Dynamic multivalent recongnition of cyclodextrin vesicles

Cyclodextrin bilayer vesicles have dynamic membranes that recognize guest molecules through efficient multivalent host–guest interaction reminiscent of multivalent binding of a ligand with receptors in a biological membrane

Orthogonal, metal-free surface modification by strain-promoted azide–alkyne and nitrile oxide–alkene/alkyne cycloadditions

In this article we present a fast and efficient methodology for biochemical surface patterning under extremely mild conditions. Micropatterned azide/benzaldoxime-surfaces were prepared by microcontact printing of a heterobifunctional cyclooctyne oxime linker on azide-terminated self-assembled monolayers (SAMs). Strain-promoted azide–alkyne cycloaddition (SPAAC) in combination with microcontact printing allows fast and effective surface patterning. The resulting bifunctional azide/oxime substrates could successfully be used for metal-free, orthogonal immobilization of various biomolecules by 1,3-dipolar cycloadditions at room temperature. Azide-decorated areas were modified by reaction with a cyclooctyne-conjugate using SPAAC, while benzaldoxime-decorated areas were activated by in situ oxidation to the reactive nitrile oxides and subsequent nitrile oxide cycloaddition with alkene- and alkyne-functionalized bioconjugates. In addition, orthogonal double immobilization was achieved by consecutive and independent SPAAC and nitrile oxide cycloadditions

Patterned monolayers of nitronyl nitroxide radicals

We report here the results of the preliminary characterization of the monolayer obtained both by self-assembling and microcontact printing of a di-alkyl sulfide nitronyl nitroxide derivative, 11-decyl sulfanyl-undecanyl nitronyl nitroxide of which we describe the synthesis. The sulfide unit has been introduced in order to allow the grafting of the molecule to the gold surface as well as to improve the stability of the organic radical with respect to different grafting agents like thiols, whereas the two long alkyl chains have been introduced to enhance the packing order of the molecules in a self assembled monolayer structure. X-band ESR was used to demonstrate the persistence of the paramagnetic character of the radical in the self-assembled monolayers, and to study its relatively large mobility. The microcontact printed monolayer was characterized by AFM, suggesting a non-negligible mobility of the molecules on the surfaces and a strong tilting of the molecules on the surface

Fabrication of arrays of gold islands on self-assembled monolayers using pulsed laser deposition through nanosieves

Sandwich structures of gold-self-assembled monolayer-gold were prepared by deposition of gold on alkylthiolate self-assembled monolayers on polycrystalline gold, using pulsed laser deposition (PLD) through a nanosieve. The arrays of sandwiches, around 600 nm in diameter, approximately 10 nm high, and spaced 1.6 ím apart, were analyzed using tapping mode atomic force microscopy. Electrochemical copper deposition experiments showed that of the islands deposited on octadecanethiolate monolayers about 15% were electrically insulated from the bottom gold electrode. This means that PLD is a suitable technique for the fabrication of metal-SAM-metal sandwich structures

Controlling the supramolecular assembly of redox active dendrimers at molecular printboards by scanning electrochemical microscopy

Redox-active ferrocenyl (Fc)-functionalized poly(propylenimine) (PPI) dendrimers solubilized in aqueous media by complexation of the Fc end groups with β-cyclodextrin (βCD) were immobilized at monolayers of βCD on glass (“molecular printboards”) via multiple host−guest interactions. The directed immobilization of the third-generation dendrimer−βCD assembly G3-PPI−(Fc)16−(βCD)16 at the printboard was achieved by supramolecular microcontact printing. The redox activity of the patterned dendrimers was mapped by scanning electrochemical microscopy (SECM) in the positive feedback mode using [IrCl6]3- as a mediator. Local oxidation of the Fc−dendrimers by the microelectrode-generated [IrCl6]2- resulted in an effective removal of the Fc−dendrimers from the host surface since the oxidation of Fc to the oxidized form (Fc+) leads to a concomitant loss of affinity for βCD. Thus, SECM provided a way not only to image the surface, but also to control the binding of the Fc-terminated dendrimers at the molecular printboard. Additionally, the electrochemical desorption process could be monitored in time as the dendrimer patterns were gradually erased upon multiple scan

Solid-supported monolayers and bilayers of amphiphilic ß-Cyclodextrin

This paper describes the adsorption and spreading of B-cyclodextrin (CD) vesicles on hydrophobic and hydrophilic substrates, which involves a transition from bilayer vesicles to planar molecular monolayers or bilayers. On substrates that are patterned with self-assembled monolayers by microcontact printing (..CP), the CD vesicles preferentially adsorb on hydrophobic areas instead of hydrophilic (nonionic) areas, and on cationic areas instead of hydrophilic (nonionic) areas. Supported monolayers of amphiphilic cyclodextrins CD1 and CD2 were obtained by adsorption of CD vesicles to hydrophobic substrates, and supported bilayers of amphiphilic cyclodextrins CD1 and CD2 were prepared by adsorption of CD vesicles on cationic substrates. Contact angle goniometry, atomic force microscopy and confocal fluorescence microscopy (CFM) were used to analyze the supported CD layers. The fluidity of the supported CD layers was verified using fluorescence recovery after photobleaching experiments. The supported layers function as a supramolecular platform that can bind suitable guest molecules through inclusion in the CD host cavities. Additionally, the CD host layers were patterned with fluorescent guest molecules by supramolecular ..CP on the supported CD layers. The host-guest interactions were investigated with CFM and fluorescence resonance energy transfer experiments

A carbohydrate-based hydrogel containing vesicles as responsive non-covalent cross-linkers

In this edge article we report the preparation of a supramolecular carbohydrate hydrogel containing cyclodextrin vesicles as 3D junctions. A cellulose polymer is randomly modified with hydrophobic side groups that act as guests for the cyclodextrin hosts on the surface of the vesicles. Hence, the vesicles interconnect the polymer chains into a three-dimensional network and act as multivalent linkages. The resulting gel shows significant shear-thinning and self-healing properties, which make it highly suitable for applications that require injectability. Furthermore, SAXS and cryo-TEM measurements indicate that intact vesicles are present in the gel matrix