Hydrogels with reversible cross‐links for improved localised stem cell retention: a review

Successful stem cell applications could significantly impact the medical fields, where many lives are at stake. However, the translation of stem cells to the clinic could be improved by challenges in stem cell transplantation and in vivo retention at the site of tissue damage.  This review aims to provide the most recent insights into developing hydrogels that can deliver, retain, and accommodate stem cells for tissue repair. Hydrogels can be used for tissue engineering as their flexibility and water content makes them excellent substitutes for the native extracellular matrix. Moreover, the mechanical properties of hydrogels are highly tuneable, and recognition moieties to control cell behaviour and fate can quickly be introduced. This review covers the parameters necessary for the physicochemical design of adaptable hydrogels, the variety of (bio)materials that can be used in such hydrogels, their application in stem cell delivery and some recently developed chemistries for reversible cross-linking. Implementing physical and dynamic covalent chemistry has resulted in adaptable hydrogels that can mimic the dynamic nature of the extracellular matrix.