Electrochemical immunosensors for personal care product development applications

This thesis describes the fabrication, characterisation and validation of two novel immunosensors for the detection of the inflammation markers nerve growth factor-β (NGF) and psoriasin (S100-A7). The initial phase of sensor construction involves the electrodeposition of polyaniline onto commercial screen-printed carbon electrodes. A classical avidin-biotin link was then used to immobilise biotinylated antibodies. Fully fabricated immunosensors were incubated with their target antigen and interrogated with AC impedance to observe the change in real (Z‘) impedance (Ohms) with respect to antigen exposure. The Z‘ impedance was found to increase over physiologically significant concentration ranges of the target antigen. The effects of non-specific antigen binding were accounted for via controls using a non-specific antigen analogue for each immunosensor. The sensors reported here, after optimisation of the fabrication procedure using the BioDot AD3200 automatic dispensing system, are capable of detecting the presence and concentration of target antigen in a commercial sample within 35 minutes with a lower limit of detection (LLD) (a response observed that is more than three times the standard deviation of the immunosensors baseline impedance measurement) of 50pg ml- 1 for NGF and 250pg ml- 1 for psoriasin. An evaluation is also presented of the competitive advantage gained by companies such as Unilever by undertaking research projects in conjunction with universities and forming other such strategic networks. As part of this EngD project, a review paper concerning antibody based sensors in the past decade was written and is now submitted ready for publishing in the peer reviewed journal 'Biosensors and Bioelectronics‘. A further two papers describing the development, characterisation and validation of the NGF and psoriasin immunosensors described within this thesis have also been submitted for publishing in 'Biosensors and Bioelectronics‘.