The binding of various single- and double-stranded DNAs onto gold and derivatized gold surfaces, and their hybridization with complementary DNA species, have been investigated using a quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). The DNA species employed were a 21-mer oligonucleotide (Mbo21), several double-stranded plasmid DNAs (7.2 kilobases) modified by incorporation of α-phosphothio-nucleotides into the ends of the linearized plasmid DNA (pPS-Sx, where x represents the number of α-phosphothio-nucleotides), and a 30-mer oligonucleotide having a mercaptohexyl group at the 5′-phosphate end (BS1-SH). Both QCM and SPR data reveal that unmodified DNA does not spontaneously adsorb onto underivatized gold surfaces from aqueous solutions. Modification of the gold surface through the attachment of an ionizable thiol compound, 2-dimethylaminoethanethiol hydrochloride (DMAET), allows DNA to adsorb through electrostatic interactions. SPR measurements confirm the presence of Mbo21 DNA on the DMAET-modified gold surface. Immobilized Mbo21, however, does not undergo hybridization. QCM and SPR data suggest that pPS-S4, pPS-S50 and BS1-SH DNA all assume a flat orientation on gold. No hybridization of single-stranded DNA to gold-immobilized pPS-S4 and pPS-S50 could be detected. In contrast 30-mer DNA binding from solution to the complement BS1-SH immobilized on gold reveals hybridization of the DNA strands.
"Although the method is very sensitive, the necessity for prior chemical modification is its obvious inherent drawback. Hence, alternative detection methods have been actively pursued in recent years, and one promising method is the adoption of surface plasmon resonance (SPR) spectroscopy in which changes in the refractive indices of the solid substrate can be correlated with the extent of hybridization of two complementary DNA strands (Georgiadis et al., 2000; Caruso et al., 1997; Peterlinz et al., 1997; Smith et al., 2001). The electrochemical method is also attracting attention as an alternative detection method since one can readily monitor the redox reactions of electroactive species once it is added as an intercalator of two complementary DNA strands (Takenaka et al., 2000). "
[Show abstract][Hide abstract] ABSTRACT: With the goal of developing a quartz crystal microbalance (QCM)-based DNA sensor, we have conducted an in situ QCM study along with fluorescence measurements using oligonucleotides (15-mer) as a model single-stranded DNA (ss-DNA) in two different aqueous buffer solutions; the sequence of 15-mer is a part of iduronate-2-sulphate exon whose mutation is known to cause Hunter syndrome, and the 15-mer is thiolated to be immobilized on the Au-coated quartz substrate. The fluorescence data indicate that the initial immobilization as well as the subsequent hybridization with a complementary strand is hardly dependent on the kind of buffer solution. In contrast, the mass increases deducible from the decrease of QCM frequency via the Sauerbrey equation are 2.7-6.2 and 3.0-4.4 times larger than the actual mass increases, as reflected in the fluorescence measurements, for the immobilization and the subsequent hybridization processes, respectively. Such an overestimation is attributed to the trapping of solvent as well as the formation of quite a rigid hydration layer associated with the higher viscosities and/or densities of the buffer solutions. Another noteworthy observation is the excessively large frequency change that occurs when the gold electrode is deposited in advance with Au nanoparticles. This clearly illustrates that the QCM detection of DNA hybridization is also affected greatly by the surface morphology of the electrode. These enlarged signals are altogether presumed to be advantageous when using a QCM system as an in situ probing device in DNA sensors.
"The changes in Df 0 for the bare electrode were a little larger than that of the dithiol modified electrode. This may result from the fact that dithiol with short-chain has some ability to dissolve the Au electrode (Caruso et al., 1997) and the changes caused by the BSA adsorption are counteracted. For the case of nanogold modified electrode, the Df 0 value was nearly two times of that for the case when no nanogold particles were used. "
[Show abstract][Hide abstract] ABSTRACT: Real-time investigation of the interaction between primaquine phosphate and bovine serum albumin by the piezoelectric quartz crystal impedance (PQCI) analysis was carried out for the first time. Three kinds of electrodes were investigated. Compared with bare gold (Au) electrode, the gold electrode self-assembled of nanogold colloids exhibits maintained biocompatibility, increased capacity and more bioactivity. Additionally, on the basis of the multi-dimensional information provided by the PQCI analysis, the real-time interaction information and the kinetics of the binding process was investigated and a response model was deduced. At 37 degrees C, the binding rate (k1), dissociation rate (k(-1)) and equilibrium constants (Ka) were 4.19x10(2) (mol l(-1))(-1) s(-1), 1.01x10(-3) s(-1) and 4.15x10(5) (mol l(-1))(-1) for the electrode modified by nanogold particles; 3.83x10(2) (mol l(-1))(-1) s(-1), 9.70x10(-4) s(-1) and 3.95x10(5) (mol l(-1))(-1) for the bare gold electrode, respectively.
Journal of Biotechnology 11/2003; 105(1-2):105-16. DOI:10.1016/S0168-1656(03)00185-8 · 2.87 Impact Factor
"After 1,6-hexanedithiol was employed as a medium to assemble to the QCM surface for 30 min, a little mass increase was observed in most cases. Some Au atoms may fall off from the QCM surface due to corrosion effect of the short-chain thiol , so that the little mass changes are reasonable. Then ð50 AE 3Þ ng out of the added 20 nm colloidal Au was immobilized because of the adsorption of Au nanoparticles onto the dithiol-modified surface. "
[Show abstract][Hide abstract] ABSTRACT: A novel amplified microgravimetric gene sensing system was developed using quartz crystal microbalance modified by gold nanoparticles anchored on its 1,6-hexanedithiol modified gold electrode surface, and ultrasensitive detection of DNA hybridization was accomplished at the level of at least 2 x 10(-16) M.
Biochemical and Biophysical Research Communications 08/2002; 295(1):14-6. DOI:10.1016/S0006-291X(02)00628-9 · 2.30 Impact Factor
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