A convenient method for the synthesis of certain poly(benzimidazoles) of high molecular weights has been developed. These polymers were prepared readily by direct polycondensation of activated dicarboxylic acids with 3,3'-diaminobenzidine tetrahydrochloride using phosphorus pentoxide/methanesulfonic acid (PPMA) as condensing agent and solvent. Polycondensation of aromatic dicarboxylic acids containing phenyl ether structures with tetramine proceeded very quickly, was completed within 80 min at 140 °C, and produced poly(benzimidazoles) with inherent viscosities up to 5.8 dL/g. The synthesis of 2-substituted benzimidazoles by the reaction of o-phenylenediamine with carboxylic acids in PPMA was studied in detail to demonstrate the feasibility of the reaction for polymer formation. The thermogravimetry of the aromatic poly(benzimidazoles) showed 10% weight loss in air and nitrogen at 470 and 540 °C, respectively.

Three separate organic, fluorescent emitter molecules with emission spectra corresponding to either blue, orange, or yellow have been covalently attached to an inorganic polyhedral oligomeric silsesquioxane (POSS) core in several controllable combinations. We were able to functionalize POSS with eight of the same emitters or a combination of two different emitters (i.e., blue and orange or blue and yellow). After purification, monodisperse products of the desired ratio of emitters attached to POSS were obtained. Solution and thin-film photoluminescence spectra were measured and compared for both the free emitters and the functionalized POSS. All POSS emitter materials have shown an increase in thermal stability over their free emitter counterparts and were able to be spincoated from solution for the fabrication of OLED devices.

Synthetic octacalcium phosphate (OCP) has a potential to enhance new bone formation and exhibits biodegradable characteristics when implanted in experimentally created bone defects. The precise mechanisms of OCP biodegradation remain unclear, though histological observations have revealed that bone-resorbing osteoclasts appear and resorb implanted OCP. To investigate how osteoclasts develop around implanted OCP, we examined osteoclast differentiation using OCP crystals in vitro. Coculturing of mouse bone marrow cells and osteoblasts in OCP-coated cell culture plates induced osteoclast differentiation, whereas that did not occur without coating. Further, addition of bone morphogenetic protein-2 significantly increased the number of osteoclasts in the OCP-coated wells. In the presence of OCP, osteoblasts expressed receptor activator of NF-kappaB ligand (RANKL), an osteoclast differentiation factor. In addition, when half of each culture well was coated with OCP, osteoclasts were formed in both coated and noncoated areas, suggesting that soluble factors mediate osteoclast differentiation induced by OCP. Also, calcium levels in culture medium were significantly decreased in the presence of OCP, while experimental reduction of calcium from 8.0 to 5.0 mg/dL significantly induced RANKL mRNA expression. These results suggest that OCP itself decreases calcium levels around implanted OCP, which induces osteoclast differentiation through RANKL expression by osteoblasts.

Summary Interleukin (IL)‐4 and IL‐13 are closely related cytokines known to inhibit osteoclast formation by targeting osteoblasts to produce an inhibitor, osteoprotegerin (OPG), as well as by directly targeting osteoclast precursors. However, whether their inhibitory actions are the same remains unclear. The inhibitory effect of IL‐4 was stronger than that of IL‐13 in an osteoclast‐differentiation culture system containing mouse osteoblasts and osteoclast precursors. Both cytokines induced OPG production by osteoblasts in similar time‐ and dose‐dependent manners. However, IL‐4 was stronger in direct inhibition that targeted osteoclast precursors. Furthermore, IL‐4 induced phosphorylation of signal transducer and activator of transcription‐6 (STAT6) at lower concentrations than those of IL‐13 in osteoclast precursors. IL‐4 but not IL‐13 strongly inhibited the expression of nuclear factor of activated T‐cells, cytoplasmic 1 (nuclear factor‐ATc1), a key factor of osteoclast differentiation, by those precursors. Thus, the activities of IL‐4 and IL‐13 toward osteoclast precursors were shown to be different in regards to inhibition of osteoclast differentiation, whereas those toward osteoblasts for inducing OPG expression were equivalent.

Bone morphogenetic proteins (BMPs) possess osteoinductive activities and are useful for clinical treatments, including bone regeneration. We found that transforming growth factor (TGF)-β1 strongly enhances the osteoinductive activity of BMP-2. Collagen sponges containing 5 μg of BMP-2 were implanted into mouse muscle tissues, after which lump-like masses appeared and grew until day 7. Subsequently, calcification occurred in the lump-like masses by day 14. Addition of 50 ng of TGF-β1 to the BMP-2-containing sponges markedly accelerated the growth of the lump-like masses and resulted in a fivefold increase in total bone volume as compared with BMP-2 alone. The number of osteoblasts in ectopic bone tissues at 14 days after implantation induced by BMP-2+TGF-β1 was twofold greater than that with BMP-2 alone, whereas the number of osteoclasts was decreased by half. On the other hand, TGF-β1 accelerated the differentiation of both osteoblasts and osteoclasts in the early stage (2-7 days after implantation) of ectopic bone formation. We also implanted collagen sponges into bone defects surgically created in mouse calvaria. Sponges containing 2.5 μg of BMP-2 and 25 ng of TGF-β1 caused complete filling of the defects with orthotopic bone, whereas those containing 2.5 μg of BMP-2 alone caused only partial filling. These results suggest that TGF-β1 enhances BMP-2-induced ectopic bone formation by accelerating the growth of lump-like masses, and regulates osteoblast and osteoclast generation. Our findings may contribute to the development of a new treatment method for skeletal disorders.