Polymer planar electrodes for cellular sensing

Collaborations between the fields of biomedicine, micro and nanotechnology and electronics are allowing the creation of complete lab on a chip devices, revolutionizing many routine techniques used in chemical, biological and medical research. The integration of electrochemistry is a convenient way to realize multi-analytical functions in a single miniaturized device. Electroanalytical techniques enable the study of neurochemical events ranging from exocytosis at isolated cells to in vivo neurotransmission. The ability to chemically modify electrodes has provided a powerful route to tune their performance. The scope of this thesis is to study the modifications of planar gold electrodes in order to increase the sensitivity and compatibility of the system to living cells. The focus is on the electrochemical detection, trough amperometric and voltammetric measurements of dopamine, a neurotransmitter released from PC12 cells during exocytosis. The material chosen is pyrrole because is very flexible and has shown good biocompatibilty and dopamine sensing properties. The process of electropolymerization on gold electrodes has been analyzed, both on macro and microfabricated electrodes. Different electrodes modifications were realized, changing the counterion included in the polymer and the oxidation state of the pyrrole. The electrodes were then tested in the electrochemical detection of dopamine. Compared to bare gold, the overoxidized polypyrrole with the dodecylsulfate (DS) counterion, has shown a better response in the detection of the positively charged dopamine, due to a partial negative charge formed on the polymer surface. The stability analysis of the electrodes showed a decrease in the response with time and a renewal method of the polymer has been developed. Finally a platform for chronoamperometric measurements of cellular exocytosis has been prepared and the modified electrodes compared to bare gold. Some issues arose due to the biocompatibility of DS and the triggering method to activate exocytosis. The counterion was changed to polyvinil sulfate and a successful measurement could be made, proving the functioning of the modification for cellular sensing.