Alginate-calcium composites: advances in design, functional properties, and applications in biomedicine and...

Alginate-Ca²⁺ composites are produced by connecting alginate with calcium through ionic crosslinking and represent extremely useful biomaterials because of their versatility, tunable mechanical properties, swelling characteristics, and degradation rates. Research is presently directed toward improving composite performance and functionality through the use of nanoparticles (e.g., hydroxyapatite, clay, and magnetic) to produce nanocomposites, blending them with other polymers, and using new fabrication techniques such as 3D printing and microfluidics. These engineered composites exhibit better mechanical properties and controlled release kinetics and are also biocompatible and environmentally friendly, while displaying unique properties from the alginate-Ca²⁺ interaction. Therefore, there are many biomedical applications for these composites, including the use of alginate-Ca²⁺ composites as an effective wound-healing dressing, as a drug and/or cell delivery vehicle, and as a scaffold for tissue engineering, particularly for the regeneration of bone and cartilage. In addition, the high density of carboxylic functional groups and porous structure in alginate-Ca²⁺ composites allow them to adsorb heavy metals, dyes, organics, etc., making them a potentially environmentally friendly material for water remediation and for microbial immobilization in bioreactors. This review paper will discuss the structure/property relationship that governs the performance of composites, outline new design strategies based on recent developments, and indicate barriers to successful translation into practice for both clinical and environmental applications, including 1) issues of scale-up, 2) stability in complex solutions, and 3) the regulatory process.