Journal of Crystal Growth 133 (1993) 1—12 ~ 0~ CRYSTAL North-Holland GROWT H Influence of monosaccharides and related molecules on the morphology of hydroxyapatite Dominic Walsh, Joanne L. Kingston, Brigid R. Heywood 1 and Stephen Mann 2 School of Chemistry, University of Bath, Bath BA2 7AY, UK Received 22 May 1993; manuscript received in final form 6 July 1993 The influence of monosaccharides and related molecules on the crystal morphology of hydroxyapatite (HAP) precipitated from chloride-containing supersaturated solutions has been studied by transmission electron microscopy. Pulse addition of aliquots of CaCl 2 to Na2HPO4 solutions resulted in the formation of plate-like HAP crystals. In contrast, the presence of the monosaccha- rides D-glucose, D-galactose, D-mannose, glucuronic acid, N-acetyl glucosamine and D-fructose (phosphate : additive = 6: 1) induced the precipitation of needle-shaped HAP crystals elongated along the c-axis. Other molecules, such as sorbitol and 1,2-butanediol, also showed this morphological effect. The order of decreasing aspect ratios was; sorbitol = 1,2-butanediol (25 : 1)> fructose (20: 1)> glucose = galactose = mannose = glucuronic acid N-acetyl glucosamine (10: 1). Expression of the nee- dle-like morphology is discussed in terms of kinetic factors involving nucleation and growth. The former is dependent on the exclusion of C1 from HAP nuclei due to additive interactions with an amorphous calcium phosphate precursor phase. The latter is related to the strength of additive binding with the subsequent development of {100} HAP crystal faces. 1. Introduction A number of kinetic studies of HAP crystal growth in the absence and presence of additives Bone, enamel, dentine and cementum consist such as Mg 2~ [9], CO~ [10], citrate [11], py- of a mineral phase that closely resembles hydrox- rophosphate [12], polyphosphates and polyphos- yapatite (Ca 10(P04)6(OH)2, HAP) together with phonates [131,albumin [14], proteoglycans [15,16], an assemblage of organic macromolecules. Bio- glycosaminoglycans [17], oesteocalcin and os- genic hydroxyapatites are often associated with a teonectin [18] and ATP [19] have been reported. wide variety of trace constituents such as Mg 2+ In contrast, few studies have been undertaken on [1,2] Nat, COY, and Cl— [3], Sr2~ [4,5], F the effect of soluble additives on the crystal mor- [6,7], and P 2O~ [8], and are therefore both phology of HAP. Inorganic ions such as C1 [20], structurally and compositionally complex materi- F— [21], CO~ — [22], Li + [23] and Sr 2± [24] have als. Some of these ions can enter the crystal been shown to produce morphological effects but lattice whilst others remain adsorbed only at sur- there are few counterpart studies involving or- face sites. The presence of extraneous ions may ganic additives. This is surprising since the mor- play an important role in determining the nude- phology of HAP can be significantly different in ation, crystal growth, morphology, aggregation, contrasting biological tissues such as bone (plate- ion-exchange, adsorption and dissolution proper- like) and enamel (needle-like hexagonal prisms) ties of biological and synthetic HAP. [25]. Moreover, many of the properties of syn- thetic HAP will be influenced by crystal size, shape and surface area, and the ability to tailor 1 . . . these characteristics could be relevant to the use Present address: Department of Chemistry, University of Salford, Salford M5 4WT, uK. of I-lAP in chromatography, catalysis and ion-ex- 2 Author to whom correspondence should be addressed. change [26—28], orthopaedics and dentistry [29]. 0022-0248/93/$06.00 © 1993 — Elsevier Science Publishers B.V. All rights reserved