Carbon Nanotube Functionalization Decreases Osteogenic Differentiation in Aluminum Oxide Reinforced Ultrahigh Molecular Weight Polyethylene

Ultrahigh molecular weight polyethylene (UHMWPE) is one of the most preferred materials as an acetabular cup-liner for bone implant applications. The current work develops a correlation between wettability, protein adsorption with osteogenic differentiation upon reinforcement of functionalized carbon nanotube (f-CNT) and 10 wt % aluminum oxide (Al2O3) in compression molded UHMWPE composites. Phase characterization has confirmed the retention of CNTs after compression molding. The loading of 2 wt % f-CNT in UHMWPE has shown to increase the contact angle (CA, from 88.9 degrees to similar to-97.3 degrees), decrease the surface free energy (SFE, 23.20 to similar to 20.85 mJ/m(2)) and elicit enhanced adsorbed protein density (PD, from similar to 0.26 to similar to 0.32 mg/cm(2)) in comparison to that of virgin polymer. Similar trend also has observed with 5 and 10 wt % f-CNT reinforcement. Initially, a high density of L929 mouse fibroblast cells is observed for 10 wt % unfunctionalized CNT (u-CNT) loading (48 h of incubation) with high values of dispersion fraction of surface free energy (sigma(d)), i.e., 0.967, whereas a decrease in cell density after 48 h is attributed to significant apatite mineralization and low dispersion fraction (cd) of CNT-Al2O3-UHMWPE biocomposites. Interestingly, gene expression studies have corroborated low osteogenic differentiation (i.e., weaker intensity osteopontin and beta-actin) in 2-10 wt % f-CNT reinforced Al2O3-UHMWPE biocomposites in comparison to that of similar wt % reinforcement of u-CNT. Thus, implant material can be engineered, (bulk or surface-modified), possessing osteoanalogous and cytocompatible properties based on f-CNT-Al2O3-reinforced UHMWPE nanocomposites.