Use of a siloxane polymer for the preparation of amperometric sensors: O2 and NO sensors and enzyme sensors

An amperometric oxygen transducer for the use of an oxidase-based sensor was prepared by coating the electrode surface from an emulsion of polydimethylsiloxane (PDMS). The porous, hydrophobic PDMS layer prepared allowed the permeation of oxygen but restricted the passage of hydrogen peroxide, which made it possible to monitor the oxygen consumption through the oxidase-catalyzed reaction without interference from the hydrogen peroxide produced through the enzymatic reaction. An enzyme sensor for l-lactic acid (50 μM–0.6 mM) was fabricated by embedding a lipid-modified lactate oxidase in the PDMS layer, and used for the l-lactate determination in serum samples. The permselective PDMS-layer was also applied to the preparation of an amperometric nitric oxide sensor. The concentration of nitric oxide (20 nM–50 μM) could be measured at 0.85 V versus Ag/AgCl without serious interference from oxidizable species such as l-ascorbic acid, uric acid and acetaminophen.