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RESEARCH Background Miniaturized
devices have had a significant impact on our society in revolutionizing the
electronics industry. A similar trend of size-reduction is emerging in the
health care industry to produce small bioanalytical devices for disease
diagnosis, novel methods for drug delivery to treat diseases, and
microfabricated platforms for studying microorganisms. Nanostructured
materials, in particular, have revolutionized capabilities of biotic-abiotic
interfaces in various biomedical devices, including affinity biosensors,
implantable neural electrodes, and drug delivery platforms. Despite the
recent research on these materials, significant challenges remain in
controlling material properties, interfacing nanocomponents with instrumentation,
and engineering their interaction with biological systems. Prior
to joining UC Davis as a faculty member, Seker’s dissertation focused on
microfabrication and thermo-mechanical characterization of nanoporous gold1,2, a promising candidate for
functional surface coatings due to its controllable morphology, electrical
conductivity, and well-studied gold surface chemistry3. In
addition, he studied mass-transport in porous media4 and
synthesized a composite material that exhibits very low elastic modulus and
high electrical conductivity5 –
highly desirable attributes for flexible electrodes. As a postdoctoral
researcher in chemistry department, his research extended to the study of
biomolecule-surface interactions6 and
development of novel flow control methods in microfluidic circuits7,8. As a research associate at Center for
Engineering in Medicine (CEM), he began to utilize nanoporous metals for
developing planar multiple electrode arrays for electrophysiology
applications9. The
overarching objective of our group is to utilize our expertise at the
intersection of nanoporous metal synthesis, microfluidics, and device
engineering to overcome challenges in the evolution of miniaturized devices
relevant to microelectronics and life sciences. We gratefully acknowledge
support from National Science Foundation (1512745
& 1454426),
UC Lab Fees Research Program (12-LR-237197),
National Institutes of Health (T32-GM008799
& R21EB024635),
and UC Davis Research Investments in the Sciences and Engineering (RISE). The
projects listed below are a selected group of our current research thrusts.
Please contact Prof. Erkin Şeker for
more information. |
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Main Research Thrusts |
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Nanostructured
Electrochemical Biosensors An
integral component of a biosensor platform with an electrochemical read-out
is the sensor element that interfaces biomolecular detection probes with
instrumentation electronics. Sensor performance, on both biomolecular and
electrical levels, is strongly influenced by sensor coating properties, such
as morphology, surface chemistry, and metallurgy. While nanostructured
materials have shown significant promise in enhancing the performance of
these sensors, the underlying mechanisms for this enhancement are not fully
understood. Currently,
we are fabricating novel nanostructured electrodes to provide insight into
how nanoscale features enhance sensitive measurement and purification of
nucleic acids in complex biological samples10-14. The fundamental studies
will reveal a set of design rules for the development of nanostructured
electrochemical sensor elements and assist technological advancements in food
safety, water quality, and medical diagnostics. |
Tunable nanoporous
gold morphology |
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Multifunctional
Biomedical Device Coatings There
is a significant need for medical devices that can both monitor and modulate
physiological activity, while minimizing adverse tissue response to an
implant. This is particularly important in neurological disorders, since
neurons exhibit both electrical and chemical activity as a part of their
normal function and implanted neural interfaces typically suffer from
deteriorating device performance due to tissue-material interactions. Currently,
we are creating multifunctional neural electrodes that incorporate tunable
drug delivery and topographical cues. Specifically, we focus on the
fundamentals of molecular release from nanoporous metals15-17 and cell-surface
interactions as a function of nano-topography18,19. We expect that these
efforts will translate into advanced neural interfaces for closed-loop
control of neurological disorders such as epilepsy. |
Astrocyte adhering
onto porous surface |
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Libraries
of Nanoporous Metal Morphologies In
the studies described above, nanoporous metal attributes (e.g.,
characteristic feature size, effective surface area, electrical conductivity,
and surface chemistry) translate into several key device performance metrics:
(i) limit of detection, sensitivity, and biofouling-resilience of affinity
biosensors; (ii) biocompatibility, signal-to-noise ratio, and charge
injection capacity of neural electrodes; and (iii) loading capacity, release
kinetics, and on demand release in drug delivery platforms. Currently,
we are developing techniques to modulate pore morphology and surface
chemistry with the goal of creating on-chip libraries that display multiple
material attributes14,20-23. We expect these libraries
to allow for high-throughput study of structure-property relationships in the
context of biomolecule-tissue-material interactions, as well as other
applications such as catalysis and energy storage. |
Freestanding
nanoporous gold beam array |
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Reference Papers 1 Seker,
E., Gaskins, J., Bart-Smith, H., Zhu, J., Reed, M., Zangari, G., Kelly, R.
& Begley, M. The effects of post-fabrication annealing on the mechanical
properties of freestanding nanoporous gold structures. Acta Materialia 55:4593 (2007). 2 Seker, E., Reed, M. L. & Begley, M.
R. A thermal treatment approach to reduce microscale void formation in
blanket nanoporous gold films. Scripta
Materialia 60:435 (2009). 3 Seker, E., Reed, M. & Begley, M.
Nanoporous Gold: Fabrication, Characterization, and Applications. Materials 2:2188 (2009). 4 Seker, E., Begley, M., Reed, M. &
Utz, M. Kinetics of capillary wetting in nanoporous films in the presence of
surface evaporation. Applied Physics
Letters 92:013128 (2008). 5 Seker, E., Reed, M., Utz, M. &
Begley, M. Flexible and conductive bilayer membranes of nanoporous gold and
silicone: Synthesis and characterization. Applied
Physics Letters 92:154101 (2008). 6 Huang, L., Seker, E., Landers, J.,
Begley, M. & Utz, M. Molecular Interactions in Surface-Assembled
Monolayers of Short Double-Stranded DNA. Langmuir
26:11574 (2010). 7 Leslie, D., Easley, C., Seker, E.,
Karlinsey, J., Utz, M., Begley, M. & Landers, J. Frequency-specific flow
control in microfluidic circuits with passive elastomeric features. Nature Physics 5:231 (2009). 8 Seker, E., Leslie, D., Haj-Hariri, H.,
Landers, J., Utz, M. & Begley, M. Nonlinear pressure-flow relationships
for passive microfluidic valves. Lab on
a Chip 9:2691 (2009). 9 Seker, E., Berdichevsky, Y., Begley, M.,
Reed, M., Staley, K. & Yarmush, M. The fabrication of low-impedance
nanoporous gold multiple-electrode arrays for neural electrophysiology
studies. Nanotechnology 21:125504
(2010). 10 Daggumati, P., Matharu, Z. & Seker, E. Effect
of Nanoporous Gold Thin Film Morphology on Electrochemical DNA Sensing. Analytical Chemistry 87:8149 (2015). 11 Daggumati, P., Matharu, Z., Wang, L. &
Seker, E. Biofouling-resilient nanoporous gold electrodes for DNA sensing. Analytical Chemistry 87:8618 (2015). 12 Daggumati, P., Appelt, S., Matharu, Z.,
Marco, M. & Seker, E. Sequence-Specific Electrical Purification of
Nucleic Acids with Nanoporous Gold Electrodes. Journal of the American Chemical Society 138:7711 (2016). 13 Zhou, J. C., Feller, B., Hinsberg, B.,
Sethi, G., Feldstein, P., Hihath, J., Seker, E., Marco, M., Knoesen, A. &
Miller, R. Immobilization-mediated reduction in melting temperatures of
DNA–DNA and DNA–RNA hybrids: Immobilized DNA probe hybridization studied by
SPR. Colloids and Surfaces A:
Physicochemical and Engineering Aspects 481:72 (2015). 14 Matharu, Z., Daggumati, P., Wang, L.,
Dorofeeva, T. S., Li, Z. & Seker, E. Nanoporous-Gold-Based Electrode
Morphology Libraries for Investigating Structure–Property Relationships in
Nucleic Acid Based Electrochemical Biosensors. ACS Applied Materials & Interfaces 9:12959 (2017). 15 Seker, E., Berdichevsky, Y., Staley, K. J.
& Yarmush, M. L. Microfabrication-Compatible Nanoporous Gold Foams as
Biomaterials for Drug Delivery. Advanced
Healthcare Materials 1:172 (2012). 16 Kurtulus, O., Daggumati, P. & Seker, E.
Molecular Release from Patterned Nanoporous Gold Thin Films. Nanoscale 6:7062 (2014). 17 Polat, O. & Seker, E. Halide-Gated
Molecular Release from Nanoporous Gold Thin Films. The Journal of Physical Chemistry C 119:24812 (2015). 18 Chapman, C. A., Chen, H., Stamou, M.,
Biener, J., Biener, M. M., Lein, P. J. & Seker, E. Nanoporous Gold as a
Neural Interface Coating: Effects of Topography, Surface Chemistry, and
Feature Size. ACS Applied Materials
& Interfaces 7:7093 (2015). 19 Chapman, C. A. R., Wang, L., Chen, H.,
Garrison, J., Lein, P. J. & Seker, E. Nanoporous Gold Biointerfaces:
Modifying Nanostructure to Control Neural Cell Coverage and Enhance
Electrophysiological Recording Performance. Advanced Functional Materials 27:1604631 (2017). 20 Chapman, C. A., Daggumati, P., Gott, S. C.,
Rao, M. P. & Seker, E. Substrate topography guides pore morphology
evolution in nanoporous gold thin films. Scripta
Materialia 110:33 (2016). 21 Chapman, C. A., Wang, L., Biener, J.,
Seker, E., Biener, M. M. & Matthews, M. J. Engineering on-chip nanoporous
gold material libraries via precision photothermal treatment. Nanoscale 8:785 (2016). 22 Dorofeeva, T. S., Matharu, Z., Daggumati,
P. & Seker, E. Electrochemically Triggered Pore Expansion in Nanoporous
Gold Thin Films. The Journal of
Physical Chemistry C 120:4080 (2016). 23 Dorofeeva, T. S. & Seker, E. In Situ
Electrical Modulation and Monitoring of Nanoporous Gold Morphology. Nanoscale 8:19551 (2016). |