The purpose of this study was to assess the relative advantages and drawbacks of the nanoprecipitation-solvent displacement method for a range of drugs with respect to the particle size and drug encapsulation in polylactic-co-glycolic acid (PLGA) nanoparticles. The particle size analysis indicated a unimodal particle size distribution in all systems, with a mean diameter of 160-170 nm, except for insulin nanoparticles, which showed a smaller particle size. The results of the encapsulation efficiency analysis demonstrated that more lipophilic drugs, such as cyclosporin and indomethacin, do not suffer from the problems of drug leakage to the external medium, resulting in improved drug content in the nanoparticles. In spite of the fact that valproic acid is a liquid that is very sparingly soluble in water, very low encapsulation efficiency was obtained. Ketoprofen, a drug sparingly soluble in water, demonstrated intermediate values of encapsulation that were well correlated with its intermediate lipophilicity. More hydrophilic drugs, such as vancomycin and phenobarbital, were poorly encapsulated in PLGA nanoparticles. Insulin was preferentially surface bound on the PLGA nanoparticles. However, a strong hypoglycemic effect of the insulin was observed after administration of the suspension of PLGA nanoparticles with surface-bound insulin to the ileum loop of male Wistar rats.

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Cationic liposomes (CL) are one of the most widely studied non-viral vectors for gene delivery. It is wellknown that CL induces cytotoxicity following lipofection. However, little is known regarding the mechanism involved in the cytotoxicity. In this study, the in vitro cytotoxicity of CL and its complex with pDNA (lipoplex) was investigated, and a part of the mechanism of induction as well. While free pDNA did not show any cytotoxicity, pDNA increased the cytotoxicity of CL via the formation of lipoplex. In addition, the lipoplex-induced cytotoxicity increased in a lipoplex dose-dependent manner, irrespective of the type of pDNA, cell line and the absence or presence of serum. An assay showed that apoptosis was largely induced by treatment with the lipoplex (lipofection), but not with CL alone, in the tested range of concentration of CL and pDNA. Furthermore, following treatment with lipoplexes, the cells exhibited the morphological features of apoptosis and DNA fragmentation. A cDNA microarray study showed that the lipofection up-regulated 45 genes related to apoptosis, transcription regulation and immune response. These results clearly indicate that pDNA in the lipoplex increases the cytotoxicity of CL as a result of inducing apoptosis. The fundamental principle for gene therapy is to deliver gene-based therapeutics to target cells for specific gene targeting with minimal cytotoxicity. Our results suggest the possibility that cytotoxicity induced by lipofection, accompanied by gene changes, could intrinsically exacerbate, attenuate or even mask the desired effects of gene-based therapy.