Silver Nanoparticles Modified by Carbosilane Dendrons and PEG as Delivery Vectors of Small Interfering RNA.

The fact that cancer is one of the leading causes of death requires researchers to create new systems of effective treatment for malignant tumors. One promising area is genetic therapy that uses small interfering RNA (siRNA). These molecules are capable of blocking mutant proteins in cells, but require specific systems that will deliver RNA to target cells and successfully release them into the cytoplasm. Dendronized and PEGylated silver nanoparticles as potential vectors for proapoptotic siRNA (siMCL-1) were used here. Using the methods of one-dimensional gel electrophoresis, the zeta potential, dynamic light scattering, and circular dichroism, stable siRNA and AgNP complexes were obtained. Data gathered using multicolor flow cytometry showed that AgNPs are able to deliver (up to 90%) siRNAs efficiently to some types of tumor cells, depending on the degree of PEGylation. Analysis of cell death showed that complexes of some AgNP variations with siMCL-1 lead to ~70% cell death in the populations that uptake these complexes due to apoptosis.

Silver Nanoparticles Surface-Modified with Carbosilane Dendrons as Carriers of Anticancer siRNA.

Gene therapy is a promising approach in cancer treatment; however, current methods have a number of limitations mainly due to the difficulty in delivering therapeutic nucleic acids to their sites of action. The application of non-viral carriers based on nanomaterials aims at protecting genetic material from degradation and enabling its effective intracellular transport. We proposed the use of silver nanoparticles (AgNPs) surface-modified with carbosilane dendrons as carriers of anticancer siRNA (siBcl-xl). Using gel electrophoresis, zeta potential and hydrodynamic diameter measurements, as well as transmission electron microscopy, we characterized AgNP:siRNA complexes and demonstrated the stability of nucleic acid in complexes in the presence of RNase. Hemolytic properties of free silver nanoparticles and complexes, their effect on lymphocyte proliferation and cytotoxic activity on HeLa cells were also examined. Confocal microscopy proved the effective cellular uptake of complexes, indicating the possible use of this type of silver nanoparticles as carriers of genetic material in gene therapy.

Carbosilane Dendron-Peptide Nanoconjugates as Antimicrobial Agents.

Over the last decades, multidrug-resistant bacteria have emerged and spread, increasing the number of bacteria, against which commonly used antibiotics are no longer effective. It has become a serious public health problem whose solution requires medical research in order to explore novel effective antimicrobial molecules. On the one hand, antimicrobial peptides (AMPs) are regarded as good alternatives because of their generally broad-spectrum activities, but sometimes they can be easily degraded by the organism or be toxic to animal cells. On the other hand, cationic carbosilane dendrons, whose focal point can be functionalized in many different ways, have also shown good antimicrobial activity. In this work, we synthetized first- and second-generation cationic carbosilane dendrons with a maleimide molecule on their focal point, enabling their functionalization with three different AMPs. After different microbiology studies, we found an additive effect between first-generation dendron and AMP3 whose study reveals three interesting effects: (i) bacteria aggregation due to AMP3, which could facilitate bacteria detection or even contribute to antibacterial activity by preventing host cell attack, (ii) bacteria disaggregation capability of second-generation cationic dendrons, and (iii) a higher AMP3 aggregation ability when dendrons were added previously to peptide treatment. These compounds and their different effects observed over bacteria constitute an interesting system for further mechanism studies.

Sulfonate-terminated carbosilane dendron-coated nanotubes: a greener point of view in protein sample preparation.

Reduction or removal of solvents and reagents in protein sample preparation is a requirement. Dendrimers can strongly interact with proteins and have great potential as a greener alternative to conventional methods used in protein sample preparation. This work proposes the use of single-walled carbon nanotubes (SWCNTs) functionalized with carbosilane dendrons with sulfonate groups for protein sample preparation and shows the successful application of the proposed methodology to extract proteins from a complex matrix. SEM images of nanotubes and mixtures of nanotubes and proteins were taken. Moreover, intrinsic fluorescence intensity of proteins was monitored to observe the most significant interactions at increasing dendron generations under neutral and basic pHs. Different conditions for the disruption of interactions between proteins and nanotubes after protein extraction and different concentrations of the disrupting reagent and the nanotube were also tried. Compatibility of extraction and disrupting conditions with the enzymatic digestion of proteins for obtaining bioactive peptides was also studied. Finally, sulfonate-terminated carbosilane dendron-coated SWCNTs enabled the extraction of proteins from a complex sample without using non-environmentally friendly solvents that were required so far. Graphical Abstract Green protein extraction from a complex sample employing carbosilane dendron coated nanotubes.

Prospects of Cationic Carbosilane Dendronized Gold Nanoparticles as Non-viral Vectors for Delivery of Anticancer siRNAs siBCL-xL and siMCL-1.

Cancer is one of the most important problems of modern medicine. At the present time, gene therapy has been developed against cancer, which includes the delivery of anticancer small interfering RNAs (siRNAs) directed at cancer proteins. The prospect of creating drugs based on RNA interference implies the use of delivery systems. Metal nanoparticles are the most studied objects for medicine, including their application as non-viral vectors. We have synthesized gold nanoparticles (AuNPs) modified with cationic carbosilane dendrons of 1-3 generations, with a positive charge on the surface, gold nanoparticles can effectively bind small interfering RNAs. Using a photometric viability test and flow cytometry, we assessed the ability of dendronized gold nanoparticles in delivering siRNAs to tumor cells. The efficiency of the complexes in initiating apoptosis was measured and, also, the overall effect of proapoptotic siRNA on cells. AuNP15 has both the highest efficacy and toxicity. The delivery efficiency in suspension cell lines was 50-60%. Complexes with targeted siRNA decreased cell viability by 20% compared to control and initiated apoptosis.

Dendronized magnetic nanoparticles for HIV-1 capture and rapid diagnostic.

Human immunodeficiency virus type 1 (HIV-1) remains a global public health problem. Detection and reduction of the rates of late diagnosis of HIV-1 infection are one of the main challenges in combating the HIV-1 epidemic. Magnetic nanoparticles (MNPs) have several characteristics that make them susceptible to capture HIV-1 of a wide range of biological samples reducing waiting times between the acquisition of HIV-1 infection and its detection by current techniques. Carbosilane dendrons decorated with peripheral carboxyl groups and alcoxysilane function at the focal point have been used to stabilize MNPs by co-precipitation method in one step. The characterization of these systems and of their carboxylate analogues was performed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), ζ potential and thermal gravimetric analysis (TGA). The ability of carboxyl and carboxylate MNPs to capture R5-HIV-1 and X4-HIV-1 strains was evaluated to achieve a rapid and easy diagnostic method in order to reduce or eliminate the risk of HIV-1 transmission.

Role of cationic carbosilane dendrons and metallic core of functionalized gold nanoparticles in their interaction with human serum albumin.

Functionalization of gold nanoparticles by different chemical groups is an important issue regarding the biomedical applications of such particles. Therefore we have analyzed the interaction between gold nanoparticles functionalized by carbosilane dendrons with human serum albumin at different pHs, and in the presence of the protein unfolding agent, guanidine hydrochloride, using circular dichroism, zeta-potential and fluorescence quenching. The effect of a nanoparticle dendronization and pure dendrons on the immunoreactivity of albumin was estimated using ELISA. In addition, the tool to estimate the binding capacity of dendronized gold nanoparticles using a hydrophobic fluorescent probe 1,8-ANS (1-anilinonaphthalene-8-sulfonic acid) was chosen. We concluded that the effect of a nanoparticle on the structure, immunochemical properties and unfolding of albumin significantly decreased with second and third generations dendrons attached. Differences in pH dependence of the interaction between nanoparticles, their dendrons and albumin showed several effects of the "dendritic corona" and the metallic part of nanoparticle on the protein. These interactions indicate changes in the immunoreactivity of the protein, whereas dendron coating per se had no effect. Thus, dendronization of gold nanoparticles helps to shield them from interactions with plasma proteins.