On the use of imaging ellipsometry for the monitoring of protein removal by means of low-pressure inductively coupled plasma discharges

Summary form only given. Non-equilibrium plasma discharges have been recently proposed to be an effective tool for the removal of protein residues from the surfaces of medical instruments and devices. However, the knowledge regarding plasma-protein interactions is still relatively poor, which consequently represents a serious drawback for the validation of this technique as well as for the optimization of the treatment. This is, among other reasons, caused by the limitations of currently used techniques for the determination of the rates of protein removal during plasma treatment. The methods used are either restricted to a narrow range of substrate materials (e.g. in the cases of quartz crystal microbalance or surface plasmon resonance) or due to their high surface sensitivities (e.g. in the case of XPS or ToF-SIMS) the thickness of the deposit is limited to few tens of nm. The objective of this contribution is therefore to present an alternative method to evaluate the efficiency of protein removal. This technique is based on imaging ellipsometry, namely on the monitoring of the temporal evolution of a 2D representation of the values of the Delta and psi angles. As it will be shown this approach allows fast and semi-quantitative monitoring of the process and thus it enables to compare capabilities of plasma discharges sustained under different experimental conditions to remove protein coatings. This will be demonstrated on deposits of a model protein (bovine serum albumin) treated by low-pressure inductively coupled plasma discharges sustained in argon based mixtures. Moreover, the results are going to be compared with the results of other diagnostics techniques.