PubMed · 6952421
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M Hulterström, A Hulterström. 1981. [Modern prosthetic materials].. https://pubmed.ncbi.nlm.nih.gov/6952421/
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The effects of wollastonite on the mechanical properties and in vitro behavior of hydroxyapatite-Ca polyacrylate composites were studied. Powder mixtures of tetracalcium phosphate, poly(acrylic-co-itaconic), and wollastonite fibers (< or =75% by weight) were hot-pressed for 30 min at 300 degrees C and 60 kpsi. Tensile strengths, elastic moduli, and microstructures of the composites were investigated. The tensile strengths of these composites were improved by the addition of wollastonite fibers, whereas the elastic moduli decreased. The highest value of tensile strength (approximately 155 MPa) was achieved by the addition of 40% wollastonite. Composites were immersed in simulated body fluid (SBF) for up to 14 days and then in 1.5 SBF for a week. The changes in the concentrations of Ca, Si, and P ions and the pH of these solutions indicate bioactivity. An evaluation of the microstructures of the composites after SBF immersion indicated that apatite layers had formed on the surfaces of the composites.
Excellent enantioselectivities up to 99.7% were achieved in the hydrogenation of (E)-beta-(acylamino)acrylates by the use of Rh(I)-complexes of electron-rich diphosphines, t-Bu-BisP and t-Bu-MiniPHOS. Low-temperature NMR experiments testify that monohydrides with beta-carbon atom of the substrate bound to rhodium are involved in the catalytic cycle.
Poly-L-aspartic acid (PLAsp), a biopolymer, and a similar synthetic polymer, poly-acrylic acid (PAA), each consisting of approximately 50 repeating Asp and acrylic acid monomers, respectively, were immobilized onto controlled pore glass (CPG) and evaluated for use as metal ion-exchange materials. Both polymers achieve metal complexation primarily through their repeating carboxylate side groups resulting in a similar binding trend for the metals tested (Ca(2+), Cd(2+), Co(2+), Cu(2+), Mg(2+), Mn(2+), Na(+), Ni(2+), Pb(2+)), with metal binding capacities ranging from <0.1 to 12 micromol metal/g column and <0.1 to 32 micromol metal/g column for PLAsp and PAA respectively. Cu(2+) and Pb(2+) exhibited strong binding to both materials, while the other metals demonstrated only weak or minimal binding. Both columns allowed for quantitative release of bound metals through acid stripping and experienced increased overall metal binding with increasing pH. Both systems also maintained similar structural and chemical stability when continuously exposed to neutral buffered, highly acidic, oxidizing, large molecule rich, and elevated temperature environments. The main differences between the two systems are the material cost and system biodegradability.