Scaffolds for Hard Tissue Engineering by Ionotropic Gelation of Alginate–Influence of Selected Preparation Parameters

Abstract

Cylindrical constructs with parallel aligned pores were prepared by using ionotropic gelation of alginate/calcium phosphate hydroxyapatite (HAP) mixtures in regard to applications as scaffold for bone regeneration. The starting powder and stabilizing agents were characterized by measurement of electrosonic amplitude, particle size distribution, and specific surface. The shrinkage of the gels was investigated in dependence on the drying methods. The pore size relied on preparation conditions such as amount of HAP and concentrations of gelling agent or alginate sol. A wide field of pore sizes could be fabricated by varying the kind and concentration of additives. Micro computer tomography-investigations of freeze dried scaffolds demonstrated the pore progression over a length of 4 mm. The pore dimension and structure were adequate for cell seeding and blood capillary ingrowth. Biocompatibility was proven by in vitro experiments with human mesenchymal stem cells by fluorescence microscopy. A high stability of the wet gels was maintained under cell culture conditions for a period of 3 weeks.

Novel Biomaterials with Parallel Aligned Pore Channels by Directed Ionotropic Gelation of Alginate: Mimicking the Anisotropic Structure of Bone Tissue

“…precipitation of calcium phosphate during the sol-gelprocess ), • HAP powder, i.e. addition of HAP powder to the alginate sol and structuring of this slurry via ionotropic gelation Dittrich et al, 2006;Dittrich et al, 2007;Bernhardt et al, 2009), • Biphasic but monolithic scaffolds for the therapy of osteochondral defects can be produced through deposition of sol layers differing in composition prior to the gelation .…”

“…The high amount of HAP introduced by addition of ceramic powder results in improved strength compared to the synchronously mineralised composites which was evaluated in wet state Bernhardt et al, 2009). All changes in composition of the sol or slurry prior to ionotropic gelation will influence the pore formation (diameter, length, density) during the sol-gel-process (Dittrich et al, 2007). However, the gel or composite with parallel aligned pores can be influenced after gelation by exposure to organic solvents benefiting of the different swelling behaviour.…”

“…butanol. Following the run of pore channels, this non destructive method also unveiled that pore channels can merge with distance from the primary membrane (Dittrich et al, 2007). A mineral gradient in the direction of the long axis of the pore channels can be obtained by carefully covering layers of alginate sol on top of each other which differ in composition .…”

“…in the incubator at 37°C/5%CO 2 and in cell culture medium (Bernhardt et al, 2009). Also the mechanical stability over time is differently affected by cell culture medium compared to water or PBS (Dittrich et al, 2007). The biocompatibility of alginate-gelatine-HAP composites with a pore diameter of approx.…”

A novel method for preparing Si 3 N 4 ceramics with unidirectional oriented pores from silicon aqueous slurries

“…In the meantime, the extrusion-induced defects, which are generated by the deformation of the ceramic paste, should be avoided as well [12]. Recently, a self-organization process was used to prepare highly unidirectional ceramics, including Al 2 O 3 , HAP and Si 3 N 4 [13][14][15]. Compared with common methods, this process was relatively complex, including the incorporation of inorganic particles into the gel matrix and ion exchange.…”