Eur. Phys. J. D (2016) 70: 25
https://doi.org/10.1140/epjd/e2015-60446-3

Regular Article

A comparative study of biomolecule and polymer surface modifications by a surface microdischarge^*

¹ Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
² Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742, USA
³ Department of Chemical and Biomolecular Engineering, University of California, Berkeley 94720, USA

^a e-mail: Oehrlein@umd.edu

Received: 31 July 2015
Received in final form: 12 December 2015
Published online: 2 February 2016

Abstract

Cold atmospheric plasma (CAP) sources are attractive sources of reactive species with promising industrial and biomedical applications, but an understanding of underlying surface mechanisms is lacking. A kHz-powered surface microdischarge (SMD) operating with N₂/O₂ mixtures was used to study the biological deactivation of two immune-stimulating biomolecules: lipopolysaccharide (LPS) and peptidoglycan (PGN), found in bacteria such as Escherichia coli and Staphylococcus aureus, respectively. Model polymers were also studied to isolate specific functional groups. Changes in the surface chemistry were measured to understand which plasma-generated species and surface modifications are important for biological deactivation. The overall goal of this work is to determine which effects of CAP treatment are generic and which bonds are susceptible to attack. CAP treatment deactivated biomolecules, oxidized surfaces, and introduced surface bound NO₃. These effects can be controlled by the N₂ fraction in O₂ and applied voltage and vary among different target surfaces. The SMD was compared with an Ar/O₂/N₂-fed kHz-powered atmospheric pressure plasma jet and showed much higher surface modifications and surface chemistry tunability compared to the jet. Possible mechanisms are discussed and findings are compared with recent computational investigations. Our results demonstrate the importance of long-lived plasma-generated species and advance an atomistic understanding of CAP-surface interactions.