title: Layer-by-layer assembly of electro-active gold nanoparticle/cytochrome c multilayers.
abstract: In this study we have tested the use of modified gold nanoparticles (GNPs) for introduction into cytochrome c (CytC) multilayer assemblies, constructed by the layer-by-layer deposition technique. For this purpose gold nanoparticles of different size are synthesized and the GNPs modified with mercaptopropionic acid (MPA). The particles are characterized by UV-vis-spectroscopy and transmission electron microscopy (TEM). The modified particles have been studied with respect to their binding capability on a CytC layer by SPR. The negatively charged particles exhibit rather fast adsorption kinetics on CytC. We can also show that CytC binds to MPA-modified gold nanoparticles. For the construction of electro-active CytC multilayers a negatively charged polyelectrolyte can be used. We demonstrated that the polyelectrolyte can be replaced by small-sized GNPs (5nm) in the multilayer assemblies, but assemblies consisting only of GNPs and CytC can be formed too. When these arrangements are prepared on gold electrodes, full electro-activity of the redox protein in the multiple layers can be obtained. CytC exhibits a formal potential of -24+/-12mV vs. Ag/AgCl. The electrochemical response is linearly increasing with the number of layers deposited, reaching a CytC surface concentration of 100pmol/cm(2) with 6 layers. The electron transfer mechanism through the layer system and the particle size influence are discussed.
authors.affiliation: Biosystems Technology, Wildau University of Applied Sciences, D-15745 Wildau, Bahnhofsstr. 1, Germany.
authors.forename: Sebastian Markus
authors.initials: SM
authors.lastname: Bonk
authors.forename: Fred
authors.initials: F
authors.lastname: Lisdat
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D045304:Cytochromes c / Q000737:chemistry*; D004563:Electrochemistry / Q000295:instrumentation*; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D020099:Coated Materials, Biocompatible; D004800:Enzymes, Immobilized; D006046:Gold; D045304:Cytochromes c