Immobilization of a catalytic DNA molecular beacon on Au for Pb(II) detection.
A Pb(II)-specific DNAzyme fluorescent sensor has been modified with a thiol moiety in order to immobilize it on a Au surface. Self-assembly of the DNAzyme is accomplished by first adsorbing the single-thiolated enzyme strand (HS-17E-Dy) followed by adsorption of mercaptohexanol, which serves to displace any Au-N interactions and ensure that DNA is bound only through the S-headgroup. The preformed self-assembled monolayer is then hybridized with the complementary fluorophore-containing substrate strand (17DS-Fl). Upon reaction with Pb(II), the substrate strand is cleaved, releasing a fluorescent fragment for detection. Fluorescence intensity may be correlated with original Pb(II) concentration, and a linear calibration was obtained over nearly four decades: 10 microM > or = [Pb(II)] > or = 1 nM. The immobilized DNAzyme is a robust system; it may be regenerated after cleavage, allowing multiple sensing cycles. In addition, drying of fully assembled DNAzyme before reaction with Pb(II) does not significantly affect analytical performance. These results demonstrate that, in comparison with solution-based schemes, immobilization of the DNAzyme sensor onto a Au surface lowers the detection limit (from 10 to 1 nM), maintains activity and specificity, and allows sensor regeneration and long-term storage. Realization of Pb(II) detection through an immobilized DNAzyme is the first important step toward creation of a stand-alone, portable Pb(II) detection device such as those immobilizing DNAzyme recognition motifs in the nanofluidic pores of a microfluidic-nanofluidic hybrid multilayer device.
Swearingen
Carla B
CB
Beckman Institute for Advanced Science and Technology and Department of Chemistry, University of Illinois at Urbana--Champaign, 405 North Mathews Avenue, Urbana, Illinois 61801, USA.
Wernette
Daryl P
DP
Cropek
Donald M
DM
Lu
Yi
Y
Sweedler
Jonathan V
JV
Bohn
Paul W
PW
D015374:Biosensing Techniques / Q000379:methods*; D021881:DNA, Catalytic / Q000737:chemistry*; D004800:Enzymes, Immobilized; D005453:Fluorescence; D006046:Gold / Q000737:chemistry*; D007854:Lead / Q000032:analysis*; D012680:Sensitivity and Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry
D021881:DNA, Catalytic; D004800:Enzymes, Immobilized; D013438:Sulfhydryl Compounds; D007854:Lead; D006046:Gold