Chemical properties and protein adsorptions on ozone/UV-treated poly(ethylene terephthalate) film surfaces

We have studied on chemical properties of poly(ethylene terephthalate) (PET) film surfaces treated by ozone aeration under UV light irradiation (ozone/UV treatment) in distilled water and in an aqueous ammonia solution, and on adsorption behavior of bovine serum albumin (BSA), fibrinogen (FBG), and γ globulin (BGG) on the treated PET film. Attenuated total-reflection FT-IR and X-ray photoelectron spectroscopy surface analysis indicate that the ozone/UV treatment in distilled water causes ring opening of benzene rings of PET molecular chains, introducing hydroxy and carbonyl groups on the treated PET film, and that the treatment in the ammonia solution also induces benzene ring opening, followed by deposition not only of hydroxy and carbonyl groups but also of amino and amide groups. The surface free energy evaluated from the contact angle of ultrapure water and diiodomethane on the PET film is enhanced by the ozone/UV treatment, because of the increment of polar force by the polar functional group. The adsorption of BSA and FBG having negative surface charges is lower on the PET film treated in distilled water than on the untreated film, and their adsorption on the film treated in the ammonia solution reaches the maximum, as treatment time increases. On the contrary, the adsorption of BGG, of which the surface charge is almost neutral, on the PET film remains constant during the ozone/UV treatment. We therefore consider that the ozone/UV treatment is more effective for the BSA and FBG adsorption on the PET film, but not for the BGG adsorption.