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Biomedical subjects

Michael Giersig

Publications and source records attributed to Michael Giersig.

18 recordsLinked to original sources
PubMed2006

Quantum dot modified multiwall carbon nanotubes.

A novel strategy for the fabrication of multiwall carbon nanotube-nanocrystal heterostructures is shown. Different quantum dots (QDs) with narrow size distributions were covalently coupled to carbon nanotubes (CNTs) and silica-coated CNTs in a simple, uniform, and controllable manner. The structural and optical properties of CNT/QD heterostructures are characterized by electron microscopy and photoluminescence spectroscopy. Complete quenching of the PL bands in both QD core and core/shell heterostructures was observed after adsorption to the CNTs, presumably through either carrier ionization or energy transfer. The deposition of a silica shell around the CNTs preserves the fluorescence properties by insulating the QD from the surface of the CNT.

Journal Article↗
PubMed2006

Spontaneous transformation of CdTe nanoparticles into angled Te nanocrystals: from particles and rods to checkmarks, X-marks, and other unusual shapes.

CdTe nanoparticles spontaneously transform into the branched Te nanocrystals with the unique, highly anisotropic shape of checkmarks after partial removal of the stabilizers of L-cysteine. The Te checkmarks are made in a relatively high yield and uniformity; the length of the arms is ca. 150 nm, whereas the angle between the arms is 74 degrees . Subsequent growth of the particle yields mothlike nanocrystals retaining geometrical anisotropy. Unlike the previous synthesis methods of branched nanocrystals, they are formed via a merger of individual rod-shaped crystallites. High-energy crystal faces on their apexes act as the sticky points causing the particles to join in the ends. This is the first demonstration of spontaneous transformation of binary semiconductor particles into highly anisotropic nanocolloids in an angled conformation. The end reactivity of starting Te rods can be used both for bottom-up fabrication of nanoscale electronics and relatively safe and nontoxic method of synthesis of Te-based optical and other materials.

Cadmium↗
PubMed2006

Nanomedicine for respiratory diseases.

Nanotechnology provides new materials in the nanometer range with many potential applications in clinical medicine and research. Due to their unique size-dependent properties nanomaterial such as nanoparticles offer the possibility to develop both new therapeutic and diagnostic tools. Thus, applied nanotechnology to medical problems--nanomedicine--can offer new concepts that are reviewed. The ability to incorporate drugs into nanosystems displays a new paradigm in pharmacotherapy that could be used for cell-targeted drug delivery. Nontargeted nanosystems such as nanocarriers that are coated with polymers or albumin and solid lipid particles have been used as transporter in vivo. However, nowadays drugs can be coupled to nanocarriers that are specific for cells and/or organs. Thus, drugs that are either trapped within the carriers or deposited in subsurface oil layers could be specifically delivered to organs, tumors and cells. These strategies can be used to concentrate drugs in selected target tissues thus minimizing systemic side effects and toxicity. In addition to these therapeutic options, nanoparticle-based "molecular" imaging displays a field in which this new technology has set the stage for an evolutionary leap in diagnostic imaging. Based on the recent progress in nanobiotechnology there is potential for nanoparticles and -systems to become useful tools as therapeutic and diagnostic tools in the near future.

Animals↗
PubMed2006

Multi-walled carbon nanotubes and metallic nanoparticles and their application in biomedicine.

Interdisciplinary research has become a matter of paramount importance for novel applications of nanomaterials in biology and medicine. As such, many disciplines-physics, chemistry, microbiology, cell biology, and material science-all contribute to the design, synthesis and fabrication of functional and biocompatible devices at the nanometer scale. Since the most areas of cell biology and biomedicine deal with functional entities such as DNA and proteins, mimicry of these structures and function in the nanosize range offers exciting opportunities for the development of biosensors, biochips, and bioplatforms. In this report we highlight the potential benefits and challenges that arise in the manufacture of biocompatible nanoparticles and nano-networks that can be coupled with biological objects. Among the challenges facing us are those concerned with making the necessary advances in enabling affordability, innovation, and quality of manufactured nanodevices for rapid progress in the emerging field of bio-nanotechnology. The convergence of nanotechnology and biomedicine makes nanoscale research highly promising for new discoveries that can cost-effectively accelerate progress in moving from basic research to practical prototypes and products.

Carbon↗
PubMed2006

Nanoparticle-based diagnosis and therapy.

Nanoparticles are at the leading edge of the rapidly developing field of material science in nanotechnology with many potential applications in clinical medicine and research. Due to their unique size-dependent properties nanoparticles offer the possibility to develop both new therapeutic and diagnostic tools. The ability to incorporate drugs into nanosystems displays a new paradigm in pharmacotherapy that could be used for cell-targeted drug delivery. Nontargeted nanosystems such as nanocarriers that are coated with polymers or albumin and solid lipid particles have been used to transport a large number of compounds. However, nowadays drugs can be coupled to nanocarriers that are specific for cells and/or organs. Thus, drugs that are either trapped within the carriers or deposited in subsurface oil layers could be specifically delivered to organs, tumors and cells. These strategies can be used to concentrate drugs in selected target tissues thus minimizing systemic side effects and toxicity. In addition to these therapeutic options, nanoparticle-based "molecular" imaging displays a field in which this new technology has set the stage for an evolutionary leap in diagnostic imaging. Based on the recent progress in nanobiotechnology, nanoparticles have the potential to become useful tools as therapeutic and diagnostic tools in the near future.

Animals↗
PubMed2005

From colloidal Co/CoO core/shell nanoparticles to arrays of metallic nanomagnets: surface modification and magnetic properties.

The magnetic properties of nanoparticles can be subject to strong variations as the chemical composition of the particle surface is modified. To study this interrelation of surface chemistry and magnetism, self-assembled layers of colloidal 9.5 nm Co/CoO core/shell nanoparticles were exposed to mild reactive hydrogen and oxygen plasmas. The consecutive oxygen/hydrogen plasma treatment transforms the particle layer into an array of metallic nanomagnets with complete reduction of the oxide and removal of the organic surfactants. The original arrangement of the particle array and the number of Co atoms per particle remains unchanged within the experimental error, and thus this is a possible route for the fabrication of ultrahigh-density magnetic bit structures from colloidal dispersions. The magnetic properties can be tuned by controlling the thickness of the surface oxide layer, which magnetically hardens the particles, as evidenced by element-specific magnetic hysteresis loops.

Journal Article↗
PubMed2005

Alignment of carbon nanotubes under low magnetic fields through attachment of magnetic nanoparticles.

The alignment of multiwalled carbon nanotubes (MWNTs) has been accomplished through deposition of uniform layers of magnetite/maghemite nanoparticles (diameter = 6-10 nm) and use of an external magnetic field. The coating of CNTs with magnetic nanoparticles was performed by combining the polymer wrapping and layer-by-layer (LbL) assembly techniques. The particle-coated MWNTs are superparamagnetic and can be aligned at room temperature on any substrate by deposition from an aqueous solution in an external field B = 0.2 T. The volume magnetization of the particle coated MWNTs is found to be enhanced by 17% compared to the pure particles in a powder indicating that either the adsorption process onto the CNTs changes the particle magnetization, or the MWNTs carry an intrinsic magnetization due to remaining Ni used as a catalyst for the growth process.

Letter↗
PubMed2005

From anisotropic photo-fluidity towards nanomanipulation in the optical near-field.

An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the degree of mechanical anisotropy can be controlled by light. Whereas during irradiation by circular polarized light the film behaves as an isotropic viscoelastic fluid, it shows considerable fluidity only in the direction parallel to the light field vector under linear polarized light. The fluidization phenomenon is related to photoinduced motion of azobenzene-functionalized molecular units, which can be effectively activated only when their transition dipole moments are oriented close to the direction of the light polarization. We also describe here how the photofluidization allows nanoscopic elements of matter to be precisely manipulated.

Anisotropy↗
PubMed2005

Multi-walled carbon nanotubes for plasmid delivery into Escherichia coli cells.

Introduction of foreign genes into bacterial cells (transformation) is used for supplementing defective genes or providing additional biological functions. Transformation can be achieved using either chemical or physical methods, e.g., electroporation. Bulk electroporation offers several advantages over chemical methods, including high transformation efficiency, but its application is limited due to the high numbers of cells and plasmids needed as a result of the high death rate of cells during this process, and the difficulty in electroporating single cells. Synthetic inorganic gene nanocarriers have received limited attention in the transformation of bacterial cells. Here we present a plasmid delivery system based on water dispersible multi-walled carbon nanotubes (CNTs) that can simultaneously target the bacterial surface and deliver the plasmids into the cells via temporary nanochannels across the cell envelope. Transformation experiments performed on E. coli provide evidence for the high potential of CNTs for nanoscale cell electroporation.

Escherichia coli↗
PubMed2005

Fabrication of nanoscale rings, dots, and rods by combining shadow nanosphere lithography and annealed polystyrene nanosphere masks.

The application of shadow nanosphere lithography for the preparation of large-area, two-dimensional, metallic nanostructures of different shape is described. Through changing the mask morphology by temperature processing and varying the evaporation conditions, particles with morphologies such as rings, rods, and dots have been produced. This process allows outstanding control of the size and morphology of the particles. The efficient technique is shown to scale down the size of metallic nanoparticles from 200 to 30 nm, while preserving the original nanosphere spacing and order. The 150-nm-diameter Fe rings produced by this method show ferromagnetic behavior, which was predicted by theoretical simulation. All the experimental results were confirmed by computer simulations, which also showed the possibility of creating periodic arrays of any other geometrical shape.

Computer Simulation↗
PubMed2005

Magnetic colloidosomes derived from nanoparticle interfacial self-assembly.

Based on the interfacial self-assembly of magnetite nanoparticles, we demonstrate the formation of colloidosomes with shells predominantly composed of monolayers of liquid-like, close-packed nanoparticles. The gelation of aqueous phase with agarose leads to robust and water-dispersible nanoparticle colloidosomes, allowing encapsulation of various water soluble materials. The cutoff of the nanoparticle colloidosomes obtained is primarily defined by the nanoparticle size. This controllable permeability should be of great importance for the encapsulation application.

Colloids↗
PubMed2005

Electrochemistry of a carbon microfiber adsorbed by cobalt nanoparticles.

The adsorption of cobalt nanoparticles on a carbon microfiber surface has been electrochemicaly detected. The redox processes observed in an electrochemical cell filled with redistilled water and equipped with the carbon fiber microelectrode modified by cobalt nanoparticles have been compared to those observed in an aqueous solution of Co2+ cations. The movement of the adsorbed nanoparticles has been demonstrated by the feedback capacitance-potential method.

Adsorption↗
PubMed2004

AuAg bimetallic nanoparticles: formation, silica-coating and selective etching.

A time-resolved study of the formation of AuAg alloy nanoparticles during boiling of AgNO3 and HAuCl4 in the presence of sodium citrate has been performed by monitoring the UV-visible spectra of the solutions. This study reveals clear differences with respect to the formation of pure Au particles, and suggests that gold and silver nanoparticles nucleate separately, but lattice rearrangement eventually leads to formation of alloy nanoparticles with the expected composition, which was confirmed by high resolution TEM. Additionally, we studied the chemical reaction of the alloy nanoparticles with NH4OH, observing that part of the Ag atoms get oxidized, but reorganization of the crystal lattice during the reaction prevents full transformation into pure gold nanoparticles. This allows the synthesis of silica-coated bimetallic particles with tailored plasmon resonance between ca. 430 and 520 nm, as well as homogeneous incorporation of the coated alloy nanoparticles within silica gels.

Journal Article↗
PubMed2002

Spontaneous organization of single CdTe nanoparticles into luminescent nanowires.

Nanoparticles of CdTe were found to spontaneously reorganize into crystalline nanowires upon controlled removal of the protective shell of organic stabilizer. The intermediate step in the nanowire formation was found to be pearl-necklace aggregates. Strong dipole-dipole interaction is believed to be the driving force of nanoparticle self-organization. The linear aggregates subsequently recrystallized into nanowires whose diameter was determined by the diameter of the nanoparticles. The produced nanowires have high aspect ratio, uniformity, and optical activity. These findings demonstrate the collective behavior of nanoparticles as well as a convenient, simple technique for production of one-dimensional semiconductor colloids suitable for subsequent processing into quantum-confined superstructures, materials, and devices.

Journal Article↗