Revised method for preparation of simulated body fluid for assessment of the apatite-forming ability of bioactive materials: proposal of mixing two stock solutions.

Bioactive glasses and glass-ceramics exhibit osteoconductivity, which is the ability to form a direct bond with living bone tissue. This property is typically assessed by observing the formation of a hydroxyapatite layer using simulated body fluid (SBF), a solution designed to mimic the inorganic constituents of human blood plasma. SBF was developed by Kokubo (T.

Apatite Formation on α-Tricalcium Phosphate Modified with Bioresponsive Ceramics in Simulated Body Fluid Containing Alkaline Phosphatase.

Bioresponsive ceramics, a new concept in ceramic biomaterials, respond to biological molecules or environments, as exemplified by salts composed of calcium ions and phosphate esters (SCPEs). SCPEs have been shown to form apatite in simulated body fluid (SBF) containing alkaline phosphatase (ALP). Thus, surface modification with SCPEs is expected to improve the apatite-forming ability of a material.

In Situ and Ex Situ Studies of Ring-Like Assembly of Silica Nanoparticles in the Presence of Poly(propylene oxide)-Poly(ethylene oxide) Block Copolymers.

Block copolymer-mediated self-assembly of colloidal nanoparticles has attracted great attention for fabricating various nanoparticle arrays. We have previously shown that silica nanoparticles (SNPs) assemble into ring-like nanostructures in the presence of temperature-responsive block copolymers poly[(2-ethoxyethyl vinyl ether)--(2-methoxyethyl vinyl ether)] (PEOVE-PMOVE) in an aqueous phase. The ring-like nanostructures formed within an aggregate of PEOVE-PMOVE when the temperature was increased to 45 °C, at which the polymer is amphiphilic.

Biological properties of self-assembled nanofibers of elastin-like block polypeptides for tissue-engineered vascular grafts: platelet inhibition, endothelial cell activation and smooth muscle cell maintenance.

Strategic materials design is essential for the development of small-diameter, tissue-engineered vascular grafts. Self-assembled nanofibers of elastin-like polypeptides represent promising vascular graft components as they replicate the organized elastin structure of native blood vessels. Further, the bioactivity of nanofibers can be modified by the addition of functional peptide motifs.

Transformation behaviour of salts composed of calcium ions and phosphate esters with different linear alkyl chain structures in a simulated body fluid modified with alkaline phosphatase.

Ceramic biomaterials have been used for the treatment of bone defects and have stimulated intense research on such materials. We have previously reported that a salt composed of calcium ions and a phosphate ester (SCPE) transformed into hydroxyapatite (HAp) in a simulated body fluid (SBF) modified with alkaline phosphatase (ALP), and proposed SCPEs as a new category of ceramic biomaterials, namely bioresponsive ceramics. However, the factors that affect the transformation of SCPEs to HAp in the SBF remained unclear.

Organic modification of layered zirconium phosphate/phosphonate for controlled release of therapeutic inorganic ions.

The present study aims to develop a layered zirconium phosphate/phosphonate (LZP) powder to control the release of therapeutic inorganic ions. Organically modified LZPs were successfully prepared with various contents of phenyl groups via a reflux method in an aqueous solution containing phosphoric and phenylphosphonic acids. Powder X-ray diffraction analysis and Fourier transform infrared spectroscopy revealed that the crystal structure of the synthesized LZP samples was identical to that of α-zirconium phosphate, even after modification.

Thixotropic Hydrogels Composed of Self-Assembled Nanofibers of Double-Hydrophobic Elastin-Like Block Polypeptides.

Physically crosslinked hydrogels with thixotropic properties attract considerable attention in the biomedical research field because their self-healing nature is useful in cell encapsulation, as injectable gels, and as bioinks for three-dimensional (3D) bioprinting. Here, we report the formation of thixotropic hydrogels containing nanofibers of double-hydrophobic elastin-like polypeptides (ELPs). The hydrogels are obtained with the double-hydrophobic ELPs at 0.

Incorporation of tetracarboxylate ions into octacalcium phosphate for the development of next-generation biofriendly materials.

Octacalcium phosphate (OCP; Ca(HPO)(PO) ∙ 5HO) is a precursor of hydroxyapatite found in human bones and teeth, and is among the inorganic substances critical for hard tissue formation and regeneration in the human body. OCP has a layered structure and can incorporate carboxylate ions into its interlayers. However, studies involving the incorporation of tetracarboxylic and multivalent (pentavalent and above) carboxylic acids into OCP have not yet been reported.

Human stem cell response to layered zirconium phosphate.

This study aims to evaluate the cytocompatibility of layered zirconium phosphate (ZP) and its derivative material that was organically modified using glycerophosphate (ZGP). The ZP and ZGP particles were prepared a reflux method in an aqueous solution containing phosphoric acid. The field emission scanning electron microscopy showed the prepared samples were fine particles with 70-100 nm diameter.

Tearable and Fillable Composite Sponges Capable of Heat Generation and Drug Release in Response to Alternating Magnetic Field.

Tearable and fillable implants are used to facilitate surgery. The use of implants that can generate heat and release a drug in response to an exogenous trigger, such as an alternating magnetic field (AMF), can facilitate on-demand combined thermal treatment and chemotherapy via remote operation. In this study, we fabricated tearable sponges composed of collagen, magnetite nanoparticles, and anticancer drugs.

Rheology of Dispersions of High-Aspect-Ratio Nanofibers Assembled from Elastin-Like Double-Hydrophobic Polypeptides.

Elastin-like polypeptides (ELPs) are promising candidates for fabricating tissue-engineering scaffolds that mimic the extracellular environment of elastic tissues. We have developed a "double-hydrophobic" block ELP, , inspired by non-uniform distribution of two different hydrophobic domains in natural elastin. has a block sequence of (VGGVG)-(VPGXG)-(VGGVG) that self-assembles to form nanofibers in water.

Ring-Like Assembly of Silica Nanospheres in the Presence of Amphiphilic Block Copolymer: Effects of Particle Size.

Block copolymer-mediated self-assembly of colloidal nanoparticles has attracted great attention for the fabrication of a wide variety of nanoparticle arrays. We have previously shown that silica nanospheres (SNSs) 15 nm in diameter assemble into ring-like nanostructures in the presence of amphiphilic block copolymers poly[(2-ethoxyethyl vinyl ether)- block-(2-methoxyethyl vinyl ether)] (EOVE-MOVE) in an aqueous phase. Here, the effects of particle size of SNSs on this polymer-mediated self-assembly are studied systematically using scanning electron microscopy to observe SNSs of seven different sizes between 13 to 42 nm.

Periodic Surface-Ring Pattern Formation for Hydroxyapatite Thin Films Formed by Biomineralization-Inspired Processes.

Surface morphology is a key factor that might significantly influence the properties of biomaterials. In this study, periodic surface-ring structures have been constructed for calcium phosphate thin films via biomineralization-inspired crystallization process. The patterned octacalcium phosphate crystals have been obtained on poly(2-hydroxyethyl methacrylate) (PHEMA) matrix in the presence of poly(acrylic acid) (PAA).

Double-hydrophobic elastin-like polypeptides with added functional motifs: Self-assembly and cytocompatibility.

We have recently developed a novel double-hydrophobic elastin-like triblock polypeptide called GPG, designed after the uneven distribution of two different hydrophobic domains found in elastin, an extracellular matrix protein providing elasticity and resilience to tissues. Upon temperature trigger, GPG undergoes a sequential self-assembling process to form flexible beaded nanofibers with high homogeneity and excellent dispersibility in water. Given that GPG might be a potential elastin-mimetic material, we sought to explore the biological activities of this block polypeptide.

Fabrication of Porous α-TCP/Gellan Gum Scaffold for Bone Tissue Engineering.

α-tricalcium phosphate (α-TCP, α-Ca3(PO4)2) receives great attention for bone repairing due to its biodegradability and capability of transformation to human bone's main inorganic components, hydroxyapatite (HAp). α-TCP porous scaffold is easily procurable by sintering of the low-temperature polymorph of TCP, β-TCR Still, porous body of α-TCP is too brittle to being handled and shaped, limiting its clinical application as implant materials. To improve mechanical properties of α-TCP porous scaffold, the present study focused on coating of a type of polysaccharides on α-TCP scaffolds.

Organic-Inorganic Composites Toward Biomaterial Application.

Bioactive ceramics are known to exhibit specific biological affinities and are able to show direct integration with surrounding bone when implanted in bony defects. However, their inadequate mechanical properties, such as low fracture toughness and high Young's modulus in comparison to natural bone, limit their clinical application. Bone is a kind of organic-inorganic composite where apatite nanocrystals are precipitated onto collagen fibre networks.

Continuous expansion of the interplanar spacing of octacalcium phosphate by incorporation of dicarboxylate ions with a side chain.

Octacalcium phosphate (OCP) is composed of apatitic and hydrated layers, and can incorporate dicarboxylate ions in its hydrated layers by substitution of HPO4(2-). The (100) interplanar spacing of OCP is increased by incorporation of dicarboxylate ions. Herein, we report continuous expansion of the interplanar spacing of OCP by incorporation of dicarboxylate ions with a side chain.

A unified in vitro evaluation for apatite-forming ability of bioactive glasses and their variants.

The aim of this study was to propose and validate a new unified method for testing dissolution rates of bioactive glasses and their variants, and the formation of calcium phosphate layer formation on their surface, which is an indicator of bioactivity. At present, comparison in the literature is difficult as many groups use different testing protocols. An ISO standard covers the use of simulated body fluid on standard shape materials but it does not take into account that bioactive glasses can have very different specific surface areas, as for glass powders.

Hydroxyapatite formation on titania-based materials in a solution mimicking body fluid: Effects of manganese and iron addition in anatase.

Hydroxyapatite formation on the surfaces of implanted materials plays an important role in osteoconduction of bone substitutes in bone tissues. Titania hydrogels are known to instigate hydroxyapatite formation in a solution mimicking human blood plasma. To date, the relationship between the surface characteristics of titania and hydroxyapatite formation on its surface remains unclear.

Utilization of star-shaped polymer architecture in the creation of high-density polymer brush coatings for the prevention of platelet and bacteria adhesion.

We demonstrate utilization of star-shaped polymers as high-density polymer brush coatings and their effectiveness to inhibit the adhesion of platelets and bacteria. Star polymers consisting of poly(2-hydroxyethyl methacrylate) (PHEMA) and/or poly(methyl methacrylate) (PMMA), were synthesized using living radical polymerization with a ruthenium catalyst. The polymer coatings were prepared by simple drop casting of the polymer solution onto poly(ethylene terephthalate) (PET) surfaces and then dried.

Organic-inorganic composites designed for biomedical applications.

Several varieties of ceramics, such as Bioglass-type glasses, sintered hydroxyapatite and glass-ceramic A-W, exhibit specific biological affinity, i.e., direct bonding to surrounding bone, when implanted in bony defects.

Apatite mineralization behavior on polyglutamic acid hydrogels in aqueous condition: effects of molecular weight.

Apatite-polymer composites mimicking specific structure of natural bone are promised as bone substitutes with moderate flexibility able to be fabricated into desired shapes as well as bone-bonding bioactivity. In order to precipitate the apatite on polymer surfaces, aqueous processing using solution supersaturated to the apatite has been attracting as much attention. Polyglutamic acid (PGA) is a promised candidate of the polymer, since it has high apatite-forming ability owing to abundant carboxyl groups able to trigger the heterogeneous apatite nucleation.

Characteristics of glass ionomer cements composed of glass powders in CaO-SrO-ZnO-SiO₂ system prepared by two different synthetic routes.

Glass ionomer cements (GICs) are composed of an acid degradable glass, polyacrylic acid and water. Sol-gel processing to prepare the glass phase has certain advantages, such as the ability to employ lower synthesis temperatures than melt quenching and glasses that are reported to have higher purity. A previous study reported the effects of glass synthesis route on GIC fabrication.

Biomineralization on chemically synthesized collagen containing immobilized poly-γ-glutamic acid.

Chemically synthesized collagen with a triple helix structure similar to that of natural collagen is attractive as a safe biomaterial. Hybrids of chemically synthesized collagen and apatite are proposed for novel bone substitutes. However their apatite-forming ability in simulated body fluid is still quite low.

Interfacial shear strength of bioactive-coated carbon fiber reinforced polyetheretherketone after in vivo implantation.

Despite the excellent osseointegration of carbon-fiber-reinforced polyetheretherketone (CFR/PEEK) with a surface hydroxyapatite (HA) coating, the bone-implant interfacial shear strength of HA-coated CFR/PEEK after osseointegration is unclear. We examined the interfacial shear strength of HA-coated CFR/PEEK implants after in vivo implantation in a rabbit femur-implant pull-out test model. HA coating was performed by a newly developed method.