Posted: June 27, 2009

Nanoscale holes provide speed boost for diagnostic tests

(Nanowerk News) Microfluidic devices, essentially miniaturized chemical laboratories etched into material similar to a microprocessor chip, are revolutionizing diagnostic medicine by providing a technology platform that is more sensitive and less expensive than conventional analytical technologies. A new sensing method that relies on nanoscale holes drilled into a microfluidic device also could add “faster” to the list of benefits afforded by microfluidics.
Reporting their work in the journal Analytical Chemistry ("Nanoholes As Nanochannels: Flow-through Plasmonic Sensing"), researchers at the University of British Columbia created a grid of 30 x 30 flow-through nanoscale holes to create a highly responsive sensor system that can detect biomolecules of interest without requiring the additional use of an optical label. They used a tightly focused laser to drill holes through a 100-nanometer-thick layer of gold deposited on a 100-nanometer-thick slab of silicon nitride. The resulting sensor array then was integrated into a microfluidic chip made of poly(dimethylsiloxane), a standard material used to make lab-on-a-chip devices for biomedical applications.
With the array in hand, the investigators then attached a monoclonal antibody to the gold lining inside the holes. This monoclonal antibody binds to a cancer biomarker protein known as PAX8. The researchers then took advantage of an optical phenomenon known as surface plasmon resonance (SPR), which takes place on thin films of gold. When irradiated with laser light, thin gold films will emit a sharp, bright burst of light whose wavelength changes as various molecules stick to the gold surface. In this case, the SPR signal changed whenever PAX8 bound to the antibody attached to the gold film lining the array holes. When compared with established SPR-based measurement techniques, the flow-through device had a response time that was sixfold faster while measuring PAX8 present at concentrations in the attomolar range.
Source: National Cancer Institute
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