Interaction between Fluorocarbon End-Capped Poly(ethylene oxide) and Cyclodextrins

Supramolecular interaction of a cancer cell photosensitizer in the nanocavity of cucurbit[7]uril: A spectroscopic and calorimetric study

The interaction of small biologically active molecules in the nanocavity of supramolecular host is very interesting and thriving research area. In the presence of supramolecular host the absorption and emission properties of small biologically active molecules were modulated several folds compared to bulk solution. In this study we have investigated the supramolecular interaction of a cancer cell photosensitizer molecule harmane in the presence of cucurbit[7]uril (CB7) as host in aqueous buffer solution (pH∼7.2). We have used steady state absorption, emission and time resolved fluorescence spectroscopy techniques. The thermodynamics of the binding between harmane in the nanochannel of CB7 were studied by using isothermal titration calorimetry (ITC) method. The emission properties of harmane are modulated several fold in the presence of CB7. ITC study indicates that the complexation between harmane and CB7 are enthalpically favourable.

Supramolecular interaction between a hydrophilic coumarin dye and macrocyclic hosts: spectroscopic and calorimetric study

The photophysics of a hydrophilic molecule, 7-(diethylamino)-coumarin-3-carboxylic acid (7-DCCA), was studied in the presence of two macrocycles, (2-hydroxypropyl)-γ-cyclodextrin and cucurbit[7]uril. We have used steady-state absorption, fluorescence, and time-resolved fluorescence emission spectroscopy; Fourier transform infrared (FTIR) spectroscopy; (1)H NMR spectroscopy; and isothermal titration calorimetry (ITC) to confirm the supramolecular host-guest complex formation. The spectral properties of 7-DCCA were modulated in the presence of both macrocycles. It was assigned that 7-DCCA forms a 1:2 complex with (2-hydroxypropyl)-γ-cyclodextrin and cucurbit[7]uril. The large modulation of the emission properties of 7-DCCA in the presence of the macrocycles indicates the formation of supramolecular complexes. A significant shift in the bond vibration frequencies in the FTIR studies showed encapsulation of the dyes in the hydrophobic cavity of the macrocycles. This is further substantiated by the (1)H NMR studies, in which the upfield and downfield shifts of the protons were observed in both the aliphatic and aromatic region in the presence of macrocycles. The time-resolved anisotropy measurements further reinforce the conception of host-guest supramolecular complex formation because, in both cases, the rotational relaxation time increases significantly compared to that in water. A deeper understanding between the differences in interaction of an anionic molecule with cucurbit[7]uril and (2-hydroxypropyl)-γ-cyclodextrin will be achieved through this work. From the ITC measurement, we have formulated the forces due to complex formation.

Nonionic fluorosurfactant as an ideal candidate for one-step modification of gold nanorods

In this work, a novel protocol was developed for size tuning and cetyltrimethylammonium bromide (CTAB) removal of gold nanorods using commercially available nonionic fluorosurfactants (FSN), an excellent candidate for PEG and other modification reagents. The tunable gold nanorods can easily be obtained by stopping the ligand replacement reaction at different time intervals. The FSN-coated gold nanorods are stable in the presence of high salt concentrations and over a wide range of pH values. Additionally, the cellular uptake experiments demonstrate that the FSN-coated gold nanorods have superior features in comparison to the widely used PEG-coated gold nanorods, such as high uptake amount, tunable uptake and excellent stability. Our findings suggest that FSN ligands are an ideal candidate for modifying gold nanorods with tunable aspect ratios, excellent biocompatibility, nontoxicity, and high stability, enabling conjugation to biomolecules for specific targeting, uptake, and delivery.

Cyclodextrin-based polymeric materials: synthesis, properties, and pharmaceutical/biomedical applications

This review describes the synthesis, properties, and, in particular, biomedical and pharmaceutical applications of an upcoming class of polymeric networks and assemblies based on cyclodextrins (CDs). CDs are cyclic oligosaccharides composed of alpha-1,4-coupled d-glucose units, which contain a hydrophobic internal cavity that can act as a host for various, generally lipophilic, guest molecules. Because of this unique physicochemical property, commonly referred to as inclusion complex formation, CDs have often been used to design polymeric materials, such as hydrogels and nanoparticles. Polymeric systems based on CDs exhibit unique characteristics in terms of mechanical properties, stimuli-responsiveness, and drug release characteristics. In this contribution, first, an outline is given of covalently cross-linked polymeric networks in which CD moieties were structurally incorporated to modulate the network strength as well as the complexation and release of low molecular weight drugs. Second, physically assembled polymeric systems are discussed, of which the formation is accomplished by inclusion complexes between polymer-conjugated CDs and various guest molecule-derivatized polymers. Due to their physical nature, these polymeric systems are sensitive to external stimuli, such as temperature changes, shear forces and the presence of competing CD-binding molecules, which can be exploited to use these systems as injectable, in situ gelling devices. In recent years, many interesting CD-containing polymeric systems have been described in literature. These systems have to be optimized and extensively evaluated in preclinical studies concerning their safety and efficacy, making future clinical applications of these materials in the biomedical and pharmaceutical field feasible.

Monoalkyl poly(2-methyl-2-oxazoline) micelles. a small-angle neutron scattering study

This paper presents a SANS study of hydrophobically end-modified poly(2-methyl-2-oxazoline) (POXZ-C(n)) micelles in aqueous solutions. Strong long-range repulsive interactions between the micelles are evidenced by correlation peaks present at concentrations as low as 0.5 wt %. Due to the dissymmetry in size between the hydrophobic and hydrophilic parts of the chains, the micelles have been analyzed using a model of star-like micelles. Large extension of the POXZ arms into the micelles can explain the original SANS behavior. The dissociation of the micellar structures by adding a complexing agent of the alkyl groups, hydroxypropy-beta-cyclodextrin (HPbeta-CD), has been followed by SANS. The micelles are progressively disrupted by the addition of increasing amounts of HPbeta-CD, and the SANS behavior of free chains is recovered in the presence of an excess of the complexing agent.