Fine-Tuned "Click" Functionalization of PAMAM Dendrimers with a Linear Fluorinated Guanidino Linker: Synthesis, Characterization, and Applications.

This study presents the synthesis, characterization, and application of multifunctional PAMAM G2 and G4 dendrimers decorated with a linear fluorinated guanidino linker designed to improve gene delivery efficiency while minimizing cytotoxicity. For the first time, we were able to fine-tune the degree of grafting (DG) during the functionalization process through efficient "click" Michael addition, achieving the synthesis of a collection of six PAMAM conjugates that showed a significant enhancement in transfection efficiency (TE), surpassing the performance of traditional nonviral vectors. The incorporation of fluorinated moieties not only facilitated better deoxyribonucleic acid (DNA) condensation and TE but also introduced potential applications in F magnetic resonance imaging thanks to the sharp and intense fluorine nuclear magnetic resonance signals and favorable relaxation parameters.

Dual Antibiotic Approach: Synthesis and Antibacterial Activity of Antibiotic-Antimicrobial Peptide Conjugates.

In recent years, bacterial resistance to conventional antibiotics has become a major concern in the medical field. The global misuse of antibiotics in clinics, personal use, and agriculture has accelerated this resistance, making infections increasingly difficult to treat and rendering new antibiotics ineffective more quickly. Finding new antibiotics is challenging due to the complexity of bacterial mechanisms, high costs and low financial incentives for the development of new molecular scaffolds, and stringent regulatory requirements.

Fluorinated PAMAM-Arginine Carrier Prodrugs for pH-Sensitive Sustained Ibuprofen Delivery.

Objective: The development of an efficient, multifunctional drug delivery system overcoming different obstacles generally associated with drug formulations, including the poor accumulation of the active principle in the target site and its sustained release for prolonged time.

Methods: Our study proposes the development of a fluorinated poly(amidoamine) (PAMAM) carrier prodrug combining drug release boosted in alkaline environments with a possible implementation in F MRI applications. In particular, we functionalized the terminal primary amines of PAMAM G2 and G4 through an ad hoc designed fluorinated ibuprofen-arginine Michael acceptor to obtain multifunctional ibuprofen-PAMAM-Arg conjugates.

Turn-Mimic Hydantoin-Based Loops Constructed by a Sequential Multicomponent Reaction.

A collection of peptidomimetics characterized by having an aspartic acid motif embedded in a rigid hydantoin heterocycle are synthesized through a sequential multicomponent domino process followed by standard regioselective deprotection/coupling reactions based on acid-base liquid/liquid purification protocols. H nuclear magnetic resonance experiments, molecular modeling, and X-ray analysis showed that the resulting hydantoin-based loops I (in particular) and II (to a lesser extent) can be considered novel β-turn inducer motifs being able to project two peptide-like strands in a U-shaped conformation driven by the formation of intermolecular hydrogen bonds.

Synthesis of amphiphilic hydantoin-based universal peptidomimetics as antibiotic agents.

Three model hydantoin-based universal peptidomimetics were designed and synthetized. Their preferred amphiphilic β-turn conformation was assessed using molecular modeling and NMR experiments, and their antibacterial activity was tested against Gram-positive and Gram-negative bacteria strains, which demonstrated that these compounds could be a captivating class of antibiotics to fight emergent drug resistance.

Selectively Fluorinated PAMAM-Arginine Conjugates as Gene Delivery Vectors.

Polyamidoamine (PAMAM) dendrimers are among the most studied cationic polymers as non-viral gene delivery vectors. However, an "ideal" PAMAM-based gene delivery vector is still missing due to the high manufacturing costs and non-negligible cytotoxicity associated with the use of high-generation dendrimers, whereas low-generation dendrimers are far from displaying efficient gene transfection. In order to cover this gap in the literature, in this study, we propose the functionalization of the outer primary amines of PAMAM G2 and PAMAM G4 with building blocks bearing fluorinated moieties along with a guanidino functional group.

Synthesis and Conformational Analysis of Hydantoin-Based Universal Peptidomimetics.

The synthesis of a collection of enantiomerically pure, systematically substituted hydantoins as structural privileged universal mimetic scaffolds is presented. It relies on a chemoselective condensation/cyclization domino process between isocyanates of quaternary or unsubstituted α-amino esters and -alkyl aspartic acid diesters followed by standard hydrolysis/coupling reactions with amines, using liquid-liquid acid/base extraction protocols for the purification of the intermediates. Besides the nature of the α carbon on the isocyanate moiety, either a quaternary carbon or a more flexible methylene group, conformational studies (molecular modeling), in solution (NMR, circular dichroism (CD), Fourier transform infrared (FTIR)), and in solid state (X-ray) showed that the presented hydantoin-based peptidomimetics are able to project their substituents in positions superimposable to the side chains of common protein secondary structures such as α-helix and β-turn, being the open α-helix conformation slightly favorable according to molecular modeling, while the closed β-turn conformation preferred in solution and in solid state.

Enantioseparation of chiral (benzylsulfinyl)benzamide sulfoxides by capillary electrophoresis using cyclodextrins as chiral selectors.

Sulfur as a stereogenic center can be found in synthetic compounds and natural products. The current study evaluated the enantioseparation of 16 chiral (benzylsulfinyl)benzamide compounds by capillary electrophoresis using charged cyclodextrins (CDs) as chiral selectors in 50 mM sodium acetate buffer, pH 5.5.

Guanidinoneomycin-maleimide molecular transporter: synthesis, chemistry and cellular uptake.

Guanidinoglycosides are a class of non-cytotoxic molecular transporters capable of delivering high molecular weight bioactive cargos into cells at low nanomolar concentrations. Efficient bioconjugation with guanidinoglycosides has been previously demonstrated by utilizing a guanidinoneomycin decorated with a reactive but also unstable N-hydroxysuccinimmide ester-containing linker. Herein we report the synthesis, chemistry, and application of a new, stable guanidinoneomycin derivative armed with a highly specific maleimide moiety which allows for thiol-maleimide click chemistry, a highly popular bioconjugation strategy, widening the field of application of these intriguing and useful delivery vehicles.

Solid-Phase Synthesis of Gly-Ψ[CH(CF)NH]-Peptides.

The solid-phase synthesis of Gly-Ψ[CH(CF)NH]-peptides is presented. In order to achieve this goal, the synthesis of Gly-Ψ[CH(CF)NH]-dipeptides having the C-terminus unprotected, the N-terminus protected as Fmoc- or Teoc-, and possibly side chain functionalities protected with acid-labile protecting groups has been developed. A selected small library of six peptidomimetics, encompassing analogues of biological relevant peptides, have been obtained in high purity.

Synthesis of Orthogonally Protected Labionin.

We report the first synthesis of the complex amino acid labionin in a fully orthogonally protected and stereopure form. The structure-which incorporates five orthogonal protecting groups and three stereogenic centers-was assembled using two key synthetic steps: (1) a thia-Michael addition for installing the thioether bridge; (2) an electrophilic azidation for creating the central quaternary α-amino acid carbon in a stereochemically pure form. This work is expected to enable the solid phase synthesis of both natural and synthetic analogues labyrinthopeptins.

Multifunctional Neomycin-Triazine-Based Cationic Lipids for Gene Delivery with Antibacterial Properties.

Cationic lipids (CLs) have gained significant attention among nonviral gene delivery vectors due to their ease of synthesis and functionalization with multivalent moieties. In particular, there is an increasing request for multifunctional CLs having gene delivery capacity and antibacterial activity. Herein, we describe the design and synthesis of a novel class of aminoglycoside (AG)-based multifunctional vectors with high transfection efficiency and noticeable antibacterial properties.

Aminoglycosides: From Antibiotics to Building Blocks for the Synthesis and Development of Gene Delivery Vehicles.

Aminoglycosides are a class of naturally occurring and semi synthetic antibiotics that have been used for a long time in fighting bacterial infections. Due to acquired antibiotic resistance and inherent toxicity, aminoglycosides have experienced a decrease in interest over time. However, in the last decade, we are seeing a renaissance of aminoglycosides thanks to a better understanding of their chemistry and mode of action, which had led to new trends of application.

Potential and current limitations of superficially porous silica as a carrier for polysaccharide-based chiral selectors in separation of enantiomers in high-performance liquid chromatography.

In this study superficially porous silica particles with a nominal pore size of 450 Å and average particle size of 2.6 micrometers was compared to fully porous silica particles with nominal particle size 3 micrometers and nominal pore size 1000 A as carriers for a polysaccharide based chiral selector for the separation of enantiomers in high-performance liquid chromatography. In addition, the effects of chiral selector loading onto the silica support and of column internal dimeter in the case of both, superficially porous and totally porous silica, as well as of the pore size of superficially porous silica on column performance were studied.

Multicomponent Approach to Libraries of Substituted Dihydroorotic Acid Amides.

A process featuring a sequential multicomponent reaction followed by a regioselective postcyclization strategy was implemented for the facile synthesis of ,'-disubstituted dihydroorotic acid amides under mild conditions. We obtained, for the first time, a library of 29 derivatives, encompassing 19 -substituted--dihydroorotyl-4-aminophenylalanine derivatives, a key residue of gonadotropin-releasing hormone antagonist Degarelix. The corresponding products were prepared from easily accessible starting materials in good to excellent yields with broad substrate scope.

Separation of enantiomers of chiral sulfoxides in high-performance liquid chromatography with cellulose-based chiral selectors using acetonitrile and acetonitrile-water mixtures as mobile phases.

The separation of 14 chiral sulfoxides was systematically studied on 12 cellulose-based chiral columns in acetonitrile and acetonitrile-water mobile phases. Out of all monosubstituted methylphenylcarbamates of cellulose the one having a methyl moiety in position 3 showed more universal chiral resolving ability compared to 2- and 4-substituted derivatives. Out of disubstituted phenylcarbamates of cellulose the ones with methyl substituents showed higher enantiomer resolving ability compared to chloro-substituted ones and substitution in positions 3 of the phenyl moiety was clearly advantageous.

Design and synthesis of biologically active cationic amphiphiles built on the calix[4]arene scaffold.

A promising strategy to design safer and more effective cationic lipids for gene delivery with inherent antibacterial properties is to covalently tether a lipophilic moiety with oligomeric aminoglycosides (AGs), a large family of Gram-negative-active antibiotics. Herein, we reported the development of a new class of multicationic-head AG-based amphiphiles built on the tetramino-tetrahexyloxycalix[4]arene (4A4Hex-calix-calix[4]) scaffold. Three different conjugates, namely 4A4Hex-calix-calix[4]-neomycin, -neamine, and -paromomycin, were synthesized and characterized.

Application of cellulose 3,5-dichlorophenylcarbamate covalently immobilized on superficially porous silica for the separation of enantiomers in high-performance liquid chromatography.

Our earlier studies have demonstrated the applicability of polysaccharide-based chiral selectors in combination with superficially porous (or core-shell) silica (SPS) particles for the preparation of highly efficient chiral stationary phases (CSP). In earlier studies, CSPs were prepared by coating (adsorption) of the chiral selector onto the surface of silica. In this study we report for the first time the CSP obtained by covalent immobilization of a chiral selector onto the surface of SPS particles.

Separation of enantiomers of chiral sulfoxides in high-performance liquid chromatography with cellulose-based chiral selectors using methanol and methanol-water mixtures as mobile phases.

The interplay between structural details of chiral analytes and selectors in the separation of 14 chiral sulfoxides was systematically studied on 18 different polysaccharide-based chiral columns. Retention and enantioselectivity of a set of chiral sulfoxides were of primary interest. Several of chiral columns studied exhibited quite powerful chiral recognition ability in pure methanol.

Separation of enantiomers of selected chiral sulfoxides with cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral columns in high-performance liquid chromatography with very high separation factor.

The present study reports successful separations of enantiomers of selected chiral sulfoxides with very high separation factor in high-performance liquid chromatography by using chiral columns prepared with the chiral selector cellulose tris(4-chloro-3-methylphenylcarbamate). High separation factors were observed in polar organic, as well as in hydrocarbon-alcohol-type mobile phases. The key structural components of the solute for obtaining high chiral recognition are discussed as well as thermodynamic quantities of analyte adsorption on the chiral stationary phase were determined.

Design, synthesis, and conformational analysis of 3-cyclo-butylcarbamoyl hydantoins as novel hydrogen bond driven universal peptidomimetics.

A collection of systematically substituted 3-cyclo-butylcarbamoyl hydantoins was synthesized by a regioselective multicomponent domino process followed by easy coupling reactions. Calculations, NMR studies and X-ray analysis show that these scaffolds are able to project their side chains similar to common secondary structures, such as the α-helix and β-turn, with favourable enthalpic and entropic profiles.

Enantioseparation of novel chiral sulfoxides on chlorinated polysaccharide stationary phases in supercritical fluid chromatography.

Asymmetric sulfoxides is a particular case of chirality that may be found in natural as well as synthetic products. Twenty-four original molecules containing a sulfur atom as a centre of chirality were analyzed in supercritical fluid chromatography on seven polysaccharide-based chiral stationary phases (CSP) with carbon dioxide - methanol mobile phases. While all the tested CSP provided enantioseparation for a large part of the racemates, chlorinated cellulosic phases proved to be both highly retentive and highly enantioselective towards these species.

An attempt for fast separation of enantiomers in nano-liquid chromatography and capillary electrochromatography.

In the present study, an attempt was made to achieve separation of enantiomers within a minute in nano-LC and CEC. In order to achieve this goal several parameters were optimized from the viewpoint of the property of chiral analytes, concentration of the chiral selector in the packing material, capillary dimensions, and separation mode. The enantiomers of several of the applied chiral sulfoxides could be resolved with the analysis time <1 min.

Dendrimeric Guanidinoneomycin for Cellular Delivery of Bio-macromolecules.

We present the synthesis of polymeric amino- and guanidinoglycosides prepared by tethering neomycin and guanidinoneomycin to PAMAM dendrimers of generations 2 and 4. The ability of these conjugates to promote cellular uptake of high-molecular-weight cargo is discussed, together with their cytotoxicity and mechanisms of entry. We demonstrate that the presence of multiple guanidinoneomycin carriers on the PAMAM surface plays an important role in promoting cellular uptake of the dendrimers, maintaining the heparan sulfate specificity and negligible cytotoxicity typical of monomeric guanidinoglycoside molecular transporters.