Individual nanoparticles attached to a surface can capture particles 100 times their size
Surfaces that can bind particles under dynamic conditions are crucial components in a range of technological and biological processes. In developing such surfaces scientists often borrow from nature by attaching biomolecular components to otherwise passive surfaces. Now, Maria Santore and colleagues1 at the University of Massachusetts in Amherst have revealed just how effective a wholly synthetic interface can be.
The researchers have shown that individual nanoparticles, immobilized on a surface, can reversibly trap micrometre-sized particles. The nanoparticles, which are around 10 nm in diameter and positively charged, comprise a gold core surrounded by about 500 ligands. Through a single contact, the nanoparticles can bind microparticles of silica flowing in solution, despite the fact that they are stationed on a negatively charged surface that repels the microparticles. Once bound to the surface, the silica particles can resist shear forces of up to 9 pN, but they are easily released by changes to the ionic conditions.
This ability to reversibly capture such large particles could form the basis for exceptionally sensitive detector elements, or prove useful in the manipulation of cells and bacteria.
Zhang, J. et al. Manipulating microparticles with single surface-immobilized nanoparticles. Langmuir 10.1021/la800857v (2008).
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Vaughan, O. Little and large. Nature Nanotech (2008). https://doi.org/10.1038/nnano.2008.201