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SERS helps diagnose osteoarthritis

27 Oct 2005

Surface-Enhanced Raman Spectroscopy can potentially spot osteoarthritis before pains sets in, say US scientists.

Raman spectroscopy of blood could provide a way to detect the onset of detect Osteoarthritis (OA), before the symptoms start showing up, according to chemists from the University of Michigan, Ann Arbor, US.

In OA, the cartilage tissue lining the bone joints breaks down causing extreme discomfort as the two bones rub against each other. The failing cartilage leaks hyaluronic acid, a lubricant from the joint, thus elevating its levels in the bloodstream. The University of Michigan research is focused on using a new highly sensitive version of Raman spectroscopy to measure these concentration changes.

To date, the team has analysed samples of water and synovial fluid with varying amounts of commercial hyaluronic acid and obtained promising results. The next step is to test blood samples.

“Our objective is to develop a complementary technique for the early diagnosis (of OA) well before the pain sets in, so that people can take corrective action to mitigate its effects,” said Dr. Michael Morris, project leader from the University of Michigan. Currently X-Rays and other clinical tests have not proven to be entirely accurate in detecting early signs of OA.

According to the 2004 Arthritis Research Campaign, over 4 million people in the UK suffer from this incurable condition which causes severe pain and stiffness in the joints, especially the knee and hip.

In order to overcome the inherent inefficiencies associated with Raman spectroscopy, the team used a variant called surface-enhanced Raman Spectroscopy (SERS) in which the sample is placed on an array of tiny (nanoscale) structures made of gold or silver. The electronic effects generated at the junctions of the metal greatly enhance the efficiency of Raman scatter. For example, Mesophotonics, a UK developer of SERS substrates, says that Raman signals can be about one million times stronger (see related story).

The Michigan set-up consists of a microscope linked to a near-infrared (785 nm) laser source and a detection system comprising an optical spectrograph and CCD camera. A tiny drop of the sample to be tested is placed on a Klarite gold SERS substrate provided by Mesophotonics and mounted on the microscope stage. Light from the laser illuminates the specimen, and the resulting Raman spectra are captured by the detection system.

“We chose the Klarite SERS substrate from Mesophotonics because they are reproducible and the properties are the same from one to the next,” commented Morris. “The presence of a vendor who can make these substrates reproducible is a big step in developing practical applications with SERS.”

This research was presented at the SERS Faraday Discussion forum of the Royal Society of Chemistry held in London last month. More information on the project can be found on the project website.

A.L. Narayan is an electronics engineer and a writer for On Target Media a Singapore-based technology content provider.

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