Importance of Biomaterials In Vivo Microenvironment pH (μe-pH) in the Regeneration Process of Osteoporotic Bone Defects

In scenario of osteoporotic fracture, significantly higher activity of osteoclasts than osteoblasts may lead to continuous loss of bone in fracture/defect site. Impaired bone regeneration efficiency is the major barrier that influences endosseous implants to get a better performance, and this substantially increases the risk of a second fracture, nonunion, and aseptic implant loosening. Although great effects have been made, there are still no clinically approved biomaterials specifically tailored for applications in osteoporotic bones. The key issue for developing such biomaterials is to reestablish normal bone regeneration at the fracture site. Acid-base property could directly influence the behavior of bone cells, thus making it an important factor to modulate the unbalanced activity between osteoclast and osteoblast in osteoporotic conditions. More importantly, it is adjustable through implant biodegradation. Therefore, a rational strategy to reconstruct the regeneration balance in the fracture site is to regulate the microenvironmental pH (μe-pH) through the application of biodegradable materials. The present chapter provides an overview on how pH change influences bone cells behaviors as well as recent development on revealing the role of μe-pH in guiding the localized bone regeneration. We proposed that the μe-pH is an important and accessible factor which should be taken into consideration in the development of orthopedic biomaterials, in particular for repair of osteoporotic bone fracture/defect.