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4 Dec 2006

Volume 89, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 89, 233120 (2006); http://dx.doi.org/10.1063/1.2402115 (3 pages)

S. Yeo, Y. Horibe, S. Mori, C. M. Tseng, C. H. Chen, A. G. Khachaturyan, C. L. Zhang, and S.-W. Cheong
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Elastomechanical model of tumor invasion

Caterina Guiot, Nicola Pugno, and Pier Paolo Delsanto

Appl. Phys. Lett. 89, 233901 (2006); http://dx.doi.org/10.1063/1.2398910 (3 pages) | Cited 5 times

Online Publication Date: 4 December 2006

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Tumor invasion concerns the tumor capability of colonizing the host by means of several complex biochemical processes. Since certain aspects of the problem present a striking resemblance with well known physical mechanisms, the authors propose here an analogy between tumoral invasive branching in a tissue and the mechanical insertion of a solid inclusion in an elastic material specimen. The model, which is an extension of a previous one, based on the universal growth law of West et al. [Nature (London) 413, 628 (2001)] , is discussed in the case of multicellular tumor spheroids (and cords), but it may be adapted to understand invasion also in real tumors.
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87.19.R- Mechanical and electrical properties of tissues and organs
87.19.X- Diseases
87.10.-e General theory and mathematical aspects
87.18.-h Biological complexity
87.15.R- Reactions and kinetics

Deoxyribonucleic acid hybridization acceleration by photovoltaic effect

Chii-Chang Chen, Wei-Chi Ku, Sung-Kay Chiu, and Chi-Meng Tzeng

Appl. Phys. Lett. 89, 233902 (2006); http://dx.doi.org/10.1063/1.2397539 (2 pages)

Online Publication Date: 5 December 2006

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In this study, the authors show a method of enhancing the deoxyribonucleic acid (DNA) hybridization efficiency by exploiting the photovoltaic effect. The arrayed microchip is fabricated in a semiconductor wafer coated with metal thin films to immobilize the probe DNA. Hybridization between immobilized probe DNAs and fluorescent-labeled target DNA is performed under illumination by a laser. The photovoltaic effect induces positive charges on the surface of the microchip to attract negatively charged target DNAs toward the hybridization sites, increasing the hybridization rate by up to two orders of magnitude. The experimental results reveal that the method represents a cutting-edge solution to the problem of the time consuming microchip process.
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87.80.-y Biophysical techniques (research methods)
87.14.G- Nucleic acids
42.62.Be Biological and medical applications
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

DNA release from cationic liposome/DNA complexes by anionic lipids

Giulio Caracciolo, Daniela Pozzi, Ruggero Caminiti, Cristina Marchini, Maura Montani, Augusto Amici, and Heinz Amenitsch

Appl. Phys. Lett. 89, 233903 (2006); http://dx.doi.org/10.1063/1.2399356 (3 pages) | Cited 5 times

Online Publication Date: 5 December 2006

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The authors found that recently developed multicomponent cationic liposome DNA complexes (lipoplexes) exhibit higher transfection efficiency with respect to usually employed binary lipoplexes in NIH 3T3 and A17 cell lines. Interaction of lipoplexes with anionic liposomes (model of cellular membranes) was investigated by synchrotron small angle x-ray diffraction. The authors used one-dimensional DNA packing density to estimate the molar fraction of DNA released from lipoplexes by anionic lipids.
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87.14.G- Nucleic acids
87.16.D- Membranes, bilayers, and vesicles

Controlled manipulation and actuation of micro-objects with magnetotactic bacteria

Sylvain Martel, Charles C. Tremblay, Serge Ngakeng, and Guillaume Langlois

Appl. Phys. Lett. 89, 233904 (2006); http://dx.doi.org/10.1063/1.2402221 (3 pages) | Cited 33 times

Online Publication Date: 7 December 2006

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Bacterial actuation and manipulation are demonstrated where Magnetospirillum gryphiswaldense magnetotactic bacteria (MTB) are used to push 3 μm beads at an average velocity of 7.5 μm s−1 along preplanned paths by modifying the torque on a chain of magnetosomes in the bacterium with a directional magnetic field of at least 0.5 G generated from a small programmed electrical current. But measured average thrusts of 0.5 and 4 pN of the flagellar motor of a single Magnetospirillum gryphiswaldense and MC-1 MTB suggest that average velocities greater than 16 and 128 μm s−1, respectively could be achieved.
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87.80.-y Biophysical techniques (research methods)
87.17.Jj Cell locomotion, chemotaxis
47.63.Gd Swimming microorganisms
47.65.-d Magnetohydrodynamics and electrohydrodynamics

Glass transition temperature of water confined in lipid membranes as determined by anelastic spectroscopy

C. Castellano, J. Generosi, A. Congiu, and R. Cantelli

Appl. Phys. Lett. 89, 233905 (2006); http://dx.doi.org/10.1063/1.2402240 (3 pages) | Cited 11 times

Online Publication Date: 7 December 2006

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The research of gene delivery vehicles used in gene therapy is focused on nonviral vectors like lipid membranes. Such vectors, nonimmunogenic and biodegradable, are formed by complexation of DNA with a mixture of cationic lipids and a neutral colipid which improve the transfection efficiency. A main topic related to lipid membrane dynamics is their capability to spontaneously confine water. At present the value of the glass transition temperature (Tg) is largely debated and determined only by some indirect methods. Here the authors show that anelastic spectroscopy allows the confined water Tg value to be directly identified in several lipid mixtures.
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87.14.Cc Lipids
87.16.D- Membranes, bilayers, and vesicles
87.15.La Mechanical properties
87.15.M- Spectra of biomolecules
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Spectroscopic infrared near-field microscopy and x-ray reflectivity studies of order and clustering in lipid membranes

J. Generosi, G. Margaritondo, J. S. Sanghera, I. D. Aggarwal, N. H. Tolk, D. W. Piston, A. Congiu Castellano, and A. Cricenti

Appl. Phys. Lett. 89, 233906 (2006); http://dx.doi.org/10.1063/1.2403184 (3 pages) | Cited 6 times

Online Publication Date: 8 December 2006

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Lipid membranes were studied by infrared scanning near-field optical microscopy at several wavelengths and by x-ray reflectivity. Together with the x-ray data, the optical images indicate the formation of locally ordered multiple bilayers, and the topographical micrographs reveal the presence of islands at the surface, both critically important features for biotechnology and medical applications such as biosensors and gene therapy.
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87.16.D- Membranes, bilayers, and vesicles
87.14.Cc Lipids
87.64.M- Optical microscopy
87.64.K- Spectroscopy
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
87.63.L- Visual imaging
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