Multicomponent chemically and physically cross-linked hydrogels

Abstract

Hydrogels are an emerging class of functional and tunable biomaterials. The hydrogel network can be maintained by chemical or physical interactions that are established between polymeric chains. The aim of this work is to develop polyethylene glycol (PEG)-based hydrogels using innovative methods based on chemical and physical interactions. A new chemical strategy for the production of hydrogels using a multicomponent reac-tion was shown for the first time. Here, 4-arm star-shaped PEG molecules, with suitable end functionalities, were used to form mechanically stiff chemically cross-linked hydrogels. The possibility of incorporating different molecular moieties into the network allowed the creation of functional and tunable hydrogels. The other approach of the work focused on physically cross-linked hydrogels. Here, the interaction between two affinity pairs was exploited to form physically crosslinked hydrogels. The first affinity pair studied was a peptide-inspired WW domain and its natural binding partner (PPxY peptide). Multivalency was created by conjugating both components of the affinity pair into 8-arm star-shaped PEG polymers. Once mixed, a new soft affinity-triggered assembly was formed, and the mechanical properties of these hydrogels were character-ized, and shown to be similar to hydrogels that contain the full version of the WW peptide in tandem. The second affinity pair studied was the Green Fluorescent Protein (GFP) and a de novo designed ligand. In this case, multivalency was generated by the tandem arrangement of GFP in 3 and 5 repeats. GFP in tandem was intercalated with a hydrophilic spacer and recombinantly expressed in two E. coli strains. The obtained crude extracts were further processed to purify the GFP protein using immobilized metal affinity chromatography, anion exchange and size-exclusion chromatography.