Biodegradable and injectable polymer–liposome hydrogel: a promising cell carrier

Biodegradable and injectable hydrogels are widely used in many important applications such as cell culturing, tissue engineering, drug delivery, and cell therapy. Here we developed an inexpensive and facile method to prepare a biodegradable and injectable polymer–liposome hydrogel using aldehyde modified xanthan gum (ALD-XA) as a matrix material and phosphatidylethanolamine (PE) liposomes as cross-linkers. To the best of our knowledge, this is the first time hydrogels containing crosslinked lipid liposomes have been prepared. The hydrogel was formed through dynamic Schiff base linkages between aldehyde groups of ALD-XA and amino groups of PE liposomes. After mixing ALD-XA and PE liposome solutions, the xanthan gum-based liposome hydrogel could be rapidly prepared within 5 min at room temperature. Owing to the dynamic equilibrium of the Schiff base bonds, the hydrogel responds to various stimuli, including physical stimulus (heat), chemical stimulus (pH variation), and biological stimulus (histidine exposure). Additionally, the hydrogel could easily be biodegraded by papain as a result of the digestion of xanthan gum backbones by enzymes. The hydrogel also exhibits excellent self-healing capability. Cells encapsulated in the prepared hydrogel are viable for a long period of time, indicating that it is an excellent carrier material suitable for three-dimensional (3D) cell culturing. These advantages suggest that the xanthan gum-based liposome hydrogel is a promising candidate as a smart cell carrier for cell therapy and as an excellent cell culturing scaffold for tissue engineering.