Patterned Fluorescent Particles as Nanoprobes for the Investigation of Molecular Interactions

Abstract

Fluorescent colloidal particles, fabricated by depositing a thin gold film on one side of the particle, show intensity fluctuation (blinking) under an optical microscope because of their rotational Brownian motion. Interactions between molecules immobilized on the surfaces of the particle and the solid substrate restrict the rotation of the particle, thus modulating the intensity fluctuations. Because we can obtain the time-dependent rotational angle from the fluorescent intensity, we can use the intensity signals to investigate the weak interactions between unlabeled molecules by analyzing the angular distribution of the particle. To the best of our knowledge, this is the first demonstration of an optical measurement of the rotations of nanoparticles and the first attempt at using such a technique to study molecular interactions.

Directed Assembly of Nanoparticles onto Polymer‐Imprinted or Chemically Patterned Templates Fabricated by Nanoimprint Lithography

“…Hammond and co-workers [18,19] have shown an alternative to these methods that creates a combination of chemical and topographical patterns by printing polyelectrolyte multilayers which then direct the positioning of particles. Patterns obtained using any of these methods can potentially be used for photonic-bandgap devices, [20][21][22] ionic and biological sensors on surfaces, [23] molecular recognition, [24,25] single-electron transistors, [26] and high-density data-storage systems.[27]Nanoparticles have been attached to substrates using immersion in a suspension [15,18] or by procedures based on capillary forces exerted on the nanoparticles. [4,16] -2003-500120) for which financial support is gratefully acknowledged.…”

Brownian Motion in Biological Sensing

“…In addition to using intrinsic anisotropies, it is also possible to add anisotropy artificially. For example, fluorescent particles can be coated on one side with an optically opaque medium such as gold, so that the fluorescence can only be observed from one side [13,14]. The rotational motion of these half-coated fluorescent particles gives rise to a characteristic "blinking."…”

Rectification of Brownian Particles with Oscillating Radii in Asymmetric Corrugated Channels

“…Their asymmetry of (159) design gives the Janus particles unique properties of interaction and a wide variety of potential future applications. These applications include: stabilisation of liquid/liquid and liquid/gas interfaces, nanoprobes [24,25], biosensors [26], drug delivery, lab on a chip devices, tailored substrate wettability [27] and programmable nanostructures capable of self-assembly and reconguration to name but a few [23]. .…”