Medicinski vjesnik, Vol. 42 No. (3-4), 2010.
Pregledni rad
Physiological and pathological mineralization: some problems and possible solutions
Helga Füredi-Milhofer
Sažetak
In the first part of this review similarities and differences between physiological and pathological biomineralization (bone and tooth formation, osteoarticular and tooth pathologies, urolithiasis) are discussed. Both processes may be seen as the deposition of ionic crystals from high ionic strength solutions upon / within a preformed organic matrix and the presence or deficiency of crystallization promoters or inhibitors plays a decisive role. However, while physiological mineralization is strictly biologically controlled, urolithiasis is more likely driven by physicochemical factors, such as urinary supersaturation and lack of inhibitors of crystallization and aggregation. In the second part of the review physicochemical research, performed to facilitate understanding ot biomineralization processes is described. It comprises precipitation diagrams for calcium and magnesium phosphates, calcium oxalates, uric acid, sodium and calcium urates, precipitating from high ionic strength solutions at biologically relevant conditions. Here we present a general precipitation diagram of the calcium phosphate system, in which the precipitation boundary and the boundary between the regions of direct crystallization and crystallization via precursor phases are defined by the mean ion activity products and the pH. Kinetic diagrams of spontaneously precipitating systems are represented, which may be interpreted in terms of subsequent or parallel precipitation processes, such as nucleation, crystal growth and aggregation. The dual role of macromolecules, poly-L-glutamate and poly-L-lysine, as crystallization promoters and/or inhibitors is demonstrated by a kinetic study of the phase transformation of amorphous calcium phosphate, ACP, into octacalcium phosphate and/or apatite. It is shown that the polyelectrolytes at low concentrations induce and at higher concentrations inhibit secondary precipitation of the crystalline phase. In the third part of the review applied interdisciplinary research is described. Three chemical methods for testing the inhibitory potential of whole urine were developed. The methods are simple and can be used in a clinical laboratory for discrimination between urines of calcium stone formers and healthy persons. Furthermore a new class of biomimetic organic inorganic composites, as coatings for bioinert metal implants was recently developed. The coating procedure involves “in situ’ growth of calcium phosphate crystals within an organic - inorganic matrix, the inorganic part being ACP. The coatings are tightly anchored to the substrate and exhibit excellent biological properties as verified by in vitro testing and animal experiments.
Ključne riječi
Aggregation; Amorphous calcium phosphate - chemistry; Biomineralization; Crystallization; Inhibitors; Interdisciplinary research; Organic — inorganic composite coatings; Phase transformation; Precipitation diagrams; Precipitation kinetics; Promoters; Urolithiasis - pathology, prevention & control, urine
Hrčak ID:
191889
URI
Datum izdavanja:
1.12.2010.
Posjeta: 1.583 *