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May 2010

Volume 81, Issue 5, Articles (05xxxx)

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back to top Biology and Medicine

Efficient micromixing of a highly viscous biosample with water using orbital shaking and microchannels

Liang Yuan, Yuan F. Zheng, and Weidong Chen

Rev. Sci. Instrum. 81, 054301 (2010); http://dx.doi.org/10.1063/1.3422244 (9 pages)

Online Publication Date: 6 May 2010

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Micromixing of a highly viscous biosample with water using orbital shaking and microchannels is considered. Existing methods mix biosamples by only shaking microwells or by specially designed microstirrers which are ineffective or inapplicable for highly viscous materials, let alone small volumes at microliter or nanoliter levels. Our method mixes a viscous biosample with water in microwells using orbital shaking plus an innovative block which divides the microwells into two compartments and is built in with microchannels. The mixing method with the block in the microwell is efficient compared to mixing in the microwell without the block. In this paper, the design of the block is presented, the model of the flow of the biosamples in the microchannel is developed, the Reynolds number of the flow in the microchannel is calculated, and the dynamics of the mixing process is analyzed. Furthermore, a miniature wireless video sensor system is used to observe the mixing process which verifies the model of the flow in the analysis. Finally, x-ray diffraction experiments on mixing monoolein with water are presented. In each trial, x-ray diffraction is used to evaluate the results of mixing which confirms that the proposed approach is effective for mixing a highly viscous biosample with water.
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87.80.Ek Mechanical and micromechanical techniques
47.51.+a Mixing
47.85.Np Fluidics
07.10.Cm Micromechanical devices and systems
87.14.E- Proteins

33S nuclear magnetic resonance spectroscopy of biological samples obtained with a laboratory model 33S cryogenic probe

Fumio Hobo, Masato Takahashi, Yuta Saito, Naoki Sato, Tomoaki Takao, Seizo Koshiba, and Hideaki Maeda

Rev. Sci. Instrum. 81, 054302 (2010); http://dx.doi.org/10.1063/1.3424853 (7 pages) | Cited 1 time

Online Publication Date: 14 May 2010

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33S nuclear magnetic resonance (NMR) spectroscopy is limited by inherently low NMR sensitivity because of the quadrupolar moment and low gyromagnetic ratio of the 33S nucleus. We have developed a 10 mm 33S cryogenic NMR probe, which is operated at 9–26 K with a cold preamplifier and a cold rf switch operated at 60 K. The 33S NMR sensitivity of the cryogenic probe is as large as 9.8 times that of a conventional 5 mm broadband NMR probe. The 33S cryogenic probe was applied to biological samples such as human urine, bile, chondroitin sulfate, and scallop tissue. We demonstrated that the system can detect and determine sulfur compounds having SO42− anions and –SO3− groups using the 33S cryogenic probe, as the 33S nuclei in these groups are in highly symmetric environments. The NMR signals for other common sulfur compounds such as cysteine are still undetectable by the 33S cryogenic probe, as the 33S nuclei in these compounds are in asymmetric environments. If we shorten the rf pulse width or decrease the rf coil diameter, we should be able to detect the NMR signals for these compounds.
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87.61.-c Magnetic resonance imaging
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Estimation method of finger tapping dynamics using simple magnetic detection system

Akihiko Kandori, Yuko Sano, Tsuyoshi Miyashita, Yoshihisa Okada, Masataka Irokawa, Keisuke Shima, Toshio Tsuji, Masaru Yokoe, and Saburo Sakoda

Rev. Sci. Instrum. 81, 054303 (2010); http://dx.doi.org/10.1063/1.3427583 (6 pages)

Online Publication Date: 18 May 2010

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We have developed the simple estimation method of a finger tapping dynamics model for investigating muscle resistance and stiffness during tapping movement in normal subjects. We measured finger tapping movements of 207 normal subjects using a magnetic finger tapping detection system. Each subject tapped two fingers in time with a metronome at 1, 2, 3, 4, and 5 Hz. The velocity and acceleration values for both the closing and opening tapping data were used to estimate a finger tapping dynamics model. Using the frequency response of the ratio of acceleration to velocity of the mechanical impedance parameters, we estimated the resistance (friction coefficient) and compliance (stiffness). We found two dynamics models for the maximum open position and tap position. In the maximum open position, the extensor muscle resistance was twice as high as the flexor muscle resistance and males had a higher spring constant. In the tap position, the flexor muscle resistance was much higher than the extensor muscle resistance. This indicates that the tapping dynamics in the maximum open position are controlled by the balance of extensor and flexor muscle friction resistances and the flexor stiffness, and the flexor friction resistance is the main component in the tap position. It can be concluded that our estimation method makes it possible to understand the tapping dynamics.
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87.80.-y Biophysical techniques (research methods)
87.19.rs Movement
87.19.Ff Muscles

Combined system of fluorescence diffuse optical tomography and microcomputed tomography for small animal imaging

Xiaoquan Yang, Hui Gong, Guotao Quan, Yong Deng, and Qingming Luo

Rev. Sci. Instrum. 81, 054304 (2010); http://dx.doi.org/10.1063/1.3422252 (8 pages) | Cited 8 times

Online Publication Date: 25 May 2010

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We developed a dual-modality system that combines fluorescence diffuse optical tomography (fDOT) and flat panel detector-based microcomputed tomography (micro-CT) to simultaneously reveal molecular and structural information in small animals. In fDOT, a 748 nm diode laser was used as an excitation source, while a cooled charge coupled device camera was adopted to collect transmission fluorescence. In micro-CT, a flat panel detector based on amorphous silicon, with active area of 13×13 cm2, and a microfocus x-ray tube were used. The fDOT system was mounted orthogonally to the micro-CT and the projection images were acquired without rotation of the sample, which is different from the method used for micro-CT alone. Both the finite element method and the algebraic reconstruction technique were used to reconstruct images from the fDOT. Phantom data showed that the resolution of the fDOT system was about 3 mm at an imaging depth of 7 mm. Quantitative error was no more than 5% and imaging sensitivity for 1,1′-dioctadecyl-3,3,3′,3′-etramethylindotricarbocyanine iodide bis-oleate (DiR-BOA) was estimated to be higher than 100 nM at a depth of 7 mm. Calculations of the phantom’s center of mass showed that the location accuracy of fDOT was about 0.7 mm. We applied a Feldkamp algorithm to reconstruct the micro-CT image. By measuring the presampled modulation transfer function with a 30 μm tungsten thread, we estimated that the micro-CT has a resolution of 5 mm−1 when the field of view was 6.5 cm. Our results indicate the uniformity of the transaxial micro-CT image and the contrast-to-noise ratio was measured as 1.95 for a radiation dose of 1 cGy. A non-image-based method was employed for merging images from the two imaging modalities. A nude mouse with DiR-BOA, imaged ex vivo, was used to validate the feasibility of the dual-modality system.
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87.57.Q- Computed tomography
87.63.L- Visual imaging
87.10.Kn Finite element calculations
87.57.nf Reconstruction
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