Patterned and switchable surfaces for biomaterial applications

Chapter 1 - IntroductionHyun et al., [111] developed a strategy for the switchable attachment of peptidesmodified with an elastin-like polypeptide moiety based upon the pentapeptidesequence of Val-Pro-Gly-X-Gly, where X is any amino acid other than proline. First,a patterned SAM with carboxylic acid functionality was formed by dip-pennanolithography (DPN). An elastin-like polypeptide was then immobilised on thesurface by 1-ethyl-3-(diethylamino)propyl carbodiimide (EDC) – N-hydroxysuccinimide (NHS) coupling. The elastin-like polypeptide is able to switchbetween a soluble and insoluble state at its LCST, which is tunable within thetemperature range of 0-100 °C [111]. The LCST of the polypeptide could be reducedby increasing the ionic strength. Proteins could be adsorbed onto this surface in thecollapsed state and released by reducing the temperature or the ionic strength.Miyata et al., [103] developed a smart hydrogel that swelled 10% in the presenceof an antigen. The creation of an antigen responsive hydrogel adds an important andmore specific stimulus ligand-receptor interactions, to the toolbox for switchablesurfaces. This hydrogel was formed by copolymerisation of acrylate derivatives ofantigen and its corresponding antibody with acrylamide (AAm), such that theantibody-antigen interaction produced extensive crosslinking of the formed hydrogel.Addition of free antigen resulted in competitive binding of the free and immobilisedantigen for the immobilised antibody, resulting in the breakdown of some of thehydrogel crosslinks and a concurrent swelling of the polymer. Miyata et al., [103]used a rabbit immunoglobulin (IgG) antibody as the antigen and a goat anti-rabbitIgG antibody. The swelling was reversible, antigen specific and occurred within atime scale of approximately 1 hr. This switchable swelling may be useful for certaincell culture applications, but it is of great interest for drug delivery on demand.1-38