Diblock and Random Antifouling Bioactive Polymer Brushes on Gold Surfaces by Visible‐Light‐Induced Polymerization (SI‐PET‐RAFT) in Water

Abstract

that perform certain biological functions, such as specific cell adsorption or interaction with a specific protein or analyte. [3] As part of a device, bioactive surfaces are commonly required to perform in complex biological media such as blood, saliva, or urine. [1,[4][5][6] These fluids typically contain numerous types of proteins and cells that may interfere with the performance of the bioactive surface by nonspecific adsorption. Such nonspecific adsorption by proteins and cells from biological media on a surface is called fouling. [7,8] Thus, the practical application of bioactive surfaces requires antifouling layers capable of preventing protein and cell fouling from complex biological media. [9,10] Antifouling coatings can be generated by immobilizing self-assembled monolayers (SAMs) or "grafted-to" or "graftedfrom" polymer coatings on a surface. [6,[11][12][13][14] SAMs are broadly applied to introduce different functionalities to the surfaces. [15,16] Notably, oligo(ethylene glycol)-terminated [4] and zwitterionic SAMs [17] can resist or decrease fouling from single-protein solutions and cell cultures. "Grafted-to" polymers based on ethylene glycol oxide, oxazoline, [18] N-(2-hydroxypropyl) methacrylamide (HPMA), [12] and zwitterionic moieties [19] have shown good resistance toward single-protein solutions and moderate-to-good resistance toward more complex biological media. The "grafted-from" approach, in which polymer chains are grown from a surface, allows the Surface-initiated photoinduced electron-transfer-reversible addition-fragmentation chain transfer (SI-PET-RAFT) is, for the first time, used for the creation of antifouling polymer brushes on gold surfaces based on three monomers: oligo(ethylene glycol) methyl ether methacrylate (MeOEGMA), N-(2-hydroxypropyl) methacrylamide (HPMA), and carboxybetaine methacrylamide (CBMA). These coatings are subsequently characterized by X-ray photoelectron spectroscopy (XPS) and ellipsometry. The living nature of this polymerization allows for the creation of random and diblock copolymer brushes, which are based on HPMA (superb antifouling) and CBMA (good antifouling and functionalizable via activated ester chemistry). The polymer brushes demonstrate good antifouling properties against undiluted human serum, as monitored by quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR) spectroscopy in real time. The amount of immobilization of bioactive moieties, here an antibody immobilized using N-succinimidyl ester-1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (NHS-EDC) coupling, in the diblock and random copolymer brushes is monitored by SPR, and is analyzed with respect to the brush structure, and is shown to be superior in the diblock copolymer brush. This approach represents a scalable, robust, mild, oxygen-tolerant, and heavy-metal-free route toward the production of antifouling and functional copolymer brushes (on gold surfaces) that open up applications in biosensing and tissue engineering.

Thermoresponsive, Pyrrolidone‐Based Antifouling Polymer Brushes

“…[20] This light-triggered technique allows surface-initiated polymerization of a wide range of monomers into various types of brush architectures without the need of rigorous degassing. [21][22][23][24][25] Among the thermoresponsive polymers employed in polymer brush coatings, poly(N-isopropylacrylamide) (poly(NIPAM)) is-by far-the most intensively investigated, mainly due to its LCST at 31°C. [26] This LCST renders poly(NIPAM) highly relevant for biomedical applications.…”

Evaluation of Dibenzocyclooctyne and Bicyclononyne Click Reaction on Azido‐Functionalized Antifouling Polymer Brushes via Microspotting

“…To obtain a high number of functional groups, side chain functionalization was implemented on copolymer building block brushes. [ 51 ] Additionally, to minimize side effects due to the thickness of the top block on antifouling properties, the thickness of the top layer was adjusted to ≈8 nm, following our previous work. [ 49 ] Generally, the polymer brush consists of two building blocks: the bottom block is an inert layer, highly‐protein repelling and therefore does not require any blocking steps in the performed specific protein binding studies; the top block is a reactive layer functionalized with azide groups, which can participate in the SPAAC reaction.…”

Surface-Immobilized Photoinitiators for Light Induced Polymerization and Coupling Reactions

“…A similar coupling strategy was then used by the same group in a later publication, modifying gold surfaces with cysteamine, followed by the reaction, which was previously mentioned (see Scheme 16 ). The group pointed out that SI-PET-RAFT with eosin Y and triethanolamine as catalyst is a scalable, robust, mild, oxygen-tolerant and heavy-metal-free method for the synthesis of antifouling (co)-polymer brushes on gold surfaces [ 164 ].…”