The remaining DNA staining is seen near the loading well indicative of liposome encapsulated plasmid. In lane 5 the sample has been digested with a mixture of DNase I and Exonuclease III [20], hence the free DNA, migrating as a 5 kb-band seen in lane 4 is lost, and only DNA protected in the liposome is seen near the loading well of the gel. Using standards of purified plasmid the PicoGreen assay was used to determine the DNA concentration in lane 4 and 5 and was estimated to be 18 μg DNA per 200 μl SPLP preparation used for one tailvein injection, an overall yield of 45% plasmid encapsulation. A tritium-labeled tracer lipid was added in the formulation and by scintillation FDA-approved Drug Library screening counting we found that the recovery

of lipids in the preparation was almost complete yielding 4 μmol total lipid in 200 μl buffer. We decided to exploit FG-4592 research buy the use of the SPLPs seen in lane 4 as the amount of plasmid DNA bound externally and released upon electrophoresis was very low. The SPLPs used for in vivo studies were characterized regarding their size and charge using dynamic light scattering. SPLP sample measurements yielded

a narrow size distribution (1–3 nm) with an average of 144 nm±13 nm (standard error of mean, n=3), a low polydispersity index (0.1±0.01) and a slightly negative zeta potential (−6.2±1.3). These properties are favorable for long-term circulation in that the size should be low and not positive as this causes retardation in first-pass organs, whereas the neutral or slightly negative charge allows for long circulation time in the system [4]. The dual properties of nanoparticles to be stably, long-circulating and at the same time yield transfection

in target tissue require exploitation of the transfection properties. Dialyzed SPLPs containing pCMV-LUC plasmid (∼0.8 μg) were added in full growth medium to tissue culture cells either easy to transfect, adherent lung cancer cells H1299 or hard-to-transfect suspension small cell lung cancer cells NCI-H69 and the luciferase reporter Montelukast Sodium activity was analyzed two days later (Fig. 2). Compared to cationic lipoplex-mediated transfection [21] a moderate activity was measured in H1299 (14±4 pg luc per mg protein) and a low activity was measured in NCI-H69 cells (0.7±0.2 pg luc per mg protein). Since we recently showed that the pharmacokinetics of cationic lipoplexes were poor for systemic treatment of xenograft flank tumors [21], we decided to investigate the use of SPLPs in our xenograft tumor model. Furthermore, NCI-H69 tumor microenvironment may be very different from growth in suspension in culture media and this could potentially have a beneficial effect in relation to transfection from accumulating SPLPs. The SPLPs with encapsulated plasmid DNA were tested in vivo using nude mice carrying xenograft flank tumors originating from human small cell lung cancer [13]. Animals were carrying 1–2 subcutaneous tumors on the flanks and used for experiments when tumors had reached 200–800 mm3 in size.