No abstract

Glioma is a highly malignant tumor that starts in the glial cells of brain. Tumor cells reproduce quickly and infiltrate rapidly in high grade glioma. Permeability of chemotherapeutic agents into brain is restricted owing to the presence of blood brain barrier (BBB). In this study, we developed a dual functionalized liposomal delivery system for efficient transport of chemotherapeutics across BBB for the treatment of glioma. Liposomes were surface modified with transferrin (Tf) for receptor targeting, and cell penetrating peptide PFVYLI (PFV) to increase translocation of doxorubicin (Dox) and Erlotinib (Erlo) across the BBB into glioblastoma (U87) tumor cells. In vitro cytotoxicity and hemolysis studies were performed to assess biocompatibility of liposomal nanoparticles. Cellular uptake studies demonstrated efficient internalization of Dox and Erlo in U87, brain endothelial (bEnd.3), and glial cells. In addition, dual functionalized liposomes showed significantly (p < 0.05) higher apoptosis in U87 cells. Significantly (p < 0.05) higher translocation of dual functionalized liposomes across the BBB and delivering chemotherapeutic drugs to the glioblastoma tumor cells inside PLGA-Chitosan scaffold resulted in approximately 52% tumor cell death, using in vitro brain tumor model.

The challenge of effectively delivering therapeutic agents to brain has led to an entire field of active research devoted to overcome the blood brain barrier (BBB) and efficiently deliver drugs to brain. This review focusses on exploring the facets of a novel platform designed for the delivery of drugs to brain. The platform was constructed based on the hypothesis that a combination of receptor-targeting agent, like transferrin protein, and a cell-penetrating peptide (CPP) will enhance the delivery of associated therapeutic cargo across the BBB. The combination of these two agents in a delivery vehicle has shown significantly improved (p < 0.05) translocation of small molecules and genes into brain as compared to the vehicle with only receptor-targeting agents. The comprehensive details of the uptake mechanisms and properties of various CPPs are illustrated here. The application of this technology, in conjunction with nanotechnology, can potentially open new horizons for the treatment of central nervous system disorders.

Background The potential of gene therapy for treatment of neurological disorders can be explored using designed lipid-based nanoparticles such as liposomes, which have demonstrated ability to deliver nucleic acid to brain cells. We synthesized liposomes conjugated to cell-penetrating peptides (CPPs) (vascular endothelial-cadherin-derived peptide [pVec], pentapeptide QLPVM and HIV-1 trans-activating protein [TAT]) and transferrin (Tf) ligand, and examined the influence of surface modifications on the liposome delivery capacity and transfection efficiency of encapsulated plasmid DNA. The design of liposomes was based on targeting molecular recognition of transferrin receptor overexpressed on the blood–brain barrier (BBB) with enhanced internalization ability of CPPs. Methods CPP-Tf-liposomes were characterized by particle size distribution, zeta potential, protection of encapsulated plasmid DNA, uptake mechanisms and transfection efficiencies. An in vitro triple co-culture BBB model selected the liposomal formulations that were able to cross the in vitro BBB and subsequently, transfect primary neuronal cells. The in vivo biodistribution and biocompatibility of selected formulations were also investigated in mice. Results Liposomal formulations were able to protect the encapsulated plasmid DNA against enzymatic degradation and presented low hemolytic potential and low cytotoxicity at 100 nM phospholipid concentration. Cellular internalization of nanoparticles occurred via multiple endocytosis pathways. CPP-Tf-conjugated liposomes mediated robust transfection of brain endothelial (bEnd.3), primary glial and primary neuronal cells. Liposomes modified with Tf and TAT demonstrated superior ability to cross the barrier layer and subsequently, transfect neuronal cells compared to other formulations. Quantification of fluorescently labeled liposomes and in vivo imaging demonstrated that this system could efficiently overcome the BBB and penetrate the brain of mice (7.7% penetration of injected dose). Conclusion In vitro screening platforms are important tools to enhance the success of brain-targeted gene delivery systems. The potential of TAT-Tf-liposomes as efficient brain-targeted gene carriers in vitro and in vivo was suggested to be related to the presence of selected moieties on the nanoparticle surface.

Drug delivery to the brain has been a major challenge due to the presence of the blood-brain barrier, which limits the uptake of most chemotherapeutics into brain. We developed a dual-functionalized liposomal delivery system, conjugating cell penetrating peptide penetratin to transferrin-liposomes (Tf-Pen-conjugated liposomes) to enhance the transport of an anticancer chemotherapeutic drug, 5-fluorouracil (5-FU), across the blood-brain barrier into the tumor cells. The in vitro cellular uptake study showed that the dual-functionalized liposomes are capable of higher cellular uptake in glioblastoma (U87) and brain endothelial (bEnd.3) cells monolayer. In addition, dual-functionalized liposomes demonstrated significantly higher apoptosis in U87 cells. The liposomal nanoparticles showed excellent blood compatibility and in vitro cell viability, as studied by hemolysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, respectively. The 5-FU-loaded dual-functionalized liposomes demonstrated higher transport across the brain endothelial barrier and delivered 5-FU to tumor cells inside poly(lactic-co-glycolic acid)-chitosan scaffold (an in vitro brain tumor model), resulting in significant tumor regression.