Design of Thermoresponsive Polyamine Cross-Linked Perfluoropolyether Hydrogels for Imaging and Delivery Applications

Perfluorocarbons are versatile compounds with applications in ¹⁹F magnetic resonance imaging (MRI) and chemical conjugation to drugs and pH sensors. We present a novel thermoresponsive perfluorocarbon emulsion hydrogel that can be detected by ¹⁹F MRI. The developed hydrogel contains perfluoro(polyethylene glycol dimethyl ether) (PFPE) emulsion droplets that are stabilized through ionic cross-linking with polyethylenimine (PEI). Specifically, PFPE ester undergoes hydrolysis upon contact with aqueous PEI solution, resulting in an ionic bond between the PFPE acid and charged PEI amino groups. Due to the ionic nature of the PFPE/PEI bond, potassium buffer is required to preserve the hydrogel's pH and rheological and emulsion droplet stability. The presence of the surface cross-linked PFPE droplets does not affect the hydrogel's rheological behavior, drug loading, or drug release, and the hydrogel is nontoxic. We propose that the presented hydrogel can be adapted to a broad range of biomedical imaging and delivery applications.