Reversible Protein Adsorption on Mixed PEO/PAA Polymer Brushes: Role of Ionic Strength and PEO Content

Abstract

Proteins at interfaces are a key for many applications in the biomedical field, in biotechnologies, in biocatalysis, in food industry, etc. The development of surface layers that allow to control and manipulate proteins is thus highly desired. In previous works, we have shown that mixed polymer brushes combining the protein-repellent properties of poly(ethylene oxide) (PEO) and the stimuli-responsive adsorption behavior of poly(acrylic acid) (PAA) could be synthesized and used to achieve switchable protein adsorption. With the present work, we bring more insight into the rational design of such smart thin films by unravelling the role of PEO on the adsorption/desorption of proteins. The PEO content of the mixed PEO/PAA brushes was regulated, on the one hand, by using PEO with different molar masses and, on the other hand, by varying the ratio of PEO and PAA in the solutions used to synthesize the brushes. The influence of ionic strength on the protein adsorption behavior was also further examined. The behavior of three proteins-human serum albumin, lysozyme, and human fibrinogen, which have very different size, shape, and isoelectric point-was investigated. X-ray photoelectron spectroscopy, quartz crystal microbalance, atomic force microscopy, and streaming potential measurements were used to characterize the mixed polymer brushes and, in particular, to estimate the fraction of each polymer within the brushes. Protein adsorption and desorption conditions were selected based on previous studies. While brushes with a lower PEO content allowed the higher protein adsorption to occur, fully reversible adsorption could only be achieved when the PEO surface density was at least 25 PEO units per nm. Taken together, the results increase the ability to finely tune protein adsorption, especially with temporal control. This opens up possibilities of applications in biosensor design, separation technologies, nanotransport, etc.

Alkoxy-functionalized ionic liquid electrolytes: understanding ionic coordination of calcium ion speciation for the rational design of calcium electrolytes

“…5b), four peaks can be discerned at binding energies of 290.2, 288.1, 286.0, and 284.8 eV, which can be assigned to À C-F, À C-OO, À C-O-À C and À C-(C,H) groups, respectively. [44][45][46] The O 1s spectrum in Fig. 5c displays three obvious peaks located at 533.5, 532.3 and 531.2 eV, corresponding to the OQC-À O, C-À O-C and À OQC-O groups, respectively, which is in agreement with the C 1s spectrum.…”

“…It can be noticed that the C-O-C group is dominating the C 1s spectrum as well as the O 1s spectrum, which is a typical characteristic of poly(ethylene oxide)-like compounds. 44,45 Thus, based on the element content and surface chemistry analysis of Ca deposits obtained from the [Ca(BH 4 ) 2 ] 0.05 [N 07 TFSI] 0.95 electrolyte, we propose that the degradation products of Ca-ion speciation in this IL-based electrolyte form a protective SEI layer mainly composed of organic polyether chains. This organic-rich, but inorganic-poor SEI layer seems to be Ca-ion conductive enabling the Ca metal dissolution/ deposition processes.…”

Design of Ultra-Thin PEO/PDMAEMA Polymer Coatings for Tunable Protein Adsorption

“…It is a linear molecule with a molecular mass of 340 kDa and an iep at pH 5.8. This protein was chosen due to its ability to adsorb below and above its iep, as reported in the literature [30,[35][36][37][38]. The third protein chosen was Lys, a small protein (14.3 kDa), with its iep at 11 [25,39,40].…”

“…The authors confirmed significant adsorption of BSA at pH 5.8. After desorption performed at pH 4, pH 9 and 1 M NaCl only 53 % of proteins were released from the surface.As it was recently shown, mixed polymer coatings composed of protein-repellent and protein-adsorbing polymers are very promising due to their ability to control protein adsorption/desorption processes [27][28][29][30][31]. For example, Välimäki et al [31] used poly (ethylene glycol) PEO-PDMAEMA block copolymers for efficient heparin binding.…”

Influence of poly(acrylic acid) grafting density on switchable protein adsorption/desorption of poly(2‐methyl‐2‐oxazoline)/poly(acrylic acid) mixed brushes

“…and thus build stimuli‐responsive (or smart) surfaces to control protein adsorption/desorption . Dupont‐Gillain and coworkers have designed binary mixed brushes of poly(ethylene glycol) [poly(ethylene oxide) (PEO)] and poly(acrylic acid) (PAA), in which PEO builds the protein repelling part, PAA as the stimuli‐responsive part can stretch or collapse upon pH and I change. They demonstrate the effectiveness of mixed PEO/PAA brushes to reversibly and repeatedly adsorb and desorb albumin, lysozyme, collagen, and immunoglobulin G under selected pH and I conditions.…”