pH-sensitive PEGylation of RIPL peptide-conjugated nanostructured lipid carriers: design and in vitro evaluation

Abstract

BackgroundRIPL peptide (IPLVVPLRRRRRRRRC)-conjugated nanostructured lipid carriers (RIPL-NLCs) can facilitate selective drug delivery to hepsin (Hpn)-expressing cancer cells, but they exhibit low stability in the blood. Generally, biocompatible and nontoxic poly(ethylene glycol) surface modification (PEGylation) can enhance NLC stability, although this may impair drug delivery and NLC clearance. To attain RIPL-NLC steric stabilization without impairing function, pH-sensitive cleavable PEG (cPEG) was grafted onto RIPL-NLCs (cPEG-RIPL-NLCs).MethodsVarious types of NLC formulations including RIPL-NLCs, PEG-RIPL-NLCs, and cPEG-RIPL-NLCs were prepared using the solvent emulsification–evaporation method and characterized for particle size, zeta potential (ZP), and cytotoxicity. The steric stabilization effect was evaluated by plasma protein adsorption and phagocytosis inhibition studies. pH-sensitive cleavage was investigated using the dialysis method under different pH conditions. Employing a fluorescent probe (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate [DiI]), in vitro drug delivery capacity of the cPEG-RIPL-NLCs under different pH conditions was also performed on Hpn-expressing SKOV3 cells and 3D-tumor spheroids.ResultsAll prepared NLCs showed homogenous dispersion (<220 nm in size) with a negative ZP (−18 to −22 mV), except for positively charged RIPL-NLCs (~10 mV), revealing no significant cytotoxicity in either SKOV3 or RAW 264.7 cell lines. cPEG-RIPL-NLC protein adsorption was 1.75-fold less than that of RIPL-NLCs, and PEGylation significantly reduced the macrophage uptake. PEG detachment from the cPEG-RIPL-NLCs was pH-sensitive and time dependent. At 2 hours incubation, cPEG-RIPL-NLCs and PEG-RIPL-NLCs exhibited comparable cellular uptake at pH 7.4, whereas cPEG-RIPL-NLC uptake was increased over 2-fold at pH 6.5. 3D-spheroid penetration also demonstrated pH-sensitivity: at pH 7.4, cPEG-RIPL-NLCs could not penetrate deep into the spheroid core region during 2 hours, whereas at pH 6.5, high fluorescence intensity in the core region was observed for both cPEG-RIPL-NLC-and RIPL-NLC-treated groups.ConclusioncPEG-RIPL-NLCs are good candidates for Hpn-selective drug targeting in conjunction with pH-responsive PEG cleavage.

Penetration Efficiency of Antitumor Agents in Ovarian Cancer Spheroids: The Case of Recombinant Targeted Toxin DARPin-LoPE and the Chemotherapy Drug, Doxorubicin

“…The idea is that the larger sized complex firstly achieves blood concentrations sufficient for its extravasation in the tumor, where the stimuli-sensitive release of smaller active agents occurs, which penetrate deeper into the tumor [38]. A similar approach has shown prospects for ovarian cancer treatment [39]. Another concept tested on ovarian carcinoma is to use cell-penetrating/tumor-targeting peptides for a better agent penetration into tumor/tumor cells [40,41], as well as cell-mediated delivery [34].…”

Hemiacetal-linked pH-sensitive PEG-lipids for non-viral gene delivery

“…55,56 Thus, mPEG-C 2 -lipid is able to resist complete hydrolysis under physiological pH during at least 7 h. As compared to other pH-sensitive linkages used for endosomal escape technologies, our hemiacetal compound shows higher hydrolytic stability at physiological pH than a reported PEG-acetal-lipid (70% hydrolysis after 2 h) 57 and a PEG-hydrazone-lipid (80% hydrolysis after 2 h). 58…”

Efficacy of Polymer-Based Nanomedicine for the Treatment of Brain Cancer

“…The results indicated that DNA-NLCs/TMZ improved anti-tumor potential and gene transfection efficacy by transferring the two of the drugs and gene into the gliomatosis cerebri [ 97 ]. To tackle this issue, Kim et al [ 98 ] designed RIPL peptide NLCs conjugated with cleavable PEG that was released from the nanocarrier surface at the tumor position in an acidic environment. The hydrophobic anchor 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPE) was used to establish cleavable PEG, which was connected to the PEG3000 chain through a hydrazone bond [ 99 ].…”