The attachment of catalase and poly-l-lysine to plasma immersion ion implantation-treated polyethylene

Plasma immersion ion implantation (PIII) treatment of polyethylene increased the functional attachment of catalase and increased the retention of enzyme activity in comparison to untreated controls. The attached protein was not removed by SDS or NaOH, while that on the untreated surfaces was easily removed. Poly-l-lysine was found to attach in a similar way to the treated surface and could not be removed by NaOH, while it did not attach to the untreated surface. This indicates that a new binding mechanism, covalent in nature, is introduced by the plasma treatment. Surfaces treated with PIII maintained the catalase activity more effectively than surfaces plasma treated without PIII. The PIII-treated surface was hydrophilic compared to the untreated surface and retained its hydrophilic character better than surfaces subjected to a conventional plasma treatment process. The strong modification of a deeper region of the polymer than for conventional plasma treatments is believed to be responsible for both the enhanced hydrophilic character and for the increase in functional lifetime of the attached protein. The results show that PIII treatment of polymers increases their usefulness for protein microarrays.