Dual-functional liposomes based on pH-responsive cell-penetrating peptide and hyaluronic acid for tumor-targeted anticancer drug delivery.

Dual-functional liposomes with pH-responsive cell-penetrating peptide (CPP) and active targeting hyaluronic acid (HA) were fabricated for tumor-targeted drug delivery. A series of synthetic tumor pH-triggered CPPs rich in arginines and histidines were screened by comparing tumor cellular uptake efficiency at pH 6.4 with at pH 7.4, and R6H4 (RRRRRRHHHH) was obtained with the optimal pH-response. To construct R6H4-modified liposomes (R6H4-L), stearyl R6H4 was anchored into liposomes due to hydrophobic interaction. HA was utilized to shield positive charge of R6H4-L to assemble HA-coated R6H4-L (HA-R6H4-L) by electrostatic effect for protecting the liposomes from the attack of plasma proteins. The rapid degradation of HA by hyaluronidase (HAase) was demonstrated by the viscosity and zeta potential detection, allowing the R6H4 exposure of HA-R6H4-L at HAase-rich tumor microenvironment as the protection by HA switches off and cell-penetrating ability of R6H4 turns on. After HAase treatment, paclitaxel-loaded HA-R6H4-L (PTX/HA-R6H4-L) presented a remarkably stronger cytotoxicity toward the hepatic cancer (HepG2) cells at pH 6.4 relative to at pH 7.4, and additionally coumarin 6-loaded HA-R6H4-L (C6/HA-R6H4-L) showed efficient intracellular trafficking including endosomal/lysosomal escape and cytoplasmic liberation by confocal laser scanning microscopy (CLSM). In vivo imaging suggested the reduced accumulation of near infrared dye 15 (NIRD15)-loaded HA-R6H4-L (NIRD/HA-R6H4-L) at the tumor site, when mice were pre-treated with an excess of free HA, indicating the active tumor targeting of HA. Indeed, PTX/HA-R6H4-L had the strongest antitumor efficacy against murine hepatic carcinoma (Heps) tumor xenograft models in vivo. These findings demonstrate the feasibility of using tumor pH-sensitive CPPs and active targeting HA to extend the applications of liposomal nanocarriers to efficient anticancer drug delivery.