Glycoclusters and their applications as anti-infective agents, vaccines and targeted drug delivery systems

This chapter reviews the most relevant and recent reports on the applications of glycoclusters as inhibitors and antiadhesive agents against bacteria and viruses, synthetic vaccines, and site-specific drug and gene delivery systems. A common strategy to achieve these goals is the targeting of carbohydrate-binding proteins (lectins) present on the surface of pathogens and tumor cells. Such target lectins are typically involved in cell recognition, signaling, and adhesion or are overexpressed in cell proliferation and tumor development. Multivalency is crucial for the enhancement of such carbohydrate-protein interactions, which are otherwise too weak in biological terms for such applications. In addition, size and spatial arrangement matching between the glycocluster and the biological target is important to obtain a high binding affinity in many cases. A large number of different scaffolds have been used for building such multivalent structures, including cyclodextrins, calixarenes, oligo- and cyclooligopeptides, pentacyclen, pentaerythritol, and saccharides, among others, giving rise to an enormous variety of modes of carbohydrate display with different topologies and valencies

Porous Metal–Organic Framework Nanoparticles

Metal–organic frameworks (MOFs) are hybrid crystalline particles composed of metal cations and organic linkers. Ranging from micro- to nanoscale depending on the preparation conditions, they have achieved a prevalent position among porous materials. The fact that varying either the metal cation or the organic component leads to a wide range of pore sizes and structures has made them very appealing materials in a broad variety of fields, including gas storage, heterogeneus catalysis, separation, imaging, biosensing, agriculture, and biomedicine. By optimizing the internal pore volume, many molecules of different natures can be accommodated within the matrix. For instance, the anticancer drug doxorubicin is well known to enter within iron trimesate MIL-100(Fe) nanoMOF. However, the use of this inclusion complex in biomedicine requires the controlled release of the drug. As reported in one of the articles within this Special Issue [1], this goal can be achieved either by modifying the way the drug is loaded into the MOF or by noncovalently coating the surface with appropriate biocompatible materials. Furthermore, the latter can also lead to a higher colloidal stability of the particles. The innovative use of the ssNMR technique on these inclusion complexes associated with a selective isotope labeling strategy gave the authors deeper insights into both the structure of the complexes as well as to the drug release rates and mechanism

Cyclodextrin-Modified Inorganic Materials for the Construction of Nanocarriers

Inorganic nanoparticles, such as gold, silver, quantum dots and magnetic nanoparticles, offer a promising way to develop multifunctional nanoparticles for biomedical applications. Such nanoparticles have the potential to combine in a single, stable construct various functionalities, simultaneously providing imaging abilities, thermal therapies and the ability to deliver drugs in a targeted fashion. An approach for providing drug loading abilities to these inorganic nanoparticles consists in the modification of their surface with a coating of cyclodextrins, and thereby endowing the nanoparticles with the potential of functioning as drug nanocarriers. This review presents the advances carried out in the preparation of cyclodextrin-contained gold, silver, quantum dot and magnetic nanoparticles as well as their applications as drug nanocarriers. The nanoparticle surface can be modified incorporating cyclodextrin moieties, (i) in situ during the synthesis of the nanoparticles, either using the cyclodextrin as reducing agent or as stabilizer; or (ii) in a post-synthetic stage. The cyclodextrin coating contributes to provide biocompatibility to the nanoparticles and to reduce their cytotoxicity. Cyclodextrin-modified nanoparticles display a multivalent presentation of quasi-hydrophobic cavities that enables, not only drug loading in a non-covalent manner, but also the non-covalent assembly of targeting motifs and optical probes. This paper also provides an overview of some of the reported applications including the in vitro studies and, to a lesser extent, in vivo studies on the drug-loaded nanoparticles behavior

Structure of concanavalin A at pH 8: bound solvent and crystal contacts

9 pages, 3 figures, 4 tables.Concanavalin A has been crystallized in the presence of the ligand (6-S-[beta]-D-galactopyranosyl-6-thio)-cyclomaltoheptaose. The crystals are isomorphous to those reported for ConA complexed with peptides at low resolution (3.00-2.75 Å). The structure was solved at 1.9 Å, with free R and R values of 0.201 and 0.184, respectively. As expected, no molecules of the ligand were bound to the protein. Soaking in the cryobuffer left its fingerprint as 25 molecules of glycerol in the bound solvent, most of them at specific positions. The fact that a glycerol molecule is located in the sugar-binding pocket of each of the four subunits in the asymmetric unit and another is located in two of the peptide-binding sites suggests a recognition phenomenon rather than a displacement of water molecules by glycerol. Crystal contact analysis shows that a relation exists between the residues that form hydrogen bonds to other asymmetric units and the space group: contact Asp58-Ser62 is a universal feature of ConA crystals, while Ser66-His121, Asn69-Asn118 and Tyr100-His205 contacts are general features of the C2221 crystal form.We thank Professor GarcõÂa-Ruiz for his constant support and helpful discussions and suggestions, Dr Cartwright for reviewing the manuscript and Professor Kabsch for providing XDS free of charge.We acknowledge EMBO/DESY for beam time, Professor Martinez Ripoll for his kind support in the preliminary X-ray characterization using the rotating-anode generator at the Instituto de QuõÂmica Fisica Roca Solano (CSIC) and the referees for valuable comments.Work in AA's laboratory is funded by Spanish Plan Nacional grant BMC- 2002-04011-C03.Peer reviewe

Multivalent Lactose–Ferrocene Conjugates Based on Poly (Amido Amine) Dendrimers and Gold Nanoparticles as Electrochemical Probes for Sensing Galectin-3

Galectin-3 is considered a cancer biomarker and bioindicator of fibrosis and cardiac remodeling and, therefore, it is desirable to develop convenient methods for its detection. Herein, an approach based on the development of multivalent electrochemical probes with high galectin-3 sensing abilities is reported. The probes consist of multivalent presentations of lactose–ferrocene conjugates scaffolded on poly (amido amine) (PAMAM) dendrimers and gold nanoparticles. Such multivalent lactose–ferrocene conjugates are synthesized by coupling of azidomethyl ferrocene–lactose building blocks on alkyne-functionalized PAMAM, for the case of the glycodendrimers, and to disulfide-functionalized linkers that are then used for the surface modification of citrate-stabilized gold nanoparticles. The binding and sensing abilities toward galectin-3 of both ferrocene-containing lactose dendrimers and gold nanoparticles have been evaluated by means of isothermal titration calorimetry, UV–vis spectroscopy, and differential pulse voltammetry. The highest sensitivity by electrochemical methods to galectin-3 was shown by lactosylferrocenylated gold nanoparticles, which are able to detect the lectin in nanomolar concentrations

Facile synthesis of per(6-O-tert-butyldimethylsilyl)-α-, β-, and γ-cyclodextrin as protected intermediates for the functionalization of the secondary face of the macrocycles

Per(6-O-tert-butyldimethylsilyl)-α-, β- and γ-cyclodextrin derivatives are well-known as synthetic intermediates that enable the selective mono-, partial, or perfunctionalization of the secondary face of the macrocycles. Although silylation of the primary rim is readily achieved by treatment with tert-butyldimethylsilyl chloride in the presence of pyridine (either alone or mixed with a co-solvent), the reaction typically results in a mixture containing both under- and oversilylated byproducts that are difficult to remove. To address this challenge in preparing a pure product in high yield, we describe an approach that centers on the addition of a controlled excess of silylating agent to avoid the presence of undersilylated species, followed by the removal of oversilylated species by column chromatography elution with carefully designed solvent mixtures. This methodology works well for 6-, 7-, and 8-member rings (α-, β-, and γ-cyclodextrins, respectively) and has enabled us to repeatedly prepare up to ⁓35 g of ≥98% pure product (as determined by HPLC) in 3 d. We also provide procedures for lower-scale reactions, as well as an example of how the β-cyclodextrin derivative can be used for functionalization of the secondary face of the molecule

Electrochemical detection of glutathione S-transferase: An important enzyme in the cell protective mechanism against oxidative stress

Oxidative stress arises when the antioxidant capacity of cells to clean the excess production of reactive oxygen species (ROS) decreases. Several human diseases seem to be related with an increment in the oxidative stress. In this regard, GSH present in the cells works by neutralizing ROS and other xenobiotics through the glutathione S-transferase (GST) enzyme. Thus, the level of expression of GST is an important factor in determining the sensitivity of cells to toxic chemicals or xenobiotic compounds. Therefore, the detection of GST levels is fundamental in the clinical diagnosis of ROS-related diseases. Here, we describe a methodology, based on the voltammetric properties of the ferrocene group (used as electrochemical probe), which can be applied for selective detection of GST levels in human cells. The electrochemical signal measured is associated to the specific interaction of a ferrocenyl-GSH derivate with the G- and H-sites of this enzyme

Binding ability properties of β-cyclodextrin dimers linked through their secondary faces towards cancer chemotherapeutic agent methotrexate

The binding ability properties of two β-cyclodextrin dimers linked through their secondary faces by short, rigid spacer arms towards the cancer chemotherapeutic agent methotrexate were studied by ITC and NMR (1D and ROESY) experiments. Both dimers are able to bind two molecules of methotrexate with a binding constant between 2.4 and 3.5 times higher than that for native β-cyclodextrin, the dimer having the shortest linker forming the most stable complex

A non‐covalent “click chemistry” strategy to efficiently coat highly porous MOF nanoparticles with a stable polymeric shell

Background Metal-organic framework nanoparticles (nanoMOFs) are biodegradable highly porous materials with a remarkable ability to load therapeutic agents with a wide range of physico-chemical properties. Engineering the nanoMOFs surface may provide nanoparticles with higher stability, controlled release, and targeting abilities. Designing postsynthetic, non-covalent self-assembling shells for nanoMOFs is especially appealing due to their simplicity, versatility, absence of toxic byproducts and minimum impact on the original host-guest ability. Methods In this study, several β-cyclodextrin-based monomers and polymers appended with mannose or rhodamine were randomly phosphorylated, and tested as self-assembling coating building blocks for iron trimesate MIL-100(Fe) nanoMOFs. The shell formation and stability were studied by isothermal titration calorimetry (ITC), spectrofluorometry and confocal imaging. The effect of the coating on tritium-labeled AZT-PT drug release was estimated by scintillation counting. Results Shell formation was conveniently achieved by soaking the nanoparticles in self-assembling agent aqueous solutions. The grafted phosphate moieties enabled a firm anchorage of the coating to the nanoMOFs. Coating stability was directly related to the density of grafted phosphate groups, and did not alter nanoMOFs morphology or drug release kinetics. Conclusion An easy, fast and reproducible non-covalent functionalization of MIL-100(Fe) nanoMOFs surface based on the interaction between phosphate groups appended to β-cyclodextrin derivatives and iron(III) atoms is presented. General significance This study proved that discrete and polymeric phosphate β-cyclodextrin derivatives can conform non-covalent shells on iron(III)-based nanoMOFs. The flexibility of the β-cyclodextrin to be decorated with different motifs open the way towards nanoMOFs modifications for drug delivery, catalysis, separation, imaging and sensing. This article is part of a Special Issue entitled “Recent Advances in Bionanomaterials” Guest Editors: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader

Mannoside and 1,2-mannobioside β-cyclodextrin-scaffolded NO-photodonors for targeting antibiotic resistant bacteria

Two β-cyclodextrin derivatives randomly appended on the primary face with both the nitric oxide (NO) photodonor 4-nitro-3-(trifluoromethyl)aniline and a mannose or α(1→2)mannobioside residue are reported to construct targeted NO photoreleasing nanocarriers. 2D ROESY and PGSE NMR suggested supramolecular homodimerization in water by inclusion of the nitroaniline group into the facing macrocycle cavities. Isothermal titration calorimetry on their concanavalin A lectin binding showed an exothermic binding event to the lectin and an endothermic process during the dilution of the conjugates. Both α(1→2)mannobioside and the nitroaniline moieties significantly enhanced the binding to the lectin. These effects might arise from a better fit within the carbohydrate-recognition site in the former case and a multivalent effect caused by homodimerization in the latter. Direct detection of NO by amperometric technique shows that both β-cyclodextrin derivatives release this radical upon excitation with visible light with higher efficiency than the unfunctionalized NO photodonor