Dr. Tobias Keplinger Profile

Dr. Tobias Keplinger

Group Leader at ETH Zürich

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Publications (2)

SPIE Journal Paper | 29 November 2018 Open Access

Effect of short-term formaldehyde fixation on Raman spectral parameters of bone quality

Imke A. Fiedler, Michele Casanova, Tobias Keplinger, Björn Busse, Ralph Müller

JBO, Vol. 23, Issue 11, 116504, (November 2018) https://doi.org/10.1117/12.10.1117/1.JBO.23.11.116504

KEYWORDS: Bone, Raman spectroscopy, Collagen, Tissues, Crystals, Minerals, Statistical analysis, Time metrology, Proteins, Carbonates

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Medical knowledge of the skeleton including its structures has improved constantly over the past decades. Advanced imaging methods, mechanical testing and optical techniques have revealed insights into bone architecture and composition. Most of these advancements were possible due to the ex vivo investigation of biological tissues. Investigations of fresh tissue are generally preferred over preserved or fixed samples. However, chemical fixation is sometimes inevitable due to histological procedures or logistical reasons. The aim of this study was to investigate whether short-term chemical fixation with formaldehyde affects bone quality parameters obtained from Raman spectroscopy and if these effects last for intermediate sample storage of several hours. As formaldehyde induces cross-links to the organic components in bone tissue, we hypothesized that collagen-related parameters are particularly affected. Femurs of eight 17-week-old C57BL/6 mice were extracted and divided into two groups (N = 8 / group). Samples of the first group were fixed by immersion in 4% formaldehyde (PFA-solution) for 12 h at 4°C (fixed group) while samples of the second group were left untreated (unfixed group). Raman spectroscopy was performed, and repeated after 4 h, to assess whether intermediate storage time influenced the obtained results. Based on resultant spectra, mineral-to-matrix ratio, carbonate-to-phosphate ratio, carbonate-to-amide I ratio, mineral crystallinity and collagen maturity were determined. Carbonate-to-phosphate ratio was the only parameter showing a significant difference between the first and the subsequent measurements. For both groups, ratios showed a decrease in carbonate substitution compared to the first measurement (percentage decrease: 3.1% in fixed, 4.7% in unfixed). Collagen maturity of samples, which were short-term fixed with formaldehyde, was significantly lower than of fresh, unfixed samples (percentage difference: 3.8%). Our study shows that Raman spectroscopy is able to detect changes in collagen structure initiated by formaldehyde and that changes in short-term fixed samples are minimally influencing bone material properties measured with Raman spectroscopy.

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Proceedings Article | 27 March 2018 Paper

Versatile strategies for the development of wood-based functional materials

Tobias Keplinger, Marion Frey, Ingo Burgert

Proceedings Volume 10593, 1059313 (2018) https://doi.org/10.1117/12.2296537

KEYWORDS: Polymers, Composites, Polymerization, Raman spectroscopy, Materials science, Manufacturing, Imaging spectroscopy, Chemical analysis

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