Effect of electron beam treatment in air on surface properties of ultra-high-molecular-weight polyethylene

In this study, ultra-high-molecular-weight polyethylene (UHMWPE) was treated by an electron beam (EB) in air to obtain polar hydroxyl and carbonyl functional groups, which originated from oxidizing agents, to improve hydrophobicity and cell adhesion (NCTC clone L929). Sample characterization using Fourier transform-infrared spectroscopy revealed the presence of carbonyl oxidation products, whose intensity and surface roughness increased with increasing irradiation dose. The substitution of polar groups into the surface layers of the polymers resulted in a decreased water contact angle. The observed differences in the water contact angle of untreated polymers relative to that of the treated samples can be attributed not only to the differences in their respective molecular composition but also to their distinct roughness values. The treatment conditions affected the adhesion characteristics of fibroblasts. The untreated polymer and the surfaces treated at 10.7 kGy maintained the adhesion, spreading, and proliferation of fibroblasts. The hydrophilic polymer treated at 46.5 and 106.5 kGy maintained only the initial adhesion of fibroblasts. Thus, this study shows that EB treatment is a useful tool for modifying the surface properties of UHMWPE for particular biomedical applications. For example, the initially hydrophobic surface of UHMWPE can be made either hydrophilic or moderately hydrophobic by varying the surface treatment procedure using EB.