Systematic Comparison of Zwitterionic and Non-Zwitterionic Antifouling Polymer Brushes on a Bead-Based Platform

Abstract

Nonspecific adsorption of biomolecules to solid surfaces, a process called biofouling, is a major concern in many biomedical applications. Great effort has been made in the development of antifouling polymer coatings that are capable of repelling the nonspecific adsorption of proteins, cells, and micro-organisms. In this respect, we herein contribute to understanding the factors that determine which polymer brush results in the best antifouling coating. To this end, we compared five different monomers: two sulfobetaines, a carboxybetaine, a phosphocholine, and a hydroxyl acrylamide. The antifouling coatings were analyzed using our previously described bead-based method with flow cytometry as the read-out system. This method allows for the quick and automated analysis of thousands of beads per second, enabling fast analysis and good statistics. We report the first direct comparison made between a sulfobetaine with opposite charges separated by two and three methylene groups and a carboxybetaine bearing two separating methylene groups. It was concluded that both the distance between opposite charges and the nature of the anionic groups have a distinct effect on the antifouling performance. Phosphocholines and simple hydroxyl acrylamides are not often compared with the betaines. However, here we found that they perform equally well or even better, yielding the following overall antifouling ranking: HPMAA ≥ PCMA-2 ≈ CBMAA-2 > SBMAA-2 > SBMAA-3 ≫ nonmodified beads (HPMAA being the best).

Bioactive Antifouling Surfaces by Visible‐Light‐Triggered Polymerization

“…The coated surfaces were challenged by contacting them with fluorescent single‐protein solutions of BSA‐FITC, Fbg‐Alexa647, and Str‐FITC, respectively, and by a 10% biotinylated bovine serum (BS) solution in PBS for 15 min; this time is typically sufficient to assess the adsorption of proteins onto stable polymer brushes . The fouling by biotinylated BS was detected by subsequent exposure to Str‐FITC solution, which binds to the biotin residues of any fouling serum proteins present on the surface . The fluorescence intensity of exposed bare SiN surfaces is high, due to the high nonspecific adsorption of proteins from corresponding solutions ( Figure a and Table S3, Supporting Information).…”

“…The diblock copolymer structure of poly(HPMA) and poly(CBMA) also showed similarly high antifouling properties to the three single‐protein solutions as well as to the biotinylated bovine serum solution. Both poly(HPMA) and poly(CBMA) are strongly hydrated polymers leading to their excellent antifouling properties …”

“…Deionized water was produced with Milli‐Q Integral 3 system Millipore, Molscheim, France (Milli‐Q water). Bovine serum was obtained and biotinylated as previously described …”

“…The resulting brushes were characterized extensively by X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), attenuated total reflection Fourier‐transform infrared spectroscopy (ATR‐FTIR), and scanning Auger microscopy. The bottom poly(HPMA) block was chosen because it seems to yield the best antifouling properties of the routinely studied brushes, while the poly(CBMA) brushes display high antifouling properties even after significant functionalization . We outline that the Ir(ppy) 3 ‐mediated light‐triggered surface‐initiated living radical polymerization allows for well‐controlled polymerization conditions and for further reinitiation from poly(HPMA) brush.…”

PLL–Poly(HPMA) Bottlebrush-Based Antifouling Coatings: Three Grafting Routes

“… 10 − 15 More recently, however, also poly( N -(2-hydroxypropyl)methacrylamide) [poly(HPMA)] brushes grown by controlled radical polymerizations have been reported to result in stable and highly antifouling coatings, on par with and in some cases outperforming zwitterionic coatings. 7 , 13 , 16 − 19 Although the antifouling properties of poly(HPMA) brushes are not entirely understood, the reported fouling levels are extremely low. 16 , 18 …”