117 research outputs found
Pioglitazone-Loaded PLGA Nanoparticles: Towards the Most Reliable Synthesis Method
Recent findings have proved the benefits of Pioglitazone (PGZ) against atherosclerosis and type 2 diabetes. Since the systematic and controllable release of this drug is of significant importance, encapsulation of this drug in nanoparticles (NPs) can minimize uncontrolled issues. In this context, drug delivery approaches based on several poly(lactic-co-glycolic acid) (PLGA) nanoparticles have been rising in popularity due to their promising capabilities. However, a fully reliable and reproducible synthetic methodology is still lacking. In this work, we present a rational optimization of the most critical formulation parameters for the production of PGZ-loaded PLGA NPs by the single emulsification-solvent evaporation or nanoprecipitation methods. We examined the influence of several variables (e.g., component concentrations, phases ratio, injection flux rate) on the synthesis of the PGZ-NPs. In addition, a comparison of these synthetic methodologies in terms of nanoparticle size, polydispersity index (PDI), zeta potential (ζp), drug loading (DL%), entrapment efficiency (EE%), and stability is offered. According to the higher entrapment efficiency content, enhanced storage time and suitable particle size, the nanoprecipitation approach appears to be the simplest, most rapid and most reliable synthetic pathway for these drug nanocarriers, and we demonstrated a very slow drug release in PBS for the best formulation obtained by this synthesis.Recent findings have proved the benefits of Pioglitazone (PGZ) against atherosclerosis and type 2 diabetes. Since the systematic and controllable release of this drug is of significant importance, encapsulation of this drug in nanoparticles (NPs) can minimize uncontrolled issues. In this context, drug delivery approaches based on several poly(lactic-co-glycolic acid) (PLGA) nanoparticles have been rising in popularity due to their promising capabilities. However, a fully reliable and reproducible synthetic methodology is still lacking. In this work, we present a rational optimization of the most critical formulation parameters for the production of PGZ-loaded PLGA NPs by the single emulsification-solvent evaporation or nanoprecipitation methods. We examined the influence of several variables (e.g., component concentrations, phases ratio, injection flux rate) on the synthesis of the PGZ-NPs. In addition, a comparison of these synthetic methodologies in terms of nanoparticle size, polydispersity index (PDI), zeta potential (ζp), drug loading (DL%), entrapment efficiency (EE%), and stability is offered. According to the higher entrapment efficiency content, enhanced storage time and suitable particle size, the nanoprecipitation approach appears to be the simplest, most rapid and most reliable synthetic pathway for these drug nanocarriers, and we demonstrated a very slow drug release in PBS for the best formulation obtained by this synthesis
Metamorphosis of a Quantum Hall Bilayer State into a Composite Fermion Metal
Composite fermion metal states emerge in quantum Hall bilayers at total
Landau level filling factor =1 when the tunneling gap collapses by
application of in-plane components of the external magnetic field. Evidence of
this transformation is found in the continua of spin excitations observed by
inelastic light scattering below the spin-wave mode at the Zeeman energy. The
low-lying spin modes are interpreted as quasiparticle excitations with
simultaneous changes in spin orientation and composite fermion Landau level
index.Comment: 4 pages 4 figure
Observation of collapse of pseudospin order in bilayer quantum Hall ferromagnets
The Hartree-Fock paradigm of bilayer quantum Hall states with finite
tunneling at filling factor =1 has full pseudospin ferromagnetic order
with all the electrons in the lowest symmetric Landau level. Inelastic light
scattering measurements of low energy spin excitations reveal major departures
from the paradigm at relatively large tunneling gaps. The results indicate the
emergence of a novel correlated quantum Hall state at =1 characterized by
reduced pseudospin order. Marked anomalies occur in spin excitations when
pseudospin polarization collapses by application of in-plane magnetic fields.Comment: ReVTeX4, 4 pages, 3 EPS figure
Soft Magnetorotons and Broken-Symmetry States in Bilayer Quantum Hall Ferromagnets
The recent report on the observation of soft magnetorotons in the dispersion
of charge-density excitations across the tunneling gap in coupled bilayers at
total Landau level filling factor is reviewed. The inelastic light
scattering experiments take advantage of the breakdown of wave-vector
conservation that occurs under resonant excitation. The results offer evidence
that in the quantum Hall state there is a roton that softens and sharpens
markedly when the phase boundary for transitions to highly-correlated
compressible states is approached. These findings are interpreted with
Hartree-Fock evaluations of the dynamic structure factor. The model includes
the effect of disorder in the breakdown of wave-vector conservation and
resonance enhancement profiles within a phenomenological approach. These
results link the softening of magnetorotons to enhanced excitonic Coulomb
interactions in the ferromagnetic bilayers.Comment: 6 pages, 5 figures; conference: EP2DS-1
Green fluorescent Protein-based pH indicators for in vivo use: a review
Green fluorescent protein (GFP) and its variants have been used as fluorescent reporters in a variety of applications for monitoring dynamic processes in cells and organisms, including gene expression, protein localization, and intracellular dynamics. GFP fluorescence is stable, species-independent, and can be monitored noninvasively in living cells by fluorescence microscopy, flow cytometry, or macroscopic imaging techniques. Owing to the presence of a phenol group on the chromophore, most GFP variants display pH-sensitive absorption and fluorescence bands. Such behavior has been exploited to genetically engineer encodable pH indicators for studies of pH regulation within specific intracellular compartments that cannot be probed using conventional pH-sensitive dyes. These pH indicators contributed to shedding light on a number of cell functions for which intracellular pH is an important modulator. In this review we discuss the photophysical properties that make GFPs so special as pH indicators for in vivo use and we describe the probes that are utilized most by the scientific community.Green fluorescent protein (GFP) and its variants have been used as fluorescent reporters in a variety of applications for monitoring dynamic processes in cells and organisms, including gene expression, protein localization, and intracellular dynamics. GFP fluorescence is stable, species-independent, and can be monitored noninvasively in living cells by fluorescence microscopy, flow cytometry, or macroscopic imaging techniques. Owing to the presence of a phenol group on the chromophore, most GFP variants display pH-sensitive absorption and fluorescence bands. Such behavior has been exploited to genetically engineer encodable pH indicators for studies of pH regulation within specific intracellular compartments that cannot be probed using conventional pH-sensitive dyes. These pH indicators contributed to shedding light on a number of cell functions for which intracellular pH is an important modulator. In this review we discuss the photophysical properties that make GFPs so special as pH indicators for in vivo use and we describe the probes that are utilized most by the scientific community. © 2008 Springer-Verlag
Intersubband absorption linewidth in GaAs quantum wells due to scattering by interface roughness, phonons, alloy disorder, and impurities
We calculate the intersubband absorption linewidth in quantum wells (QWs) due
to scattering by interface roughness, LO phonons, LA phonons, alloy disorder,
and ionized impurities, and compare it with the transport energy broadening
that corresponds to the transport relaxation time related to electron mobility.
Numerical calculations for GaAs QWs clarify the different contributions of each
individual scattering mechanism to absorption linewidth and transport
broadening. Interface roughness scattering contributes about an order of
magnitude more to linewidth than to transport broadening, because the
contribution from the intrasubband scattering in the first excited subband is
much larger than that in the ground subband. On the other hand, LO phonon
scattering (at room temperature) and ionized impurity scattering contribute
much less to linewidth than to transport broadening. LA phonon scattering makes
comparable contributions to linewidth and transport broadening, and so does
alloy disorder scattering. The combination of these contributions with
significantly different characteristics makes the absolute values of linewidth
and transport broadening very different, and leads to the apparent lack of
correlation between them when a parameter, such as temperature or alloy
composition, is changed. Our numerical calculations can quantitatively explain
the previously reported experimental results.Comment: 17 pages, including 15 figure
Observation of soft magnetorotons in bilayer quantum Hall ferromagnets
Inelastic light scattering measurements of low-lying collective excitations
of electron double layers in the quantum Hall state at total filling nu_T=1
reveal a deep magnetoroton in the dispersion of charge-density excitations
across the tunneling gap. The roton softens and sharpens markedly when the
phase boundary for transitions to highly correlated compressible states is
approached. The findings are interpreted with Hartree-Fock evaluations that
link soft magnetorotons to enhanced excitonic Coulomb interactions and to
quantum phase transitions in the ferromagnetic bilayers.Comment: ReVTeX4, 4 pages, 4 EPS figure
Spectroscopy of soft modes and quantum phase transitions in coupled electron bilayers
Strongly-correlated two-dimensional electrons in coupled semiconductor
bilayers display remarkable broken symmetry many-body states under accessible
and controllable experimental conditions. In the cases of continuous quantum
phase transitions soft collective modes drive the transformations that link
distinct ground states of the electron double layers. In this paper we consider
results showing that resonant inelastic light scattering methods detect soft
collective modes of the double layers and probe their evolution with
temperature and magnetic field. The light scattering experiments offer venues
of research of fundamental interactions and continuous quantum phase
transitions in low-dimensional electron liquids.Comment: 10 pages, 7 figure
Graphene promotes axon elongation through local stall of Nerve Growth Factor signaling endosomes
Several works reported increased differentiation of neuronal cells grown on
graphene; however, the molecular mechanism driving axon elongation on this
material has remained elusive. Here, we study the axonal transport of nerve
growth factor (NGF), the neurotrophin supporting development of peripheral
neurons, as a key player in the time course of axonal elongation of dorsal root
ganglion neurons on graphene. We find that graphene drastically reduces the
number of retrogradely transported NGF vesicles in favor of a stalled
population in the first two days of culture, in which the boost of axon
elongation is observed. This correlates with a mutual charge redistribution,
observed via Raman spectroscopy and electrophysiological recordings.
Furthermore, ultrastructural analysis indicates a reduced microtubule distance
and an elongated axonal topology. Thus, both electrophysiological and
structural effects can account for graphene action on neuron development.
Unraveling the molecular players underneath this interplay may open new avenues
for axon regeneration applications
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