Synthesis methods for nanosized hydroxyapatite with diverse structures.

Bioceramics of calcium orthophosphates

Alginate is a natural polysaccharide exhibiting excellent biocompatibility and biodegradability, having many different applications in the field of biomedicine Alginate is readily processable for applicable three-dimensional scaffolding materials such as hydrogels, microspheres, microcapsules, sponges, foams and fibers Alginate-based biomaterials can be utilized as drug delivery systems and cell carriers for tissue engineering Alginate can be easily modified via chemical and physical reactions to obtain derivatives having various structures, properties, functions and applications Tuning the structure and properties such as biodegradability, mechanical strength, gelation property and cell affinity can be achieved through combination with other biomaterials, immobilization of specific ligands such as peptide and sugar molecules, and physical or chemical crosslinking This review focuses on recent advances in the use of alginate and its derivatives in the field of biomedical applications, including wound healing, cartilage repair, bone regeneration and drug delivery, which have potential in tissue regeneration applications

Alginate-Based Biomaterials for Regenerative Medicine Applications.

In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of ∼0.1 to 0.3 μm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value (∼10–20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall–Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process.

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Nanocrystalline materials and coatings

Alginate composites for bone tissue engineering: a review.

In vivo evaluation of porous hydroxyapatite/chitosan-alginate composite scaffolds for bone tissue engineering.

TiN and TiAlN coatings were deposited onto AISI D2 steel substrates by an arc ion plating (AIP) technique These coatings were comparatively studied on their tribological behaviors For this study, the dry sliding wear experiments were conducted on TiN and TiAlN-coated steel discs at two different contact loads, 1 N and 5 N, and three different sliding speeds, 01, 03, 05 m/s, against the steel and alumina ball using a conventional ball-on-disc sliding wear apparatus It was found that the adhesive wear behavior was dominant between both coating layers and steel, while the abrasive wear behavior was prevailed in the case of the alumina ball The friction coefficient of TiAlN coatings became lower than that of TiN coatings at high sliding speed although it was higher at low speed Similar trends were observed regardless of counterpart materials and applying load in this work This suggested that TiAlN coatings may be more advantageous than TiN coatings for high speed machining with respect to machining efficiency and to excellent resistance to high temperature oxidation

A comparative study on tribological behavior of TiN and TiAlN coatings prepared by arc ion plating technique

Antimony-doped tin oxide (ATO) films were deposited on Corning glass 1737 substrates by a plasma-enhanced chemical vapor deposition (PE-CVD) technique using a gas mixture of SnCl4–SbCl5–O2–Ar. Electrical properties and surface morphologies of these films were studied by varying the deposition temperature, input gas ratio, R[=(PSbCl5/PSnCl4)], and RF power. The PE-CVD method effectively enhanced the deposition rate and also improved the surface roughness of the deposit compared with thermal CVD. The antimony doped tin oxide films which had relatively good electrical properties were obtained at a deposition temperature of 450°C, an input gas ratio of R=1.12, and a RF power of 30 W. In addition, the studies on the morphological development of the films by AFM analysis suggested that higher input gas ratio and lower deposition temperature led to a decrease in the surface roughness of the deposited films.

Surface morphologies and electrical properties of antimony-doped tin oxide films deposited by plasma-enhanced chemical vapor deposition

In-situ formation of the hydroxyapatite/chitosan-alginate composite scaffolds

A novel freeze-gel casting/polymer sponge technique has been introduced to fabricate porous hydroxyapatite scaffolds with controlled “designer” pore structures and improved compressive strength for bone tissue engineering applications. Tertiary-butyl alcohol (TBA) was used as a solvent in this work. The merits of each production process, freeze casting, gel casting, and polymer sponge route were characterized by the sintered microstructure and mechanical strength. A reticulated structure with large pore size of 180–360 μm, which formed on burn-out of polyurethane foam, consisted of the strut with highly interconnected, unidirectional, long pore channels (~4.5 μm in dia.) by evaporation of frozen TBA produced in freeze casting together with the dense inner walls with a few, isolated fine pores (<2 μm) by gel casting. The sintered porosity and pore size generally behaved in an opposite manner to the solid loading, i.e., a high solid loading gave low porosity and small pore size, and a thickening of the strut cross section, thus leading to higher compressive strengths.

Seog-Young Yoon

Papers

In vivo evaluation of porous hydroxyapatite/chitosan-alginate composite scaffolds for bone tissue engineering.

A comparative study on tribological behavior of TiN and TiAlN coatings prepared by arc ion plating technique

Surface morphologies and electrical properties of antimony-doped tin oxide films deposited by plasma-enhanced chemical vapor deposition

In-situ formation of the hydroxyapatite/chitosan-alginate composite scaffolds

Hydroxyapatite scaffolds processed using a TBA-based freeze-gel casting/polymer sponge technique