Protein polymers, polymer brushes

Tugulu, S., Arnold,ASielaff, L,Johnsson, K., Klok, H.-A., Protein-Functionalized Polymer Brushes, Bimmaamokci j 2005,6, 1602-1607. 

D protein arrays based on biotin-streptavidin architectures are likely to be the system of choice due to their ease in handling, excellent signal-to-noise ratio and non-specific interactions. 3D surfaces based on porous gold, sol-gel materials, polymer brushes and dextran surfaces are widely used to mimic the properties of bulk solution and increase the immobilization capacity of proteins. 

Halperin A (1999) Polymer brushes that resist adsorption of model proteins design parameters. Langmuir 15 2525-2533 Haynes CA, Norde W (1994) Globular proteins at solid-liquid interfaces. Colloid Surf B 2 517-566... 

Going to more complex systems such as aggregates, micelles, polymer brushes or polymers with architectures hke stars, dendrimers, combs, etc. or gels, the scientific arena is wide open for new investigations reveahng new phenomena and new insights. This is even more true for the dynamics of proteins and biomaterials in general, where at present basically only diffusion processes or very local dynamics have been addressed. 

Polymer brushes were found to minimize adsorption of proteins by the soft or steric repulsion of the flexible yet immobihzed macromolecules [179], although a generally valid explanation of the protein resistant properties of some hydrophihc brushes is not available. A similar explanation can be formulated for the improvement of the colloidal stability of particle suspensions, when polymer brush-type layers are bound to small particles. This and other intriguing features of polymer brushes prompted a remarkable experimental and theoretical research activity in order to understand and exploit the unique properties of polymer brushes. 

Keywords Gradient Polymer brush Self-assembly Nanoparticles Protein adsorption... 

Another attractive application of polymer brushes is directed toward a biointerface to tune the interaction of solid surfaces with biologically important materials such as proteins and biological cells. For example, it is important to prevent surface adsorption of proteins through nonspecific interactions, because the adsorbed protein often triggers a bio-fouling, e.g., the deposition of biological cells, bacteria and so on. In an effort to understand the process of protein adsorption, the interaction between proteins and brush surfaces has been modeled like the interaction with particles, the interaction with proteins is simplified into three generic modes. One is the primary adsorption. 

Most of these polymers have multi-functional character, which results in cross-linked heterogeneous products. In contrast, monomethoxy polyethylene glycol (PEG) presents only one reactive terminal group per polymer chain. Once PEGy-lated with these compounds, the protein acquires a brush-like shape, with the hydrophilic PEG chains extended from the protein to the solvent. 

Keywords protein adsorption cell adhesion polymer brush surface modification biofouling PEO a-chymotrypsin IgG... 

One should also consider the glycocalyx, a carbohydrate-containing polymer network between the microvilli and the mucus gel coat. It probably consists mainly of oligosaccharide chains that are covalently linked to the lipids and proteins of the brush border membrane. The definite structure of the glycocalyx is not yet available, and nothing can be said about its possible importance as an absorption barrier. 

We can visualize that when our hair is rubbed with a plastic plate, strands of hair stand up from the scalp due to electrostatic repulsion among them. Similarly, when charged functional groups, such as diethylamino groups, are introduced onto the graft chains, the polymer chains extend from the pore surface due to their mutual repulsion. This extended polymer brush conformation provides the protein with three-dimensional binding sites. The multilayer binding of various proteins onto the ion-... 

T. Kawai, K. Saito, K. Sugita and T. Sugo, Extension and Shrinkage of Polymer Brush Grafted onto Porous Membrane Induced by Protein Binding, Macromolecules, 33 (2000) 1306. 

Yun JM, Jung CH, Kim DK, Hwang IT, Choi JH, Ganesan R, et al. Photosensitive polymer brushes grafted onto PTFE film surface for micropatterning of proteins. J Mater Chem 2010 20(10) 2007-12. 

Iwata R, Suk-In P, Hoven VP, Takahara A, Akiyoshi K, Iwasaki Y. Control of nanobiointerfaces generated from well-defined biomimetic polymer brushes for protein and cell manipulations. Biomacromolecules 2004 5(6) 2308-14. 

So far, we have summarized strategies to exploit the chemical versatility of polymer brushes to either immobilize biomolecules by covalent attachment or for significantly decreasing protein adsorption. However, the extended interface created by the brush in a good solvent also provides a swellable, soft layer that can promote the nonspecific immobilization of enzymes and provide an environment that supports their activity. We have tested the functionality of enzymes physisorbed from solution [11]. Because this type of binding is weak, the conformation and activity of the proteins is expected to remain largely intact. To assess the influence of polymer brush chemistry, wettability, and swellability on the physisorption of proteins, model enzymes were chosen. Alkaline phosphatase (ALP) and horseradish peroxidase (HRP) were selected because they both catalyze the transformation of a colorless substrate to a colored product, and the enzymatic activity can therefore be easily monitored with colorimetry. The substrate of choice for ALP is /lara-nitrophenyl phosphate (pNPP), which is hydrolyzed to yield yellow /lara-nitrophenol (pNP) (Figure 4.14). 

Hairy polymer colloids formed in this way might find application in several domains in the future. With a polymer brush exhibiting a LCST, the change of surface properties with temperature could be of high interest for appUcations based on adsorption-desorption processes, such as their use as stationary phases for bioseparation. Recently, PEG-based N-substituted acrylamide maeromonomers were grafted via SI-ATRP from the surface of polystyrene latexes. These PEG-based surfaces showed good protection against nonspecific protein adsorption from... 

A. Hucknall, S. Rangarajan, A. Chilkoti, In pursuit of zero polymer brushes that resist the adsorption of proteins, Adv. Mater. 21 (2009) 2441-2446. 

Ulbricht M, Yang H. Porous polypropylene membranes with different carboxyl polymer brush layers for reversible protein binding via surface initiated graft copolymerization. Chem. Mater. 2005 17 2622-2631. 

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