Chapter 4: Naturally Occurring and Nature-derived Polymers as Injectable Hydrogels

Hydrogels from naturally occurring polymers have been the focus of intense research for many decades, in an effort to mimic the complex and hierarchical structure of biological tissues. One of the main reasons for this interest is that they can offer to cells a highly hydrated environment and many similarities with their native extracellular matrix, both in structure and chemistry. When hydrogels are intended for cell embedding or in vivo injection, naturally occurring materials also have on their side unparalleled gelation mechanisms, with sol–gel transition entailing only minimal deviation from cells ideal conditions. Although derivatives of natural materials have attracted enormous research efforts for the fine-tuning of their properties, this chapter largely focuses on unmodified biopolymers with a sol–gel transition suitable for injection and cell encapsulation and on their gelation properties in particular.