The effect of increasing dosage of atmospheric dielectric barrier plasma discharge (DBD) on the surface chemistry and topography on electrically conductive electrospun PLCL/PANI biomaterials

Introduction
Plasma surface treatments such as DBD are routinely used to enhance cellular attachment and differentiation in tissue engineering. Electrically conductive polymers have become increasingly important as a method of promoting cellular response and monitoring real time cell culture in vitro. Here we investigate the effects of increasing DBD plasma processing on the surface physical and chemical properties of electrospun PLCL/PANi an electrically conductive polymer.

Methodology
Electrically conductive PLCL/PANi (4:1) composite polymer was manufactured from 10% w/w PLCL and 3mg/ml PANi in chloroform/DMF solvent. Polymers were electrospun at 12 cm distance
and 20kV to produce a randomly aligned 50μm disc. This was exposed to increasing dosages of DBD plasma under atmospheric conditions. After a 48-hour resting period the samples were characterised using wettability analysis, SEM, AFM, FTiR and XPS.

Results
Randomly aligned, electroconductive electrospun PLCL/PANi matrices 50μm of thickness, with an average fibre diameter of 1.75μm were manufactured. The effect of the increasing DBD treatment caused a dose dependant statistically significant enhancement in their wettability until the point where surface melting was observed. SEM revealed a dose dependant beneficial change in fibre morphology and topography at low DBD dosages up to 500w. However, higher
dosages above this caused polymer fibre fractures and surface melting changes to be observed. FTiR analysis following DBD plasma treatment showed no chemical changes to the bulk properties of the polymer. AFM showed alterations in the topography of the individual surface fibres. Chemical XPS analysis showed an increase in surface oxygenation in plasma treated samples a desirable quality in a cell culture biomaterial.

Conclusions
Electrically conductive polymers have many applications in tissue engineering. The problems associated with synthetic medical polymers are their inherent hydrophobicity and poor surface chemistry. The research presented here clearly shows that atmospheric DBD plasma treatment alters the surface topography to improve surface wettability. Despite DBD being a cold plasma technology thermal damage to the individual fibres was observed at higher DBD dosages. 500w DBD treatment is the optimal DBD dosage to surface modify electrospun PLCL/PANi matrices balancing the need for improved surface wettability against polymer thermal degradation.