TAT peptide-modified liposomes provide enhanced gene delivery to intracranial human brain tumor xenografts in nude mice.

In this study, we have investigated the potential of trans-activating transcriptional activator peptide (TATp)-modified liposomes to enhance the delivery of the model gene, plasmid encoding for the green fluorescent protein (pEGFP-N1), to human brain tumor U-87 MG cells in vitro and in an intracranial model in nude mice. The TATp-lipoplexes were characterized at lipid/DNA (+/-) charge ratios of 0.2, 5, 10, and 20 for size analysis and DNA complexation. The size distribution of DNA-loaded TATp-liposomes was narrow and the DNA complexation was firm at lipid/DNA (+/-) charge ratios of 5 and higher. TATp-lipoplexes had demonstrated an enhanced delivery of pEGFP-N1 to U-87 MG tumor cells in vitro at lipid/DNA (+/-) charge ratios of 5 and 10. In vivo transfection of intracranial brain tumors by intratumoral injections of TATp-lipoplexes showed an enhanced delivery of pEGFP-N1 selectively to tumor cells and subsequent effective transfection compared to plain plasmid-loaded lipoplexes. No transfection (green fluorescence of the GFP) was noted in the normal brain adjacent to tumor.

Monoclonal antibody 2C5-mediated binding of liposomes to brain tumor cells in vitro and in subcutaneous tumor model in vivo.

This study aimed to investigate the monoclonal antibody (mAb) 2C5 with nucleosome-restricted specificity for its ability to specifically recognize human brain tumor cells and to serve as a specific ligand for liposome targeting to brain tumor cells in vitro and in vivo. The affinity of mAb 2C5 towards brain tumor cells was tested by flow cytometry. The interaction of 2C5-immunoliposomes (ILS) with brain tumor cells in vitro was studied by fluorescence microscopy. For in vivo accumulation studies, (111)In-ILS were administered i.v. into mice bearing subcutaneously grown brain tumor. mAb 2C5 was found to be reactive against several tested brain tumor cell lines. mAb 2C5 and 2C5-ILS demonstrated enhanced cell-surface binding with CCF-STTG1,U-87 MG and LN-18 cells in vitro. 2C5-ILS displayed significantly better accumulation in the subcutaneously grown brain tumor than non-specific control IgG-ILS. mAb 2C5 specifically recognizes brain tumor cells and can serve as a ligand to target drug carriers such as liposomes to brain tumor cells in vivo.

Intracellular delivery of large molecules and small particles by cell-penetrating proteins and peptides.

Cell-penetrating peptides (CPPs) have been used to overcome the lipophilic barrier of the cellular membranes and deliver large molecules and even small particles inside the cell for their biological actions. CPPs are being used to deliver inside cell a large variety of cargoes such as proteins, DNA, antibodies, contrast (imaging) agents, toxins, and nanoparticular drug carriers including liposomes. In this paper, we have reviewed the delivery of different molecules and particles mediated by TAT, Antp, VP22, and other CPPs as well as potential applications of these delivery systems in different areas of vaccine development, cancer immunotherapy, gene delivery, and cellular imaging.

Preparation and in vitro synergistic anticancer effect of vitamin K3 and 1,8-diazabicyclo[5,4,0]undec-7-ene in poly(ethylene glycol)-diacyllipid micelles.

Polymeric micelles consisting of poly(ethylene glycol)-distearoyl phosphoethanolamine conjugates (PEG-DSPE) loaded with Vitamin K3 (VK3) to 0.2 mg of drug/mg of carrier and with 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU) to 0.06 mg of drug/mg of carrier were prepared. These micelles were stable for as long as 6 months during storage at 4 degrees C and did not change their size or release the incorporated drugs. Co-encapsulation of VK3 and DBU into PEG-DSPE micelles resulted in synergistic anticancer effects against both murine and human cancer cells in vitro. The synergism may be explained by the fact that the presence of DBU promotes the escape of drug-loaded micelles from the endosomes of cancer cells directly into the cytoplasm as demonstrated by fluorescent microscopy.

Liposome clearance in mice: the effect of a separate and combined presence of surface charge and polymer coating.

The purpose of our work was to compare the biodistribution of liposomes with different surface properties. Phosphatidylcholine (PC)/cholesterol (Chol) liposomes were prepared containing 6% mol of a charged lipid (stearylamine, SA; phosphatidic acid, PA; or phosphatidyl serine, PS) and/or polyethylene glycol (PEG)-PE of different MW (750 and 5000). zeta-Potentials and liposome clearance in mice were investigated. In vitro, the attachment of PEG in a similar fashion neutralizes the effect of any charged component. In vivo, the chemical nature of a charged lipid becomes important. Both short PEG750 and longer PEG5000 inhibit the clearance of positively charged SA-liposomes, while only longer PEG5000 inhibits the clearance of negatively charged PA-liposomes and none of the PEGs inhibit the clearance of negatively charged PS-liposomes. The opsonins with different molecular size may be involved in the clearance of liposomes containing different charged lipids.