Luisa Giansanti

Recognition of concanavalin A by cationic glucosylated liposomes.

The specificity of carbohydrate-lectin interaction has been reported as an attractive strategy for drug delivery in cancer therapy because of the high levels of lectins in several human malignancies. A novel cationic glucosylated amphiphile was therefore synthesized, as a model system, to attribute specificity toward d-glucose receptors to liposome formulations. Fluorescence experiments demonstrated that the monomeric glucosylated amphiphile is capable of interacting with fluorescently labeled concanavalin A, a D-glucose specific plant lectin. The interaction of concanavalin A with liposomes composed of a phospholipid and the glucosylated amphiphile was demonstrated by agglutination observed by optical density and dynamic laser light scattering measurements, thus paving the way to the preparation of other glycosilated amphiphiles differing for the length of polyoxyethylenic spacer, the sugar moieties, and/or the length of the hydrophobic chain.

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

Correction for ‘Inclusion of new 5-fluorouracil amphiphilic derivatives in liposome formulation for cancer treatment’ by M. Petaccia et al., Med. Chem. Commun., 2015, 6, 1639–1642.

Role of the hydrophilic spacer of glucosylated amphiphiles included in liposome formulations in the recognition of Concanavalin A.

The functionalization of liposomes with glycosylated amphiphiles is an optimal strategy for targeted drug delivery, leading to enhanced efficacy as well as to reduced side effects of drugs. In fact, the presence of natural or synthetic glycolipids in vesicle formulations might increase their specificity toward lectins, a class of non-enzymatic sugar-binding proteins involved in cellular recognition and adhesion. The capability of a new glucosylated synthetic amphiphile to interact with Concanavalin A (Con A), a plant lectin used as model system, was investigated by a synergic experimental and computational approach, both as pure component and in formulation with a natural phospholipid. The comparison of the affinity with Con A of the new glucosylated amphiphile with respect to that of a previously described structural analogue demonstrates that the hydrophilic spacer length controls the exposure of the glucose residue on liposome surface, and consequently the recognition by the lectin.

Influence of the state of phase of lipid bilayer on the exposure of glucose residues on the surface of liposomes

The presence of carbohydrate-binding proteins (i.e. lectins) on the surface of various bacterial strains and their overexpression in some tumor tissues makes the use of glycosylated liposomes a promising approach for the specific drug delivery in antibacterial and anti-cancer therapies. However, the functionalization of liposome surface with sugar moieties by glycosylated amphiphiles does not ensure the binding of sugar-coated vesicles with lectins. In fact, the composition and properties of lipid bilayer play a pivotal role in the exposure of sugar residues and in the interaction with lectins. The influence of the length of the hydrophilic spacer that links the sugar to liposome surface and of the presence of saturated or unsaturated phospholipids in the lipid bilayer on the ability of glucosylated liposomes to interact with a model lectin, Concanavalin A, was investigated. Our results demonstrate that both the chain length and the prensece of unsaturation, parameters that strongly affect the fluidity of the lipid bilayer, affect agglutination. In particular, agglutination is favored when liposomes are in the gel phase within a defined range of temperature. Moreover, the obtained results confirm that the length of the PEG spacer, that influences both lipid organization and the exposure of sugar moieties to the bulk, plays a crucial role in liposome/lectin interaction.

Achiral Dye/Surfactant Heteroaggregates for Chiral Sensing of Phosphocholines

An investigation, based on absorption and circular dichroism spectroscopy, was carried out on assemblies formed in water upon the interaction of heteroaggregates, composed of dyes (Congo Red or Evans Blue) and cetyltrimethylammonium bromide (CTAB), with four enantiopure phopshocholines (DMPC, DPPC, DOPC, and POPC) characterized by the same polar head and different hydrophobic tails. The results show that the nature of the lipid as well as the concentration ratios influence sensitively the absorption and chiroptical properties of the supramolecular structure. Intriguingly, the transfer of chirality from the lipid to the assembly may be triggered or not, depending on the nature of the lipid hydrophobic chain. These findings confirm the fundamental role of hydrophobic interactions in the transcription of chirality from molecules to complex architectures.

Synthesis, characterization and inclusion into liposomes of a new cationic pyrenyl amphiphile

The aggregation properties of a new cationic fluorescent amphiphile tagged on the hydrophobic tail with a pyrene moiety and bearing two hydroxyethyl functionalities on the polar headgroup were investigated by fluorescence experiments as pure components or in mixed liposomes containing an unsaturated phospholipid, 1,2-dioleoyl-sn-glycero-3-phosphocholine, at different molar ratios. The obtained results put in evidence that the conformation and the miscibility of the lipids in the aggregates strongly influence the excimer/monomer ratio. Mixed monolayers at the same composition were investigated by Langmuir compression isotherms to deepen the understanding of lipid organization and miscibility, both in the polar and in the hydrophobic regions. The presence of two hydroxyethyl functionalities on the polar headgroup of the newly synthesized amphiphile exerts a shielding effect of the charge of the amphiphile increasing the compressibility of lipid components in contrast with the disturbing effect of the unsaturated acyl chains of the phospholipid.

Fluorescence and computational studies of thymidine phosphorylase affinity toward lipidated 5-FU derivatives

Thymidine phosphorylase (TP) is an enzyme that is up-regulated in a wide variety of solid tumors, including breast and colorectal cancers. It is involved in tumor growth and metastasis, for this reason it is one of the key enzyme to be inhibited, in an attempt to prevent tumor proliferation. However, it also plays an active role in cancer treatment, through its contribution in the conversion of the anti-cancer drug 5-fluorouracil (5-FU) to an irreversible inhibitor of thymidylate synthase (TS), responsible of the inhibition of the DNA synthesis. In this work, the intrinsic TP fluorescence has been investigated for the first time and exploited to study TP binding affinity for the unsubstituted 5-FU and for two 5-FU derivatives, designed to expose this molecule on liposomal membranes. These molecules were obtained by functionalizing the nitrogen atom with a chain consisting of six (1) or seven (2) units of glycol, linked to an alkyl moiety of 12 carbon atoms. Derivatives (1) and (2) exhibited an affinity for TP in the micromolar range, 10 times higher than the parent compound, irrespective of the length of the polyoxyethylenic spacer. This high affinity was maintained also when the compounds were anchored in liposomal membranes. Experimental results were supported by molecular dynamics simulations and docking calculations, supporting a feasible application of the designed supramolecular lipid structure in selective targeting of TP, to be potentially used as a drug delivery system or sensor device.

Transcription of chirality from molecules to complex systems: the role of hydrophobic interactions

An absorption and circular dichroism spectroscopies investigation was carried out on the heteroaggregates formed in water upon the interaction of Chicago Sky Blue with four different cationic surfactants derived from ephedrine and pseudoephedrine and featuring hydrophobic tails of different length. The chirooptical features of the heteroaggregates indicate that hydrophobic interactions control the transcription of the chiral information from the surfactant to the supramolecular architectures they form with the dye. In fact, surfactants characterised by the same stereochemistry and by different length of the hydrophobic tails mediate the selection of the enantiomers of the same chiral topological arrangement.

Glucosylated pH-sensitive liposomes as potential drug delivery systems

The inclusion of pH-sensitive components in liposome formulations can allow a more controlled and efficient release in response to low pH typical of some pathological tissues and/or subcellular compartments. On the other hand decorating the surface of liposomes with sugar moieties attributes to lipid vesicles specificity toward lectins, sugar-binding proteins overexpressed in many tumor tissues. A novel multifunctional pH-sensitive glucosylated amphiphile was synthesized and characterized as pure aggregate component and in mixtures with a natural phospholipid. The comparison of the properties of the new glucosylated amphiphile with respect to those of a previously described cationic structural analogue demonstrates that the pH-sensitivity can strongly affect drug release, lipid organization, as well as the exposure of the glucose residues on liposome surface and their ability to interact with Concanavalin A, a plant lectin used as model system.