Biofunctionalized indigo-nanoparticles as biolabels for the generation of precipitated visible signal in immunodipsticks.
ABSTRACT A novel class of organic nanoparticles as biolabels that can generate an instant visible signal was applied to immunodipsticks. A new principle for signal generation based on hydrolysis of colourless signal precursor molecules to produce coloured signal molecules followed by signal precipitation and localization was demonstrated. The nanoparticle biolabels were applied to sandwich immunoassays for the detection of mouse immunoglobulin G (M IgG). In the presence of M IgG, a nanoparticle-immunocomplex was formed and bound on the test zone immobilized with goat anti M IgG (Gt α M IgG). A blue line was developed on the test zone upon the addition of a signal developing reagent. An optical signal could be simply assessed using naked eyes or quantified using a reading device. The lowest visible signal that could be observed using naked eyes was found to be 1.25 μg L(-1) M IgG. The nanoparticle biolabel also showed a better sensitivity (signal-to-noise ratio) compared with the conventional colloidal gold biolabel. This novel class of organic nanoparticles offers an alternative biolabel system for the development of point-of-care immunodipsticks.
- SourceAvailable from: Dieter Trau[show abstract] [hide abstract]
ABSTRACT: We report on an immobilization strategy utilizing layer-by-layer encapsulated microparticles of enzymes within a nanoscale polyelectrolyte film. Encapsulation of glucose oxidase (GOD) microparticles was achieved by the sequential adsorption of oppositely charged polyelectrolytes onto the GOD biocrystal surface. The polyelectrolyte system polyallylamine/polystyrene sulfonate was used under high salt conditions to preserve the solid state of the highly water soluble GOD biocrystals during the encapsulation process. The resulting polymer multilayer capsule of about 15 nm wall thickness is permeable for small molecules (glucose), but non-permeable for macromolecules thus preventing the enzyme from leakage and at the same time shielding it from the outer environment e.g., from protease or microbial activity. Decrease of the buffer salt concentration leads to the dissolution of the enzyme under formation of mu-bioreactors. The spherical mu-bioreactors are bearing an extremely high loading of biocompound per volume. Encapsulated GOD was subsequently used to construct a biosensor by nanoengineered immobilisation of mu-bioreactor capsules onto an electrode surface. The presented approach demonstrates a general method to encapsulate highly soluble solid biomaterials and an immobilization strategy with the potential to create highly active thin and stable films of biomaterial.Biosensors and Bioelectronics 11/2003; 18(12):1491-9. · 5.44 Impact Factor