Structure and Properties of Bioactive Glass-Modified Calcium Phosphate/Calcium Sulfate Biphasic Porous Self-Curing Bone Repair Materials and Preliminary Research on Their Osteogenic Effect

Current and Future Perspectives of Bioactive Glasses as Injectable Material

This review covers recent compositions of bioactive glass, with a specific emphasis on both inorganic and organic materials commonly utilized as matrices for injectable materials. The major objective is to highlight the predominant bioactive glass formulations and their clinical applications in the biomedical field. Previous studies have highlighted the growing interest among researchers in bioactive glasses, acknowledging their potential to yield promising outcomes in this field. As a result of this increased interest, investigations into bioactive glass have prompted the creation of composite materials and, notably, the development of injectable composites as a minimally invasive method for administering the material within the human body. Injectable materials have emerged as a promising avenue to mitigate various challenges. They offer several advantages, including minimizing invasive surgical procedures, reducing patient discomfort, lowering the risk of postoperative infection and decreasing treatment expenses. Additionally, injectable materials facilitate uniform distribution, allowing for the filling of defects of any shape.

Limitations and modifications in the clinical application of calcium sulfate

Calcium sulfate and calcium sulfate-based biomaterials have been widely used in non-load-bearing bone defects for hundreds of years due to their superior biocompatibility, biodegradability, and non-toxicity. However, lower compressive strength and rapid degradation rate are the main limitations in clinical applications. Excessive absorption causes a sharp increase in sulfate ion and calcium ion concentrations around the bone defect site, resulting in delayed wound healing and hypercalcemia. In addition, the space between calcium sulfate and the host bone, resulting from excessively rapid absorption, has adverse effects on bone healing or fusion techniques. This issue has been recognized and addressed. The lack of sufficient mechanical strength makes it challenging to use calcium sulfate and calcium sulfate-based biomaterials in load-bearing areas. To overcome these defects, the introduction of various inorganic additives, such as calcium carbonate, calcium phosphate, and calcium silicate, into calcium sulfate is an effective measure. Inorganic materials with different physical and chemical properties can greatly improve the properties of calcium sulfate composites. For example, the hydrolysis products of calcium carbonate are alkaline substances that can buffer the acidic environment caused by the degradation of calcium sulfate; calcium phosphate has poor degradation, which can effectively avoid the excessive absorption of calcium sulfate; and calcium silicate can promote the compressive strength and stimulate new bone formation. The purpose of this review is to review the poor properties of calcium sulfate and its complications in clinical application and to explore the effect of various inorganic additives on the physicochemical properties and biological properties of calcium sulfate.

Enhanced Cell Osteogenic Differentiation in Alendronate Acid and Flufenamic Acid Drug-Impregnated Nanoparticles of Mesoporous Bioactive Glass Composite Calcium Phosphate Bone Cement In Vitro

This study aims to compare the anti-osteoporotic drugs alendronic acid (ALN) and flufenamic acid (FA) alone impregnate into nanoparticles of mesoporous bioactive glass (nMBG), which further composites calcium phosphate cement (CPC) and investigates their in vitro performance. The drug release, physicochemical properties, and biocompatibility of nMBG@CPC composite bone cement are tested, and the effect of the composites on improving the proliferation and differentiation efficiency of mouse precursor osteoblasts (D1 cells) is also investigated. Drug release shows that FA impregnates nMBG@CPC composite, a large amount of FA is released rapidly within 8 h, gradually reaching a stable release within 12 h, followed by a slow and sustained release within 14 days, and then reaches a plateau within 21 days. The release phenomenon confirms that the drug-impregnated nBMG@CPC composite bone cement effectively achieves slow drug delivery. The working time and setting time of each composite are within 4-10 min and 10-20 min, respectively, meeting the operational requirements of clinical applications. The addition of nMBG nanoparticles in the CPC matrix did not prevent the aggregation phenomenon under microstructural observation, thus resulting in a decrease in the strength of the nMBG@CPC composite. However, after 24 h of immersed reaction, the strength of each 5 wt.% nMBG impregnated with different concentrations of FA and ALN is still greater than 30 MPa, which is higher than the general trabecular bone strength. The drug-impregnated nMBG@CPC composites did not hinder the product formation and exhibit biocompatibility. Based on the proliferation and mineralization of D1 cells, the combination of nMBG with abundant FA and ALN in CPC is not conducive to the proliferation of D1 cells. However, when D1 cells are contact cultured for 21 days, alkaline phosphatase (ALP) enzyme activity shows higher ALP secretion from drug-impregnated nMBG@CPC composites than drug-free composites. Accordingly, this study confirms that nMBG can effectively impregnate the anti-osteoporosis drugs FA and ALN, and enhance the mineralization ability of osteoblasts. Furthermore, drug-impregnated nMBG applications can be used alone or in combination with CPC as a new option for osteoporotic bone-filling surgery.