Microwave-assisted fabrication of titanium implants with controlled surface topography for rapid bone healing

Poly-l-lysine/Sodium Alginate Coating Loading Nanosilver for Improving the Antibacterial Effect and Inducing Mineralization of Dental Implants

In recent years, antibacterial surface modification of titanium (Ti) implants has been widely studied in preventing implant-associated infection for dental and orthopedic applications. The purpose of this study was to prepare a composite coating on a porous titanium surface for infection prevention and inducing mineralization, which was initialized by deposition of a poly-l-lysine (PLL)/sodium alginate(SA)/PLL self-assembled coating, followed by dopamine deposition, and finally in situ reduction of silver nanoparticles (AgNPs) by dopamine. The surface zeta potential, SEM, XPS, UV-vis, and water contact angle analyses demonstrate that each coating was successfully prepared after the respective steps and that the average sizes of AgNPs were 20-30 nm. The composite coating maintained Ag⁺ release for more than 27 days in PBS and induced mineralization when incubated in SBF. The antibacterial results showed that the composite coating inhibited/killed bacteria on the material surface and killed bacteria around them. In addition, although this coating inhibited the initial adhesion of osteoblasts, the mineralized surface greatly enhanced the cytocompatibility. Thus, we concluded that the composite coating could prevent bacterial infections and facilitate mineralization in vivo in the early postoperative period, and then, the mineralized surface could enhance the cytocompatibility.

A comparative study of the effect of submicron porous and smooth ultrafine-grained Ti-20Mo surfaces on osteoblast responses

The surface of an orthopaedic implant plays a crucial role in determining the adsorption of proteins and cell functions. A detailed comparative study has been made of the in vitro osteoblast responses to coarse-grained (grain size: 500 μm), ultrafine-grained (grain size: 100 nm), coarse-porous (pore size: 350 nm), and fine-porous (pore size: 155 nm) surfaces of Ti-20Mo alloy. The purpose was to provide essential experimental data for future design of orthopaedic titanium implants for rapid osseointegration. Systematic original experimental data was produced for each type of surfaces in terms of surface wettability, cell morphology, adhesion, growth, and differentiation. Microscopic evidence was collected to reveal the detailed interplay between each characteristic surface with proteins or cells. Various new observations were discussed and compared with literature data. It was concluded that the coarse-porous surfaces offered the optimum topographical environment for osteoblasts and that the combination of ultrafine grains and considerable grain boundary areas is not an effective way to enhance cell growth and osteogenic capacity. Moreover, pore features (size and depth) have a greater effect than smooth surfaces on cell growth and osteogenic capacity. It proves that cells can discern the difference in pore size in the range of 100-350 nm. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2020-2033, 2018.

Dual-Functionalized Graphene Oxide Based siRNA Delivery System for Implant Surface Biomodification with Enhanced Osteogenesis

Surface functionalization by small interfering RNA (siRNA) is a novel strategy for improved implant osseointegration. A gene delivery system with safety and high transfection activity is a crucial factor for an siRNA-functionalized implant to exert its biological function. To this end, polyethylene glycol (PEG) and polyethylenimine (PEI) dual-functionalized graphene oxide (GO; nGO-PEG-PEI) may present a promising siRNA vector. In this study, nanosized nGO-PEG-PEI was prepared and optimized for siRNA delivery. Titania nanotubes (NTs) fabricated by anodic oxidation were biomodified with nGO-PEG-PEI/siRNA by cathodic electrodeposition, designated as NT-GPP/siRNA. NT-GPP/siRNA possessed benign cytocompatibility, as evaluated by cell adhesion and proliferation. Cellular uptake and knockdown efficiency of the NT-GPP/siRNA were assessed by MC3T3-E1 cells, which exhibited high siRNA delivery efficiency and sustained target gene silencing. Casein kinase-2 interacting protein-1 (Ckip-1) is a negative regulator of bone formation. siRNA-targeting Ckip-1 (siCkip-1) was introduced to the implant, and a series of in vitro and in vivo experiments were carried out to evaluate the osteogenic capacity of NT-GPP/siCkip-1. NT-GPP/siCkip-1 dramatically improved the in vitro osteogenic differentiation of MC3T3-E1 cells in terms of improved osteogenesis-related gene expression, and increased alkaline phosphatase (ALP) production, collagen secretion, and extracellular matrix (ECM) mineralization. Moreover, NT-GPP/siCkip-1 led to apparently enhanced in vivo osseointegration, as indicated by histological staining and EDX line scanning. Collectively, these findings suggest that NT-GPP/siRNA represents a practicable and promising approach for implant functionalization, showing clinical potential for dental and orthopedic applications.

Ti-GO-Ag nanocomposite: the effect of content level on the antimicrobial activity and cytotoxicity

Surface modification of titanium (Ti) implants are extensively studied in order to obtain prominent biocompatibility and antimicrobial activity, especially preventing implant-associated infection. In this study, Ti substrates surface were modified by graphene oxide (GO) thin film and silver (Ag) nanoparticles via electroplating and ultraviolet reduction methods so as to achieve this purpose. Microstructures, distribution, quantities and spectral peaks of GO and Ag loading on the Ti sheets surface were characterized. GO-Ag-Ti multiphase nanocomposite exhibited excellent antimicrobial ability and anti-adherence performance. Subsequently, morphology, membrane integrity, apoptosis and relative genes expression of bacteria incubated on the Ti samples surface were monitored to reveal the bactericidal mechanism. Additionally, the cytotoxicity of Ti substrates incorporating GO thin film and Ag nanoparticles were investigated. GO-Ag-Ti composite configuration that have outstanding antibacterial properties will provide the foundation to study bone integration in vitro and in vivo in the future.

Falling Leaves Inspired ZnO Nanorods-Nanoslices Hierarchical Structure for Implant Surface Modification with Two Stage Releasing Features

Inspired from falling leaves, ZnO nanorods-nanoslices hierarchical structure (NHS) was constructed to modify the surfaces of two widely used implant materials: titanium (Ti) and tantalum (Ta), respectively. By which means, two-stage release of antibacterial active substances were realized to address the clinical importance of long-term broad-spectrum antibacterial activity. At early stages (within 48 h), the NHS exhibited a rapid releasing to kill the bacteria around the implant immediately. At a second stage (over 2 weeks), the NHS exhibited a slow releasing to realize long-term inhibition. The excellent antibacterial activity of ZnO NHS was confirmed once again by animal test in vivo. According to the subsequent experiments, the ZnO NHS coating exhibited the great advantage of high efficiency, low toxicity, and long-term durability, which could be a feasible manner to prevent the abuse of antibiotics on implant-related surgery.

Alternating Current Electrophoretic Deposition for the Immobilization of Antimicrobial Agents on Titanium Implant Surfaces

One prominent cause of implant failure is infection; therefore, research is focusing on developing surface coatings that render the surface resistant to colonization by micro-organisms. Permanently attached coatings of antimicrobial molecules are of particular interest because of the reduced cytoxicity and lower risk of developing resistance compared to controlled release coatings. In this study, we focus on the chemical grafting of bioactive molecules on titanium. To concentrate the molecules at the metallic implant surface, we propose electrophoretic deposition (EPD) applying alternating current (AC) signals with an asymmetrical wave shape. We show that for the model molecule bovine serum albumin (BSA), as well as for the clinically relevant antifungal lipopeptide caspofungin (CASP), the deposition yield is drastically improved by superimposing a DC offset in the direction of the high-amplitude peak of the AC signal. Additionally, in order to produce immobilized CASP coatings, this experimental AC/DC-EPD method is combined with an established surface activation protocol. Principle component analysis (PCA) of time-of-flight secondary ion mass spectrometry (ToF-SIMS) data confirm the immobilization of CASP with higher yield as compared to a diffusion-controlled process, and higher purity than the clinical CASP starting suspensions. Scratch testing data indicate good coating adhesion. Importantly, the coatings remain active against the fungal pathogen C. albicans as shown by in vitro biofilm experiments. In summary, this paper delivers a proof-of-concept for the application of AC-EPD as a fast grafting tool for antimicrobial molecules without compromising their activities.

A novel microwave recipe for an antibiofilm titanium surface

A microwave based method for the surface modification of titanium was demonstrated for biomedical applications. The surfaces were characterized using XRD, HR-SEM and Goniometer. The absence of rutile, anatase and brookite phases and the presence of an amorphous near-native oxide film were confirmed. The microwave oxidized (MWO) surfaces exhibited a significant antibiofilm activity against Escherichia coli and Staphylococcus aureus. In the presence and absence of the water pot, the oxidation times of 60 and 20min demonstrated a high antibiofilm property respectively. The surfaces turned more hydrophobic with increasing oxidation time. The viability of L6 cells remained unaffected on the MWO oxidized surfaces, signifying no loss in biocompatibility. This systematic study presents MWO as a promising technique for solving the biofilm problem faced by the otherwise robust titanium.

Bioactivity response of Ta1-xOx coatings deposited by reactive DC magnetron sputtering

The use of dental implants is sometimes accompanied by failure due to periimplantitis disease and subsequently poor esthetics when soft-hard tissue margin recedes. As a consequence, further research is needed for developing new bioactive surfaces able to enhance the osseous growth. Tantalum (Ta) is a promising material for dental implants since, comparing with titanium (Ti), it is bioactive and has an interesting chemistry which promotes the osseointegration. Another promising approach for implantology is the development of implants with oxidized surfaces since bone progenitor cells interact with the oxide layer forming a diffusion zone due to its ability to bind with calcium which promotes a stronger bond. In the present report Ta-based coatings were deposited by reactive DC magnetron sputtering onto Ti CP substrates in an Ar+O2 atmosphere. In order to assess the osteoconductive response of the studied materials, contact angle and in vitro tests of the samples immersed in Simulated Body Fluid (SBF) were performed. Structural results showed that oxide phases where achieved with larger amounts of oxygen (70 at.% O). More compact and smooth coatings were deposited by increasing the oxygen content. The as-deposited Ta coating presented the most hydrophobic character (100°); with increasing oxygen amount contact angles progressively diminished, down to the lowest measured value, 63°. The higher wettability is also accompanied by an increase on the surface energy. Bioactivity tests demonstrated that highest O-content coating, in good agreement with wettability and surface energy values, showed an increased affinity for apatite adhesion, with higher Ca/P ratio formation, when compared to the bare Ti substrates.