Peptide-assembled hydrogels for pH-controllable drug release

A peptide (FFACD) can form hydrogels in DMSO-H₂O mixtures (G1), NaOH (G2) and L-arginine (G3) aqueous solutions, respectively. Methyl thiazolyl tetrazolium (MTT) assays demonstrated that G1 and G3 exhibited excellent biocompatibility against HEK293 epithelial cells while G2 had an obvious cytotoxicity. G1 and G3 were used as drug carriers with the high drug loading capacity (DLC). Both hydrophilic DOX and hydrophobic PTX were completely loaded into G1 without destroying the hydrogel, while G3 could only encapsulate DOX. The strong electrostatic interaction between DOX and FFACD molecules could destroy the microstructure of G3 to produce precipitate with a high DOX DLC of 93%. The cytotoxicity assay of G1/DOX against K562 leukemia cells indicated that G1 did not inhabit the efficacy of DOX. In vitro release experiments demonstrated DOX of G3/DOX precipitates could be released 76% at pH = 6.0 of the tumor cells and only about 13% at pH = 7.4 of normal cells.