Dr. Anna-Liisa Välimaa Profile

Dr. Anna-Liisa Välimaa

Research Scientist at Natural Resources Institute Finland (Luke)

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Publications (2)

Proceedings Article | 4 March 2019 Presentation

Surface-enhanced Raman spectroscopy for beverage spoilage yeasts and bacteria detection with patterned substrates and gold nanoparticles (Conference Presentation)

Sanna Uusitalo, Martin Kögler, Alexey Popov, Yury Ryabchikov, Olga Bibikova, Hanna-Leena Alakomi, Riikka Juvonen, Ville Kontturi, Samuli Siitonen, Anna-Liisa Välimaa, Riitta Laitinen, Anton Popov, Gleb Tselikov, Ahmed Al-Kattan, Peter Neubauer, Andrei Kabashin, Igor Meglinski, Jussi Hiltunen, Arja Laitila

Proceedings Volume 10907, 1090703 (2019) https://doi.org/10.1117/12.2513956

KEYWORDS: Yeast, Nanoparticles, Surface enhanced Raman spectroscopy, Gold, Chemical analysis, Molecules, Chemometrics, Biological research, Spherical lenses, Signal detection

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In food industry, detection of spoilage yeasts such as W. anomalus and B. bruxellensis and pathogens such as certain Listeria and E. coli species can be laborious and time-consuming. In the present study, a simple and repeatable technique was developed for rapid yeast detection using a combination of patterned gold coated polymer SERS substrates and gold nanoparticles [1−4]. For the first time, a state-of-the-art time-gated Raman detection approach was used as a complementary technique to show the possibility of using 532-nm pulsed laser excitation and avoid the destructive influence of induced fluorescence [3]. Conventional nanoparticles synthesized by colloidal chemistry are typically contaminated by non-biocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. Here, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and Au Si hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection [3]. We demonstrate successful identification of two types of bacteria (L. innocua and E. coli) and yeast (W. anomalus and B. bruxellensis). They showed several differing characteristic peaks making the discrimination of these yeasts possible without the need for chemometric analysis [2]. The use of composite gold-silicon laser-ablated nanoparticles in combination with the SERS substrate gave distinctive spectra for all the detected species. The detection limit of the studied species varied within 104-107 CFU/ml. The obtained results open up opportunities for non-disturbing investigation of biological systems by profiting from excellent non-disturbing nature of laser-synthesized nanomaterials in combination with outstanding optical detection technologies [2, 3]. [1] Uusitalo et al. 2016, http://pubs.rsc.org/en/content/articlehtml/2016/ra/c6ra08313g [2] Uusitalo et al. 2017a, https://www.sciencedirect.com/science/article/pii/S0260877417302054 [3] Kögler et al. 2018, https://onlinelibrary.wiley.com/doi/abs/10.1002/jbio.201700225 [4] Uusitalo et al. 2017b, https://www.spiedigitallibrary.org/journalArticle/Download?fullDOI=10.1117/1.OE.56.3.037102

SPIE Journal Paper | 7 March 2017

Stability optimization of microbial surface-enhanced Raman spectroscopy detection with immunomagnetic separation beads

Sanna Uusitalo, Martin Kögler, Anna-Liisa Välimaa, Jarno Petäjä, Ville Kontturi, Samuli Siitonen, Riitta Laitinen, Matti Kinnunen, Tapani Viitala, Jussi Hiltunen

OE, Vol. 56, Issue 03, 037102, (March 2017) https://doi.org/10.1117/12.10.1117/1.OE.56.3.037102

KEYWORDS: Surface enhanced Raman spectroscopy, Signal detection, Raman spectroscopy, Bacteria, Gold, Neodymium, Biological research, Nanoparticles, Magnetism, Microorganisms

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