Utilizing G2/M retention effect to enhance tumor accumulation of active targeting nanoparticles.

In recent years, active targeting strategies by ligand modification have emerged to enhance tumor accumulation of NP, but their clinical application was strictly restricted due to the complex preparation procedures, poor stability and serious toxicity. An effective and clinical translational strategy is required to satisfy the current problems. Interestingly, the internalization of NP is intimately related with cell cycle and the expression of receptors is not only related with cancer types but also cell cycle progression. So the cellular uptake of ligand modified NP may be related with cell cycle. However, few investigations were reported about the relationship between cell cycle and the internalization of ligand modified NP. Herein, cellular uptake of folic acid (FA) modified NP after utilizing chemotherapeutic to retain the tumor cells in G2/M phase was studied and a novel strategy was designed to enhance the active targeting effect. In our study, docetaxel (DTX) notably synchronized cells in G2/M phase and pretreatment with DTX highly improved in vitro and in vivo tumor cell targeting effect of FA decorated NP (FANP). Since FA was a most common used tumor active targeting ligand, we believe that this strategy possesses broader prospects in clinical application for its simplicity and effectiveness.

Tumor-targeted paclitaxel delivery and enhanced penetration using TAT-decorated liposomes comprising redox-responsive poly(ethylene glycol).

To combine the advantage of poly(ethylene gylcol) (PEG) for longer circulation and cell-penetrating peptides (CPPs) for efficient cellular uptake, paclitaxel (PTX)-loaded liposomes functionalized with TAT, the most frequently used CPP, and cleavable PEG via a redox-responsive disulfide linker (PTX-C-TAT-LP) were successfully developed here. Under physiological conditions, TAT was shielded by PEG layer and liposomes exhibited a long blood circulation. At tumor site, PEG could be detached in the presence of exogenous reducing agent [glutathione (GSH)] and TAT was exposed to facilitate cell internalization. In the presence of GSH, the liposomal vesicle C-TAT-LP showed increased cellular uptake and improved three-dimensional tumor spheroids penetration in vitro compared with analogous stable shielded liposomes. C-TAT-LP achieved enhanced tumor distribution and demonstrated superior delivery efficiency in vivo. PTX-C-TAT-LP with GSH strongly inhibited the proliferation of murine melanoma B16F1 tumor cells in vitro and in vivo with the tumor inhibition rate being 69.4% on B16F1-bearing mice. In addition, the serum aspartate transaminase level, alanine transaminase level, and creatine kinase level were almost completely within normal range in the PTX-C-TAT-LP with GSH group, revealing PTX-C-TAT-LP with GSH had no obvious drug-related adverse events for liver and heart. Taken together, C-TAT-LP is a promising tumor-targeting drug carrier.

PEGylated hyaluronic acid-modified liposomal delivery system with anti-γ-glutamylcyclotransferase siRNA for drug-resistant MCF-7 breast cancer therapy.

Human chromosome 7 open reading frame 24 has been identified as a tumor-related protein, and later it was shown to be γ-glutamylcyclotransferase (GGCT). This protein is upregulated in various types of cancer and is proved to be associated with cellular proliferation. RNA interference is an effective method to achieve highly specific gene regulation. In this study, the anti-GGCT siRNA was incorporated into a comprehensively evaluated polyethylene glycol-hyaluronic acid-modified liposomal siRNA delivery system (PEG-HA-NP) for drug-resistant MCF-7 breast cancer therapy by systemic administration. The PEG-HA-NP had a diameter of 216 nm and a zeta potential of -17.4 mV. Transfection of anti-GGCT siRNA-loaded PEG-HA-NP could achieve effective GGCT downregulation and induce the subsequent cell cytotoxicity against MCF-7/ADR cells. Systemic administration of PEG-HA-NP at 0.35 mg/kg siRNA could retard the tumor growth and induce necrosis of tumor tissue while showing no obvious toxicity to normal tissues. Therefore, systemic administration of anti-GGCT-loaded PEG-HA-NP was proved to be a promising strategy for drug-resistant MCF-7 breast cancer therapy.

Enhanced gene delivery efficiency of cationic liposomes coated with PEGylated hyaluronic acid for anti P-glycoprotein siRNA: a potential candidate for overcoming multi-drug resistance.

RNA interference is an effective method to achieve highly specific gene regulation. However, the commonly used cationic liposomes have poor biocompatibility, which may lead to systematic siRNA delivery of no avail. PEGylation is a good strategy in shielding the positive charge of cationic liposomes, but the enhanced serum stability is often in company with compromised cellular uptake and endosome escape. In this study, PEG was covalently linked to negatively charged hyaluronic acid and it was used to coat the liposome-siRNA nanoparticles. The resulting PEG-HA-NP complex had a diameter of 188.6 ± 10.8 nm and a dramatically declined zeta-potential from +34.9 ± 4.0 mV to -18.2 ± 2.2 mV. Owing to the reversed surface charge, PEG-HA-NP could remain stable in fetal bovine serum (FBS) to up to 24h. In contrast with normal PEGylation, hyaluronic acid and PEG co-modified PEG-HA-NP provided comparable cellular uptake and P-glycoprotein downregulation efficacy in MCF-7/ADR cells compared with Lipofectamine RNAiMAX and naked NP regardless of its anionic charged surface. Because of its good biocompatibility in serum, PEG-HA-NP possessed the best tumor accumulation, cellular uptake and subsequently the strongest P-glycoprotein silencing capability in tumor bearing mice compared with naked NP and HA-NP after i.v. injection, with a 34% P-glycoprotein downregulation. Therefore, PEG-HA coated liposomal complex was demonstrated to be a promising siRNA delivery system in adjusting solid tumor P-glycoprotein expression, which may become a potential carrier in reversing MDR for breast cancer therapy.

Paclitaxel loaded liposomes decorated with a multifunctional tandem peptide for glioma targeting.

The treatment of glioma is a great challenge because of the existence of the blood-brain barrier (BBB). In order to reduce toxicity to the normal brain tissue and achieve efficient treatment, it is also important for drugs to specifically accumulate in the glioma foci and penetrate into the tumor core after entering into the brain. In this study, a specific ligand cyclic RGD peptide was conjugated to a cell penetrating peptide R8 to develop a multifunctional peptide R8-RGD. R8-RGD increased the cellular uptake of liposomes by 2-fold and nearly 30-fold compared to separate R8 and RGD respectively, and displayed effective penetration of three-dimensional glioma spheroids and BBB model in vitro. In vivo studies showed that R8-RGD-lipo could be efficiently delivered into the brain and selectively accumulated in the glioma foci after systemic administration in C6 glioma bearing mice. When paclitaxel (PTX) was loaded in liposomes, R8-RGD-lipo could induce the strongest inhibition and apoptosis against C6 cells and finally achieved the longest survival in intracranial C6 glioma bearing mice. In conclusion, all the results indicated that the tandem peptide R8-RGD was a promising ligand possessing multi functions including BBB transporting, glioma targeting and tumor penetrating. And R8-RGD-lipo was proved to be a potential anti-glioma drug delivery system.

Liposomes co-modified with cholesterol anchored cleavable PEG and octaarginines for tumor targeted drug delivery.

Tumor targeted drug delivery system with high efficiency of tumor accumulation, cell internalization and endosomal escape was considered ideal for cancer therapy. Herein, a cleavable polyethylene glycol (PEG) and octaarginines (R8) co-modified liposome (CL-R8-LP) was developed, in which the cholesterol was used as an alternative anchor to the commonest phospholipids for the diversified development of surface modification. The in vitro hemolysis assay and bio-distribution study demonstrated that CL-R8-LP improved biocompatibility and tumor accumulation compared with the single R8 modified liposomes (R8-LP), since the strong positive charges, toxicity and non-specificity of R8 were efficiently shielded by the outer cleavable PEG. And the cellular uptake, cytotoxicity and apoptosis of CL-R8-LP on C26 cells were much stronger than that of control liposomes in which R8 was not included or exposed. In addition, it was confirmed that CL-R8-LP entered cells via clathrin-mediated endocytosis and the macropinocytosis, and followed by a more efficient endosomal escape compared with R8-LP due to the topology change of R8. The enhanced in vivo delivery efficiency and anti-tumor efficacy were validated in C26 bearing mice. In conclusion, the results demonstrated that CL-R8-LP was a promising vehicle for enhancing the chemotherapy of solid cancers.

A detachable coating of cholesterol-anchored PEG improves tumor targeting of cell-penetrating peptide-modified liposomes.

Cell-penetrating peptides (CPPs) have been widely used to enhance the membrane translocation of various carriers for many years, but the non-specificity of CPPs seriously limits their utility in vivo. In this study, cholesterol-anchored, reduction-sensitive PEG (first synthesized by our laboratory) was applied to develop a co-modified liposome with improved tumor targeting. Following optimization of the formulation, the in vitro and in vivo properties of the co-modified liposome were evaluated. The co-modified liposome had a much lower cellular uptake and tumor spheroid uptake, but a much higher tumor accumulation compared to CPP-modified liposome, indicating the non-specific penetration of CPPs could be attenuated by the outer PEG coating. With the addition of exogenous reducing agent, both the in vitro and in vivo cellular uptake was markedly increased, demonstrating that the reduction-sensitive PEG coating achieved a controllable detachment from the surface of liposomes and did not affect the penetrating abilities of CPPs. The present results demonstrate that the combination of cholestervsitive PEG and CPPs is an ideal alternative for the application of CPP-modified carriers in vivo.