Preparation, Microscopy, and Flow Cytometry with Excitation into Surface Plasmon Resonance Bands of Gold or Silver Nanoparticles on Aminodextran-Coated Polystyrene Beads

Abstract

Spherical polystyrene latex beads of about 2.0 µm diameter were coated with islands of silver or gold metal, about 5-200 nm in diameter, by reduction of aqueous silver or gold ions in the presence of sugar-coated polystyrene latex beads. The metal islands are held on the bead surface by a polymeric sugar derivative, aminodextran, covalently bound to the polystyrene aldehyde/sulfate bead. Images of the gold or silver nanoparticle-coated polystyrene beads, obtained with an optical microscope, show that gold, silver, and uncoated polystyrene beads can be distinguished by their different colors, red-purple, black, and colorless, respectively. Also, scanning electron micrographs of coated versus uncoated polystyrene beads show a distinct granular bead surface when metal nanostructures are present versus a smooth bead surface when they are absent. Nanoparticles of gold greater than about 50 nm in diameter on polystyrene beads showed enhanced 90°or side light scatter (resonant Rayleigh scattering) with excitation at 633 nm but no enhancement (same light scatter intensity as uncoated polystyrene beads) at excitation wavelengths of 544, 488, and 458 nm. On the other hand, nanoparticles of silver greater than about 50 nm in diameter on polystyrene beads showed enhanced 90°or side light scatter with excitation wavelengths of 458, 488, 544, and 633 nm but no enhancement with 351-365 nm excitation. Amplification of elastic scatter from both silver and gold colloids was maximally achieved with structures of 50-200 nm diameter, as shown in forward versus side scatter histograms obtained by flow cytometry. Side scatter enhancements of 2-to 10-fold were observed for gold-or silver-coated polystyrene beads over uncoated polystyrene beads of the same diameter. The origin of this wavelengthdependent, light scattering amplification that was observed by flow cytometry has been identified with excitation into surface plasmon resonance bands of gold and silver nanoparticles on polystyrene latex beads.

Exploitation of Localized Surface Plasmon Resonance

“…Colloidal gold and silver enhanced flow cytometry CD4+ and CD8+ lymphocytes [228 ] particles in molecularly imprinted polymers. [204] The polymer swells upon selective binding of the analyte, the distance between immobilized gold nanoparticles increases, and hence their T-LSPR spectrum changes.…”

SERS as a Foundation for Nanoscale, Optically Detected Biological Labels

“…Siiman and Burshteyn have demonstrated the use of Au and Ag colloidal nanoparticles deposited onto aminodextrancoated polymeric particles for cytometry applications. [17,18] The metal nanoparticles strongly amplify the side scattering signals.…”

Thermosensitive Core–Shell Particles as Carriers for Ag Nanoparticles: Modulating the Catalytic Activity by a Phase Transition in Networks

“…Recently, a number of systems have been discussed that are suitable for applications in aqueous environments. These include polymers, [10][11][12][13][14] dendrimers, [15,16] microgels, [17,18] and other colloidal systems. [19,20] In all the cases studied so far, these carrier systems only provide a suitable support for the nanoparticles and prevent them from aggregating.…”