Periprosthetic osteolysis-bone loss in the vicinity of a prosthesis-is the most serious problem limiting the longevity of artificial joints. It is caused by bone-resorptive responses to wear particles originating from the articulating surface. This study investigated the effects of graft polymerization of our original biocompatible phospholipid polymer 2-methacryloyloxyethyl phosphorylcholine (MPC) onto the polyethylene surface. Mechanical studies using a hip-joint simulator revealed that the MPC grafting markedly decreased the friction and the amount of wear. Osteoclastic bone resorption induced by subperiosteal injection of particles onto mouse calvariae was abolished by the MPC grafting on particles. MPC-grafted particles were shown to be biologically inert by culture systems with respect to phagocytosis and resorptive cytokine secretion by macrophages, subsequent expression of receptor activator of NF-kappaB ligand in osteoblasts, and osteoclastogenesis from bone marrow cells. From the mechanical and biological advantages, we believe that our approach will make a major improvement in artificial joints by preventing periprosthetic osteolysis.

Using deep sequencing (deepCAGE), the FANTOM4 study measured the genome-wide dynamics of transcription-start-site usage in the human monocytic cell line THP-1 throughout a time course of growth arrest and differentiation. Modeling the expression dynamics in terms of predicted cis-regulatory sites, we identified the key transcription regulators, their time-dependent activities and target genes. Systematic siRNA knockdown of 52 transcription factors confirmed the roles of individual factors in the regulatory network. Our results indicate that cellular states are constrained by complex networks involving both positive and negative regulatory interactions among substantial numbers of transcription factors and that no single transcription factor is both necessary and sufficient to drive the differentiation process.

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The purpose of this study was to enhance the water-solubility of paclitaxel (PTX) using an amphiphilic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer as the solubilizer. PTX is an antineoplastic drug effective for various cancers, especially for ovarian and breast cancers. However, its solubility in aqueous medium is quite low, less than 0.1 microg/mL in water. We prepared the amphiphilic MPC polymers containing hydrophobic units to form aggregates and provide hydrophobic domains in water. The most effective polymer to dissolve the PTX was poly[MPC-co-n-butyl methacrylate(BMA) (PMB30W)] with 70 mol % of the BMA unit. The inside polarity of PMB30W aggregate was the same as that of ethanol, which is a good solvent for dissolving PTX. The diameter of PMB30W aggregate containing 1 mg/mL of PTX was 50 nm in aqueous medium. The concentration of PTX in the PMB30W aqueous solution reached 5.0 mg/mL. The solution was transparent and PTX did not precipitate even when the solution was stored at room temperature for 1 month. Animal experiments indicated that the PMB30W has no adverse effect even when the polymer solution is injected into the bloodstream. From the PMB30W/PTX solution, we prepared by the solvent evaporation method a PMB30W film containing PTX with good transparency. The PMB30W film containing PTX easily dissolved in water to give a clear solution. We conclude that the water-soluble amphiphilic MPC polymers are good solubilizers for PTX as injectable and biocompatible drug formulations.

A hydrophobic to hydrophilic gradient surface was prepared using the tuned photodegradation of an alkylsilane self-assembled monolayer (SAM) using irradiation of vacuum ultraviolet light (wavelength=172 nm). The water contact angle on the photodegraded SAM surface was adjusted using the intensity and time photoirradiation parameters. The formation of a gradient was confirmed by fluorescent labeling. The water drop moved from the hydrophobic to hydrophilic surface with a velocity that depended on the gradient. The higher the gradient, the faster the water moved. For the first time, we have prepared a gradient surface using photodegradation where the movement of a water drop was regulated by the degree of gradation. Considering that the photodegradation technique can be applied to various surfaces and to lithography, this technique will be useful for various material surfaces.