Zinc(II) Iminopyridine Complexes as Antibacterial Agents: A Structure-to-Activity Study.

Antibiotic resistance is currently a global health emergency. Metallodrugs, especially metal coordination complexes, comprise a broad variety of candidates to combat antibacterial infections. In this work, we designed a new family of Schiff base zinc(II) complexes with iminopyridine as an organic ligand and different inorganic ligands: chloride, nitrate, and acetate. The antibacterial effect of the Zn(II) complexes was studied against planktonic bacterial cells of Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) strains. The results showed a moderate biocide activity in both types of planktonic bacteria, which arises from the metal complexation to the Schiff base ligand. Importantly, we confirmed the crucial effect of the metal, with Zn(II) improving the activity of Cu(II) counterparts previously reported. On the other hand, the impact of the inorganic ligands was not significant for the antibacterial effect but was relevant for the complex solubility. Finally, as proof of concept of topical antibacterial formulation, we formulated an emulsion containing the most lipophilic Zn(II) complex and confirmed a sustained release for 24 h in a vertical cell diffusion assay. The promising activity of iminopyridine Zn(II) complexes is potentially worth exploring in more detailed studies.

Combination of Copper Metallodendrimers with Conventional Antitumor Drugs to Combat Cancer in In Vitro Models.

Copper carbosilane metallodendrimers containing chloride ligands and nitrate ligands were mixed with commercially available conventional anticancer drugs, doxorubicin, methotrexate and 5-fluorouracil, for a possible therapeutic system. To verify the hypothesis that copper metallodendrimers can form conjugates with anticancer drugs, their complexes were biophysically characterized using zeta potential and zeta size methods. Next, to confirm the existence of a synergetic effect of dendrimers and drugs, in vitro studies were performed. The combination therapy has been applied in two cancer cell lines: MCF-7 (human breast cancer cell line) and HepG2 (human liver carcinoma cell line). The doxorubicin (DOX), methotrexate (MTX) and 5-fluorouracil (5-FU) were more effective against cancer cells when conjugated with copper metallodendrimers. Such combination significantly decreased cancer cell viability when compared to noncomplexed drugs or dendrimers. The incubation of cells with drug/dendrimer complexes resulted in the increase of the reactive oxygen species (ROS) levels and the depolarization of mitochondrial membranes. Copper ions present in the dendrimer structures enhanced the anticancer properties of the whole nanosystem and improved drug effects, inducing both the apoptosis and necrosis of MCF-7 (human breast cancer cell line) and HepG2 (human liver carcinoma cell line) cancer cells.

UV-Cured Antibacterial Hydrogels Based on PEG and Monodisperse Heterofunctional Bis-MPA Dendrimers.

Bacterial infections are one of the major threats to human health due to the raising crisis of antibiotic resistance. Herein, second generation antibacterial heterofunctional dendrimers based on 2,2-bis(methylol)propionic acid were synthesized. The dendrimers possessed six alkenes and 12 ammonium end-groups per molecule and were used to fabricate antibacterial hydrogels together with dithiol-functional polyethylene glycol (mol wt of 2, 6 and 10 kDa) as crosslinkers via thiol-ene chemistry. The network formation can be completed within 10 s upon UV-irradiation as determined by the stabilization of the storage modulus in a rheometer. The hydrogels swelled in aqueous media and could be functionalized with the N-hydroxysuccinimide ester of the dye disperse red 13, which allowed for visually studying the degradation of the hydrogels through the hydrolysis of the ester bonds of the dendritic component. The maximum swelling ratio of the gels was recorded within 4-8 h and the swelling ratios increased with higher molecular weight of the polyethylene glycol crosslinker. The gel formed with 10 kDa polyethylene glycol crosslinker showed the highest swelling ratio of 40 and good mechanical properties, with a storage modulus of 8 kPa. In addition, the hydrogels exhibited good biocompatibility towards both human fibroblasts and mouse monocytes, while showing strong antibacterial activity against both gram-positive and gram-negative bacteria.

Accelerated Chemoselective Reactions to Sequence-Controlled Heterolayered Dendrimers.

Chemoselective reactions are a highly desirable approach to generate well-defined functional macromolecules. Their extraordinary efficiency and selectivity enable the development of flawless structures, such as dendrimers, with unprecedented structure-to-property capacity but with typically tedious synthetic protocols. Here we demonstrate the potency of chemoselective reactions to accomplish sequence-controlled heterolayered dendrimers. An accurate accelerated design of bis-MPA monomers with orthogonally complementary moieties and a wisely selected chemical toolbox generated highly complex monodisperse dendrimers through simplified protocols. The versatility of the strategy was proved by obtaining different dendritic families with different properties after altering the order of addition of the monomers. Moreover, we evaluated the feasibility of the one-pot approach toward these heterolayered dendrimers as proof-of-concept.

Fine-Tuning the Interaction and Therapeutic Effect of Cu(II) Carbosilane Metallodendrimers in Cancer Cells: An In Vitro Electron Paramagnetic Resonance Study.

Copper(II) carbosilane metallodendrimers are promising nanosized anticancer metallodrugs. The precise control on their design enables an accurate structure-to-activity study. We hypothesized that different structural features, such as the dendrimer generation and metal counterion, modulate the interaction with tumor cells, and subsequently, the effectivity and selectivity of the therapy. A computer-aided analysis of the electron paramagnetic resonance (EPR) spectra allowed us to obtain dynamical and structural details on the interactions over time between the dendrimers and the cells, the myeloid U937 tumor cells and peripheral blood mononuclear cells (PBMC). The intracellular fate of the metallodendrimers was studied through a complete in vitro evaluation, including cytotoxicity, cytostaticity, and sublethal effects regarding mitochondria function, lysosomal compartments, and autophagic organelle involvement. EPR results confirmed a higher membrane stabilization for chloride dendrimers and low generation complexes, which ultimately influence the metallodrug uptake and intracellular fate. The in vitro evaluation revealed that Cu(II) metallodendrimers are cytostatic and moderate cytotoxic agents for U937 tumor cells, inducing death processes through the mitochondria-lysosome axis as well as autophagic vacuole formation, while barely affecting healthy monocytes. The study provided valuable insight into the mechanism of action of these nanosized metallodrugs and relevant structural parameters affecting the activity.

Synthesis of Heterofunctional Polyester Dendrimers with Internal and External Functionalities as Versatile Multipurpose Platforms.

Heterofunctional dendrimers with internal and external representations of functionalities are considered as the ultimate dendritic frameworks. This is reflected by their unprecedented scaffolding, such as precise control over the structure, molecular weight, number, and location of different cargos across the whole dendritic skeleton. Consequently, these dendrimers with multipurpose characters are the pinnacle of precision polymers and thereof are highly attractive to the scientific community as they can find use in a great number of cutting-edge applications, especially as discrete unimolecular carriers for therapeutic exploitation. Unfortunately, most established dendrimer families display external functionalities but lack internal scaffolding ability, which leads to inherent limitations to their full potential use as precision carriers. Consequently, here, we embark on a novel synthetic strategy facilitating the introduction of internal functionalization of established dendrimers. As a proof of concept, a new class of internally and externally functionalized multipurpose dendrimers based on the established 2,2-bis(methylol)propionic acid (bis-MPA) was successfully obtained by the elegant and simple design of AB2C monomers, amalgamated from two traditional AB2 monomers. Utilizing fluoride-promoted esterification (FPE), straightforward layer-by-layer divergent growth up to the fourth generation was successful in less than one day of reaction time, with a molecular weight of 15 kDa, and displaying 93 reactive groups divided by 45 internal and 48 external functionalities. The feasibility of postfunctionalization through click reactions is demonstrated, where the fast and effective attachment of drugs, dyes, and PEG chains is achieved, as well as cross-linking into multifunctional hydrogels. The simplicity and versatility of the presented strategy can easily be transferred to generate a myriad of functional materials such as polymers, surfaces, nanoparticles, or biomolecules.

Lipidomic profiling of chorionic villi in the placentas of women with chronic venous disease.

Background: Chronic venous disease (CVD) is a prevalent lower limb venous pathology that especially affects women, who also show an increased risk of this disease during pregnancy. Studies have shown significant structural changes in the placentas of women with CVD and several markers of tissue damage have been also described. Patients and Methods: To try to understand the different placental pathologies, research efforts have focused on examining metabolomic profiles as indicators of the repercussions of these vascular disorders. This study examines changes produced in the metabolomic profiles of chorionic villi in the placentas of women with CVD. In a study population of 12 pregnant women, 6 with and 6 without CVD, we compared through mass spectroscopy coupled to ultra-high performance liquid chromatography (UHPLC-MS), 240 metabolites in chorionic villus samples. Results: This study is the first to detect in the placental villi of pregnant women with CVD, modifications in lysophosphatidylcholines and amino acids along with diminished levels of other lipids such as triglycerides, sphingomyelins, and non-esterified omega 9 fatty acids, suggesting a role of these abnormalities in the pathogenesis of CVD. Conclusions: Our findings are a starting point for future studies designed to examine the impacts of CVD on maternal and fetal well-being.

Function Oriented Molecular Design: Dendrimers as Novel Antimicrobials.

In recent years innovative nanostructures are attracting increasing interest and, among them, dendrimers have shown several fields of application. Dendrimers can be designed and modified in plentiful ways giving rise to hundreds of different molecules with specific characteristics and functionalities. Biomedicine is probably the field where these molecules find extraordinary applicability, and this is probably due to their multi-valency and to the fact that several other chemicals can be coupled to them to obtain desired compounds. In this review we will describe the different production strategies and the tools and technologies for the study of their characteristics. Finally, we provide a panoramic overview of their applications to meet biomedical needs, especially their use as novel antimicrobials.

Fluoride-promoted esterification with imidazolide-activated compounds: a modular and sustainable approach to dendrimers.

Based on the growing demand for facile and sustainable synthetic methods to structurally perfect polymers, we herein describe a significant improvement of esterification reactions capitalizing on 1,1'-carbonyldiimidazole (CDI). Cesium fluoride was shown to be an essential catalyst for these reactions to reach completion. This approach was successfully applied to the synthesis of structurally flawless and highly functional polyester dendrimers employing traditional and accelerated growth strategies. A sixth generation bis-MPA dendrimer with a molecular weight of 22.080 Da and 192 peripheral hydroxy groups was isolated in less than one day of total reaction time. Large quantities of dendrimers were obtained in high yields (>90%) using simple purification steps under sustainable conditions. The fluoride-promoted esterification (FPE) via imidazolide-activated compounds is wide in scope and constitutes a potentially new approach toward functional polymers and other materials.

Carbon-monoxide-releasing molecules for the delivery of therapeutic CO in vivo.

The development of carbon-monoxide-releasing molecules (CORMs) as pharmaceutical agents represents an attractive and safer alternative to administration of gaseous CO. Most CORMs developed to date are transition-metal carbonyl complexes. Although such CORMs have showed promising results in the treatment of a number of animal models of disease, they still lack the necessary attributes for clinical development. Described in this Minireview are the methods used for CORM selection, to date, and how new insights into the reactivity of metal-carbonyl complexes in vivo, together with advances in methods for live-cell CO detection, are driving the design and synthesis of new CORMs, CORMs that will enable controlled CO release in vivo in a spatial and temporal manner without affecting oxygen transport by hemoglobin.

Shell Formulation in Soft Gelatin Capsules: Design and Characterization.

Soft gelatin capsules (SGCs) are the most widely used pharmaceutical form after tablets. The active components, active pharmaceutical ingredients (APIs), or nutrients are dissolved, dispersed, or suspended in a liquid or semisolid fill, which is covered with a gelatin shell. Several factors can modify the properties of the gelatin shell and subsequently affect their operative handling during manufacturing process and the stability of the soft gelatin capsules. Three elements appear to be crucial: the shell formulation (type and content of the different components such as gelatins-source, extraction method-plasticizers, or additives); the manufacture and storage conditions (temperature, humidity, light) as well as the interactions between fill-shell formulas. Mechanical and thermal analysis arise as straightforward but highly useful tools to monitor the properties of the gelatin shell. This review provides an updated overview on the shell formulation and design. Additionally, it presents the uses of mechanical and thermal techniques to characterize and evaluate the impact of different parameters on the gelatin behavior over the production and stability of these pharmaceutical forms. This will help to detect changes that are yet not visible by visual inspection ensuring a suitable finished product over its shelf-life.

Fine-Tuning the Amphiphilic Properties of Carbosilane Dendritic Networks towards High-Swelling Thermogels.

Dendritic hydrogels based on carbosilane crosslinkers are promising drug delivery systems, as their amphiphilic nature improves the compatibility with poorly water-soluble drugs. In this work, we explored the impact of the complementary polymer on the amphiphilic properties of the dendritic network. Different polymers were selected as precursors, from the highly lipophilic propylene glycol (PPG) to the hydrophilic polyethylene glycol (PEG), including amphiphilic Pluronics L31, L35 and L61. The dithiol polymers reacted with carbosilane crosslinkers through UV-initiated thiol-ene coupling (TEC), and the resultant materials were classified as non-swelling networks (for PPG, PLUL31 and PLUL61) and high-swelling hydrogels (for PEG and PLUL35). The hydrogels exhibited thermo-responsive properties, shrinking at higher temperatures, and exhibited an intriguing drug release pattern due to internal nanostructuring. Furthermore, we fine-tuned the dendritic crosslinker, including hydroxyl and azide pendant groups in the focal point, generating functional networks that can be modified through degradable (ester) and non-degradable (triazol) bonds. Overall, this work highlighted the crucial role of the amphiphilic balance in the design of dendritic hydrogels with thermo-responsive behavior and confirmed their potential as functional networks for biomedical applications.

Bifunctional Carbosilane Dendrimers for the Design of Multipurpose Hydrogels with Antibacterial Action.

The emergence of antibiotic resistance is a serious global health problem. There is an incessant demand for new antimicrobial drugs and materials that can address this global issue from different angles. Dendritic hydrogels have appeared as a promising strategy. A family of bifunctional amphiphilic carbosilane dendrimers was designed and employed as nanosized cross-linking points for the synthesis of high-swelling hydrogels using the highly efficient Thiol-Ene click reaction for their preparation. Both stoichiometric and off-stoichiometric conditions were studied, generating hydrogels with pendant hydroxyl or alkene moieties. These hydrogels were found to be tunable antibacterial materials. They can easily be postmodified with relevant antibiotic moieties through covalent attachment on the hydroxyl or alkene pendant groups, generating ammonium-decorated networks with temperature and pH-responsive properties. Additionally, they can efficiently encapsulate drugs with poor solubility in water, like ciprofloxacin, and perform a sustained release over time, as demonstrated in preliminary assays against Staphylococcus aureus.

Synthesis and biophysical evaluation of carbosilane dendrimers as therapeutic siRNA carriers.

Gene therapy presents an innovative approach to the treatment of previously incurable diseases. The advancement of research in the field of nanotechnology has the potential to overcome the current limitations and challenges of conventional therapy methods, and therefore to unlocking the full potential of dendrimers for use in the gene therapy of neurodegenerative disorders. The blood-brain barrier (BBB) poses a significant challenge when delivering therapeutic agents to the central nervous system. In this study, we investigated the biophysical properties of dendrimers and their complexes with siRNA directed against the apolipoprotein E (APOE) gene to identify an appropriate nanocarrier capable of safely delivering the cargo across the BBB. Our study yielded valuable insights into the complexation process, stability over time, the mechanisms of interaction, the influence of dendrimers on the oligonucleotide's spatial structure, and the potential cytotoxic effects on human cerebral microvascular endothelium cells. Based on our findings, we identified that the dendrimer G3Si PEG6000 was an optimal candidate for further research, potentially serving as a nanocarrier capable of safely delivering therapeutic agents across the BBB for the treatment of neurodegenerative disorders.

Amphiphilic Dendritic Hydrogels with Carbosilane Nanodomains: Preparation and Characterization as Drug Delivery Systems.

Carbosilane dendrimers are hyperbranched lipophilic scaffolds widely explored in biomedical applications. This work exploits, for the first time, the ability of these scaffolds to generate functional hydrogels with amphiphilic properties. The monodispersity and multivalency enable a precise synthetic control of the network, while the lipophilicity improves the compatibility with poorly soluble cargo. The first family of cleavable carbosilane dendrimers was designed for this purpose, overcoming one of the main drawbacks of these type of dendrimers. Biodegradable dendritic low-swelling hydrogels with aromatic nanodomains were easily prepared using the highly efficient click thiol-ene chemistry. Our studies through electron-paramagnetic resonance, molecular dynamics simulations, and experimental assays confirmed the impact of the carbosilane dendritic nanodomains in both the encapsulation and the release pattern of model drugs such as ibuprofen and curcumin. Curcumin-loaded hydrogels were further tested in in vitro assays against advanced prostate cancer cells. The dendritic hydrogels not only enabled drugs encapsulation; as proof of concept, ibuprofen was efficiently attached via fluoride-promoted esterification and was enzymatically cleaved, achieving a controlled release over time.

Synthesis of cationic carbosilane dendrimers via click chemistry and their use as effective carriers for DNA transfection into cancerous cells.

New amine-terminated carbosilane dendrimers have been prepared by a Huisgen cycloaddition ("click chemistry" reaction) of azide-terminated carbosilane dendrimers with two different propargyl amines. The corresponding cationic derivatives with peripheral ammonium groups were obtained by subsequent addition of MeI. Quaternized dendrimers are soluble and stable in water or other protic solvents for long time periods, and have been studied as nonviral vectors for the transfection of DNA to cancer cells. In this study DNA-dendrimeric nanoparticles (dendriplexes) formulated with two different families of cationic carbosilane dendrimers (family 1 (G1, G2 and G3) and family 2 (G1, G2)) were characterized and evaluated for their ability to transfect cells in vitro and in vivo. Dendriplex derived from second generation dendrimer of family 1 (F1G2 5/1 (+/-)) increased the efficiency of plasmid-mediated gene transfer in HepG2 cells as compared to naked DNA and the commercial control dendrimer. Also, intravenously administered dendriplex F1G3 20/1 (+/-) is superior in terms of gene transfer efficiency in vivo.

Dendrimers and Dendritic Materials against Infectious Diseases.

The COVID-19 pandemic showed more deeply the need of our society to provide new therapeutic strategies to fight infectious diseases, not only against currently known illnesses, where common antibiotics and drugs appear to be not fully effective, but also against new infectious threats that may arise [...].

Direct and Reverse Pluronic Micelles: Design and Characterization of Promising Drug Delivery Nanosystems.

Pluronics are a family of amphiphilic block copolymers broadly explored in the pharmaceutical field. Under certain conditions, Pluronics self-assemble in different structures including nanosized direct and reverse micelles. This review provides an overview about the main parameters affecting the micellization process of Pluronics, such as polymer length, fragments distribution within the chain, solvents, additives and loading of cargo. Furthermore, it offers a guide about the most common techniques used to characterize the structure and properties of the micelles. Finally, it presents up-to-date approaches to improve the stability and drug loading of Pluronic micelles. Special attention is paid to reverse Pluronics and reverse micelles, currently underexplored in the literature. Pluronic micelles present a bright future as drug delivery agents. A smart design and thorough characterization will improve the transfer to clinical applications.

Insight on the Structure-to-Activity of Carbosilane Metallodendrimers in the Fight against Staphylococcus aureus Biofilms.

Biofilm formation is a critical health concern, involved in most human bacterial infections. Combatting this mechanism, which increases resistance to traditional antibiotics and host immune defences, requires novel therapeutic approaches. The remarkable biocide activity and the monodispersity of carbosilane metallodendrimers make them excellent platforms to evaluate the impact of different structural parameters on the biological activity. In this work, we explore the influence of iminopyridine ring substituents on the antibacterial activity against planktonic and biofilm Staphylococcus aureus. New families of first-generation Ru(II) and Cu(II) metallodendrimers were synthesised and analysed, in comparison to the non-substituted counterparts. The results showed that the presence of methyl or methoxy groups in meta position to the imine bond decreased the overall positive charge on the metal ion and, subsequently, the activity against planktonic bacteria. However, it seemed a relevant parameter to consider for the prevention of biofilm formation, if they contribute to increasing the overall lipophilicity. An optimum balance of the charge and lipophilicity of the metallodrug, accomplished through structural design, will provide effective biocide agents against bacteria biofilms.

Elaborated study of Cu(II) carbosilane metallodendrimers bearing substituted iminopyridine moieties as antitumor agents.

Iminopyridine-decorated carbosilane metallodendrimers have recently emerged as a promising strategy in the treatment of cancer diseases. Their unique features such as the nanometric size, the multivalent nature and the structural perfection offer an extraordinary platform to explore structure-to-property relationships. Herein, we showcase the outstanding impact on the antitumor activity of a parameter not explored before: the iminopyridine substituents in meta position. New Cu(II) carbosilane metallodendrimers, bearing methyl or methoxy substituents in the pyridine ring, were synthesized and thoroughly characterized. Electron Paramagnetic Resonance (EPR) was exploited to unveil the properties of the metallodendrimers. This study confirmed the presence of different coordination modes of the Cu(II) ion (Cu-N2O2, Cu-N4 and Cu-O4), whose ratios were determined by the structural features of the dendritic molecules. These metallodendrimers exhibited IC50 values in the low micromolar range (<6 µM) in tumor cell lines such as HeLa and MCF-7. The subsequent in vitro assays on both healthy (PBMC) and tumor (U937) myeloid cells revealed two key facts which improved the cytotoxicity and selectivity of the metallodrug: First, maximizing the Cu-N2O2 coordination mode; second, adequately selecting the pair ring-substituent/metal-counterion. The most promising candidates, G1(-CH3)Cl (8) and G1(-OCH3)NO3(17), exhibited a substantial increase in the antitumor activity in U937 tumor cells, compared to the non-substituted counterparts, probably through two different ROS-production pathways.