Amperometric immunosensor for probing complement III (C3) based on immobilizing C3 antibody to a nano-Au monolayer supported by sol–gel-derived carbon ceramic electrode

An electrochemical immunosensor based on nano-size particulate gold (nano-Au) monolayer as sensing interface has been developed for probing complement III (C3). The thiol functional group-derived carbon ceramic electrode (CCE) was firstly constructed using (3mercaptopropyl) trimethoxy silane (MPTMOS) as sol–gel monomer. The stable nano-Au monolayer was obtained resulting from covalent combination between nano-Au and thiol group on the surface of CCE. The nano-Au monolayer formed was utilized as a sensing platform for the immobilization of C3 antibody (anti-C3) and subsequent immunoreaction. A competitive immunoassay format was adopted with horseradish peroxidase (HRP)–C3 as a tracer, hydroquinone and hydrogen peroxide as the enzymatic substrates. The dynamic concentration range for C3 is 0.08–5.6 (mu)g ml^-1. The feasibility of regenerating nano-Au monolayer for consecutive assays was demonstrated by a simple chemical treatment after each determination. The high stability of formed nano-Au monolayer, readily adsorptive immobilization of antibody on nano-Au monolayer, efficient activity retention of loading immunoreactants as well as the simple operation for the formation of nano-Au monolayer make proposed methodology an attractive alternative for the designing new-type immunosensors.