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A layer-by-layer deposition technique with grafting chitosan on the Co-Cr-Mo alloy was developed. The performance of tribology and biocompatibility were investigated under simulated conditions. Wettability of coating surface was super hydrophilic and the surface was in positive charge under the neutral solution, which was favored in water-based lubricating and adhesion of cells. By pin-on-disk tests, the chitosan coating surface exhibited lower friction coefficient under various sliding speed as compared with the uncoated substratum. A wear rate of 1.1 × 10 −7 mm 3 /Nm was detected, which was only one seventh of uncoated surfaces. Hypothetically illuminating the mechanism of antifriction is able to lead for better wear resistance. Co-culturing with osteoblast cells showed that coating had good benefits in the proliferation of osteoblast cells. [ABSTRACT FROM AUTHOR]

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co–Cr–Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co–Cr–Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co–Cr–Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants. [ABSTRACT FROM AUTHOR]

Using the layer-by-layer deposition method, functional chitosan/casein phospopeptides (CS/CPP) composite coatings were produced on Co–Cr–Mo alloy. The CS/CPP composite coatings had the dendritic topography, and were quite hydrophilic. Zeta potential measurements showed the composite coatings were negative charged at neural pH. XPS results indicated that the CS/CPP composite coatings were covalently bond to the substrate. When MC3T3-E1 cells were seeded on the CS/CPP composite coatings, no cytotoxicity was observed. The bone morphogenetic protein-2 (BMP-2) mRNA expression was significantly up-regulated in MC3T3-E1 cells cultured on the composite coatings and it was twice as much as that of cells cultured on the bare substrate. The expression of osteoprotegerin (OPG) mRNA and the ratio of OPG/receptor activator of nuclear factor-κB ligand (RNAKL) mRNA were increased 5-fold and 55-fold, respectively. These results suggested the CS/CPP composite coatings may have potential application in cobalt matrix orthopaedic implants. [ABSTRACT FROM AUTHOR]

Abstract: Surface wettability behaviors of three kinds of laser textured Co–Cr–Mo alloy surfaces (arrays of circular, triangular and square shape dimples) were evaluated in aqueous bovine serum albumin (BSA) solution. The tribological properties of laser textured Co–Cr–Mo alloy were investigated by pin–on–disc reciprocating tribometer under BSA lubrication. The wetting surfaces ranging from superhydrophilic (CA=21.5°) to superhydrophobic (CA=142.2°) were obtained by dual/combined surface modification including laser surface texturing (LST) and further fluoro-alkyl silane (FAS). It was found that surface wettability behaviors of Co–Cr–Mo alloy surfaces were closely related to their tribological behaviors in BSA solution. Results showed that the contact angle of circular dimple was the most stable, sliding time of the friction pair reaching steady state stage was shortest and coefficient of friction was minimum among three regular layout shapes of dimples during the tribological tests. It suggests that the combined surface modification of LST and FAS is a promising method to improve the tribological performances and prolong the service life of Co–Cr–Mo orthopedic implants. [Copyright &y& Elsevier]