Carbosilane dendrimers as gene delivery agents for the treatment of HIV infection

Ruthenium metallodendrimer against triple-negative breast cancer in mice

Carbosilane metallodendrimers, based on the arene Ru(II) complex (CRD13) and integrated to imino-pyridine surface groups have been investigated as an anticancer agent in a mouse model with triple-negative breast cancer. The dendrimer entered into the cells efficiently, and exhibited selective toxicity for 4T1 cells. In vivo investigations proved that a local injection of CRD13 caused a reduction of tumour mass and was non-toxic. ICP analyses indicated that Ru(II) accumulated in all tested tissues with a greater content detected in the tumour.

Encapsulation of miRNA and siRNA into Nanomaterials for Cancer Therapeutics

Globally, cancer is amongst the most deadly diseases due to the low efficiency of the conventional and obsolete chemotherapeutic methodologies and their many downsides. The poor aqueous solubility of most anticancer medications and their low biocompatibility make them ineligible candidates for the design of delivery systems. A significant drawback associated with chemotherapy is that there are no advanced solutions to multidrug resistance, which poses a major obstacle in cancer management. Since RNA interference (RNAi) can repress the expression of genes, it is viewed as a novel tool for advanced drug delivery. this is being explored as a promising drug targeting strategy for the treatment of multiple diseases, including cancer. However, there are many obstructions that hinder the clinical uses of siRNA drugs due to their low permeation into cells, off-target impacts, and possible unwanted immune responses under physiological circumstances. Thus, in this article, we review the design measures for siRNA conveyance frameworks and potential siRNA and miRNA drug delivery systems for malignant growth treatment, including the use of liposomes, dendrimers, and micelle-based nanovectors and functional polymer-drug delivery systems. This article sums up the advancements and challenges in the use of nanocarriers for siRNA delivery and remarkably centers around the most critical modification strategies for nanocarriers to build multifunctional siRNA and miRNA delivery vectors. In short, we hope this review will throw light on the dark areas of RNA interference, which will further open novel research arenas in the development of RNAi drugs for cancer.

Nanomedicine-based delivery strategies for nucleic acid gene inhibitors in inflammatory diseases

Thanks to their abilities to modulate the expression of virtually any genes, RNA therapeutics have attracted considerable research efforts. Among the strategies focusing on nucleic acid gene inhibitors, antisense oligonucleotides and small interfering RNAs have reached advanced clinical trial phases with several of them having recently been marketed. These successes were obtained by overcoming stability and cellular delivery issues using either chemically modified nucleic acids or nanoparticles. As nucleic acid gene inhibitors are promising strategies to treat inflammatory diseases, this review focuses on the barriers, from manufacturing issues to cellular/subcellular delivery, that still need to be overcome to deliver the nucleic acids to sites of inflammation other than the liver. Furthermore, key examples of applications in rheumatoid arthritis, inflammatory bowel, and lung diseases are presented as case studies of systemic, oral, and lung nucleic acid delivery.

Small Interfering RNAs and their Delivery Systems: A Novel Powerful Tool for the Potential Treatment of HIV Infections

Small interfering RNAs (siRNAs) have rapidly developed into biomedical research as a novel tool for the potential treatment of various human diseases. They are based on altered gene expression. In spite of the availability of highly active antiretroviral therapy (HAART), there is a specific interest in developing siRNAs as a therapeutic agent for human immunodeficiency virus (HIV) due to several problems including toxicity and drug resistance along with long term treatment. The successful use of siRNAs for therapeutic goals needs safe and effective delivery to specific cells and tissues. Indeed, the efficiency of gene silencing depends on the potency of the carrier used for siRNA delivery. The combination of siRNA and nano-carriers is a potent method to prevent the limitations of siRNA formulation. Three steps were involved in non-viral siRNA carriers such as the complex formation of siRNA with a cationic carrier, conjugation of siRNA with small molecules, and encapsulation of siRNA within nanoparticles. In this mini-review, the designed siRNAs and their carriers are described against HIV-1 infections both in vitro and in vivo.

Developments in Treatment Methodologies Using Dendrimers for Infectious Diseases

Dendrimers comprise a specific group of macromolecules, which combine structural properties of both single molecules and long expanded polymers. The three-dimensional form of dendrimers and the extensive possibilities for use of additional substrates for their construction creates a multivalent potential and a wide possibility for medical, diagnostic and environmental purposes. Depending on their composition and structure, dendrimers have been of interest in many fields of science, ranging from chemistry, biotechnology to biochemical applications. These compounds have found wide application from the production of catalysts for their use as antibacterial, antifungal and antiviral agents. Of particular interest are peptide dendrimers as a medium for transport of therapeutic substances: synthetic vaccines against parasites, bacteria and viruses, contrast agents used in MRI, antibodies and genetic material. This review focuses on the description of the current classes of dendrimers, the methodology for their synthesis and briefly drawbacks of their properties and their use as potential therapies against infectious diseases.

Promising PEGylated cationic dendrimers for delivery of miRNAs as a possible therapy against HIV-1 infection

BACKGROUND

The appearance of resistance against new treatments and the fact that HIV-1 can infect various cell types and develop reservoirs and sanctuaries makes it necessary to develop new therapeutic approaches to overcome those failures.

RESULTS

Studies of cytotoxicity, genotoxicity, complexes formation, stability, resistance, release and particle size distribution confirmed that G2-SN15-PEG, G3-SN31-PEG, G2-SN15-PEG-FITC and G3-SN31-PEG-FITC dendrimers can form complexes with miRNAs being biocompatible, stable and conferring protection to these nucleic acids. Confocal microscopy and flow cytometry showed effective delivery of these four dendrimers into the target cells, confirming their applicability as delivery systems. Dendriplexes formed with the dendrimers and miRNAs significantly inhibited HIV-1 infection in PBMCs.

CONCLUSIONS

These dendrimers are efficient delivery systems for miRNAs and they specifically and significantly improved the anti-R5-HIV-1 activity of these RNA molecules.

siRNAs and viruses: The good, the bad and the way forward

There are no available antivirals for many viruses or strains, while current antivirals are limited by toxicity and drug resistance. Therefore, alternative strategies, such as RNA interference (RNAi) are required. RNAi suppresses gene expression of any mRNA, making it an attractive candidate for antiviral therapeutics. Studies have evaluated siRNAs in a range of viruses, with some showing promising results. However, issues with stability and delivery of siRNAs remain. These may be minimized by modifying the siRNA structure, using an efficient delivery vector and targeting multiple regions of a virus's genome in a single dose. Finding these solutions could accelerate the progress of RNAi-based antivirals. This review highlights selected examples of antiviral siRNAs, limitations of RNAi and strategies to overcome these limitations.

Cyclopentadienyl ruthenium(II) carbosilane metallodendrimers as a promising treatment against advanced prostate cancer

In searching for efficient and selective antitumour drugs, a new family of carbosilane metallodendrimers functionalized with [Ru(η⁵-C₅H₅)(PTA)Cl] (PTA = 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1] decane) is reported. Experiments of the biophysical characterization showed an ability to interact with biological membranes, as well as with proteins (e.g. human serum albumin) without affecting their usual biological activity. These metallodendrimers possessed potent and selective anticancer activity in vitro in a panel of tumour cell lines. Importantly, the first generation metallodendrimer, bearing 4 Ru(II) complexes, was remarkably active towards resistant prostate cancer cells, inhibiting both cell proliferation and metastasis to bone tissues. Such promising antitumour activity can be further improved when given with docetaxel, with in vitro cytotoxicity being in the nanomolar range. Furthermore, its intravenous administration to an advanced prostate cancer mice model inhibited tumour growth up to 25% and 45% when given 10 mg/kg/week and 7.5 mg/kg/4-5 days, respectively.

Nanomedicines for the delivery of glucocorticoids and nucleic acids as potential alternatives in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects 0.5-1% of the world population. Current treatments include on one hand non-steroidal anti-inflammatory drugs and glucocorticoids (GCs) for treating pain and on the other hand disease-modifying anti-rheumatic drugs such as methotrexate, Janus kinase inhibitors or biologics such as antibodies targeting mainly cytokine expression. More recently, nucleic acids such as siRNA, miRNA, or anti-miRNA have shown strong potentialities for the treatment of RA. This review discusses the way nanomedicines can target GCs and nucleic acids to inflammatory sites, increase drug penetration within inflammatory cells, achieve better subcellular distribution and finally protect drugs against degradation. For GCs such a targeting effect would allow the treatment to be more effective at lower doses and to reduce the administration frequency as well as to induce much fewer side-effects. In the case of nucleic acids, particularly siRNA, knocking down proteins involved in RA, could importantly be facilitated using nanomedicines. Finally, the combination of both siRNA and GCs in the same carrier allowed for the same cell to target both the GCs receptor as well as any other signaling pathway involved in RA. Nanomedicines appear to be very promising for the delivery of conventional and novel drugs in RA therapeutics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures.

Dendrimers as Pharmaceutical Excipients: Synthesis, Properties, Toxicity and Biomedical Applications

The European Medicines Agency (EMA) and the Current Good Manufacturing Practices (cGMP) in the United States of America, define excipient as the constituents of the pharmaceutical form other than the active ingredient, i.e., any component that is intended to furnish pharmacological activity. Although dendrimers do not have a pharmacopoeia monograph and, therefore, cannot be recognized as a pharmaceutical excipient, these nanostructures have received enormous attention from researchers. Due to their unique properties, like the nanoscale uniform size, a high degree of branching, polyvalency, aqueous solubility, internal cavities, and biocompatibility, dendrimers are ideal as active excipients, enhancing the solubility of poorly water-soluble drugs. The fact that the dendrimer's properties are controllable during their synthesis render them promising agents for drug-delivery applications in several pharmaceutical formulations. Additionally, dendrimers can be used for reducing the drug toxicity and for the enhancement of the drug efficacy. This review aims to discuss the properties that turn dendrimers into pharmaceutical excipients and their potential applications in the pharmaceutical and biomedical fields.

Generation 2 (G2) - Generation 4 (G4) PAMAM dendrimers disrupt key plasma coagulation parameters

The aim of the research was to evaluate the effects of G2 - G4 PAMAM dendrimers on basic plasma haemostasis parameters (Partially Activated Thrombin Time (APTT), Prothrombin Time (PT), Thrombin Time (TT)) as well as the activity of factor X, antithrombin III (AT), protein C and plasmin. Furthermore, tissue factor (TF) synthesis in endothelial cells and viability of smooth muscle cells in the presence of PAMAM dendrimers was investigated. APTT, PT and TT were performed according to the available commercial methods. The activity of factor X was conducted based on deficient plasma factor X. Protein C, AT and plasmin activity were measured spectrophotometrically using chromogenic substrates. Intracellular TF production in human umbilical vein endothelial cells (HUVECs) was measured using immunohistochemical method. Viability of Human Aortal Smooth Muscle cells (hAoSMCs) was established using WST-1 assay. PAMAM dendrimers decreased activity of factor X, and concomitantly prolonged PT and APTT. We also demonstrated shortened TT and increased fibrinogen concentrations in plasma treated with G4 PAMAM dendrimers, suggesting formation of fibrinogen aggregates. G2 - G4 PAMAM dendrimers decreased the activity of both naturally occurring anticoagulants AT and protein C. G2 and G3 PAMAM dendrimers did not affect the proteolytic reaction with plasmin. PAMAM dendrimers were found not to trigger TF production in undisturbed endothelial cells. PAMAM dendrimers, depending on the concentration and generation decreased viability of AoSMCs. The results presented within the current study suggest complex but mostly undesirable effect of G2 - G4 PAMAM dendrimers on plasma haemostasis and underscore the need for further in-depth research.

Nanoparticle Vaccines Against Infectious Diseases

Due to emergence of new variants of pathogenic micro-organisms the treatment and immunization of infectious diseases have become a great challenge in the past few years. In the context of vaccine development remarkable efforts have been made to develop new vaccines and also to improve the efficacy of existing vaccines against specific diseases. To date, some vaccines are developed from protein subunits or killed pathogens, whilst several vaccines are based on live-attenuated organisms, which carry the risk of regaining their pathogenicity under certain immunocompromised conditions. To avoid this, the development of risk-free effective vaccines in conjunction with adequate delivery systems are considered as an imperative need to obtain desired humoral and cell-mediated immunity against infectious diseases. In the last several years, the use of nanoparticle-based vaccines has received a great attention to improve vaccine efficacy, immunization strategies, and targeted delivery to achieve desired immune responses at the cellular level. To improve vaccine efficacy, these nanocarriers should protect the antigens from premature proteolytic degradation, facilitate antigen uptake and processing by antigen presenting cells, control release, and should be safe for human use. Nanocarriers composed of lipids, proteins, metals or polymers have already been used to attain some of these attributes. In this context, several physico-chemical properties of nanoparticles play an important role in the determination of vaccine efficacy. This review article focuses on the applications of nanocarrier-based vaccine formulations and the strategies used for the functionalization of nanoparticles to accomplish efficient delivery of vaccines in order to induce desired host immunity against infectious diseases.

Dendrimers Show Promise for siRNA and microRNA Therapeutics

The lack of an appropriate intracellular delivery system for therapeutic nucleic acids (TNAs) is a major problem in molecular biology, biotechnology, and medicine. A relatively new class of highly symmetrical hyperbranched polymers, called dendrimers, shows promise for transporting small TNAs into both cells and target tissues. Dendrimers have intrinsic advantages for this purpose: their physico-chemical and biological properties can be controlled during synthesis, and they are able to transport large numbers of TNA molecules that can specifically suppress the expression of single or multiple targeted genes. Numerous chemical modifications of dendrimers extend the biocompatibility of synthetic materials and allow targeted vectors to be designed for particular therapeutic purposes. This review summarizes the latest experimental data and trends in the medical application of various types of dendrimers and dendrimer-based nanoconstructions as delivery systems for short small interfering RNAs (siRNAs) and microRNAs at the cell and organism levels. It provides an overview of the structural features of dendrimers, indicating their advantages over other types of TNA transporters.

Nanotechnology approaches to eradicating HIV reservoirs

The advent of combination antiretroviral therapy (cART) has transformed HIV-1 infection into a controllable chronic disease, but these therapies are incapable of eradicating the virus to bring about an HIV cure. Multiple strategies have been proposed and investigated to eradicate latent viral reservoirs from various biological sanctuaries. However, due to the complexity of HIV infection and latency maintenance, a single drug is unlikely to eliminate all HIV reservoirs and novel strategies may be needed to achieve better efficacy while limiting systemic toxicity. In this review, we describe HIV latency in cellular and anatomical reservoirs, and present an overview of current strategies for HIV cure with a focus on their challenges for clinical translation. Then we provide a summary of nanotechnology solutions that have been used to address challenges in HIV cure by delivering physicochemically diverse agents for combination therapy or targeting HIV reservoir sites. We also review nanocarrier-based gene delivery and immunotherapy used in cancer treatment but may have potential applications in HIV cure.

Polymeric therapeutic delivery systems for the treatment of infectious diseases

Infectious diseases caused by germs, parasites, fungi, virus and bacteria are one of the leading causes of death worldwide. Polymeric therapeutics are nanomedicines that offer several advantages making them useful for the treatment of infectious diseases such as targeted drug release mechanism, ability to maintain the drug concentration within a therapeutic window for a desired duration, biocompatibility with low immunogenicity and reduced drug toxicity resulting in enhanced therapeutic efficacy of the incorporated drug. Although polymeric therapeutics have been evaluated for the treatment of infectious diseases in vitro and in vivo with improved therapeutic efficacy, most treatments for infectious disease have not been evaluated using polymeric therapeutics. This review will focus on the applications of polymeric therapeutics for the treatment of infectious diseases (preclinical studies and clinical trials), with particular focus on parasitic and viral infections.

Increased CD127+ and decreased CD57+ T cell expression levels in HIV-infected patients on NRTI-sparing regimens

BACKGROUND

NRTIs-sparing regimens exert favourable profiles on T-cell homeostasis associated parameters. Our aim was to analyze the effect of NRTIs sparing regimen (NRTI-sparing-cART) vs NRTIs-containing regimen (NRTI-cART), on T-cell homeostasis associated parameters in naive HIV-infected patients.

METHODS

Biomarkers of cell survival (CD127) and replicative senescence (CD57), were measured by multiparametric flow cytometry for T-cell phenotyping on peripheral blood mononuclear cells (PBMCs) samples just before (baseline) and after 48 weeks of undetectable viral load in patients on NRTI-sparing-cART (N = 13) and NRTI-cART (N = 14). After 48 weeks a subgroup of patients (n = 5) on NRTI-cART switched to NRTI-sparing-cART for another additional 48 weeks. In vitro assays were performed on PBMCs from HIV-uninfected healthy donors exposed or not to HIV. To analyze the independent factors associated with type of cART bivariate and stepwise multivariate analysis were performed after adjusting for basal CD4+, CD8+ and nadir CD4+ T-cell counts.

RESULTS

After 48 weeks of a NRTI-sparing-cART vs NRTI-cART patients have higher effector memory (EM) CD4+ CD127+ T-cell levels, lower EM CD4+ CD57+ T-cell levels, higher CD8+ CD127+ T-cell levels, lower CD8+ CD57+ T-cell levels and higher memory CD8+ T-cell levels. This effect was confirmed in the subgroup of patients who switched to NRTI-sparing-cART. In vitro assays confirmed that the deleterious effect of a NRTIs-containing regimen was due to NRTIs.

CONCLUSIONS

The implementation of NRTI-sparing regimens, with a favourable profile in CD127 and CD57 T-cell expression, could benefit cART-patients. These results could have potential implications in a decrease in the number of Non-AIDS events.

Current Progress in Non-viral RNAi-Based Delivery Strategies to Lymphocytes

RNAi-based therapy holds great promise, as it can be utilized for the treatment of multiple conditions in an accurate manner via sequence-specific manipulation of gene expression. To date, RNAi therapeutics have advanced into clinical trials for liver diseases and solid tumors; however, delivery of RNAi to leukocytes in general and to lymphocytes in particular remains a challenge. Lymphocytes are notoriously hard to transduce with RNAi payloads and are disseminated throughout the body, often located in deep tissues; therefore, developing an efficient systemic delivery system directed to lymphocytes is not a trivial task. Successful manipulation of lymphocyte function with RNAi possesses immense therapeutic potential, as it will enable researchers to resolve lymphocyte-implicated diseases such as inflammation, autoimmunity, transplant rejection, viral infections, and blood cancers. This potential has propelled the development of novel targeted delivery systems relying on the accumulating research knowledge from multiple disciplines, including materials science and engineering, immunology, and genetics. Here, we will discuss the recent progress in non-viral delivery strategies of RNAi payloads to lymphocytes. Special emphasis will be made on the challenges and potential opportunities in manipulating lymphocyte function with RNAi. These approaches might ultimately become a novel therapeutic modality to treat leukocyte-related diseases.

Potential inhibition of HIV-1 encapsidation by oligoribonucleotide-dendrimer nanoparticle complexes

Background

Encapsidation, the process during which the genomic RNA of HIV is packaged into viral particles, is an attractive target for antiviral therapy. This study explores a novel nanotechnology-based strategy to inhibit HIV encapsidation by an RNA decoy mechanism. The design of the 16-mer oligoribonucleotide (RNA) decoy is based on the sequence of stem loop 3 (SL3) of the HIV packaging signal (Ψ). Recognition of the packaging signal is essential to the encapsidation process. It is theorized that the decoy RNA, by mimicking the packaging signal, will disrupt HIV packaging if efficiently delivered into lymphocytes by complexation with a carbosilane dendrimer. The aim of the study is to measure the uptake, toxicity, and antiviral activity of the dendrimer–RNA nanocomplex.

Materials and methods

A dendriplex was formed between cationic carbosilane dendrimers and the RNA decoy. Uptake of the fluorescein-labeled RNA into MT4 lymphocytes was determined by flow cytometry and confocal microscopy. The cytoprotective effect (50% effective concentration [EC₅₀]) and the effect on HIV replication were determined in vitro by the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and viral load measurements, respectively.

Results

Flow cytometry and confocal imaging demonstrated efficient transfection of lymphocytes. The dendriplex containing the Ψ decoy showed some activity (EC₅₀ =3.20 µM, selectivity index =8.4). However, there was no significant suppression of HIV viral load.

Conclusion

Oligoribonucleotide decoys containing SL3 of the packaging sequence are efficiently delivered into lymphocytes by carbosilane dendrimers where they exhibit a modest cytoprotective effect against HIV infection.

Polyanionic carbosilane dendrimers prevent hepatitis C virus infection in cell culture

Hepatitis C virus (HCV) infection is a major biomedical problem worldwide. Although new direct antiviral agents (DAAs) have been developed for the treatment of chronic HCV infection, the potential emergence of resistant virus variants and the difficulties to implement their administration worldwide make the development of novel antiviral agents an urgent need. Moreover, no effective vaccine is available against HCV and transmission of the virus still occurs particularly when prophylactic measures are not taken. We used a cell-based system to screen a battery of polyanionic carbosilane dendrimers (PCDs) to identify compounds with antiviral activity against HCV and show that they inhibit effective virus adsorption of major HCV genotypes. Interestingly, one of the PCDs irreversibly destabilized infectious virions. This compound displays additive effect in combination with a clinically relevant DAA, sofosbuvir. Our results support further characterization of these molecules as nanotools for the control of hepatitis C virus spread.

Recent advances in RNAi-based strategies for therapy and prevention of HIV-1/AIDS

RNA interference (RNAi) provides a powerful tool to silence specific gene expression and has been widely used to suppress host factors such as CCR5 and/or viral genes involved in HIV-1 replication. Newer nuclease-based gene-editing technologies, such as zinc finger nucleases (ZFN), transcription activator-like effector nucleases (TALEN) and the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, also provide powerful tools to ablate specific genes. Because of differences in co-receptor usage and the high mutability of the HIV-1 genome, a combination of host factors and viral genes needs to be suppressed for effective prevention and treatment of HIV-1 infection. Whereas the continued presence of small interfering/short hairpin RNA (si/shRNA) mediators is needed for RNAi to be effective, the continued expression of nucleases in the gene-editing systems is undesirable. Thus, RNAi provides the only practical way for expression of multiple silencers in infected and uninfected cells, which is needed for effective prevention/treatment of infection. There have been several advances in the RNAi field in terms of si/shRNA design, targeted delivery to HIV-1 susceptible cells, and testing for efficacy in preclinical humanized mouse models. Here, we comprehensively review the latest advances in RNAi technology towards prevention and treatment of HIV-1.

Inorganic dendrimers: recent advances for catalysis, nanomaterials, and nanomedicine

Dendrimers are hyperbranched polymers having a perfectly defined structure because they are synthesized step-by-step in an iterative fashion, and not by polymerization reactions. Some dendrimers are considered as inorganic, as they possess inorganic atoms at each branching point. Among numerous examples, two families of inorganic dendrimers have emerged as particularly promising: silicon-containing dendrimers, particularly carbosilanes, and phosphorus-containing dendrimers, particularly phosphorhydrazones. This tutorial review will display the main properties of both families of dendrimers in the fields of catalysis, materials and biology/nanomedicine. Emphasis will be put on the most recent and promising examples.

Polyphenolic carbosilane dendrimers as anticancer agents against prostate cancer

Polyphenolic carbosilane dendrimers improved the antioxidant and anticancer properties of free vanillin.

Nanotechnology Approaches for the Delivery of Exogenous siRNA for HIV Therapy

RNA interference (RNAi) is triggered by oligonucleotides that are about 21-23 nucleotides long and are capable of inducing the destruction of complementary mRNA. The RNAi technique has been successfully utilized to target HIV replication; however, the main limitation to the successful utilization of this technique in vivo is the inability of naked siRNA to cross the cell membrane by diffusion due to its strong anionic charge and large molecular weight. This review describes current nonviral nanotechnological approaches to deliver anti-HIV siRNAs for the treatment of HIV infection.

Synthesis, characterization and antibacterial behavior of water-soluble carbosilane dendrons containing ferrocene at the focal point

A series of novel water-soluble ammonium-terminated carbosilane dendrons containing a ferrocene unit at the focal point were synthesized, in order to combine the unique redox activity of ferrocene and the precisely designed structure of the dendrons with the aim to evaluate them as a new class of potential organometallic-based antibacterial compounds. The synthetic route is based on the initial amination of ferrocenecarboxaldehyde with carbosilane dendrons that contain allyl groups on the surface followed by reduction of the in situ prepared imine product, and the subsequent functionalization of the periphery with terminal amine groups by hydrosilylation reactions. Systems quaternized with HCl are soluble and stable in water or other protic solvents. The obtained compounds were spectrally and electrochemically (cyclic voltammetry) characterized, and diffusion-ordered spectroscopy experiments were conducted to determine the size of the dendritic wedges in solution. The antibacterial activity of these compounds was evaluated using Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli), which shows that the first and second generations of cationic dendrons are broad spectrum antibacterial agents, i.e. selective and effective in both bacterial strains.

Mesoporous Silica Nanoparticles Decorated with Carbosilane Dendrons as New Non-viral Oligonucleotide Delivery Carriers

A novel nanosystem based on mesoporous silica nanoparticles covered with carbosilane dendrons grafted on the external surface of the nanoparticles is reported. This system is able to transport single-stranded oligonucleotide into cells, avoiding an electrostatic repulsion between the cell membrane and the negatively charged nucleic acids thanks to the cationic charge provided by the dendron coating under physiological conditions. Moreover, the presence of the highly ordered pore network inside the silica matrix would make possible to allocate other therapeutic agents within the mesopores with the aim of achieving a double delivery. First, carbosilane dendrons of second and third generation possessing ammonium or tertiary amine groups as peripheral functional groups were prepared. Hence, different strategies were tested in order to obtain their suitable grafting on the outer surface of the nanoparticles. As nucleic acid model, a single-stranded DNA oligonucleotide tagged with a fluorescent Cy3 moiety was used to evaluate the DNA adsorption capacity. The hybrid material functionalised with the third generation of a neutral dendron showed excellent DNA binding properties. Finally, the cytotoxicity as well as the capability to deliver DNA into cells, was tested in vitro by using a human osteoblast-like cell line, achieving good levels of internalisation of the vector DNA/carbosilane dendron-functionalised material without affecting the cellular viability.

Systemic Gene Silencing in Primary T Lymphocytes Using Targeted Lipid Nanoparticles

Modulating T cell function by down-regulating specific genes using RNA interference (RNAi) holds tremendous potential in advancing targeted therapies in many immune-related disorders including cancer, inflammation, autoimmunity, and viral infections. Hematopoietic cells, in general, and primary T lymphocytes, in particular, are notoriously hard to transfect with small interfering RNAs (siRNAs). Herein, we describe a novel strategy to specifically deliver siRNAs to murine CD4(+) T cells using targeted lipid nanoparticles (tLNPs). To increase the efficacy of siRNA delivery, these tLNPs have been formulated with several lipids designed to improve the stability and efficacy of siRNA delivery. The tLNPs were surface-functionalized with anti-CD4 monoclonal antibody to permit delivery of the siRNAs specifically to CD4(+) T lymphocytes. Ex vivo, tLNPs demonstrated specificity by targeting only primary CD4(+) T lymphocytes and no other cell types. Systemic intravenous administration of these particles led to efficient binding and uptake into CD4(+) T lymphocytes in several anatomical sites including the spleen, inguinal lymph nodes, blood, and the bone marrow. Silencing by tLNPs occurs in a subset of circulating and resting CD4(+) T lymphocytes. Interestingly, we show that tLNP internalization and not endosome escape is a fundamental event that takes place as early as 1 h after systemic administration and determines tLNPs' efficacy. Taken together, these results suggest that tLNPs may open new avenues for the manipulation of T cell functionality and may help to establish RNAi as a therapeutic modality in leukocyte-associated diseases.

Improving bioavailability and biodistribution of anti-HIV chemotherapy

In the context of the treatment of HIV/AIDS, many improvements have been achieved since the introduction of the combination therapy (HAART). Nevertheless, no cure for this disease has been so far possible, because of some particular features of the therapies. Among them, two important ones have been selected and will be the subject of this review. The first main concern in the treatments is the poor drug bioavailability, resulting in repeated administrations and therefore a demanding compliance (drug regimens consist of multiple drugs daily intake, and non-adherence to therapy is among the important reasons for treatment failure). A second important challenge is the need to target the drugs into the so-called reservoirs and sanctuaries, i.e. cells or body compartments where drugs cannot penetrate or are distributed in sub-active concentrations. The lack of antiviral action in these regions allows the virus to lie latent and start to replicate at any moment after therapy suspension. Recent drug delivery strategies addressing these two limitations will be presented in this review. In the first part, strategies to improve the bioavailability are proposed in order to overcome the absorption or the target cell barrier, or to extend the efficacy time of drugs. In the second section, the biodistribution issues are considered in order to target the drugs into the reservoirs and the sanctuaries, in particular the mononuclear phagocyte system and the brain.

Use of carbosilane dendrimer to switch macrophage polarization for the acquisition of antitumor functions

Tumor microenvironment favors the escape from immunosurveillance by promoting immunosuppression and blunting pro-inflammatory responses. Since most tumor-associated macrophages (TAM) exhibit an M2-like tumor cell growth promoting polarization, we have studied the role of 2G-03NN24 carbosilane dendrimer in M2 macrophage polarization to evaluate the potential application of dendrimers in tumor immunotherapy. We found that the 2G-03NN24 dendrimer decreases LPS-induced IL-10 production from in vitro generated monocyte-derived M2 macrophages, and also switches their gene expression profile towards the acquisition of M1 polarization markers (INHBA, SERPINE1, FLT1, EGLN3 and ALDH1A2) and the loss of M2 polarization-associated markers (EMR1, IGF1, FOLR2 and SLC40A1). Furthermore, 2G-03NN24 dendrimer decreases STAT3 activation. Our results indicate that the 2G-03NN24 dendrimer can be a useful tool for antitumor therapy by virtue of its potential ability to limit the M2-like polarization of TAM.

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.

Nanotech-derived topical microbicides for HIV prevention: the road to clinical development

More than three decades since its discovery, HIV infection remains one of the most aggressive epidemics worldwide, with more than 35 million people infected. In sub-Saharan Africa, heterosexual transmissions represent nearly 80% of new infections, with 50% of these occurring in women. In an effort to stop the dramatic spread of the HIV epidemic, new preventive treatments, such as microbicides, have been developed. Nanotechnology has revolutionized this field by designing and engineering novel highly effective nano-sized materials as microbicide candidates. This review illustrates the most recent advances in nanotech-derived HIV prevention strategies, as well as the main steps required to translate promising in vitro results into clinical trials.

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.