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Gold nanoholes poised to improve medical sensors

Posted: 26 Sep 2013 ?? ?Print Version ?Bookmark and Share

Keywords:medical sensor? gold nanohole? surface plasmon resonance? electron-beam lithography?

A team of researchers at the A*STAR Institute of High Performance Computing in Singapore has found a way to efficiently manufacture arrays of gold nanoholes that enables sensor chips built using these nanostructures to accurately detect cancer-related molecules in the blood and are small enough to be used in portable medical devices. They added that the nanohole arrays are designed so that incident light of certain wavelengths will induce large-scale oscillations of the gold electrons, known as localized surface plasmon resonance (SPR), which focuses the absorbed light energy to enhance fluorescence.

"Commercial SPR systems are already used in hospital laboratories, but they are bulky and expensive," stated Ping Bai, lead author of the study. "We would like to develop small, handheld devices for on-the-spot clinical use. This requires localized SPR, for which we need nanohole arrays."

Previously, nanohole arrays have been created using electron-beam lithography (EBL), which is expensive and time consuming. Bai and co-workers used EBL to create a nickel mould and then used the mould to print nanohole patterns onto a photoresist material. The researchers made the nanostructures by evaporating gold onto the patterned structure before peeling off the photoresist material. Because the nickel mould can be reused many times, this methodcalled nano-imprintingcan produce large numbers of gold nanohole arrays.

"We fabricated arrays of 140nm2 nanoholes with very few defects," noted Bai. As a first demonstration, the researchers showed that a sensor chip made with their nanohole arrays could detect prostate cancer antigens in blood, and was ten times more sensitive than an identical device that used a gold film without nanoholes. Optimising the chip design would further improve the sensitivity, Bai said.

The team believes that these chips could be incorporated into cheap and portable point-of-care devices for rapid diagnosis of diseases such as dengue fever. "The microfluidic cartridge built using our nanohole arrays is about the size of a credit card," continued Bai. "In the future, we hope to build detectors that use very simple light sources such as LEDs and simple detectors similar to smartphone cameras. These devices will have widespread applications across medical science and could even be used to detect contaminants in food, water or the air."

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