In situ FTIR spectroscopy study on biomolecular etching by atmospheric pressure plasma jets

Abstract

The evaluation of biomolecular etching by non-thermal plasmas is of great significance for surface decontamination but remains a big challenge. In this work, the atmospheric pressure plasma jets etching profiles of over 40 kinds of biological materials were systematically probed by in situ Fourier transform infrared spectroscopy. The infrared spectra were recorded in real time during the plasma exposure processes with the sensitivity of ∼µg. Etching rather than chemical modifications dominated the spectral variations. Results showed that short-carbon-chain or hydroxyl-containing amino acids had much higher etching rates (ERs). Almost all tested proteins shared close ERs, which were higher than those of nucleic acids, peptidoglycan, phospholipid, and serum. Difficultly etched component significantly hindered the overall etching of mixtures. This investigation provides new hints for bacterial or organic contamination removal by plasmas.

Surface decontamination by atmospheric pressure plasma jet: key biological processes

“…This band is attributed to the symmetric stretching vibration of C=O in carboxylate groups (denoted as v s (COO − )), the rising of which under plasma exposure has been reported [24]. Overall, for both bacteria, the decreasing of bands dominates the spectral variations rather than modifications, which is the typical spectral characteristic induced by plasma etching and has been reported by our previous study regarding the etching of biomolecules such as proteins, nucleic acids, and lipids, etc by the same APPJ device [34].…”

“…The experimental setup has been described elsewhere [34]. As shown in figure 1, the plasma jet was obtained by applying a 4 kVp and 2 kHz sinusoidal voltage to a 1.2 mm outer-diameter stainless steel needle using argon as the inlet gas with a flow rate of 0.2 standard liters per minute (SLM).…”

“…By this way, the baseline of the spectra can be thoroughly subtracted. Then the processed data were analyzed on MATLAB 2020a (MathWorks) [34]. According to our pretest, flowing argon alone has neglected influence on the spectra, and thus the spectral variations are due to the plasma treatment.…”

“…As a result, the amide region in 1600-1700 cm −1 is used to calculate the etching rate due to the higher signalto-noise ratio compared to the other two regions. Similar to the etching of DNA and peptidoglycan, [34] the reduction of amide region area is best fitted by the weighted exponential function (y = a 1 + a 2 × e −t/a3 ). The R 2 value is 0.860 ± 0.220 (mean ± std) for E. coli and 0.9974 ± 0.0003 for S. albus, while a 1 is 0.940 ± 0.070 and 0.887 ± 0.003, respectively.…”

“…In our previous studies, Fourier transform infrared (FTIR) spectroscopy has been applied to characterize the chemical modifications or structural changes of proteins or bacteria in liquid environments induced by DBD plasma [31][32][33]. And the etching characteristics of various biological materials induced by APPJ have been investigated by in situ FTIR [34]. Compared to other biomedical techniques, FTIR has the advantage of being non-invasive and applicable to all bacterial constituents.…”