Preparation of hierarchically organized calcium phosphate–organic polymer composites by calcification of hydrogel

Abstract

A novel type of calcium phosphate-organic polymer composite having a hierarchical structure was prepared by calcification of a poly(acrylic acid) hydrogel. Macroscopically, an organic gel containing phosphate ions was transformed into an opaque solid material by diffusion of calcium ions. We observed the formation of micrometer-scale layered structures consisting of nanoscale crystals of hydroxylapatite (HAp) in the opaque products. The laminated architecture resulting from the periodic precipitation of calcium phosphate varied with the reaction conditions, such as the concentrations of the precursor ions and the density of the gel. The nanoscopic structure of HAp crystals was modified by the addition of gelatin to the polymer matrix. q

Nanoscale hydroxyapatite particles for bone tissue engineering

“…Degradable and non-degradable polymers are used in controlled drug delivery, scaffolds for tissue engineering, wound dressing, cosmetic skin masks and protective clothing. Imai, Furuichi and co-workers [122,123] reported hierarchical laminated architecture and porous structures after calcinations of the polymer composite (poly(-acrylic acid)) at 700°C. Polyacrylamide hydrogel is a biomaterial and non-degradable water-based polymer used as tissue filler.…”

Control of the pore architecture in three-dimensional hydroxyapatite-reinforced hydrogel scaffolds

“…In the case of hard tissue substitution, a reasonable strategy is to design ceramic-polymer materials that combine the strength of single components and minimize undesirable drawbacks [18][19][20][21][22][23][24][25][26]. Bioceramics, such as hydroxyapatite, bioactive glass and tricalcium phosphate, impart high biocompatibility and the ability to induce bone formation while mechanically reinforcing the scaffolds [27][28][29][30].…”

Crystallization of calcium phosphate in polyacrylamide hydrogels containing phosphate ions

“…This method is especially useful for crystal growth of poorly soluble compounds. Many sparingly soluble inorganic compounds, such as calcium carbonate [1][2][3][4], calcium phosphate [5][6][7][8][9][10][11][12], calcium tartrate [13,14], and calcium oxalate [15], have been synthesized in gels. The crystals formed in the gel can have a variety of morphologies: dominant factors affecting crystal morphology are degree of supersaturation, rate-determining step of crystal growth, and interactions between the gel molecules and crystals and/or ions.…”

“…Calcium phosphate crystals have been synthesized in various kinds of organic hydrogels, and calcium phosphate-hydrogel composite materials are expected to be useful as bone-repairing materials. As a media for crystal growth, natural or synthetic organic hydrogels such as gelatin [7], agar [8], fibrin [9], polyacrylamide (PAAm) [10,11], and poly(acrylic acid) (PAA) [12] have been used in these fundamental studies of development of bone-repairing materials. Gelatin, fibrin, and agar are typical biodegradable natural polymers, and hence composites of calcium phosphate and these natural polymer hydrogels can be regard as biodegradable bone-repairing materials.…”