Gold nanoparticles-based protease assay. - Aggregation & Cleavage

Gold nanoparticles-based protease assay.
Received October 27, 2005.
Published online 2006 March 1
Cristian Guarise,* Lucia Pasquato,? Vincenzo De Filippis,? and Paolo Scrimin*?
PNAS
PubMed Central
Copyright ? 2006 by The National Academy of Sciences of the USA
*Department of Chemical Sciences and Institute for Membrane Technology?National Research Council, Padova Section, University of Padova, Via Marzolo 1, 35131 Padova, Italy;
?Department of Chemical Sciences, University of Trieste, Via Giorgieri 1, 34127 Trieste, Italy; and
?Department of Pharmaceutical Sciences, University of Padova, Via Marzolo 5, 35131 Padova, Italy
?To whom correspondence should be addressed. E-mail: paolo.scrimin@unipd.it
Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved January 10, 2006
Author contributions: L.P. and P.S. designed research; C.G. performed research; V.D.F. contributed new reagents/analytic tools; L.P., V.D.F., and P.S. analyzed data; and P.S. wrote the paper.
Abstract
We describe here a simple assay that allows the visual detection of a protease. The method takes advantage of the high molar absorptivity of the plasmon band of gold colloids and is based on the color change of their solution when treated with dithiols. We used C- and N-terminal cysteinyl derivatives of a peptide substrate exploiting its selective recognition and cleavage by a specific protease. Contrary to the native ones, cleaved peptides are unable to induce nanoparticles aggregation; hence, the color of the solution does not change. The detection of two proteases is reported: thrombin (involved in blood coagulation and thrombosis) and lethal factor (an enzyme component of the toxin produced by Bacillus anthracis). The sensitivity of this nanoparticle-based assay is in the low nanomolar range.
Keywords: lethal factor, plasmon surface band, thrombin
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