Nanomedicine and Drug Delivery

Biography

Biography: Shahd Abuhelal

Abstract

The presence of small interfering RNA (siRNA) in a cell leads to silencing of protein expression, offering the potential of a powerful therapeutic option for treatment of many conventionally intractable diseases. Due to the negative charge and sensitivity against RNase,siRNA has a short half-life in the blood and struggles to penetrate within the target cells. Successful development of siRNA therapies depends on the ability for it to be efficiently delivered inside the target cells efficiently while avoiding enzymatic degradation and aggregation. Methodology: We present the design and optimization of a cationic liposomal/pH responsive cationic peptide based nano-carrier for siRNA delivery. The major used components in the formulation are; DODAG (1 N′,N′-dioctadecyl-N-4,8-diaza-10aminodecanoylglycine amide), a cationic lipid which was designed to be a structural chimera involving the N(1)-cholesteryloxycarbonyl-3-7-diazanonane-1,9-diamine (CDAN) polar head group and the dialkylglycine amide moiety of dioctadecylamido glycylspermine (DOGS) to improve positively charged lipid interaction with siRNA, and LAH4-L1 is a 26-amino acid, histidine rich helical peptide. It is a membrane-active peptide that displays increased affinity toward anionic lipids and possess DNA delivery capabilities. Liposomes (20% DODAG, DOPC/ cholesterol/DSPE-PEG2000)/siRNA, LAH4-L1/siRNA (Figure1) and their combination with siRNA (Figure 2) have been investigated as delivery systems. Their physicochemical characteristics such as size, zeta potential, siRNA retention, release behaviour and aggregation behaviour of formulations were tested. In vitro cell uptake and luciferase knock-down studies were also tested in MDA-MB231 and A549 cells. Complexes were tested in vivo for bio-distribution. Findings: The hydrodynamic diameter and zeta potential of the particles was characterized. Size was adjusted to be around 130nm and zeta potential was slightly positive. All complexes associated with siRNA have more than 80% complexation efficiency. Lipoplexes showed better encapsulation but were less stable as leakage was observed after co-incubation in serum. Improved cell uptake was seen with ternary complex in comparison with liposomal and Peptide siRNA complexes (siRNA cells uptake was increased from 1.4% to 32.9% in some cases). In vitro studies suggest improvement in gene silencing with ternary complex even when compared with generic positive control. in vivo studies are ongoing to understand the pharmacokinetic behaviour of the particles. Conclusion & Significance: A stable lipid/peptide ternary complex for siRNA delivery with defined physicochemical properties was designed and evaluated and shown to be a promising delivery system for siRNA for both in vitro and in vivo applications. Current and future work is focused, in vitro, on the improvement of cell targeting and in vivo on studying the PK/PD properties of the new system.