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Graphical abstract Abstract Although laboratory tests and mid-term clinical outcomes show the clinical safety and remarkable wear resistance of the highly cross-linked polyethylene (HXLPE) acetabular liner with a nanometer-scaled graft layer of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), the wear resistance of the layer under severe abrasive conditions is concerning. We evaluated the effects of a roughened femoral head and the grafting locus on the wear resistance of the PMPC-grafted HXLPE liner and the effect of PMPC grafting on wear resistance of the HXLPE substrate by removing the PMPC-grafted layer using a severely roughened femoral head. Against a moderately roughened femoral head, the PMPC-grafted HXLPE liner showed negative wear, although an untreated HXLPE liner increased the wear by 154.1% compared with wear against a polished femoral head, confirming that PMPC grafts were unaffected. Against a severely roughened femoral head, the PMPC-grafted layer of the head contact area might be removed under severe conditions. However, the wear rate was reduced by 52.5% compared to that of untreated HXLPE liners. Moreover, the head non-contact area-modified PMPC-grafted HXLPE liner against a polished femoral head reduced the wear by 76.8% compared with untreated HXLPE liner; thus, this area may be also important in the development of fluid-film lubrication. Statement of significance Here we describe effects of a roughened femoral head and the locus of grafting on the wear-resistance of the phospholipid polymer grafted highly cross-linked polyethylene (PMPC-HXLPE) liner. Against a moderately roughened femoral head, the PMPC-HXLPE liner showed negative wear, confirming that PMPC grafts were unaffected. After removing the PMPC layer of the head contact area using a severely roughened femoral head, the wear rate not only exceeded that of untreated HXLPE liners, but was reduced by 52.5%, confirming that PMPC grafting does not affect the wear-resistance of the HXLPE substrate. In addition, the head non-contact area-modified PMPC-HXLPE liner reduced the wear by 76.8%. Thus, this area may also may be important in the development of fluid-film lubrication. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract To overcome clinical issues caused by large bone defects and subsequent nonunion, various approaches to bone regeneration have been researched, including tissue engineering, biomaterials, stem cells and drug screening. Previously, we developed a free-standing biodegradable polymer nanosheet composed of poly(L-lactic acid) (PLLA) using a simple fabrication process consisting of spin-coating and peeling techniques. We reported that sandwich-type PLLA nanosheets loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2) displayed long-lasting, sustained release of rhBMP-2, and markedly enhanced bone regeneration in mouse calvarial bone defects. Here, we fabricated multi-layered nanosheets loaded with fibroblast growth factor-2 (FGF-2), and investigated their application for long bone regeneration. Subcutaneously implanted tri-layered PLLA nanosheets displayed sustained release of loaded rhFGF-2 for about 2 weeks. Next, we prepared critical-sized mouse femoral defects and implanted mono- or tri-layered nanosheets, or a gelatin hydrogel with rhFGF-2. Amongst these conditions, the tri-layered nanosheet most efficiently induced bone regeneration. Indeed, bone regeneration was enhanced even after 4 weeks in the tri-layered nanosheet group, and was accompanied by FGFR1 activation and subsequent osteoblast differentiation. Multi-layered PLLA nanosheets loaded with rhFGF-2 may be useful for bone regenerative medicine. Furthermore, the multi-layered PLLA nanosheet structure may potentially be applied as a potent sustained-release carrier. Statements of Significance Here, we describe multi-layered poly(L-lactic acid) (PLLA) nanosheets loaded with recombinant human fibroblast growth factor-2 (rhFGF-2) as a modified sustained-release carrier for bone regeneration. In vivo imaging system analysis revealed that subcutaneously implanted tri-layered PLLA nanosheets displayed sustained release of loaded rhFGF-2 for 2 weeks. In critical-sized mouse femoral defects, tri-layered nanosheets loaded with rhFGF-2 most efficiently induced bone regeneration. Notably, bone regeneration was enhanced even after 4 weeks in the tri-layered nanosheet group, and was accompanied by FGFR1 activation and subsequent osteoblast differentiation. Multi-layered PLLA nanosheets loaded with rhFGF-2 may be useful for bone regenerative medicine. Furthermore, the multi-layered PLLA nanosheet structure may potentially be applied as a potent sustained-release carrier. [ABSTRACT FROM AUTHOR]

Manipulating the surface and substrate of cross-linked polyethylene (CLPE) is an essential approach for obtaining life-long orthopedic bearings. We therefore proposed a bearing material comprised of an antioxidative substrate generated by vitamin E blending (HD-CLPE[VE]) with a poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-grafted surface, and investigated its wear resistance and oxidative stability under accelerated aging and load bearing conditions. Neither the hydration nor friction kinetics of the molecular network structure of the PMPC-grafted surface or the HD-CLPE(VE) substrate were influenced by accelerated aging but rather exhibited high stability even under high oxidation conditions. The characteristics of the PMPC-grafted surface improved the wear and impact fatigue resistance of the HD-CLPE(VE) liner regardless of accelerated aging. Notably, the PMPC-grafted surface was found to affect the potential oxidative stability at the rim part of the acetabular liner. PMPC chains serve several important functions on the surface regardless of load bearing, such as high lubricity or low lipophilicity attributed to phosphorylcholine groups and/or surrounding water-fluid film, and suppression of lipid diffusion attributed to methacrylate main chains on the surface. Together, these results provide preliminary evidence that the PMPC graft layer and vitamin E-blended substrate might positively affect the extent of orthopedic implant durability. [ABSTRACT FROM AUTHOR]

Background: We evaluated the clinical and radiographic outcomes, including femoral head penetration, of total hip arthroplasty performed using a specific polyethylene (PE) liner in small Asian patients at 10 years after the index surgery. In addition, we investigated whether femoral head penetration was affected by patient-related, implant-related, and surgical factors.Methods: Between August 2002 and June 2005, for cementless primary total hip arthroplasty, we used acetabular PE liners that were manufactured from GUR 1050 resin, machined from isostatic compression-molded bar stock, and sterilized with a gamma ray irradiation in argon gas. We assessed 82 hips in 78 patients who received these liners.Results: The mean Harris hip score improved from 41.0 preoperatively to 84.5 at 10 years postoperatively. Periprosthetic osteolysis was observed in 7 hips (9.8%). No acetabular component migration was detected, and no revision surgery was performed 10 years postoperatively. The mean steady-state wear rate was 0.031 mm/y, which was lower than the wear rate for other conventional PE liners of the previous studies. Among the patient-related, implant-related, and surgical factors, sex was significantly associated with the mean steady-state wear rate, with a higher rate in male patients than in female patients.Conclusion: PE acetabular liners used in small Asian patients show similar clinical outcomes and reduced wear compared with those of other liners. In addition, sex is significantly associated with the mean steady-state wear rate, and the steady-state wear rate is higher in male patients than in female patients. [ABSTRACT FROM AUTHOR]

To overcome serious clinical problems caused by large bone defects, various approaches to bone regeneration have been researched, including tissue engineering, biomaterials, stem cells and drug screening. Previously, we developed a free-standing biodegradable polymer nanosheet composed of poly(L-lactic acid) (PLLA) using a simple fabrication process consisting of spin-coating and peeling techniques. Here, we loaded recombinant human bone morphogenetic protein-2 (rhBMP-2) between two 60-nm-thick PLLA nanosheets, and investigated these sandwich-type nanosheets in bone regeneration applications. The PLLA nanosheets displayed constant and sustained release of the loaded rhBMP-2 for over 2 months in vitro . Moreover, we implanted the sandwich-type nanosheets with or without rhBMP-2 into critical-sized defects in mouse calvariae. Bone regeneration was evident 4 weeks after implantation, and the size and robustness of the regenerated bone had increased by 8 weeks after implantation in mice implanted with the rhBMP-2-loaded nanosheets, whereas no significant bone formation occurred over a period of 20 weeks in mice implanted with blank nanosheets. The PLLA nanosheets loaded with rhBMP-2 may be useful in bone regenerative medicine; furthermore, the sandwich-type PLLA nanosheet structure may potentially be applied as a potent prolonged sustained-release carrier of other molecules or drugs. Statements of Significance Here we describe sandwich-type poly( L -lactic acid) (PLLA) nanosheets loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2) as a novel method for bone regeneration. Biodegradable 60-nm-thick PLLA nanosheets display strong adhesion without any adhesive agent. The sandwich-type PLLA nanosheets displayed constant and sustained release of the loaded rhBMP-2 for over 2 months in vitro . The nanosheets with rhBMP-2 markedly enhanced bone regeneration when they were implanted into critical-sized defects in mouse calvariae. In addition to their application for bone regeneration, PLLA nanosheets may be useful for various purposes in combination with various drugs or molecules, because they displays excellent capacity as a sustained-release carrier. [ABSTRACT FROM AUTHOR]

The surface and substrate of a cross-linked polyethylene (CLPE) liner are designed to achieve resistance against oxidative degradation in the construction of hip joint replacements. In this study, we aimed to evaluate the oxidative degradation caused by lipid absorption of a highly hydrophilic nanometer-scaled thickness layer prepared by grafting a poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer and a high-dose gamma-ray irradiated CLPE with vitamin E blending (HD-CLPE[VE]). The HD-CLPE(VE) and PMPC-grafted HD-CLPE(VE) exhibited extremely high oxidation resistance regardless of lipid absorption, even though residual-free radical levels were detectable. The water wettability of the PMPC-grafted CLPE and PMPC-grafted HD-CLPE(VE) surfaces was considerably greater than that of untreated surfaces. The hydrated PMPC-grafted layer also exhibited extremely low solubility for squalene. Lipids such as squalene and cholesterol esters diminished the oxidation resistance of CLPE despite the vitamin E improvement. Notably, the PMPC-grafted surface was resistant to lipid absorption and diffusion as well as subsequent lipid-related oxidative degradation, likely because of the presence of the hydrated PMPC-grafted layer. Together, these results provide preliminary evidence that the resistance against lipid absorption and diffusion of a hydrated PMPC-grafted layer might positively affect the extent of resistance to the in vivo oxidation of orthopedic implants. [ABSTRACT FROM AUTHOR]

In the construction of artificial hip joint replacements, the surface and substrate of a cross-linked polyethylene (CLPE) liner are designed to achieve high wear resistance and prevent infection by bacteria. In this study, we fabricated a highly hydrophilic and antibiofouling poly(2-methacryloyloxyethyl phosphorylcholine [MPC]) (PMPC)-graft layer on the vitamin E-blended CLPE (HD-CLPE(VE)) surface. The 100-nm-thick, smooth, and electrically neutral PMPC layer was successfully fabricated on the HD-CLPE(VE) surface using photoinduced graft polymerization. The PMPC-grafted HD-CLPE(VE) was found to prevent bacterial adherence and biofilm formation on the surface because of the formation of a highly hydrophilic polyzwitterionic layer on the surface of HD-CLPE(VE), which can serve as an extremely efficient antibiofouling layer. The number of bacterial adhered on the PMPC-grafted HD-CLPE(VE) surface was reduced by 100-fold or more by PMPC grafting, regardless of the biofilm-production characteristics of the strains. In contrast, vitamin E blending did not affect bacterial adhesion. Moreover, the number of planktonic bacteria did not differ significantly, regardless of PMPC grafting and vitamin E blending. In conclusion, the PMPC-grafted HD-CLPE(VE) provided bacteriostatic effects associated with smooth, highly hydrophilic surfaces with a neutral electrostatic charge owing to the zwitterionic structure of the MPC unit. Thus, this modification may prove useful for the production of artificial hip joint replacement materials. Statement of Significance Our preliminary in vitro findings suggest that improved bacteriostatic performance of the HD-CLPE(VE) surface in orthopedic implants is possible via PMPC grafting. The results also indicate that surface modifications affect the anti-infection properties of the orthopedic implants and demonstrate that the application of a PMPC-grafted HD-CLPE(VE) surface may be a promising approach to extend the longevity and clinical outcomes of total hip arthroplasty. Further research is needed to evaluate the resistance to infection of PMPC-grafted HD-CLPE(VE) in terms of the varieties of biofilm formation tests including fluid flow conditions and animal experiments, which may offer useful clues to the possible performance of these materials in vivo . [ABSTRACT FROM AUTHOR]

In this study, we aimed to determine whether the outcomes of total hip arthroplasty (THA) after rotational acetabular osteotomy (RAO) are equal to those of primary THA, and to elucidate the characteristics of THA after RAO. The clinical and radiographic findings of THA after RAO (44 hips), with minimum 24 months of follow-up, were compared with a matched control group of 58 hips without prior RAO. We found that the outcomes in terms of functional scores and complication rates did not differ between THA after RAO and THA without previous pelvic osteotomy, indicating that the results of THA after RAO are equivalent to those of primary THA. Although THA after RAO requires technical considerations, similar clinical outcomes to primary THA can be expected. [ABSTRACT FROM AUTHOR]

Abstract: The ultimate goal in manipulating the surface and substrate of a cross-linked polyethylene (CLPE) liner is to obtain not only high wear resistance but also high oxidative stability and high-mechanical properties for life-long orthopedic bearings. We have demonstrated the fabrication of highly hydrophilic and lubricious poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) grafting layer onto the antioxidant vitamin E-blended CLPE (HD-CLPE(VE)) surface. The PMPC grafting layer with a thickness of 100 nm was successfully fabricated on the vitamin E-blended CLPE surface by using photoinduced-radical graft polymerization. Since PMPC has a highly hydrophilic nature, the water wettability and lubricity of the PMPC-grafted CLPE and HD-CLPE(VE) surfaces were greater than that of the untreated CLPE surface. The PMPC grafting contributed significantly to wear reduction in a hip-joint simulator wear test. Despite high-dose gamma-ray irradiation for cross-linking and further UV irradiation for PMPC grafting, the substrate modified by vitamin E blending maintained high-oxidative stability because vitamin E is an extremely efficient radical scavenger. Furthermore, the mechanical properties of the substrate remained almost unchanged even after PMPC grafting or vitamin E blending, or both PMPC grafting and vitamin E blending. In conclusion, the PMPC-grafted HD-CLPE(VE) provided simultaneously high-wear resistance, oxidative stability, and mechanical properties. [Copyright &y& Elsevier]

Abstract: Despite improvements in the techniques, materials, and fixation of total hip arthroplasty, periprosthetic osteolysis, a complication that arises from this clinical procedure and causes aseptic loosening, is considered to be a major clinical problem associated with total hip arthroplasty. With the objective of reducing the production of wear particles and eliminating periprosthetic osteolysis, we prepared a novel hip polyethylene (PE) liner whose surface graft was made of a biocompatible phospholipid polymer—poly(2-methacryloyloxyethyl phosphorylcholine (MPC)). This study investigated the wear resistance of the poly(MPC)-grafted cross-linked PE (CLPE; MPC-CLPE) liner during 15×106 cycles of loading in a hip joint simulator. The gravimetric analysis showed that the wear of the acetabular liner was dramatically suppressed in the MPC-CLPE liner, as compared to that in the non-treated CLPE liner. Analyses of the MPC-CLPE liner surface revealed that it suffered from no or very little wear even after the simulator test, whereas the CLPE liners suffered from substantial wears. The scanning electron microscope (SEM) analysis of the wear particles isolated from the lubricants showed that poly(MPC) grafting dramatically decreased the total number, area, and volume of the wear particles. However, there was no significant difference in the particle size distributions, and, in particular, from the SEM image, it was observed that particles with diameters less than 0.50μm were present in the range of the highest frequency. In addition, there were no significant differences in the particle size descriptors and particle shape descriptors. The results obtained in this study show that poly(MPC) grafting markedly reduces the production of wear particles from CLPE liners, without affecting the size of the particles. These results suggest that poly(MPC) grafting is a promising technique for increasing the longevity of artificial hip joints. [Copyright &y& Elsevier]

Abstract: We investigated the production of free radicals on a poly(ether-ether-ketone) (PEEK) substrate under ultraviolet (UV) irradiation. The amount of the ketyl radicals produced from the benzophenone (BP) units in the PEEK molecular structure initially increased rapidly and then became almost constant. Our observations revealed that the BP units in PEEK acted as photoinitiators, and that it was possible to use them to control the graft polymerization of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). This “self-initiated surface graft polymerization” method is very convenient in the absence of external photoinitiator. We also investigated the effects of the monomer concentration and UV irradiation time on the extent of the grafted PMPC layer. Furthermore, as an application to improving the durability of artificial hips, we demonstrated the nanometer-scale photoinduced grafting of PMPC onto PEEK and carbon fiber-reinforced PEEK (CFR-PEEK) orthopedic bearing surfaces and interfaces. A variety of test revealed significant improvements in the water wettability, frictional properties, and wear resistance of the surfaces and interfaces. [Copyright &y& Elsevier]

Abstract: Natural joints rely on fluid thin-film lubrication by the hydrated polyelectrolyte layer of cartilage. However, current artificial joints with polyethylene (PE) surfaces have considerably less efficient lubrication and thus much greater wear, leading to osteolysis and aseptic loosening. This is considered a common factor limiting prosthetic longevity in total hip arthroplasty (THA). However, such wear could be mitigated by surface modification to mimic the role of cartilage. Here we report the development of nanometer-scale hydrophilic layers with varying charge (nonionic, cationic, anionic, or zwitterionic) on cross-linked PE (CLPE) surfaces, which could fully mimic the hydrophilicity and lubricity of the natural joint surface. We present evidence to support two lubrication mechanisms: the primary mechanism is due to the high level of hydration in the grafted layer, where water molecules act as very efficient lubricants; and the secondary mechanism is repulsion of protein molecules and positively charged inorganic ions by the grafted polyelectrolyte layer. Thus, such nanometer-scaled hydrophilic polymers or polyelectrolyte layers on the CLPE surface of acetabular cup bearings could confer high durability to THA prosthetics. [Copyright &y& Elsevier]

Abstract: Preventing peritendinous adhesions after surgical repair of tendon is difficult. In order to establish an ideal anti-adhesion material, we prepared a spontaneously forming hydrogel by mixing the aqueous solutions of two polymers, poly(MPC-co-methacrylic acid) (PMA) and amphiphilic poly(MPC-co-n-butyl methacrylate) (PMB), in the presence of Fe3+. This PMA/PMB/Fe3+ hydrogel (MPC polymer hydrogel) had a honeycomb microstructure with nanometer-scale pores, which resist cell invasion but allow the passage of cytokines and growth factors for tendon healing. The dissociation rate of the hydrogel could be controlled by changing Fe3+ concentration, and by examining the viscoelasticity of the hydrogel, we determined the optimal Fe3+ concentration to be 0.05 m. We then examined the effects of the in situ application of this MPC polymer hydrogel containing 0.05 m Fe3+ by using two animal models: the rat Achilles tendon model and the chicken flexor digitorum profundus tendon model. In both models, macroscopic and histological observation revealed that peritendinous adhesions were significantly decreased by the hydrogel application. Mechanical analyses revealed that the hydrogel prevented peritendinous adhesions but did not affect the tendon healing. Because of its characteristic microstructure and excellent biocompatibility, we believe that the MPC polymer hydrogel will be ideal for preventing peritendinous adhesions. [Copyright &y& Elsevier]

Abstract: Poly(ether-ether-ketone) (PEEK)s are a group of polymeric biomaterials with excellent mechanical properties and chemical stability. In the present study, we demonstrate the fabrication of an antibiofouling and highly hydrophilic high-density nanometer-scaled layer on the surface of PEEK by photo-induced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) without using any photo-initiators, i.e., “self-initiated surface graft polymerization.” Our results indicated that the diphenylketone moiety in the polymer backbone acted as a photo-initiator similar to benzophenone. The density and thickness of the poly(MPC) (PMPC)-grafted layer were controlled by the photo-irradiation time and monomer concentration during polymerization, respectively. Since MPC is a highly hydrophilic compound, the water wettability (contact angle <10°) and lubricity (coefficient of dynamic friction <0.01) of the PMPC-grafted PEEK surface were considerably lower than those of the untreated PEEK surface (90° and 0.20, respectively) due to the formation of a PMPC nanometer-scale layer. In addition, the amount (0.05μg/cm2) of BSA adsorbed on the PMPC-grafted PEEK surface was considerably lower, that is more than 90% reduction, compared to that (0.55μg/cm2) for untreated PEEK. This photo-induced polymerization process occurs only on the surface of the PEEK substrate; therefore, the desirable mechanical properties of PEEK would be maintained irrespective of the treatment used. [Copyright &y& Elsevier]

Abstract: Migration of the artificial femoral head to the inside of the pelvis due to the degeneration of acetabular cartilage has emerged as a serious issue in resurfacing or bipolar hemi-arthroplasty. Surface modification of cobalt–chromium–molybdenum alloy (Co–Cr–Mo) is one of the promising means of improving lubrication for preventing the migration of the artificial femoral head. In this study, we systematically investigated the surface properties, such as lubricity, biocompatibility, and stability of the various modification layers formed on the Co–Cr–Mo with the biocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer by dip coating or grafting. The cartilage/poly(MPC) (PMPC)-grafted Co–Cr–Mo interface, which mimicked a natural joint, showed an extremely low friction coefficient of <0.01, as low as that of a natural cartilage interface. Moreover, the long-term stability in water was confirmed for the PMPC-grafted layer; no hydrolysis of the siloxane bond was observed throughout soaking in phosphate-buffered saline for 12 weeks. The PMPC-grafted Co–Cr–Mo femoral head for hemi-arthroplasty is a promising option for preserving acetabular cartilage and extending the duration before total hip arthroplasty. [Copyright &y& Elsevier]

Abstract: Aseptic loosening of artificial hip joints induced by wear particles from the polyethylene (PE) liner remains the ruinous problem limiting their longevity. We reported here that grafting with a polymer, poly(2-methacryloyloxyethyl phosphorylcholine (MPC)) (PMPC), on the PE liner surface dramatically decreased the wear production under a hip joint simulator condition. We examined that the effect of properties of both PE by cross-linking and femoral head by changing the materials on wearing properties of PE. The PMPC grafting on the liners increased hydrophilicity and decreased friction torque, regardless of the cross-linking of the PE liner or the difference in the femoral head materials. During the hip joint simulator experiments (5×106 cycles of loading), cross-linking caused a decrease of wear amount and a reduction of the particle size, while the femoral head materials did not affect it. The PMPC grafting abrogated the wear production, confirmed by almost no wear of the liner surface, independently of the liner cross-linking or the femoral head material. We concluded that the PMPC grafting on the PE liner surpasses the liner cross-linking or the change of femoral head materials for extending longevity of artificial hip joints. [Copyright &y& Elsevier]

Summary: The study aimed to determine the status of disease management activities that patients under conservative treatment actually performed and to examine the relevant factors in performing or not performing the activities. A survey was conducted with hip OA patients of the orthopaedic outpatient service of one university hospital in Japan. Results indicated that it is necessary to advise patients at an earlier stage of the disease to perform the management activities and to develop a program to link the advice to actual performance of the activities. [Copyright &y& Elsevier]

The wear resistance of cross-linked polyethylene grafted with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC-grafted CLPE) and unmodified CLPE loaded by an alumina roller were evaluated in a simulated synovial fluid (0.5 wt% hyaluronate solution containing 30 vol% fetal bovine serum). To evaluate the wear depth distribution within the wear scar, we compared the projected area of wear and non-wear for indents on polyethylene surfaces produced by a triangular pyramidal indenter and estimated the local wear depths on the basis of the changes in the projected area. The worn depth of PMPC-grafted CLPE was almost a third lower than that on CLPE. [ABSTRACT FROM AUTHOR]

Abstract: Osteolysis caused by wear particles from polyethylene in artificial hip joints is of great concern. Various bearing couple combinations, bearing material improvements, and surface modifications have been attempted to reduce such wear particles. With the aim of reducing the wear and developing a novel artificial hip-joint system, we created a highly lubricious metal-bearing material: A 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was grafted onto the surface of the cobalt–chromium–molybdenum (Co–Cr–Mo) alloy. For ensuring the long-term retention of poly(MPC) on the Co–Cr–Mo alloy, we used a 4-methacryloxyethyl trimellitate anhydride (4-META) intermediate layer and photo-induced graft polymerization technique to create a strong bonding between the Co–Cr–Mo substrate and the poly(MPC) chain via the 4-META layer. The Co–Cr–Mo alloy was pretreated with nitric acid and O2 plasma to facilitate efficient interaction between the 4-META carboxyl group and the surface hydroxyl group on the Cr oxide passive layer of the Co–Cr–Mo alloy. After MPC grafting, the MPC unit peaks were clearly observed in the Fourier-transform infrared spectroscopy with attenuated total reflection (FT-IR/ATR) and X-ray photoelectron spectroscopy (XPS) spectra of the Co–Cr–Mo surface. Tribological studies with a pin-on-plate machine revealed that surface MPC grafting markedly lowered the friction coefficient. We concluded that the grafted poly(MPC) layer successfully provided high lubricity to the Co–Cr–Mo surface. [Copyright &y& Elsevier]

Abstract: The biomimetic synthetic phospholipid polymer containing a phosphorylcholine group, 2-methacryloyloxyethyl phosphorylcholine (MPC), has improved the surface property of biomaterials. Both hydrophilic and anti-biofouling surfaces were prepared on polydimethylsiloxane (PDMS) with MPC grafted by surface-initiated photo-induced radical polymerization. Benzophenone was used as the photoinitiator. The quantity of the adsorbed initiator on PDMS was determined by UV absorption and ellipsometry. The poly(MPC)-grafted PDMS surfaces were characterized by XPS, ATR-FTIR and static water contact angle (SCA) measurements. The SCA on PDMS decreased from 115° to 25° after the poly(MPC) grafting. The in vitro single protein adsorption on the poly(MPC)-grafted PDMS decreased 50–75% compared to the unmodified PDMS. The surface friction of the poly(MPC)-grafted PDMS was lower than the unmodified PDMS under wet conditions. The oxygen permeability of the poly(MPC)-grafted PDMS was as high as the unmodified PDMS. The tensile property of PDMS was maintained at about 90% of the ultimate stress and strain after the poly(MPC) grafting. The surface-modified PDMS is expected to be a novel medical elastomer which possesses an excellent surface hydrophilicity, anti-biofouling property, oxygen permeability and tensile property. [Copyright &y& Elsevier]