Surface-attached hydrogel coatings via C,H-insertion crosslinking for biomedical and bioanalytical applications (Review)

Abstract

A novel method for the generation of surface-attached hydrogel coatings and their use in biomedical applications is discussed. This short review concentrates on surface architectures that are prepared from prepolymers carrying reactive groups suitable for crosslinking via C,H insertion reactions [C,H insertion crosslinking (CHic)]. Upon photochemical or thermal activation these groups do not only induce the crosslinking of the system, but also connect the forming gel to the surface as long as the surface itself consists of an organic material. C,H groups as the reaction partner are available in abundance at practically all types of organic surfaces such as biomaterials or polymers, rendering the technique almost universally applicable. Surface-attached gels prepared this way show unique swelling properties due to the confinement of the chains, as the obtained essentially two-dimensional gels can only swell in one dimension. This anisotropic swelling does not permit penetration of the layers by macromolecules so that the surfaces become bioinert, i.e., are strongly protein and cell repellent. It is discussed how this property can be used to control the interaction of surfaces with biological species ranging from the level of biomolecules to living cells. A combination of the CHic chemistry and microstructuring techniques opens further avenues for the study of the behavior of cells to the generation of novel bioanalytical devices.

Prevention of Ocular Tenon Adhesion to Sclera by a PDMAA Polymer to Improve Results after Glaucoma Surgery

“…A strategy which has been described recently, which allows to generate protein‐repellent surfaces in the presence of water, is to make use of neutral surface‐attached hydrogels generated by C–H insertion crosslinking (CHic) . In this process a photosensitive hydrogel precursor is physically deposited onto the surface and through brief irradiation it is transformed into the hydrogel, which is simultaneously attached to the surface.…”

“…Neutral, surface‐attached hydrogels have been shown to be protein and cell repellent . The key concept behind such an approach is that proteins expressed by the cells show no enthalpic interactions (i.e., no Coulombic or hydrophobic interactions) with the coating.…”

PnBA/PDMAA‐Based Iron‐Loaded Micropillars Allow for Discrete Cell Adhesion and Analysis of Actuation‐Related Molecular Responses

“…To circumvent the above‐mentioned problems, a defined strategy was used to ensure that cells only adhere to the top faces of the pillars. The process is based on reactive prepolymers that crosslink upon a photochemical stimulus, generating reactive species, such as biradicaloid triplets, nitrenes, or carbenes,29 which then formally insert into C,H bonds, e.g., of neighboring polymer chains, and link them together. This principle is known as C,H insertion crosslinking (CHic) and it can also be used to covalently modify the surfaces of the completed polymer microstructures, hereby enabling selective coating of the pillar surfaces.…”

Wafer‐Scale Fabrication of Conducting Polymer Hydrogels for Microelectrodes and Flexible Bioelectronics

“…The crosslinking was performed via UVlight exposure through a photomask. Thereby, the benzophenone units (MABP) of the PDMAAp polymer chains are photochemically activated and crosslink with C–H groups of neighboring polymer chains (C–H insertion crosslinking) . Simultaneously, the forming network binds to the surface bound benzophenone within the 3‐EBP silane layer to form a surface attached hydrogel.…”