A sustainable Knoevenagel condensation of a series of aldehydes with malononitrile and ethyl cyanoacetate is described. The process is based on the combination of microwave activation and hydroxyapatite catalysis under solvent-free conditions. Products are obtained in and high yields after short reaction times. The effects of the specific surface of porous calcium hydroxyapatite and microwave a...

The aim of this study is to investigate the biomimetic mineralization on a cellulose-based porous matrix with an improved biological profile. The cellulose matrix was precalcified using three methods: (i) cellulose samples were treated with a solution of calcium chloride and diammonium hydrogen phosphate; (ii) the carboxymethylated cellulose matrix was stored in a saturated calcium hydroxide so...

Although blockor granular-type sintered hydroxyapatite are known to show excellent tissue responses and good osteoconductivity, apatite powder elicits inflammatory response. For the fabrication of hydroxyapatite block or granules, sintering is commonly employed. However, the inorganic component of bone and tooth is not high crystalline hydroxyapatite but low crystalline B-type carbonate apatite...

Conclusions: Crystals forming mineral blocks of mostly compact matter are nucleated on organic substrates, with their growth controlled by the diffusion of building units through the virtually stagnant layer of interstitial fluid wetting the deposit surface. Preferentially formed precursors of hydroxyapatite, dicalcium, octacalcium and/or amorphous calcium phosphate, are in later stages of depo...

Results The changes of FT-IR spectraat 1743 cmresulted from hyperoxidation of lipids due to oxidative stress. The characteristic bands at the spectral regions 1200-900 cm and 700-400 cmshowed the formation of low crystallinity biological hydroxyapatite (Ca10(PO4)6(OH)2) and calcium monophosphate (CaHPO4) salts. The results were confirmed using SEM-ΕDAX and XRD analysis. The observed cross-linki...

Recently, premixed calcium phosphate cement pastes have been proposed as biomaterials for bone tissue repair and regeneration. Use of saves the time removes an extra step during a medical operation. α-Tricalcium (α-TCP) based cements set to form deficient hydroxyapatite which has moderate bioresorbtion speed. α-TCP require setting aid, usually sodium or potassium salt, speed up process. Within ...

Different aspects of biominerals formed by apatite and DNA have been investigated using computer modeling tools. Firstly, the structure and stability of biominerals in which DNA molecules are embedded into hydroxyapatite and fluoroapatite nanopores have been examined by combining different molecular mechanics methods. After this, the early processes in the nucleation of hydroxyapatite at a DNA ...

In a previous paper (1) it was shown that discrimination against strontium as compared to calcium, in the formation of synthetic hydroxyapatite, Calo(POJ)6(OH)2, was greater in large, more slowly grown crystals than in small, more rapidly precipitated crystals. The exclusion of strontium as compared to calcium in the hydroxyapatite crystals increases as the preparation conditions approach equil...

FLEISCH, HERBERT, AND SYLVXA BISAZ. Isolation from urine of pyrophosphate, a calczjlcution inhibitor. Am. J. Physiol. 203(4) : 671-675. 1962. -The minimum value of the product, Ca x P, necessary for calcium phosphate precipitation to occur, was determined in vitro. The addition of 2.2 y0 urine to the solutions raised the mean product from 53 to 105 (mg/I oo ml)2, which shows that the urine cont...