5 research outputs found
Phospholipid-modified PEI-based nanocarriers for in vivo siRNA therapeutics against multidrug-resistant tumors.
Multidrug resistance (MDR) mediated by P-glycoprotein overexpression in solid tumors is a major factor in the failure of many forms of chemotherapy. Here we evaluated phospholipid-modified, low-molecular-weight polyethylenimine (DOPE-PEI) nanocarriers for intravenous delivery of anti-P-pg siRNA to tumors with the final goal of modulating MDR in breast cancer. First, we studied the biodistribution of DOPE-PEI nanocarriers and the effect of PEG coating in a subcutaneous breast tumor model. Four hours postinjection, PEGylated carriers showed an 8% injected dose (ID) accumulation in solid tumor via the enhanced permeability and retention effect and 22% ID in serum due to a prolonged, PEG-mediated circulation. Second, we established the therapeutic efficacy and safety of DOPE-PEI/siRNA-mediated P-gp downregulation in combination with doxorubicin (Dox) chemotherapy in MCF-7/MDR xenografts. Weekly injection of siRNA nanopreparations and Dox for up to 5 weeks sensitized the tumors to otherwise non-effective doses of Dox and decreased the tumor volume by threefold vs controls. This therapeutic improvement in response to Dox was attributed to the significant, sequence-specific P-gp downregulation in excised tumors mediated by the DOPE-PEI formulations
Post-Transcriptional Regulation of the GASC1 Oncogene with Active Tumor-Targeted siRNA-Nanoparticles
Screening Nylon‑3 Polymers, a New Class of Cationic Amphiphiles, for siRNA Delivery
Amphiphilic nucleic acid carriers
have attracted strong interest.
Three groups of nylon-3 copolymers (poly-β-peptides) possessing
different cationic/hydrophobic content were evaluated as siRNA delivery
agents in this study. Their ability to condense siRNA was determined
in SYBR Gold assays. Their cytotoxicity was tested by MTT assays,
their efficiency of delivering Alexa Fluor-488-labeled siRNA intracellularly
in the presence and absence of uptake inhibitors was assessed by flow
cytometry, and their transfection efficacies were studied by luciferase
knockdown in a cell line stably expressing luciferase (H1299/Luc).
Endosomal release was determined by confocal laser scanning microscopy
and colocalization with lysotracker. All polymers efficiently condensed
siRNA at nitrogen-to-phosphate (N/P) ratios of 5 or lower, as reflected
in hydrodynamic diameters smaller than that at N/P 1. Although several
formulations had negative zeta potentials at N/P 1, G2C and G2D polyplexes
yielded >80% uptake in H1299/Luc cells, as determined by flow cytometry.
Luciferase knockdown (20–65%) was observed after transfection
with polyplexes made of the high molecular weight polymers that were
the most hydrophobic. The ability of nylon-3 polymers to deliver siRNA
intracellularly even at negative zeta potential implies that they
mediate transport across cell membranes based on their amphiphilicity.
The cellular uptake route was determined to strongly depend on the
presence of cholesterol in the cell membrane. These polymers are,
therefore, very promising for siRNA delivery at reduced surface charge
and toxicity. Our study identified nylon-3 formulations at low N/P
ratios for effective gene knockdown, indicating that nylon-3 polymers
are a new, promising type of gene delivery agent