| Current
Nanoscience
ISSN: 1573-4137
Current Nanoscience
Volume 2, Number 4, November 2006
Contents
Heterologous Virus-Like-Particles: Recombinant
Nanosystems as Versatile Antigen Delivery Devices for Immune
Intervention Pp. 295-309
Christoph Reichel, Marc Brinkman, Claus Ruehland, Christian
O.A. Reiser and Juergen Hess
[Abstract]
Enhancing the Sensitivity of SAW Sensors with
Nanostructures Pp. 311-318
Yeswanth L. Rao and Guigen Zhang
[Abstract]
Functionalization of CNTs: New Routes Towards
the Development of Novel Electrochemical Sensors
Pp. 319-327
Jian-Shan Ye and Fwu-Shan Sheu
[Abstract]
High-Resolution Imaging and Force Measurement
of Individual Membrane Proteins by AFM Pp. 329-335
Filipp Oesterhelt and Simon Scheuring
[Abstract]
High Resolution Interference Microscopy: A Tool
for Probing Optical Waves in the Far-Field on a Nanometric
Length Scale Pp. 337-350
Carsten Rockstuhl, Iwan Märki, Toralf Scharf, Martin
Salt, Hans Peter Herzig and René Dändliker
[Abstract]
Stress-Induced Reduction of Water Uptake in Clay-reinforced
Epoxy Nanocomposites Pp. 351-357
Erol Sancaktar and Jason Kuznicki
[Abstract]
Revisiting Silver Nanoparticle Chemical Synthesis
and Stability by Optical Spectroscopy Pp. 359-371
Anne Van Hoonacker and Patrick Englebienne
[Abstract]
Dental Nanocomposites Pp. 373-381
Mui Siang Soh, Alan Sellinger and Adrian UJ. Yap
[Abstract]
Abstracts
[Back to top]
Heterologous Virus-Like-Particles: Recombinant Nanosystems
as Versatile Antigen Delivery Devices for Immune Intervention
Christoph Reichel, Marc Brinkman, Claus Ruehland, Christian
O.A. Reiser and Juergen Hess
Biological protein-based entities that form nanostructures
ranging from 8 to 50 nm in size represent promising candidates
in the development of novel immunotherapeutics against cancer
and microbial pathogens. These recombinant nanoparticles usually
consist of major coat or core proteins derived from viruses
like for instance papillomavirus, polyomavirus, parvovirus
or hepatitis B virus that spontaneously assemble into these
highly ordered, supramolecular, icosahedral structures. By
genetic engineering of permissive sites or cross-linking to
surface-exposed subunit domains these nanoparticles successfully
serve as carrier matrix with per se adjuvant activity for
the delivery of appropriate guest peptides, protein fragments
and complete proteins. Using this nanobiotechnology, potent
humoral and cell-mediated immunity with emphasis on CD4 and
CD8 T cell responses are induced against self or non-self
foreign antigens representing appropriate immunostimulatory
epitopes or complete proteins of microbial pathogens or tumor-associated
antigens. Breaking of T and B cell tolerance required for
therapeutic interventions against cancer represents the hallmark
of such an outstanding antigen delivery system. In combination
with the increasing identification of validated target antigens
from pathogens or tumors, and promising progress in bioprocess
development, such nanostructures offer novel homologous or
heterologous treatment and prevention opportunities against
a variety of malignant and infectious diseases.
[Back to top]
Enhancing the Sensitivity of SAW Sensors with
Nanostructures
Yeswanth L. Rao and Guigen Zhang
In search of a high resolution sensing platform with
the capability of wireless operation, we identified surface
acoustic wave (SAW) devices as the most promising technology.
In this review we discussed the working principles of SAW
devices, their applications in sensing as well as the integration
of nanostructures with SAW devices for achieving enhanced
sensitivity. Future research challenges and benefits of nanostructured
surface acoustic wave devices for biosensing applications
were also addressed.
[Back to top]
Functionalization of CNTs: New Routes Towards
the Development of Novel Electrochemical Sensors
Jian-Shan Ye and Fwu-Shan Sheu
Carbon nanotubes (CNTs) possess high electrical conductivity,
high chemical stability, and extremely high mechanical strength
and modulus. These special properties of both single-walled
and multi-walled CNTs (SWNTs and MWNTs, respectively) have
attracted much attention in electrochemistry. Functionalization
of CNTs is one of the most active fields in carbon nanotube
research, which provides an effective tool to broaden the
spectrum of electrochemical application of CNTs. In this review,
we summarize various approaches to functionalize CNTs for
the development of novel electrochemical sensors. Particular
emphasis is directed to the use of lipid-functionalized CNTs
for sensors and biosensors and for the fabrication of photo
switched-functional devices. The functionalization of the
nanotubes generates a novel, interesting class of nanomaterials,
which combines the properties of the nanotubes and the functional
moiety, thus offering new opportunities in electrochemical
sensors.
[Back to top]
High-Resolution Imaging and Force Measurement
of Individual Membrane Proteins by AFM
Filipp Oesterhelt and Simon Scheuring
Atomic force microscopy (AFM) has developed into a powerful
tool in biophysics to assess the structure and measure the
inter- and intramolecular forces of biological objects. At
the cutting-edge, imaging and force measurements are performed
on individual membrane proteins. Here, recent achievements
of high-resolution imaging and imaging in combination with
controlled force measurement using AFM are reviewed. High-resolution
imaging can yield topographical information to ~ 10 Å
resolution. The comparison with protein structures from X-ray
crystallography shows that surface protruding loops of no
more than 5 aminoacids are reliably contoured. Force measurements
reveal intramolecular forces with a precision of ~ 10 pN.
Again, the comparison with atomic structures shows that forces
between pairs of transmembrane helices are probed. As a major
advantage, the combination of force spectroscopy measurements
with high resolution imaging allow assignment of measured
unfolding events with topographical changes.
[Back to top]
High Resolution Interference Microscopy: A Tool
for Probing Optical Waves in the Far-Field on a Nanometric
Length Scale
Carsten Rockstuhl, Iwan Märki, Toralf Scharf, Martin
Salt, Hans Peter Herzig and René Dändliker
High Resolution Interference Microscopy (HRIM) is a technique
that allows the characterization of amplitude and phase of
electromagnetic wave-fields in the far-field with a spatial
accuracy that corresponds to a few nanometers in the object
plane. Emphasis is put on the precise determination of topological
features in the wave-field, called phase singularities or
vortices, which are spatial points within the electromagnetic
wave at which the amplitude is zero and the phase is hence
not determined. An experimental tool working in transmission
with a resolution of 20 nm in the object plane is
presented and its application to the optical characterization
of various single and periodic nanostructures such as trenches,
gratings, microlenses and computer generated holograms is
discussed. The conditions for the appearance of phase singularities
are theoretically and experimentally outlined and it is shown
how dislocation pairs can be used to determine unknown parameters
from an object. Their corresponding applications to metrology
or in optical data storage systems are analyzed. In addition,
rigorous diffraction theory is used in all cases to simulate
the interaction of light with the nano-optical structures
to provide theoretical confirmation of the experimental results.
[Back to top]
Stress-Induced Reduction of Water Uptake in Clay-reinforced
Epoxy Nanocomposites
Erol Sancaktar and Jason Kuznicki
Exfoliated nano-clay/epoxy composites typically contain approximately
1 nm thick layers of clay dispersed in the polymer matrix.
Owing to the platy morphology of the silicate layers, exfoliated
clay nanocomposites can exhibit dramatically improved barrier
and mechanical properties that are not available with conventional
composite materials. Since epoxy applications may exist in
areas of high moisture content and under mechanically induced
stress, the effect of such stressing on water uptake by epoxy-clay
nanocomposites is of interest. In this work, low viscosity
liquid aromatic diglycidyl ether of bisphenol A (DGEBA) epoxy
resin, Epon 815C, was mixed with Montmorillonite nanoclay
to produce an exfoliated clay – epoxy resin system containing
0.5% nanoclay by weight. These samples were immersed in water
in stressed condition (flexural stress) to assess the effect
of stress on the nanocomposite epoxy system’s water
uptake behavior. Application of the flexural stress affected
the water uptake barrier properties for the nanoclay/epoxy
nanocomposites, with the stress acting to decrease the rate
of absorption as well as to decrease the equilibrium moisture
content in the 0.5% loaded nanocomposite. The results revealed
up to 33% reduction in water uptake for the stressed samples.
[Back to top]
Revisiting Silver Nanoparticle Chemical Synthesis
and Stability by Optical Spectroscopy
Anne Van Hoonacker and Patrick Englebienne
Silver nanocolloids (SNC) are materials useful for wide application
in chemistry and biology which are usually prepared by chemical
reduction of a silver salt. Monodisperse SNC sols are relatively
difficult to prepare compared to gold nanocolloids and few
data are available on the optimization of the synthetic conditions
as well as on the possible evolution of the nanocolloids after
synthesis. To document this, we have carried out a series
of chemical syntheses of SNC by the citrate and borohydride
methods by varying the reductant/AgNO3 ratio. We
characterized the colloids by UV-vis. spectroscopy immediately
after completion of the synthetic process and during several
months of storage. The spectroscopic data collected were verified
for conformity with Mie theory and we retained only the data
fitting to spherical nanoparticles for further analysis. Our
results indicate that the SNC prepared by the citrate method
contain large particles (diameters around 40 nm) which remain
stable during storage. In contrast, the borohydride method
generates smaller SNC. During storage, these nanoparticles
were found to experience alternating nucleation and Ostwald
ripening phases, which were not necessarily dependent on further
silver reduction but rather on particle-particle interactions,
stabilizing only after several months, depending on the synthetic
conditions. We conclude that the citrate method generates
stable SNC that can be safely used after synthesis, although
a safe use during storage of SNC produced by borohydride reduction
depends heavily on the synthetic conditions.
[Back to top]
Dental Nanocomposites
Mui Siang Soh, Alan Sellinger and Adrian UJ. Yap
The development of polymeric dental composites has
revolutionized the field of dentistry over the past 30 years.
This development has been achieved mainly through organic
monomer discovery, modifications in formulation and filler
technology, advances in light curing equipment and efficient
photoinitiators. Despite these developmental advances, dental
composites are still limited by problems such as polymerization
shrinkage and wear resistance. The post-gel polymerization
shrinkage causes significant stresses in the surrounding tooth
structure and composite tooth bonding leading to premature
restoration failure. Other problems such as uncured organic
monomers leaching from the dental composites into the surrounding
gum tissue have caused cytotoxic effects. With the recent
advances in nanotechnology and nanomaterials, it is postulated
that mechanical properties and polymerization shrinkage of
dental composites can be significantly improved.
This review will focus on several recent advances of nanotechnology
implementation into dental composites. The technology involved
in the development of dental nanocomposites and their
enhancement in mechanical properties when compared to the
traditional macrofill and microfill composites will be reviewed.
Some of our work in the development of low shrinking nanocomposites
using functionalized Polyhedral Oligomeric Silsesquioxane
(POSS) molecule will also be discussed.
|
