Use of polymers as wavenumber calibration standards in deep-UVRR

Aikaterini Pistiki; Oleg Ryabchykov; Thomas W Bocklitz; Petra Rösch; Jürgen Popp

doi:10.1016/j.saa.2022.122062

Use of polymers as wavenumber calibration standards in deep-UVRR

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Feb 15;287(Pt 2):122062. doi: 10.1016/j.saa.2022.122062. Epub 2022 Nov 2.

Authors

Aikaterini Pistiki¹, Oleg Ryabchykov², Thomas W Bocklitz², Petra Rösch³, Jürgen Popp⁴

Affiliations

¹ Leibniz Institute of Photonic Technology Jena, Albert-Einstein-Str. 9, 07745 Jena, Germany.
² Leibniz Institute of Photonic Technology Jena, Albert-Einstein-Str. 9, 07745 Jena, Germany; Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich Schiller University, Lessingstraße 10, 07743 Jena, Germany.
³ InfectoGnostics Research Campus Jena, Philosophenweg 7, 07743 Jena, Germany; Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich Schiller University, Lessingstraße 10, 07743 Jena, Germany. Electronic address: petra.roesch@uni-jena.de.
⁴ Leibniz Institute of Photonic Technology Jena, Albert-Einstein-Str. 9, 07745 Jena, Germany; InfectoGnostics Research Campus Jena, Philosophenweg 7, 07743 Jena, Germany; Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich Schiller University, Lessingstraße 10, 07743 Jena, Germany; Jena Biophotonics and Imaging Laboratory, Albert-Einstein-Str. 9, 07745 Jena, Germany; Center for Sepsis Control and Care, Jena University Hospital, Am Klinikum 1, 07747 Jena, Germany.

PMID: 36351311
DOI: 10.1016/j.saa.2022.122062

Abstract

Deep-UV resonance Raman spectroscopy (UVRR) allows the classification of bacterial species with high accuracy and is a promising tool to be developed for clinical application. For this attempt, the optimization of the wavenumber calibration is required to correct the overtime changes of the Raman setup. In the present study, different polymers were investigated as potential calibration agents. The ones with many sharp bands within the spectral range 400-1900 cm^-1 were selected and used for wavenumber calibration of bacterial spectra. Classification models were built using a training cross-validation dataset that was then evaluated with an independent test dataset obtained after 4 months. Without calibration, the training cross-validation dataset provided an accuracy for differentiation above 99 % that dropped to 51.2 % after test evaluation. Applying the test evaluation with PET and Teflon calibration allowed correct assignment of all spectra of Gram-positive isolates. Calibration with PS and PEI leads to misclassifications that could be overcome with majority voting. Concerning the very closely related and similar in genome and cell biochemistry Enterobacteriaceae species, all spectra of the training cross-validation dataset were correctly classified but were misclassified in test evaluation. These results show the importance of selecting the most suitable calibration agent in the classification of bacterial species and help in the optimization of the deep-UVRR technique.

Keywords: Bacterial species differentiation; Deep-UV resonance Raman spectroscopy; Polymers; Wavenumber calibration.

MeSH terms

Calibration
Polymers*
Reference Standards
Spectrum Analysis, Raman* / methods
Vibration

Substances

Polymers