Insight into the Molecule Impact of Critical-Sized UHMWPE-ALN Wear Particles on Cells by the Alginate-Encapsulated Cell Reactor.

Wear particles of ultra-high molecular weight polyethylene (UHMWPE) are inevitable during service as joint prosthesis, and particles ≤ 10 µm with critical size could cause serious osteolysis and aseptic loosening of joint prosthesis. The aim of this study is to adopt the alginate-encapsulated cell reactor to investigate the molecular impact of critical-sized wear particles of UHMWPE loaded with alendronate sodium (UHMWPE-ALN) on cells. Results showed that compared with UHMWPE wear particles, UHMWPE-ALN wear particles inhibited the proliferation of macrophages significantly after being co-cultured for 1, 4, 7, and 14 d. Furthermore, the released ALN promoted early apoptosis, suppressed the secretion of TNF-α and IL-6 of macrophages, and down-regulated relative gene expressions of TNF-α, IL-6, and IL-1ß and RANK. In addition, compared with UHMWPE wear particles, UHMWPE-ALN wear particles promoted the ALP activity of osteoblasts, down-regulated the gene expression of RANKL, and up-regulated gene expression of osteoprotegerin. There were mainly two approaches of the effects of critical-sized UHMWPE-ALN wear particles on cells, one of which was cytology and the other was cytokine signal pathway. The former mainly affected the proliferation and activity of macrophages and osteoblasts. The latter would inhibit osteoclasts via cytokine and RANKL/RANK signal pathway. Thus, UHMWPE-ALN had the potential application in clinics to treat osteolysis induced by wear particles.

[Mechanical Reinforcement Strategy of Calcium Phosphate Cements by Loading Polymers].

Calcium phosphate cement (CPC) is well known for the excellent bioactivity and biocompatibility, however, CPC has been used only for the repair of non-load bearing bone defects due to its brittle nature and low flexural strength. Polymer reinforced CPC has been considered as one of the most effective strategies for mechanical reinforcement. This paper summarizes various kinds of polymers loaded CPC:fiber reinforcement, microsphere reinforcement and dual setting cements. It is aimed to analyze the advantages, disadvantages and principles of the polymers reinforced CPC, and so as to lay a foundation for the further research of improving and manufacturing the CPC with ideal mechanical properties.

Study on critical-sized ultra-high molecular weight polyethylene wear particles loaded with alendronate sodium: in vitro release and cell response.

The aim of this study was to investigate the in vitro release and the effect of RAW 264.7 macrophages of critical-sized wear particles of ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), one of the most effective drugs to treat osteoporosis in clinic. The critical-sized UHMWPE-ALN 0.5 wt.% wear particles were prepared by vacuum gradient filtration combined with Pluronic F-68. In vitro release of ALN from critical-sized UHMWPE-ALN wear particles was investigated in phosphate buffered saline (PBS) at 37 °C with a shaker. Cell morphology, proliferation, lactate dehydrogenase (LDH) leakage and secretions of cytokines were evaluated after co-cultured with critical-sized UHMWPE-ALN wear particles in vitro. Results showed that ALN released from critical-sized UHMWPE-ALN wear particles included burst release and slow release in vitro. Macrophages would be chemotaxis and aggregated around the critical-sized UHMWPE-ALN or UHMWPE wear particle, which was phagocytosed with time. The proliferation of macrophages co-cultured with critical-sized UHMWPE-ALN wear particles was significantly decreased compared with that of critical-sized UHMWPE group. Meanwhile, the critical-sized UHMWPE-ALN wear particles significantly induced the LDH leakage of macrophages, which indicated the cell death. The death of macrophages induced by ALN was one of pathways to inhibit their proliferation. The secretions of cytokines (interleukin-6 and tumor necrosis factor-alpha) in critical-sized UHMWPE-ALN group were significantly lower than those in critical-sized UHMWPE group due to the released ALN. The present results suggested that UHMWPE-ALN had the potential application in clinic to treat osteolysis induced by wear particles.

High-scale yield of nano hydroxyapatite through combination of mechanical activation and chemical dispersion.

The aim of this study is to develop a simple, convenient and effective approach to synthesize nano-sized hydroxyapatite (nano-HA) at high-scale yield. Nano-HA was wet synthesized in the presence or absence of alendronate sodium (ALN), one of bisphosphonates for anti-osteoporotic. Then aged and washed nano-HA precipitate was directly treated by mechanical activation combined with the chemical dispersion of ALN to prevent the agglomeration of nano-HA. ALN acted not only as a chemical dispersant but also as an orthopedic drug. In vitro release showed that ALN was released slowly from nano-HA. Transmission electron microscopy (TEM) revealed that nano-HA with size less than 100 nm appeared as single particle after being treated by mechanical activation combined with the dispersion of ALN (AMA-HA and MA-HA). High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) confirmed that as-prepared nanoparticles were HA with low crystallinity and crystallite size. Fourier transform infrared spectroscopy (FTIR) indicated that the phosphonate groups in ALN were introduced to bond with the Ca2+ of HA to impede the growth of HA crystal. Zeta potential illustrated that the absolute value of surface negative charge of nano-HA increased significantly with the addition of ALN, which inhibited the agglomeration of nano-HA. The present approach makes it feasible to produce nano-HA at high-scale yield, which provide the possibility to construct bone graft.

[Application of Microspheres in Calcium Phosphate Cement System].

Calcium phosphate cement(CPC)has been widely used as bone fillers because of its excellent bioactivity and biocompatibility.Meanwhile,CPC is also an attractive candidate for the incorporation of drug or microspheres,because the preparing procedure avoids sintering and heating release.This paper summarizes the clinical applications of microspheres incorporated in CPC from the aspects of sustained drug release,accelerated degradation,porous structure and improved mechanical properties.The paper is aimed to analyze the methods and principles of microspheres loaded CPC,and so as to lay a foundation for the further research of improving and manufacturing the CPC with ideal properties.

Enhanced mechanic properties of calcium phosphate cements via mussel-inspired adhesive as bone substitute: Highlights of their interactions.

BACKGROUND: Inspired by natural bones, many organic components were added to Calcium Phosphate Cements (CPCs) to improve their mechanical strength. However, the strength of these composite CPCs is limited by the low strength of organic components itself and the weak interaction between organic components and CPCs. OBJECTIVE: Firstly, a composite CPC containing mussel-inspired adhesive, Poly-(Dopamine Methacrylamide-co-2-methoxy Ethylacrylate) (pDM) was developed. Secondly, the interactions between pDM and CPC and their effect on mechanical properties were investigated. METHODS: The interactions between pDM and CPC were performed by Nuclear Magnetic Resonance, Laser Raman, X-ray Photoelectron Spectroscopy, Fourier Transform-Infrared Spectroscopy and X-ray Diffraction Analysis. RESULTS: The toughness and compressive strength of pDM-CPC scaffold were both significantly enhanced, because of the enhanced interface binding strength among CPC and pDM due to their interaction and the improved mechanical strength of pDM owing to its self-oxidation cross-linking. The toughness of pDM-CPC scaffolds increased with the increased contents of pDM, while pDM-CPC scaffold containing 35 wt.% pDM had the highest compressive strength of all, which the latter was more than five times compared to that of CPC. CONCLUSION: The mechanically strong pDM-CPC scaffolds has potential application in bone regeneration as well as in craniofacial and orthopedic repair.

Enhanced proliferation and angiogenic phenotype of endothelial cells via negatively-charged alginate and chondroitin sulfate microsphere hydrogels.

Sodium alginate-based hydrogel was the one of the most used polymers for cell delivery. However, the adsorption of extracellular matrix and proteins was inhibited due to the formation of a hydrated surface layer of these hydrogels. In this study, a novel cell delivery system, negatively-charged alginate and chondroitin sulfate microsphere hydrogel (nCACSMH), was fabricated with excellent permeability and biocompatibility in the action of a high voltage direct-current electric field. Negative charge was introduced to the surface of nCACSMH to obtain the expanded network and enhanced permeability. Additionally, the increasing content of chondroitin sulfate in nCACSMH could give rise to the charge density and its asymmetric structure, thus the uneven, plicate and expanded surface of nCACSMH which was favorable to cell proliferation was developed. Moreover, chondroitin sulfate was released with the degradation of nCACSMH, which played a crucial role in maintaining the normal physiological functions of cells. Thus the proliferation of human umbilical vein endothelial cells (HUVECs) was further accelerated and the angiogenesis related genes expression in endothelial cells was continuously and dramatically up-regulated. After 4 d, the proliferation and viability of HUVECs were significantly improved, the cells were distributed evenly in nCACSMH. The novel nCACSMH has the potential to be used as cell delivery, three-dimensional (3D) cell cultures for cell therapy, 3D bioprinting, high-throughput screening for drugs, and disease model for regeneration and constructing of tissue engineering.

A novel alginate-encapsulated system to study biological response to critical-sized wear particles of UHMWPE loaded with alendronate sodium.

The aim of this study was to develop a novel alginate-encapsulated system (Alg beads) to investigate the cell response to critical-sized wear particles of ultra-high molecular weight polyethylene loaded with alendronate sodium (UHMWPE-ALN), one of the most effective drugs to treat bone resorption in clinic. The extrusion method was used to prepare Alg beads encapsulating rat calvarial osteoblasts (RCOs) and critical-sized UHMWPE-ALN wear particles with spherical morphology and uniform size. The morphology, permeability and stability of Alg beads were characterized. The proliferation, ALP activity, cell apoptosis and distribution of live/dead RCOs co-cultured with wear particles in Alg beads were evaluated. RCOs and critical-sized UHMWPE-ALN wear particles distributed evenly and contacted efficiently in Alg beads. Alg beads were both permeable to trypsin and BSA, while the smaller the molecular was, the larger the diffuse was. The proliferation of RCOs in Alg beads increased with time, which indicated that Alg beads provided suitable conditions for cell culture. The long-term stability of Alg beads indicated the possibility for the longer time of co-cultured cells with wear particles. Critical-sized UHMWPE-ALN and UHMWPE wear particles both inhibited the proliferation and differentiation of RCOs, and induced the apoptosis of RCOs encapsulated in Alg beads. However, these effects could be significantly alleviated by the ALN released from the critical-sized UHMWPE-ALN wear particles. The present results suggested that this novel-developed co-culture system was feasible to evaluate the cell response to critical-sized UHMWPE-ALN wear particles for a longer time.

Biological responses to M13 bacteriophage modified titanium surfaces in vitro.

Phage-based materials have showed great potential in tissue engineering application. However, it is unknown what inflammation response will happen to this kind of materials. This work is to explore the biological responses to M13 bacteriophage (phage) modified titanium surfaces in vitro from the aspects of their interaction with macrophages, osteoblasts and mineralization behavior. Pretreated Ti surface, Ti surfaces with noncrosslinked phage film (APP) and crosslinked phage film (APPG) were compared. Phage films could limit the macrophage adhesion and activity due to inducing adherent-cell apoptosis. The initial inflammatory activity (24h) caused by phage films was relatively high with more production of TNF-α, but in the later stage (7-10days) inflammatory response was reduced with lower TNF-α, IL-6 and higher IL-10. In addition, phage films improved osteoblast adhesion, differentiation, and hydroapatite (HA)-forming via a combination of topographical and biochemcial cues. The noncrosslinked phage film displayed the best immunomodulatory property, osteogenic activity and HA mineralization ability. This work provides better understanding of inflammatory and osteogenetic activity of phage-based materials and contributes to their future application in tissue engineering. STATEMENT OF SIGNIFICANCE: In vivo, the bone and immune cells share a common microenvironment, and are being affected by similar cytokines, signaling molecules, transcription factors and membrane receptors. Ideal implants should cause positive biological response, including adequate and appropriate inflammatory reaction, well-balanced bone formation and absorption. Phage-based materials have showed great potential in tissue engineering application. However, at present it is unknown what inflammation response will happen to this kind of materials. A good understanding of the immune response possibly induced by phage-based materials is needed. This work studied the osteoimmunomodulation property of phage films on titanium surface, involving inflammatory response, osteogenic activity and biomineralization ability. It provides more understanding of the phage-based materials and contributes to their future application in tissue engineering.

The synergistic effect of micro/nano-structured and Cu2+-doped hydroxyapatite particles to promote osteoblast viability and antibacterial activity.

Microstructure and chemical constitution are important factors affecting the biological activity of biomaterials. This study aimed to fabricate hydroxyapatite (HAp) particles with both micro/nanohybrid structure and Cu2+ doping to promote osteogenic differentiation and antibacterial property. In the presence of inositol hexakisphosphate (IP6), micro/nano-structured and Cu2+-doped HAp (HAp-IP6-Cu) microspheres were successfully fabricated via hydrothermal method. Morphological observation showed that HAp-IP6-Cu microspheres with a diameter of 3.1-4.1 µm were chrysanthemum-like and composed of nano-flakes approximately 50 nm in thickness. Compared with the HAp micro-rods or IP6 modified HAp (HAp-IP6) microspheres, HAp-IP6-Cu microspheres had a larger specific surface area, better hydrophilicity and stronger ability to adsorb bovine serum albumin. To evaluate the synergistic effects of micro/nanohybrid structure and Cu2+ on cell behavior, rat calvarial osteoblasts (RCOs) were cultured on HAp-IP6-Cu, HAp-IP6 and HAp layers as well as their extracts, respectively. Results demonstrated that HAp-IP6-Cu layer promoted the adhesion, proliferation and osteogenic differentiation of RCOs. The cells grew on HAp-IP6-Cu and HAp-IP6 layers exhibited greater spreading than those on HAp layer. In addition, quantitative test by the agar disk diffusion technique found that HAp-IP6-Cu microspheres were effectively against S taphylococcus aureus and E scherichia coli. These results demonstrated that HAp-IP6-Cu microspheres may be a potential candidate as a bioactive and anti-infective biomaterial for bone regeneration.

The mechanical and tribological properties of UHMWPE loaded ALN after mechanical activation for joint replacements.

Ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN) has tremendous potential as an orthopeadic biomaterial for joint replacements. However, poor mechanical and tribological properties of UHMWPE-ALN are still obstacle for further application. The purpose of this study was to investigate the effect and mechanism of mechanical activation on mechanical and tribological properties of 1wt% ALN-loaded UHMWPE (UHMWPE-ALN-ma). In this study, tensile test, small punch test and reciprocating sliding wear test were applied to characterize the mechanical and tribological properties of UHMWPE-ALN-ma. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize UHMWPE-ALN-ma. Tensile test and small punch test showed that Young׳s modulus, tensile strength and work-to-failure (WTF) of UHMWPE-ALN-ma increased significantly compared to those of UHMWPE-ALN. The friction coefficients and wear factors of UHMWPE-ALN-ma both decreased significantly compared to those of UHMWPE-ALN. Mechanical activation obviously reduced type 1 (void) and type 2 (the disconnected and dislocated machining marks) fusion defects of UHMWPE-ALN-ma, which were revealed by SEM images of freeze fracture surfaces after etching and lateral surfaces of specimens after extension to fracture, respectively. It was attributed to peeled-off layers and chain scission of molecular chains of UHMWPE particles after mechanical activation, which were revealed by SEM images and FTIR spectra of UHMWPE-ALN-ma and UHMWPE-ALN, respectively. Moreover, EDS spectra revealed the more homogeneous distribution of ALN in UHMWPE-ALN-ma compared to that of UHMWPE-ALN. The present results showed that mechanical activation was a potential strategy to improve mechanical and tribological properties of UHMWPE-ALN-ma as an orthopeadic biomaterial for joint replacements.

Self-assembled Biodegradable Nanoparticles and Polysaccharides as Biomimetic ECM Nanostructures for the Synergistic effect of RGD and BMP-2 on Bone Formation.

Producing biomimetic extracellular matrix (ECM) is an effective approach to improve biocompatibility of medical devices. In this study, biomimetic ECM nanostructures are constructed through layer-by-layer self-assembling positively charged chitosan (Chi), negatively charged oxidized sodium alginate (OAlg), and positively charged bovine serum albumin (BSA)-based nanoparticles. The BSA-based nanoparticles in the self-assembled films not only result in porous nanostructures similar to natural ECM, but also preserve the activity and realize the sustained release of Bone morphogenetic protein-2 (BMP-2). The results of bone marrow stem cells (BMSCs) culture demonstrate that the penta-peptide glycine-arginine-glycine-aspartate-serine (GRGDS) grafted Chi/OAlg films favor cell adhesion and proliferation. GRGDS and BMP-2 in biomimetic ECM nanostructures synergistically promote BMSC functions and new bone formation. The RGD and BMP incorporated biomimetic ECM coatings could be applied on a variety of biomedical devices to improve the bioactivity and biocompatibility.

Nanostructured Architectures by Assembling Polysaccharide-Coated BSA Nanoparticles for Biomedical Application.

Nanostructured architectures are produced on Ti surfaces by layer-by layer (LbL) self-assembling of polysaccharide-coated BSA nanoparticles (BNPs), which created cellular microenvironments mimicking natural extracellular matrix. The BMP-2 encapsulated BNPs are prepared by a desolvation method, and are further coated by chitosan (CHI) coatings to obtain positively charged NPs (CBNPs). Vancomycin (Van) encapsulated CBNPs are obtained by the same method and subsequently coated by oxidized alginate (OALG) to obtain negatively charged NPs (OCBNPs). The CBNPs and OCBNPs are assembled on Ti surfaces to construct nanostructured coatings via electrostatic and covalent interactions. The nanostructured architectures realize the sustained release of BMP-2 and Van for a long term. Bone marrow stromal cells (BMSCs) culture tests confirm that the bare nanostructured architectures intrinsically facilitate attachment, proliferation, and differentiation of cells, which is attributed to the nanoscale porous structures that are similar to the size of cellular filopodia. Incorporating BMP-2 into the nanostructured architectures significantly enhances osteogenetic differentiation of BMSCs, which reveals the synergistic effects of nanostructures and growth factors on cell activity. The antibacterial tests indicate that controlled release of Van has good antibacterial ability against Staphylococcus epidermidis, while not affecting the normal biological activity of BMSCs.

TEM study of calcium phosphate precipitation on HA/TCP ceramics.

This study focuses on phase identification of precipitation on bioactive calcium phosphate (BCP) surfaces in vitro and in vivo. The BCP used in this study consisted of 70 wt% hydroxyapatite (HA) and 30 wt% beta-tricalcium phosphate. Single crystalline precipitates of calcium phosphates on porous BCP bioceramics obtained after immersion in dynamic simulated body fluid (SBF) and after implantation in pig muscle were examined using electron diffraction in transmission electron microscope. The crystals formed in vitro in dynamic SBF were identified as octacalcium phosphate (OCP), instead of apatite. Most of the precipitated crystals in vivo samples had an HA structure; while OCP and dicalcium phosphate dihydrate were also identified. The evidence from single diffraction patterns indicates that apatite formation on bioactive ceramics is a complicated process, particularly in physiological environments where formation might include a transient stage of intermediate phases.

Effect of polydopamine on the biomimetic mineralization of mussel-inspired calcium phosphate cement in vitro.

Inspired by the excellent adhesive property of mussel adhesive protein, we added polydopamine (PDA) to calcium phosphate cement (PDA-CPC) to enhance its compressive strength previously. The mineralization and mechanism on PDA-CPC were investigated by soaking it in simulated body fluid in this study. The results indicated that PDA promoted the conversion of dicalcium phosphate dihydrate and α-tricalcium phosphate to hydroxyapatite (HA) in the early stage but inhibited this conversion subsequently. PDA promoted the rapid mineralization on PDA-CPC to form a layer of nanoscale calcium phosphate (CaP) whereas there was no CaP formation on the control-CPC after 1d of soaking. This layer of nanoscale CaP was similar to that of natural bone, which was always observed during soaking. X-ray photoelectron spectroscopy showed that the peak of CO of PDA existed in the newly formed CaP on PDA-CPC, indicating the co-precipitation of CaP with PDA. Furthermore, the newly formed CaP on PDA-CPC was HA confirmed by transmission electron microscopy, which the newly formed HA was in association with PDA. Therefore, PDA increased the capacity of mineralization of CPC and induced the formation of nanoscale bone-like apatite on PDA-CPC. Thus, this provides the feasible route for surface modification on CPC.

A novel porous bioceramics scaffold by accumulating hydroxyapatite spherulites for large bone tissue engineering in vivo. II. Construct large volume of bone grafts.

In vivo engineering of bone autografts using bioceramic scaffolds with appropriate porous structures is a potential approach to prepare autologous bone grafts for the repair of critical-sized bone defects. This study investigated the evolutionary process of osteogenesis, angiogenesis, and compressive strength of bioceramic scaffolds implanted in two non-osseous sites of dogs: the abdominal cavity and the dorsal muscle. Hydroxyapatite (HA) sphere-accumulated scaffolds with controlled porous structures were prepared and placed in the two sites for up to 6 months. Analyses of retrieved scaffolds found that osteogenesis and angiogenesis were faster in scaffolds implanted in dorsal muscles compared with those placed in abdominal cavities. The abdominal cavity, however, can accommodate larger bone grafts with designed shape. Analyses of scaffolds implanted in abdominal cavities [an environment of a low mesenchymal stem cell (MSC) density] further demonstrated that angiogenesis play critical roles during osteogenesis in the scaffolds, presumably by supplying progenitor cells and/or MSCs as seed cells. This study also examined the relationship between the volume of bone grafts and the physiological environment of in vivo bioreactor. These results provide basic information for the selection of appropriate implanting sites and culture time required to engineer autologous bone grafts for the clinical bone defect repair. Based on these positive results, a pilot study has applied the grafts constructed in canine abdominal cavity to repair segmental bone defect in load-bearing sites (limbs).

Study on in vitro release and cell response to alendronate sodium-loaded ultrahigh molecular weight polyethylene loaded with alendronate sodium wear particles to treat the particles-induced osteolysis.

The aim of this study is to investigate in vitro release and cell response to wear particles of ultrahigh molecular weight polyethylene loaded with alendronate sodium (UHMWPE-ALN), a potent bone resorption inhibitor. Wear particles of UHMWPE-ALN with different ALN contents (0.5 wt % or 1.0 wt %) and size ranges (<45 µm or 45-75 µm) were cocultured with macrophages (RAW264.7) and osteoblasts (MC3T3-E1), respectively. The in vitro ALN release was divided into three stages: an initial burst release, subsequent rapid release, and final slow release. The particle size and ALN content of UHMWPE-ALN wear particles affected the in vitro release mainly during initial burst and rapid release. Compared with the control cells, UHMWPE-ALN wear particles stimulated a significant elevation of tumor necrosis factor-alpha (TNF-α) release from macrophages but had no obvious effect on interleukin-6 release. However, this stimulation of TNF-α release could be reduced by ALN released from UHMWPE-ALN wear particles. The wear particle size had stronger effect of on the macrophages compared with the ALN concentration. After coculture with UHMWPE-ALN wear particles, osteoblast proliferation and alkaline phosphatase activities increased moderately with the increase in particle sizes and ALN concentrations. These results suggest that incorporation of ALN in UHMWPE-ALN may be an effective approach to prevent or reduce particles-induced osteolysis.

Reciprocating sliding wear behavior of alendronate sodium-loaded UHMWPE under different tribological conditions.

The aim of this study is to investigate the tribological behaviors and wear mechanisms of ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), a potential drug to treat osteolysis, under different normal loads and lubrication conditions. A mixture of UHMWPE powder and ALN (1.0 wt.%) solution was dried and hot pressed. The static and dynamic friction coefficients of UHMWPE-ALN were slightly higher than those of UHMWPE except under normal load as 10 N and in 25 v/v % calf serum. The specific wear rates of UHMWPE-ALN and UHMWPE were the lowest in 25 v/v % calf serum compared to those in deionized water or physiological saline. In particular, the specific wear rate of UHMWPE-ALN was lower than that of UHMWPE at 50 N in 25 v/v % calf serum. The main wear mechanisms of UHMWPE and UHMWPE-ALN in deionized water and UHMWPE in physiological saline were abrasive. The main wear mechanism of UHMWPE-ALN in physiological saline was micro-fatigue. In 25 v/v % calf serum, the main wear mechanism of UHMWPE and UHMWPE-ALN was abrasive wear accompanied with plastic deformation. The results of Micro-XRD indicated that the molecular deformation of UHMWPE-ALN and UHMWPE under the lower stress were in the amorphous region but in the crystalline region at the higher stress. These results showed that the wear of UHMWPE-ALN would be reduced under calf serum lubricated, which would be potentially applied to treat osteolysis.

Nano-Ag-loaded hydroxyapatite coatings on titanium surfaces by electrochemical deposition.

Hydroxyapatite (HA) coatings on titanium (Ti) substrates have attracted much attention owing to the combination of good mechanical properties of Ti and superior biocompatibility of HA. Incorporating silver (Ag) into HA coatings is an effective method to impart the coatings with antibacterial properties. However, the uniform distribution of Ag is still a challenge and Ag particles in the coatings are easy to agglomerate, which in turn affects the applications of the coatings. In this study, we employed pulsed electrochemical deposition to co-deposit HA and Ag simultaneously, which realized the uniform distribution of Ag particles in the coatings. This method was based on the use of a well-designed electrolyte containing Ag ions, calcium ions and l-cysteine, in which cysteine acted as the coordination agent to stabilize Ag ions. The antibacterial and cell culture tests were used to evaluate the antibacterial properties and biocompatibility of HA/Ag composite coatings, respectively. The results indicated the as-prepared coatings had good antibacterial properties and biocompatibility. However, an appropriate silver content should be chosen to balance the biocompatibility and antibacterial properties. Heat treatments promoted the adhesive strength and enhanced the biocompatibility without sacrificing the antibacterial properties of the HA/Ag coatings. In summary, this study provided an alternative method to prepare bioactive surfaces with bactericidal ability for biomedical devices.

Silver/hydroxyapatite composite coatings on porous titanium surfaces by sol-gel method.

Hydroxyapatite (HA) coatings loaded with nanosilver particles is an attractive method to impart the HA coating with antibacterial properties. Producing Ag/HA coatings on porous Ti substrates have been an arduous job since commonly used line-of-sight techniques are not able to deposit uniform coatings on the inner pore surfaces of the porous Ti. In this study, porous Ti scaffolds with high porosity and interconnected structures were prepared by polymer impregnating method. A sol-gel process was used to produce uniform Ag/HA composite coatings on the surfaces of porous Ti substrates. Ca(NO(3) )(2) ·4H(2) O and P(2) O(5) in an ethyl alcohol based system was selected to prepare the sol, which ensured the homogeneous distribution of Ag in the sol. The characterization revealed that silver particles uniformly distributed in the coatings without agglomeration. High antibacterial ratio (>95%), against E. coli and S. albus was expressed by the silver-containing coatings (Ag/HA 0.8 and 1.6 wt %). The biocompatibility of the Ag/HA 0.8 surfaces was as good as that of pure HA surface, as revealed by culturing osteoblasts on them. The results indicated that Ag/HA 0.8 had the good balance between the biocompatibility and antibacterial properties of the coatings.