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ABSTRACT: The integration of biological molecules with semiconducting materials such as silicon and diamond has great potential for the development of new types of bioelectronic devices, such as biosensors and bioactuators. We have investigated the electrical properties of the antibody-antigen modified diamond and silicon surfaces using electrical impedance spectroscopy (EIS). Frequency dependent measurements at the open-circuit potential show: (a) significant changes in impedance at frequency >10(4) Hz when the surface immobilized IgG was exposed to anti-IgG, and (b) only little or no change when exposed to anti-IgM. Mott-Schottky measurements at high frequency (200 kHz) show that the impedance is dominated by the space charge layer of the semiconducting substrates. Silicon surfaces modified in a similar manner to the diamond surface are compared; n-type and p-type samples show complementary behavior, as expected for a field effect. We also show it is possible to directly observe antigen-antibody interaction at a fixed frequency in real time, and with no additional labeling.
The Analyst 04/2007; 132(4):296-306. · 4.23 Impact Factor
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ABSTRACT: Recent studies have shown that semiconductor surfaces such as silicon and diamond can be functionalized with organic monolayers, and that these monolayer films can be used to tether biomolecules such as DNA to the surfaces. Electrical measurements of these interfaces show a change in response to DNA hybridization and other biological binding processes, but the fundamental nature of the electrical signal transduction has remained unclear. We have explored the electrical impedance of polycrystalline and single-crystal diamond surfaces modified with an organic monolayer produced by photochemical reaction of diamond with 1-dodecene. Our results show that, by measuring the impedance as a function of frequency and potential, it is possible to dissect the complex interfacial structure into frequency ranges where the total impedance is controlled by the molecular monolayer, by the diamond space-charge region, and by the electrolyte. The results have implications for understanding the ability to use molecularly modified semiconductor surfaces for applications such as chemical and biological sensing.
The Journal of Physical Chemistry B 06/2005; 109(17):8523-32. · 3.70 Impact Factor
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ABSTRACT: We have investigated the frequency-dependent interfacial electrical properties of nanocrystalline diamond films that were covalently linked to DNA oligonucleotides and how these properties are changed upon exposure to complementary and noncomplementary DNA oligonucleotides. Frequency-dependent electrical measurements at the open-circuit potential show significant changes in impedance at frequencies of >10(4) Hz when DNA-modified diamond films are exposed to complementary DNA, with only minimal changes when exposed to noncomplementary DNA molecules. Measurements as a function of potential show that at 10(5) Hz, the impedance is dominated by the space-charge region of the diamond film. DNA molecules hybridizing at the interface induce a field effect in the diamond space-charge layer, altering the impedance of the diamond film. By identifying a range of impedances where the impedance is dominated by the diamond space-charge layer, we show that it possible to directly observe DNA hybridization, in real time and without additional labels, via simple measurement of the interfacial impedance.
Langmuir 08/2004; 20(16):6778-87. · 4.19 Impact Factor
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ABSTRACT: Recently developed DNA-modified diamond surfaces exhibit excellent chemical stability to high-temperature incubations in biological buffers. The stability of these surfaces is substantially greater than that of gold or silicon surfaces, using similar surface attachment chemistry. The DNA molecules attached to the diamond surfaces are accessible to enzymes and can be modified in surface enzymatic reactions. An important application of these surfaces is for surface invasive cleavage reactions, in which target DNA strands added to the solution may result in specific cleavage of surface-bound probe oligonucleotides, permitting analysis of single nucleotide polymorphisms (SNPs). Our previous work demonstrated the feasibility of performing such cleavage reactions on planar gold surfaces using PCR-amplified human genomic DNA as target. The sensitivity of detection in this earlier work was substantially limited by a lack of stability of the gold surface employed. In the present work, detection sensitivity is improved by a factor of approximately 100 (100 amole of DNA target compared with 10 fmole in the earlier work) by replacing the DNA-modified gold surface with a more stable DNA-modified diamond surface.
Biopolymers 05/2004; 73(5):606-13. · 2.87 Impact Factor
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Wensha Yang,
Orlando Auciello,
James E Butler,
Wei Cai,
John A Carlisle,
Jennifer E Gerbi,
Dieter M Gruen,
Tanya Knickerbocker,
Tami L Lasseter,
John N Russell,
Lloyd M Smith,
Robert J Hamers
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ABSTRACT: Diamond, because of its electrical and chemical properties, may be a suitable material for integrated sensing and signal processing. But methods to control chemical or biological modifications on diamond surfaces have not been established. Here, we show that nanocrystalline diamond thin-films covalently modified with DNA oligonucleotides provide an extremely stable, highly selective platform in subsequent surface hybridization processes. We used a photochemical modification scheme to chemically modify clean, H-terminated nanocrystalline diamond surfaces grown on silicon substrates, producing a homogeneous layer of amine groups that serve as sites for DNA attachment. After linking DNA to the amine groups, hybridization reactions with fluorescently tagged complementary and non-complementary oligonucleotides showed no detectable non-specific adsorption, with extremely good selectivity between matched and mismatched sequences. Comparison of DNA-modified ultra-nanocrystalline diamond films with other commonly used surfaces for biological modification, such as gold, silicon, glass and glassy carbon, showed that diamond is unique in its ability to achieve very high stability and sensitivity while also being compatible with microelectronics processing technologies. These results suggest that diamond thin-films may be a nearly ideal substrate for integration of microelectronics with biological modification and sensing.
Nature Material 01/2003; 1(4):253-7. · 32.84 Impact Factor
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Wensha Yang,
Orlando Auciello,
James E. Butler,
Wei Cai,
John A. Carlisle,
Jennifer E. Gerbi,
Dieter M. Gruen,
Tanya Knickerbocker,
Tami L. Lasseter,
John N. Russell Jr,
Lloyd M. Smith,
Robert J. Hamers
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ABSTRACT: Nanocrystalline diamond thin films of sub-micron thickness have been covalently modified with DNA oligonucleotides. Quantitative studies of hybridization of surface-bound oligonucleotides with fluorescently tagged complementary and non-complementary oligonucleotides were performed. The results show no detectable nonspecific adsorption, with extremely good selectivity between matched and mismatched sequences. Impedance spectroscopy measurements were made of DNA-modified boron-doped nanocrystalline diamond films. The results show that exposure to non-complementary sequences induce only small changes in impedance, while complementary DNA sequences produce a pronounced decrease in impedance. The combination of high stability, selectivity, and the ability to directly detect DNA hybridization via electrical means suggest that diamond may be an ideal substrate for continuously-monitoring biological sensors.
MRS Proceedings. 12/2001; 737.
