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A single isolated cardiac muscle cell, cardiomyocyte, is a reliable experimental model to study intrinsic mechanical properties of the myocardium. To date, there are few reports aimed to examine cell force parameters during isometric contractions for mimicking cell behavior in the intact heart. No studies were conducted to implement isometric contractions of cardiomyocytes using digital systems. This work is devoted to the use of an adaptive feed-forward control approach for a digital micromanipulation system to subject single cardiomyocytes to near-isometric contractions. To overcome the linear time dependence of digital micromanipulator movement we fitted the complex time dependence of the cell length change to an isosceles trapezoid. The developed software initiated outwardly directed trapezoidal countermovement of micromanipulators during cell auxotonic contractions to achieve the cell length near-constant. The preliminary experiments showed that the maximum normalized force during near-isometric contractions was 2.5 times greater compared with auxotonic contractions that corresponds to earlier studies. The developed approach provides a powerful research tool to study cardiac biomechanics at the cell level under in vivo-like conditions. [ABSTRACT FROM AUTHOR]

Currently, the most common model object of molecular and biological research is cell cultures. This work is devoted to the selection of optimal cell cultures for their use in cellular engineering technologies and the possibility of using differ ent microtools in micromanipulations with cells. A scientific study has found that of the six cell lines studied, the most optimal micromanipulations are human skin fibroblasts and Hela line cells. It was also found that when conducting micromanipulations with cells of these lines it is necessary to use only microtools without spikes, as the use of them with spikes leads to a significant decrease in the index of cell viability. [ABSTRACT FROM AUTHOR]

We report here on the reorientation dynamics of the avian Red Blood Cell (aRBC), a structure ellipsoidal in shape and with a non-uniform distribution of birefringence across its diameter. We find that in linearly polarized light, an aRBC shows a dual reorientation behavior with the first reorientation about the major axis and the second about the minor axis so as to align its major axis along the laser propagation direction. We are able to explain the observed sequence of reorientation as a consequence of the minimization of work done in rotating the avian cell first about the major axis and then about the minor axis. These calculations are also used to also show why a single reorientation about the minor axis to reach the final equilibrium position is not seen experimentally. Further, in the case of elliptically polarized light, we see that the second reorientation process about the minor axis of the cell can be controlled by the ellipticity of the polarization of light. We explain this as a consequence of balance between the torques due to birefringence and reorientation. [ABSTRACT FROM AUTHOR]

Live mammalian cells from various tissues of origin can be aseptically and noninvasively micromanipulated via lasers of different regimes. Laser-driven techniques are therefore paving a path toward the advancement of human immunodeficiency virus (HIV-1) investigations. Studies aimed at the interaction of laser light, nanomaterials, and biological materials can also lead to an understanding of a wealth of disease conditions and result in photonics-based therapies and diagnostic tools. Thus, in our research, both continuous wave and pulsed lasers operated at varying wavelengths are employed, as they possess special properties that allow classical biomedical applications. This paper discusses photo-translocation of antiretroviral drugs into HIV-1 permissive cells and preliminary results of low-level laser therapy (LLLT) in HIV-1 infected cells. [ABSTRACT FROM AUTHOR]

Biosensors are analytic devices that incorporate a biochemical recognition system (biological, biologicalderived or biomimic: enzyme, antibody, DNA, receptor, etc.) in close contact with a physicochemical transducer (electrochemical, optical, piezoelectric, conductimetric, etc.) that converts the biochemical information, produced by the specific biological recognition reaction (analyte-biomolecule binding), into a chemical or physical output signal, related to the concentration of the analyte in the measuring sample. The biosensing concept is based on natural chemoreception mechanisms, which are feasible over/within/by means of a biological membrane, i.e., a structured lipid bilayer, incorporating or attached to proteinaceous moieties that regulate molecular recognition events which trigger ion flux changes (facilitated or passive) through the bilayer. The creation of functional structures that are similar to natural signal transduction systems, correlating and interrelating compatibly and successfully the physicochemical transducer with the lipid film that is self-assembled on its surface while embedding the reconstituted biological recognition system, and at the same time manage to satisfy the basic conditions for measuring device development (simplicity, easy handling, ease of fabrication) is far from trivial. The aim of the present work is to present a methodological framework for designing such molecular sensing interfaces, functioning within a knowledge-based system built on an ontological platform for supplying sub-systems options, compatibilities, and optimization parameters. [ABSTRACT FROM AUTHOR]

Using a standing wave field of ultrasound, it is possible to trap and manipulate small objects at nodes of a sound pressure distribution. In the present paper, a sound wave was generated by a transducer far from a microchannel, and propagated into a microchannel on a glass plate, where it generated a standing wave field. When the liquid water containing alumina particles was injected into the microchannel, the particles flowed along several layers in the flat microchannel. It was shown that the traveling wave was transmitted into the microchannel and the standing wave field was formed in the microchannel. When a half circular space and a branched microchannel were added in the center of the microchannel and the frequency of the ultrasound swept, the exit channel of the particle flow can be selected. [ABSTRACT FROM AUTHOR]

The high-specificity self-assembling nature of DNA makes the molecule a candidate for the template for the construction of molecular devices. In order to construct a functional device, the template must be positioned onto a predetermined site on a substrate to allow external connections, and the components must be properly aligned onto the template. A key factor is the high yield of binding, especially when the device consists of many components. Such high yield requires that the bases of the template DNA be exposed so that its counterpart can interact freely, and the template be stretched to avoid folding or coiling that hampers the interaction. We have developed electrokinetic DNA manipulation method, by which a double-stranded DNA is stretched and immobilized bridging over an electrode pair, with the molecular ends anchored while the middle part is left free to interact with foreign molecules. However, double-stranded DNA has a closed structure and the bases inside are not easily accessible. To have a template DNA with accessible bases, two methods are developed in this paper; one being the direct stretching of single-stranded DNA, and the other being the use of a recombination protein to make the bases of double-stranded DNA accessible. The former has an advantage in its simplicity, and the latter in its mechanical stability. We expect that these stretch-and-positioned DNA with accessible base-pairs will lead to the high-yield molecular construction. [ABSTRACT FROM AUTHOR]

We describe the topic of beam shaping (sculpting) the phase and amplitude of light for applications in Biophotonics. Methods to create and apply 'non-diffracting' modes in cell transfection and micromanipulation will be discussed as well as a new method to correct for aberrations in situ and overcome the diffraction limit. [ABSTRACT FROM AUTHOR]