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

Bifunctional Janus beads made by 'sandwich' microcontact printing using click chemistry

This article describes the preparation of spherical Janus particles by microcontact printing. A set of three different polymer beads (diameter ca. 170 mu m), each bearing different functional groups at their surface, are used to covalently attach distinct functional molecules exclusively on opposing poles of the beads. The covalent modification of the beads involves three different types of click chemistry: epoxide ring opening (ERO), copper catalysed azide-alkyne cycloaddition (CuAAC) and thiol-yne addition (TYA). These reactions are compared with regard to their advantages and disadvantages in the context of "sandwich" microcontact chemistry. The success of surface modification of the beads is verified by fluorescence microscopy and 3D-time of flight secondary ion mass spectrometry measurements and is further supported by reference experiments on planar surfaces bearing the same surface functionality and analysed by X-ray photoelectron spectroscopy, secondary ion mass spectrometry, atomic force microscopy and fluorescence microscopy. Furthermore we demonstrate that sandwich microcontact printing can also be performed on smaller polymer beads with a diameter of ca. 5 mu m. The broad scope of surface chemistry in combination with the simple experimental setup makes this method attractive to a wide range of material science applications, since it combines orthogonality of surface functionalization with high pattern fidelity

Chemically orthogonal trifunctional Janus beads by photochemical 'sandwich' microcontact printing

The combination of topographic and chemical orthogonality on polymer particles by site selective immobilization of functional thiols via thiol-ene chemistry provides a trifunctional particle surface with azide and acid functionalities on opposing poles and alkenes in the equatorial area. These Janus beads are accessible for site selective orthogonal chemical reactions as well as biomolecular recognition on the same particle

“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