Growth-inhibited hydroxyapatite, process for its preparation and use

Abstract

A growth-inhibited hydroxyapatite is contained in agglomerates of prestructured collagen templates, wherein the prestructured collagen templates are denatured or broken up so that fibrillogenesis of the prestructured collagen templates is inhibited. Epitactic hydroxyapatite crystallites with a crystallite size below a critical nucleus radius are formed on the prestructured collagen templates.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional application of U.S. patent application Ser. No. 13 / 812,497 having a filing date of 26 Jan. 2013, which is a national stage filing of international application No. PCT / EP2011 / 063470 having an international filing date of 4 Aug. 2011 and designating the United States, the international application claiming a priority date of 4 Aug. 2010, based on prior filed German patent application No. 10 2010 038 926.9, the entire contents of the aforesaid United States patent application, the international application, and the aforesaid German patent application being incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]The invention concerns growth-inhibited hydroxyapatite (referred to in the following as wHAP) for the improvement of bone healing. It differs from the apatites used already up to now in that it releases calcium and phosphate ions in physiological solutions and, in contrast to customary hydrox...

AI Technical Summary

Benefits of technology

[0020]The HAP crystallites according to the invention dissolve in a narrow range of calcium concentration of 2.2 to 2.7 mmol / l. The proliferation and the differentiation of bone-forming cells are positively influenced by the additional supply of calcium ions in the vicinity of a bone defect, and bone formation / bone healing is promoted.

[0074]Composite materials obtained in this way can be used in biomedicine as an implant material which is required to exhibit a release of calcium and phosphate ions in addition to having biocompatibility, degradability and sufficient strength.

Problems solved by technology

However, they are subject to special demands, depending on implantation site, with regard to biocompatibility, mechanical strength, degradation behavior in case of resorbable implants, and bioactivity.

On the other hand, some publications also report negative effects on the cell behavior in connection with a high bioactivity of the biomaterial.

Since collagen-based products alone as a rule do not match the mechanical requirements as a bone substitute, they are substituted or supplemented with inorganic-non-metallic phases.

However, the degradation behavior of TCP is calculable only with difficulty.

These HAP crystals have thus the undesirable property of removing from the electrolyte surroundings calcium as well as phosphate ions causing them to grow and the calcium and phosphate ions to be bound in physiological solutions.

A high bioactivity as it is usually exhibited by unmodified calcium phosphate phases leads, on the one hand, to the formation of an apatite layer which has been positively valued up to now, but then also to the depletion of the surroundings of the biomaterial with respect to calcium ions; this can affect negatively the cells involved in remodeling and thus bone healing or new bone formation.

However, it is unambiguously clear that calcium phosphate-based materials are needed whose calcium binding and release behavior can be adjusted in a predetermined way.

In this connection, according to the current level of knowledge, metastable calcium phosphate phases, as for example tricalcium phosphate, bruschite, and octacalcium phosphate, are unsuitable because their dissolution behavior is too fast with respect to the bone healing process.

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