Peptide-Based Multicomponent Oligonucleotide Delivery Systems: Optimisation of Poly-<Emphasis Type="SmallCaps">l</Emphasis>-lysine Dendrons for Plasmid DNA Delivery

Gene therapy is a promising means to treat or prevent diseases either through gene silencing or expression. Some of the most effective delivery agents are polycationic dendrimers, which are highly branched constructs incorporating many positively charged groups. Two of the most effective dendrimers are polyethyleneimine (PEI) and poly(amidoamine) (PAMAM), which show high proficiency at overcoming barriers to oligonucleotide delivery. However, because of their abundance of cationic charge, they are associated with severe toxicity. We have therefore aimed to develop a low toxicity oligonucleotide delivery system, incorporating multiple components that have been selected and optimised to overcome the barriers to efficient oligonucleotide delivery. In this work we have focused on improving the toxicity, cellular uptake, and condensation of plasmid DNA (pDNA) through the fusion of synthetic poly-l-lysine (PLL) dendrons with the cell penetrating peptide TAT(48-60). A library of dendron structures, from 4⁺ to 16⁺ charge, and constructs containing six histidine residues, were synthesised. The effects of each modification on pDNA binding and condensation; cellular uptake and toxicity; and the size and zeta-potential of the complexes were assessed to identify the optimum dendron for incorporation into our systems. This work concluded that increasing the dendron charge from 4⁺ to 16⁺ significantly improved cellular uptake and pDNA condensation, with no effect on toxicity, while PLL dendrons with greater than 16⁺ charge could not be efficiently produced. In comparison, the incorporation of six histidines into these constructs had a variable effect on cellular uptake, and generated larger sized complexes, but did not affect toxicity.     

Synthesis of symmetrical and unsymmetrical PAMAM dendrimers by fusion between azide- and alkyne-functionalized PAMAM dendrons

A new convergent synthetic method for the synthesis of PAMAM dendrimers has been developed. The fusion between propargyl-functionalized PAMAM dendrons and azido-functionalized PAMAM dendrons via the Cu(I)-catalyzed Huisgen [2 + 3] dipolar cycloaddition reaction (click chemistry) of an alkyne and an azide leads to the formation of symmetric PAMAM dendrimers in high yields. Furthermore, the coupling reactions between the different generation dendrons afford the size-differentiated unsymmetrical PAMAM dendrimers.     

In vitro activity of steroidal dendrimers on Trypanosoma cruzi epimastigote form with PAMAM dendrons modified by “click” chemistry

The increasing use of dendrimers shows promise for the treatment of inflammatory diseases, Chagas disease and other conditions such as cancer. In this study, the activity of 1st and 2nd generation dendrimers over T. cruzi in the epimastigote stage was tested. Dendrimers were derived from α-ethynylestradiol (EE) modified with PAMAM-type dendrons through a triazole ring. The activity of each compound was evaluated in five doses (from 1.3 to 20 µmol/mL) by flow cytometry, including benznidazole (Bz) as positive control. The findings show that an equivalent concentration of 14.8 µmol/mL of 2nd generation (G) dendrimer is 8 times more effective than Bz at 24 h, and it maintains its superiority at 48 h with an IC₅₀ = 1.25 ± 0.19 µmol/mL. A TUNEL assay showed that dendrimers induce cell death in T. cruzi epimastigotes mostly via apoptosis, unlike Bz, which induces death via necrosis in more than 50% of cells.     

Synthesis and evaluation of novel dendrimers with a hydrophilic interior as nanocarriers for drug delivery

Novel polyester-co-polyether dendrimers consisting of a hydrophilic core were synthesized by a combination of convergent and divergent syntheses. The core was synthesized from biocompatible moieties, butanetetracarboxylic acid and aspartic acid, and the dendrons from PEO (poly(ethylene oxide)), dihydroxybenzoic acid or gallic acid, and PEG monomethacrylate. The dendrimers, Den-1-(G 2) (second generation dendrimer-1) and Den-2-(G 2) (second generation dendrimer-2) consisting of 16 and 24 allyl surface groups, respectively, were obtained by coupling the dendrons to the core. The dendrimer (Den-1-(G 2)-OH) with hydroxyl groups at the surface was synthesized by oxidation of the allyl functional groups of Den-1-(G 2), which was divergently coupled to the dendrons to obtain the third generation dendrimer Den-1-(G 3) consisting of 32 surface groups. The modifications in surface groups and generation of dendrimers were shown to influence the shape of dendrimers in the AFM studies. The aggregation as well as self-assembly of dendrimers was observed at high concentration in water by light scattering studies; however, it was reduced on dilution and in the presence of sodium chloride. Dendrimers demonstrated good ability to encapsulate the guest molecule, with loading of 15.80 and 6.47% w/w for rhodamine and beta-carotene, respectively. UV spectroscopy proved the absence of any pi-pi complexation between the dendrimer and encapsulated compounds. (1)H NMR and FTIR studies showed that the physical entrapment and/or hydrogen bonding by PEO in the interior and branch of the dendrimer are the mechanisms of encapsulation. The release of the encapsulated compounds was found to be slow and sustained, suggesting that these dendrimers can serve as potential drug delivery vehicles.     

Enzymatic activation of hydrophobic self-immolative dendrimers: The effect of reporters with ionizable functional groups

Self-immolative dendrimers are uniquely structured molecules that release multiple tail units through a chain fragmentation initiated by a single cleavage at the dendrimer’s core. Although bioactivation of self-immolative dendritic molecules with only two reporter groups was demonstrated, enzymatic activation failed for self-immolative dendrimers with more reporters. These large and hydrophobic dendrimers aggregated under aqueous conditions and enzyme did not efficiently trigger chain fragmentation. Here we demonstrate a simple solution to the problem of enzymatic activation of hydrophobic self-immolative dendrimers. The reporter units on the dendritic platform were equipped with ionizable functional group. Polar interactions with water significantly decreased hydrophobicity of the dendrimers and prevented aggregate formation. Consequently, hydrophobic self-immolative dendrons were effectively activated.     

Evaluation of poly(amidoamine) dendrimers as potential carriers of iminodiacetic derivatives using solubility studies and 2D-NOESY NMR spectroscopy

The interactions between dendrimers and different types of drugs are nowadays one of the most actively investigated areas of the pharmaceutical sciences. The interactions between dendrimers and drugs can be divided into: internal encapsulation, external electrostatic interaction, and covalent conjugation. In the present study, we investigated the potential of poly(amidoamine) (PAMAM) dendrimers for solubility of four iminodiacetic acid derivatives. We reported that PAMAM dendrimers contribute to significant solubility enhancement of iminodiacetic acid analogues. The nature of the dendrimer–drug complexes was investigated by ¹H NMR and 2D-NOESY spectroscopy. The ¹H NMR analysis proved that the water-soluble supramolecular structure of the complex was formed on the basis of ionic interactions between terminal amine groups of dendrimers and carboxyl groups of drug molecules, as well as internal encapsulation. The 2D-NOESY analysis revealed interactions between the primary amine groups of PAMAM dendrimers and the analogues of iminodiacetic acid. The results of solubility studies together with ¹H NMR and 2D-NOESY experiments suggest that the interactions between PAMAM dendrimers of generation 1–4 and derivatives of iminodiacetic acid are based on electrostatic interactions and internal encapsulation.     

Nanotechnology as a New Therapeutic Approach to Prevent the HIV-Infection of Treg Cells

Background

HIV-1 has proved to infect regulatory T cells (Treg) modifying their phenotype and impairing their suppressive capacity. As Treg cells are a crucial component in the preservation of the immune homeostasis, we researched that the antiviral capacity of carboxilan dendrimers prevents the HIV-1 infection of Treg and their effects. The phenotype and suppressive capacity of Treg treated or non-treated with carbosilane dendrimers were studied by flow cytometry. Treated and non-treated Treg from healthy donors were infected with HIV-1_NL4.3. The infection of Treg cells by HIV-1, and protective effect of two dendrimers were determined by measuring antigen p24^gag in the supernatant of the culture and intracellular.

Results

The Treg cells were treated with cationic and anionic carbosilane dendrimers. The results showed that both dendrimers did not modify the phenotype and functionality of Treg cells compared with non- treated Treg cells. Anionic dendrimers showed high biocompatibility with normal activity of the Treg cells and in antiviral assays. These dendrimers were highly active against HIV-1 preventing the infection of Treg, and were able to protect the Treg from the Foxp3 downregulation induced by the HIV-1 infection.

Conclusions

This is the first work showing that the in vitro use of anionic dendrimers prevent the HIV-1 replication and the infection of expanded Treg cells in culture, which raises the possibility to use Treg cells therapeutically in HIV-1-infected subjects.     

Synthesis and biological studies of 5-aminolevulinic acid-containing dendrimers for photodynamic therapy.

Using a convergent growth approach, a series of novel 5-aminolevulinic acid (ALA)-containing dendrimers have been synthesized. In these molecules, ALA residues are attached to the periphery by ester linkages, with amide bonds connecting the dendrons. Three first-generation dendrimers, bearing either 6 or 9 ALA residues, were synthesized by attachment of a tris(Boc-protected ALA)-containing wedge (1) to a di- or tripodent aromatic, or tripodent aliphatic core. Two second generation 18-ALA-containing dendrimers were also synthesized using a 3,3'-iminodipropionic acid spacer unit between wedge 1 and the aromatic core. These compounds differed only in the distance between the core and the linker unit. The Boc-protected dendrimers were deprotected using trifluoroacetic acid and isolated as their TFA salts. The potential of these ALA ester dendrimers as macromolecular prodrugs for photodynamic therapy has been demonstrated in the tumorigenic keratinocyte PAM 212 cell line.     

Paramagnetic NMR Investigation of Dendrimer-Based Host-Guest Interactions

In this study, the host-guest behavior of poly(amidoamine) (PAMAM) dendrimers bearing amine, hydroxyl, or carboxylate surface functionalities were investigated by paramagnetic NMR studies. 2,2,6,6-Tetramethylpiperidinyloxy (TEMPO) derivatives were used as paramagnetic guest molecules. The results showed that TEMPO-COOH significantly broaden the ¹H NMR peaks of amine- and hydroxyl-terminated PAMAM dendrimers. In comparison, no paramagnetic relaxation enhancement (PRE) was observed between TEMPO-NH₂, TEMPO-OH and the three types of PAMAM dendrimers. The PRE phenomenon observed is correlated with the encapsulation of TEMPO-COOH within dendrimer pockets. Protonation of the tertiary amine groups within PAMAM dendrimers plays an important role during this process. Interestingly, the absence of TEMPO-COOH encapsulation within carboxylate-terminated PAMAM dendrimer is observed due to the repulsion of TEMPO-COO- anion and anionic dendrimer surface. The combination of paramagnetic probes and ¹H NMR linewidth analysis can be used as a powerful tool in the analysis of dendrimer-based host-guest systems.     

Peptide and glycopeptide dendrimers and analogous dendrimeric structures and their biomedical applications

The size of information that can be stored in nucleic acids, proteins, and carbohydrates was calculated. The number of hexamers for peptides is 64,000,000 (20⁶) and seems to be impressive in comparison with 4,096 (4⁶) hexanucleotides, but the number of isomers of hexasaccharides is 1.44 × 10¹⁵. Carbohydrates are therefore the best high-density coding system. This language has been named glycocode resp. sugar code. In comparison with peptide dendrimers, the amount of information carried by glycopeptide dendrimers or glycodendrimers is therefore much higher. This is reflected by the variability of structures and functions (activities). This review is about the broad area of peptide and glycopeptide dendrimers. The dendrimeric state and physicochemical properties and general consequences are described, together with a cluster effect. The impact of cluster effect to biological, chemical, and physical properties is discussed. Synthesis of dendrimers by convergent and divergent approaches, “Lego” chemistry, ligation strategies, and click chemistry is given with many examples. Purification and characterization of dendrimers by chromatographic methods, electromigration methods, and mass spectrometry are briefly mentioned. Different types of dendrimers with cyclic core, i.e. RAFTs, TASPs and analogous cyclic structures, carbopeptides, carboproteins, octopus glycosides, inositol-based dendrimers, cyclodextrins, calix[4]arenes, resorcarenes, cavitands, and porphyrins are given. Dendrimers can be used for creation of libraries, catalysts, and solubilizing agents. Biocompatibility and toxicity of dendrimers is discussed, as well as their applications in nanoscience, nanotechnology, drug delivery, and gene delivery. Carbohydrate interactions of glycopeptide dendrimers (bacteria, viruses, and cancer) are described. Examples of dendrimers as anti-prion agents are given. Dendrimers represent a fast developing area which partly overlaps with nanoparticles and nanotechnologies.     

Oligosaccharide-derivatized dendrimers: defined multivalent inhibitors of the adherence of the cholera toxin B subunit and the heat labile enterotoxin of E. coli to GM1

Poly(propylene imine) dendrimers having four or eight primary amino groups and a Starburst^TM (PAMAM) dendrimer having eight primary amino groups were used as core molecules, to which phenylisothiocyanate derivatized (PITC) galβ1-3galNAcβ1-4[sialic acidβ2-3]-galβ1-4glc (oligo-GM1) residues were covalently attached to yield multivalent oligosaccharides. The synthesis of the oligo-GM1-PITC derivatized dendrimers was monitored using high performance thin layer chromatography, infrared spectroscopy, sialic acid content, and mass spectroscopy. The ability of multivalent oligo-GM1-PITC dendrimers to inhibit the binding of ¹²⁵I-labeled cholera toxin B subunit and the heat labile enterotoxin of E. coli to GM1-coated microtiter wells was determined. IC₅₀s obtained for the oligo-GM1-PITC dendrimers, GM1, and the oligosaccharide moiety of GM1 indicated that the derivatized dendrimers inhibited binding of the choleragenoid and the heat labile enterotoxin to GM1-coated wells at a molar concentration five- to 15-fold lower than native GM1 and more than 1,000-fold lower than that of the free oligosaccharide. This revised version was published online in November 2006 with corrections to the Cover Date.     

Physicochemical and MRI characterization of Gd<Superscript>3+</Superscript>-loaded polyamidoamine and hyperbranched dendrimers

Generation 4 polyamidoamine (PAMAM) and, for the first time, hyperbranched poly(ethylene imine) or polyglycerol dendrimers have been loaded with Gd³⁺ chelates, and the macromolecular adducts have been studied in vitro and in vivo with regard to MRI contrast agent applications. The Gd³⁺ chelator was either a tetraazatetracarboxylate DOTA-pBn⁴⁻ or a tetraazatricarboxylate monoamide DO3A-MA³⁻ unit. The water exchange rate was determined from a ¹⁷O NMR and ¹H Nuclear Magnetic Relaxation Dispersion study for the corresponding monomer analogues [Gd(DO3A-AEM)(H₂O)] and [Gd(DOTA-pBn-NH₂)(H₂O)]⁻ (k _ex²⁹⁸ = 3.4 and 6.6 × 10⁶ s⁻¹, respectively), where H₃DO3A-AEM is {4-[(2-acetylaminoethylcarbamoyl)methyl]-7,10-bis(carboxymethyl-1,4,7,10-tetraazacyclododec-1-yl)}-acetic acid and H₄DOTA-pBn-NH₂ is 2-(4-aminobenzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. For the macromolecular complexes, variable-field proton relaxivities have been measured and analyzed in terms of local and global motional dynamics by using the Lipari–Szabo approach. At frequencies below 100 MHz, the proton relaxivities are twice as high for the dendrimers loaded with the negatively charged Gd(DOTA-pBn)⁻ in comparison with the analogous molecule bearing the neutral Gd(DO3A-MA). We explained this difference by the different rotational dynamics: the much slower motion of Gd(DOTA-pBn)⁻-loaded dendrimers is likely related to the negative charge of the chelate which creates more rigidity and increases the overall size of the macromolecule compared with dendrimers loaded with the neutral Gd(DO3A-MA). Attachment of poly(ethylene glycol) chains to the dendrimers does not influence relaxivity. Both hyperbranched structures were found to be as good scaffolds as regular PAMAM dendrimers in terms of the proton relaxivity of the Gd³⁺ complexes. The in vivo MRI studies on tumor-bearing mice at 4.7 T proved that all dendrimeric complexes are suitable for angiography and for the study of vasculature parameters like blood volume and permeability of tumor vessels. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cyclam cored luminescent dendrimers as ligands for Co(II), Ni(II) and Cu(II) ions

We have investigated the photophysical properties of two dendrimers containing a cyclam core decorated with 4 naphthyl units (G0), 12 dimethoxybenzene and 16 naphthyl units (G2). These dendrimers show fluorescence bands that can be assigned to naphthyl localized excited states (λ_max = 337 nm), naphthyl-amine exciplexes (λ_max = 470 nm) and, for G2, naphthyl excimers (λ_max ca. 400 nm). Cyclam is a very good ligand for transition metal ions and we have investigated complex formation between these dendritic ligands and Ni(II), Co(II) and Cu(II), added as nitrate salts. This process can be monitored by the strong changes, both in shape and intensity, observed in the emission spectra of these dendrimers. Complexation with Cu(II) causes not only changes in the relative intensities of the fluorescence bands, but also the appearance of a new absorption band in the near UV spectral region. An analysis of the titration curves has allowed us to obtain clear evidence for the formation of not only 1:1 species, but also 1:2 metal to ligand species. G2 shows a clear preference, compared to G0, in forming complexes with a 1:2 metal-to-ligand stoichiometry, although it possesses very bulky dendrons appended to the cyclam central unit.     

Synthesis of glycopeptide dendrimers, dimerization and affinity for Concanavalin A

We described herein the synthesis of second generation glycopeptide dendrimers G2a-g presenting variable amino acids placed internally into the multivalent scaffold. The effect of such structural modulation on recognition processes by Concanavalin A (Con A), was then estimated by enhanced-sensitivity Enzyme-Linked Lectin Assay (ELLA). In a complementary study, glycopeptide dendrons of different valencies and including a l-cysteine residue before the dendritic core (G0SH, G1SH and G2SH), were also synthesized and homodimerized. Then, the disulfide-containing glycopeptide dendrimers generated by this convergent approach (G0(2)S(2), G1(2)S(2) and G2(2)S(2)) were used as Con A inhibitors and assayed by ELLA.     

Anionic PAMAM dendrimers as drug delivery vehicles for transition metal-based anticancer drugs

The use of anionic half-generation poly(amidoamine) dendrimers as drug delivery vehicles for [Pt(S,S-dach)(5,6-Me₂phen)]²⁺ (56MESS) (where S,S-dach = 1S,2S-diaminocyclohexane; 5,6-Me₂phen = 5,6-dimethyl-1,10-phenanthroline) and [{Δ,Δ-Ru(phen)₂}₂(μ-bb7)]⁴⁺ (Rubb₇) (where phen = 1,10-phenanthroline; bb7 = 1,7-bis[4-(4′-methyl-2,2′-bipyridyl)heptane]) has been studied by nuclear magnetic resonance spectroscopy. From one- and two-dimensional ¹H NMR spectra both 56MESS and Rubb₇ were found to bind to the surface of generation 3.5, 4.5, 5.5 and 6.5 dendrimers through electrostatic interactions. The higher charge and larger size of Rubb₇ resulted in stronger binding to all dendrimer generations (K_b ? 2 × 10⁵ M⁻¹) compared with 56MESS (K_b ? 1 × 10⁴ M⁻¹). Interestingly, there appeared to be no observable trend between dendrimer size and binding constant strength. The size of the free and 56MESS-bound dendrimers were examined using pulsed-gradient spin-echo NMR. The dendrimers ranged in hydrodynamic diameter from 11 to 20 nm and in all cases were larger than their corresponding full-generation dendrimer. Upon the addition of 56MESS the diameter of the dendrimers increased, consistent with surface binding.     

Enhanced cellular uptake of a triplex-forming oligonucleotide by nanoparticle formation in the presence of polypropylenimine dendrimers

We used polypropylenimine dendrimers for delivering a 31 nt triplex-forming oligonucleotide (ODN) in breast, prostate and ovarian cancer cell lines, using ³²P-labeled ODN. Dendrimers enhanced the uptake of ODN by ~14-fold in MDA-MB-231 breast cancer cells, compared with control ODN uptake. Dendrimers exerted their effect in a concentration- and molecular weight-dependent manner, with generation 4 (G-4) dendrimer having maximum efficacy. A similar increase in ODN uptake was found with MCF-7 and SK-BR-3 (breast), LNCaP (prostate) and SK-OV-3 (ovarian) cancer cells. The dendrimers had no significant effect on cell viability at concentrations at which maximum ODN uptake occurred. [³H]Thymidine incorporation showed that complexing the ODN with G-4 significantly increased the growth-inhibitory effect of the ODN. Western blot analysis showed a significant 65% reduction of c-myc protein level in ODN–G-4 treated cells compared with that of ODN-treated/control cells. Gel electrophoretic analysis showed that ODN remained intact in cells even after 48 h of treatment. The hydrodynamic radii of nanoparticles formed from ODN in the presence of the dendrimers were in the range of 130–280 nm, as determined by dynamic laser light scattering. Taken together, our results indicate that polypropylenimine dendrimers might be useful vehicles for delivering therapeutic oligonucleotides in cancer cells.     

Synthesis and Relaxometric Characterization of New Poly[N,N‐bis(3‐aminopropyl)glycine] (PAPGly) Dendrons Gd‐Based Contrast Agents and Their in Vivo Study by Using the Dynamic Contrast‐Enhanced MRI Technique at Low Field (1 T)

The synthesis of poly[N,N‐bis(3‐aminopropyl)glycine] (PAPGly) dendrons Gd‐based contrast agents (GdCAs) via an orthogonal protection of the different functional groups and an activation/coupling strategy wherein a specific number of synthetic steps add a generation to the existing dendron has been described. The aim of this protocol is to build up two different generations of dendrons ( G‐0 or dendron's core, and G‐1 ) with peripheral NH₂ groups to conjugate a 1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid (DO3A) derivative and afterwards to chelate with Gd³⁺ paramagnetic ions. These complexes, which have a well‐defined molecular weight, are of relevance to MRI as an attempt to gain higher ¹H relaxivity by slowing down the rotation of molecule compared to monomeric Gd(III) complexes used as contrast agents and to increase the number of paramagnetic centers present in one molecular structure. From the study of their water ¹H longitudinal relaxation rate at different magnetic fields (NMRD, Nuclear Magnetic Relaxation Dispersion) and by evaluating the variable temperature ¹⁷O‐NMR data we determined the parameters characterizing the water exchange rate and the rotational correlation time of each complex, both affecting ¹H relaxivity. Furthermore, these two novel PAPGly GdCAs were objects of i) an in vivo study to determine their biodistributions in healthy C57 mice at several time points, and ii) the Dynamic Contrast‐Enhanced MRI (DCE‐MRI) approach to assess their contrast efficiency measured in the tumor region of C57BL/6 mice transplanted subcutaneously with B16‐F10 melanoma cells. The aim of the comparison of these two dendrons GdCAs, having different molecular weights (MW), is to understand how MW and relaxivity may influence the contrast enhancement capabilities in vivo at low magnetic field (1 T). Significant contrast enhancement was observed in several organs (vessel, spleen and liver), already at 5 min post‐injection, for the investigated CAs. Moreover, these CAs induced a marked contrast enhancement in the tumor region, thanks to the enhanced permeability retention effect of those macromolecular structures.     

Carboxymethyl chitosan-poly(amidoamine) dendrimer core–shell nanoparticles for intracellular lysozyme delivery

Intracellular delivery of native, active proteins is challenging due to the fragility of most proteins. Herein, a novel polymer/protein polyion complex (PIC) nanoparticle with core–shell structure was prepared. Carboxymethyl chitosan-grafted-terminal carboxyl group-poly(amidoamine) (CM-chitosan-PAMAM) dendrimers were synthesized by amidation and saponification reactions. ¹H NMR was used to characterize CM-chitosan-PAMAM dendrimers. The TEM images and results of lysozyme loading efficiency indicated that CM-chitosan-PAMAM dendrimers could self-assemble into core–shell nanoparticles, and lysozyme was efficiently encapsulated inside the core of CM-chitosan-PAMAM dendrimer nanoparticles. Activity of lysozyme was completely inhibited by CM-chitosan-PAMAM Dendrimers at physiological pH, whereas it was released into the medium and exhibited a significant enzymatic activity in an acidic intracellular environment. Moreover, the CM-chitosan-PAMAM dendrimer nanoparticles did not exhibit significant cytotoxicity in the range of concentrations below 3.16 mg/ml. The results indicated that these CM-chitosan-PAMAM dendrimers have excellent properties as highly potent and non-toxic intracellular protein carriers, which would create opportunities for novel applications in protein delivery.     

Interaction of multicomponent anionic liposomes with cationic pyridylphenylene dendrimer: Does the complex behavior depend on the liposome composition?

Dendrimers are individual macromolecular compounds having a great potential for biomedical application. The key step of the cell penetration by dendrimers is the interaction with lipid bilayer. Here, the interaction between cationic pyridylphenylene dendrimer of third generation (D₃⁵⁰⁺) and multicomponent liquid (CL/POPC), solid (CL/DPPC) and cholesterol-containing (CL/POPC/30% Chol) anionic liposomes was investigated by dynamic light scattering, fluorescence spectroscopy, conductometry, calorimetric studies and molecular dynamic (MD) simulations. Microelectrophoresis and MD simulations revealed the interaction is electrostatic and reversible with only part of pyridinium groups of dendrimers involved in binding with liposomes. The ability of dendrimer molecules to migrate between liposomes was discovered by the labeling liposomes with Rhodamine B. The phase state of the lipid membrane and the incorporation of cholesterol into the lipid bilayer were found to not affect the mechanism of the dendrimer - liposome complex formation. Rigid dendrimer adsorption on liposomal surface does not induce the formation of significant defects in the lipid membrane pave the way for possible biological application of pyridylphenylene dendrimers.     

CpFe-induced hexafunctionalization of hexamethylbenzene in [FeCp(η-C6Me6][PF6] using dendronized benzyl bromide derivatives at room temperature for the direct synthesis of metallodendrimers

Reaction of [FeCp(η⁶-C₆Me₆][PF₆] with KOH and benzylbromides parasubstituted with a functional dendron at room temperature selectively gives the hexasubstitution without decomplexation providing functional dendrimers, that were characterized by their molecular peaks in MALDI-TOF spectroscopy whereas, this chemistry was previously carried out at 60 °C which led to partial decomplexation and less selective reactions.