ESCA investigation of low-temperature ammonia plasma-treated polyethylene substrate for immobilization of protein

A low-temperature radiofrequency plasma excited in anhydrous ammonia was used to modify polyethylene substrate surfaces for covalent immobilization of proteins. Electron spectroscopy for chemical application (ESCA) was used for surface characterization of polyethylene to a depth scale of 7 nm. The data revealed that surface modification is extensive and occurs in seconds at low discharge power. Primary amino functionalities were detected on the polyethylene surface and the level is dependent on plasma parameters. 125I-labelled antibodies covalently attached to amino groups via glutaraldehyde allowed the conditions for optimum level of primary amine to be established. Both ESCA data and protein loadings are in excellent agreement.