Lipid-Modified Polyethyleneimine: A Versatile Platform for Enhanced Gene Delivery and Sirna-Mediated Silencing
Project Investigator: Dr. Rupa Sawant
The project within the CTCN dealing with developing PEG-PE-based polymeric micelles for the protection and delivery of siRNA can be complemented by the synthesis of additional polymer-lipid conjugates used for the delivery of siRNA and DNA. Water soluble polyethylenimine (PEI 1.8kDa) can be hydrophobically modified with phosphoethanolamine (PE-PEI) or phosphocholine phospholipids (PC-PEI) to obtain different amphiphilic structures. In the case of PE-PEI conjugates, the head of DOPE or DPPE phospholipid can be grafted to the PEI backbone. On the contrary, PC-PEI conjugates can be constructed by grafting one of the phospholipid fatty acid tails to the PEI backbone. The conjugates will be evaluated for siRNA delivery and down-regulation of gene expression in cells, and the gene silencing efficacy will be studied dependeing on the nature of the lipid grafted and the structure of the conjugate. We hypothesize that the outer shell of PE-PEI complexes and PC-PEI complexes can self-assemble into the micelle-like complexes and may display a different degree of cell membrane interaction. This latter feature together with their in vitro gene silencing efficacy suggests promising application for phospholipid-modified PEIs as dual nanocarriers poorly soluble drug/siRNA. In addition, the use of low-molecular-weight PEI and its modification with lipids is expected to decrease the PEI toxicity – the main limiting factor of its use in vivo. PEI-DOPE conjugates will be evaluated for siRNA delivery with the goal of silencing the MDR-1 gene encoding for P-glycoprotein (P-gp) and overcoming drug resistance in MDR human breast cancer cells.
One of the key projects of the CTCN aims to engineer polymeric micelles co-loaded with anti-cancer drug and siRNA down-regulating certain proteins involved into the development of Multidrug Resistance (MDR) in cancer cells. Polymeric micelles to be used in this project are based on the conjugate between polyethylene glycol and phosphatidylethanolamine (PEG-PE).
Recently, we have developed novel derivatives of low-molecular-weight polyethyleneimine (PEI) containing lipid modifications. Low-molecular-weight PEI is known not be a very good carrier for DNA and related materials, such as siRNA, compared to higher MW PEI, but is much less toxic than high MW PEI. We found that lipidated low MW PEI serves as a very efficient system for DNA/siRNA delivery, but preserves low toxicity of the initial low MW PEI. Complexes of low MW lipidated PEI with siRNA have a micelle-like structure and can be additionally loaded with poorly soluble anti-cancer drugs. In our preliminary experiments, we have shown that the co-administration of siRNA complexes with low MW lipidated PEI together with doxorubicin reverses MDR in resistant breast cancer cells and significantly increases their killing by the drug.
Thus, micelle-like structures based on non-toxic lipidated PEI can become a useful addition or alternative to PEG-PE-based structures for the co-delivery of anti-cancer drug and siRNA to overcome the MDR phenomenon in resistant cancer cells and increase the efficiency of such combination therapy.