Design, synthesis, and in vitro evaluation of new amphiphilic cyclodextrin-based nanoparticles for the incorporation and controlled release of acyclovir.

Acyclovir possesses low solubility in water and in lipid bilayers, so that its dosage forms do not allow suitable drug levels at target sites following oral, local, or parenteral administration. In order to improve this lack of solubility, new cyclodextrin-based amphiphilic derivatives have been designed to form nanoparticles, allowing the efficient encapsulation of this hydrophobic antiviral agent. The present work first describes the synthesis and characterization of five new O-2,O-3 permethylated O-6 alkylthio- and perfluoroalkyl-propanethio-amphiphilic ß-cyclodextrins. These derivatives have been obtained with good overall yields. The capacity of these molecules to form nanoparticles in water and to encapsulate acyclovir has then been studied. The nanoparticles prepared from the new ß-cyclodextrin derivatives have been characterized by dynamic light scattering and have an average size of 120nm for the fluorinated derivatives and 220nm for the hydrogenated analogs. They all allowed high loading and sustained release of acyclovir.

Preparation and characterization of CK2 inhibitor-loaded cyclodextrin nanoparticles for drug delivery.

Casein Kinase 2 (CK2) is a ubiquitous kinase protein currently targeted for the treatment of some cancers. Recently, the series of indeno[1,2-b]indoles has revealed great interest as potent and selective CK(2) ATP-competitive inhibitors. Among them, 1-amino-5-isopropyl-5,6,7,8-tetrahydroindeno[1,2-b]indole-9,10-dione (CM1) was selected for an encapsulation study in order to improve its biodisponibility. Its complexation was evaluated at the molecular scale, with a series of fluorinated or hydrocarbonated amphiphilic cyclodextrins (CDs). Then the encapsulation of CM1 within CD nanoparticles at the supramolecular level was achieved. Nanoparticles formed between CM1 and hexakis[6-deoxy-6-(3-perfluorohexylpropanethio)-2,3-di-O-methyl]-α-cyclodextrin, a fluorinated amphiphilic α-cyclodextrin, gave the best results in terms of encapsulation rate, stability and drug release. These nanospheres showed an encapsulation efficiency of 65% and a sustained release of the entrapped drug over 3h. Based on these results, encapsulation within fluorinated amphiphilic CD nanoparticles could be considered as a potential drug delivery system for indenoindole-type CK2 inhibitors, allowing better biodisponibility and offering perspectives for tumor targeting development.

Selectivity among two lectins: probing the effect of topology, multivalency and flexibility of "clicked" multivalent glycoclusters.

The design of multivalent glycoconjugates has been developed over the past decades to obtain high-affinity ligands for lectin receptors. While multivalency frequently increases the affinity of a ligand for its lectin through the so-called "glycoside cluster effect", the binding profiles towards different lectins have been much less investigated. We have designed a series of multivalent galactosylated glycoconjugates and studied their binding properties towards two lectins, from plant and bacterial origins, to determine their potential selectivity. The synthesis was achieved through copper(I)-catalysed azide-alkyne cycloaddition (CuAAC) under microwave activation between propargylated multivalent scaffolds and an azido-functionalised carbohydrate derivative. The interactions of two galactose-binding lectins from Pseudomonas aeruginosa (PA-IL) and Erythrina cristagalli (ECA) with the synthesized glycoclusters were studied by hemagglutination inhibition assays (HIA), surface plasmon resonance (SPR) and isothermal titration microcalorimetry (ITC). The results obtained illustrate the influence of the scaffold's geometry on the affinity towards the lectin and also on the relative potency in comparison with a monovalent galactoside reference probe.

Novel nanoparticles made from amphiphilic perfluoroalkyl alpha-cyclodextrin derivatives: preparation, characterization and application to the transport of acyclovir.

The preparation of aqueous suspensions of nanoparticles of the fluorinated amphiphilic alpha-cyclodextrins hexakis[6-deoxy-6-(3-perfluoroalkylpropanethio)-2,3-di-O-methyl]-alpha-cyclodextrin and their hydrocarbon analogues was studied. The complexation of acyclovir by modified alpha-cyclodextrin, the encapsulation efficiency and release profile were measured as an assessment of the properties of such nanoparticles regarding drug delivery applications. Stable aqueous suspensions of nanoparticles were prepared using nanoprecipitation method without using surface-active agent. The organic solvent (ethanol) and cyclodextrin concentration (0.4 mM) were carefully selected. The nanoparticles prepared from these new amphiphilic alpha-cyclodextrin derivatives according to optimized conditions have an average diameter of 100 nm for fluorinated derivatives and 150 nm for hydrocarbon analogues. Suspensions were stable over at least 9 months. Acyclovir forms inclusion complexes of 1:1 stoichiometry and high stability constants (from 700 mol L(-1) to 4000 mol L(-1) in ethanol) as assessed from UV/vis spectroscopy and Electrospray Ionization Mass Spectroscopy. Satisfactory loading of acyclovir inside the nanoparticles was achieved according to the "highly loaded" preparation method (encapsulation efficiency approximately 40%). Nanoparticles based on the fluorinated compounds delayed the drug release up to 3 h with little initial burst release. Fluorinated amphiphilic alpha-cyclodextrins self-assemble in the form of nanospheres that encapsulate acyclovir and allow sustained release, showing their potential for applications to drug delivery.

Control of the regioselectivity for new fluorinated amphiphilic cyclodextrins: synthesis of di- and tetra(6-deoxy-6-alkylthio)- and 6-(perfluoroalkypropanethio)-alpha-cyclodextrin derivatives.

Twelve new di- and tetraderivatized alpha-cyclodextrin molecules having either alkylthio and perfluoroalkylpropanethio functions at the primary face have been synthesized by using the procedure of Sinay for di-O-debenzylation of perbenzylated alpha-cyclodextrins. A new strategy of protection/deprotection has been developed for introducing the lipophilic chains. The coupling reaction involves the reaction between the appropriate alpha-cyclodextin derivative, regioselectively modified at C-6 positions by a good leaving group (O-mesityl for disubstituted or iodine for tetrasubstituted derivatives), with the thioalkyl or the thioperfluoroakylpropane chains. These nucleophilic reagents are obtained from the in situ basic hydrolysis of the alkylisothiouronium bromides or perfluoalkylropropane and the isothiouronium iodides. These multistep reactions give the desired amphiphilic alpha-cyclodextrins in good overall yields of 33% to 58%.

Sulfated and non-sulfated amphiphilic-beta-cyclodextrins: impact of their structural properties on the physicochemical properties of nanoparticles.

PURPOSE: The aim of this work was to study the preparation of nanospheres from amphiphilic beta-cyclodextrins formed (a) by different acylation degrees (DA) at the secondary hydroxyl face (DA=14 and 21) followed by varying (b) the sulfatation degrees (DS) at the primary hydroxyl face (DS=0, 4 and 7). METHODS: The physicochemical properties of the synthesized compounds such as molecular weights, the theoretical HLB values and the critical micellar concentration values and their surface area were presented. The nanoparticles prepared from amphiphilic beta-cyclodextrins were characterized by mean size, zeta potential and their morphology. RESULTS: The compounds presented hydrophile-lipophile balance values ranging from 5.6 to 10. For sulfated amphiphilic beta-cyclodextrins having HLB values higher than 8, were able to self-organize in water to form nanoparticles. However, for the amphiphilic beta-cyclodextrins that HLB values lower than 6.6 are insoluble in water but soluble in organic solvents rendering possible the preparation of nanoparticles by nanoprecipitation technique. CONCLUSION: An interesting correlation between the amphiphilic-beta-cyclodextrin structures and their ability to form nanospheres has been established. The association of sulfated amphiphilic-beta-CDs to the peracylated amphiphilic-beta-CDs was interesting, it led to improve the stability of nanospheres size and probably confer them a biological activity.

Synthesis and characterisation of novel nanospheres made from amphiphilic perfluoroalkylthio-beta-cyclodextrins.

This work describes the synthesis of new amphiphilic perfluorohexyl- and perfluorooctyl-propanethio-beta-cyclodextrins and the comparison of the ability of these molecules and alkyl analogue, nonanethio-beta-cyclodextrin to form nanospheres. Nanospheres were prepared using nanoprecipitation method (perfluoroalkylthio-beta-cyclodextrin in THF [0.11 x 10(-3)M], stirring rate 700rpm, addition of aqueous phase at 64 degrees C into organic phase at 50 degrees C). They were characterised by Photon Correlation Spectroscopy (PCS) and by electron microscopy (SEM and cryo-TEM). The nanospheres prepared from these new beta-cyclodextrin derivatives have an average size of 260nm, and appear to be spherical in cryo-TEM images. Whereas alkyl analogue forms polydisperse aggregates with sizes in the range 60-350nm.

Synthesis and characterisation of sulfated amphiphilic alpha-, beta- and gamma-cyclodextrins: application to the complexation of acyclovir.

The synthesis of sulfated amphiphilic alpha-, beta- and gamma-cyclodextrins was achieved according to the standard protection-deprotection procedure. The formation of inclusion complexes between the amphiphilic alpha-, beta- and gamma-cyclodextrins and an antiviral molecule, acyclovir (ACV) was investigated by UV-visible spectroscopy (UV-Vis) and electrospray ionisation mass spectrometry (ESIMS). UV-Vis spectroscopy allowed determination of the stoichiometry and stability constants of complexes, whereas ESIMS, a soft ionisation technique, allowed the detection of the inclusion complexes. The results showed that the non-sulfated amphiphilic cyclodextrins exhibit a 1:2 stoichiometry with acyclovir, while sulfated amphiphilic cyclodextrins, except gamma-cyclodextrin, exhibit a 1:1 stoichiometry indicating the loss of one interaction site. Non-covalent interactions between acyclovir and non-sulfated amphiphilic cyclodextrins appear to take place both in the cavity of the cyclodextrin and inside the hydrophobic zone generated by alkanoyl chains. In contrast, in the case of sulfated amphiphilic cyclodextrins, the interactions appear to involve only the hydrophobic region of the alkanoyl chains.

Scanning electron microscopy and atomic force microscopy imaging of solid lipid nanoparticles derived from amphiphilic cyclodextrins.

Scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been applied to the imagery of solid lipid nanoparticles (SLNs) formulated from an amphiphilic cyclodextrin, 2,3-di-o-alkanoyl-beta-cyclodextrin, beta-CD21C6. Comparison of the results shows that the vacuum drying technique used in sample preparation for SEM causes shrinkage in the size of the SLNs, whereas the deposition method used for AFM causes the SLNs to form small clusters. The hydrodynamic diameter determined from photon correlation spectroscopy (PCS) is 359+/-15 nm and the zeta potential is -25 mV.

Interfacial interactions between amphiphilic cyclodextrins and physiologically relevant cations.

The compression isotherms of a series of amphiphilic cyclodextrins, formed (a) by acylation at the secondary hydroxyl face and (b) by acylation accompanied by varying degrees of sulfatation (DS) at the primary hydroxyl face (DS=0, 4, and 7), have been studied on subphases of pure water and of water containing NaCl, KCl, MgCl(2), and CaCl(2) at inter- and extracellular concentrations. The formation of solid lipid nanoparticles (SLNs) by two of the molecules has been observed, while these do not aggregate at concentrations of monovalent salts up to 150 mM for the sulfated derivative. In the presence of divalent salts one of these with a DS=0 for sulfatation degree flocculates at divalent salt concentrations below 0.1 mM while the other with a DS=4 flocculates at Mg(2+) concentration above 5 mM and a Ca(2+) concentration above 3 mM. AFM noncontact mode imaging has been carried out, in air, for the SLNs deposited on mica.

Molecular recognition by Kluyveromyces of amphotericin B-loaded, galactose-tagged, poly (lactic acid) microspheres.

In an effort to develop a new way of drug delivery, especially for polyenic antifungal molecules, we have incorporated amphotericin B (AmB) into biodegradable galactosylated poly (L-lactic acid) (L-PLA) and poly (L-lactic-co-glycolic acid) (PLGA) microspheres. These drug carriers were prepared by solvent evaporation using an oil/water (o/w) emulsion. The ratio of galactosyl spacers with different chain lengths was 1.74-2.78%. The maximal quantity of AmB encapsulated reported to 100 mg of the galactosylated microspheres was 7.14 mg for L-PLA (encapsulation rate 45% of mole) and 6.42 mg for PLGA derivatives (encapsulation rate 81% of mole). In our yeast model, drug release depended on three factors: (i) presence of galactosylated antennae, (ii) length of galactosyl antenna and (iii) nature of the polymer. More of the AmB trapped in PLGA microspheres was released than from PLA microspheres. These novel functionalised microspheres could be required for the delivering of therapeutic agents according to their recognition to specific cells.