Sustained release of human growth hormone from in situ forming hydrogels using self-assembly of fluoroalkyl-ended poly(ethylene glycol)

Poly(ethylene glycol)s modified with fluorocarbon end groups are capable of in situ transition from an injectable liquid to a viscoelastic hydrogel by hydrophobic interaction of the end groups; this class of materials is useful for a variety of biomedical applications, including sustained protein release. The hydrogel state can be transformed into an injectable state by the addition of a toxicologically acceptable organic solvent, such as N-methyl pyrrolidone; after injection, this solution quickly returns to a gel state by diffusion of the water-miscible organic solvent into the surrounding environment. In vitro characterization of sustained release of human growth hormone (hGH) using this injectable depot shows that hGH remains stable inside the hydrogel formed, and demonstrates more than 2 weeks of prolonged release of hGH complexed with Zn2+ ions without protein aggregation or initial burst.