Natural Polymers with Bioactive Glass Additives for Bone Regeneration: Chemistry and Trends

Natural polymers, such as chitosan (CH) and gelatine (GE), have a wide range of uses in biological environments. This is primarily attributed to their biocompatibility and the body’s recognition of them being as “self” as opposed to “foreign”. These polymers provide a dynamic and cell-friendly interaction environment which is a crucial factor for tissue repair and regeneration. Bone regeneration is a highly intricate multistep process involving a plethora of biomolecules, signalling pathways, and stages in cellular activity. Critically-sized bone defects do not regenerate without an implant due to the cessation of the cellular stimulus associated with new bone formation. Therefore, natural polymers have been combined with bioactive glasses (BGs) to provide a biocompatible delivery matrix and to stimulate bone formation via the release of osteogenic ions from the BG particles. The addition of BG particles in natural polymers has been shown not only to result in an osteogenic response at a cellular level but also result in per se formation of hydroxyapatite (HA) on implant surfaces and regeneration of new bone in vivo. This review discusses the recent trends over the last decade in this field, keeping a focus on the chemistry and properties of CH and GE composites containing a bioactive glass additive.