| Current
Nanoscience
ISSN: 1573-4137
Current Nanoscience
Volume 3, Number 4, November 2007
Contents
Fluorescent Imaging Applications of Quantum Dot Probes
Pp. 273-284
Michael R. Warnement, Ian D. Tomlinson and Sandra J. Rosenthal
[Abstract]
Synthesis of Morphology-Controlled Titania Nanocrystals
and Application for Dye-Sensitized Solar Cells Pp.
285-295
Motonari Adachi, Jinting Jiu and Seiji Isoda
[Abstract]
Self-Assembled Photonic Crystals and Templated Nanomaterials
Pp. 296-305
Peng Jiang, Chih-Hung Sun, Nicolas C. Linn, Brian J. Ho
and Srinivasan Venkatesh
[Abstract]
From Sol-Gel Processing to Bio-Inspired Materials
Synthesis Pp. 306-328
Peer Löbmann
[Abstract]
Intracellular Delivery of Nanocarriers for Cancer
Therapy Pp. 329-338
Yah-el Har-el and Yoshinori Kato
[Abstract]
Improved Oral Absorption of Carbamazepine from 1-O
Alkylglycerol Stabilized o/w Nanoemulsions Pp. 339-344
B. Madhusudhan, D. Rambhau, S.S. Apte and D. Gopinath
[Abstract]
Nano-Science Revelations in Bone Research
Pp. 345-351
Tue Hassenkam, René Brüggebusch Svensson and
Maksim Zalkovskij
[Abstract]
Abstracts
[Back to top]
Fluorescent Imaging Applications of Quantum
Dot Probes
Michael R. Warnement, Ian D. Tomlinson and Sandra J. Rosenthal
Quantum dots (QDs) have rapidly emerged as an attractive alternative
to conventional organic fluorophores in a variety of biological
imaging applications. Their improved photostability allows
for long-term dynamic imaging of cellular processes and their
narrow, size-tunable emission permits unprecedented multiplexing
capabilities. Additionally, the inherent brightness of core/shell
QDs, with quantum yields capable of exceeding 85%, provides
increased sensitivity for both diagnostic screening and single
molecule tracking applications. To date, the primary focus
of research in this field has been directed towards modifying
the surface chemistries of the QDs to introduce biological
specificity while, at the same time, limiting nonspecific
cellular interactions. As such, biomolecules such as antibodies,
peptides, streptavidin and biotin have all been conjugated
to QDs and been used to demonstrate specific labeling of cellular
targets. Additionally, polyethylene glycol (PEG) modification
of the QD surface has been shown to limit nonspecific interactions.
The use of small molecule QD-conjugates has also been demonstrated
as an effective means for targeted labeling of membrane associated
receptors. This approach introduces specificity via ligand-receptor
interactions, resulting in a highly modular system which is
easily modified to interrogate a wide variety of cellular
targets. This article provides a comprehensive review of the
current status of QD imaging applications in biological systems
with a particular emphasis on the design and application of
small molecule nanoconjugates.
[Back to top]
Synthesis of Morphology-Controlled Titania Nanocrystals
and Application for Dye-Sensitized Solar Cells
Motonari Adachi, Jinting Jiu and Seiji Isoda
Development of renewable energy resources in the near future
is an urgent issue. One attractive strategy is the development
of dye-sensitized solar cells (DSSCs); they are extremely
promising, because they are made of low-cost materials and
do not need elaborate apparatus to manufacture. Titania is
the most promising material for the electrode of DSSCs, and
then morphological control and carrier transport optimization
are the key properties needed in titanium oxide materials
for DSSCs. We review the formation procedures and characteristics
of titanium oxide nanocrystalline products, which exhibit
various morphological shapes in nanometer scale, i. e., nanotubes,
nanorods, nanowires and nanosheets, and their arrays. We also
present new findings in our laboratory on the formation of
titania nanorods and network structures of single-crystal-like
titania nanowires as well as their application for DSSCs.
In order to evaluate the electrical properties of DSSCs with
electrodes composed of various nanoscale titania materials,
measurement procedures for electron transport processes in
DSSCs are also reviewed, together with our results in electrochemical
impedance spectroscopy to determine various parameters concerning
about electron transport.
[Back to top]
Self-Assembled Photonic Crystals and Templated Nanomaterials
Peng Jiang, Chih-Hung Sun, Nicolas C. Linn, Brian J. Ho
and Srinivasan Venkatesh
Photonic crystals offer unprecedented opportunities for
the realization of all-optical integrated circuits and optical
computation. Colloidal self-assembly provides a much cheaper
and simpler alternative to complex nanolithography in creating
three dimensional photonic crystals operating at visible and
telecommunication wavelengths. The self-organized colloidal
arrays can also be used as templates in fabricating nanostructured
materials that have important technological applications ranging
from biosensors to plasmonic devices. The present paper reviews
recent advances in the assembly of colloidal photonic crystals,
mainly focuses on the spin-coating technological platform
that is compatible with standard microfabrication, enabling
mass-fabrication of wafer-scale colloidal photonic crystals.
Various templating approaches based on the spin-coating platform
for making periodic nanomaterials and their potential applications
are also addressed.
[Back to top]
From Sol-Gel Processing to Bio-Inspired Materials
Synthesis
Peer Löbmann
The improvement of materials performance and their respective
processing routes ever has been the driving force for material
science and engineering. For the preparation of non-metallic
inorganic materials the synthesis from chemical precursors
is a field of steadily increasing scientific and industrial
importance: Products in a broad variety of compositions can
be obtained by sol-gel techniques. The shaping of intermediates
allows the specific preparation of many microarchitectural
configurations such as powders, fibers, thin films and aerogels.
For purely inorganic products the sintering temperatures are
low compared to conventional mixed-oxide ceramic processing
which enables e.g. the coating of glasses and metals. Hybrid
inorganic-organic compositions combine some advantages of
polymers and ceramics.
Nature has found amazing alternative ways to produce high-performance
inorganic-organic composites at ambient temperatures under
physiological conditions: Teeth, bone and nacre are self-evident
examples for the capability of biomineralization processes.
Even though many aspects of the related mechanisms in
vivo are not yet fully understood, the utilization of
the basic strategies of natural biomineralization has become
a challenge to material scientist in an interdisciplinary
approach.
In this paper the strong points of sol-gel processing are
highlighted, its limitations are discussed and related to
the unique characteristics of natural biomineralization. Subsequently
biomimetic and biologically-inspired material syntheses routes
are reviewed which try to compensate the shortcomings of sol-gel
techniques.
[Back to top]
Intracellular Delivery of Nanocarriers for Cancer
Therapy
Yah-el Har-el and Yoshinori Kato
Drug delivery systems largely contribute to cancer therapy
in terms of tumor targeting and controlled release of cargo
molecules. While targeting of tumor “tissue” has
been achieved using nanocarriers, delivery of cargo molecules
into tumor cells is still challenging. Intracellular delivery
of nanocarriers is an essential process to overcome multi-drug
resistance and for the delivery of cargo molecules for both
therapy and vaccine applications. Nanocarriers may gain access
to the interior of target cells either non-specifically, as
in adsorptive endocytosis, or specifically, as in receptor-mediated
endocytosis. Once internalized, they must subsequently break
free of their endosomal compartments in order to deliver their
cargo into either the cytosol or nucleus. If the nucleus is
the target, as in DNA delivery, the nanocarrier must then
traffick to the perinuclear region and deliver the cargo into
the nucleus, either by physically transporting DNA through
the nuclear pore complex (NPC), or by releasing DNA at the
door of the NPC, allowing free DNA to gain access. This review
article includes both principles and mechanisms of intracellular
delivery of nanocarriers, and gives a few examples of their
application.
[Back to top]
Improved Oral Absorption of Carbamazepine from 1-O
Alkylglycerol Stabilized o/w Nanoemulsions
B. Madhusudhan, D. Rambhau, S.S. Apte and D. Gopinath
Absorption of carbamazepine (CBZ) from gastrointestinal tract
is slow and erratic. In order to improve oral absorption of
CBZ, 1-O-alkylglycerol/lecithin stabilized o/w nanoemulsions
incorporating CBZ in oil phase were prepared and characterized.
Nanoemulsions had a size around 200 nm. Their oral bioavailability
in rabbits and in situ intestinal absorption in rats
were evaluated. In in situ studies, the test and
control systems were charged into intestine and instead of
lumenal samples, blood samples from tail vein were analyzed
for CBZ content. These results indicated faster rate and higher
extent of absorption for nanoemulsions than control (a micron
sized aqueous CBZ suspension). The high rate of release from
and adherence of nano-oil particles to mucosa seems to have
enhanced absorption of CBZ in this model. Among nanoemulsions
1-O-decylglycerol/lecithin stabilized system showed
faster rate of absorption, higher Cmax
and area under the curve (AUC). Improvement in oral absorption
of CBZ from nanoemulsions was also evident from the bioavailability
study conducted on rabbits. Peak serum concentration (Cmax)
and AUC were higher for nanoemulsions than control. This
study indicated increase in absorption and decrease in disposition
of CBZ when administered as nanoemulsions. Broadly the globule
size and per-meabilization effect due to 1-O-alkylglycerols
seem to be the factors responsible for enhanced absorption
due to nanoemulsions in in situ and in vivo
experiments. However the permeability effect of 1-O-alkylglycerol
was prominent only in in situ experiments.
[Back to top]
Nano-Science Revelations in Bone Research
Tue Hassenkam, René Brüggebusch Svensson and
Maksim Zalkovskij
When diagnosing human bone as Osteoporotic, the quantity of
bone, assessed by measurement of the bone mineral density
(BMD), is often used in the estimate of fracture resistance.
However, bone quantity is only one of the factors that determine
the ability of bone to resist fracture. Bone quality describes
the remaining characteristics and traits that determine the
fracture resistance of bone.
Bone is a composite material, consisting of minerals embedded
in an organic matrix. The mechanical properties of a composite
material are determined by the structural interactions of
the individual constituents, which is different from the sum
of mechanical properties of the individual constituents. The
size of the building blocks of bone is in the nanometer range,
the diameter of collagen is 100 nanometers and mineral plates
range from the typical diameter of 10-20 nanometers to 200
nanometers. To understand the ability of bone to resist fracture,
and its quality as a tissue, it is important to appreciate
the intricate interplay between these building blocks. This
review focuses on the parameters that contribute to bone quality,
including recent evidence for the roles of factors such as
collagen cross-linking, micro-cracking and bone remodelling.
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