Microporous calcium phosphate ceramics driving osteogenesis through surface architecture

Abstract

The presence of micropores in calcium phosphate (CaP) ceramics has shown its important role in initiating inductive bone formation in ectopic sites. To investigate how microporous CaP ceramics trigger osteoinduction, we optimized two biphasic CaP ceramics (i.e., BCP-R and BCP-S) to have the same chemical composition, equivalent surface area per volume, comparable protein adsorption, similar ion (i.e., calcium and phosphate) exchange and the same surface mineralization potential, but different surface architecture. In particular, BCP-R had a surface roughness (Ra) of 325.4 ± 58.9 nm while for BCP-S it was 231.6 ± 35.7 nm. Ceramic blocks with crossing or noncrossing channels of 250, 500, 1000, and 2000 µm were implanted in paraspinal muscle of dogs for 12 weeks. The percentage of bone volume in the channels was not affected by the type of pores (i.e., crossing vs. closed) or their size, but it was greatly influenced by the ceramic type (i.e., BCP-R vs. BCP-S). Significantly, more bone was formed in the channels of BCP-R than in those of BCP-S. Since the two CaP ceramics differed only in their surface architecture, the results hereby demonstrate that microporous CaP ceramics may induce ectopic osteogenesis through surface architecture.

Muscle as an osteoinductive niche for local bone formation with the use of a biphasic calcium sulphate/hydroxyapatite biomaterial

“…It has already been reported that heterotopic bone formation was induced in the presence of micropores in ceramic materials. 35,36 Porous HA-CS and HA-CS-G scaffolds provide sufficient surface area for cellular attachment and also an efficient environment for exchange of nutrients, gases and other signalling molecules. Cells were uniformly distributed across the surface of the scaffold as observed from SEM and DAPI analysis (Figs 3c to 3f).…”

Calcium orthophosphate bioceramics

“…Thus, the aim of CaPO 4 is to prepare artificial porous bioceramic scaffolds able to provide the physical and chemical cues to guide cell seeding, differentiation and assembly into 3D tissues of a newly formed bone. Particle sizes, shape and surface roughness of the scaffolds are known to affect cellular adhesion, proliferation and phenotype [707,[818][819][820][821][822][823]. Additionally, the surface energy might play a role in attracting particular proteins to the bioceramic surface and, in turn, this will affect the cells affinity to the material.…”

“…Nevertheless, besides the specific genetic factors [688] and chosen animals [690], the dissolution/precipitation behavior of CaPO 4 [700], their particle size [699], microporosity [686,690,701,702], physicochemical properties [684,686], composition [690], the specific surface area [702], nanostructure [689], as well as the surface topography and geometry [685,[703][704][705][706][707] have been pointed out as the relevant parameters. A positive effect of increased microporosity on the ectopic bone formation could be both direct and indirect.…”

“…Firstly, an increased microporosity is directly related to the changes in surface topography, i.e. increases a surface roughness, which affects the cellular differentiation [707].…”

Preclinical testing of drug delivery systems to bone

“…The sintering temperature of the calciumphosphates, the pressure and the porosity gives each material its own characteristics. Therefore, they exert different actions in bone regeneration [90][91][92].…”