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7 Jan 2008

Volume 92, Issue 1, Articles (01xxxx)

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Appl. Phys. Lett. 92, 011101 (2008); http://dx.doi.org/10.1063/1.2828458 (3 pages)

F. Pedaci, S. Barland, E. Caboche, P. Genevet, M. Giudici, J. R. Tredicce, T. Ackemann, A. J. Scroggie, W. J. Firth, G.-L. Oppo, G. Tissoni, and R. Jäger
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Electroporation chip for adherent cells on photochemically modified polymer surfaces

Michael Olbrich, Esther Rebollar, Johannes Heitz, Irene Frischauf, and Christoph Romanin

Appl. Phys. Lett. 92, 013901 (2008); http://dx.doi.org/10.1063/1.2826272 (3 pages) | Cited 3 times

Online Publication Date: 2 January 2008

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We present a polytetrafluoroethylene electroporation microchip with integrated electrodes for transfection of adherent biological cells. For fabrication, UV-surface modification was employed in combination with metal deposition. UV irradiation in reactive atmosphere resulted in introduction of polar chemical groups into the polytetrafluoroethylene surface for significant adhesion enhancement of both biological cells as well as metal electrodes thereon. Electroporation was demonstrated by transfection of human embryonic kidney cells with the enhanced green fluorescent protein. Transparent, working at low voltages, and easy to handle, this chip yields the potential to reduce the amount of sequential working steps necessary for transfection.
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87.17.-d Cell processes

Minimizing photobleaching in fluorescence microscopy by depleting triplet states

Partha Pratim Mondal

Appl. Phys. Lett. 92, 013902 (2008); http://dx.doi.org/10.1063/1.2830996 (3 pages) | Cited 5 times

Online Publication Date: 7 January 2008

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A technique for minimizing photobleaching in fluorescence microscopy is proposed. One of the prominent reason for photobleaching is the involvement of metastable triplet states during the excitation-emission process. Photobleaching minimization is achieved by depleting triplet states (T1→S0) employing a depletion pulse just after the excitation pulse thereby resulting in highly populated singlet ground state S0. Thus, the next excitation pulse can cause rapid population inversion (S0→S1) due to the availability of electrons in the ground state. This increases the fraction of population that is undergoing fluorescence (S1→S0), whereas the depletion pulse continuously depletes the triplet states. An interesting phase transition from occupied to unoccupied triplet state is observed. The excitation-depletion cycle is continued throughout the imaging process. The performance of such a system is examined through theoretical calculation and computational study of population dynamics. Substantial reduction in photobleaching of fluorescent molecules such as fluorescein promises several interesting applications in bioimaging, microscopy, and other optical studies.
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87.15.mq Luminescence
87.64.mn Multiphoton
87.80.-y Biophysical techniques (research methods)

Silicon-based nanochannel glucose sensor

Xihua Wang, Yu Chen, Katherine A. Gibney, Shyamsunder Erramilli, and Pritiraj Mohanty

Appl. Phys. Lett. 92, 013903 (2008); http://dx.doi.org/10.1063/1.2832648 (3 pages) | Cited 14 times

Online Publication Date: 8 January 2008

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Silicon nanochannel biological field effect transistors have been developed for glucose detection. The device is nanofabricated from a silicon-on-insulator wafer with a top-down approach and surface functionalized with glucose oxidase. The differential conductance of silicon nanowires, tuned with source-drain bias voltage, is demonstrated to be sensitive to the biocatalyzed oxidation of glucose. The glucose biosensor response is linear in the 0.5–8 mM concentration range with 3–5 min response time. This silicon nanochannel-based glucose biosensor technology offers the possibility of high density, high quality glucose biosensor integration with silicon-based circuitry.
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85.30.Tv Field effect devices
87.85.Ox Biomedical instrumentation and transducers, including micro-electro-mechanical systems (MEMS)
87.85.Rs Nanotechnologies-applications

Fiber-focused diode bar optical trapping for microfluidic flow manipulation

Robert W. Applegate, Jr., Jeff Squier, Tor Vestad, John Oakey, and David W. M. Marr

Appl. Phys. Lett. 92, 013904 (2008); http://dx.doi.org/10.1063/1.2829589 (3 pages) | Cited 10 times

Online Publication Date: 9 January 2008

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The direct integration of light and optical control into microfluidic systems presents a significant hurdle to the development of portable optical trapping-based devices. We present a simple, inexpensive fiber-based approach that allows for easy implementation of diode bars for optical particle separations within flowing microfluidic systems. We also develop models that demonstrate the advantages of manipulating particles within flow using linear geometries as opposed to individually focused point traps as traditionally employed in optical trapping micromanipulation.
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42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.81.Wg Other fiber-optical devices
42.62.Cf Industrial applications

Metal-enhanced e-type fluorescence

Yongxia Zhang, Kadir Aslan, Michael J. R. Previte, and Chris D. Geddes

Appl. Phys. Lett. 92, 013905 (2008); http://dx.doi.org/10.1063/1.2829798 (3 pages) | Cited 3 times

Online Publication Date: 10 January 2008

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In this letter, we report metal-enhanced e-type fluorescence. Eosin in close proximity to silver island films (SiFs) shows enhanced e-type fluorescence with an approximately two-fold higher intensity observed from SiFs, as compared to a control sample. Our findings suggest two complementary mechanisms for the enhancement: surface plasmons can radiate e-type delayed fluorescence efficiently and enhanced absorption also facilitates enhanced emission from both S1 and T1 states. This observation is helpful in our understanding not only for studying the interactions between plasmons and fluorophores but also for our laboratories continued efforts to develop a unified plasmon-lumophore description.
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78.60.-b Other luminescence and radiative recombination
78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
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