Incorporation of a DNAzyme into Au-coated nanocapillary array membranes with an internal standard for Pb(ii) sensing

Abstract

A Pb(ii)-specific DNAzyme has been successfully incorporated into Au-coated polycarbonate track-etched (PCTE) nanocapillary array membranes (NCAMs) by thiol-gold immobilization. Incorporation of the DNAzyme into the membrane provides a substrate-bound sensor using a novel internal control methodology for fluorescence-based detection of Pb(ii). A non-cleavable substrate strand, identical to the cleavable DNAzyme substrate strand except the RNA-base is replaced by the corresponding DNA-base, is used for ratiometric comparison of intensities. The cleavable substrate strand is labeled with fluorescein, and the non-cleavable strand is labeled with a red fluorophore (Cy5 or Alexa 546) for detection after release from the membrane surface. This internal standard based ratiometric method allows for real-time monitoring of Pb(ii)-induced cleavage, as well as standardizing variations in substrate size, solution detection volume, and monolayer density. The result is a Pb(ii)-sensing structure that can be stored in a prepared state for 30 days, regenerated after reaction, and detect Pb(ii) concentrations as low as 17 nM (3.5 ppb).

Self‐Supporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating

“…[12,13] Because of reagent depletion along the pores,r educed platingr ates and inhomogeneous deposits are found. [3,4,12,13,33,36] In the case of the template membranes appliedh ere, ar eliable transport of the plating reagents to the inner surfaces is especially difficult due to the dense arrangemento fh igh-aspect-ratio pores. Beside the deposition kinetics, the seeding quality and the morphology of the plated metal films strongly affect the homogeneity and nanostructure of the resulting networks.…”

“…Prior to metal deposition, the templates were covered with Ag NPs by sensitizationw ith aS nCl 2 solution,f ollowed by activation with an ammoniac solutiono fA gNO 3 . [37] Pederson mechanistically analyzed this process on glass substrates using X-ray photoelectron spectroscopy and suggested the establishment of af irmly bound layer of Sn II during sensitization.…”

DNA as Sensors and Imaging Agents for Metal Ions

“…114 An internal standard was also introduced into the same sensors immobilized on nanocapillary array membranes to realize ratiometric fluorescence detection, which is more resistant to background fluctuation. 115 Later, microfluidic sensor devices for Pb 2+ detection were developed by conjugating the same DNAzymes on polymethylmethacrylate (PMMA) microchannel walls. 116 By immobilizing DNAzymes and substrates on microarrays, Ye’s 117 and Zhao’s 118 groups constructed sensor arrays for high throughput detection of Pb 2+ and Cu 2+ , which combined the high selectivity and sensitivity of DNAzymes and the high throughput analysis of microarrays.…”

Fluorescence sensing of intermolecular interactions and development of direct molecular biosensors

“…The ability for signal transduction on solid supports has been demonstrated for molecular beacons (Du et al, 2005;Li et al, 2001;Yao and Tan, 2004). It has also been shown that chemical sensors (Basabe-Desmonts et al, 2004), or assays involving third interactants, such as conjugated polymers (Chen et al, 1999;Liu and Bazan, 2005) or DNAzymes (Wernette et al, 2006), can be adapted to work on supports.…”