Switchable surface coatings for control over protein absorption

Control over biomolecule interactions at interfaces is becoming an increasingly important goal for a range of scientificfields and is being intensively studied in areas of biotechno logical, biomedical and materials science. Improvement in thecontrol over materials and biomolecules is particularly important to applications such as arrays, biosensors, tissueengineering, drug delivery and ‘lab on a chip’ devices. Furthe r development of these devices is expected to be achievedwith thin coatings of stimuli responsive materials that can have their chemical properties ‘switched’ or tuned to stimulatea certain biological response such as adsorption/desorption of proteins. Switchable coatings show great potential for therealisation of spatial and temporal immobilisation of cells and biomolecules such as DNA and proteins.This study focuses on protein adsorption onto coatings of the thermosensitive polymer poly(N-isopropylacrylamide)(pNIPAM) which can exhibit low and high protein adsorption properties based on its temperature dependentconformation. At temperatures above its lower critical solution temperature (LCST) pNIPAM polymer chains arecollapsed and protein adsorbing whilst below the LCST they are hydrated and protein repellent.Coatings of pNIPAM on silicon wafers were prepared by free radical polymerisation in the presence of surface boundpolymerisable groups. Surface analysis and protein adsorptio n was carried out using X-ra y photoelectron spectroscopy,time of flight secondary ion mass spectrometry and contact angle measurements.This study is expected to aid the development of stimuli-responsive coatings for biochips and biodevices.Keywords: Surface modification, protein adsorption, radical polym erisation, stimuli-responsive polymers, biochips