Biophysics and protein corona analysis of Janus cyclodextrin-DNA nanocomplexes. Efficient cellular transfection on cancer cells.

The self-assembling processes underlining the capabilities of facially differentiated ("Janus") polycationic amphiphilic cyclodextrins (paCDs) as non-viral gene nanocarriers have been investigated by a pluridisciplinary approach. Three representative Janus paCDs bearing a common tetradecahexanoyl multitail domain at the secondary face and differing in the topology of the cluster of amino groups at the primary side were selected for this study. All of them compact pEGFP-C3 plasmid DNA and promote transfection in HeLa and MCF-7 cells, both in absence and in presence of human serum. The electrochemical and structural characteristics of the paCD-pDNA complexes (CDplexes) have been studied by using zeta potential, DLS, SAXS, and cryo-TEM. paCDs and pDNA, when assembled in CDplexes, render effective charges that are lower than the nominal ones. The CDplexes show a self-assembling pattern corresponding to multilamellar lyotropic liquid crystal phases, characterized by a lamellar stacking of bilayers of the CD-based vectors with anionic pDNA sandwiched among them. When exposed to human serum, either in the absence or in the presence of pDNA, the surface of the cationic CD-based vector becomes coated by a protein corona (PC) whose composition has been analyzed by nanoLC-MS/MS. Some of the CDplexes herein studied showed moderate-to-high transfection levels in HeLa and MCF-7 cancer cells combined with moderate-to-high cell viabilities, as determined by FACS and MTT reduction assays. The ensemble of data provides a detail picture of the paCD-pDNA-PC association processes and a rational base to exploit the protein corona for targeted gene delivery on future in vivo applications.

Trehalose-based Janus cyclooligosaccharides: the "Click" synthesis and DNA-directed assembly into pH-sensitive transfectious nanoparticles.

The convergent preparation of Janus molecular nanoparticles by thiourea-"clicking" of α,α'-trehalose halves has been implemented; the strategy allows access to macrocyclic derivatives with seggregated cationic and lipophilic domains that in the presence of DNA undergo pH-dependent self-assembly into lamellar superstructures, as established by electrochemical, structural (SAXS), microscopical (TEM) and computational techniques, that mediate transfection in vitro and in vivo.

Surface and bulk properties of aqueous decyltrimethylammonium bromide-hexadecyltrimethylammonium bromide mixed system.

The aqueous mixed system decyltrimethylammonium bromide (C(10)TAB)-hexadecyltrimethylammonium bromide (C(16)TAB) was studied by conductivity, ion-selective electrodes, surface tension, and fluorescence spectroscopy techniques. The mixture critical micelle concentration, cmc(*), aggregation number, N( *), and micelle molar conductivity, Lambda(M)(cmc), showed that the system aggregation is strongly nonideal. Both cmc(*) and N( *) results were analyzed with two different procedures: (i) the regular solution theory on mixed micelles or Rubingh's theory, and (ii) by the determination of the partial critical micelle concentration of the amphiphile component i in the presence of a constant concentration of the other amphiphile component, cmc(i)( *). The Rubingh procedure gives micelles richer in C(16)TAB than the overall mixtures, while procedure (ii) gives micelles having the same composition as in the complete surfactant mixture (alpha(C(10)TAB). Mixed micelles are larger than pure surfactant ones, with nonspherical shape. Using a literature model, the cause of the synergistic effect seems to be a reduction of the hydrocarbon/water contact at the micelle surface when mixed micelles form. Conductivity and ion-selective electrodes indicate that highly ionized premicelles form immediately before the cmc(*). The air/solution interface is strongly nonideal and much richer in C(16)TAB than the composition in the bulk. When micelles form there is a strong desorption from the air/solution interface because micelles are energetically favored when compared with the monolayer.

Role of Hydrophobic Effect on the Noncovalent Interactions Between Salicylic Acid and a Series of beta-Cyclodextrins.

The molecular complexation of salicylic acid (o-hydroxybenzoic acid) by beta-cyclodextrin (beta-CD) and/or two of its most used derivatives, 2,6-di-O-methyl-beta-cyclodextrin (DIMEB) and hydroxypropyl-beta-cyclodextrin (HPBCD), was studied from pH potentiometric measurements. The role of the hydrophobic effect was evaluated by studying the influence of the presence of different constant amounts of a series of alcohols (methanol, ethanol, propanol, and butanol) on the CD:guest interaction at 25 degrees C. The study was carried out by measuring the pH of the hydroalcoholic solutions of the guest, whose concentration is kept constant, as a function of cyclodextrin concentration. The dissociation constant of salicylic acid and the binding constants of the inclusion complexes formed by the CD and both the nonionized (HSA) and ionized (SA-) forms of the guest were simultaneously determined at all alcohol concentrations by using a model previously derived by us. The carboxylic forms were found to bind the CD with higher affinities than the carboxylate partners, irrespective of the polarity of the medium and the cyclodextrin used. The ratio KCD:HSA/KCD:SA- is a constant value characteristic of the cyclodextrin, which points to the hydrophobic effect as one of the main forces involved in the association. A clear influence of the solvent polarity on the affinity of binding was found, in the sense that, as long as the medium becomes more apolar, the interaction between the drug and the cyclodextrin is weakened. A phenomenological limit association curve is proposed to define the limiting conditions for association in the presence of an alcohol as a cosolvent. Copyright 1999 Academic Press.

Thermodynamic analysis of the binding of a hepatoprotectant drug, thioctic acid, by beta-cyclodextrin.

Spectroscopic and thermodynamic studies of the binding of a hepatoprotectant drug, thioctic acid, by beta-cyclodextrin (beta-CD) have been carried out using UV-vis and pH potentiometric measurements. The UV-vis spectra and the pH of the aqueous solutions of the drug were measured (i) as a function of total drug concentration in the absence of cyclodextrin, and (ii) as a function of cyclodextrin concentration at constant drug concentration. The spectroscopic study was done at pH = 7 and 25 degrees C, while the potentiometric study was performed at several temperatures ranging from 15 to 40 degrees C. From the spectroscopic data, the molar absorption coefficient, epsilon, for the pure drug in aqueous media and the stoichiometry of the inclusion complex with beta-CD were determined. The dissociation constant, Ka, of the pure drug (which is a weak acid), and the association constants of the complexes formed by beta-cyclodextrin and both the nonionized (HTIO) and ionized (TIO-) forms of the drug, have been simultaneously determined at several temperatures from the pH data, without the necessity of working with buffered solutions. The nonionic forms are complexed by the beta-CD with higher affinity than their ionic counterparts. From the dependency of the association constants on temperature (van't Hoff analysis), the inclusion complexes formed by HTIO or TIO- and the beta-CD were found to be enthalpy driven, with a favorable enthalpic term dominant over an unfavorable entropic term. Both contributions were found to show a possible dependence with temperature (DeltaCpo not equal 0). This pattern may reveal the contribution of van der Waals interactions, hydrophobic effect, and solvent reorganization as the main driving forces promoting the complexation.

Binding of sodium salicylate by beta-cyclodextrin or 2,6-di-O-methyl-beta-cyclodextrin in aqueous solution.

Speed of sound and conductivity experiments have been done at 298.15 K to study the encapsulation process of sodium salicylate (NaSA) by beta-cyclodextrin (beta-CD) and 2,6-di-O-methyl-beta-cyclodextrin (DIMEB) in aqueous solutions. Since the concentration of the salicyclic form (HSA), coming from the hydrolysis of SA-, is negligible at biological pH, the binding process studied in this work is that of the SA- species. The stoichiometries of the complexes DIMEB: SA- and beta-CD:SA- have been found to be 1:1, as usually determined for most CD:drug complexes. Their association constants and their ionic molar conductivities at infinite dilution have been obtained by fitting the experimental conductivity data with a nonlinear regression method (NLR). For that purpose, a model based on that of Gelb and co-workers has been used. From the values of K beta-CD:SA- = (105 +/- 15)M-1 and KDIMEB:SA- = (140 +/- 20)M-1 obtained, the bioavailability of the salicylate drug in the complexed form has been discussed.