Macropore Regulation of Hydroxyapatite Osteoinduction via Microfluidic Pathway

Abstract

Macroporous characteristics have been shown to play a key role in the osteoinductivity of hydroxyapatite ceramics, but the physics underlying the new bone formation and distribution in such scaffolds still remain elusive. The work here has emphasized the osteoinductive capacity of porous hydroxyapatite scaffolds containing different macroporous sizes (200–400 μm, 1200–1500 μm) and geometries (star shape, spherical shape). The assumption is that both the size and shape of a macropore structure may affect the microfluidic pathways in the scaffolds, which results in the different bone formations and distribution. Herein, a mathematical model and an animal experiment were proposed to support this hypothesis. The results showed that the porous scaffolds with the spherical macropores and large pore sizes (1200–1500 μm) had higher new bone production and more uniform new bone distribution than others. A finite element analysis suggested that the macropore shape affected the distribution of the medium–high velocity flow field, while the macropore size effected microfluid speed and the value of the shear stress in the scaffolds. Additionally, the result of scaffolds implanted into the dorsal muscle having a higher new bone mass than the abdominal cavity suggested that the mechanical load of the host tissue could play a key role in the microfluidic pathway mechanism. All these findings suggested that the osteoinduction of these scaffolds depends on both the microfluid velocity and shear stress generated by the macropore size and shape. This study, therefore, provides new insights into the inherent osteoinductive mechanisms of bioceramics, and may offer clues toward a rational design of bioceramic scaffolds with improved osteoinductivity.

Prioritizing Biomaterial Driven Clinical Bioactivity Over Designing Intricacy during Bioprinting of Trabecular Microarchitecture: A Clinician’s Perspective

“…Microporous hydroxyapatite (HA) scaffolds with 0.4 μm pore sizes exhibit osteogenic potential, as hydroxyapatite nanocrystals display superior adsorption of albumin and fibronectin. − Further, it is also observed that structural design influences bioactivity; concave scaffolds induce bone formation within pores and its concave surfaces, while osteoblasts preferentially attach to grooved scaffold surfaces . Microporosities not only enhance the surface area for protein adsorption but also induce capillarity, anchoring, and accommodating cells within micropores, even if their dimension is slightly smaller than the cell …”

Recent Advances in Bioengineering Bone Revascularization Based on Composite Materials Comprising Hydroxyapatite

“…In contrast, the pore size should ideally be greater than 200 µm or even greater than 250 µm to facilitate internal bone growth and the colonization and proliferation of osteoblasts within the large pores [87]. Leet et al found that a scaffold with 500 µm macroporous pores produced more osseointegration and bone regeneration than a scaffold with 250 µm macroporous pores in vivo [88][89][90]. Graphene oxide-hydroxyapatite (GO-HAP) is a 2D nanocomposite prepared by in situ bonding.…”

Fabrication of biomimetic scaffold through hybrid forming technique

“…6 Given the similarities with natural bone chemistry, osteoinductive bioceramic materials have inspired the interest of researchers. 7,8 Moreover, bioceramics have good surface characteristics including roughness, dispersion, and porosity, and they might contribute to osteoblast adhesion and proliferation, hence promoting osteogenesis. 9 Calcium phosphates in the form of hydroxyapatite (HA) are an excellent material option for the preparation of 3D porous scaffolds in bone tissue engineering.…”