A surface-bound DNA switch driven by a chemical oscillator.
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DNA↗
Biomedical subjects
Tim Liedl
Publications and source records attributed to Tim Liedl.
Multiple particle tracking in 3-D+t microscopy: method and application to the tracking of endocytosed quantum dots.
We propose a method to detect and track multiple moving biological spot-like particles showing different kinds of dynamics in image sequences acquired through multidimensional fluorescence microscopy. It enables the extraction and analysis of information such as number, position, speed, movement, and diffusion phases of, e.g., endosomal particles. The method consists of several stages. After a detection stage performed by a three-dimensional (3-D) undecimated wavelet transform, we compute, for each detected spot, several predictions of its future state in the next frame. This is accomplished thanks to an interacting multiple model (IMM) algorithm which includes several models corresponding to different biologically realistic movement types. Tracks are constructed, thereafter, by a data association algorithm based on the maximization of the likelihood of each IMM. The last stage consists of updating the IMM filters in order to compute final estimations for the present image and to improve predictions for the next image. The performances of the method are validated on synthetic image data and used to characterize the 3-D movement of endocytic vesicles containing quantum dots.
Algorithms↗
On the development of colloidal nanoparticles towards multifunctional structures and their possible use for biological applications.
In this Review, we describe the synthesis of high-quality colloidal nanoparticles in organic solvents, the mechanisms by which they can be transferred into aqueous solution, and some of their applications in biology. In particular, we will place emphasis on the creation of multifunctional nanoparticles or nanoparticle assemblies.
Animals↗
Nanoengineered polymer capsules: tools for detection, controlled delivery, and site-specific manipulation.
We present the concept of multifunctional nanoengineered polymer capsules and outline their applications as new drug delivery systems or supramolecular toolboxes containing, for example, enzymes capable of converting nontoxic prodrugs into toxic drugs at a designated location. Such functionalized nanocontainers offer a wide range of applications including enzymatic catalysis, controlled release, and directed drug delivery in medicine due to their multifunctionality. The unique advantage of capsules in comparison to other systems is that they can be functionalized or loaded simultaneously with the above-mentioned components, thus permitting multifunctional processes in single cells.
Animals↗
Fluorescent nanocrystals as colloidal probes in complex fluids measured by fluorescence correlation spectroscopy.
The diffusion properties of fluorescent colloidal CdSe and CdSe/ZnS nanocrystals (QDs) with different hydrophilic coatings were characterized in complex fluids such as actin solutions using fluorescence correlation spectroscopy (FCS). The hydrodynamic radii of the QDs were determined both in organic solvents and water. Attention was given to the potential artifacts arising from the fluorescence properties of the QDs. With increasing excitation intensities, the apparent particle concentration and diffusion times are overestimated if using a simple diffusion model. This can be explained by a numerical simulation. The diffusion behavior of QDs in actin networks of different concentrations was determined to demonstrate the potential use of nanocrystals as probes in soft biological matter. The decreasing diffusion coefficient of the nanocrystals with increasing actin concentration results in an intrinsic polymer viscosity of 0.12+/-0.02 ml mg(-1), in accordance with literature values.
Actins↗
Cytotoxicity of colloidal CdSe and CdSe/ZnS nanoparticles.
Cytotoxicity of CdSe and CdSe/ZnS nanoparticles has been investigated for different surface modifications such as coating with mercaptopropionic acid, silanization, and polymer coating. For all cases, quantitative values for the onset of cytotoxic effects in serum-free culture media are given. These values are correlated with microscope images in which the uptake of the particles by the cells has been investigated. Our data suggest that in addition to the release of toxic Cd(2+) ions from the particles also their surface chemistry, in particular their stability toward aggregation, plays an important role for cytotoxic effects. Additional patch clamp experiments investigate effects of the particles on currents through ion channels.
Animals↗
Switching the conformation of a DNA molecule with a chemical oscillator.
pH oscillations generated by a nonequilibrium chemical reaction are used to switch a pH-sensitive DNA structure between two distinct conformations. The utilization of a chemical oscillator represents a novel method for achieving autonomous motion in molecular devices. The oscillatory reaction is a variant of the Landolt reaction and produces pH variations in the range between pH 5 and 7. In this range, a cytosine-rich DNA strand can be switched between a random coil conformation and the folded i-motif structure. The conformational changes are monitored simultaneously with the pH value in fluorescence-resonance energy-transfer experiments.
Cytosine↗