Sensitive and selective detection of biothiols based on target-induced agglomeration of silver nanoclusters

In this work, we present a label-free biosensor for the sensing of biothiols such as cysteine, homocysteine, and glutathione. This biosensor is based on the fluorescent probe, polyethyleneimine-capped silver nanoclusters. The selective binding of silver nanoclusters to biothiols promotes the silver nanoclusters agglomeration to yield larger non-fluorescent silver nanoparticles. And the fluorescence intensity of silver nanoclusters was quenched efficiently with increasing concentration of biothiols. The other amino acids introduced to the silver nanoclusters probe solution did not quench the fluorescence of the probe as they do not have thiol group which has strong affinity to the silver nanoclusters. Thus, this biosensor allowed selectively investigation of biothiols. The as-proposed biosensor was sensitive for the detection of biothiols. The linear ranges for cysteine, homocysteine, and glutathione were 0.1-10 mu M (R-2=0.9930), 0.1-10 mu M (R-2=0.9924), and 0.5-6 mu M (R-2=0.9900), respectively. The detection limits for cysteine, homocysteine, glutathione were 42, 47, and 380 nM, respectively. The silver nanoclusters-based fluorescent biosensor provides a simple, cost-effective, and sensitive platform for the detection of biothiols. (C) 2012 Elsevier B.V. All rights reserved.