Alternative Micelle-Like Nanoparticles for Co-Loading of siRNA and Poorly Soluble Drugs
One of the projects within the CTCN is focused on developing PEG-PE-based-polymeric micelles for the protection and delivery of siRNA. Here, we propose an alternative micellar carrier based on phospholipid modified-polyethylenimine (PEI) for systemic, tumor-targeted and simultaneous delivery of siRNA and drug. We previously showed that the hydrophobic modification of low molecular weight PEI (1.8 kDa) with phospholipids such as phosphoethanolamine and phosphocholine generated different amphiphiles that self-assembled into micellar structures, condensed and protected siRNA and achieved different levels of gene silencing depending on the nature of the phospholipid and the structure of the conjugate. We found that DOPE modification of PEI dramatically increased siRNA intracellular delivery and gene down-regulation capacity of non-modified PEI while the abscence of cytotoxicity of PEI was maintained. In addition, DOPE-PEI/siRNA complexes can interact with lipidated PEG giving raise to micelle-like nanoparticles that stabilize the siRNA upon intravenous injection and promoted its delivery at the tumor site. We hypothesize that the results obtained with these micelle-like nanoparticles can be reinforced by the inclusion of tumor specific cell-binding ligands such as Transferrin (TF). Therefore, TF-PEG-modified DOPE-PEI micelles will be evaluated as dual siRNA/drug carriers with final goal of increasing the bioavailability and efficacy of such combinations in a synergistic manner at the tumor site. In particular, we will assess their capacity to stabilized siRNA, increase drug solubility, facilitate the uptake of the dual cargo by means of targeted interaction with cancer cells and boost the antitumor effect of poorly soluble anticancer drug (paclitaxel) and siRNA (down-regulating apoptosis related proteins) co-delivery.
The use of siRNA silencing approach to solve some of the limitations of traditional chemotherapy is gathering increased research interest. We recently showed that siRNA silencing of P-gp efflux transporters in multidrug resistant tumors improved the effectiveness of anticancer drugs. Polyethilenimine (PEI) is widely used for nucleic acid delivery, including siRNA delivery. PEI can be synthesized in different lengths, be branched or linear, and possesses high charge density that endows it with highly efficient condensation of nucleic acids (DNA, siRNA).
In this study, we will examine phospholipid-modified PEIs as the principal component of alternative Transferrin-PEG-micelles for dual and targeted delivery of poorly soluble drugs and siRNA. Water soluble polyethylenimine will be modified with phosphoethanolamine phospholipids to obtain different amphiphilic structures. In particular, we will evaluate the effect of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) conjugation on transfection efficacy and toxicity of PEI and the capacity of these novel amphiphiles to self-assemble into micelle like complexes for simultaneous delivery of drug and siRNA. DOPE-PEI micelles will be further modified with PEG to improve their in vivo stability and biocompatibility and with Transferrin to increase their specificity towards tumor site. Both siRNA down-regulating Green Fluorescent Protein and paclitaxel will be studied as model of siRNA and poorly soluble drugs, respectively. The therapeutic application will be assesed by using siRNA down-regulating apoptosis related protein (survivin, polokinase-1) and poorly soluble anticancer drug (paclitaxel).