A Comparative Study of Thiol‐Terminated Surface Modification by Click Reactions: Thiol‐yne Coupling versus Thiol‐ene Michael Addition

Abstract

Two quick and efficient, metal catalyst free conjugation routes for the covalent attachment of functional compounds to functionalized surfaces by scanning probe lithography methods are compared in the presented work. The studied methods are thiol‐yne coupling (TYC) and thiol‐ene Michael addition (TEMA). First, the surface of hydroxyl‐terminated glass is thiolated using (3‐mercaptopropyl)trimethoxysilane (MPTMS). Then, in the distinct experiments, the thiol‐terminated surface is spotted by microchannel cantilever spotting with different fluorescent and nonfluorescent inks containing cycloalkyne (dibenzocyclooctyne (DBCO)) or alkene (maleimide) groups. Experiments with different fluorophores show that both routes are successful in coupling functional moieties to the surface in a short time and low temperature. Comparing the protein binding experiments for biotin‐DBCO and biotin‐maleimide reveals a higher surface density of immobilized biotin via the TEMA route. The results from this study are applicable in design and fabricating of biosensors, appropriate for protein detection and other biomedical/biological applications.

Protein Microarray Immobilization via Epoxide Ring‐Opening by Thiol, Amine, and Azide

“…The change in contact angle of the epoxy-terminated surfaces over time might be induced by unmodified hydroxyl groups on the surface decaying until only the thiol groups remain. Comparing the obtained results for WCA of epoxy-terminated surfaces with those of DBCO-terminated [32] and thiolterminated [33] surfaces studied in previous works reveals the hydrophilicity order as follows: DBCO-terminated surface > thiol-terminated surface > epoxy-terminated surface.…”

“…However, as different fluorophores used for surface coupling have different functional groups, different emission spectra, and different intensities even for the same surface concentration of immobilized molecules, another strategy should be employed for the direct comparison of these reactions. [32,33] For this, via epoxide ring-opening routes, biotin-bearing compounds including biotin-thiol, biotin-amine, and biotin-azide were spotted on the epoxy-terminated glasses by μCS into 15 × 15 spot arrays. Biotin is a frequently used linker having strong affinity with streptavidin.…”

“…For this, molecules that have specific affinity with the protein in question (bioreceptors) should be immobilized on a surface (transducer). [29][30][31] In previous works, we prepared microarrays of dyes containing azide or thiol groups on DBCO-terminated glass surfaces [32] and dyes containing maleimide or DBCO groups on thiol-terminated glass surfaces [33] using microchannel cantilevers spotting (μCS). In order to enable even more flexible choice of immobilization chemistry, in this work, three different routes for the surface functionalization of epoxy-terminated glasses will be examined.…”

Controlled Surface Adhesion of Macrophages via Patterned Antifouling Polymer Brushes

“…[57] These droplets can act as reaction vessels where click-reactions take place. [58,61,62] After 20 min of binding, the excess ink was washed away and samples were incubated with fluorescently labeled streptavidin to activate the array for macrophage capture. A typical result of the arraying procedure is shown in Figure 3.…”

Evaluation of click chemistry microarrays for immunosensing of alpha-fetoprotein (AFP)

“…Finally, the best performing fabrication route was evaluated for its efficiency as sensor platform. Click chemistry reactions, which have been widely studied since their introduction by Kolb, Finn and Sharpless in 2001 [24], have unique advantages such as high reaction rates, high yield, mild reaction conditions and easy post-treatment [25][26][27][28][29]. Afterwards, the biotinylated glasses produced following the six different functionalization procedures, which are referred to as routes 1-6 throughout this article, were gradually incubated with solutions of streptavidin and biotinylated anti-AFP to obtain a biotin-streptavidin-biotin sandwich structure.…”