Hallmarks of BCZT-based piezoceramics: From chemical fundamental to processing route and biomedical applications

Microwave-assisted hydrothermal synthesis of carbonated apatite with calcium and phosphate resources derived from green mussel shell and bovine bone wastes

The life of human beings is moving at a breakneck pace, with a fast-moving life demanding the need for devices for use in biomedical applications, which attracts the interested researcher to work on ensuring novel breakthroughs. Processing of biomaterials is one of the key factors that will exert an influence on impacting the attributes of a biomaterial. Additive manufacturing is one of the promising routes by which layer-by-layer creation of parts takes place from a computer-aided design (CAD) file. Parts that cannot or are difficult to manufacture by other processing routes can be easily manufactured using the technique of additive manufacturing (AM). Parts, such as (i) stents, (ii) customized prosthetics, (iii) organs, and (iv) implants can be easily manufactured using the technique of additive manufacturing (AM). With noticeable advances in the domain specific to additive manufacturing, the biomedical field is being revolutionized, and viable solutions to difficult problems are being put forth with ease, and the resultant by-products offer a combination of acceptable to good properties. The key benefits of the technique of additive manufacturing (AM) are low cost, minimal material waste, and enhanced product reliability. This study explores recent developments in both alloys and composite materials processed by the techniques of additive manufacturing for selection and use in biomedical applications. This review provides a highlight of the different additive manufacturing techniques with specific reference to biomedical applications and additive manufacturing of titanium alloys, the Co-Cr alloy, the magnesium alloys and their composite counterparts. Multidisciplinary research will be required to meet and overcome any and all obstacles while concurrently fulfilling the potential of additive manufacturing (AM) in the years ahead.

The work reviews the research and development status of magnesium alloy, with more attention to the methodologies and technologies adopted to improve the properties of AZ91 alloy. The drive force of utilizing magnesium alloys for automotive and biomedical application is light weightiness and biocompatibility respectively. However, the softness and high activity of magnesium alloys result in high wear and high corrosion rate respectively. One of the essential factors influencing the properties of magnesium alloy is its microstructure. Consequently, the grain size, morphology and distribution of phase constituents influence the properties of magnesium alloys. The modification of microstructure through processing route (hot working and cold working), heat treatment, and alloying elements improves the mechanical, corrosion, biocompatible, and tribological properties of magnesium alloys. Besides microstructural modification processes, addition of reinforcements, and coatings improves the properties of magnesium alloys. This article emphasis on the recent research on the technologies to improve the microstructure, hardness, tensile strength, ductility, yield strength, wear resistance, and corrosion resistance of magnesium alloy AZ91. Moreover, this review addresses the key issues hindering the applications of magnesium alloys for structural and biomedical applications.

In this paper we present a novel cost benefit operator that assists multi level genetic algorithm searches. Through the use of the cost benefit operator, it is possible to dynamically constrain the search of the base level genetic algorithm, to suit the user's requirements. Initially we review meta-evolutionary (multi-level genetic algorithm) approaches. We note that the current literature has abundant studies on meta-evolutionary GAs. However these approaches have not identified an efficient approach to termination of base GA search or a means to balance practical consideration such as quality of solution and the expense of computation. Our quality time tradeoff operator (QTT) is user defined, and acts as a base level termination operator and also provides a fitness value for the meta-level GA. In this manner the amount of computation time spent on less encouraging configurations can be specified by the user. Our approach has been applied to a computationally intensive test problem which evaluates a large set of configuration settings for the base GAs. This approach should be applicable across a wide range of practical problems (e.g. routing, logistic and biomedical applications).

Cascade molecules are nearly uniform-sized macromolecules of small molecules or linear polymer cores built around symmetric branching units. A wide range of biological properties can be achieved with phosphorus-containing dendrimers, depending on their terminal functions, ranging from biomaterials to imaging, drug delivery, and acting as a drug by themselves. This feature article presents significant examples of phosphorus-containing dendrimers used to develop biochips, support cell cultures, carry or deliver biomacromolecules and drugs, bioimaging, and combinational benefits. Because of the thermal stability, ferrocene function, and physical and chemical properties of phosphorus, dendrimers show greater rigidity, mobility, and strength. These dendrimers will be discussed as having a favorable effect on cell growths, especially on neuronal cells, as well as human immune cells like natural killer cells and monocytes, which have a crucial part in preventing cancerous and viral infections. Several phosphorus dendrimers are effective as drugs by themselves (drug per se) and show their activity against neurodegenerative diseases, cancer, inflammation, ocular hypertension, and transmissible spongiform encephalopathies (TSEs) in both in vivo and in vitro. The present review discusses the synthetic route, fabrications, and biomedical applications of phosphorus-containing dendrimers. The toxicity of these dendrimers was also reported.

2 - Metals

Hydrogels are widely used in various biomedical applications, as they cannot only serve as materials for biofabrication but also as depots for the administration of drugs. However, the possibilities of formulation of water‐insoluble drugs in hydrogels are rather limited. Herein, we assembled recombinant spider silk gels using a new processing route with aqueous–organic co‐solvents, and the properties of these gels could be controlled by the choice of the co‐solvent. The presence of the organic co‐solvent further enabled the incorporation of hydrophobic drugs as exemplarily shown for 6‐mercaptopurine. The developed gels showed shear‐thinning behaviour and could be easily injected to serve, for example, as drug depots, and they could even be 3D printed to serve as scaffolds for biofabrication. With this new processing route, the formulation of water‐insoluble drugs in spider silk‐based depots is possible, circumventing common pharmaceutical solubility issues.

Biomedical applications are an emerging field of interest for magnesium technology, envisioning biodegradable implants that resorb in the human body after having cured a particular medical condition (such as artery clogging or bone fractures). This challenges research in a sense that the materials to be used need to dissolve in vivo in a controlled fashion without leaving harmful remainders and while maintaining sufficient strength and other (mechanical) attributes as long as necessary. To comply to the requirements, magnesium alloys as well as their processing routes into implants need to be tailored. While new alloy compositions are receiving ample attention, the paper at hand addresses the processing issue. The application of choice is the (cardio)-vascular stent. Different steps in manufacturing magnesium AZ-alloy stent tube are considered, including equal channel angular pressing, extrusion and subsequent drawing operations. Results show that the processing route has an important influence on the microstructure of the finished stent tube and hence on its functional performance.

Influence of Equal Channel Angular Processing and Rotary Swaging on the Mechanical and Degradation Properties of WE43 Mg Alloy

Chemical species mixing during direct energy deposition of bimetallic systems using titanium and dissimilar refractory metals for repair and biomedical applications

Human hair keratins (HHK) are natural structural proteins that can be extracted from abundant hair waste and valorised into biomaterials for tissue regeneration, wound healing, and drug delivery etc. The emergence of HHK in biomedical applications is attributed to their proven biocompatibility as well as their potential to promote cell adhesion and proliferation due to the presence of LDV (leucine-aspartic-valine) cell adhesion motifs and residual regulatory molecules. In a clinical setting, HHK-based templates could also serve as autologous alternatives which minimise the risk of xenogeneic infections or chemically induced cyto-toxicity. Nonetheless, conventional methods to translate HHK proteins into meaningful three-dimensional (3D) constructs often require chemical modifications or cross-linking additives. Such processing routes can be complicated and may compromise the resultant biocompatibility of the scaffolds. To circumvent the use of chemical additives, cryogelation was adopted as a clean and facile technique to fabricate 3D HHK scaffolds with tuneable physical properties. This novel concept of amalgamating HHK and cryogelation was premised on the ability of cryogelation to facilitate natural crosslinking between the HHK molecules through disulphide bonds due to the abundance of cysteine residues. However, the actual assembly mechanism of HHK during cryogelation remained speculative and prompted further investigation on the contribution of various intermolecular associations including hydrophobic interactions, hydrogen, and ionic bonding. In this research, inhibition studies using bond disrupting agents and gel solubilisation studies revealed that both disulphide bonds and hydrophobic interactions are cooperatively vital for gel network formation and stabilization. Inhibition of either interaction resulted in incomplete or delayed gelation.

Electrochemical and mechanical performance of biodegradable ZX30 alloy using multi-channel spiral twist extrusion (MCSTE) for biomedical implants

Magnesium-based composites and alloys for medical applications: A review of mechanical and corrosion properties

Titanium (Ti) is the most widely used metal in biomedical applications because of its biocompatibility; however, the significant difference in the mechanical properties between Ti and the surrounding tissues results in stress shielding which is detrimental for load-bearing tissues. In the current study, to attenuate the stress shielding effect, a new processing route was developed. It aimed at growing thick poly(methyl methacrylate) (PMMA) layers grafted on Ti substrates to incorporate a polymer component on Ti implants. However, the currently available methods do not allow the development of thick polymeric layers, reducing significantly their potential uses. The proposed route consists of an alkali activation of Ti substrates followed by a surface-initiated atom transfer radical polymerization using a phosphonic acid derivative as a coupling agent and a polymerization initiator and malononitrile as a polymerization activator. The average thickness of the grown PMMA layers is approximately 1.9 μm. The Ti activation-performed in a NaOH solution-leads to a porous sodium titanate interlayer with a hierarchical structure and an open microporosity. It promotes the covalent grafting reaction because of high hydroxyl groups' content and enables establishing a further mechanical interlocking between the growing PMMA layer and the Ti substrate. As a result, the produced graduated structure possesses high Ti/PMMA adhesion strength (∼260 MPa). Moreover, the PMMA layer is (i) thicker compared to those obtained with the previously reported techniques (∼1.9 μm), (ii) stable in a simulated body fluid solution, and (iii) biocompatible. This strategy opens new opportunities toward hybrid prosthesis with adjustable mechanical properties with respect to host bone properties for personalized medicines.

Particle-reinforced titanium matrix composites (TMCs) have been an area of active research in recent times. This is because of their high specific strength, excellent mechanical properties, and aversion to corrosion which makes them ideal for aerospace, automotive, and biomedical applications. The mechanical and physical properties of TMCs rely on the reinforcement phases and the processing route. Carbides, borides, nitrides, oxides, silicides, and graphene/carbon-matrix reinforcements for TMCs are broadly adopted. Powder metallurgy (PM) is a widely used method for the production of TMCs. This study reviews the common particles that are used as reinforcements in TMCs, their properties, production, the PM techniques used for consolidating them in TMCs, and their effect on the TMCs produced. Current literature and developments in TMCs have also been considered in this review.