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.
In this work an injectable and self setting calcium phosphate/albumen foam is developed. The effect of both the amount of albumen and the particle size of the starting a-tricalcium phosphate (a-TCP) powder on the injectability of the cement paste is studied. X-ray diffraction (XRD) and infrared (IR) analysis of the samples reveal that the hydrolysis of a-TCP to calcium deficient hydroxyapatite (CDHA) is not affected by the addition of albumen. A foamed structure formed by spherical pores with diameters between 100 and 500 µm is observed by SEM. This
porous structure is maintained after injection of the paste, although some deformation of the pores is produced due to the extrusion process. The injectability of the cements is increased by the presence of albumen as compared with cements prepared in the same conditions but without foaming agent.
In this work, the preparation and characterization of a macroporous a-tricalcium phosphate (a-TCP) cement with albumen as foaming agent is discussed. X-ray diffraction (XRD) and infrared (IR) analysis of the samples reveal that the conversion of a-TCP to calcium deficient hydroxyapatite (CDHA) was not affected by the addition of albumen in the cement paste. SEM observations showed the formation of spherical macropores with diameters between 100 and 500 mm. The use of phosphate solutions, which have an accelerating effect of the setting reaction, influenced the foam stability, reducing the macroporosity of the set cements.
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