Highly sensitive detection of exocytotic dopamine release using a gold-nanoparticle-network microelectrode

Here we report a new type of microelectrode sensor for single-cell exocytotic dopamine release. The new microsensor is built by forming a gold-nanoparticle (AuNP) network on a carbon fiber microelectrode. First a gold surface is obtained on a carbon fiber microdisk electrode by partially etching away the carbon followed by electrochemical deposition of gold into the pore. The gold surface is chemically functionalized with a sol-gel silicate network derived from (3-mercaptopropyl)trimethoxysilane (MPTS). A AuNP network is formed by immobilizing Au nanoparticles onto the thiol groups in the sol-gel silicate network. The AuNP-network microelectrode has been characterized by scanning electron microscopy (SEM) and steady-state voltammetry. The AuNP-network microelectrode has been used for amperometric detection of exocytotic dopamine secretion from individual pheochromocytoma (PC12) cells. The results show significant differences in the kinetic peak parameters including shorter rise time, decay time, and half-width as compared to a bare carbon fiber electrode equivalent. These results indicate AuNP-network microelectrodes possess an excellent sensing activity for single-cell exocytotic catecholamine release, specifically dopamine. Moreover, key advantageous properties inherent to bare carbon fiber microelectrodes (i.e., rigidity, flexibility, and small size) are maintained in addition to an observed prolonged shelf life stability and resistance to cellular debris fouling and dopamine polymerization.