Responsive polymer brushes protein molecules

Responsive polymer bmshes are not only investigated on planar substrates, but can also be used to decorate nanoparticles (Figure 5.13). Here, the key biomedical application is the accommodation (immobilize) of biofunctional moieties such as proteins or enzymes (Wittemann Ballauff, 2006 Wittemann, Haupt, BaUauff, 2003). If there is sufficient attraction between a protein and a polymer brush to overcome excluded volume effects (the antifouling properties of the brush), much larger amounts of protein can accumulate inside a brnsh layer than can be adsorbed onto just the particles surface. The role of the attached polymer chains is thus to strongly increase the available surface area. In Fignre 5.13, we schematically show a spherical polymer brush filled with adsorbed nanoparticles. Because, protein molecules inunobilized by polymers are found to be relatively weakly bound, they keep their conformation and (enzymatic)... 

In addition to pH-responsiveness, the behavior of polymer brushes may also be altered by temperature. For instance, electrochemistry-induced radical polymerization was used to fabricate a PNIPAAm bmsh [67]. The authors used this PNIPAAm brush in conjunction with ITO to create electrically heated electrodes (H Es). Altered HEs exhibited rapid temperature increases upon heating and this temperature enhancement was reversible. The control and release properties of the HE system were then assessed by means of the model protein hemoglobin. Hemoglobin diluted in phosphate-buffered sahne was exposed to the bmsh at 20 °C when it was in the expanding state. Upon a temperature change above the brush LCST, the brush transitioned to the shrunken state, capturing the hemoglobin molecules. 

Lipid-bilayer membranes on solid substrates are often used as cell-surface models connecting biological and artificial materials. They can be placed either directly on solids or on ultrathin polymer supports, such as brushes or hydrogels, which mimic the extracellular matrix. A similar approach has been applied to polymer membranes with the advantage of tunable thickness, easier chemical modifications to allow stimulus responsiveness, or the attachment of active molecules by incorporation of reactive end groups. In addition, incorporated proteins have lower interactions with the support because of the increased membrane thickness, and therefore behave as in a natural environment. ... 

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