STUDY OF LAYER BY LAYER ASSEMBLY ON GOLD NANOPARTICLES. A NANOPARTICLE-BASED GLUCOSE BIOSENSOR AS AN APPLICATION

PABLO SCODELLER, VICTORIA FLEXER, VERONICA IELMINI, ALEX FAINSTEIN, NICOLAS TOGNALLI, HORACIO TROIANI, ERNESTO J. CALVO

Reñaca, Chile

Workshop; PASI "NOVEL MATERIALS FOR MICRO AND NANOELECTRONICS"; 2007

We have studied the self assembly of a cationic polymer and an anionic enzime on gold nanoparticles with the goal of fabricating a nanoparticle-based glucose biosensor. Using the layer by layer technique, Glucose Oxidase (GOx) and a redox polymer, poly(allylamine), modified with an Os-pyridine-bipyridine complex (PAH-Os) have been deposited on 10 nm gold nanoparticles. The nanoparticles are derivatized with mercaptopropanesulfonate (MPS). This is accomplished by simultaneous addition of MPS and sodium citrate to the gold solution during the synthesis. A strong bond between the colloid-stabilising molecule and the gold nanoparticle, such as the Au-S covalent bond, is crucial for preventing dewrapping of polymers in the subsequent deposition steps. The UV-Vis spectra after each deposition step show a slight red shift in the plasmon peak and no broadening of the plasmon band; this indicates a change in the dielectric constant of the medium surrounding the nanoparticle (polymer deposition) and absence of polymer-induced nanoparticle aggregation, respectively. The PAH-Os works as a "molecular wire", transfering electrons from the enzyme to the substrate. This amperometric biosensor (with two GOx layers and three PAH-Os layers) was tested. The nanoparticles were adsorbed onto a gold working electrode and a catalytic current was detected in the voltamograms. We have probed the sensor spectroscopically, thus eliminating the need for wiring. The Osmium complex (with Os(II)) posseses a characteristic Resonant Raman scattering signal. Once the Osmium is oxidised to Os(III) this Raman signal is significantly quenched. When glucose is later added, Osmium is reduced back to Os(II), recovering the raman signal.