Lipid-coated ruthenium dendrimer conjugated with doxorubicin in anti-cancer drug delivery: Introducing protocols

One of the major limitations for the treatment of many diseases is an inability of drugs to cross the cell membrane barrier. Different kinds of carriers are being investigated to improve drug bioavailability. Among them, lipid or polymer-based systems are of special interest due to their biocompatibility. In our study, we combined dendritic and liposomal carriers and analysed the biochemical and biophysical properties of these formulations. Two preparation methods of Liposomal Locked-in Dendrimers (LLDs) systems have been established and compared. Carbosilane ruthenium metallodendrimer was complexed with an anti-cancer drug (doxorubicin) and locked in a liposomal structure, using both techniques. The LLDs systems formed by hydrophilic locking had more efficient transfection profiles and interacted with the erythrocyte membrane better than systems using the hydrophobic method. The results indicate these systems have improved transfection properties when compared to non-complexed components. The coating of dendrimers with lipids significantly reduced their hemotoxicity and cytotoxicity. The nanometric size, low polydispersity index and reduced positive zeta potential of such complexes made them attractive for future application in drug delivery. The formulations prepared by the hydrophobic locking protocol were not effective and will not be considered furthermore as prospective drug delivery systems. In contrast, the formulations formed by the hydrophilic loading method have shown promising results where the cytotoxicity of LLD systems with doxorubicin was more effective against cancer than normal cells.

Dendronized Gold Nanoparticles as Carriers for gp160 (HIV-1) Peptides: Biophysical Insight into Complex Formation

The unavailability of effective and safe human immunodeficiency virus (HIV) vaccines incites several approaches for development of the efficient antigen/adjuvant vaccination composite. In this study, three different dendronized gold nanoparticles (AuNPs 13-15) were investigated for a complexation ability with gp160 synthetic peptides derived from an HIV envelope. It has been shown that HIV peptides interacted with nanoparticles as evident from the changes in their secondary structures, restricted the mobility of the attached fluorescence dye, and enhanced peptide helicity confirmed by the fluorescence polarization and circular dichroism results. Transmission electron microscopy visualized complexes as cloud-like structures with attached nanoparticles. AuNP 13-15 nanoparticles bind negatively charged peptides depending on the number of functional groups; the fastest saturation and peptide retardation were observed for the most dendronized nanoparticle as indicated from dynamic light scattering, laser Doppler velocimetry, and agarose gel electrophoresis experiments. Dendronized gold nanoparticles can be considered one of the potential HIV peptide-based vaccination platforms.

Dendrimers complexed with HIV-1 peptides interact with liposomes and lipid monolayers

AIMS

We have investigated the effect of surface charge of model lipid membranes on their interactions with dendriplexes formed by HIV-derived peptides and 2 types of positively charged carbosilane dendrimers (CBD).

METHODS

Interaction of dendriplexes with lipid membranes was measured by fluorescence anisotropy, dynamic light scattering and Langmuir-Blodgett techniques. The morphology of the complexes was examined by transmission electron microscopy.

RESULTS

All dendriplexes independent of the type of peptide interacted with model lipid membranes. Negatively charged vesicles composed of a mixture of DMPC/DPPG interacted more strongly, and it was accompanied by an increase in anisotropy of the fluorescent probe localized in polar domain of lipid bilayers. There was also an increase in surface pressure of the lipid monolayers. Mixing negatively charged liposomes with dendriplexes increased liposome size and made their surface charges more positive.

CONCLUSIONS

HIV-peptide/dendrimer complexes interact with model lipid membranes depending on their surface charge. Carbosilane dendrimers can be useful as non-viral carriers for delivering HIV-peptides into cells.

Cellular uptake of DNA-chitosan nanoparticles: the role of clathrin- and caveolae-mediated pathways

The success of gene therapy depends on efficient delivery of DNA and requires a vector. A promising non-viral vector is chitosan. We tailored chitosan to optimize it for transfection by synthesizing self-branched and trisaccharide-substituted chitosan oligomers (SBTCO), which show superior transfection efficacy compared with linear chitosan (LCO). The aim of the work was to compare the cellular uptake and endocytic pathways of polyplexes formed by LCO and SBTCO. Both polyplexes were taken up by the majority of the cells, but the uptake of LCO was lower than SBTCO polyplexes. LCO polyplexes were internalized through both clathrin-dependent and clathrin-independent pathways, whereas SBTCO polyplexes were primarily taken up by clathrin-independent endocytosis. The different level of cellular uptake and the distinct endocytic pathways, may explain the difference in transfection efficacy. This was supported by the observation that photochemical internalization increased the transfection by LCO polyplexes considerably, whereas no effect on transfection was found for SBTCO polyplexes.

Abstract 5404: DNA-chitosan nanoparticles in gene delivery: Endocytotic pathways and intracellular trafficking

Background: The success of gene therapy depends on efficient delivery of DNA and efficient transcription of the transgene. This involves several steps, including penetration through the extracellular matrix to target cells, intracellular uptake, and trafficking to the nucleus. A DNA vector is necessary, packing DNA into smaller polyplexes and protecting the DNA from degradation. A promising non-viral vector is chitosan, a cationic polysaccharide derived from chitin. The interactions with DNA and ability to transfect cells depend strongly on intrinsic chitosan properties. We are tailoring the chitosan to optimize transfection and have synthesized self-branched and trisaccharide-substituted chitosan oligomers (SBTCO), which seem to compact DNA less tightly and have shown superior transfection efficiency compared to linear chitosan (LCO) of equivalent molecular weight (1-3). The aim of the present work was to compare the endocytotic pathways and intracellular trafficking of polyplexes formed by SBTCO and LCO, to see if such differences could explain the difference in transfection efficacy.

Material and Methods: Uptake of the two polyplexes in HeLa cells was studied using flow cytometry. Clathrin- and caveolin-dependent endocytosis was compared by inhibiting the two pathways using chlorpromazine, genistein and dynasore. Intracellular trafficking was studied using confocal laser scanning microscopy. Quantitative colocalization of polyplexes with early endosomes and intracellular DNA-chitosan colocalization were performed. The impact of photochemical internalization on transfection was studied by flow cytometric analysis of GFP expression (4).

Results: All three inhibitors reduced the uptake of LCO polyplexes and genistein and dynasore were somewhat more efficient than chlorpromazine. For SBTCO polyplexes chlorpromazine showed little inhibition, whereas genistein and dynasore efficiently inhibited endocytosis. Consistent with this, only a fraction of the polyplexes was found in early endosomes. 60-80% of the intracellular DNA was binding to chitosan the first 4 hrs. Polyplexes of LCO showing low transfection was increased significantly by photochemical internalization.

Conclusion: LCO polyplexes are taken up by cells both by clathrin and caveolin mediated pathways, whereas SBTCO polyplexes are primarily taken up by caveolin mediated endocytosis. The difference in endocytotic pathway results in different intracellular routes and this may explain the difference in transfection efficacy.

1. Reitan et al. Biomacromolecules 10, 2009

2. Strand et al. Biomaterials 31, 2010

3. Strand et al. Biomacromolecules 9, 2008

4. Berg et al Curr. Pharma Biotech 8, 2007

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5404. doi:10.1158/1538-7445.AM2011-5404