Paclitaxel-loaded pH responsive hydrogel based on self-assembled peptides for tumor targeting.

Intratumoral delivery of chemotherapeutic agents may permit the localization of drugs in tumors, decrease nonspecific targeting and increase efficacy. The pH-responsive peptide hydrogel is considered a suitable carrier for chemotherapeutics via intratumoral injection. Thus, a study was carried out to develop a paclitaxel (PTX) drug delivery system using a pH-responsive FER-8 peptide hydrogel for tumor targeting. The pH-sensitive hydrogel system was characterized for loading capacity, acid sensitivity, structure, rheology, morphology, drug release, in vitro cytotoxicity and in vivo efficacy in H22 tumor-bearing mice. The stable FER-8 peptide hydrogel with high drug-loading capacity was formed at pH 7.4 by the self-assembly of peptide, whereas higher degradation was observed at an acidic pH. Circular dichroism and rheology confirmed the suitable meshwork structure and enhanced mechanical properties of the hydrogel. The FER-8 peptide hydrogel fibers were found to have an average size less than 500 nm at pH 7.4, which was confirmed by TEM and DLS analysis. Sustained release of PTX at pH 5.5 was observed for the FER-8 peptide hydrogel (HG-PTX) for almost 1 week. In vitro cytotoxicity studies indicated that the FER-8 peptide hydrogel increased the drug accumulation in HepG2 cells and effectively inhibited the growth of HepG2 tumor cells compared with free drugs. Furthermore, in vivo studies using H22-bearing mice indicated that the paclitaxel-loaded FER-8 peptide hydrogel significantly increased the amount of drugs in tumor tissues and showed prolonged retention (96 hours) at the tumor site by intratumoral injection. The in vivo anti-tumor studies confirmed the pH-sensitive properties of HG-PTX, which allowed the drug to be triggered by the acidic pH environment at tumor sites, provided sustained delivery of the drug and enhanced tumor inhibition. In conclusion, HG-PTX provides an attractive strategy and potential vehicle for efficient anti-cancer drug delivery. The carrier can enhance tumor targeting, prolong retention, reduce systemic side effects and increase the accumulation of drugs at the tumor site.