Novel Fluorescent Labels Prepared by Layer-by-Layer Assembly on Colloids for Biodetection Systems
- PDF / 63,834 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 23 Downloads / 163 Views
Novel Fluorescent Labels Prepared by Layer-by-Layer Assembly on Colloids for Biodetection Systems Wenjun Yang1, Dieter Trau1, Reinhard Renneberg1, Nai-Teng Yu1* and Frank Caruso2 1 Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, SAR Hong Kong, People’s Republic of China 2 Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam, Germany ABSTRACT Fluorescent polystyrene microparticles with different sizes were produced by the consecutive assembly of fluorescently labeled polyelectrolytes using the layer-by-layer self-assembly method. Film growth was characterized by microelectrophoresis and fluorescence microscopic image (FMI) analysis. Alternating negative and positive ζ-potentials with deposition of each successive polyelectrolyte layer demonstrated that the alternate adsorption of polyelectrolytes was achieved. FMI analysis provided direct measurement of the fluorescence intensity of single microparticles. The subsequent deposition of a protein (immunoglobulin G, IgG) layer onto the fluorescent microparticles was confirmed by a sandwich immunoassay. INTRODUCTION During the past ten years, the construction of functional multilayer films using the layer-bylayer (LbL) assembly approach introduced by Decher et al. [1] has attracted much interest in many aspects of materials research. Electrostatic interaction between the oppositely charged substrate and assembling species results in the formation of stable multilayers with unique optical, electronic or magnetic properties, depending on the functionality of the assembling species. The substrate widely used for assembling multilayer films was initially charged, flat surfaces. This was later extended to charged colloidal particles. Functional particles with controlled surface modification have recently been produced using the LbL method applied to colloids [2]. Fluorescent microparticles are widely used in biological and immunological studies [3] and different synthetic methods have been attempted for the fabrication of particles with high fluorescence output at desired emission wavelengths. Semiconductor nanocrystal core-shell composites, such as CdSe-CdS nanocrystals [4], CdSe-ZnS quantum dots [5], and hollow spheres of silica filled with fluorescein isothiocyanate (FITC) molecules [6] were all successfully synthesized and used as fluorescent markers in immunotests. Here we report the construction of fluorescent colloidal microparticles by using the LbL approach. The fluorescence intensity from individual microparticles was obtained using fluorescence microscopic image (FMI) analysis. The subsequent passive adsorption of IgG onto polyelectrolyte multilayer-coated fluorescent microparticles provides the biospecific recognition function required for the successful application of the particles in immunodetections. EXPERIMENTAL DETAILS Materials. Polystyrene (PS) particles with a negatively charged surface and 640 nm in diameter (PS640) were prepared by the method described by Furusawa et al. [7]. PS particles
Data Loading...
