AVS 56th International Symposium & Exhibition
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuP

Paper BI-TuP11
Plasma Polymerization Induced Structural Modification of PCL

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Biomaterial Interfaces Poster Session I
Presenter: A.M. Sandstrom, University of Queensland, Australia
Authors: A.M. Sandstrom, University of Queensland, Australia
L. Grøndahl, University of Queensland, Australia
J.J. Cooper-White, University of Queensland, Australia
Correspondent: Click to Email

Cellular response to tissue culture scaffolds is thought to be directed by chemical and topographical cues from surfaces which bind biological motifs recognized by cell receptors. Plasma polymerization (PP) is frequently used to functionalize surfaces for improved biocompatibility. It has been reported that the type and distribution of functional groups created on a surface is dependent on plasma parameters. However, in addition to changing chemistry, modification of plasma parameters is also likely to introduce topographical variation to the sample. The aim of this work was to elucidate the combined effects of plasma power and treatment time on the surface chemistry and topographical features of the substrate.

Scaffolds [5% poly(ε-caprolactone) (PCL)/1,4-dioxane] were prepared using thermally induced phase separation. Samples were plasma polymerized in a custom-built radio frequency reactor using heptylamine (HA) at 20W and 50W for 30s and 60s. Additional substrates were prepared by spincoating PCL on Si wafers. For each of the four treatment conditions, surface homogeneity was confirmed across the wafers and scaffold sections via XPS. Surface topography was investigated on wafers by AFM, and scaffolds were examined using SEM.

Disappearance of the PCL carboxyl (C=O) peak following PP for all treatment conditions suggests complete coverage (>10nm) of the top surface of all substrates by PPHA. The N/C ratio was slightly higher on the Si wafer than the scaffold. Treatment was homogenous across individual samples. Slight chemical functionality shifts were found between samples, which may reflect intrinsic plasma differences or post-PP oxidative variation.

Polymer aggregates formed on Si following PPHA treatment at 20W, but were diminished at 50W. Topographical changes were more pronounced on PPHA PCL-coated Si. Although spherulite size variation was minimal between untreated semi-crystalline PCL and PPHA PCL on Si for most treatments, complete recrystallization of the base polymer was observed at 50W 60s. Change in surface roughness was evidenced by disappearance of well-defined fibrous domains as treatment power and time increase for all samples, except at 50W 60s when distinct spherulites re-emerged.

Highly reactive HA recombination led to aggregate size reduction on Si, whereas PPHA on PCL appeared to affect structural organization of the substrate. Scaffold morphology also changed following PPHA, as more energetically favored fibrous extensions in the porous region of the surface were observed by SEM. These results may be used in conjunction with cellular studies to tune PPHA reactions on scaffolds as required for support of various cell types.