Tetracarboxylic acid cobalt phthalocyanine SAM on gold:: Potential applications as amperometric sensor for H2O2 and fabrication of glucose biosensor

This report describes the applications of cobalt tetracarboxylic acid phthalocyanine (CoTCAPc) self-assembled monolayer (SAM) immobilized onto a preformed 2-mercaptoethanol (Au-ME) SAM on gold surface (Au-ME-CoTCAPc SAM) as a potential amperometric sensor for the detection of hydrogen peroxide (H,02) at neutral pH conditions. The Au-ME-CoTCAPc SAM sensor showed a very fast amperometric response time of approximately 1 s, good linearity at the studied concentration range of up to 5 mu M with a coefficient R-2 = 0.993 and a detection limit of 0.4 mu M oxidatively. Also reductively, the sensor exhibited a very fast amperometric response time (similar to 1 s), linearity up to 5 mu M with a coefficient R-2 = 0.986 and a detection limit of 0.2 mu M. The cobalt tetracarboxylic acid phthalocyamne self-assembled monolayer was then evaluated as a mediator for glucose oxidase (GOx)-based biosensor. The GOx (enzyme) was immobilized covalently onto Au-ME-CoTCAN SAM using coupling agents: N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS), and the results demonstrated a good catalytic behavior. Kinetic parameters associated with the enzymatic and mediator reactions were estimated using electrochemical versions of Lineweaver-Burk and Hanes equation, and the stability of the sensor was tested. The biosensor (Au-ME-CoTCAPc-GOx SAM) electrode showed good sensitivity (7.5 nA/mM) with a good detection limit of 8.4 mu M at 3 sigma, smaller Michaelis-Menten constant (4.8 mM from Hanes plot) and very fast response time of approximately 5 s. (c) 2006 Elsevier Ltd. All rights reserved.