Multifunctional CaSiO3/Calcium alginate microcarriers loaded with tea tree oil for antibacterial and osteogenic applications

• Composite microcarriers were fabricated by emulsion-based ionic crosslinking. • 97% encapsulation efficiency and 240 h sustained release of TTO were achieved. • CaSiO 3 enhanced mineralization, cell proliferation, and apatite formation. • All microcarriers showed >96% antibacterial activity against E. coli for 96 h. • Formulations can be tailored for acute infection or long-term bone regeneration. . A multifunctional composite microcarrier system (TTO@CSi/CA) is successfully developed for bone repair applications, integrating antimicrobial, osteoconductive, osteoinductive, and controlled drug delivery properties. The microcarriers are fabricated via emulsion-based ionic crosslinking, encapsulating tea tree oil (TTO) within a calcium alginate matrix and reinforcing the structure with bioactive CaSiO 3 . By adjusting CaCl 2 concentrations (1-3%) and CaSiO 3 content (10-50 mol%), the microcarrier morphology, drug loading efficiency, release kinetics, and biological performance of the microcarriers are optimized. CaSiO 3 enhances structural integrity and bioactivity, while CaCl 2 concentration significantly influences shell formation, shrinkage behavior, and encapsulation efficiency. The optimized formulation (TTO@C2-CSi20), containing 2% CaCl 2 and 20% CaSiO 3 , achieves the highest encapsulation efficiency (97%) and loading capacity (76.7%), along with a sustained TTO release up to 240 hours. Antibacterial assays demonstrate >96% inhibition of E. coli DH5α over 96 hours, while MG-63 cell viability is promoted across all formulations. Simulated body fluid immersion confirms apatite formation, and Alizarin Red S staining reveals enhanced mineralization, particularly for TTO@C3-CSi20. Depending on therapeutic needs, microcarriers can be tailored for acute infection control (TTO@C1-CSi20), balanced healing (TTO@C2-CSi20), or long-term support (TTO@C3-CSi20). This work presents a customizable strategy for designing bioactive and antimicrobial microcarriers, offering promising potential in infection-resistant bone regeneration therapies.