O content*

The interactions between biological samples and atmospheric pressure plasma sources are very complex and still not understood in detail. In general, these interactions are driven by reactive oxygen and nitrogen species (RONS), such as •OH, O₂⁻ and NO. A major factor affecting RONS is the gas mixture the plasma is formed in. To understand their influence on the chemical modifications of biological targets, the biomolecule Cysteine is used as simplified target and treated with Argon- and Helium-based plasmas with varying H₂O and O₂ content. As plasma source, we use a well-characterized dielectric barrier discharge at atmospheric pressure in a chamber to control the exact operating conditions. The Cysteine samples are analysed by FTIR spectroscopy. With increasing molecular admixture, several molecular structures in the Cysteine molecule change in intensity and new structures are produced. The decrease in signal intensity of hydrogen containing groups is directly associated to an intensity increase of the corresponding oxygen containing groups. To provide insights into the underlying mechanisms, plasma parameters (e.g. gas temperature and UV flux) are measured by optical emission spectroscopy.