Fabrication of Ag and Ta co-doped amorphous calcium phosphate coating films by radiofrequency magnetron sputtering and their antibacterial activity

Sputtering thin films: Materials, applications, challenges and future directions

Sputtering is an effective technique for producing ultrathin films with diverse applications. The review begins by providing an in-depth overview of the background, introducing the early development of sputtering and its principles. Consequently, progress in advancements made in recent decades highlights the renaissance of sputtering as a powerful technology for creating thin films with varied compositions, structures, and properties. For the first time, we have discussed a thorough overview of several sputtered thin film materials based on metal and metal oxide, metal nitride, alloys, carbon, and ceramic-based thin film along with their properties and their applicability in various fields. We further delve into the applications of sputter-coated thin films, specifically emphasizing their relevance in environmental sustainability, energy and electronics, and biomedical fields. We critically examine the recent advancements in developing sputter-coated catalysts for eliminating water pollutants andhydrogen generation. Additionally, the review sheds light on advantages, shortcomings, and future directions for developing sputter-coated thin films utilized in biodegradable metals and alloys with enhanced corrosion resistance and biocompatibility. This review is a comprehensive integration of recent literature, covering diverse sputtering thin film applications. We delve deeply into various material types and emphasize critical analysis of recent advancements, particularly in environmental, energy, and biomedical fields. By offering insights into both advancements and limitations, the review provides a nuanced understanding essential for practical utilization.

Evaluation of sustained drug release performance and osteoinduction of magnetron-sputtered tantalum-coated titanium dioxide nanotubes

Modifying the drug-release capacity of titanium implants is essential for maintaining their long-term functioning. Titanium dioxide nanotube (TNT) arrays, owing to their drug release capacity, are commonly used in the biomaterial sphere. Their unique half open structure and arrangement in rows increase the drug release capacity. However, their rapid drug release ability not only reduces drug efficiency but also produces excessive local and systemic deposition of antibiotics. In this study, we designed a tantalum-coated TNT system for drug-release optimization. A decreased nanotube size caused by the tantalum nanocoating was observed through SEM and analyzed (TNT: 110 nm, TNT-Ta1: 80 nm, TNT-Ta3: 40 nm, TNT-Ta5: 20 nm, TNT-Ta7: <5 nm). XPS analysis revealed the distribution of the chemical components, especially that of the tantalum element. In vitro experiments showed that the tantalum nanocoating enhanced cell proliferation; in particular, TNT-Ta5 possessed the best cell viability (about 1.18 of TNT groups at 7d). It also showed that the tantalum nanocoating had a positive effect on osteogenesis (especially TNT-Ta5 and TNT-Ta7). Additionally, hydrophilic/hydrophobic drug (vancomycin/raloxifene) release results indicated that the TNT-Ta5 group possessed the most desirable sustained release capacity. Moreover, in this drug release system, the hydrophobic drug showed more sustained release capacity than the hydrophilic drug (vancomycin: sustained release for more than 48 h, raloxifene: sustained release for more than 168 h). More importantly, TNT-Ta5 is proved to be an appropriate drug release system, which possesses cytocompatibility, osteogenic capacity, and sustained drug release capacity.

Journey of Mineral Precursors in Bone Mineralization: Evolution and Inspiration for Biomimetic Design

Bone mineralization is a ubiquitous process among vertebrates that involves a dynamic physical/chemical interplay between the organic and inorganic components of bone tissues. It is now well documented that carbonated apatite, an inorganic component of bone, is proceeded through transient amorphous mineral precursors that transforms into the crystalline mineral phase. Here, the evolution on mineral precursors from their sources to the terminus in the bone mineralization process is reviewed. How organisms tightly control each step of mineralization to drive the formation, stabilization, and phase transformation of amorphous mineral precursors in the right place, at the right time, and rate are highlighted. The paradigm shifts in biomineralization and biomaterial design strategies are intertwined, which promotes breakthroughs in biomineralization-inspired material. The design principles and implementation methods of mineral precursor-based biomaterials in bone graft materials such as implant coatings, bone cements, hydrogels, and nanoparticles are detailed in the present manuscript. The biologically controlled mineralization mechanisms will hold promise for overcoming the barriers to the application of biomineralization-inspired biomaterials.

Silver-Containing Biomaterials for Biomedical Hard Tissue Implants

Bacterial infection caused by biomaterials is a very serious problem in the clinical treatment of implants. The emergence of antibiotic resistance has prompted other antibacterial agents to replace traditional antibiotics. Silver is rapidly developing as an antibacterial candidate material to inhibit bone infections due to its significant advantages such as high antibacterial timeliness, high antibacterial efficiency, and less susceptibility to bacterial resistance. However, silver has strong cytotoxicity, which can cause inflammatory reactions and oxidative stress, thereby destroying tissue regeneration, making the application of silver-containing biomaterials extremely challenging. In this paper, the application of silver in biomaterials is reviewed, focusing on the following three issues: 1) how to ensure the excellent antibacterial properties of silver, and not easy to cause bacterial resistance; 2) how to choose the appropriate method to combine silver with biomaterials; 3) how to make silver-containing biomaterials in hard tissue implants have further research. Following a brief introduction, the discussion focuses on the application of silver-containing biomaterials, with an emphasis on the effects of silver on the physicochemical properties, structural properties, and biological properties of biomaterials. Finally, the review concludes with the authors' perspectives on the challenges and future directions of silver in commercialization and in-depth research.

Tantalum as Trabecular Metal for Endosseous Implantable Applications

During the last 20 years, tantalum has known ever wider applications for the production of endosseous implantable devices in the orthopedic and dental fields. Its excellent performances are due to its capacity to stimulate new bone formation, thus improving implant integration and stable fixation. Tantalum's mechanical features can be mainly adjusted by controlling its porosity thanks to a number of versatile fabrication techniques, which allow obtaining an elastic modulus similar to that of bone tissue, thus limiting the stress-shielding effect. The present paper aims at reviewing the characteristics of tantalum as a solid and porous (trabecular) metal, with specific regard to biocompatibility and bioactivity. Principal fabrication methods and major applications are described. Moreover, the osteogenic features of porous tantalum are presented to testify its regenerative potential. It can be concluded that tantalum, especially as a porous metal, clearly possesses many advantageous characteristics for endosseous applications but it presently lacks the consolidated clinical experience of other metals such as titanium.

Current Advances and Applications of Tantalum Element in Infected Bone Defects

Infected bone defects (IBDs) cause significant economic and psychological burdens, posing a huge challenge to clinical orthopedic surgeons. Traditional approaches for managing IBDs possess inevitable shortcomings; therefore, it is necessary to develop new functionalized scaffolds. Tantalum (Ta) has been widely used in load-bearing orthopedic implants due to its good biocompatibility and corrosion resistance. However, undecorated Ta could only structurally repair common bone defects, which failed to meet the clinical needs of bacteriostasis for IBDs. Researchers have made great efforts to functionalize Ta scaffolds to enhance their antibacterial activity through various methods, including surface coating, alloying, and micro- and nanostructure modifications. Additionally, several studies have successfully utilized Ta to modify orthopedic scaffolds for enhanced antibacterial function. These studies remarkably extended the application range of Ta. Therefore, this review systematically outlines the advances in the fundamental and clinical application of Ta in the treatment of IBDs, focusing on the antibacterial properties of Ta, its functionalization for bacteriostasis, and its applications in the modification of orthopedic scaffolds. This study provides researchers with an overview of the application of Ta in the treatment of IBDs.

A review: strategies to reduce infection in tantalum and its derivative applied to implants

Implant-associated infection is the main reasons for implant failure. Titanium and titanium alloy are currently the most widely used implant materials. However, they have limited antibacterial performance. Therefore, enhancing the antibacterial ability of implants by surface modification technology has become a trend of research. Tantalum is a potential implant coating material with good biological properties. With the development of surface modification technology, tantalum coating becomes more functional through improvement. In addition to improving osseointegration, its antibacterial performance has also become the focus of attention. In this review, we provide an overview of the latest strategies to improve tantalum antibacterial properties. We demonstrate the potential of the clinical application of tantalum in reducing implant infections by stressing its advantageous properties.

Room-temperature growth of fluorapatite/CaCO3 heterogeneous structured composites inspired by human tooth

Organisms can synthesize heterogeneous structures with excellent mechanical properties through mineralization, the most typical of which are teeth. The tooth is an extraordinarily resilient bi-layered material that is composed of external enamel perpendicular to the tooth surface and internal dentin parallel to the tooth surface. The synthesis of enamel-like heterostructures with good mechanical properties remains an elusive challenge. In this study, we applied a biomimetic mineralization method to grow fluorapatite/CaCO₃ (FAP/CaCO₃) heterogeneous structured thin films that mimic their biogenic counterparts found in teeth through a three-step pathway: coating a polymer substrate, growing a layered calcite film, and mineralization of a fluorapatite columnar array on the calcite layer. The synthetic heterostructure composites combine well and exhibit good mechanical properties comparable to their biogenic counterparts. The FAP/CaCO₃ heterogeneous structured composite exhibits excellent mechanical properties, with a hardness and Young's modulus of 1.99 ± 0.02 GPa and 47.5 ± 0.6 GPa, respectively. This study provides a reasonable new idea for unique heterogeneous structured materials designed at room temperature.

Fluorapatite/CaCO₃ thin films were synthesized by mimicking their biogenic counterparts found in teeth using a biomimetic mineralization method. The synthetic heterostructure composites combine well and exhibit excellent mechanical properties.

Tantalum and its derivatives in orthopedic and dental implants: Osteogenesis and antibacterial properties

Implant-associated infections and aseptic loosening are some of the main reasons for implant failure. Therefore, there is an urgent need to improve the osseointegration and antibacterial capabilities of implant materials. In recent years, a large number of breakthroughs in the biological application of tantalum and its derivatives have been achieved. Owing to their corrosion resistance, biocompatibility, osseointegration ability, and antibacterial properties, they have shown considerable potential in orthopedic and dental implant applications. In this review, we provide the latest progress and achievements in the research on osseointegration and antibacterial properties of tantalum as well as its derivatives, and summarize the surface modification methods to enhance their osseointegration and antibacterial properties.

Using HAADF-STEM for atomic-scale evaluation of incorporation of antibacterial Ag atoms in a β-tricalcium phosphate structure

Structural evaluation of ionic additions in calcium phosphates that enhance their performance is a long-lasting area of research in the field of biomedical materials. Ionic incorporation in β-tricalcium phosphate (β-TCP) structures is indispensable for obtaining desirable properties for specific functions and applications. Owing to its complex structure and beam-sensitive nature, determining the extent of ion incorporation and its corresponding location in the β-TCP structure is challenging. Further, very few experimental studies have been able to estimate the location of Ag atoms incorporated in a β-TCP structure while considering the associated changes in lattice parameters. Although the incorporation alters the lattice parameters, the alteration is not significant enough for estimating the location of the incorporated Ag atoms. Here, Ag incorporation in a β-TCP structure was evaluated on atomic scale using scanning transmission electron microscopy (STEM). To the best of our knowledge, this is the first report to unambiguously determine the location of the incorporated Ag atoms in the β-TCP structure by comparing z-contrast profiles of the Ag and Ca atoms by combining the state-of-art STEM observations and STEM image simulations. The Ag incorporation in the Ca(4) sites of β-TCP, as estimated by the Rietveld refinement, was in good agreement with the high-angle annular dark-field STEM observations and the simulations of the location of Ag atoms for [001] and [010] zone axes.