Water-soluble carbosilane dendrimers protect phosphorothioate oligonucleotides from binding to serum proteins

Screening Libraries to Discover Molecular Design Principles for the Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers Derived from Plant Phenolic Acids

Viral and synthetic vectors to deliver nucleic acids were key to the rapid development of extraordinarily efficient COVID-19 vaccines. The four-component lipid nanoparticles (LNPs), containing phospholipids, PEG-conjugated lipids, cholesterol, and ionizable lipids, co-assembled with mRNA via a microfluidic technology, are the leading nonviral delivery vector used by BioNTech/Pfizer and Moderna to access COVID-19 mRNA vaccines. LNPs exhibit a statistical distribution of their four components when delivering mRNA. Here, we report a methodology that involves screening libraries to discover the molecular design principles required to realize organ-targeted mRNA delivery and mediate activity with a one-component ionizable multifunctional amphiphilic Janus dendrimer (IAJD) derived from plant phenolic acids. IAJDs co-assemble with mRNA into monodisperse dendrimersome nanoparticles (DNPs) with predictable dimensions, via the simple injection of their ethanol solution in a buffer. The precise location of the functional groups in one-component IAJDs demonstrated that the targeted organs, including the liver, spleen, lymph nodes, and lung, are selected based on the hydrophilic region, while activity is associated with the hydrophobic domain of IAJDs. These principles, and a mechanistic hypothesis to explain activity, simplify the synthesis of IAJDs, the assembly of DNPs, handling, and storage of vaccines, and reduce price, despite employing renewable plant starting materials. Using simple molecular design principles will lead to increased accessibility to a large diversity of mRNA-based vaccines and nanotherapeutics.

Poly(lysine) Dendrimers Form Complexes with siRNA and Provide Its Efficient Uptake by Myeloid Cells: Model Studies for Therapeutic Nucleic Acid Delivery

The disruption of the cellular pathways of protein biosynthesis through the mechanism of RNA interference has been recognized as a tool of great diagnostic and therapeutic significance. However, in order to fully exploit the potential of this phenomenon, efficient and safe carriers capable of overcoming extra- and intracellular barriers and delivering siRNA to the target cells are needed. Recently, attention has focused on the possibility of the application of multifunctional nanoparticles, dendrimers, as potential delivery devices for siRNA. The aim of the present work was to evaluate the formation of dendriplexes using novel poly(lysine) dendrimers (containing lysine and arginine or histidine residues in their structure), and to verify the hypothesis that the use of these polymers may allow an efficient method of siRNA transfer into the cells in vitro to be obtained. The fluorescence polarization studies, as well as zeta potential and hydrodynamic diameter measurements were used to characterize the dendrimer:siRNA complexes. The cytotoxicity of dendrimers and dendriplexes was evaluated with the resazurin-based assay. Using the flow cytometry technique, the efficiency of siRNA transport to the myeloid cells was determined. This approach allowed us to determine the properties and optimal molar ratios of dendrimer:siRNA complexes, as well as to demonstrate that poly(lysine) dendrimers may serve as efficient carriers of genetic material, being much more effective than the commercially available transfection agent Lipofectamine 2000. This outcome provides the basis for further research on the application of poly(lysine) dendrimers as carriers for nucleic acids in the field of gene therapy.

Feasibility of cationic carbosilane dendrimers for sustainable protein sample preparation

Protein sample preparation is the bottleneck in the analysis of proteins. The aim of this work is to evaluate the feasibility of carbosilane dendrimers functionalized with cationic groups to make easier this step. Anionic carbosilane dendrimers (sulphonate- and carboxylate-terminated) have already demonstrated their interaction with proteins and their potential in protein sample preparation. In this work, interactions between positively charged carbosilane dendrimers and different model proteins were studied when working under different pH conditions, dendrimer concentrations, and dendrimer generations. Amino- and trimethylammonium-terminated carbosilane dendrimers presented, in some cases, weak interactions with proteins. Unlike them, carbosilane dendrimers with terminal dimethylamino groups could interact, in many cases, with proteins and these interactions were affected by the pH, the dendrimer concentration, and the dendrimer generation. Moreover, dendrimer precipitation was observed at all pHs, although just second and fourth generation (2 G and 4 G) dendrimers resulted in the formation of complexes with proteins. Under experimental conditions promoting dendrimer-protein interactions, 2 G dimethylamino-terminated dendrimers were proposed as an alternative to other methods used in analytical chemistry or analysis in which an organic solvent or a resin are required to enrich/purify proteins in a complex sample.

ESI-TOF mass spectrometry of cationic carbosilane dendrimers: A potent tool for characterization of structural defects

Macromolecular polyelectrolytes are gaining considerable attention for the application in medicine that implies their detailed characterization. We have successfully applied electrospray ionization mass spectrometry (ESI MS) to the analysis of defects in the structure of three generations of polycationic carbosilane dendrimers bearing series of quarternary phosphonium groups at their periphery. Besides expected defects caused by incomplete conversion of particular reaction steps during the synthesis of dendritic scaffold and subsequent peripheral functionalization, also, several products of side reactions were observed together with defects created in the course of measurement (particularly ion exchange products). Defective molecules can be to some extent separated by means of gel permeation chromatography that proves that they are not products of in source fragmentation processes. Within the reaction sequence used for the synthesis of dendrimers under study, hydrosilylation was the source of most defects; the effectivity of quarternization depends on the type of phosphine. Results confirm high sensitivity of ESI MS towards defects, stability of the carbosilane skeleton towards fragmentation under the conditions of ESI ionization, and capability to detect both lower- and higher-molecular weight impurities arising from the synthetic sequence in the same m/z range as the target dendrimer, thus providing valuable view of the polydispersity.

Phosphonium carbosilane dendrimers for biomedical applications – synthesis, characterization and cytotoxicity evaluation

Phosphonium carbosilane dendrimers could represent an alternative to ammonium ones in gene therapy applications with high potential of mitochondrial targeting.

Anticancer siRNA cocktails as a novel tool to treat cancer cells. Part (B). Efficiency of pharmacological action

This paper examines a perspective to use newly engineered nanomaterials as effective and safe carriers for gene therapy of cancer. Three different groups of cationic dendrimers (PAMAM, phosphorus, and carbosilane) were complexed with anticancer siRNA and the biophysical properties of the dendriplexes created were analyzed. The potential of the dendrimers as nanocarriers for anticancer Bcl-xl, Bcl-2, Mcl-1 siRNAs and additionally a scrambled sequence siRNA has been explored. Dendrimer/siRNA complexes were characterised by various methods including fluorescence, zeta potential, dynamic light scattering, circular dichroism, gel electrophoresis and transmission electron microscopy. In this part of study, the transfection of complexes in HeLa and HL-60 cells was analyzed using both single apoptotic siRNAs and a mixture (cocktail) of them. Cocktails were more effective than single siRNAs, allowing one to decrease siRNAs concentration in treating cells. The dendrimers were compared as siRNA carriers, the most effective being the phosphorus-based ones. However, they were also the most cytotoxic on their own, so that in this regard the application of all dendrimers in anticancer therapy will be discussed.

Cationic carbosilane dendrimers and oligonucleotide binding: an energetic affair

Generation 2 cationic carbosilane dendrimers hold great promise as internalizing agents for gene therapy as they present low toxicity and retain and internalize the genetic material as an oligonucleotide or siRNA. In this work we carried out complete in silico structural and energetical characterization of the interactions of a set of G2 carbosilane dendrimers, showing different affinity towards two single strand oligonucleotide (ODN) sequences in vitro. Our simulations predict that these four dendrimers and the relevant ODN complexes are characterized by similar size and shape, and that the molecule-specific ODN binding ability can be rationalized only by considering a critical molecular design parameter: the normalized effective binding energy ΔG(bind,eff)/N(eff), i.e. the performance of each active individual dendrimer branch directly involved in a binding interaction.

Cyclotetrasiloxane frameworks for the chemoenzymatic synthesis of oligoesters

The lipase-mediated synthesis of branched and polycyclic polyester systems based on a cyclotetrasiloxane core.

siRNA nanotherapeutics: a Trojan horse approach against HIV

The concept of RNA interference (RNAi) is gaining popularity for the better management of various diseases, including HIV. Currently, the successful biomedical utilization of siRNA therapeutics is hampered, both in vivo and in vitro, mainly by the inherent inability of naked siRNA to cross the cell membrane. RNAi can potentially improve the weakness of current highly active antiretroviral therapy (HAART) by diminishing the chances of the appearance of antiHIV-resistant strains. Here, we discuss the nanocarrier-mediated delivery of siRNA delivery as well as highlighted the scope of siRNA-mediated gene-silencing technology for improved HIV treatment.

Interaction of cationic carbosilane dendrimers and their complexes with siRNA with erythrocytes and red blood cell ghosts

We have investigated the interactions between cationic NN16 and BDBR0011 carbosilane dendrimers with red blood cells or their cell membranes. The carbosilane dendrimers used possess 16 cationic functional groups. Both the dendrimers are made of water-stable carbon-silicon bonds, but NN16 possesses some oxygen-silicon bonds that are unstable in water. The nucleic acid used in the experiments was targeted against GAG-1 gene from the human immunodeficiency virus, HIV-1. By binding to the outer leaflet of the membrane, carbosilane dendrimers decreased the fluidity of the hydrophilic part of the membrane but increased the fluidity of the hydrophobic interior. They induced hemolysis, but did not change the morphology of the cells. Increasing concentrations of dendrimers induced erythrocyte aggregation. Binding of short interfering ribonucleic acid (siRNA) to a dendrimer molecule decreased the availability of cationic groups and diminished their cytotoxicity. siRNA-dendrimer complexes changed neither the fluidity of biological membranes nor caused cell hemolysis. Addition of dendriplexes to red blood cell suspension induced echinocyte formation.

Dendrimers as potential therapeutic tools in HIV inhibition

The present treatments for HIV transfection include chemical agents and gene therapies. Although many chemical drugs, peptides and genes have been developed for HIV inhibition, a variety of non-ignorable drawbacks limited the efficiency of these materials. In this review, we discuss the application of dendrimers as both therapeutic agents and non-viral vectors of chemical agents and genes for HIV treatment. On the one hand, dendrimers with functional end groups combine with the gp120 of HIV and CD4 molecule of host cell to suppress the attachment of HIV to the host cell. Some of the dendrimers are capable of intruding into the cell and interfere with the later stages of HIV replication as well. On the other hand, dendrimers are also able to transfer chemical drugs and genes into the host cells, which conspicuously increase the anti-HIV activity of these materials. Dendrimers as therapeutic tools provide a potential treatment for HIV infection.

A review of nanotechnological approaches for the prophylaxis of HIV/AIDS

Successful treatment and control of HIV/AIDS is one of the biggest challenges of 21st century. More than 33 million individuals are infected with HIV worldwide and more than 2 million new cases of HIV infection have been reported. The situation demands development of effective prevention strategies to control the pandemic of AIDS. Due to lack of availability of an effective HIV vaccine, antiretroviral drugs and nucleic acid therapeutics like siRNA have been explored for HIV prophylaxis. Clinical trials shave shown that antiretroviral drugs, tenofovir and emtricitabine can offer some degree of HIV prevention. However, complete prevention of HIV infection has not been achieved yet. Nanotechnology has brought a paradigm shift in the diagnosis, treatment and prevention of many diseases. The current review discusses potential of various nanocarriers such as dendrimers, polymeric nanoparticles, liposomes, lipid nanocarriers, drug nanocrystals, inorganic nanocarriers and nanofibers in improving efficacy of various modalities available for HIV prophylaxis.

Synthesis, structure and molecular modelling of anionic carbosilane dendrimers

Anionic carbosilane dendrimers of generations 1-3 have been synthesized containing carboxylate G(n)X(C(2)H(4)CO(2)Na)(m) and sulfonate G(n)X(C(2)H(4)SO(3)Na)(m) peripheral groups and derived from two different cores, 1,3,5-(HO)(3)C(6)H(3) (X = O(3)) and Si(C(3)H(5))(4) (X = Si). The peripheral anionic groups make these dendrimers water soluble, despite their highly hydrophobic framework. These dendrimers present a net negative charge in water, which was influenced by the pH of the medium. This characteristic was studied by pH titration. Also molecular modeling calculations have been performed to study differences in an aqueous medium between carboxylate and sulfonate dendrimers of different cores. The results obtained were also compared with those obtained from DOSY NMR experiments and zeta-potential measurements.

Stability of dendriplexes formed by anti-HIV genetic material and poly(propylene imine) dendrimers in the presence of glucosaminoglycans

There are several barriers to the application of dendriplexes formed by poly(propylene imine) dendrimers and genetic material for gene therapy. One limitation is their interaction with extracellular matrix components such as glucosaminoglycans. These can displace the genetic material from the dendriplexes, affecting their transfection activity. In this study, we analyzed the interaction between dendriplexes and the four main glucosaminoglycans (heparin, heparan sulfate, chondroitin sulfate, and hyaluronic acid) by fluorescence polarization and gel electrophoresis. Dendriplexes were formed by combining three anti-HIV antisense oligodeoxynucleotides with three poly(propylene imine) dendrimers of the fourth generation: unmodified and partially modified with maltose and maltotriose (open shell glycodendrimers). The data showed that the effect of glucosaminoglycans on dendriplexes depends on the glucosaminoglycan type and the oligosaccharide serving as the surface group of the dendrimer. Heparin at physiological concentrations destroys dendriplexes formed by open shell glycodendrimers, but dendriplexes based on unmodified poly(propylene imine) dendrimers are stable in its presence. The other glucosaminoglycans at physiological concentrations cannot destroy dendriplexes formed by any of the dendrimers studied.

Characterization of carboxylate-terminated carbosilane dendrimers and their evaluation as nanoadditives in capillary electrophoresis for vegetable protein profiling

Protein profiles are becoming an important tool to differentiate and classify varieties of several cultivars and to obtain a specific fingerprint for them. The use of protein profiles for these purposes needs to achieve high separation efficiencies to obtain a high number of well resolved peaks. In this work, carbosilane dendrimers with interior carbon-silicon bonds and negatively charged in the dendrimer surface with carboxylic acid as functional groups were employed as nanoadditives to separate soybean and olive seeds proteins. First, these dendrimers were characterized using CE to evaluate their possible impurities. A potentiometric titration was later carried out to determine their pK(a) values. Afterwards, the characterized dendrimers were used to improve the protein profiles obtained by EKC for vegetable proteins. Different dendrimer generations (G1, G2, and G3) and concentrations (0.01-1% m/v) were tested. The highest dendrimer generation G3 at 0.1% (m/v) allowed observing the best protein profiles for soybean and olive seeds. These results demonstrate that carboxylate-terminated carbosilane dendrimers are attractive nanoadditives in EKC for the effective separation of vegetable proteins.

The inhibition of Th17 immune response in vitro and in vivo by the carbosilane dendrimer 2G-NN16

We evaluated the 2G-NN16-carbosilane dendrimer activities in Th17 response as a potential therapy for Th17 deregulated pathologies. IL17A, IL17F, IL22, IL23 and other interleukins secreted by Th17 cells CD4+ cells were down regulated when cells were cultured in the presence of this dendrimer. Furthermore, IL17F and IL17A protein levels in splenocytes from mice pretreated with 2G-NN16 dendrimer in a Th17 induction mouse model were lower than those corresponding to PBS treated mice. Treatment of mice with 2G-NN16 inhibited the Th17 response causing much more pathogenicity as indicated by the increase in the number of Candida albicans colonies in the kidneys as compared to PBS-treated mice. All these results suggest a potential pharmacological application for this dendrimer in the therapy of Th17-mediated diseases.

Carbosilane dendrimers to transfect human astrocytes with small interfering RNA targeting human immunodeficiency virus

BACKGROUND

HIV infection of the CNS is the principle cause of HIV-associated dementia in adults and encephalopathy in children. Gene therapy techniques such as small interfering RNA (siRNA) possess great potential in drug development, but first they must overcome the key obstacle of reaching the interior of the affected cells. A successful delivery vector for anti-HIV drugs that is capable of crossing the blood-brain barrier (BBB) could provide a way of addressing this issue. Non-viral vectors such as dendrimers offer a means for effectively delivering and transfecting siRNA to the target cells.

OBJECTIVE

To evaluate the application of gene therapy for reducing HIV replication in human astrocytes.

METHODS

We used the 2G-NN16 amino-terminated carbosilane dendrimer as a method for delivering siRNA to HIV-infected human astrocytes. We tested the cytotoxicity in human astrocytoma cells caused by 2G-NN16 and dendriplexes formed with siRNA (siRNA/2G-NN16) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium-bromide (MTT) and lactate dehydrogenase assays. The ability to transfect human astrocytes with siRNA/2G-NN16 dendriplexes was tested by flow cytometry and immunofluorescence microscopy. To assess the potential capability of siRNA/2G-NN16 dendriplexes for crossing the BBB, we used an in vitro transcytosis assay with bovine brain microvascular endothelial cells. HIV-1 inhibition assays using 2G-NN16 and siRNA/2G-NN16 dendriplexes were determined by quantification of the viral load from culture supernatants of the astrocytes.

RESULTS

A gradual time-controlled degradation of the 2G-NN16 dendrimer and liberation of its siRNA cargo between 12 and 24 hours was observed via gel electrophoresis. There was no cytotoxicity in HIV-infected or non-infected human astrocytoma cells when treated with up to 24 microg/mL of 2G-NN16 dendrimer or siRNA/2G-NN16 dendriplexes, and siRNA/2G-NN16 dendriplexes were seen to successfully transfect human astrocytes even after crossing an in vitro BBB model. More interestingly, transfected siRNA was observed to exert a biologic effect, as dendriplexes were shown to down-regulate the housekeeping gene GAPDH and to reduce replication of HIV-1 strains X4-HIV NL4-3 and R5-HIV BaL in human astrocytes.

CONCLUSIONS

The 2G-NN16 dendrimer successfully delivers and transfects siRNA to HIV-infected human astrocytes and achieves gene silencing without causing cytotoxicity.

Characterization of complexes formed by polypropylene imine dendrimers and anti-HIV oligonucleotides

Current anti-HIV therapies are capable of controlling viral infection but do not represent a definitive cure. They rely on the administration of antiretroviral nucleoside analogues, either alone or in combination with vectors. Dendrimers are branched, synthetic polymers with layered architectures, promising non-viral vectors in gene therapy. The aim of the paper was to study the interactions between three anti-HIV antisense oligonucleotides (ODNs): SREV, ANTI TAR, GEM91 and different generation polypropylene imine dendrimers (PPI) by monitoring changes in the fluorescence polarization of fluorescein attached to the ends of the ODNs when increasing concentrations of dendrimers were added. Laser Doppler electrophoresis, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize, respectively, zeta potential, particle size and morphology of dendriplexes formed in different molar ratios. Antisense oligonucleotides interacted with polypropylene imine dendrimers in different molar ratios depending on generation. Zeta potential of dendriplexes varied from (-25 to -21) mV to -5 mV (for PPIG3 and PPIG4 complexes) and to zero (for PPIG2 complexes). The structures presented a polydisperse size from about 50 nm to even 700-800 nm by TEM and about 250 nm by DLS. It means that besides single dendriplexes, aggregates were also present.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.

Gene therapy in HIV-infected cells to decrease viral impact by using an alternative delivery method

The ability of dendrimer 2G-[Si{O(CH(2))(2)N(Me)(2) (+)(CH(2))(2)NMe(3) (+)(I(-))(2)}](8) (NN16) to transfect a wide range of cell types, as well as the possible biomedical application in direct or indirect inhibition of HIV replication, was investigated. Cells implicated in HIV infection such as primary peripheral blood mononuclear cells (PBMC) and immortalized suspension cells (lymphocytes), primary macrophages and dendritic cells, and immortalized adherent cells (astrocytes and trophoblasts) were analyzed. Dendrimer toxicity was evaluated by mitochondrial activity, cell membrane rupture, release of lactate dehydrogenase, erythrocyte hemolysis, and the effect on global gene expression profiles using whole-genome human microarrays. Cellular uptake of genetic material was determined using flow cytometry and confocal microscopy. Transfection efficiency and gene knockdown was investigated using dendrimer-delivered antisense oligonucleotides and small interfering RNA (siRNA). Very little cytotoxicity was detected in a variety of cells relevant to HIV infection and erythrocytes after NN16 dendrimer treatment. Imaging of cellular uptake showed high transfection efficiency of genetic material in all cells tested. Interestingly, NN16 further enhanced the reduction of HIV protein 24 antigen release by antisense oligonucleotides due to improved transfection efficiency. Finally, the dendrimer complexed with siRNA exhibited therapeutic potential by specifically inhibiting cyclooxygenase-2 gene expression in HIV-infected nervous system cells. NN16 dendrimers demonstrated the ability to transfect genetic material into a vast array of cells relevant to HIV pathology, combining high efficacy with low toxicity. These results suggest that NN16 dendrimers have the potential to be used as a versatile non-viral vector for gene therapy against HIV infection.

The mechanism of polyplex internalization into cells: testing the GM1/caveolin-1 lipid raft mediated endocytosis pathway

The GM1/caveolin-1 lipid raft mediated endocytosis mechanism was explored for generation 5 and 7 poly(amidoamine) dendrimer polyplexes employing the Cos-7, 293A, C6, HeLa, KB, and HepG2 cell lines. Expression levels of GM1 and caveolin-1 were measured using dot blot and Western blot, respectively. The level of GM1 in the cell plasma membrane was adjusted by incubation with exogenous GM1 or ganglioside inhibitor PPMP, and the level of CAV-1 was adjusted by upregulation with the adenovirus vector expressed caveolin-1 (AdCav-1). Cholera toxin B subunit was employed as a positive control for uptake in all cases. No evidence was found for a GM1/caveolin-1 lipid raft mediated endocytosis mechanism for the generation 5 and 7 poly(amidoamine) dendrimer polyplexes.

How to study dendriplexes II: Transfection and cytotoxicity

This paper reviews different techniques for analyzing the transfection efficiencies and cytotoxicities of dendriplexes-complexes of nucleic acids with dendrimers. Analysis shows that three plasmids are mainly used in transfection experiments: plasmid DNA encoding luciferase from the firefly Photinus pyralis, beta-galactosidase, or green fluorescent protein. The effective charge ratio of transfection does not directly correlate with the charge ratio obtained from gel electrophoresis, zeta-potential or ethidium bromide intercalation data. The most popular cells for transfection studies are human embryonic kidney cells (HEK293), mouse embryonic cells (NIH/3T3), SV40 transformed monkey kidney fibroblasts (COS-7) and human epithelioid cervical carcinoma cells (HeLa). Cellular uptake is estimated using fluorescently-labeled dendrimers or nucleic acids. Transfection efficiency is measured by the luciferase reporter assay for luciferase, X-Gal staining or beta-galactosidase assay for beta-galactosidase, and confocal microscopy for green fluorescent protein. Cytotoxicity is determined by the MTT test and lactate dehydrogenase assays. On the basis of the papers reviewed, a standard essential set of techniques for characterizing dendriplexes was constructed: (1) analysis of size and shape of dendriplexes in dried/frozen state by electron or atomic force microscopy; (2) analysis of charge/molar ratio of complexes by gel electrophoresis or ethidium bromide intercalation assay or zeta-potential measurement; (3) analysis of hydrodynamic diameter of dendriplexes in solution by dynamic light scattering. For the evaluation of transfection efficiency the essential techniques are (4) luciferase reporter assay, beta-galactosidase assay or green fluorescent protein microscopy, and (5) cytotoxicity by the MTT test. All these tests allow the transfection efficiencies and cytotoxicities of different kinds of dendrimers to be compared.

Water-stable ammonium-terminated carbosilane dendrimers as efficient antibacterial agents

A new family of amine- and ammonium-terminated carbosilane dendrimers of the type Gn-[Si(CH2)3N(Et)CH2CH2NMe2]x and Gn-{[Si(CH2)(3)N+R(Et)CH2CH2N+RMe2]x(X-)y} (where n = 1, 2 and 3; R = H, X = Cl; R = Me, X = I) respectively has been synthesized by hydrosilylation of N,N-dimethyl-N'-allyl-N'-ethyl-ethylenediamine, [(CH2=CH-CH2)(Et)N(CH2)2NMe2] with the corresponding hydride-terminated dendrimers and subsequent quaternization with HCl or MeI. Quaternized dendrimers are soluble and stable in water or other protic solvents for long time periods. The antibacterial properties of the quaternary ammonium functionalized dendrimers have been evaluated showing that they act as potent biocides in which the multivalency along with the biopermeability of the carbosilane dendritic skeleton play an important role in the antibactericidal activity of these compounds.

Highly efficient transfection of rat cortical neurons using carbosilane dendrimers unveils a neuroprotective role for HIF-1alpha in early chemical hypoxia-mediated neurotoxicity

PURPOSE

To study the effect of a non-viral vector (carbosilane dendrimer) to efficiently deliver small interfering RNA to postmitotic neurons to study the function of hypoxia-inducible factor-1alpha (HIF1-alpha) during chemical hypoxia-mediated neurotoxicity.

METHODS

Chemical hypoxia was induced in primary rat cortical neurons by exposure to CoCl(2). HIF1-alpha levels were determined by Western Blot and toxicity was evaluated by both MTT and LDH assays. Neurons were incubated with dendriplexes containing anti-HIF1-alpha siRNA and both uptake and HIF1-alpha knockdown efficiency were evaluated.

RESULTS

We report that a non-viral vector (carbosilane dendrimer) can deliver specific siRNA to neurons and selectively block HIF1-alpha synthesis with similar efficiency to that achieved by viral vectors. Using this method, we have found that this transcription factor plays a neuroprotective role during the early phase of chemical hypoxia-mediated neurotoxicity.

CONCLUSION

This work represents a proof-of-concept for the use of carbosilane dendrimers to deliver specific siRNA to postmitotic neurons to block selected protein synthesis. This indicates that this type of vector is a good alternative to viral vectors to achieve very high transfection levels in neurons. This also suggests that carbosilane dendrimers might be very useful for gene therapy.

Changes in gene expression pattern of human primary macrophages induced by carbosilane dendrimer 2G-NN16

PURPOSE

The use of dendrimers for biomedical applications has emerged with promising results. 2G-NN16 is a carbosilane dendrimer with sixteen positive charges per molecule tested to be capable to bind and release antisense oligonucleotides (ODNs) and small interference RNA (siRNA) in vitro. In spite of low cytotoxicity observed for these dendrimers, little is known about cellular changes they produce in cells in general and in immune cells in particular.

MATERIALS AND METHODS

Genomic technologies allow us to identify global gene expression profile changes in macrophages exposed to a non-toxic concentration (5 microM) of 2G-NN16, alone or complexed with a random siRNA (dendriplex). Results were confirmed by quantitative real-time RT-PCR.

RESULTS

Exposing macrophages to this dendrimer or dendriplex causes multiple gene expression changes, but no specific action of random siRNA was detected. Pathway analysis of differentially expressed genes shows the altered functions to be immune response, proliferation and transcription regulation. Interleukin 17F (IL17F) was the most regulated gene.

CONCLUSIONS

Global gene expression profiles are a highly sensitive method to measure the toxicity degree of a gene delivery vehicle. The strong repression of IL17F, IL23R and IL23A, all of which are involved in autoimmune disease, by this particular dendrimer suggests a potential pharmacological application.

Characterization of carbosilane dendrimers as effective carriers of siRNA to HIV-infected lymphocytes

One of the primary limitations of RNA interference as a technique for gene regulation is effective delivery of siRNA into the target cells. Dendrimers are nanoparticles that are increasingly being used as oligonucleotide and drug delivery vehicles. We have developed amino-terminated carbosilane dendrimers (CBS) as a means to protect and transport siRNA. Initially, stability studies showed that CBS bind siRNA via electrostatic interactions. Dendrimer-bound siRNA was found to be resistant to degradation by RNase. Cytotoxicity assays of CBS/siRNA dendriplexes with peripheral blood mononuclear cells (PBMC) and the lymphocytic cell line SupT1 revealed a maximum safe dendrimer concentration of 25 microg/ml. Next, utilizing flow cytometry and confocal microscopy, lymphocytes were seen to be successfully transfected by fluorochrome-labeled siRNA either naked or complexed with CBS. Dendriplexes with +/- charge ratio of 2 were determined to have the highest transfection efficiency while maintaining a low level of toxicity in these systems including hard-to-transfect HIV-infected PBMC. Finally, CBS/siRNA dendriplexes were shown to silence GAPDH expression and reduce HIV replication in SupT1 and PBMC. These results point to the possibility of utilizing dendrimers such as CBS to deliver and transfect siRNA into lymphocytes thus allowing the use of RNA interference as a potential alternative therapy for HIV infection.