Porous Nanomaterials Targeting Autophagy in Bone Regeneration

Abstract

Porous nanomaterials (PNMs) are nanosized materials with specially designed porous structures that have been widely used in the bone tissue engineering field due to the fact of their excellent physical and chemical properties such as high porosity, high specific surface area, and ideal biodegradability. Currently, PNMs are mainly used in the following four aspects: (1) as an excellent cargo to deliver bone regenerative growth factors/drugs; (2) as a fluorescent material to trace cell differentiation and bone formation; (3) as a raw material to synthesize or modify tissue engineering scaffolds; (4) as a bio-active substance to regulate cell behavior. Recent advances in the interaction between nanomaterials and cells have revealed that autophagy, a cellular survival mechanism that regulates intracellular activity by degrading/recycling intracellular metabolites, providing energy/nutrients, clearing protein aggregates, destroying organelles, and destroying intracellular pathogens, is associated with the phagocytosis and clearance of nanomaterials as well as material-induced cell differentiation and stress. Autophagy regulates bone remodeling balance via directly participating in the differentiation of osteoclasts and osteoblasts. Moreover, autophagy can regulate bone regeneration by modulating immune cell response, thereby modulating the osteogenic microenvironment. Therefore, autophagy may serve as an effective target for nanomaterials to facilitate the bone regeneration process. Increasingly, studies have shown that PNMs can modulate autophagy to regulate bone regeneration in recent years. This paper summarizes the current advances on the main application of PNMs in bone regeneration, the critical role of autophagy in bone regeneration, and the mechanism of PNMs regulating bone regeneration by targeting autophagy.

Bioactive core–shell structure of TiC/TiO2/SrCO3 coating on carbon black particles for bone tissue formation: Fabrication, characterization, and biological functions

“…Importantly, the hydrophilicity and nanotopography of the nanocomposite particles are also crucial properties enhancing their bioactive functions as reported by previous studies 49,50 . Ceramic particles acted as a template for the attachment of calcium secreted from osteoblast cells during bone tissue formation, whereas the hydrophilic particles with rough surfaces acted as preferential substrates for calcium deposition.…”

“…Importantly, the hydrophilicity and nanotopography of the nanocomposite particles are also crucial properties enhancing their bioactive functions as reported by previous studies. 49,50 Ceramic particles acted as a template for the attachment of calcium secreted from osteoblast cells during bone tissue formation, whereas the hydrophilic particles with rough surfaces acted as preferential substrates for calcium deposition. In the current research, the results demonstrated that the nanocomposite particles, especially the SrHT250, with high hydrophilicity and favored nanotopography, had a greater calcium deposition than those having poorer hydrophilicity and roughness.…”

Hydroxyapatite-based carriers for tumor targeting therapy

“…Compared with allogeneic bone and bone gras, HAP-based drug carriers usually bind well to the surrounding host bone and promote the formation of new bone, combine with new bone, and recover the damaged bone tissue. 146 Dexamethasone (DEX)-loaded polylactic acid-glycolic acid (PLGA) microspheres were immobilized on the surface of HAP scaffolds. This composite HAP scaffold can enhance bone regeneration in vivo.…”

Current Methods in the Study of Nanomaterials for Bone Regeneration

“…Autophagy promotes the circulation of cellular components and provides energy to starving cells while simultaneously removing damaged proteins and organelles. Such functions are essential for osteocyte differentiation and immune cell polarization and are thought to play a central role in bone regeneration [ 36 ] ( Figure 3 ).…”

“… Schematic of autophagy-derived regulation in the differentiation/function of osteoclasts/osteoblasts and osteoimmunology. Reprinted from reference [ 36 ]. M1, M1 macrophage; M2, M2 macrophage; IL-6, interleukin 6; iNOS, inducible nitric oxide synthase; IL-10, interleukin 10; TGF-β, transforming growth factor-beta; RANKL, receptor activator of nuclear factor-κB ligand; BMSC, bone marrow stem cell.…”