Improved Efficiency of Ibuprofen by Cationic Carbosilane Dendritic Conjugates.

In order to improve the efficiency of the anti-inflammatory drug ibuprofen, cationic carbosilane dendrimers and dendrons with ibuprofen at their periphery or at their focal point, respectively, have been synthesized, and the release of the drug was studied using HPLC. Macrophages were used to evaluate the anti-inflammatory effect of the ibuprofen-conjugated dendritic systems and compared with mixtures of non-ibuprofen dendritic systems in the presence of the drug. The cationic ibuprofen-conjugated dendron was the compound that showed higher anti-inflammatory properties. It reduces the LPS-induced COX-2 expression and decreases the release of several inflammatory cytokines such as TNFα, IL-1ß, IL-6, and CCL3. These results open new perspectives in the use of these compounds as drug carriers.

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.

In vivo delivery of siRNA to the brain by carbosilane dendrimer.

Nanotechnology offers a new platform for therapeutic delivery of antiretrovirals to the central nervous system (CNS). Nanoformulated antiretroviral drugs offer multifunctionality, that is, the ability to package multiple diagnostic and therapeutic agents in the same nanocompose, along with the added provisions of site-directed delivery, delivery across the blood-brain-barrier (BBB), and controlled release of therapeutics. We studied the viability of dendrimers and dendriplexes in human primary astrocytes, as well as their uptake by these astrocytes. Functional validation was performed by using specific siRNA against HIV-1 Nef to interfere to HIV-1 infectivity. A high efficiency in Nef silencing, reducing HIV-1 infectivity was observed in astrocytes treated with dendriplexes compared with control or siRandom treated astrocytes. More interestingly, we studied the biodistribution of the second generation of carbosilane dendrimer loaded with FITC (2G-(SNMe3I)11-FITC) in vivo, in BALB/c mice. Dendriplexes were inoculated into BALB/c mice by the retro-orbital venous plexus, and their localization was determined after 1 and 24h post-injection. Dendriplexes were detected inside the brain by a sensitive imaging system of fluorescent imaging in vivo (IVIS Lumina), and by confocal microscopy analysis of sections of OCT-embedded tissues. The 2G-(SNMe3I)11-FITC dendrimer transported efficiently siRNA into the brain, crossing the BBB. Moreover, this dendrimer successfully delivered and transfected siRNA to HIV-infected human primary astrocytes and achieved gene silencing without causing cytotoxicity. These results highlight the potential of this nanoformulation in the treatment of neurological disorders.

Evaluation of the activity of new cationic carbosilane dendrimers on trophozoites and cysts of Acanthamoeba polyphaga.

Dendrimers are repetitively branched molecules with a broad spectrum of applications, mainly for their antimicrobial properties and as nanocarriers for other molecules. Recently, our research group have synthesized and studied their activity against Acanthamoeba sp., causative agent of a severe ocular disease in humans: Acanthamoeba keratitis. New cationic carbosilane dendrimers were tested against the protozoa forms at different concentrations and for different incubation times. Trophozoite viability was determined by manual counting and cyst viability by observing excystment in microplates with fresh culture medium. Cytotoxicity was checked on HeLa cells using the microculture tetrazolium assay. Alterations were observed by optical microscopy and by flow cytometry staining with propidium iodide. Six out of the 18 dendrimers tested were non-cytotoxic and effective against the trophozoite form, having one of them (dendrimer 14 with an IC50 of 2.4 + 0.1 mg/L) a similar activity to chlorhexidine digluconate (IC50 1.7 + 0.1 mg/L). This dendrimer has a polyphenoxo core and a sulphur atom close to the six -NH3+ terminal groups. On the other hand, only two dendrimers showed some effect against cysts (dendrimers 14 and 17). However, their minimum cysticidal concentrations were cytotoxic and less effective than the control drug. The alterations on the amoeba morphology produced by the treatment with dendrimers were size reduction, increased complexity, loss of acanthopodia and cell membrane disruption. In conclusion, these results suggest that some dendrimers may be studied in animal models to test their effect and that new dendrimers with similar features should be synthesized.

Novel non-viral gene delivery systems composed of carbosilane dendron functionalized nanoparticles prepared from nano-emulsions as non-viral carriers for antisense oligonucleotides.

The development of novel and efficient delivery systems is often the limiting step in fields such as antisense therapies. In this context, poly(d,l-lactide-co-glycolide) acid (PLGA) nanoparticles have been obtained by a versatile and simple technology based on nano-emulsion templating and low-energy emulsification methods, performed in mild conditions, providing good size control. O/W polymeric nano-emulsions were prepared by the phase inversion composition method at 25°C using the aqueous solution/polysorbate80/[4 wt% PLGA in ethyl acetate] system. Nano-emulsions formed at oil-to-surfactant (O/S) ratios between 10/90-90/10 and aqueous contents above 70 wt%. Nano-emulsion with 90 wt% of aqueous solution and O/S ratio of 70/30 was chosen for further studies, since they showed the appropriate characteristics to be used as nanoparticle template: hydrodynamic radii lower than 50 nm and enough kinetic stability. Nanoparticles, prepared from nano-emulsions by solvent evaporation, showed spherical shape, sizes about 40 nm, negative surface charges and high stability. The as-prepared nanoparticles were functionalized with carbosilane cationic dendrons through a carbodiimide-mediated reaction achieving positively charged surfaces. Antisense oligonucleotides were electrostatically attached to nanoparticles surface to perform gene-silencing studies. These complexes were non-haemolytic and non-cytotoxic at the concentrations required. The ability of the complexes to impart cellular uptake was also promising. Therefore, these novel nanoparticulate complexes might be considered as potential non-viral carriers in antisense therapy.

Hyperbranched polymers versus dendrimers containing a carbosilane framework and terminal ammonium groups as antimicrobial agents.

A new family of amine- and ammonium-terminated hyperbranched polycarbosilanes (PCS) and dendrimers has been synthesized. The functionalization of a polycarbosilane matrix was carried out with peripheral allyl groups by two strategies in the case of PCS: 1) hydrosilylation of allyl amines with PCS containing terminal Si-H bonds, or 2) hydrosilylation of PCS-allyl with an aminosilane. Dendrimers with terminal amine groups were synthesized by hydrosilylation of allydimethylamine. Quaternized systems with MeI are soluble and stable in water or other protic solvent. The antibacterial properties of the ammonium-terminated hyperbranched polycarbosilanes and dendrimers have been evaluated showing that they act as potent biocides against Gram-positive and Gram-negative bacterial strains.