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 (AlO) 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° to ∼97.3°), decrease the surface free energy (SFE, 23.20 to ∼20.85 mJ/m) and elicit enhanced adsorbed protein density (PD, from ∼0.26 to ∼0.32 mg/cm) 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 (σ), i.e., 0.967, whereas a decrease in cell density after 48 h is attributed to significant apatite mineralization and low dispersion fraction (σ) of CNT-AlO-UHMWPE biocomposites. Interestingly, gene expression studies have corroborated low osteogenic differentiation (i.e., weaker intensity osteopontin and β-actin) in 2-10 wt % f-CNT reinforced AlO-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-AlO-reinforced UHMWPE nanocomposites.