Patterned and switchable surfaces for biomaterial applications

Chapter 5 – Surface plasmon resonance imaging of polymer microarrays5.4.3. Kinetic analysis of protein adsorption to polymer arrayThe adsorption to a polymer microarray of BSA, a globular serum protein presentin cell culture media, FN, a globular extracellular matrix (ECM) protein that isimportant for cell attachment and contains the RGD cell adhesion mediatingsequence, and CN type I, which is a protein also integral to the ECM and involvedlargely with the structural properties of the ECM, was studied by SPRi due to theimportant role played by these proteins for cell attachment in standard cell cultureconditions. For these studies, a polymer microarray was first deposited on a HDI-PEG layer. Initially, experiments were attempted to coat the SPR chips with theALAPP-PEG constructs previously described [34](section 2.2.2 and 2.2.3), however,the elevated temperature and use of the strong reducing agent NaCNBH 3 demandedby this approach led to the stripping of the gold layer from the glass SPR chips. Toovercome this problem, a new approach was developed to deposit a thin PEG layerwith relative ease. A thin ALAPP layer was deposited and incubated overnight withHDI. This activated the layer for subsequent grafting of a PEG brush layer withsimilar low fouling properties to the ALAPP-PEG layers previously described. Thisapproach is advantageous over the use of a PEGylated alkanethiol [280] as it can alsobe used to coat almost any material of choice including glass or silicon, which allowsthis coating to be readily transferred from a SPR chip to a substrate for cellattachment and outgrowth assays. Thus, this approach provides an alternative to selfassembledmonolayers of thiols or use of dextran for coating SPR chips.After the HDI-PEG layer had been deposited a resonance angle shift of 1.14° wasmeasured corresponding to a thickness of 10.6 nm assuming the layer has a refractiveindex of 1.5, as determined by Winspall curve fitting software. Initially, a polymer5-188