Reversible and Rewritable Surface Functionalization and Patterning via Photodynamic Disulfide Exchange

Abstract

Light-promoted precise spatial control of target molecules on surfaces is crucial in the development of novel bioanalytical, diagnostic, or sensor tools. Proteins, DNA fragments, peptides and antibodies, [1][2][3][4][5][6] as well as hydrogels, [7] have been immobilized and patterned using a number of photochemical methods, such as thiol-yne, [8] thiol-ene, [9] azide-yne (by photoreduction of copper II), [10] terazole-ene, [11] photo-triggered Diels-Alder reaction, [12] Paterno-Buchi reaction, [13] and some other chemistries capable of photo-triggered formation of reactive functional groups. [14][15][16][17] However, most of the existing photochemical methods lead to irreversible permanent surface functionalization, limiting possible applications in the formation of materials and surfaces with dynamic and responsive properties or reusable 2 functionalities. Reversible surface functionalization methods can be applied to introduce, exchange, or remove a functionality and, thus, generate "smart" surfaces and patterns.Examples of possible applications of such dynamic surfaces are reusability of substrates, possibility to perform "write and erase" procedures (i.e., rewritable surfaces), formation of complex, multi-component and gradient patterns, capture-and-release properties, and the possibility of in-situ manipulation of local environments.To the best of our knowledge, only two photo-induced reversible patterning strategies have been reported so far. Popik et al. [18] showed that reactive o-naphthoquinone methides (oNQMs) produced under UV light from 3-(hydroxymethyl)-2-naphtholcould react with surface thiol groups to yield thioether conjugates, which could be subsequently cleaved by a secondary UV irradiation to regenerate surface thiol groups. [18] In a recent publication, Anseth et al. described the use of allyl sulfides incorporated into a hydrogel to achieve reversible modification with thiol-containing biomolecules.[19]Here, we present a new reversible photo-patterning strategy based on a photo-induced disulfide exchange reaction that allows for reversible photo-functionalization, patterning, as well as exchange or removal of surface functional groups (Figure 1).Disulfide bonds are known to undergo reversible cleavage under basic conditions via thiol-disulfide exchange reactions through intermediate thiolate anions. [20][21][22] However, disulfides can also undergo dynamic exchange reactions by homolytic photo-cleavage to become sulfanyl radicals (Figure1a). This reaction was recently adopted for the synthesis of self-healing polymers. [23,24] We hypothesized that the dynamic nature of disulfide homolysis and recombination under UV irradiation could be utilized to achieve reversible dynamic .In order to demonstrate the reversibility of the photo-induced disulfide exchange, the reaction was repeated 20 times (10 cycles). The results shown in Figure 2b confirm perfect 4 reversibility of the surface modification without significant change of wettability even after 20 consecutive UV-induced functionalizations ar...

Reversible DNA micro-patterning using the fluorous effect

“…14 As a result, investigations concerning the development of new re-writable DNA platforms have become more widespread, and have concentrated on the use of disulphide bonds as reversible anchors for DNA immobilisation, as these covalent linkages are capable of reversible cleavage. 16,17 Although these methods offer strong binding, they require a large excess of reagent to achieve an efficient regeneration, and are often limited by surface degradation after multiple cycles (due to, for example, thiol oxidation on surfaces). 17 In contrast, fluorous surfaces are chemically inert, and the non-covalent nature of the “fluorous effect” allows for the complete removal of surface-bound biomolecules using simple solvent washes.…”

“…16,17 Although these methods offer strong binding, they require a large excess of reagent to achieve an efficient regeneration, and are often limited by surface degradation after multiple cycles (due to, for example, thiol oxidation on surfaces). 17 In contrast, fluorous surfaces are chemically inert, and the non-covalent nature of the “fluorous effect” allows for the complete removal of surface-bound biomolecules using simple solvent washes. 18 In this paper, we show for the first time the implementation of the fluorous effect for the reversible immobilisation of DNA micro-patterns on solid supports.…”

Switching biological functionalities of biointerfaces via dynamic covalent bonds

“…[1][2][3][4][5][6][7] Traditionally, to achieve stable interface functionalization, functional groups are covalently linked to biointerfaces, which usually need multi-steps of chemical synthesis to approach the functionalization. [1][2][3][4][5][6][7] Traditionally, to achieve stable interface functionalization, functional groups are covalently linked to biointerfaces, which usually need multi-steps of chemical synthesis to approach the functionalization.…”

Reversible photo-patterning of soft conductive materials via spatially-defined supramolecular assembly

“…1–3 Nevertheless, the requirement on initial surface functionalization may complicate the process and limit the choice of available substrates. Being able to circumvent this complication, supramolecular assembly via noncovalent interactions has been applied in patterning through photo-triggered molecular assembly and subsequent sol-gel transitions, as the assembly process can occur without reliance on reactive functional groups on substrates.…”