Cancer theranostic platforms based on injectable polymer hydrogels.

Theranostic platforms combining therapy with diagnosis not only prevent the undesirable biological responses that may occur when these processes are conducted separately, but also supply individualized therapies for patients. Polymer hydrogels have been employed to provide well-controlled drug release and targeted therapy in theranostics, where injectable hydrogels enable non-invasive treatment and monitoring with one single injection, offering a great comfort and efficient therapy. Efforts have been dedicated to applying injectable polymer hydrogels in theranostic research and clinical use. This review highlights recent progress in the design of injectable polymer hydrogels for theranostics, particularly focusing on the elements/components of theranostic hydrogels, and their cross-linking strategies, structures, as well as performances in drug delivery/tracking. In the present review, therapeutic agents and tracking modalities which are essential components of the theranostic platforms are first introduced, followed by the design strategies, properties and applications of the injectable hydrogels developed via two approaches: chemical bonds and physical interactions. The theranostic functions of the platforms are highly dependent on the architectures and components employed for the construction of hydrogels. Finally, current challenges of the theranostic platforms based on injectable hydrogels are identified and prospects of acquiring more comfortable and personalized therapies are proposed.