Alena Krupková

Tetraureido tetranitro-azacalix[4]arene architectures are substitution-tunable supramolecular systems representing promising anion receptors, with potential to form self-assemblies, both modulated by the nature of the aryl substituents.

Dendrimers, constituting a prominent class of monodisperse and multivalent macromolecular compounds with outstanding properties, are characterized by regular and highly branched three-dimensional architectures and well-defined chemical structures. Within each structural type, the skeletal diversity is typically limited to the range of generations. Here, we introduce a novel modular synthetic strategy enabling an increase in the diversity of the dendrimer interior while maintaining its chemical nature. Resulting poly­(amide-carbosilane) (PAMCAS) dendrimers can be fine-tuned within one generation in terms of size, number, and density of end groups, as well as interior free volume. Using a tetravalent core and two building blocksdendritic wedges with branching degrees 3 and 6we demonstrate the potency of this strategy by producing a family of dendrimers through a controlled iterative process that combines highly chemoselective amidic coupling and thiol–ene click reaction (TEC). Within three generations, we prepared 14 structural analogs of PAMCAS dendrimers, systematically varying the order of building blocks and thus their structural profile. The solution properties of the obtained materials were studied by DLS, A4F, diffusion NMR, and molecular modeling. When using exclusively the AB₆ module, the dendritic growth is accelerated and allows straightforward access to structures with extremely high valency in a given generation. As the modular synthetic strategy poses a considerable purification challenge, we implemented organic solvent nanofiltration (OSN) as the main separation tool. Herein, we demonstrate proof-of-principle experiments to evaluate the scope and limits of the use of OSN as an effective separation method in synthetic macromolecular chemistry.

Here, we present a modular synthesis as well as physicochemical and biological evaluation of a new series of amphiphilic dendrons carrying triphenylphosphonium groups at their periphery. Within the series, the size and mutual balance of lipophilic and hydrophilic domains are systematically varied, changing the dendron shape from cylindrical to conical. In physiological solution, the dendrons exhibit very low critical micelle concentrations (2.6-4.9 mu M) and form stable and uniform micelles 6-12 nm in diameter, depending on dendron shape; the results correlate well with molecular dynamics simulations. The compounds show relatively high cytotoxicity (IC50 1.2-21.0 mu M) associated with micelle formation and inversely related to the size of assembled particles. Depending on their shape, the dendrons show promising results in terms of dendriplex formation and antibacterial activity. In addition to simple amphiphilic dendrons, a fluorescently labeled analogue was also prepared and utilized as an additive visualizing the dendron's cellular uptake.

Galectins, the glycan binding proteins, and their respective carbohydrate ligands represent a unique fundamental regulatory network modulating a plethora of biological processes. The advances in galectin-targeted therapy must be based on a deep understanding of the mechanism of ligand-protein recognition. Carbosilane dendrimers, the well-defined and finely tunable nanoscaffolds with low toxicity, are promising for multivalent carbohydrate ligand presentation to target galectin receptors. The study discloses a synthetic method for two types of lactose-functionalized carbosilane glycodendrimers (Lac-CS-DDMs). Furthermore, we report their outstanding, dendritic effect-driven affinity to tandem-type galectins, especially Gal-9. In the enzyme-linked immunosorbent assay, the affinity of the third-generation multivalent dendritic ligand bearing 32 lactose units to Gal-9 reached nanomolar values (IC₅₀ = 970 nM), being a 1400-fold more effective inhibitor than monovalent lactose for this protein. This demonstrates a game-changing impact of multivalent presentation on the inhibitory effect of a ligand as simple as lactose. Moreover, using DLS hydrodynamic diameter measurements, we correlated the increased affinity of the glycodendrimer ligands to Gal-3 and Gal-8 but especially to Gal-9 with the formation of relatively uniform and stable galectin/Lac-CS-DDM aggregates.

Supramolecular structures, such as micelles, liposomes, polymerosomes or dendrimerosomes, are widely studied and used as drug delivery systems. The behavior of amphiphilic building blocks strongly depends on their spatial distribution and shape of polar and nonpolar component. This report is focused on the development of new versatile synthetic protocols for amphiphilic carbosilane dendrons (amp-CS-DDNs) capable of self-assembly to regular micelles and other supramolecular objects. The presented strategy enables the fine modification of amphiphilic structure in several ways and also enables the facile connection of a desired functionality. DLS experiments demonstrated correlations between structural parameters of amp-CS-DDNs and the size of formed nanoparticles. For detailed information about the organization and spatial distribution of amp-CS-DDNs assemblies, computer simulation models were studied by using molecular dynamics in explicit water.

The complexity of drug delivery mechanisms calls for the development of new transport system designs. Here, we report a robust synthetic procedure toward stable glycodendrimer (glyco-DDM) series bearing glucose, galactose, and oligo(ethylene glycol)-modified galactose peripheral units. In vitro cytotoxicity assays showed exceptional biocompatibility of the glyco-DDMs. To demonstrate applicability in drug delivery, the anticancer agent doxorubicin (DOX) was encapsulated in the glyco-DDM structure. The anticancer activity of the resulting glyco-DDM/DOX complexes was evaluated on the noncancerous (BJ) and cancerous (MCF-7 and A2780) cell lines, revealing their promising generation- and concentration-dependent effect. The glyco-DDM/DOX complexes show gradual and pH-dependent DOX release profiles. Fluorescence spectra elucidated the encapsulation process. Confocal fluorescence microscopy demonstrated preferential cancer cell internalization of the glyco-DDM/DOX complexes. The conclusions were supported by computer modeling. Overall, our results are consistent with the assumption that novel glyco-DDMs and their drug complexes are very promising in drug delivery and related applications.

Three series of poly(ionic) carbosilane dendrimers peripherally functionalized with imidazolium groups substituted on N-3 with methyl, isopropyl and 2,6-diisopropylphenyl (Dipp) were prepared up to the 3rd generation together with model monovalent imidazolium iodides and used as N-heterocyclic carbene (NHC) precursors. Catalytic activity of model and dendritic NHCs generated in situ by deprotonation with DBU was tested in redox esterification of α,β-unsaturated aldehydes and the influence of substitution, dendrimer generation, temperature and substrate structure on the reaction outcome was evaluated. Dipp substituted NHCs showed high activity and selectivity in the reaction with primary alcohols. Effectiveness of organic solvent nanofiltration for the recycling of dendritic NHCs was demonstrated on the 1st generation Dipp substituted catalyst in model redox esterification of cinnamaldehyde with benzyl alcohol. A marked increase in both activity and selectivity in the first four reaction runs was observed and this improved performance was preserved in the following catalytic cycles.

The repetition of urea-based binding units within the receptor structure does not only lead to monomer properties multiplication. As confirmed by spectroscopic studies, UV-Vis and ¹H-NMR in classical or competitive titration mode, the attachment to a carrier allocates the active moieties to mutual positions predetermining the function of the whole receptor molecule. Bivalent receptors form self-aggregates. Dendritic receptors with low dihydrogen phosphate loadings offer a cooperative complexation mode associated with a positive dendritic effect. In higher dihydrogen phosphate concentrations, the dendritic branches act independently and the binding mode changes to 1:1 anion: complexation site. Despite the anchoring, the dendritic receptors retain the superior efficiency and selectivity of a monomer, paving the way to recyclable receptors, desirable for economic and ecological reasons.