3,797 research outputs found
Allan Variance Analysis as Useful Tool to Determine Noise in Various Single-Molecule Setups
One limitation on the performance of optical traps is the noise inherently
present in every setup. Therefore, it is the desire of most experimentalists to
minimize and possibly eliminate noise from their optical trapping experiments.
A step in this direction is to quantify the actual noise in the system and to
evaluate how much each particular component contributes to the overall noise.
For this purpose we present Allan variance analysis as a straightforward
method. In particular, it allows for judging the impact of drift which gives
rise to low-frequency noise, which is extremely difficult to pinpoint by other
methods. We show how to determine the optimal sampling time for calibration,
the optimal number of data points for a desired experiment, and we provide
measurements of how much accuracy is gained by acquiring additional data
points. Allan variances of both micrometer-sized spheres and asymmetric
nanometer-sized rods are considered.Comment: 14 pages, 6 figures, presented at SPIE Optics+Photonics 2009 in San
Diego, CA, US
Advanced photonic methodologies for the 'in vitro' manipulation of cellular systems
This thesis investigates the application of a variety of optical techniques for the
manipulation of single cells and their local micro-environment. The methodologies
developed provide enhanced control over a single cell under study affording exquisite
spatial and temporal control over biological processes of interest. The work presented
within the thesis can be split into three distinct categories.
The first of these provides an investigation in light activated “caged” molecular
probes. This work generated several new compounds which were then applied to
providing control over processes involved in pain, mitochondrial intracellular signalling and memory processes in the central nervous system. Application of caged
neurotransmitters then demonstrates the first in vitro wavelength orthogonal photolysis of biologically relevant substances. Such a technique has great potential in
the study of fundamental interactions within the processes underpinning memory
and cognitive function.
Secondly the application of optical injection techniques for the introduction of
membrane impermeable species of interest is presented. An exploration of laser
sources and optical systems has yielded two new strategies for optical injection.
The targeted introduction of fluorescent stains, nucleic acids and gold nanoparticles
to the interior of live mammalian cells demonstrates the power of these techniques.
Thirdly, an investigation in optical trapping and optical injection provides simplified micromanipulation techniqes for application to biological studies. The use
of capillaries as reservoirs for reagents of interest has realised a procedure for the
reduction of large-scale chemical assays to a single cell level in static flow. When
this technique is combined with intelligent control over the trapping laser source’s
temporal behaviour, the interaction with the sample under study can be tailored for biological amiability or sample ablation. In this way a single laser source can be employed for the optical trapping and nanosurgery of a biological sample. A final study
is presented demonstrating initial results for the targeted optical injection of caged
compounds into mammalian cells. This methodology draws on the strengths of optical injection and caging technologies and presents a significant step forward in the
level of control afforded over a biological system under study by optical techniques.
The studies presented highlight the level of control and flexibility afforded by the
application of optical manipulation and excitation strategies. Such optical methodologies extend the photonic tools available for enhanced studies in the life sciences
Preimplantation Mouse Embryo Selection Guided by Light-Induced Dielectrophoresis
Selection of optimal quality embryos for in vitro fertilization (IVF) transfer is critical to successful live birth outcomes. Currently, embryos are chosen based on subjective assessment of morphologic developmental maturity. A non-invasive means to quantitatively measure an embryo's developmental maturity would reduce the variability introduced by the current standard. We present a method that exploits the scaling electrical properties of pre-transfer embryos to quantitatively discern embryo developmental maturity using light-induced dielectrophoresis (DEP). We show that an embryo's DEP response is highly correlated with its developmental stage. Uniquely, this technique allows one to select, in sequence and under blinded conditions, the most developmentally mature embryos among a mixed cohort of morphologically indistinguishable embryos cultured in optimized and sub-optimal culture media. Following assay, embryos continue to develop normally in vitro. Light-induced dielectrophoresis provides a non-invasive, quantitative, and reproducible means to select embryos for applications including IVF transfer and embryonic stem cell harvest
Nano handling and measurement of biological cells in culture
A thesis submitted to the University of Bedfordshire in partial fulfillment of the requirements for the degree of Doctor of PhilosophyThis thesis systematically investigates the nano handling and measurement techniques for biological cells in culture and studies the techniques to realize innovative and multi-functional applications in biomedicine. Among them, the technique based on AFM is able to visualize and quantify the dynamics of organic cells in culture on the nano scale. Especially, the cellular shear adhesion force on the various locations of biological cells was firstly accurately measured in the research of the cell-substrate interaction in terms of biophysical perspective. The innovative findings are conductive to study the cell-cell adhesion, the cell-matrix adhesion which is related to the cell morphology structure, function, deformation ability and adhesion of cells and better understand the cellular dynamic behaviors. Herein, a new liquid-AFM probe unit and an increment PID control algorithm were implemented suitable for scanning the cell samples under the air conditions and the liquid environments. The influence between the surface of sample and
the probe, and the damage of probe during the sample scanning were reduced. The proposed system is useful for the nano handling and measurement of living cells.
Besides, Besides, to overcome the limitations of liquid-AFMs, the multiple optical tweezers were developed to integrate with the liquid-AFM. The technique based on laser interference is able to characterize the optical trap stiffness and the escape velocity, especially to realize the capture and sorting of multiple cells by a polarization-controlled periodic laser interference. It can trap and move hundreds of cells without physical contact, and has broad application prospects in cytology. Herein, a new experimental method integrated with the positioning analysis in the Z direction was used to improve the fluid force method for the calibration and characterize the mechanical forces exerted on optical traps and living cells. Moreover, a sensitive and highly efficient polarization-controlled three-beam interference set-up was developed for the capture and sorting of multiple cells. By controlling the polarization angles of the beams, various intensity distributions and different sizes of dots were obtained. Subsequently, we have experimentally observed multiple optical tweezers and the sorting of cells with different polarization angles, which are in accordance with the theoretical analysis
Roadmap for Optical Tweezers 2023
Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration
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