Bart Jan Ravoo

Light-responsive capture and release of DNA in a ternary supramolecular complex.

The wavelength determines whether DNA is captured in a light-responsive ternary supramolecular complex or released (see scheme). The reversible binding of DNA is triggered by a photoisomerization, which switches the complex from a multivalent to a monovalent binding mode.

Shape and release control of a peptide decorated vesicle through pH sensitive orthogonal supramolecular interactions.

A pH sensitive carrier is obtained by coating a cyclodextrin vesicle with an adamantane-terminated octapeptide through the formation of an inclusion complex. Upon lowering the pH from 7.4 to 5.0, the formation of peptide beta-sheets on the vesicle surface induces a transition of the bilayer from a sphere to a fiber. This transition is fully reversible and repeatable. The vesicles release their cargo upon fiber formation.

Light‐Responsive Molecular Recognition and Adhesion of Vesicles

Supramolecular glue: The photoinduced isomerization of difunctional azobenzenes can be used to induce and reverse the molecular recognition and adhesion of bilayer vesicles made up of cyclodextrin (CD) molecules. The molecular basis of this light-responsive supramolecular glue is the cis–trans isomerization of the azobenzene (see picture; black circles CD, green trans-azobenzene, red cis-azobenzene).

Stamps, inks and substrates: polymers in microcontact printing

Microcontact printing (μCP) is a straightforward method for the preparation of micro- and nanostructured surfaces. The key element in μCP is a polymeric stamp with a relief pattern. This stamp is “inked” and put in contact with the substrate surface. Ideally, the ink is transferred from stamp to substrate only in the area of contact. This review focuses on the important role of polymers in μCP. First of all, polymers are the material of choice to make μCP stamps. Furthermore, μCP is a useful method for preparing microstructured polymer surfaces. Polymers can be applied as inks in μCP so that microstructured polymer surfaces are obtained in a single printing step. Microstructured polymer surfaces can also be obtained by μCP on polymer substrates. A wide range of inks – including polymer inks – can be patterned on polymer substrates by μCP. In short, polymers are widely used as stamps, inks and substrates in μCP and we have organized this review accordingly.

Sugar-Decorated Sugar Vesicles: Lectin-Carbohydrate Recognition at the Surface of Cyclodextrin Vesicles

An artificial glycocalix self-assembles when unilamellar bilayer vesicles of amphiphilic beta-cyclodextrins are decorated with maltose and lactose by host-guest interactions. To this end, maltose and lactose were conjugated with adamantane through a tetra(ethyleneglycol) spacer. Both carbohydrate-adamantane conjugates strongly bind to beta-cyclodextrin (K(a) approximately 4 x 10(4) M(-1)). The maltose-decorated vesicles readily agglutinate (aggregate) in the presence of the lectin concanavalin A, whereas the lactose-decorated vesicles agglutinate in the presence of peanut agglutinin. The orthogonal multivalent interaction in the ternary system of host vesicles, guest carbohydrates, and lectins was investigated by using isothermal titration calorimetry, dynamic light scattering, UV/Vis spectroscopy, and cryogenic transmission electron microscopy. It was shown that agglutination is reversible, and the noncovalent interaction can be suppressed and eliminated by the addition of competitive inhibitors, such as D-glucose or beta-cyclodextrin. Also, it was shown that agglutination depends on the surface coverage of carbohydrates on the vesicles.

Photochemical microcontact printing by thiol-ene and thiol-yne click chemistry.

This article describes the microstructured immobilization of functional thiols on alkene- and alkyne-terminated self-assembled monolayers on silicon oxide substrates by photochemical microcontact printing. A photochemical thiol-ene or thiol-yne “click” reaction was locally induced in the area of contact between stamp and substrate by irradiation with UV light (365 nm). The immobilization reaction by photochemical microcontact printing was verified by contact angle measurements, X-ray photoelectron spectroscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry. The reaction rate of photochemical microcontact printing by thiol-ene chemistry was studied using time dependent contact angle measurements. The selective binding of lectins to galactoside microarrays prepared by photochemical microcontact printing was also demonstrated. It was found that photochemical microcontact printing results in a high surface coverage of functional thiols within 30 s of printing even for dilute (mM) ink solutions.

Transfer Printing of DNA by “Click” Chemistry

This paper describes a straightforward procedure to immobilize oligonucleotides on glass substrates in well‐defined micropatterns by microcontact printing with a dendrimer‐modified stamp. The oligonucleotides are efficiently immobilized by “click” chemistry induced by microcontact printing. Acetylene‐modified oligonucleotides were treated with an azide‐terminated glass slide under the confinement of the dendrimer‐modified stamp, without the use of a CuI catalyst. The immobilization is an irreversible, covalent, and one‐step reaction that results in stable attachment of the oligonucleotides. Oligonucleotides with the acetylene‐modification at the 5′ terminus hybridize selectively with full‐length, complementary targets. Strands with more than one acetylene linker do not hybridize with complementary strands.

Photoresponsive Capture and Release of Lectins in Multilamellar Complexes

The development of triggered release systems for delivery of peptides and proteins is critical to the success of biological drug therapies. In this paper we describe a dynamic supramolecular system able to capture and release proteins in response to light. The ternary system self-assembles in a dilute aqueous solution of three components: vesicles of amphiphilic cyclodextrin host, noncovalent cross-linkers with an azobenzene and a carbohydrate moiety, and lectins. The cross-linkers form inclusion complexes with the host vesicles, provided the azobenzene is in the trans state. The formation of a ternary complex with lectins requires a high density of cross-linkers on the surface of vesicles. The key innovation in this system is a photoinduced switch from a multivalent, high-affinity state that captures protein to a monovalent, low-affinity state that releases protein. By using isothermal titration calorimetry, dynamic light scattering, UV/vis spectroscopy, and cryogenic transmission electron microscopy, we demonstrate that photoinduced capture and release of lectins in dense multilamellar complexes is highly efficient, highly selective, and fully reversible.

Inverse Opal Spheres Based on Polyionic Liquids as Functional Microspheres with Tunable Optical Properties and Molecular Recognition Capabilities

Based on the combination of the unique features of both polyionic liquids and spherical colloidal crystals, a new class of inverse opaline spheres with a series of distinct properties was fabricated. It was found that such photonic spheres could not only be used as stimuli-responsive photonic microgels, but also serve as multifunctional microspheres that mimic the main characteristics of conventional molecules, including intrinsic optical properties, specific molecular recognition, reactivity and derivatization, and anisotropy.

“Sandwich” Microcontact Printing as a Mild Route Towards Monodisperse Janus Particles with Tailored Bifunctionality

A “sandwich” microcontact printing method is reported. A monolayer of porous epoxy polymer microspheres is transformed into Janus particles with distinct functionality on each face by reaction with amine functional fluorescent dyes, carbohydrates, and magnetic nanoparticles.