Carbosilane Dendritic Amphiphiles from Cholesterol or Vitamin E for Micelle Formation.

Cationic dendritic amphiphiles were prepared through the linkage of interesting hydrophobic molecules such as cholesterol or vitamin E to the focal point of carbosilane dendrons. These new dendritic systems self-assembled in saline, producing micellar aggregates with hydrodynamic diameters ranging from 6.5 to 9.2 nm, and critical micelle concentrations of approximately 5 and 10 µM for second- and third-generation systems, respectively. The assemblies were able to encapsulate drugs of different charges (anionic, neutral, and cationic). Surprisingly, a 92% encapsulation efficiency for diclofenac was achieved in micelles prepared from second-generation dendrons. Toxicity measurements on peripheral blood mononuclear cells indicated different behavior depending on the generation, corresponding to the micellar regime. In contrast to the third-generation system, the second-generation system was non-toxic up to 20 µM, opening a window for its use in a micellar regimen, thereby operating as a drug delivery system for different biomedical applications.

The Novel Synthetic Antibiotic BDTL049 Based on a Dendritic System Induces Lipid Domain Formation while Escaping the Cell Envelope Stress Resistance Determinants.

The threat of antimicrobial-resistant bacteria is ever increasing and over the past-decades development of novel therapeutic counter measurements have virtually come to a halt. This circumstance calls for interdisciplinary approaches to design, evaluate and validate the mode of action of novel antibacterial compounds. Hereby, carbosilane dendritic systems that exhibit antimicrobial properties have the potential to serve as synthetic and rationally designed molecules for therapeutic use. The bow-tie type topology of BDTL049 was recently investigated against the Gram-positive model organism Bacillus subtilis, revealing strong bactericidal properties. In this study, we follow up on open questions concerning the usability of BDTL049. For this, we synthesized a fluorescent-labeled version of BDTL049 that maintained all antimicrobial features to unravel the interaction of the compound and bacterial membrane. Subsequently, we highlight the bacterial sensitivity against BDTL049 by performing a mutational study of known resistance determinants. Finally, we address the cytotoxicity of the compound in human cells, unexpectedly revealing a high sensitivity of the eukaryotic cells upon BDTL049 exposure. The insights presented here further elaborate on the unique features of BDTL049 as a promising candidate as an antimicrobial agent while not precluding that further rounds of rational designing are needed to decrease cytotoxicity to ultimately pave the way for synthetic antibiotics toward clinical applicability.

Synthesis and mechanism-of-action of a novel synthetic antibiotic based on a dendritic system with bow-tie topology.

Over the course of the last decades, the continuous exposure of bacteria to antibiotics-at least in parts due to misprescription, misuse, and misdosing-has led to the widespread development of antimicrobial resistances. This development poses a threat to the available medication in losing their effectiveness in treating bacterial infections. On the drug development side, only minor advances have been made to bring forward novel therapeutics. In addition to increasing the efforts and approaches of tapping the natural sources of new antibiotics, synthetic approaches to developing novel antimicrobials are being pursued. In this study, BDTL049 was rationally designed using knowledge based on the properties of natural antibiotics. BDTL049 is a carbosilane dendritic system with bow-tie type topology, which has antimicrobial activity at concentrations comparable to clinically established natural antibiotics. In this report, we describe its mechanism of action on the Gram-positive model organism Bacillus subtilis. Exposure to BDTL049 resulted in a complex transcriptional response, which pointed toward disturbance of the cell envelope homeostasis accompanied by disruption of other central cellular processes of bacterial metabolism as the primary targets of BDTL049 treatment. By applying a combination of whole-cell biosensors, molecular staining, and voltage sensitive dyes, we demonstrate that the mode of action of BDTL049 comprises membrane depolarization concomitant with pore formation. As a result, this new molecule kills Gram-positive bacteria within minutes. Since BDTL049 attacks bacterial cells at different targets simultaneously, this might decrease the chances for the development of bacterial resistances, thereby making it a promising candidate for a future antimicrobial agent.

Prevention of Herpesviridae Infections by Cationic PEGylated Carbosilane Dendrimers.

Infections caused by viruses from the Herpesviridae family produce some of the most prevalent transmitted diseases in the world, constituting a serious global public health issue. Some of the virus properties such as latency and the appearance of resistance to antiviral treatments complicate the development of effective therapies capable of facing the infection. In this context, dendrimers present themselves as promising alternatives to current treatments. In this study, we propose the use of PEGylated cationic carbosilane dendrimers as inhibitors of herpes simplex virus 2 (HSV-2) and human cytomegalovirus (HCMV)infections. Studies of mitochondrial toxicity, membrane integrity, internalization and viral infection inhibition indicated that G2-SN15-PEG, G3-SN31-PEG, G2-SN15-PEG fluorescein isothiocyanate (FITC) labeled and G3-SN31-PEG-FITC dendrimers are valid candidates to target HSV-2 and HCMV infections since they are biocompatible, can be effectively internalized and are able to significantly inhibit both infections. Later studies (including viral inactivation, binding inhibition, heparan sulphate proteoglycans (HSPG)binding and surface plasmon resonance assays) confirmed that inhibition takes place at first infection stages. More precisely, these studies established that their attachment to cell membrane heparan sulphate proteoglycans impede the interaction between viral glycoproteins and these cell receptors, thus preventing infection. Altogether, our research confirmed the high capacity of these PEGylated carbosilane dendrimers to prevent HSV-2 and HCMV infections, making them valid candidates as antiviral agents against Herpesviridae infections.

Cationic Carbosilane Dendrimers Prevent Abnormal α-Synuclein Accumulation in Parkinson's Disease Patient-Specific Dopamine Neurons.

Accumulation of misfolded α-synuclein (α-syn) is a hallmark of Parkinson's disease (PD) thought to play important roles in the pathophysiology of the disease. Dendritic systems, able to modulate the folding of proteins, have emerged as promising new therapeutic strategies for PD treatment. Dendrimers have been shown to be effective at inhibiting α-syn aggregation in cell-free systems and in cell lines. Here, we set out to investigate the effects of dendrimers on endogenous α-syn accumulation in disease-relevant cell types from PD patients. For this purpose, we chose cationic carbosilane dendrimers of bow-tie topology based on their performance at inhibiting α-syn aggregation in vitro. Dopamine neurons were differentiated from induced pluripotent stem cell (iPSC) lines generated from PD patients carrying the LRRK2G2019S mutation, which reportedly display abnormal accumulation of α-syn, and from healthy individuals as controls. Treatment of PD dopamine neurons with non-cytotoxic concentrations of dendrimers was effective at preventing abnormal accumulation and aggregation of α-syn. Our results in a genuinely human experimental model of PD highlight the therapeutic potential of dendritic systems and open the way to developing safe and efficient therapies for delaying or even halting PD progression.

Eradication of Candida albicans Biofilm Viability: In Vitro Combination Therapy of Cationic Carbosilane Dendrons Derived from 4-Phenylbutyric Acid with AgNO3 and EDTA.

Candida albicans is a human pathogen of significant clinical relevance. This pathogen is resistant to different drugs, and most clinical antifungals are not effective against the prevention and treatment of C. albicans infections. As with other microorganisms, it can produce biofilms that serve as a barrier against antifungal agents and other substances, contributing to infection in humans and environmental tolerance of this microorganism. Thus, resistances and biofilm formation make treatment difficult. In addition, the complete eradication of biofilms in implants, catheters and other medical devices, is challenging and necessary to prevent relapses of candidemia. Therefore, it is a priority to find new molecules or combinations of compounds with anti-Candida biofilm activity. Due to the difficulty of treating and removing biofilms, the aim of this study was to evaluate the in vitro ability of different generation of cationic carbosilane dendrons derived from 4-phenylbutyric acid, ArCO2Gn(SNMe3I)m, to eradicate C. albicans biofilms. Here, we assessed the antifungal activity of the second generation dendron ArCO2G2(SNMe3I)4 against C. albicans cells and established biofilms since it managed to seriously damage the membrane. In addition, the combinations of the second generation dendron with AgNO3 or EDTA eradicated the viability of biofilm cells. Alterations were observed by scanning electron microscopy and cytotoxicity was assessed on HeLa cells. Our data suggest that the dendritic compound ArCO2G2(SNMe3I)4 could represent an alternative to control the infections caused by this pathogen.

Interaction of Cationic Carbosilane Dendrimers and Their siRNA Complexes with MCF-7 Cells.

The application of siRNA in gene therapy is mainly limited because of the problems with its transport into cells. Utilization of cationic dendrimers as siRNA carriers seems to be a promising solution in overcoming these issues, due to their positive charge and ability to penetrate cell membranes. The following two types of carbosilane dendrimers were examined: CBD-1 and CBD-2. Dendrimers were complexed with pro-apoptotic siRNA (Mcl-1 and Bcl-2) and the complexes were characterized by measuring their zeta potential, circular dichroism and fluorescence of ethidium bromide associated with dendrimers. CBD-2/siRNA complexes were also examined by agarose gel electrophoresis. Both dendrimers form complexes with siRNA. Moreover, the cellular uptake and influence on the cell viability of the dendrimers and dendriplexes were evaluated using microscopic methods and XTT assay on MCF-7 cells. Microscopy showed that both dendrimers can transport siRNA into cells; however, a cytotoxicity assay showed differences in the toxicity of these dendrimers.

Evaluation of pH-dependent amphiphilic carbosilane dendrons in micelle formation, drug loading and HIV-1 infection.

New amphiphilic carbosilane dendrons with pH-dependent behaviour based on the presence of carboxylate (propionate or succinate) groups at their peripheries and a fatty acid at the focal point were developed. In the presence of salts, they were able to form micelles with critical aggregation concentrations increasing with increasing dendron generation. Their thermodynamic parameters were calculated from surface tension measurements and their diameters at different pHs were measured by dynamic light scattering. These micelles were stable at basic pH but degraded under acidic conditions. No significant differences were found for the propionate and succinate based dendron micelles at basic or acidic pH, but the succinate dendron assemblies were more stable at neutral pH. The properties of these systems as drug nano-carriers were studied using both hydrophilic and hydrophobic molecules, and the drug loading varied with the structure and charge of the drug. In addition, due to the presence of multiple negative charges, the dendrons exhibited anti-HIV activity. Higher generation dendrons with more peripheral carboxylates that were not assembled into micelles were more active than micelles composed of lower generation dendrons having fewer peripheral carboxylates.

Cationic Carbosilane Dendritic Systems as Promising Anti-Amyloid Agents in Type†2 Diabetes.

The most common denominator of many of the neurodegenerative diseases is badly folded protein accumulation, which results in the formation of insoluble protein deposits located in different parts of the organism, causing cell death and tissue degeneration. Dendritic systems have turned out to be a promising new therapeutic approach for the treatment of these diseases due to their ability to modulate the folding of these proteins. With this perspective, and focused on type 2 diabetes (T2D), characterized by the presence of deposits containing the amyloidogenic islet amyloid polypeptide (IAPP), we demonstrate how different topologies of cationic carbosilane dendrimers inhibit the formation of insoluble protein deposits in pancreatic islets isolated from transgenic Tg-hIAPP mice. Also, the results obtained by the modification of dendritic carbosilane wedges with the chemical chaperone 4-phenylbutyric acid (4-PBA) at the focal point confirmed their potential as anti-amyloid agents with a concentration efficiency in their therapeutic action five orders of magnitude lower than that observed for free 4-PBA. Computational studies, which determined the main interaction between IAPP and dendrimers at the atomic level, support the experimental work.

New Ionic Carbosilane Dendrons Possessing Fluorinated Tails at Different Locations on the Skeleton.

The fluorination of dendritic structures has attracted special attention in terms of self-assembly processes and biological applications. The presence of fluorine increases the hydrophobicity of the molecule, resulting in a better interaction with biological membranes and viability. In addition, the development of 19F magnetic resonance imaging (19F-MRI) has greatly increased interest in the design of new fluorinated structures with specific properties. Here, we present the synthesis of new water-soluble fluorinated carbosilane dendrons containing fluorinated chains in different positions on the skeleton, focal point or surface, and their preliminary supramolecular aggregation studies. These new dendritic systems could be considered as potential systems to be employed in drug delivery or gene therapy and monitored by 19F-MRI.

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.