Efficient siRNA delivery with non-viral polymeric vehicles

Structural contributions of blocked or grafted poly(2-dimethylaminoethyl methacrylate) on PEGylated polycaprolactone nanoparticles in siRNA delivery

The multiformity in polymer structure and conformation design provides a great potential in improving the gene silencing efficiency of siRNA by polymer vectors. In order to provide information on the polymer design for siRNA delivery, the structural contributions of blocked or grafted poly(2-dimethylaminoethyl methacrylate) on PEGylated polycaprolactone nanoparticles (NPs) in siRNA delivery were studied. Herein, two kinds of self-assembly nanoparticles (NPs) formed by amphiphilic cationic polymers, methoxy poly(ethylene glycol)-block-polycaprolactone-block-poly(2-dimethylaminoethyl methacrylate) (mPEG-PCL-b-PDMAEMA, PECbD) and methoxy poly(ethylene glycol)-block-(polycaprolactone-graft-poly(2-dimethylaminoethyl methacrylate)) (mPEG-PCL-g-PDMAEMA, PECgD), were used to deliver siRNA for in vitro and in vivo studies. The physiochemical properties including size and zeta potential of PECbD NPs/siRNA and PECgD NPs/siRNA complexes were characterized. In vitro cytotoxicity, cellular uptake and siRNA knockdown efficiency were evaluated in HeLa-Luc cells. The endosome escape and intracellular distribution of PECbD NPs/siRNA and PECgD NPs/siRNA in HeLa-Luc cells were also observed. In vivo polymer mediated siRNA delivery and the complexes distribution in isolated organs were studied using mice and tumor-bearing mice. At the same total degree of polymerization (DP) of DMAEMA, PECgD NPs/siRNA complexes possessed higher zeta potentials than PECbD NPs/siRNA complexes (at the same N/P ratio), which may be the reason that PECgD NPs/siRNA complexes can deliver more siRNA into the cytoplasm and lead to higher in vitro luciferase and lamin A/C silencing efficiency than PECbD NPs/siRNA complexes. The in vivo imaging measurement and histochemical analysis also confirmed that siRNA could be delivered to lungs, livers, pancreas and HeLa-Luc tumors more efficiently by PECgD NPs than PECbD NPs. Meanwhile, the PDMAEMA chains of PECgD could be shortened which provides benefits for clearing. Therefore, PECgD NPs have great potential to be used as efficient non-viral carriers for in vivo siRNA delivery.

Cationic liposomal co-delivery of small interfering RNA and a MEK inhibitor for enhanced anticancer efficacy

PURPOSE

To test whether co-delivery of anticancer small interfering RNA (siRNA) and a chemical MEK inhibitor using cationic liposomes enhances anticancer activity in vitro and in vivo.

METHOD

MEK inhibitor PD0325901 was encapsulated in lipid layers of N',N''-dioleylglutamide-based cationic liposomes (DGL). Mcl1-specific siRNA (siMcl1) was complexed to DGL or PD0325901-loaded liposomes (PDGL). Efficiency of cellular siRNA delivery was tested using fluorescent double-stranded RNA. Silencing of target proteins was evaluated using Western blotting and real-time quantitative polymerase chain reactions. In vivo anticancer activity was tested using xenografted mice.

RESULTS

Size and zeta potential of PDGL were similar to DGL. PDGL could deliver double-stranded RNA into cells with efficiencies comparable to DGL. Cellular co-delivery of siMcl1 and PD0325901 reduced expression of Mcl1 and pERK1/2 proteins and more effectively reduced tumor cell survival than other treatments. In mice, siMcl1 and PD0325901 co-delivered by PDGL inhibited growth of tumors 79%. Substantial apoptosis of tumor cells was observed following PDGL-mediated co-delivery of siMcl1, but not in other groups.

CONCLUSIONS

PDGL-mediated co-delivery of siMcl1 and MEK inhibitor, PD0325901, could serve as a potential strategy for combination chemogene anticancer therapy.

Synthesis and characterization of mannosylated pegylated polyethylenimine as a carrier for siRNA

Regulation of gene expression using small interfering RNA (siRNA) is a promising strategy for research and treatment of numerous diseases. In this study, we develop and characterize a delivery system for siRNA composed of polyethylenimine (PEI), polyethylene glycol (PEG), and mannose (Man). Cationic PEI complexes and compacts siRNA, PEG forms a hydrophilic layer outside of the polyplex for steric stabilization, and mannose serves as a cell binding ligand for macrophages. The PEI-PEG-mannose delivery system was constructed in two different ways. In the first approach, mannose and PEG chains are directly conjugated to the PEI backbone. In the second approach, mannose is conjugated to one end of the PEG chain and the other end of the PEG chain is conjugated to the PEI backbone. The PEI-PEG-mannose delivery systems were synthesized with 3.45-13.3 PEG chains and 4.7-3.0 mannose molecules per PEI. The PEI-PEG-Man-siRNA polyplexes displayed a coarse surface in Scanning Electron Microscopy (SEM) images. Polyplex sizes were found to range from 169 to 357 nm. Gel retardation assays showed that the PEI-PEG-mannose polymers are able to efficiently complex with siRNA at low N/P ratios. Confocal microscope images showed that the PEI-PEG-Man-siRNA polyplexes could enter cells and localized in the lysosomes at 2h post-incubation. Pegylation of the PEI reduced toxicity without any adverse reduction in knockdown efficiency relative to PEI alone. Mannosylation of the PEI-PEG could be carried out without any significant reduction in knockdown efficiency relative to PEI alone. Conjugating mannose to PEI via the PEG spacer generated superior toxicity and gene knockdown activity relative to conjugating mannose and PEG directly onto the PEI backbone.

Research progress on siRNA delivery with nonviral carriers

RNA interference is a powerful method for the knockdown of pathologically relevant genes. Small interfering RNAs (siRNAs) have been widely demonstrated as effective biomedical genetic-therapy applications for many diseases. Unfortunately, siRNA duplexes are not ideal drug-like molecules. Problems hindering their effective application fundamentally lie in their delivery, stability, and off-target effects. Delivery systems provide solutions to many of the challenges facing siRNA therapeutics. Due to some fatal disadvantages of viral vectors, nonviral carriers have been studied extensively. Aside from liposomes, nanoparticles and cationic polymer carriers have exhibited improved in vivo stability, better biocompatibility, and efficiency for gene silencing with less cellular toxicity. They may represent a promising strategy for siRNA-based therapies, especially as nanomaterials. The present review also summarizes other methods of siRNA delivery and the side effects of the nanoparticles.

RNA interference therapy via functionalized scaffolds

Tissue engineering aims to provide structural and biomolecular cues to compromised tissues through scaffolds. An emerging biomolecular cue is that of RNA interference by which the expression of genes can be silenced through a potent endogenous pathway. Recombinant viral-based approaches in RNAi delivery exist; however non-viral strategies offer many opportunities to exploit this mechanism of regulation in a safer way. Current RNAi therapies in clinical trials are without a vector (naked) or have slightly modified structures. Modification of these molecules with efficient backbone moieties for improved stability and potency, protecting and buffering them with delivery vehicles, and using scaffolds as reservoirs of delivery is at the frontier of current research. However, to enable an efficient sustained therapeutic effect scaffolds have a potentially significant role to play. This review presents non-viral delivery of RNAi that have been attempted via tissue engineered scaffolds. For RNAi to have a clinical impact, it is imperative to evaluate optimal delivery systems to ensure that the efficacy of this promising technology can be maximized.

Co-delivery of small interfering RNA and plasmid DNA using a polymeric vector incorporating endosomolytic oligomeric sulfonamide

Cationic polymers are potential intracellular carriers for small interfering RNA (siRNA). The short and rigid nature of an siRNA chain often results in larger and more loosely packed particles compared to plasmid DNA (pDNA) after complexing with carrier polycations, and in turn, poor silencing effects are seen against the target mRNAs. A helper polyanion, pDNA, was incorporated along with siRNA to form compact nanosized polyplexes. At C/A (cation/anion) ratios of 2 and 5, poly(l-lysine) (PLL)/siRNA-pGFP and PLL/siRNA-pGFP-OSDZ (oligomeric sulfadiazine (OSDZ) for endosomolysis) complexes produced particles 90-150 nm in size with a 15-45 mV surface charge, while PLL/siRNA complexes yielded particles 1-2 μm in size at the same C/A ratios. The PLL/siRNA-pGFP (C/A 2) complexes showed significantly higher specific gene silencing (50-90% vs. 10-25%) than the complexes formed at C/A 5. PLL/siRNA-pGFP-OSDZ (C/A 2) complexes improved the specific gene silencing (90%) more dramatically than PLL/siRNA-pGFP (C/A 2) complexes (50%), demonstrating a potential role for OSDZ. PLL/siRNA-pGFP-OSDZ (C/A 2) complexes sustained higher specific gene silencing compared with PLL/siRNA-pGFP (C/A 2) complexes. Other oligomeric sulfonamides (OSA) with varying pK(a) used in PLL/siRNA-pGFP-OSA complexes also caused effective gene silencing. The pGFP in the PLL/siRNA-pGFP complexes successfully expressed GFP protein without interfering with the siRNA. In conclusion, this study demonstrates that long pDNA helps effectively form nanosized siRNA particles and that OSA enhances specific gene silencing. In a single nucleic acid carrier formulation, co-delivery of siRNA and pDNA is feasible to maximize therapeutic effects or to include therapeutic or diagnostic functionalities.

Polyethylenimine-carbon nanotube nanohybrids for siRNA-mediated gene silencing at cellular level

Carbon nanotubes (CNTs) covalently modified with low molecular weight polyethylenimine (PEI) are able to bind and deliver siRNA to cells with higher efficacy than a reference lipidic carrier. The performances of the nanohybrid are rationalized by the combination of the cell penetration and endosomal escape properties of CNTs and PEI, respectively.

Plasmid-based Stat3 siRNA delivered by hydroxyapatite nanoparticles suppresses mouse prostate tumour growth in vivo

DNA vector-based Stat3-specific RNA interference (si-Stat3) blocks Stat3 signalling and inhibits prostate tumour growth. However, the antitumour activity depends on the efficient delivery of si-Stat3. The effects on the growth of mouse prostate cancer cells of si-Stat3 delivered by hydroxyapatite were determined in this study. RM-1 tumour blocks were transplanted into C57BL/6 mice. CaCl₂-modified hydroxyapatite carrying si-Stat3 plasmids were injected into tumours, and tumour growth and histology were determined. The expression levels of Stat3, pTyr-Stat3, Bcl-2, Bax, Caspase3, VEGF and cyclin D1 were measured by western blot analysis. Amounts of apoptosis in cancer cells were analysed with immunohistochemistry and the terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) assay. The results showed that hydroxyapatite-delivered si-Stat3 significantly suppressed tumour growth up to 74% (P < 0.01). Stat3 expression was dramatically downregulated in the tumours. The immunohistochemistry and TUNEL results showed that si-Stat3-induced apoptosis (up to 42%, P < 0.01). The Stat3 downstream genes Bcl-2, VEGF and cyclin D1 were also strongly downregulated in the tumour tissues that also displayed significant increases in Bax expression and Caspase3 activity. These results suggest that hydroxyapatite can be used for the in vivo delivery of plasmid-based siRNAs into tumours.

Smart siRNA delivery systems based on polymeric nanoassemblies and nanoparticles

RNA interference is a post-transcriptional gene-silencing pathway induced by double-stranded small interfering RNA (siRNA). The potential use of siRNA as a therapeutic agent has attracted great attention as a novel approach to the treatment of several intractable diseases. Despite the rapid progress in the therapeutic use of siRNA, systemic application is still controversial due to the limitations of siRNA, such as low enzymatic tolerability, cellular internalization and body distribution after systemic administration. This review describes the recent progress and strategies of siRNA delivery systems based on polyion complexes. Numerous siRNA-containing polyion complex systems bound together through electrostatic interactions between the negatively charged siRNA and positively charged components, including synthetic polymers, biopolymers and nanoparticles, have been developed for the therapeutic application of siRNA. Additionally, stimulus-sensitive smart siRNA carrier systems, including bioreducible polycations and hydrophilic polymer-siRNA conjugates, have been developed to enhance the gene-silencing efficacy of siRNAs.

Delivery of small interfering RNA with a synthetic collagen poly(Pro-Hyp-Gly) for gene silencing in vitro and in vivo

Silencing gene expression by small interfering RNAs (siRNAs) has become a powerful tool for the genetic analysis of many animals. However, the rapid degradation of siRNA and the limited duration of its action in vivo have called for an efficient delivery technology. Here, we describe that siRNA complexed with a synthetic collagen poly(Pro-Hyp-Gly) (SYCOL) is resistant to nucleases and is efficiently transferred into cells in vitro and in vivo, thereby allowing long-term gene silencing in vivo. We found that the SYCOL-mediated local application of siRNA targeting myostatin, coding a negative regulator of skeletal muscle growth, in mouse skeletal muscles, caused a marked increase in the muscle mass within a few weeks after application. Furthermore, in vivo administration of an anti-luciferase siRNA/SYCOL complex partially reduced luciferase expression in xenografted tumors in vivo. These results indicate a SYCOL-based non-viral delivery method could be a reliable simple approach to knockdown gene expression by RNAi in vivo as well as in vitro.

Comparative in vivo study of poly(ethylene imine)/siRNA complexes for pulmonary delivery in mice

Pulmonary siRNA delivery offers a new way to treat various lung diseases. Poly(ethylene imines) (PEIs) are promising cationic nanocarriers and various modifications are still under investigations to improve their cytotoxicity and efficacy for siRNA delivery. In this study, we analyzed two different types of PEI-based nanocomplexes in mice after intratracheal administration regarding their toxicity and efficacy in the lungs. Ubiquitously enhanced green fluorescent protein (EGFP) expressing transgenic and BALB/c mice were intratracheally instilled with 35μg siRNA complexed with the different types of PEI nanocarriers. Lung toxicity and inflammation were investigated after 24h, 3d and 7d treatment and knockdown of EGFP expression was analyzed by flow cytometry and fluorescence microscopy five days post instillation. Three different polyplexes caused more than 60% knockdown of EGFP expression, but only the fatty acid modified low molecular weight PEI 8.3kDa (C16-C18-EO25)1.4 specifically reduced EGFP expression in CD45+ leucocytes (25±12%) and CD11b-/CD11c+ lung macrophages (36±14%). Hydrophobic and hydrophilic PEG modifications on PEI caused severe inflammatory response and elevated levels of IgM in broncho-alveolar fluid (BALF). Thus, the PEG modification reduced cytotoxicity, but elevated the immune response and proinflammatory effects. Further investigations of the proinflammatory and immunomodulatory effects of the PEI-modified carriers are necessary to clarify the highly unspecific knockdown effects in the lung in more detail. Nevertheless, the more hydrophobic modification of PEI based non-viral vector system appeared to be a promising approach for improved siRNA therapeutics offering successful pulmonary siRNA delivery.

Combinatorial approach to determine functional group effects on lipidoid-mediated siRNA delivery

The application of RNA interference (RNAi), either in the clinic or in the laboratory, requires safe and effective delivery methods. Here, we develop a combinatorial approach to synthesize a library of delivery vectors based on two lipid-like substrates with known siRNA delivery capabilities. Members of this library have a mixture of lipid-like tails and feature appendages containing hydroxyl, carbamate, ether, or amine functional groups as well as variations in alkyl chain length and branching. Using a luciferase reporter system in HeLa cells, we studied the relationship between lipid chemical modification and delivery performance in vitro. The impact of the functional group was shown to vary depending on the overall amine content and tail number of the delivery vector. Additionally, in vivo performance was evaluated using a Factor VII knockdown assay. Two library members, each containing ether groups, were found to knock down the target protein at levels comparable to those of the parent delivery vector. These results demonstrate that small chemical changes to the delivery vector impact knockdown efficiency and cell viability both in vitro and in vivo. The work described here identifies new materials for siRNA delivery and provides new insight into the parameters for optimized chemical makeup of lipid-like siRNA delivery materials.

Controlled release of anti-inflammatory siRNA from biodegradable polymeric microparticles intended for intra-articular delivery to the temporomandibular joint

PURPOSE

As the next step in the development of an intra-articular controlled release system to treat painful temporomandibular joint (TMJ) inflammation, we developed several biodegradable poly(DL-lactic-co-glycolic acid) (PLGA)-based microparticle (MP) formulations encapsulating a model anti-inflammatory small interfering RNA (siRNA) together with branched poly(ethylenimine) (PEI) as a transfecting agent. The effect of siRNA loading and N:P ratio on the release kinetics of siRNA-PEI polyplexes was determined, and the size and N:P ratio of the polyplexes released over time was characterized.

METHODS

Polyplex-loaded PLGA MPs were prepared using an established double emulsion technique. Increasing the pH of the release samples enabled siRNA-PEI dissociation and subsequent measurement of the release of each component over 28 days. Polyplex diameter was measured for all release samples and compared to freshly prepared siRNA-PEI under simulated physiologic conditions.

RESULTS

Systematic variation of siRNA loading and N:P ratio resulted in distinct siRNA and PEI release profiles. Polyplex diameter remained constant despite large variations in the relative amounts of siRNA and PEI. Excess PEI was sequestered through complexation with 500-1,000 nm diameter PLGA MP-derived particles, including small MPs and PLGA degradation products.

CONCLUSIONS

These PLGA MP formulations show exciting potential as the first intra-articular TMJ controlled release system.

siRNA applications in nanomedicine

The ability to specifically silence genes using RNA interference (RNAi) has wide therapeutic applications for the treatment of disease or the augmentation of tissue formation. RNAi is the sequence-specific gene silencing mediated by a 21-25 nucleotide double-stranded small interfering RNA (siRNA) molecule. siRNAs are incorporated into the RNA-induced silencing complex (RISC), which mediates mRNA sequence-specific binding and cleavage. Although RNAi has the potential to be a powerful therapeutic drug, its delivery remains a major limitation. The generation of nanosized particles is being investigated to enhance the delivery of siRNA-based drugs. These nanoparticles are generally designed to overcome one or more of the barriers encountered by the siRNA when trafficked to the cytosol. In this review, we will discuss recent advances in the design of delivery strategies for siRNA, focusing our attention to those strategies that have had in vivo success or have introduced novel functionality that allowed enhanced intracellular trafficking and/or cellular targeting. First, we will discuss the different barriers that must be overcome for efficient siRNA delivery. Second, we will discuss the approaches for siRNA delivery by size including direct modification of siRNAs (less than 10 nm), self-assembled particles based on cationic polymers and cationic lipids (100-300 nm), neutral liposomes (<200 nm), and macroscale matrices that contain naked siRNA or siRNA loaded nanoparticles (>100 microm). Finally, we will briefly discuss recent in vivo therapeutic success.

Carbonate apatite-facilitated intracellularly delivered siRNA for efficient knockdown of functional genes

Gene therapy through intracellular delivery of a functional gene or a gene-silencing element is a promising approach to treat critical diseases. Elucidation of the genetic basis of human diseases with complete sequencing of human genome revealed many vital genes as possible targets in gene therapy programs. RNA interference (RNAi), a powerful tool in functional genomics to selectively silence messenger RNA (mRNA) expression, can be harnessed to rapidly develop novel drugs against any disease target. The ability of synthetic small interfering RNA (siRNA) to effectively silence genes in vitro and in vivo, has made them particularly well suited as a drug therapeutic. However, since naked siRNA is unable to passively diffuse through cellular membranes, delivery of siRNA remains the major hurdle to fully exploit the potential of siRNA technology. Here pH-sensitive carbonate apatite has been developed to efficiently deliver siRNA into the mammalian cells by virtue of its high affinity interactions with the siRNA and the desirable size of the resulting siRNA/apatite complex for effective cellular endocytosis. Moreover, following internalization by cells, siRNA was found to be escaped from the endosomes in a time-dependent manner and finally, more efficiently silenced reporter genes at a low dose than commercially available lipofectamine. Knockdown of cyclin B1 gene with only 10nM of siRNA delivered by carbonate apatite resulted in the significant death of cancer cells, suggesting that the new method of siRNA delivery is highly promising for pre-clinical and clinical cancer therapy.

The development and mechanism studies of cationic chitosan-modified biodegradable PLGA nanoparticles for efficient siRNA drug delivery

PURPOSE

In order to improve siRNA delivery for possible clinical applications, we developed biodegradable chitosan-modified poly(D,L-lactide-co-glycolide) (CHT-PLGA) nanoparticles with positive surface charge, high siRNA loading, high transfection efficiency and low toxicity.

METHODS

CHT-PLGA nanoparticles were prepared, and siRNA was loaded by emulsion evaporation method with poly(vinyl alcohol) (PVA) as emulsifier. siRNA loading efficiency, particle size, and Zeta potential of nanoparticles were measured. Gel retardation and protection assays were conducted to determine the loading and binding of siRNA in the formulation. Cell transfection was performed to study in vitro siRNA silencing efficiency. XTT assay was used to evaluate the cytotoxicity.

RESULTS

It was found that the nanoparticle diameter and positive Zeta potential increase as the chitosan coating concentration increases. CHT-PLGA nanoparticles showed excellent siRNA binding ability and effective protection of oligos from RNase degradation. siRNA-loaded nanoparticles were successfully delivered into the HEK 293 T cell line, and the silencing of green fluorescence protein (GFP) expression was observed using fluorescent microscopy and flow cytometry. In addition, the cytotoxicity assay revealed that CHT-PLGA nanoparticles had relatively low cytotoxicity.

CONCLUSION

This study suggests that biodegradable cationic CHT-PLGA nanoparticles possess great potential for efficient and safer siRNA delivery in future clinical applications.

Carbon nanotubes in cancer diagnosis and therapy

During the past years, great progress has been made in the field of nanomaterials given their great potential in biomedical applications. Carbon nanotubes (CNTs), due to their unique physicochemical properties, have become a popular tool in cancer diagnosis and therapy. They are considered one of the most promising nanomaterials with the capability of both detecting the cancerous cells and delivering drugs or small therapeutic molecules to these cells. Over the last several years, CNTs have been explored in almost every single cancer treatment modality, including drug delivery, lymphatic targeted chemotherapy, thermal therapy, photodynamic therapy, and gene therapy. In this review, we will show how they have been introduced into the diagnosis and treatment of cancer. Novel SWNT-based tumor-targeted drug delivery systems (DDS) will be highlighted. Furthermore, the in vitro and in vivo toxicity of CNTs reported in recent years will be summarized.

Chemically programmed polymers for targeted DNA and siRNA transfection

Plasmid DNA and siRNA have a large potential for use as therapeutic nucleic acids in medicine. The way to the target cell and its proper compartment is full of obstacles. Polymeric carriers help to overcome the encountered barriers. Cationic polymers can interact with the nucleic acid in a nondamaging way but still require optimization with regard to transfer efficiency and biocompatibility. Aiming at virus-like features, as viruses are the most efficient natural gene carriers, the design of bioresponsive polymers shows promising results regarding DNA and siRNA delivery. By specific chemical modifications dynamic structures are created, programmed to respond towards changing demands on the delivery pathway by cleavage of labile bonds or conformational changes, thus enhancing biocompatible gene delivery.

Chitosan-modified poly(D,L-lactide-co-glycolide) nanospheres for improving siRNA delivery and gene-silencing effects

Chitosan (CS) surface-modified poly(d,l-lactide-co-glycolide) (PLGA) nanospheres (NS) for a siRNA delivery system were evaluated in vitro. siRNA-loaded PLGA NS were prepared by an emulsion solvent diffusion (ESD) method, and the physicochemical properties of NS were investigated. The level of targeted protein expression and siRNA uptake were examined in A549 cells. CS-modified PLGA NS exhibited much higher encapsulation efficiency than unmodified PLGA NS (plain-PLGA NS). CS-modified PLGA NS showed a positive zeta potential, while plain-PLGA NS were negatively charged. siRNA uptake studies by observation with confocal leaser scanning microscopy (CLSM) indicated that siRNA-loaded CS-modified PLGA NS were more effectively taken up by the cells than plain-PLGA NS. The efficiencies of different siRNA preparations were compared at the level of targeted protein expression. The gene-silencing efficiency of CS-modified PLGA NS was higher and more prolonged than those of plain-PLGA NS and naked siRNA. This result correlated with the CLSM studies, which may have been due to higher cellular uptake of CS-modified PLGA NS due to electrostatic interactions. It was concluded that CS-modified PLGA NS containing siRNA could provide an effective siRNA delivery system.

Development of pH-responsive nanocarriers using trimethylchitosans and methacrylic acid copolymer for siRNA delivery

RNA interference-based therapies are dependent on intracellular delivery of siRNA. The release of siRNA from the endosomal compartment may be a rate limiting step in the transfection process. The purpose of this study was to produce pH-responsive nanocarriers made of trimethylchitosan (TMC). To this end, pH-sensitive methacrylic acid (MAA) copolymer was added to TMC-siRNA formulations. Four different TMCs associated or not with MAA were evaluated as siRNA carriers. Nanoparticles were characterized in terms of size, surface charge, morphology and interaction with siRNA. A swelling behaviour due to a decrease in pH was observed and was found to be dependent on MAA content in the complexes. In vitro experiments aimed at evaluating how the capacity of the nanocarriers to transfect siRNA in L929 cells was affected by MAA content. Confocal microscopy experiments showed that fluorescent MAA-containing particles exhibit a different distribution pattern inside the cells comparing to their counterpart without this pH-sensitive polymer. Transfection efficiency was investigated by RhoA mRNA expression inhibition. MAA-TMC-siRNA complexes were able to transfect L929 cells with greater efficiency than corresponding TMC-siRNA complexes. This study gives an insight into the opportunity of pH-sensitive nanocarriers for siRNA delivery. Such formulations may represent an attractive strategy to improve endosomal escape of siRNA.

Electrically assisted delivery of macromolecules into the corneal epithelium

Electrically assisted delivery is noninvasive and has been investigated in a number of ocular drug delivery studies. The objectives of this study were to examine the feasibility of electrically assisted delivery of macromolecules such as small interfering RNA (siRNA) into the corneal epithelium, to optimize the iontophoresis and electroporation methods, and to study the mechanisms of corneal iontophoresis for macromolecules. Anodal and cathodal iontophoresis, electroporation and their combinations were the methods examined with mice in vivo. Cyanine 3 (Cy3)-labeled glyceraldehyde-3-phosphate dehydrogenase (GAPDH) siRNA and fluorescein isothiocyanate (FITC)-labeled dextran of different molecular weights (4-70 kDa) were the macromolecules studied. Microscopy and histology after cryostat sectioning were used to analyze and compare the delivery of the macromolecules to the cornea. Iontophoresis was effective in delivering siRNA and dextran up to 70 kDa into the cornea. The electroporation method studied was less effective than that of iontophoresis. Although both iontophoresis and electroporation alone can deliver the macromolecules into the cornea, these methods alone were not as effective as the combination of iontophoresis and electroporation (iontophoresis followed by electroporation). The significant enhancement of dextran delivery in anodal iontophoresis suggests that electroosmosis can be a significant flux-enhancing mechanism during corneal iontophoresis. These results illustrate the feasibility of electrically assisted delivery of macromolecules such as siRNA into the cornea.

Surface-engineered targeted PPI dendrimer for efficient intracellular and intratumoral siRNA delivery

Low penetration ability of Small Interfering RNA (siRNA) through the cellular plasma membrane combined with its limited stability in blood, limits the effectiveness of the systemic delivery of siRNA. In order to overcome such difficulties, we constructed a nanocarrier-based delivery system by taking advantage of the lessons learned from the problems in the delivery of DNA. In the present study, siRNA nanoparticles were first formulated with Poly(Propyleneimine) (PPI) dendrimers. To provide lateral and steric stability to withstand the aggressive environment in the blood stream, the formed siRNA nanoparticles were caged with a dithiol containing cross-linker molecules followed by coating them with Poly(Ethylene Glycol) (PEG) polymer. A synthetic analog of Luteinizing Hormone-Releasing Hormone (LHRH) peptide was conjugated to the distal end of PEG polymer to direct the siRNA nanoparticles specifically to the cancer cells. Our results demonstrated that this layer-by-layer modification and targeting approach confers the siRNA nanoparticles stability in plasma and intracellular bioavailability, provides for their specific uptake by tumor cells, accumulation of siRNA in the cytoplasm of cancer cells, and efficient gene silencing. In addition, in vivo body distribution data confirmed high specificity of the proposed targeting delivery approach which created the basis for the prevention of adverse side effects of the treatment on healthy organs.