Attachment of Human Primary Osteoblast Cells to Modified Polyethylene Surfaces

Abstract

Ultra-high-molecular-weight polyethylene (UHMWPE) has a long history of use in medical devices, primarily for articulating surfaces due to its inherent low surface energy which limits tissue integration. To widen the applications of UHMWPE, the surface energy can be increased. The increase in surface energy would improve the adsorption of proteins and attachment of cells to allow tissue integration, thereby allowing UHMWPE to potentially be used for a wider range of implants. The attachment and function of human primary osteoblast-like (HOB) cells to surfaces of UHMWPE with various levels of incorporated surface oxygen have been investigated. The surface modification of the UHMWPE was produced by exposure to a UV/ozone treatment. The resulting surface chemistry was studied using X-ray photoelectron spectroscopy (XPS), and the topography and surface structure were probed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), which showed an increase in surface oxygen from 11 to 26 atom % with no significant change to the surface topography. The absolute root mean square roughness of both untreated and UV/ozone-treated surfaces was within 350-450 nm, and the water contact angles decreased with increasing oxygen incorporation, i.e., showing an increase in surface hydrophilicity. Cell attachment and functionality were assessed over a 21 day period for each cell-surface combination studied; these were performed using SEM and the alamarBlue assay to study cell attachment and proliferation and energy-dispersive X-ray (EDX) analysis to confirm extracellular mineral deposits, and total protein assay to examine the intra- and extracellular protein expressed by the cells. HOB cells cultured for 21 days on the modified UHMWPE surfaces with 19 and 26 atom % oxygen incorporated showed significantly higher cell densities compared to cells cultured on tissue culture polystyrene (TCPS) from day 3 onward. This indicated that the cells attached and proliferated more readily on the UV/ozone-treated UHMWPE surfaces than on untreated UHMWPE and TCPS surfaces. Contact guidance of the cells was observed on the UHMWPE surfaces by both SEM and AFM. Scanning electron micrographs showed that the cells were confluent on the modified UHMWPE surfaces by day 10, which led to visible layering of the cells by day 21, an indicator of nodule formation. In vitro mineralization of the extracellular matrix expressed by the HOB cells on the modified UHMWPE surfaces was confirmed by SEM and EDX analysis; spherulite structures were observed near cell protrusions by day 21. EDX analysis confirmed the spherulites to contain calcium and phosphorus, the major constituents in calcium phosphate apatite, the mineral phase of bone. Overall cell attachment, functionality, and mineralization were found to be enhanced on the UV/ozone-modified UHMWPE surfaces, demonstrating the importance of optimizing the surface chemistry for primary HOB cells.

In vitro and in vivo evaluation of a novel nanosize hydroxyapatite particles/poly(ester-urethane) composite scaffold for bone tissue engineering

“…addition increased the surface oxygen with a more significant and pronounced effect of the filler, the alkoxy concentration increase being the most significant. This is an important finding, because high surface oxygen has been shown to improve the attachment and the proliferation of osteoblast-like cells on biomaterials [24], which may be beneficial for bone tissue engineering. Interestingly, we found in vitro that nHA/PU scaffolds adsorbed significantly more proteins on their surface than control scaffolds.…”

Adsorption of tripeptide RGD on rutile TiO2 nanotopography surface in aqueous solution

“…Increasing the surface energy improves the adsorption of proteins and attachment of cells to allow the integration of tissues [11]. A surface with higher surface energy promotes the adhesion and spreading of cells [12,13].…”

Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria

“…Various surface treatments/modifications have been extensively examined to control the adhesion and growth characteristics of cells on surfaces [1][2][3][4], a matter of prime importance, for instance, for tissue engineering [5]. Understanding the relationship between cells and the physico-chemical properties of surfaces with which they interact (such as wettability, functional groups, topography) is, in fact, essential for the optimisation of cell adhesion, their spreading, and growth thereon [1].…”

“…Improved cellular attachment [3] is promoted by certain functional groups, which at the same time increase hydrophilicity, favouring the adsorption or adhesion of proteins [6]. For example, surface modifications with UV/O 3 [1] or with plasmas such as corona discharges [2] can increase proliferation and protein expression of cells or enhance their culture process. Similar action can be obtained with coatings with well-defined surface chemistries as they can also amplify, or prevent, bioadhesion of molecules, cells and, in some cases, bacteria [7][8][9][10].…”

“…Other authors showed that surfaces could also be modified chemically (e.g. thiocyanation) by turning to various gas plasmas (Ar, O 2 ) [17,18], with O 3 [19], with vacuum ultra-violet (VUV) irradiation in the presence of O 2 and with UV/O 3 exposure [2,20] before grafting the antiseptic or other active species [21]. These modified surfaces exhibit antimicrobial effectiveness on a broad spectrum of Gram-positive and Gram-negative bacteria and in some case viruses and fungi [21,13,17].…”