Titanium and its alloys have been widely used over the past 3 decades as implants for healing bone defects. Nevertheless, the bioinert property of titanium alloy limits its clinical application and surface modification method is frequently performed to improve the biological and chemical properties. Recently, the delivery of microRNA with osteogenesis capability has been recognized as a promising tool to enhance bone regeneration of implants. Here, we developed a biodegradable coating to modify the titanium surface in order to enhance osteogenic bioactivity. The previous developed nanocapsules were used as the building blocks, and then a bioactive titanium coating was designed to entrap the miR-29b nanocapsules. This coating was not only favorable for cell adhesion and growth but also provided sufficient microRNA transfection efficacy and osteoinductive potential, resulting in a significant enhancement of bone regeneration on the surface of bioinert titanium alloy.Keywords: bone regeneration; miR-29b; nanocapsules; osteogenic bioactivity; titanium

•The film of a mixture of gentamicin sulphate (GS) and chitosan is fabricated.•Physical adsorption and cycling loading is effective for GS loading.•Chitosan layer can adjust the loading efficiency and the release kinetics.•The antibacterial activity is due to the synergistic effects of GS and chitosan.Bacterial infections have been identified as the main cause of orthopaedic implant failure. Owing to their high antibiotic delivery efficiency, titania nanotubes loaded with antibiotics constitute one of the most promising strategies for suppressing bacterial infections. However, it is difficult to control the drug-release behaviour of such nanotubes. Although sealing the nanotubes with a polymer solution provides sustained release effects to a certain extent, it inevitably influences their initial antibacterial activity. This study reports on the controlled release of gentamicin sulphate (GS) from titania nanotube surfaces whereby their initial antibacterial activity remains unaffected. Titania nanotubes were fabricated via electrochemical anodization and loaded with GS through physical adsorption. Experimental results showed that this loading method is feasible and efficient. The GS-loaded titania nanotubes were further covered by a thin film comprising a mixture of GS and chitosan (GSCH). The release kinetics confirmed that the drug release could be controlled by this thin film. Moreover, such a film was shown to not only inhibit initial bacterial adherence owing to its strong antibacterial properties but also enhance cell viability. Thus, GS-loaded titania nanotubes coated with GSCH have considerable potential as biomaterials for preventing initial release and peri-implant infection in the field of orthopaedics.

•Ag- and Sr-substituted HA was prepared by hydrothermal method.•Ag- and Sr-substituted HA coating was deposited on dopamine functionalized titanium.•Ag-substituted HA biofilm showed a remarkable antibacterial activity.•Sr could offset the side effects of Ag.Infection in primary total joint prostheses is attracting considerable attention. In this study, silver (Ag) was incorporated into hydroxyapatite (HA) using a hydrothermal method in order to improve its antimicrobial properties. Strontium (Sr) was added as a second binary element to improve the biocompatibility. The substituted HA samples were fixed on titanium (Ti) substrates by dopamine-assisted immobilization in order to evaluate their antibacterial and biological properties. The results showed that Ag and Sr were successfully incorporated into HA without affecting their crystallinity. Further, the antibacterial tests showed that all the Ag-substituted samples had good anti-bacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Despite their good antibacterial ability, the Ag-substituted samples showed evidence of cytotoxicity on MG63 cells, characterized by low cell density and poor spreadability. The addition of Sr to the Ag-substituted samples considerably reduced the cytotoxicity of Ag. Although the viability of the cells grown on the surfaces of co-substituted HA was not as high as that of the cells grown on the HA surfaces, it is believed that excellent antibacterial properties and good biological activity can be achieved by balancing the dosage of Sr and Ag.

Magnesium (Mg) and strontium (Sr) have been widely used in the field of implanted devices because of their excellent bioactivity. However, the local high ion concentration caused by the implant affects the growth of hydroxyapatite (Ca10(PO4)6(OH)2, HA), which is the main inorganic component of bone and teeth. Many studies have investigated the effect of Mg2+ and Sr2+ on the growth of HA, but no systematic research has been conducted to compare these two ions in terms of the growth of HA. In this study, the substitution of a series of Sr- and Mg-substituted HA was conducted through a conventional hydrothermal method. Comprehensive characterization techniques, including X-ray diffraction, inductive coupled plasma, field emission scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, thermo gravimetric-differential scanning calorimetry, and Fourier transform infrared spectroscopy, were used to examine the effects of Sr2+ and Mg2+ on the phase, morphology, crystallinity, chemical composition, thermal stability, and lattice parameters of HA. The results indicated that Mg ions partially substituted for calcium (Ca) ions in the apatite structure, thus decreasing the lattice parameters, partially adsorbing on the apatite surface that formed the amorphous phase, and inhibiting the crystal growth. By contrast, Sr ions fully substituted for Ca ions and increased the lattice parameters. Both Mg and Sr ions affected the morphology of HA. Crystallinity decreased with the addition of Mg ions (transition from the crystal to amorphous phase was between 30% and 40% Mg), but it was not affected by Sr ions. Thermostability decreased with the addition of Mg (a total weight loss from 8.06 wt% for 10% Mg to 25.81 wt% for 50% Mg), but it had no significant changes in the Sr-substituted samples.

•We designed three kinds of PC-containing copolymers to modify PLA membrane.•A well “anti-fouling” surface could be achieved by PMPC-g-(PEG-b-PLA).•We surmised the PEG spacer might advance the resistance to protein.•The resistance to adsorption depended on surface component and chain mobility.Anti-fouling properties are important for both pharmaceutical and biomedical applications of polylactic acid (PLA). In this study, highly hydrated hydrophilic bilayers containing phosphatidylcholine (PC) and polyethylene glycol (PEG) were applied to PLA films to prevent the protein adsorption and blood platelet adhesion. The PLA films were coated with three PLA copolymers of PC and PEG, namely, a PLA-b-PEG block copolymer with a PC group on the end of a PEG chain (PC-PEG-PLA), a poly[2-methacryloyloxyethyl phosphatidylcholine (MPC)]-PLA graft copolymer (PMPC-g-PLA), and a PMPC-PLA graft copolymer with PEG serving as a spacer (PMPC-g-(PEG-b-PLA)). The influence of the copolymer structure on the anti-fouling properties of PLA film was then investigated. The results showed that the introduction of PC and PEG polar copolymers decreased the water-contact angle (WCA) and increased the equilibrated degree of hydration (Heq) of the PLA surface significantly. The PMPC-g-(PEG-b-PLA) copolymer achieved the lowest WCA value and the highest Heq value as it provided a higher density of PC on the outer surface. In addition, the strong hydration of the PEG and PC groups efficiently suppressed the bovine serum albumin (BSA) and fibrinogen (Fg) adsorption and subsequently inhibited platelet adhesion. The above results demonstrated that a good “anti-fouling” surface layer on the PLA substrate could be achieved by a combination of PEG and PC in copolymers.

In this study, the microstructure, hardness depth profile and cavitation erosion behavior of commercially pure Ti (CP Ti) and Ti−6Al−4V alloys nitrided at 973, 1123 and 1273 K for 16 h were examined. The results revealed that the cavitation erosion behavior of both CP Ti and Ti−6Al−4V alloy was considerably improved by gas nitriding process. The CP Ti nitrided at 973 K has a 2.65-fold increase in cavitation erosion resistance (Re) as compared with untreated specimens, whereas the CP Ti nitrided at 1273 K has the lowest Re. In contrast, the Ti−6Al−4V alloy nitrided at 1273 K exhibited the highest Re while the specimen nitrided at 973 K has the lowest resistance. These results were mainly due to the different properties of the nitrogen diffused zone (NDZ) for CP Ti and alloy. For CP Ti, the NDZ prevented the propagation of microcracks to interior and retarded the erosion due to its homogeneous structure with high hardness, crack-free and good metallurgical bonding. However, the well-organized microstructure was damaged by high temperature (1273 K) treatment and induced the decrease of Re. For Ti−6Al−4V alloy, the NDZ consisted of hard α-Ti grains and soft β-Ti grains resulted in a selective attack for cavitation damage and accelerated the erosion process. But high temperature (1273 K) treatment induced the transformation of β-Ti to α-Ti due to solid solution of nitrogen, which promoted the formation of nitrogen-enriched α-grains (α-Ti(N)) layer on the top of NDZ and sequentially increased the Re up to 6.72 folds. In summary, the significant improvement of cavitation erosion behavior after gas nitriding treatment was mainly attributed to the formation of a unique and homogenous α-Ti(N) layer on the top of the NDZ.Highlights► Gas nitriding enhanced cavitation erosion resistance of CP Ti and Ti–6Al–4V alloy. ► The nitrogen diffused zone played a key role on cavitation erosion behavior. ► Improvement in Re of Ti and Ti–6Al–4V is due to the formation of α-Ti(N) layer.

•Strontium-containing bioactive bone cement (Sr-BC) was designed.•The biocompatibility of Sr-BC was evaluated according ISO 10993 standards.•Preclinical results provide additional assurance for the safety of Sr-BC.Strontium (Sr) has become more attractive for orthopaedic applications as they can simultaneously stimulate bone formation and prevent bone loss. A Sr-containing bioactive bone cement (Sr-BC) has been designed to fix osteoporotic bone fracture. Sr is a trace element, so the safety of containing Sr is concerned when Sr-BC is implanted in human body. The preclinical assessment of biocompatibility of Sr-BC was conducted according to ISO 10993 standards. MTT assay showed that this bioactive bone cement was non-toxic to mouse fibroblasts, and it met the basic requirement for the orthopaedic implant. The three independent genetic toxicity studies including Ames, chromosome aberration and bone marrow micronucleus assays demonstrated absence of genotoxic components in Sr-BC, which reassured the safety concerns of this novel bone cement. The muscle implantation results in present study were also encouraging. The acute inflammation around the cement was observed at 1 week post-implantation; however, no significant difference was observed between control and Sr-BC groups. These responses may be attributed to the presence of the foreign body, but the tissue healed after 12 weeks implantation. In summary, the above preclinical results provide additional assurance for the safety of this implant. Sr-BC can be used as a potential alternative to the traditional bone cement.

Magnesium (Mg) and strontium (Sr) have been widely used in the field of implanted devices because of their excellent bioactivity. However, the local high ion concentration caused by the implant affects the growth of hydroxyapatite (Ca10(PO4)6(OH)2, HA), which is the main inorganic component of bone and teeth. Many studies have investigated the effect of Mg2+ and Sr2+ on the growth of HA, but no systematic research has been conducted to compare these two ions in terms of the growth of HA. In this study, the substitution of a series of Sr- and Mg-substituted HA was conducted through a conventional hydrothermal method. Comprehensive characterization techniques, including X-ray diffraction, inductive coupled plasma, field emission scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, thermo gravimetric-differential scanning calorimetry, and Fourier transform infrared spectroscopy, were used to examine the effects of Sr2+ and Mg2+ on the phase, morphology, crystallinity, chemical composition, thermal stability, and lattice parameters of HA. The results indicated that Mg ions partially substituted for calcium (Ca) ions in the apatite structure, thus decreasing the lattice parameters, partially adsorbing on the apatite surface that formed the amorphous phase, and inhibiting the crystal growth. By contrast, Sr ions fully substituted for Ca ions and increased the lattice parameters. Both Mg and Sr ions affected the morphology of HA. Crystallinity decreased with the addition of Mg ions (transition from the crystal to amorphous phase was between 30% and 40% Mg), but it was not affected by Sr ions. Thermostability decreased with the addition of Mg (a total weight loss from 8.06 wt% for 10% Mg to 25.81 wt% for 50% Mg), but it had no significant changes in the Sr-substituted samples.