Patterned and switchable surfaces for biomaterial applications
Patterned and switchable surfaces for biomaterial applications
Patterned and switchable surfaces for biomaterial applications
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Chapter 1 - IntroductionA major problem with protein microarrays is the ability to attach the protein whistmaintaining its functionality. Various methods of attachment are used includingphysioadsorption, metal complexation, covalent attachment, electrostatic attractionor by biological interaction (biotin-avidin) (see section 1.2.5) [79, 131, 132]. Thecommon problem is that the attachment is either weak, enabling protein to be washedaway or replaced with another protein, or the binding denatures or sterically hindersthe binding site. One strategy to combat this was achieved by the production of aPLA-PEG film containing biotin [133]. Addition of avidin as a linker moleculeenabled the potential attachment of biotin modified proteins, where if correctlymodified, would result in correctly orientated proteins that are strongly attached.Another similar strategy is the use of His-proteins, which <strong>for</strong>m a chelate complexwith Ni 2+ . Surfaces modified with carboxylic functionality are able to <strong>for</strong>m such Ni 2+complexes <strong>and</strong> effectively immobilise His-proteins, which can be subsequentlyremoved by addition of either EDTA that chelates Ni 2+ , thus, breaking apart thecomplex <strong>for</strong>med with the his-protein, or imidiazole that competitively binds to theNi 2+ comples in place of the his-proteins. Such strategies are often used in proteinpurification. This <strong>and</strong> similar strategies involving protein modification <strong>and</strong> controlledattachment currently provide the means of effective protein microarray <strong>for</strong>mationwithout compromising on protein activity.Another problem associated with protein microarrays is storage, h<strong>and</strong>ling <strong>and</strong>purification of an array of proteins. Formed microarrays may have limitedtemperature ranges <strong>and</strong> often have short shelf lives. Ramachadran at al., [134] havedeveloped a technique <strong>for</strong> the production of proteins in situ on the microarray ondem<strong>and</strong> by utilising in vitro DNA transcription <strong>and</strong> translation. ComplementaryDNA (cDNA), which is DNA reverse transcribed from mRNA whereupon the RNA1-44
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