Amino Acidic Control of Calcium Phosphate Precipitation by Using the Vapor Diffusion Method in Microdroplets

Abstract

Calcium phosphate precipitation was carried out in the presence of L-aspartic acid (L-asp, iep = 2.77), L-alanine (L-ala, iep = 6.00), and L-arginine (L-arg, iep = 10.76) at different concentrations by using a vapor diffusion sitting drop method (VDSD) in microdroplets. Irrespective of the nature and the concentration of the amino acid used, the early stage in the precipitation consisted in the formation of a white viscous suspension composed of amorphous calcium phosphate (ACP) spherulites. After 1 week, different calcium phosphate phases were found depending on the amino acid nature and concentration. At higher concentrations of L-aspartic acid, brushite (dicalcium phosphate dihydrate, DCDP) platelets and a few needle-like carbonate-hydroxyapatite (HA) crystals were found. In the presence of higher concentrations of L-alanine, the precipitate was composed of both needle-like HA and octacalcium phosphate (OCP) platelets. Finally, at higher concentrations of L-arginine, we obtained carbonate-HA nanocrystals with length of 20À40 nm and a few OCP crystals, as in the blank experiment (without amino acids). The results are explained on the basis of the influence of these amino acids on the pH evolution of the solution and on the nature and strength of the interactions of the major charged species of the amino acids with the surface lattice ions of the apatite precursor phases (DCPD or OCP). A thermodynamic model, based on the temporal existence of OCP in the solution, is proposed to explain the formation of the HA nanocrystals.

Mineralization on polylactide/gelatin composite nanofibers using simulated body fluid containing amino acid

“…4(B, b)). According to literature [31], the needles were supposed to be HA crystals, while those scattered small platelets might as well be octacalcium phosphate (OCP) or ACP, which were thermodynamically instable precursor for HA. The SAED characterization was applied and the diffraction patterns were illustrated as insets in Fig.…”

Biological Crystallization

“…Apart from CaCO 3 , the vapor diffusion method has been adapted to crystallize biomimetic calcium phosphates [125][126][127]. Iafisco et al [126] and Gómez-Morales et al [125] carried out calcium phosphate crystallization experiments using a modified "mushroom" (Figure 20.6) by diffusing vapors of NH 4 HCO 3 through aqueous droplets containing a Ca(CH 3 COO) 2 /(NH 4 ) 2 HPO 4 mixed solution.…”

“…Thus, in additive-free experiments performed over 1 week [126], ACP was obtained at the early stages, then it transformed to octacalcium phosphate (Ca 8 H 2 (PO 4 ) 6 $5H 2 O, OCP) and carbonateapatites nanocrystals whose sizes oscillated between 60 nm and 120 nm. In the presence of L-alanine, the precipitate was composed of both OCP platelets and needle-like carbonate-apatite, and in the presence of L-arginine, carbonate-HA nanocrystals (shown in Figure 20.6) of 20-40 nm and a few OCP crystals [125]. After 1 week, at the higher concentration of L-aspartic acid, brushite (CaHPO 4 $2H 2 O, DCDP) platelets and a few needle-like carbonate-apatite crystals were found.…”

Smart designing of new hybrid materials based on brushite-alginate and monetite-alginate microspheres: Bio-inspired for sequential nucleation and growth

“…Other routes have been also explored to synthesis these calcium phosphates such as sol-gel [38], solid state [39], chemical precipitation [40], hydrothermal [41], hard templating [42], flame-spray route [43], dual irradiation of the microwave and ultrasound [44], and physiological conditions [45]. More recently, Gomez-Morales et al have controlled the precipitation of calcium phosphate such as brushite by using vapor diffusion method in microdroplets and amino acids like organic additives [46]. This current study demonstrates for the first time that the synthesis of hybrid material phosphate-biopolymer can be achieved using gelation of alginate mixed with a phosphate source via complexation of calcium ions.…”