Hydrogels for tissue engineering.

Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, in order to improve the biological, chemical, and mechanical properties, surface modification is often performed. This article reviews the various surface modification technologies pertaining to titanium and titanium alloys including mechanical treatment, thermal spraying, sol–gel, chemical and electrochemical treatment, and ion implantation from the perspective of biomedical engineering. Recent work has shown that the wear resistance, corrosion resistance, and biological properties of titanium and titanium alloys can be improved selectively using the appropriate surface treatment techniques while the desirable bulk attributes of the materials are retained. The proper surface treatment expands the use of titanium and titanium alloys in the biomedical fields. Some of the recent applications are also discussed in this paper.

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Surface modification of titanium, titanium alloys, and related materials for biomedical applications

Fibroblasts can condense a hydrated collagen lattice to a tissue-like structure 1/28th the area of the starting gel in 24 hr. The rate of the process can be regulated by varying the protein content of the lattice, the cell number, or the con- centration of an inhibitor such as Colcemid. Fibroblasts of high population doubling level propagated in vitro, which have left the cell cycle, can carry out the contraction at least as efficiently as cycling cells. The potential uses of the system as an immu- nologically tolerated "tissue" for wound hea ing and as a model for studying fibroblast function are discussed.

Production of a tissue-like structure by contraction of collagen lattices by human fibroblasts of different proliferative

Novel bioactive materials with different mechanical properties.

Novel crosslinking methods to design hydrogels

Self-assembled monolayers (SAMs) of alkanethiols having CH3, PO4H2, COOH, CONH2, OH, and NH2 terminal groups formed on a gold surface via sulfur attachment were soaked in a simulated body fluid (SBF), whose ion concentrations were nearly equal to those of human blood plasma, at 37 degrees C for up to 40 days. The effect of their terminal functional groups on apatite formation was assessed using X-ray photo-electron spectroscopic (XPS) measurement and a quartz crystal microbalance (QCM) technique. The Ca and P atoms were detected, of which element intensities increased with time, on SAMs except for the alkanethiol having the methyl terminal group. The Ca/P atomic ratios of the apatites formed on the SAMs ranged from around 1.0 to around 1.3. The most potent inducer for apatite formation, judged from the growth rate (micrometers per day) calculated from the weight change during QCM measurement, was the SAM of the alkanethiol with the PO4H2 group, followed by that of the alkanethiol with the COOH group. The SAMs of the alkanethiols with the CONH2, OH, and NH2 groups possessed much weaker inducing powers than the former two SAMs. Little weight change was observed for the methyl-group-terminated alkanethiol SAM. The growth rates increased with time, irrespective of the terminal group species among apatite formation-inducing groups. During the experimental observation period, the following relationship held. The growth rate decreased in the order PO4H2 > COOH >> CONH2 approximately equal to OH > NH2 >> CH3 approximately equal to 0. Some negatively charged groups strongly induced apatite formation but the positively charged group did not, it can be said that the apatite formation initiated via calcium ion-absorption upon complexation with a negative surface-charged group may be dominant in biomaterial calcification where ionic species directly contact the biomaterial surface in body fluids.

Surface functional group dependence on apatite formation on self-assembled monolayers in a simulated body fluid

Hydrogel formation via hybridization of oligonucleotides derivatized in water-soluble vinyl polymers

Surface macromolecular architectures with regional dimensional precision, control of the thickness of a graft layer, and blocks of graft chains were attempted using the surface photo-graft copolymerization method pioneered by Otsu et al. This is based on the photochemistry of benzyl N,N-diethyldithiocarbamate, which can be photolyzed into a radical pair (one radical can initiate radical polymerization and the other tends to recombine with the former radical). Ultraviolet light (UV) irradiation of a benzyl N,N-diethyldithiocarbamyl group-immobilized polymer surface in the presence of a vinyl monomer such as N,N-dimethylacrylamide, N-[3-(dimethylamino)propyl]acrylamide, methacrylic acid, or styrene at room temperature allowed precise control of the macromolecular architectures of the grafted surfaces. X-ray photoelectron spectroscopy (XPS) analyses and water contact angle measurements before and after UV irradiation in a monomer solution provided evidence that the graft copolymerization proceeded only durin...

Takehisa Matsuda

Papers

Surface functional group dependence on apatite formation on self-assembled monolayers in a simulated body fluid

Hydrogel formation via hybridization of oligonucleotides derivatized in water-soluble vinyl polymers

Surface macromolecular architectural designs using photo-graft copolymerization based on photochemistry of benzyl N,N-diethyldithiocarbamate

Mechanical stress-induced orientation and ultrastructural change of smooth muscle cells cultured in three-dimensional collagen lattices.

Venous reconstruction using hybrid vascular tissue composed of vascular cells and collagen: Tissue regeneration process