| AVS 54th International Symposium | |
| Biomaterial Interfaces | Thursday Sessions |
| Session BI-ThP |
| Session: | Biomaterial Interfaces Poster Session |
| Presenter: | R. Dahint, University of Heidelberg, Germany |
| Authors: | P. Buecker, University of Heidelberg, Germany E. Trileva, University of Heidelberg, Germany M. Himmelhaus, University of Heidelberg, Germany R. Dahint, University of Heidelberg, Germany |
| Correspondent: | Click to Email |
In a recent paper,1 we presented a novel way of preparing densely packed, metal coated nanoparticle films for the label-free detection of binding events. The layer system is composed of dielectric nanoparticles, which are adsorbed onto a plain gold surface and subsequently metallized by deposition of gold colloid prior to electroless plating. Upon reflection of white light, the layers exhibit pronounced extinction peaks which shift to higher wavelengths when molecules adsorb onto the surface. For the same concentration and incubation time of octadecanethiol, an about fivefold higher red-shift of the extinction maximum was observed than reported for conventional surface plasmon resonance (SPR).2 However, as no quantitative information existed on the amount of adsorbed molecules, which may be different for our nanoparticle layers and the plain gold surfaces used in standard SPR, no clear decision could be made regarding their sensitivity towards adsorbate layer thickness or mass density. Thus, the goal of the present study was to accurately determine the mass sensitivity of the nano-composite films in order to facilitate quantitative studies of binding events. For this purpose, self-assembled monolayers of simple and ethylene glycol terminated alkanethiols with various chain lengths were prepared on the nanoparticle coated substrates. The measured red-shift of the extinction spectrum upon molecule adsorption was related to the thickness and mass density of the films as determined by X-ray photoelectron spectroscopy. Special attention was paid to the question whether sensitivity decreases with increasing film thickness, as this could limit the use of the nanoparticle layers for biosensing applications, which often involve the detection of high molecular weight molecules. Experiments on antigen/antibody interactions show that the sensitivity factors determined for thin organic films can also be used to quantify the amount of surface bound protein in immunoreactions.
1 R. Dahint, E. Trileva, H. Acunman, U. Konrad, M. Zimmer, V. Stadler, M. Himmelhaus, Biosensors & Bioelectronics, in press.
2 L. S. Jung, C. T. Campbell, J. Phys. Chem. B 2000, 104, 11168-11178.