Repurposing biowaste for biomedical applications: Eggshell containing injectable bone substitution cements for bone regeneration

Bone tissues play an important role in the human body by providing structural support, protecting internal organs, enabling locomotion, and storing vital minerals. However, bone damage due to trauma, disease, or other factors can lead to defects that require surgical intervention. Traditional bone grafting methods, such as autografts, allografts, and xenografts, have limitations including limited donor sites, risk of host rejection, and disease transmission. This has led to a growing demand for synthetic bone substitutes that promote bone regeneration. Synthetic bone scaffolds and cements are used to address bone defects, but face challenges with bio-inertness, which can slow tissue regeneration. Injectable bone cement, often used as an alternative to solid scaffolds, provides a higher mechanical strength than foams and fills irregularly shaped defects during surgery. However, many bone cements lack bioactivity, which hinders the bone regeneration process. This review explores the use of eggshells as an additive in injectable bone cement to enhance bioactivity. The unique composition of eggshells, including calcium carbonate and vital trace elements such as fluorine, sodium, and potassium, offers potential benefits for stimulating bone regeneration. This review also evaluates the effectiveness of eggshell additives in promoting bone regeneration, and identifies future research directions.