Injectable Cryogels for Biomedical Applications

To prevent postoperative complications, there has been a substantial interest in designing syringe-injectable hydrogels. To date, cryogels remain the only viable option for preformed and large-scale hydrogels to be delivered through a conventional needle–syringe injection. Cryogels, a type of hydrogel with exceptional features, are fabricated at subzero temperatures. This process typically results in a biomaterial with a unique macroporous network, shape-memory properties, and exceptional flexibility allowing syringe injectability. These advanced biomaterials have been used for a number of biomedical applications, including tissue engineering, drug delivery, and more recently, immunotherapy. This review summarizes the recent progress on the design of injectable cryogels, their current limitations, and strategies to further improve their properties for translatability into the clinic. Injectable cryogels were disclosed in 2012 as the first preformed large-scale hydrogels to be injected through a conventional hypodermic syringe, obviating the need for invasive surgical implantations.Injectable cryogels have shape-memory properties and are reversibly compactible.When syringe injected, shear-collapsed cryogels flow through conventional needles. Once released, cryogels instantly pop back to their initial shape and size.Cryogels with their inherent interconnected macroporous network can host and/or deliver mammalian cells for tissue regeneration, cell transplantation, and in situ cell manipulation/reprogramming.Biomolecules can be efficiently entrapped within the dense polymer walls of cryogels. Fine-tuning cryogel properties can control the spatiotemporal release of their payloads.Enhancing cryogel properties will expand their potential in the biomedical field.