Title: Plasma injection system: Reaching beyond the surface in plasma medicine applications
Funder: Engineering and Physical Sciences Research Council

Abstract: Plasma, the fourth state of matter, provides a unique means for creating reactive environments at low gas temperature useful for many scientific and technological applications. For example more than half the steps required to fabricate a modern chip require plasma. Other well established multi-million applications include the lighting and the flat panel display industries. While most established technologies utilize low pressure plasmas, in recent years there has been a growing interest on developing plasmas that can be operated at atmospheric pressure and yet remain at low temperature. In particular, low temperature atmospheric pressure plasmas have made possible the treatment of biological materials that are temperature sensitive and cannot be put in vacuum environments, given birth to a fast growing scientific discipline referred to as Plasma medicine . Plasma medicine studies the interaction of gas plasmas and living cells and is being considered for a wide range of biomedical applications including sterilization of medical equipment, wound disinfection, wound healing, cancer treatment, oral/dental care, and food safety. As in any emerging technology, initial efforts have been focused in demonstrating the potential of plasmas to either kill, modify or stimulate living cells. This has been largely done in in-vitro studies where often monolayers of targeted cells are treated by plasma. Having been demonstrated the capability of plasma to modify biomolecules and the interact with potential therapeutic value with living cells, it is now time for the field to address other fundamental questions. Arguably the main two issues that plasma medicine needs to address before plasmas become widely accepted by the biomedical community are (1) selectivity, in other words, can plasma damage malignant cells while sparing healthy ones; and (2) penetration, can plasma reach underneath the surface to infer its therapeutic value. In this feasibility study we focus on the latter issue: penetration. Given the non-equilibrium character of the chemistry developed in plasmas, their action is typically limited to the surface. While this is ideal for surface modification applications where we want to preserve the properties of the bulk material, most envisaged biomedical applications require plasma treatments to reach beyond the first monolayer of cells. Although plasma treatment penetration has not been studied in detail in the past, the literature has indirect evidence that suggest that plasma treatments weaken in tens of microns. For example, the bactericidal properties of plasmas rapidly decay if cells are embedded in a biofilm or even simply stacked one on another. Addressing this potential technology killer, the proposed work undertakes the development of a plasma injection system where a combination of a plasma jet and a needle-free liquid injector are operated synergistically to enable the penetration of plasmas species inside a biological target. Taking a heuristic approach aimed at demonstrating the feasibility of the plasma injection system, we will examine the bactericidal properties of a He/O2/water plasma injection system against bacteria protected by gels acting as biological barriers. The project will include an initial characterization of the system although detailed analysis aimed at unravelling the underlying physico-chemical processes are envisaged in follow-up studies.


Research activity codes: 5.1 PHARMACEUTICALS
Health categories: INFECTION