Resveratrol and Resveratrol-Loaded Galactosylated Liposomes: Anti-Adherence and Cell Wall Damage Effects on Staphylococcus aureus and MRSA

Antibiotic resistance due to bacterial biofilm formation is a major global health concern that makes the search for new therapeutic approaches an urgent need. In this context,, trans-resveratrol (RSV), a polyphenolic natural substance, seems to be a good candidate for preventing and eradicating biofilm-associated infections but its mechanism of action is poorly understood. In addition, RSV suffers from low bioavailability and chemical instability in the biological media that make its encapsulation in delivery systems necessary. In this work, the anti-biofilm activity of free RSV was investigated on Staphylococcus aureus and, to highlight the possible mechanism of action, we studied the anti-adherence activity and also the cell wall damage on a MRSA strain. Free RSV activity was compared to that of RSV loaded in liposomes, specifically neutral liposomes (L = DOPC/Cholesterol) and cationic liposomes (LG = DOPC/Chol/GLT1) characterized by a galactosylated amphiphile (GLT1) that promotes the interaction with bacteria. The results indicate that RSV loaded in LG has anti-adherence and anti-biofilm activity higher than free RSV. On the other side, free RSV has a higher bacterial-growth-inhibiting effect than encapsulated RSV and it can damage cell walls by creating pores; however, this effect can not prevent bacteria from growing again. This RSV ability may underlie its bacteriostatic activity.

Transport of cationic liposomes in a human blood brain barrier model: Role of the stereochemistry of the gemini amphiphile on liposome biological features

HYPOTHESIS

The positive charge on liposome surface is known to promote the crossing of the Blood brain barrier (BBB). However, when diastereomeric cationic gemini amphiphiles are among lipid membrane components, also the stereochemistry may affect the permeability of the vesicle across the BBB.

EXPERIMENTS

Liposomes featuring cationic diasteromeric gemini amphiphiles were formulated, characterized, and their interaction with cell culture models of BBB investigated.

FINDINGS

Liposomes featuring the gemini amphiphiles were internalized in a monolayer of brain microvascular endothelial cells derived from human induced pluripotent stem cells (hiPSC) through an energy dependent transport, internalization involving both clathrin- and caveolae-mediated endocytosis. On the same formulations, the permeability was also evaluated across a human derived in vitro BBB transport model. The permeability of liposomes featuring the gemini amphiphiles was significantly higher compared to that of neutral liposomes (DPPC/Cholesterol), that were not able to cross BBB. Most importantly, the permeability was influenced by the stereochemistry of the gemini and pegylation of these formulations did not result in a drastic reduction of the crossing ability. The in vitro iPSC-derived BBB models used in this work represent an important advancement in the drug discovery research of novel brain delivery strategies and therapeutics for central nervous system diseases.

Improvement of Lipoplexes With a Sialic Acid Mimetic to Target the C1858T PTPN22 Variant for Immunotherapy in Endocrine Autoimmunity

The C1858T variant of the protein tyrosine phosphatase N22 (PTPN22) gene is associated with pathophysiological phenotypes in several autoimmune conditions, namely, Type 1 diabetes and autoimmune thyroiditis. The R620W variant protein, encoded by C1858T, leads to a gain of function mutation with paradoxical reduced T cell activation. We previously exploited a novel personalized immunotherapeutic approach based on siRNA delivered by liposomes (lipoplexes, LiposiRNA) that selectively inhibit variant allele expression. In this manuscript, we functionalize lipoplexes carrying siRNA for variant C1858T with a high affinity ligand of Siglec-10 (Sig10L) coupled to lipids resulting in lipoplexes (LiposiRNA-Sig10L) that enhance delivery to Siglec-10 expressing immunocytes. LiposiRNA-Sig10L lipoplexes more efficiently downregulated variant C1858T PTPN22 mRNA in PBMC of heterozygous patients than LiposiRNA without Sig10L. Following TCR engagement, LiposiRNA-Sig10L more significantly restored IL-2 secretion, known to be paradoxically reduced than in wild type patients, than unfunctionalized LiposiRNA in PBMC of heterozygous T1D patients.

Design and Characterization of Myristoylated and Non-Myristoylated Peptides Effective against Candida spp. Clinical Isolates

The increasing resistance of fungi to antibiotics is a severe challenge in public health, and newly effective drugs are required. Promising potential medications are lipopeptides, linear antimicrobial peptides (AMPs) conjugated to a lipid tail, usually at the N-terminus. In this paper, we investigated the in vitro and in vivo antifungal activity of three short myristoylated and non-myristoylated peptides derived from a mutant of the AMP Chionodracine. We determined their interaction with anionic and zwitterionic membrane-mimicking vesicles and their structure during this interaction. We then investigated their cytotoxic and hemolytic activity against mammalian cells. Lipidated peptides showed a broad spectrum of activity against a relevant panel of pathogen fungi belonging to Candida spp., including the multidrug-resistant C. auris. The antifungal activity was also observed vs. biofilms of C. albicans, C. tropicalis, and C. auris. Finally, a pilot efficacy study was conducted on the in vivo model consisting of Galleria mellonella larvae. Treatment with the most-promising myristoylated peptide was effective in counteracting the infection from C. auris and C. albicans and the death of the larvae. Therefore, this myristoylated peptide is a potential candidate to develop antifungal agents against human fungal pathogens.

How stereochemistry of lipid components can affect lipid organization and the route of liposome internalization into cells

Though liposome-based drugs are in clinical use, the mechanism of cell internalization of liposomes is yet an object of controversy. The present experimental investigation, carried out on human glioblastoma cells, indicated different internalization routes for two diastereomeric liposomes. Molecular dynamics simulations of the lipid bilayers of the two formulations indicated that the different stereochemistry of a lipid component controls some parameters such as area per lipid molecule and fluidity of lipid membranes, surface potential and water organization at the lipid/water interface, all of which affect the interaction with biomolecules and cell components.

Synthesis and Characterization of Mitochondria-Targeted Triphenylphosphonium Bolaamphiphiles

In this chapter we describe: (1) the procedure for the synthesis of four single chain bolaamphiphiles, displaying chains of 12, 16, 20 and 30 methylene units and triphenylphosphonium moieties as headgroups (TPP1-TPP4); (2) the methods used to characterize TPP1-TPP4 spontaneous aggregation in aqueous solution. We illustrate the determination of Krafft point and cac by conductivity measurements and the procedures used to investigate dimensions, morphology, and stability by dynamic and dielectrophoretic laser light scattering, dialysis, transmission electron microscopy, and Raman spectroscopy measurements.

Structural Analysis and Design of Chionodracine-Derived Peptides Using Circular Dichroism and Molecular Dynamics Simulations

Antimicrobial peptides have been identified as one of the alternatives to the extensive use of common antibiotics as they show a broad spectrum of activity against human pathogens. Among these is Chionodracine (Cnd), a host-defense peptide isolated from the Antarctic icefish Chionodraco hamatus, which belongs to the family of Piscidins. Previously, we demonstrated that Cnd and its analogs display high antimicrobial activity against ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter species). Herein, we investigate the interactions with lipid membranes of Cnd and two analogs, Cnd-m3 and Cnd-m3a, showing enhanced potency. Using a combination of Circular Dichroism, fluorescence spectroscopy, and all-atom Molecular Dynamics (MD) simulations, we determined the structural basis for the different activity among these peptides. We show that all peptides are predominantly unstructured in water and fold, preferentially as α-helices, in the presence of lipid vesicles of various compositions. Through a series of MD simulations of 400 ns time scale, we show the effect of mutations on the structure and lipid interactions of Cnd and its analogs. By explaining the structural basis for the activity of these analogs, our findings provide structural templates to design minimalistic peptides for therapeutics.

Trematocine, a Novel Antimicrobial Peptide from the Antarctic Fish Trematomus bernacchii: Identification and Biological Activity

Antimicrobial peptides (AMPs) are short peptides active against a wide range of pathogens and, therefore, they are considered a useful alternative to conventional antibiotics. We have identified a new AMP in a transcriptome derived from the Antarctic fish Trematomus bernacchii. This peptide, named Trematocine, has been investigated for its expression both at the basal level and after in vivo immunization with an endemic Antarctic bacterium (Psychrobacter sp. TAD1). Results agree with the expected behavior of a fish innate immune component, therefore we decided to synthesize the putative mature sequence of Trematocine to determine the structure, the interaction with biological membranes, and the biological activity. We showed that Trematocine folds into a α-helical structure in the presence of both zwitterionic and anionic charged vesicles. We demonstrated that Trematocine has a highly specific interaction with anionic charged vesicles and that it can kill Gram-negative bacteria, possibly via a carpet like mechanism. Moreover, Trematocine showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against selected Gram-positive and Gram-negative bacteria similar to other AMPs isolated from Antarctic fishes. The peptide is a possible candidate for a new drug as it does not show any haemolytic or cytotoxic activity against mammalian cells at the concentration needed to kill the tested bacteria.

Effect of the Hydrophobic Tail of a Chiral Surfactant on the Chirality of Aggregates and on the Formation of Wormlike Micelles

The micellization of chiral enantiopure surfactants, dodecyl- N, N-dimethyl- N-( S)-(1-phenyl)ethylammonium bromide and hexadecyl- N, N-dimethyl- N-( S)-(1-phenyl)ethylammonium bromide, was investigated by circular dichroism spectroscopy and isothermal titration calorimetry. The formation of wormlike micelles (WLMs) upon the addition of sodium salicylate to the aqueous solutions of the surfactant was observed only in the case of hexadecyl- N, N-dimethyl- N-( S)-(1-phenyl)ethylammonium bromide. The presence of WLMs was assessed by cryogenic transmission electron microscopy, rheology, and isothermal titration calorimetry experiments, and their supramolecular chirality was investigated by circular dichroism spectroscopy. Depending on the length of the hydrophobic tail, molecular chirality is transferred into a different chiral supramolecular trait. Our findings demonstrate that hydrophobic interactions by controlling the organization and functions of self-assemblies also control the transcription of the chiral information from molecules to complex supramolecular systems.

Targeting Serotonin 2A and Adrenergic α1 Receptors for Ocular Antihypertensive Agents: Discovery of 3,4-Dihydropyrazino[1,2-b]indazol-1(2H)-one Derivatives

Glaucoma affects millions of people worldwide and causes optic nerve damage and blindness. The elevation of the intraocular pressure (IOP) is the main risk factor associated with this pathology, and decreasing IOP is the key therapeutic target of current pharmacological treatments. As potential ocular hypotensive agents, we studied compounds that act on two receptors (serotonin 2A and adrenergic α₁ ) linked to the regulation of aqueous humour dynamics. Herein we describe the design, synthesis, and pharmacological profiling of a series of novel bicyclic and tricyclic N2-alkyl-indazole-amide derivatives. This study identified a 3,4-dihydropyrazino[1,2-b]indazol-1(2H)-one derivative with potent serotonin 2A receptor antagonism, >100-fold selectivity over other serotonin subtype receptors, and high affinity for the α₁ receptor. Moreover, upon local administration, this compound showed superior ocular hypotensive action in vivo relative to the clinically used reference compound timolol.

Design and characterization of chionodracine-derived antimicrobial peptides with enhanced activity against drug-resistant human pathogens

Design of new chionodracine-derived peptides with potent activity against drug-resistant human pathogens.

The aggregation of amphiphilic (L)-proline-porphyrin derivatives in ethanol-water mixtures promoted by chiral anionic surfactants

The use of chiral surfactants results in a powerful tool to form chiral assemblies of (L)proline-functionalized porphyrin derivatives in EtOH/H[Formula: see text]O exploiting hydrophobic effect. The formation of chiral heteroaggregated species strictly depends both on the configuration of the chiral center of the surfactant and on its concentration, opening the possibility to tune the supramolecular asymmetry of the final structures.

Proof of the Structure of the Stemodia chilensis Tetracyclic Diterpenoid (+)-19-Acetoxystemodan-12-ol by Synthesis from (+)-Podocarpic Acid: X-ray Structure Determination of a Key Intermediate

The first synthesis of (+)-19-acetoxystemodan-12-ol (1), a stemodane diterpenoid isolated from Stemodia chilensis, is described. The structure was supported by an X-ray crystallographic analysis of intermediate (+)-9a, which confirmed the proposed structure and excluded the structure of (-)-19-hydroxystemod-12-ene as a possible candidate for the Chilean Calceolaria diterpenoid to which the (-)-19-hydroxystemar-13-ene structure (9b) had been erroneously assigned.

Inclusion of new 5-fluorouracil amphiphilic derivatives in liposome formulation for cancer treatment

Liposomes containing novel 5-fluorouracil derivatives differing in the length of their polyoxyethylenic spacer were shown active against colorectal tumor cells.

Surfactant-induced chirality on reluctant aggregates of a chiral amphiphilic cationic (l)-proline–Zn(ii)porphyrin conjugate in water

The aggregation of an amphiphilic chiral Zn(ii)porphyrin derivative occurs in aqueous solutions of chiral surfactants with highly specific molecular recognition.

A combined theoretical and experimental study of solid octyl and decylammonium chlorides and of their aqueous solutions

The analysis of the thermal behavior of octyl- (OAC) and decylammonium chloride (DAC) has provided relevant new information. OAC shows a polymorphic phase transition that starts at 308 K and is completed at 313 K, between a monoclinic and a tetragonal structure, which belongs to a space group different from what was observed for other alkylammonium chlorides. At the melting temperature (463 K), the growing of a strong first sharp diffraction peak (FSDP) occurring at a d-spacing of ca. 21.0 Å was observed. DAC is characterized by two phase transitions at 318 (T(d1)) and 323 K (T(d2)). At T(d1), the LT polymorph coexists with a new-formed phase. At T(d2) the LT polymorph is replaced by a further polymorphic modification of DAC that becomes the only one at 328 K. This second phase transition signals the occurrence of a phase, closely related to the LT polymorph of HeAC, that crystallizes in the tetragonal crystal system a = ca. 5.00 Å and c = ca. 28.5 Å, P4/nmm space group. DAC melting starts at 458 K and is accompanied, as in the case of OAC, by the growing of a strong FSDP at a d-spacing of ca. 24.8 Å. A parallel DSC study confirmed the above-mentioned transitions. In addition, the structural properties of OAC/water and DAC/water mixtures were studied using an integrated approach, which combines X-ray diffraction and molecular dynamics (MD) techniques. A very good agreement between theoretical and experimental diffraction patterns has been obtained for both investigated mixtures. A thorough analysis of the MD trajectories shows that strong anion-water interactions are present in the mixtures, where Cl(-) forms a rather unstructured first hydration shell of water molecules bound to the anion in a linear Cl···H-O configuration. Moreover, cations and anions were found to interact with each other, and to form "solvent-shared ion pairs", in which one or more water molecules are shared between Cl(-) and the alkylammonium cation.

A combined theoretical and experimental study of solid octyl and decylammonium chlorides and of their aqueous solutions

The analysis of the thermal behavior of octyl- (OAC) and decylammonium chloride (DAC) has provided relevant new information. OAC shows a polymorphic phase transition that starts at 308 K and is completed at 313 K, between a monoclinic and a tetragonal structure, which belongs to a space group different from what was observed for other alkylammonium chlorides. At the melting temperature (463 K), the growing of a strong first sharp diffraction peak (FSDP) occurring at a d-spacing of ca. 21.0 Å was observed. DAC is characterized by two phase transitions at 318 (T(d1)) and 323 K (T(d2)). At T(d1), the LT polymorph coexists with a new-formed phase. At T(d2) the LT polymorph is replaced by a further polymorphic modification of DAC that becomes the only one at 328 K. This second phase transition signals the occurrence of a phase, closely related to the LT polymorph of HeAC, that crystallizes in the tetragonal crystal system a = ca. 5.00 Å and c = ca. 28.5 Å, P4/nmm space group. DAC melting starts at 458 K and is accompanied, as in the case of OAC, by the growing of a strong FSDP at a d-spacing of ca. 24.8 Å. A parallel DSC study confirmed the above-mentioned transitions. In addition, the structural properties of OAC/water and DAC/water mixtures were studied using an integrated approach, which combines X-ray diffraction and molecular dynamics (MD) techniques. A very good agreement between theoretical and experimental diffraction patterns has been obtained for both investigated mixtures. A thorough analysis of the MD trajectories shows that strong anion-water interactions are present in the mixtures, where Cl(-) forms a rather unstructured first hydration shell of water molecules bound to the anion in a linear Cl···H-O configuration. Moreover, cations and anions were found to interact with each other, and to form "solvent-shared ion pairs", in which one or more water molecules are shared between Cl(-) and the alkylammonium cation.

Regio- and diastereoselective synthesis and X-ray structure determination of (+)-2-deoxyoryzalexin S from (+)-podocarpic acid. Structural nonidentity with its nominal natural isolated enantiomer

(+)-2-Deoxyoryzalexin S (1), the nominal enantiomer of a diterpenoid isolated in Chile from Calceolaria species, was regio- and diastereoselectively synthesized from (+)-podocarpic acid. (+)-2-Deoxyoryzalexin S (1) was characterized also as its acetyl derivative, (+)-2, whose structure was confirmed by X-ray crystallographic analysis. Surprisingly, comparison of the data recorded for (+)-1 and (+)-2 and those reported in the literature for the Calceolaria isolated diterpenoid 1 and its derivative (-)-2 showed some differences, suggesting that the latter do not possess the proposed structures.

Construction and complexation studies of some self-assembled diporphyrin receptors

A ternary self-assembling system consisting of two Zn(II) carboxyphenylporphyrins and an aliphatic diamine linker was constructed via hydrogen bonding and Coulombic interactions between the porphyrin carboxylic moieties and the amino groups of the spacer. The properties of the resulting structures, in terms of binding of several aromatic diamine guests are described. The stability and geometry of the final host-guest supramolecular architecture (i.e. cyclic or linear array) can be modulated by the nature of the spacer.

Diastereoselective total synthesis of (+)-13-stemarene by fourth generation methods: a formal total synthesis of (+)-18-deoxystemarin

The problem of constructing diastereoselectively the C/D ring system of stemarane diterpenes from a bicyclo[2.2.2]octane intermediate was solved resulting in very simple synthesis of (+)-13-stemarene 1. The obtaining of the latter represents also a formal synthesis of (+)-18-deoxystemarin 2. In the key step, the epimeric mixture 10, dissolved in toluene, was converted by the action of TsOH into (+)-stemar-13-en-15-one 28.

Spectroscopic characterization of 6-hydroxy and 1-methyl-6-hydroxybicyclo[2.2.2]octan-2-one ethylene acetals and ethylene dithioacetals

6-endo- and 6-exo-Hydroxybicyclo[2.2.2]octan-2-one and 1-methyl-6-endo- and 6-exo-hydroxybicyclo[2.2.2]octan-2-one ethylene acetals and ethylene dithioacetals 1-4 have been characterized by 1D and 2D NMR methods.

pH Variation as the Switch for Chiral Recognition in a Biomembrane Model

Chiral recognition was observed in a biomembrane model. Micellar aggregates formed by N-dodecyl-l-proline were, in fact, able to convert the racemic mixture of a biphenyl derivative into an enantiomerically enriched mixture. The extent of deracemization was established by HPLC on a chiral stationary phase and, in some conditions, resulted in the highest ever observed in these systems. The configuration of the exceeding enantiomer and the extent of enantiomeric enrichment depend on the medium pH. In fact, the exceeding enantiomer has the same configuration at pH 1 and 7, being more abundant at pH 7, whereas it has the opposite configuration at pH 13. The changes in the stereochemical bias are reversible.

Elucidation of the isomeric domains formed by sodium N-dodecanoyl-l-prolinate

Investigations aimed at clarifying the nature of geometrical domains of amidic sodium N-dodecanoyl-l-prolinate are reported. NMR investigations on the association of aromatic solutes with the aggregates formed by the amidic surfactant in water show the selective binding of some solutes to the Z domains. Fluorescence quenching experiments allowed us to measure the aggregation number of the aggregates. SAXS experiments gave the average size and structural features of the aggregates. A NMR ROESY experiment evidenced the mosaic-like nature of the domains inside the same aggregate.

A New Simple Procedure for Discriminating between Deracemization and an Induced CD Effect in Chiral Recognition Experiments on Atropoisomers

A CD band in chiral recognition experiments on racemic stereolabile compounds can be ascribed either to deracemization or to a solely induced CD effect. A procedure is presented that allows one to discriminate positively between the two phenomena. The procedure, based on CD spectroscopy, was used in experiments on racemic biphenylic derivatives in aggregates formed by enantiopure surfactants. In addition to demonstrating a deracemization event, the procedure allowed us to measure the enantiomeric excess.

Interaction of a chirally functionalised porphyrin derivative with chiral micellar aggregates

The functionalisation of a porphyrin derivative with a chiral functionality results in a selective interaction with chiral micellar aggregates.

Deracemization of an axially chiral biphenylic derivative as a tool for investigating chiral recognition in self-assemblies

Two diastereomeric cationic surfactants derived from L-proline, in which the second chiral center is a quaternary nitrogen, have been separated and fully characterized. The recognition properties of the aggregates formed by the two diastereomeric surfactants have been investigated by circular dichroism and (1)H NMR through deracemization of racemic 2-carboxy-2'-dodecyloxy-6-nitrobiphenyl.