Alginates as a useful natural polymer for microencapsulation and therapeutic applications

This review outlines the role of alginates in microencapsulation and therapeutic applications. It focuses on the physicochemical properties of alginates (e.g. viscosity, thermo-stability, sol–gel transformation and drug release) to gain better insight into their potential medical applications, particularly for wound care and therapeutics. In order to understand how alginates can be optimized as a useful delivery system for therapeutic applications, various factors that impact drug release from alginate matrices (e.g. types of cations used in cross-linking, porosity of alginate matrices, pH effect, alginate composition, molecular weight of encapsulated drugs and modification of the functional groups in alginates) are also discussed. More specifically, practical applications of the cross-linking mechanism and sol–gel transformation property of alginates are explored to assess their potential to improve the mechanical properties of alginate dressings, to impart anti-microbial properties for treating wound infections and to develop products for tissue repair and wound healing. Innovative processes of developing alginate carriers and delivery systems and their recent applications are also discussed. Strategies employed to improve gelation of alginates commonly target the formulation by the inclusion of non-gelling cations or sequestrants during cross-linking. The application of other strategies, such as hot-made alginate gel method, in situ gelation method, crystal gun method, acoustic excitation method, and the use of extrusion devices with improved design are reviewed.

► Alginates can be crosslinked with various cations to modify the characteristics of the resultant matrices for different applications.
► New strategies have been successfully employed to improve the gelation mechanism of alginates.
► Innovative wound dressings with haemostatic, absorbent and antimicrobial properties have been developed.
► A number of patents involving alginate formulations for cell transplant have emerged.
► Alginates can be employed for rapid, as well as prolonged delivery of bioactive compounds.