Uptake of oligonucleotide-loaded nanoparticles in prostatic cancer cells and their intracellular localization.

The development of antisense biotechnology is dependent, in part, on creating improved methods for delivering oligonucleotides to cells. In this study, we investigated a colloidal system (nanoparticles (NP) of poly (D,L) lactic acid) that affects the intracellular delivery of oligonucleotides. We have examined the intracellular compartmentalization in DU145 cells of fluorescein labeled phosphorothioate oligonucleotides, both in the free state and when loaded into NP. Fluorescent oligonucleotides were incubated for 18 h with DU145 cells and the mean intracellular fluorescence was determined by flow cytometry. After the addition of monensin, an increase in signal intensity was observed, indicating that free oligonucleotides were resident in an acidic intracellular environment, whereas oligonucleotides from the NP did not reside in an acidic compartment. Free and NP loaded with oligonucleotides effluxed from DU145 cells from two intracellular compartments. This preliminary report indicates that colloidal carriers such as NP could prove to be useful in affecting intracellular trafficking of oligonucleotides in DU145 and in other cells.

Highly loaded nanoparticulate carrier using an hydrophobic antisense oligonucleotide complex.

Antisense oligonucleotides, and particularly those with phosphorothioate backbones, have emerged as potential gene specific therapeutic agents and are currently undergoing evaluation in clinical trials for a variety of diseases. In the area of HIV-1 therapeutics, targeting of oligonucleotides to infected cells, such as macrophages, would be highly desirable. The present study was designed to prepare and characterize oligonucleotide-loaded nanoparticles for this purpose. Due to their hydrophilic characteristics, oligonucleotides are difficult to entrap in polymeric particles. Here, the oligonucleotides were first complexed with cetyltrimethylammonium bromide. The oligonucleotide-loaded nanoparticles were prepared by the emulsification-diffusion method and subsequently purified. In comparison with previous studies, a high oligonucleotide-loading was achieved; 2.5, 5 and 10% oligonucleotide loading were assessed. If the initial oligonucleotide content was 4%, this method produced a final oligonucleotide loading of 1.9% with an entrapment efficiency of 47%. The integrity of the oligonucleotide and of the polymer, in the final freeze-dried product, was retained.

Comparison of two methods of encapsulation of an oligonucleotide into poly(D,L-lactic acid) particles.

The aim of this study was to compare two methods to encapsulate a 25-mer-phosphorothioate oligonucleotide (ODN) into poly(D,L-lactic acid) (PLA) particles. Antisense oligonucleotides belong to a new therapeutic class especially attractive for the treatment of cancers and viral diseases. The development of these new drugs suffers, however, from poor stability in biological media and very low cellular uptake. Polymeric particulate systems display interesting features for ODN delivery. ODN are highly hydrophilic and most encapsulation methods are inappropriate for such molecules. Using poly(D,L-lactide) polymer, two methods of encapsulation were compared. First, a double emulsion technique was used to prepare nano- and microparticles. Secondly, the ODN was combined with a quaternary ammonium, the cethyltrimethyl-ammonium bromide (CTAB), to enhance the hydrophobicity of the molecule before entrapment by the emulsification-diffusion method. Both methods led to the formation of individualized and spherical particles loaded with a significant amount of ODN. Similar entrapment efficiencies were obtained for the nanoparticles prepared by both methods (approx. 27% of the theoretical loading) whereas 45% of entrapment efficiency was observed for the microparticles. Seventy five percent of the ODN were released in 60 min with the particles prepared by the emulsification-diffusion method, whereas only 7% were released in 60 h when using the double emulsion method. A viability test on U-937 cells showed better survival rates with the particles prepared by the double emulsion technique. The results suggest that the location of the ODN in the polymeric matrix is affected by the encapsulation method. Particles containing CTAB appeared more toxic than the ones obtained by the double emulsion technique, however, these particles can still be used for antisense activity since high oligonucleotide loading can be achieved.

CD40 expression by gingival fibroblasts: correlation of phenotype with function.

CD40, a member of the tumor necrosis factor-alpha receptor family, is constitutively expressed by cells of hematopoietic and non-hematopoietic origin, including fibroblasts. Signaling through this receptor molecule regulates inflammatory cytokine secretion by many cell types. Based on the recently described cytokine secretory heterogeneity of fibroblast cell subsets, we hypothesized that secretion of inflammatory cytokines by gingival fibroblast cultures may be dictated by the existence of differential proportions of cytokine-secreting subpopulations which express high levels of CD40. After examining a large number of gingival fibroblast (GF) cultures we find that the frequency of IL-6- and IL-8-secreting cells mirrors the frequency of cells expressing high levels of CD40 in these cultures. In addition, we demonstrate a direct functional relationship between CD40 expression and IL-6 or IL-8 secretion by showing that ligation of this molecule on GF, and CD40+ fibroblast subsets in particular, up-regulates secretion of these cytokines in vitro.

Inhibition of HIV-1 in cell culture by oligonucleotide-loaded nanoparticles.

PURPOSE: To investigate the potential use of polymeric nanoparticles for the delivery of antisense oligonucleotides in HIV-1-infected cell cultures. METHODS: Phosphorothioate oligonucleotides were encapsulated into poly (D,L-lactic acid) nanoparticles. Two models of infected cells were used to test the ability of nanoparticles to deliver them. HeLa P4-2 CD4+ cells, stably transfected with the beta-galactosidase reporter gene, were first used to evaluate the activity of the oligonucleotides on a single-round infection cycle. The acutely infected lymphoid CEM cells were then used to evaluate the inhibition of the viral production of HIV-1 by the oligonucleotides. RESULTS: The addition to infected CEM cells of nanoparticles containing gag antisense oligonucleotides in the nanomolar range led to strong inhibition of the viral production in a concentration-dependent manner. Similar results were previously observed in HeLa P4-2 CD4+ cells. Nanoparticle-entrapped random-order gag oligonucleotides had similar effects on reverse transcription. However, the reverse transcriptase activity of infected cells treated with nanomolar concentrations of free antisense and random oligonucleotides was not affected. CONCLUSIONS: These results suggest that poly (D,L-lactic acid) nanoparticles may have great potential as an efficient delivery system for oligonucleotides in HIV natural target cells, i.e., lymphocytic cells.