Tailored cobalt ferrite nanostructures: synthesis, characterization, multifunctional performance, and toxicity evaluation for biomedical applications

CoFe₂O₄ (CFO) nanoparticles (NPs) have emerged as a promising class of magnetic nanomaterials for next generation theranostic applications owing to their high magneto crystalline anisotropy, superior chemical stability, tunable magnetic behaviour, and multifunctional biomedical capabilities. Despite extensive research, a comprehensive understanding of how synthesis strategies, structural engineering, and surface functionalization collectively govern their biological performance remains lacking. This review addresses this gap by providing a critical structure–property–function framework that links synthesis-controlled parameters including particle size, morphology, crystallinity, cation distribution, and defect chemistry to magnetic characteristics, colloidal stability, biocompatibility, and therapeutic efficacy. Particular emphasis is placed on advanced surface engineering approaches, including polymeric, silica-based, biomimetic, and ligand-assisted functionalization strategies that enable enhanced circulation stability, immune evasion, targeted delivery, and multimodal imaging. Beyond summarizing recent progress in magnetic hyperthermia, magnetic resonance imaging, drug delivery, biosensing, antimicrobial, and anticancer applications, this review critically evaluates the limitations associated with toxicity, biodegradation, biodistribution, reproducibility, and large-scale manufacturing. By integrating physicochemical design principles with biological outcomes and translational considerations, the review provides actionable guidelines for the rational development of clinically relevant CFO-based nanomedicines and identifies key research priorities for accelerating their transition from laboratory studies to biomedical practice.