Surface decontamination by atmospheric pressure plasma jet: key biological processes

In this work, surface decontamination of bacteria by argon atmospheric-pressure plasma jet was systematically studied. The chemical modifications and etching characteristics of Gram-positive and Gram-negative bacteria under direct plasma jet exposure were inspected by in-situ Fourier transform infrared spectroscopy. Etching rather than chemical modifications dominates the infrared spectral variations. The etching rate of bacteria is comparable to the cell wall constituents. By using the green fluorescence protein-expressing Escherichia coli, it is found that cellular envelope destruction by plasma etching is the main cause of bacterial inactivation. The tailing phenomenon of the survival curve is more pronounced when the initial bacterial density is higher than ∼1 × 10⁷ CFU cm⁻², indicating the limited penetration depth of reactive species into bacterial deposits. Finally, three dominant biological processes key to surface decontamination were put forward according to our results.