Taken together, these results suggest that pmIL-12/PPC may be an effective strategy for inhibiting progression of disseminated ovarian cancer and may offer a new option for treatment of advanced disease that can be used to complement standard therapies.

We have designed a series of versatile lipopolyamines which are amenable to chemical modification for in vivo delivery of small interfering RNA (siRNA). This report focuses on one such lipopolyamine (Staramine), its functionalized derivatives and the lipid nanocomplexes it forms with siRNA. Intravenous (i.v.) administration of Staramine/siRNA nanocomplexes modified with methoxypolyethylene glycol (mPEG) provides safe and effective delivery of siRNA and significant target gene knockdown in the lungs of normal mice, with much lower knockdown in liver, spleen, and kidney. Although siRNA delivered via Staramine is initially distributed across all these organs, the observed clearance rate from the lung tissue is considerably slower than in other tissues resulting in prolonged siRNA accumulation on the timescale of RNA interference (RNAi)-mediated transcript depletion. Complete blood count (CBC) analysis, serum chemistry analysis, and histopathology results are all consistent with minimal toxicity. An in vivo screen of mPEG modified Staramine nanocomplexes-containing siRNAs targeting lung cell-specific marker proteins reveal exclusive transfection of endothelial cells. Safe and effective delivery of siRNA to the lung with chemically versatile lipopolyamine systems provides opportunities for investigation of pulmonary cell function in vivo as well as potential treatments of pulmonary disease with RNAi-based therapeutics.

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The therapeutic application of commercially available polyethylenimines (e.g., PEI 25 kD) is marred by substantial toxicity. The benefit of using lower molecular weight polyethylenimines (<25 kD) has not been fully explored because of limited availability and high molecular heterogeneity (e.g., degree of branching) among the available few. We have synthesized a series of low molecular weight linear polyethylenimines (LPEI; 2.5-25 kD) with a single synthesis scheme to minimize molecular heterogeneity. DNA formulation with the newly synthesized linear polyethylenimines resulted in the formation of stable nanoparticles (100-150 nm) of positive zeta potential. Addition of these nanoparticles onto COS-1 and HEK 293 cell cultures led to transgene expression the efficiency and cytotoxicity of which varied with the LPEI size. The lowest molecular weight LPEI (LPEI 2.5 kD) gave the smallest level of gene expression and did not exert any cytotoxicity. The transfection activity exponentially increased with higher molecular weight LPEIs reaching maximal level with 7.5 kD LPEI and was accompanied with some cytotoxicity. The transfection activity of 7.5 kD LPEI was equal to that of the higher molecular weight LPEIs including 25 kD LPEI, but caused less cytotoxicity. To achieve high transfection efficiency without substantial increase in cytotoxicity, we cross-linked LPEI 3.6 kD with a biodegradable linkage to form a multi-block copolymer (BD3.6K) of approximately 8 kD. The multi-block copolymer, BD3.6K, expressed 20-fold higher transfection activity than that of the monomer block and produced significantly lower cytotoxicity than 25 kD PEI in vitro. Following intravenous administration, plasmid/BD3.6K complexes elicited significant gene transfer in lungs, while complexes prepared with monomer block did not yield discernable transfection activity. The transfection efficiency of the systemically administered plasmid/BD3.6K complexes was 2.5-times and 70-times higher than that of linear and branched 25 kD PEI, respectively. Transfection complexes prepared with BD3.6K exhibited better tolerability than complexes prepared with 25 kD PEIs. These results demonstrate that: (1) the lower molecular weight linear polyethylenimines (<10 kD) are more suitable for gene delivery than the commercially available higher molecular weight polyethylenimines (25 kD) and (2) the cross-linking of the non-toxic low molecular weight polyethylenimines via biodegradable linkage is a viable approach to improving PEI transfection efficiency without significantly increasing the cytotoxicity.