Bio-based composite hydrogels for biomedical applications

Hydrogels are three-dimensional, water-swollen polymer networks that have been widely studied for biomedical applications such as tissue engineering and the controlled delivery of biologically active agents. Since the pioneering work of Wichterle and Lim in the 1960s, hydrogel research has shifted from relatively simple single polymer networks to multifunctional composite hydrogels that better mimic the complex nature of living tissues. Bio-based polymers, which can be obtained from renewable natural resources, are attracting increasing attention for use in biomaterials due to the recent demands for a reduction in the environmental impact of the polymer industry and the development of a sustainable society. Moreover, bio-based polymers are often biodegradable and exhibit a significant level of biocompatibility and biomimicry, which are highly desired properties with regard to in vivo application. This review presents the state-of-the-art in the field of bio-based composite hydrogels for biomedical applications, thereby focusing on different types of polymeric components that have been combined with hydrogels to obtain materials with unique, synergistic properties: particles (including micelles and microspheres), electrospun fibres and nanocellulose. In addition, the challenges are described that should be overcome to facilitate clinical application of these versatile and environmentally responsible biomaterials.