2015 Fiscal Year Research-status Report
An Ultra-Sensitive and Ultra-Selective Electronic Nose System
Project/Area Number |
15K16318
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Research Institution | Tohoku University |
Principal Investigator |
Banan Ramin 東北大学, 原子分子材料科学高等研究機構, 助手 (30728465)
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Project Period (FY) |
2015-04-01 – 2017-03-31
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Keywords | biosensor / nanotechnology / electronic nose |
Outline of Annual Research Achievements |
Substantial progress has been made in fabrication and characterization of Si microprobe arrays during FY2015. Below summarizes our achievements so far: Arrays of silicon microprobes were successfully developed with controlled probe-to-probe spacing, length, and tip geometry. Between the two proposed fabrication methods, the bottom-up vapor-liquid-solid (VLS) and the top-down etching methods, we chose to proceed with the former, as expected results were obtained meeting the project requirements. All the fabrication process steps were carried out at the Electronics-Inspired Interdisciplinary Research Institute in Toyohashi University of Technology. Therefore, we would like to acknowledge the contribution and help we received from the researchers at that institute, namely, Hideo Oi, Yoshihiro Kubota, Shota Yamagiwa, and Takeshi Kawano. (1) Si needles with tip curvature of less than 3 μm and length of 200 μm were fabricated. Such sharp tips are advantageous as they can easily penetrate live tissue and make noninvasive biosensing possible. (2) One of the major hurdles of the fabrication process was to prevent mutli-mode growth of the probes. In some cases, instead of a single Si microwire, multiple branched wires were grown from the Au/Si sites patterned on the Si substrates through photolithography. Important parameters to tweak were the growth temperature and pressure. These parameters were adjusted along with the Au dot size and substrate dopant to achieve a uniform mixture of Au and Si at the growth sites required to produce single-mode probes.
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Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
After the development of reliable and durable arrays of Si probes, it was imperative to test their biocompatibility by interfacing the structures with cell lines and living tissues. We decided to use C2C12 skeletal muscle cells because of their capability to form contractile muscle tissue upon maturation. C2C12 tissue is not only useful in biosensing studies targeting certain chemicals such as reactive oxygen species (ROS) but also can incorporate the piezoresistive property of Si microprobes as a platform for quantification of muscle fiber contraction. In addition, myotubes can be electrically stimulated using the probes with high spatiotemporal resolution. By stimulating the tissue at micrometer scale, we can detect the changes in the levels of biochemicals locally using the same microprobes. As a result a multipurpose platform (e-nose, contractility sensos, and localized electrical simulator) was introduced.
(1) C2C12 myoblasts were seeded on the Si microwire substrates soaked in a cell culture medium. Upon confluency, the medium was replaced with differentiation medium that triggers formation of myotubes. Single nucleus myoblasts fused into eachother creating contractile myotubes.
(2) We performed immunostaining experiments to quantity the density of C2C12 myoblasts on the substrate and the location of myotubes. Interestingly, well-developed muscle tissue formed on the microwire array. The tissue firmly attached to the trunk of Si microwires. In addition we showed that myogenesis (formation of myotubes) is enhanced at the tip of the microprobes.
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Strategy for Future Research Activity |
In line with exploring the biosensing performance of Au-terminated Si probes for e-nose applications, we developed a biosensor platform to detect and measure the rate of superoxide anion generation from live tissue. Electrodes made of nanoporous gold were functionalized with a superoxide sensitive protein and then interfaced with C2C12 cell line. Upon stimulation with a tumor promoting drug, phorbol 12-myristate 13-acetate (PMA), the cells released superoxide anions in nano-molar quantities which could be measured by our sensor. Such ultra-high sensitivity is achieved due to the high surface-to-volume ratio of nanoporous gold electrode as compared to standard nonporous gold electrodes.
(1) In the upcoming year, we intend to implement the technology of nanoporous gold-based biosensor on the tips of Au-terminated Si microprobes. To this end, we will use the microprobes containing nanoprous gold at their tips and functionalize them with various enzymes to target different biochemicals. We have already, demonstrated formation of such nanoporous film of gold at the probe tips. However, the repeatability of the fabrication process needs to be improved. Also using finite element methods, we will estimate the local amplitude of electric field at the apex of the Si microprobes.
(2) In addition, we are in the process of designing experiments for localized electrical stimulation of skeletal muscle tissue and contractility measurements. In order to track the displacement of myotubes we need to mark the cells using a noninvasive fluorescent dye.
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Causes of Carryover |
A sum of \170,577 has been left over from the previous fiscal year, as the travel expenses I have incurred along with the price of the PMU until purchased from Keithley, and the other items purchased were not exactly \2,990,000.
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Expenditure Plan for Carryover Budget |
I plan to use the left over amount to purchase consumable chemicals and other materials for the project during the upcoming fiscal year.
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Research Products
(2 results)