Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applications1.3. Surfaces with switchable propertiesThe development of switchable surfaces is a key enabling advancement forbiodevice applications, including biomaterials and in particular tissue engineeringand cell microarrays. Switchability, in essence, enables temporal control, addinganother dimension to controlled biomolecular manipulation. These types of surfaceshave already been instrumental in gaining a better understanding of biomolecularsurfaces at the solid-liquid interface. Typically, DNA adsorption and desorption istemporally controlled by electrochemistry due to the polycationic nature of thisbiomolecule. On the other hand, a number of strategies to reversibly control cell andprotein adhesion have been investigated and typically involve the use of hydrogelsand switching of these polymers from a hydrophobic to hydrophilic state bytemperature shifts about the lower critical solution temperature (LCST). Othertriggers such as pH, specific ligand-receptor interactions and light have beeninvestigated to evoke changes in hydrogel properties, including optical and densitychanges [70, 102-104].1.3.1. Switchable DNA adsorption and desorptionOf great interest in terms of DNA surface manipulation are surfaces that canswitch between a positive and negative surface charge, instigating temporal controlover DNA adsorption and desorption. This is particularly important for TCMswhereupon adsorbed DNA must be released in order to be internalised by cells [1].The ability to electro-stimulate the desorption of DNA has been studied extensivelyon gold [18, 105-108]. Wang et al., [105] demonstrated small amounts of DNA werereleased at voltages as low as -0.2 V, however, maximised DNA release wasobserved at -1.2 V. Jiang et al., [109] demonstrated by AFM analysis that the surface1-31