Water/O₂-Plasma-Assisted Treatment of PCL Membranes for Biosignal Immobilization

Abstract

The main purpose of this study was to obtain COOH functionalities on the surface of poly-epsilon-caprolactone (PCL) membranes using low-pressure water/O-2-plasma-assisted treatment. PCL membranes were prepared using the solvent-casting technique. Then, low-pressure water/O-2 plasma treatments were performed in a cylindrical, capacitively coupled RF-plasma-reactor in three steps: H2O/O-2-plasma treatment; in situ (oxalyl chloride vapors) gas/solid reaction to convert -OH functionalities into -COCl groups; and hydrolysis for final -COOH functionalities. Optimization of plasma modification processes was done using the DoE software program. COOH and OH functionalities on modified surfaces were detected quantitatively using the fluorescent labeling technique and an UVX 300G sensor. Chemical structural information of untreated, plasma treated and oxalyl chloride functionalized PCL membranes were acquired using pyrolysis GC/MS and ESCA analysis. High-resolution AFM images revealed that nanopatterns were more affected than micropatterns by plasma treatments. AFM images recorded with amino-functionalized tips presented increased size of the features on the surface that suggests higher density of the carboxyls on the nanotopographical elements. Low-pressure water/O-2-plasma-treated and oxalyl chloride functionalized samples were biologically activated with insulin and/or heparin biosignal molecules using a PEO (polyoxyethylene bis amine) spacer. The success of the immobilization process was checked qualitatively by ESCA analysis. In addition, fluorescent labeling techniques were used for the quantitative determination of immobilized biomolecules. Cell-culture experiments indicated that biomolecule immobilization onto PCL scaffolds was effective on L929 cell adhesion and proliferation, especially in the presence of heparin. (C) Koninklijke Brill NV, Leiden, 2009