Magnetic Nanoparticles-Loaded Physarum polycephalum: Directed Growth and Particles Distribution.

Slime mold Physarum polycephalum is a single cell visible by an unaided eye. The slime mold optimizes its network of protoplasmic tubes to minimize expose to repellents and maximize expose to attractants and to make efficient transportation of nutrients. These properties of P. polycephalum, together with simplicity of its handling and culturing, make it a priceless substrate for designing novel sensing, computing and actuating architectures in living amorphous biological substrate. We demonstrate that, by loading Physarum with magnetic particles and positioning it in a magnetic field, we can, in principle, impose analog control procedures to precisely route active growing zones of slime mold and shape topology of its protoplasmic networks.

Magnetic nanoparticles-loaded Physarum polycephalum: Directed growth and particles distribution.

Slime mold Physarum polycephalum is a single cell visible by an unaided eye. The slime mold optimizes its network of protoplasmic tubes to minimize expose to repellents and maximize expose to attractants and to make efficient transportation of nutrients. These properties of P. polycephalum, together with simplicity of its handling and culturing, make it a priceless substrate for designing novel sensing, computing and actuating architectures in living amorphous biological substrate. We demonstrate that, by loading Physarum with magnetic particles and positioning it in a magnetic field, we can, in principle, impose analog control procedures to precisely route active growing zones of slime mold and shape topology of its protoplasmic networks.

Magnetic nanoparticles-loaded Physarum polycephalum: Directed growth and particles distribution.

Slime mold Physarum polycephalum is a single cell visible by an unaided eye. The slime mold optimizes its network of protoplasmic tubes to minimize expose to repellents and maximize expose to attractants and to make efficient transportation of nutrients. These properties of P. polycephalum, together with simplicity of its handling and culturing, make it a priceless substrate for designing novel sensing, computing and actuating architectures in living amorphous biological substrate. We demonstrate that, by loading Physarum with magnetic particles and positioning it in a magnetic field, we can, in principle, impose analog control procedures to precisely route active growing zones of slime mold and shape topology of its protoplasmic networks.

Hybridization of genomic DNA adsorbed electrostatically onto cationic surfaces.

Our previous study revealed an intriguing phenomenon of partial hybridization of two single strands of genomic DNA, with one of them being electrostatically adsorbed on a solid surface. Although the effect was confirmed with different methods and even recommended for a crude DNA analysis, the exact mechanism of hybridization was not clear. This work presents the results of more detailed study of adsorption and hybridization of two genomic DNA, of salmon and herring, using the experimental techniques of total internal reflection ellipsometry (TIRE), ATR FTIR spectroscopy, and AFM. The in situ TIRE study of the hybridization kinetics allowed the evaluation of the association constant. It appeared to be in the range of 10(5) mol(-1) L for binding complementary ss-DNA in comparison to 10(4) mol(-1) L for binding of noncomplementary ss-DNA. FTIR study directly confirmed the effect of partial binding of complementary ss-DNA by monitoring the 1650 and 1690 cm(-1) spectral bands. AFM showed the transformation from clearly resolved images of separate chains of ss-DNA molecules adsorbed on the surface of mica to an inhomogeneous layer of tangled and overlapping DNA molecules following binding of another complementary ss-DNA.

Electrochemical control of the conductivity in an organic memristor: a time-resolved X-ray fluorescence study of ionic drift as a function of the applied voltage.

Grazing-incidence X-ray fluorescence measurements were applied for a time-resolved study of an organic memristor conductivity variation mechanism. A comparison of these results with electrical measurements has allowed us to conclude that the variation of the fluorescence intensity of Rb ions is directly connected to the ionic charge transferred between the conducting polymer and the solid electrolyte, which made up the device. In addition, the conductivity of the memristor was shown to be a function of the transferred ionic charge.

X-ray reflectivity measurements of layer-by-layer films at the solid/liquid interface.

In this Letter, we present a method for the decoration of layer-by-layer (LbL) structures by heavy metal ions, which allows X-ray reflectivity (XRR) measurements at the solid/water interface. The improved contrast has allowed us to obtain well-structured X-ray reflectivity curves from samples at the liquid/solid interface that can be used for the film structure modeling. The developed technique was also used to follow the formation of complexes between DNA and the LbL multilayer. The XRR data are confirmed by independent null-ellipsometric measurements at the solid/liquid interface on the very same architectures.

Structural study of the DNA dipalmitoylphosphatidylcholine complex at the air-water interface.

We present here results that demonstrate the formation of a complex of DNA with zwitterionic dipalmitoylphosphatidylcholine (DPPC) monolayer at the air-water interface in the presence of Ca2+ ions; in particular, we show that the presence of Ca2+ cations is essential for the formation of the complex of DPPC with DNA. We characterize the resulting structure by X-ray reflectivity and by null-ellipsometry. We show that DNA maintains its native double helix form when attached to the zwitterionic lipid monolayer, at difference with the case of ammine containing monolayers. Our findings are discussed in view of other works that recently appeared on the interaction of DNA with zwitterionic phospholipids, emphasizing the role of DPPC as a potential vector for transfer of genetic material into mammalian cells by nonviral gene therapy and also suggesting Langmuir/Blodgett layers of zwitterionic phospoholipids as a method for nonconventional DNA immobilization.

Interaction of DNA oligomers with cationic lipidic monolayers: complexation and splitting.

Interactions of native DNA with octadecylamine (ODA) and hexadecymdimethylammonium bromide (HTAB) monolayers at the air/water interface were studied by pi-A isotherms, ellipsometry, and X-ray reflectivity. We show that the microscopic structure of ODA-DNA complexes is definitely consistent with a single-stranded form for DNA. On the contrary, with HTAB, DNA complexes in its native form. The crucial difference in the behavior of these two fairly similar lipids is due to the presence of the amine group in ODA. These results should be relevant to applications such as DNA chips and sensors.

Conducting polymer-solid electrolyte fibrillar composite material for adaptive networks.

The non-linear electrical characteristics of a polymeric electrochemically controlled junction based on a conducting polymer (polyaniline) and a solid electrolyte (Li doped polyethylene oxide) are considered as basic features for the realization of smart materials based on the statistical occurrence of such heterojunctions in statistical networks. In this paper we demonstrate the possibility of realizing such adaptive networks in a statistically mixed polymeric fibrillar heterostructure.

Electron beam irradiation for structuring of molecular assemblies.

Nontraditional applications of electron beam irradiation for patterning of molecular assemblies are considered. The electron beam can have the following effects on molecular layers: destruction of molecular structure under e-beam irradiation with a successive formation of new molecular system when the irradiation is stopped; variation of the properties of the layer after e-beam irradiation; crosslinking of molecules in the layer under irradiation; modification of the templates for the successive film growth, providing different growing conditions in irradiated and nonirradiated areas; and activation of the solid support surface and molecular systems in the film resulting in the increased adhesion of the layer to the substrate in irradiated areas. All these effects were used for patterning of thin layers of different compounds. Five classes of molecular systems were considered, namely, films of simple surfactant molecules, layers of charge-transfer complexes, films of conducting polymers, aggregated nanoparticulate layers and films of nanoengineered polymeric capsules. Characteristic features of patterning processes in each particular case are discussed.