pH-control of the protein resistance of thin hydrogel gradient films

Abstract

We report on the preparation and characterization of thin polyampholytic hydrogel gradient films permitting pH-controlled protein resistance via the regulation of surface charges. The hydrogel gradients are composed of cationic poly(2-aminoethyl methacrylate hydrochloride) (PAEMA), and anionic poly(2-carboxyethyl acrylate) (PCEA) layers, which are fabricated by Self-Initiated Photografting and Photopolymerization (SIPGP). Using a two-step UV exposure procedure, a polymer thickness gradient of one component is formed on top of a uniform layer of the oppositely charged polymer. The swelling of the gradient films in water and buffers at different pH were characterized by imaging spectroscopic ellipsometry. The surface charge distribution and steric interactions with the hydrogel gradients were recorded by direct force measurement with colloidal-probe atomic force microscopy. We demonstrate that formation of a charged polymer thickness gradient on top of a uniform layer of opposite charge can result in a region of charge-neutrality. This charge-neutral region is highly resistant to non-specific adsorption of proteins, and its location along the gradient can be controlled via the pH of the surrounding buffer. The pH-controlled protein adsorption and desorption was monitored in real-time by imaging surface plasmon resonance, while the corresponding redistribution of surface charge was confirmed by direct force measurements.

Interaction Forces on Polyampholytic Hydrogel Gradient Surfaces

“…Due to the transition from net repulsion to net attraction between positions C and D, it is also clear that the results are consistent with the presence of a charge-balanced region with a low net surface charge, as has been suggested previously. 21,29…”

“…Later, we also demonstrated that the location of this charge-balanced region, and hence also the protein adsorption, can be controlled via the pH of the surrounding solution. 29 The mechanisms behind the antifouling properties of these systems are thought to be similar to fouling-resistant zwitterionic polyelectrolytes. 18 Direct force measurements by colloidal probe atomic force microscopy (AFM) to determine the surface charge distribution on these films revealed a charge-balanced area around the zero protein adsorption region and opposite surface charge on either side of this region.…”

A pH-/thermo-responsive hydrogel formed from N,N′-dibenzoyl-l-cystine: properties, self-assembly structure and release behavior of SA

“…Among the various external stimuli, the pH/temperature responsiveness of hydrogels has been most extensively investigated in sensors and biological applications due to the controllability both under in vitro and in vivo conditions. [23][24][25] For example, Gao et al 26 reported a kind of sowood kra lignin pH-responsive hydrogels which were self-assembled through strong intermolecular hydrogen bonds in aqueous solution. However, most of them are formed from polymers.…”

Multi‐Responsive Supramolecular Hydrogels Derived from Gemini Surfactants for Visual Recognition of Isomerization

“…hydrogen bonds, ionic bonds, halogen bonds, metal‐ligand coordnation bonds, π‐π stacking interactions, van der Waals interactions, host‐guest interactions and hydrophobic interactions, and can exhibit reversible behaviors . In consequence, they can often be used as stimuli‐responsive materials sensitive to temperature, light, pH, electronic (magnetic) field, mechanical stress, ion, etc …”

“…[4][5] In consequence, they can often be used as stimuli-responsive materials sensitive to temperature, light, pH, electronic (magnetic) field, mechanical stress, ion, etc. [6][7][8][9][10][11] Among various types of stimuli-responsive materials, the photo-responsive hydrogels are more favored. [12] Therein, azobenzene group as a photo-responsive moiety is especially delightful due to the reversible trans-cis photoisomerization.…”