Harmful microbes and toxic micromolecules in food and drinking water can cause serious health problems around the world. For her PhD thesis, VTT researcher Sanna Uusitalo has developed a disposable optical test substrate for use in microbial detection. The aim is to enable cost-effective detection of harmful microbes and toxins.

Uusitalo developed the optical detection of microbial cells using Raman spectroscopy to increase measurement sensitivity via SERS (surface-enhanced Raman scattering) amplification. SERS measurement is based on Raman scattering, whose intensity is increased by the oscillation of free electrons in metal. In some cases, the method can identify a sample to a precision-level of one molecule. The disposable SERS measuring substrate is patterned using a roll-to-roll production method and coating the substrate with thin gold plating. "The more sensitive the SERS process becomes in the case of challenging cell measurements, the more applications it will have in the future. It would provide a fast and simple method of microbial identification compared to traditional cell cultures and enable the fast identification of microbes in cases, say, of food poisoning, or rapid purity analysis in food industry production facilities," says Uusitalo.

She believes that the first general application of the method will be in explosives detection or the analysis of environmental toxins. Portable Raman measuring devices are already on the market for the analysis of larger sample volumes. Future R&D will also lead to portable SERS measuring devices for measuring very low sample volumes.

Uusitalo's doctoral thesis, "Detection of small molecules and microbial cells by surface-enhanced Raman spectroscopy using roll-to-roll produced substrates," which focuses on Raman spectroscopy, will be examined at 12 noon on 24 November at the University of Oulu.