Abstract
High-density polyethylene (PE) foils were modified by an Ar+ plasma discharge and subsequent grafting with biomolecules, namely glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C) or BSA and C (BSA + C). As revealed by atomic force microscopy (AFM), goniometry and Rutherford Backscattering Spectroscopy (RBS), the surface chemical structure and surface morphology of PE changed dramatically after plasma treatment. The contact angle decreased for the samples treated by plasma, mainly in relation to the formation of oxygen structures during plasma irradiation. A further decrease in the contact angle was obvious after glycine and PEG grafting. The increase in oxygen concentration after glycine and PEG grafting proved that the two molecules were chemically linked to the plasma-activated surface. Plasma treatment led to ablation of the PE surface layer, thus the surface morphology was changed and the surface roughness was increased. The materials were then seeded with vascular smooth muscle cells (VSMC) derived from rat aorta and incubated in a DMEM medium with fetal bovine serum. Generally, the cells adhered and grew better on modified rather than on unmodified PE samples. Immunofluorescence showed that focal adhesion plaques containing talin, vinculin and paxillin were most apparent in cells on PE grafted with PEG or BSA + C, and the fibres containing α-actin, β-actin or SM1 and SM2 myosins were thicker, more numerous and more brightly stained in the cells on all modified PE samples than on pristine PE. An enzyme-linked immunosorbent assay (ELISA) revealed increased concentrations of focal adhesion proteins talin and vinculin and also a cytoskeletal protein β-actin in cells on PE modified with BSA + C. A contractile protein α-actin was increased in cells on PE grafted with PEG or Gly. These results showed that PE activated with plasma and subsequently grafted with bioactive molecules and colloidal C particles, especially with PEG and BSA + C, promotes the adhesion, proliferation and phenotypic maturation of VSMC.
Highlights
Synthetic polymers, such as polyethylene, polystyrene, polyurethane, polytetrafluoroethylene and polyethyleneterephthalate, are commonly used in various industrial applications, as well as in biotechnology and medicine
The results of this study proved that grafting PE with biomolecules, such as glycine, PEG, bovine serum albumin (BSA) and/or carbon particles, can create surfaces which are suitable for the adhesion and growth of vascular smooth muscle cells (VSMC)
In accordance with the data obtained on the cell number and the cell spreading area, immunofluorescence staining revealed that focal adhesion plaques containing talin, vinculin and paxillin were generally better developed in cells on modified PE samples, those grafted with PEG and BSA + C, than in cells on pristine PE samples (Figure 8)
Summary
Synthetic polymers, such as polyethylene, polystyrene, polyurethane, polytetrafluoroethylene and polyethyleneterephthalate, are commonly used in various industrial applications, as well as in biotechnology and medicine. These modifications change the stability, roughness, morphology, mechanical properties and chemical composition of the polymer surface by creating chemical functional groups containing oxygen or nitrogen, e.g., carbonyl, carboxyl or amine groups, on the surface of the material These groups increase the surface wettability, support the adsorption of cell adhesion-mediating extracellular matrix proteins in an appropriate geometrical conformation and stimulate cell adhesion and growth [1,2,3,7]. In this study, high-density polyethylene, a model material for potential biomedical use, was modified by an Ar+ plasma discharge and subsequent grafting of glycine (Gly), bovine serum albumin (BSA), polyethyleneglycol (PEG), colloidal carbon particles (C) or BSA + C The aim of these modifications was to create surfaces attractive for cell colonization. We evaluated the adhesion, proliferation and phenotypic maturation of vascular smooth muscle cells in cultures derived from rat aorta
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