Factors affecting the structure and properties of an injectable self‐setting calcium phosphate foam

Abstract

One of the main challenges in the investigation on calcium phosphate cements (CPC) lies in the introduction of macroporosity, without loosing the self-setting ability and injectability, characteristic of the cement-type materials. The benefits of macroporosity are related to the enhancement of bone regeneration mechanisms, such as angiogenesis and tissue ingrowth. In this work, the feasibility to obtain self-setting injectable macroporous hydroxyapatite foams by the incorporation of a protein-based foaming agent to a CPC is demonstrated. Albumen is combined with an alpha-tricalcium phosphate [Ca3(PO4)2, alpha-TCP] paste, which hydrolyzes to a calcium deficient hydroxyapatite during the setting reaction. A systematic study is presented, where the effect of different processing parameters is analyzed in terms of porosity, setting properties, injectability, and compressive strength. Self-setting foams with porosities up to 70%, which maintain their porous structure after injection, are obtained. These injectable foams can be used both for direct in vivo applications and for the fabrication of low temperature tissue engineering scaffolds.

Biomaterials in orthopaedics

“…In addition, BG-ceramics elaborated from CaP degradable glasses as well as BGs, and CPC foams have been used as templates for in situ regeneration with very promising results (Gong et al 2001;Yuan et al 2001;Almirall et al 2004;Navarro et al 2004a;Ginebra et al 2007).…”

An evaluation of methods to determine the porosity of calcium phosphate cements

“…The CPCs that have been tested with this method have so far mostly been basic CPCs. 3,11,12 Solvent resaturation is a method that is commonly used for other types of porous materials. 5,7 In this method, dry samples are immersed in a solvent, normally water or alcohol and the weight change is monitored until a constant weight is achieved.…”

“…For CPCs, mainly three methods are utilized: helium pycnometry, [8][9][10] mercury intrusion porosimetry (MIP), 3,11,12 and using the tabulated density value of the material 11,[13][14][15] to calculate the porosity. The main drawbacks of these methods are the destructiveness, the long analysis times and the need for special equipment, especially for MIP and helium pycnometry, which may entail that fewer samples are analyzed, compromising statistical power.…”

Self-Setting Calcium Orthophosphate Formulations: Cements, Concretes, Pastes and Putties

“…Further, the setting reactions of a calcium orthophosphate cement transforms the liquid foam into a solid, which ideally maintains the geometry, size and shape of the bubbles of the liquid foam. Thus, the liquid foam acts as a template for the macroporosity of the solid foam [333,334]. In addition, several other porosity creation techniques in calcium orthophosphate cements are known and, for further details on the subject, the interested readers are referred to an excellent review [327].…”