Collagen immobilization on polyethylene terephthalate surface after helium plasma treatment

An attractive alternative to add new functionalities such as biocompatibility due to the micro- and nano-scaled modification of polymer surfaces is offered by plasma processing. Many vital processes of tissue repair and growth following injuries depend on the rate of adsorption and self-assembling of the collagen molecules at the interfaces. Consequently, besides the amount of protein, it is necessary to investigate the form in which the collagen molecules are organizing on the polymer surface. In this study, direct current (DC) helium plasma treatment was used in order to obtain poly(ethylene terephthalate) (PET) films with different amounts of collagen and different shapes of aggregates formed from the collagen molecules. The immobilization of collagen on PET surface was confirmed by XPS measurements, an increase of the nitrogen content by increasing the plasma exposure time being recorded. The SEM and AFM measurements revealed the presence of grains and dendrites of collagen formed on the polymer surface. At 15 min plasma treatment time, the polymer surface after collagen immobilization has a homogenous topography. Usually, one can find fibrils, coil or dendrimers of collagen formed in buffer solutions and immobilized on different polymer surfaces. On the other hand, in this particular configuration, the combination of DC plasma and helium gas as a PET functionalization tool is an original one. As the collagen is not covalently immobilized on the surfaces, it may interact with the cell culture medium proteins, part of the collagen might being replaced by other serum proteins.