Atmospheric pressure plasma induced grafting of poly (ethylene glycol) onto silicone elastomers for controlling biological response

This study investigates the role that surface functionalisation of siliconeelastomer (SE) by atmosphericpressureplasmainduced graft immobilisation of poly(ethyleneglycol) methyl ether methacrylate (PEGMA) plays in the attendant biologicalresponse. SE is used in modern ophthalmic medical devices and samples of the material were initially plasma treated using a dielectric barrier discharge reactor (DBD) to introduce reactive oxygen functionalities, prior to in situgrafting of two molecular weights of PEGMA (MW 1000 Da: PEGMA1000, MW 2000 Da: PEGMA2000). The variously processed surfaces were characterised by water contact angle analysis, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and atomic force microscopy. Lens epithelial cells were then cultured on the PEGMA grafted SE surfaces. It was found that cells on the pristine surface were not well spread and had shrunken morphology. On the DBD pre-treated surfaces, the cells were well spread. On the PEGMA1000 surface, the cells displayed evidence of shrinkage and were on the verge of detaching. Remarkably, on the PEGMA2000 surface, no cell adhesion was detection. Bacterial adhesion to the surfaces was studied using Staphylococcus aureus NTC8325. There was no difference in the number of bacteria adhering to any of the surfaces studied.