotides or clonal DNAs on a small surface area. It uses the binding property of DNA double strains or so-called hybridization. The single-stranded DNA target is labeled with a fluorescent tag and delivered to a designated area where the complementary DNA sequence or oligonucleotide is present. Following the basic hybridization and washing procedures, the signal of the probe-target interaction is measured and processed through analytical software. Such a format can provide enormously high throughput to studies in various biological systems. 

Figure 1: A microfluidic prototype showing the delivery channel, reaction chamber and trap device. 

A Lab-on-a-chip is a more advanced device that integrates multiple processes, including sample collection and pretreatment with the DNA/RNA extraction, amplification, fragmentation, labeling, hybridization and detection, on a microfluidic platform. It employs the most recent technological developments in microfabrication, microfluidics, and biosensors/microchip. Semiconductor-like fabrication techniques are primarily used to produce micro/nano-devices consisting of interconnected fluid reservoirs and pathways. Transport of samples is automated through selected pathways by the electrokinetic forces generated at designated electrodes, or by the voltage gradient between electrodes in capillary electrophoresis. Micro-valves and pumps are used to perform manipulations such as reagent dispensing and mixing, incubation/reaction, and sample partition, whiie analyte detection is achieved through various biosensing and nanoparticle-detection systems. 

Figure 1 shows the prototypes of a microdevice that contains a microchannel, a reaction chamber and a particle trapping device. This prototype is used to study fluid movement under microchannels with and without the presence of analytes, and will be evolved later to incorporate bacterial detection systems. The DNA microchip team led by Dr WT Liu has established the capability of producing DNA chips containing oligonucleotides and cDNA fragments for various biological targets. Further progress is made in the development of software, LabArray, for real-time detection and quantification, and post-statistical analysis of chip hybridization signals. Work is in progress to develop a rapid and sensitive lab-on-a-chip for simultaneous detection of waterborne pathogens, which will be further expanded and applied into other areas, from medical diagnostics and monitoring food and biological agents, to environmental bioremediation and crime analysis. 

The principal investigators are Dr WT Liu from the Department of Civil Engineering and Prof Simon Ang from the Department of Mechanical Engineering and the collaborators are Profs F Tay, FS Chau and MA Mannan from the Department of Mechanical Engineering.