Human mesenchymal stem cell response to poly(ε-caprolactone/poly(methyl methacrylate) demixed thin films.

Advances in material sciences have enabled the fabrication of biomaterials which are able to provide the requisite cues to stimulate cells to behave in a specific way. Nanoscale surface topographies are well known to be able to positively influence cell-substrate interactions. This study reports on a novel series of poly(ε-caprolactone) PCL and poly(methyl methacrylate) demixed nanotopographic films as non-biological cell-stimulating cues. The topographic features observed ranged from nanoislands to nanopits. PMMA was observed to segregate to the air interface, while PCL preferred the substrate interface. Preliminary response of human mesenchymal stem cells to these surfaces indicated that the substrate with nanoisland topography has the potential to differentiate to osteogenic, chondrogenic and adipogenic lineages.

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 silicone elastomer (SE) by atmospheric pressure plasma induced graft immobilisation of poly(ethylene glycol) methyl ether methacrylate (PEGMA) plays in the attendant biological response. 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 situ grafting of two molecular weights of PEGMA (MW 1000 Da: PEGMA(1000), MW 2000 Da: PEGMA(2000)). 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 PEGMA(1000) surface, the cells displayed evidence of shrinkage and were on the verge of detaching. Remarkably, on the PEGMA(2000) 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.

Lens epithelial cell response to atmospheric pressure plasma modified poly(methylmethacrylate) surfaces.

Selective control of cellular response to polymeric biomaterials is an important consideration for many ocular implant applications. In particular, there is often a need to have one surface of an ophthalmic implant capable of promoting cell attachment while the other needs to be resistant to this effect. In this study, an atmospheric pressure dielectric barrier discharge (DBD) has been used to modify the surface region of poly(methyl methacrylate) (PMMA), a well established ocular biomaterial, with the aim of promoting a controlled response to human lens epithelial cells (LEC) cultured thereon. The DBD plasma discharge environment has also been employed to chemically graft a layer of poly(ethylene glycol) methyl ether methacrylate (PEGMA) onto the PMMA and the response to LEC likewise determined. Two different molecular weights of PEGMA, namely 1000 and 2000 MW were used in these experiments. The LEC response to DBD treated polystyrene (PS) samples has also been examined as a positive control and to help to further elucidate the nature of the modified surfaces. The LEC adhered and proliferated readily on the DBD treated PMMA and PS surfaces when compared to the pristine polymer samples which showed little or no cell response. The PMMA and PS surfaces that had been DBD grafted with the PEGMA(1000) layer were found to have some adhered cells. However, on closer inspection, these cells were clearly on the verge of detaching. In the case of the PEGMA(2000) grafted surfaces no cells were observed indicating that the higher molecular weight PEGMA has been able to attain a surface conformation that is capable of resisting cell attachment in vitro.

Chemical grafting of poly(ethylene glycol) methyl ether methacrylate onto polymer surfaces by atmospheric pressure plasma processing.

This article reports the use of atmospheric pressure plasma processing to induce chemical grafting of poly(ethylene glycol) methyl ether methacrylate (PEGMA) onto polystyrene (PS) and poly(methyl methacrylate) (PMMA) surfaces with the aim of attaining an adlayer conformation which is resistant to protein adsorption. The plasma treatment was carried out using a dielectric barrier discharge (DBD) reactor with PEGMA of molecular weights (MW) 1000 and 2000, PEGMA(1000) and PEGMA(2000), being grafted in a two step procedure: (1) reactive groups are generated on the polymer surface followed by (2) radical addition reactions with the PEGMA. The surface chemistry, coherency, and topography of the resulting PEGMA grafted surfaces were characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM), respectively. The most coherently grafted PEGMA layers were observed for the 2000 MW PEGMA macromolecule, DBD processed at an energy dose of 105.0 J/cm(2) as indicated by ToF-SIMS images. The effect of the chemisorbed PEGMA layer on protein adsorption was assessed by evaluating the surface response to bovine serum albumin (BSA) using XPS. BSA was used as a model protein to determine the grafted macromolecular conformation of the PEGMA layer. Whereas the PEGMA(1000) surfaces showed some protein adsorption, the PEGMA(2000) surfaces appeared to absorb no measurable amount of protein, confirming the optimum surface conformation for a nonfouling surface.