Living-loaded hydrogel: Strategies for loading living, interactions between loaded living and hydrogel, and applications

In natural settings, most live organisms lack a protective and structured shell and show susceptibility to harsh external environments. Hydrogels are a versatile category of biomaterials that exhibit excellent biocompatibility, remarkable water retention, high swelling properties and the capability to faithfully replicate the structure of extracellular matrix. Three-dimensional (3D) hydrogel networks have a unique microstructure that confers distinct advantages for the encapsulation of live organisms and expands their potential applications. The addition of living endows the hydrogel with more advanced functions, and the two interact with each other. By engineering living and non-living substrates, we can create materials that sense changes in their environment and adjust their functions accordingly. This review provides a comprehensive overview of studies on strategies for the loading of living within hydrogels, the interactions between loaded living beings and hydrogels and their applications in wound dressings, tissue engineering, 3D bioprinting and living delivery. Furthermore, the challenges and prospects associated with the application of hydrogels loaded with living were analysed, which is conducive to further investigations and their utilisation in the future.