Synthesis of Biocompatible PEG Hydrogels by pH-Sensitive Potassium Acyltrifluoroborate (KAT) Amide Ligations

The synthesis of novel PEG-based hydrogel via chemoselective potassium acyl trifluoroborate (KAT) and O-carbamoyl hydroxylamines amide ligation is reported. The gelation kinetics, determined by dynamic rheometry, is pH dependent and allows fine-tuning of the gelation time. For a 4 wt % PEG hydrogel, at low acidic pHs (3 to 6) gelation proceeds rapidly within few minutes, comparable or existing the faster known gelation times. At neutral and physiological pHs (7 and 7.4) the reaction is slower, forming a hydrogel in ca. 80 min. The gels are suitable for the encapsulation of bovine chondrocytes with the high viability (96% after 2 days), demonstrating the biocompatibility of the KAT ligation for the first time.