737 research outputs found
Trapping tetracycline-loaded nanoparticles into polycaprolactone fiber networks for periodontal regeneration therapy
The controlled delivery of antibiotics, anti-inflammatory agents, or chemotherapeutic agents to
the periodontal site is a recognized strategy to improve the efficiency of regenerative processes of
hard tissues. A novel approach based on the trapping of tetracycline hydrochloride–loaded particles
in polycaprolactone nanofibers was used to guide the regeneration processes of periodontal
tissue at the gum interface. Chitosan nanoparticles loaded with different levels of tetracycline
hydrochloride (up to 5% wt) were prepared by solution nebulization induced by electrical forces
(i.e. electrospraying). The fine tuning of process parameters allows to obtain nanoparticles with
tailored sizes ranging from 0.485 ± 0.147 μm to 0.639 ± 0.154 μm. The tetracycline hydrochloride
release profile had a predominant burst effect for the first 70% of release followed by a relatively
slow release over 24 h, which is promising for oral drug delivery. We also demonstrated that
trapping tetracycline hydrochloride–loaded particles with submicrometer diameters into a
polycaprolactone fiber network contributed to slowing the release of tetracycline hydrochloride
from the nanoparticles, thus providing a more prolonged release in the periodontal pocket during
clinical therapy. Preliminary studies on human mesenchymal stem cells confirm the viability of
cells up to 5 days after culture, and thereby, validate the use of nanoparticle-/nanofiber-integrated
systems in periodontal therapie
Ibuprofen-loaded poly(trimethylene carbonate-co-e-caprolactone) electrospun fibres for nerve regeneration
The development of scaffolds that combine the delivery of drugs with the physical support provided by electrospun fibres holds great potential in the field of nerve regeneration. Here it is proposed the incorporation of ibuprofen, a well-known non-steroidal anti-inflammatory drug, in electrospun fibres of the statistical copolymer poly(trimethylene carbonate-co-e-caprolactone) [P(TMC-CL)] to serve as a drug delivery system to enhance axonal regeneration in the context of a spinal cord lesion, by limiting the inflammatory response. P(TMC-CL) fibres were electrospun from mixtures of dichloromethane (DCM) and dimethylformamide (DMF). The solvent mixture applied influenced fibre morphology, as well as mean fibre diameter, which decreased as the DMF content in solution increased. Ibuprofen-loaded fibres were prepared from P(TMC-CL) solutions containing 5% ibuprofen (w/w of polymer). Increasing drug content to 10% led to jet instability, resulting in the formation of a less homogeneous fibrous mesh. Under the optimized conditions, drug-loading efficiency was above 80%. Confocal Raman mapping showed no preferential distribution of ibuprofen in P(TMC-CL) fibres. Under physiological conditions ibuprofen was released in 24h. The release process being diffusion-dependent for fibres prepared from DCM solutions, in contrast to fibres prepared from DCM-DMF mixtures where burst release occurred. The biological activity of the drug released was demonstrated using human-derived macrophages. The release of prostaglandin E 2 to the cell culture medium was reduced when cells were incubated with ibuprofen-loaded P(TMC-CL) fibres, confirming the biological significance of the drug delivery strategy presented. Overall, this study constitutes an important contribution to the design of a P(TMC-CL)-based nerve conduit with anti-inflammatory properties.This work was financed by FEDER funds through the Programa Operacional Factores de Competitividade – COMPETE and by Portuguese funds through FCT – Fundação para a Ciência e a Tecnologia in the framework of the project PEst-C/SAU/LA0002/2011 and PTDC/CTM-NAN/115124/2009, PTDC/SAU-ONC/112511/2009. L.R.P. thanks FCT for her PhD grant (SFRH /BD / 46015 / 2008) and M.J.O. is a FCT Ciência 200 7 fello w. The authors acknowledge Centro de Materiais da Universidade do Por to (C EMUP; RE EQ/1062/C TM/20 05 from FCT ) for t he 1HNMR analysis
Muon Energy Estimate Through Multiple Scattering with the Macro Detector
Muon energy measurement represents an important issue for any experiment
addressing neutrino induced upgoing muon studies. Since the neutrino
oscillation probability depends on the neutrino energy, a measurement of the
muon energy adds an important piece of information concerning the neutrino
system. We show in this paper how the MACRO limited streamer tube system can be
operated in drift mode by using the TDC's included in the QTPs, an electronics
designed for magnetic monopole search. An improvement of the space resolution
is obtained, through an analysis of the multiple scattering of muon tracks as
they pass through our detector. This information can be used further to obtain
an estimate of the energy of muons crossing the detector. Here we present the
results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines,
to provide a full check of the electronics and to exploit the feasibility of
such a multiple scattering analysis. We show that by using a neural network
approach, we are able to reconstruct the muon energy for 40 GeV. The
test beam data provide an absolute energy calibration, which allows us to apply
this method to MACRO data.Comment: 25 pages, 11 figures, Submitted to Nucl. Instr. & Meth.
Low energy atmospheric muon neutrinos in MACRO
We present the measurement of two event samples induced by atmospheric
of average energy . In the first sample,
the neutrino interacts inside the MACRO detector producing an upward-going muon
leaving the apparatus. The ratio of the number of observed to expected events
is with an angular
distribution similar to that expected from the Bartol atmospheric neutrino
flux. The second is a mixed sample of internally produced downward-going muons
and externally produced upward-going muons stopping inside the detector. These
two subsamples are selected by topological criteria; the lack of timing
information makes it impossible to distinguish stopping from downgoing muons.
The ratio of the number of observed to expected events is . Using the ratio of the two subsamples (for
which most theoretical uncertainties cancel) we can test the pathlength
dependence of the oscillation hypothesis. The probability of agreement with the
no-oscillation hypothesis is 5% .
The deviations of our observations from the expectations has a preferred
interpretation in terms of oscillations with maximal mixing and
. These parameters are in agreement
with our results from upward throughgoing muons, induced by of much
higher energies.Comment: 7 pages, 6 figures. Submitted to Phys. Lett.
Search for diffuse neutrino flux from astrophysical sources with MACRO
Many galactic and extragalactic astrophysical sources are currently
considered promising candidates as high energy neutrino emitters. Astrophysical
neutrinos can be detected as upward-going muons produced in charged-current
interactions with the medium surrounding the detector. The expected neutrino
fluxes from various models start to dominate on the atmospheric neutrino
background at neutrino energies above some tens of TeV. We present the results
of a search for an excess of high energy upward-going muons among the sample of
data collected by MACRO during ~5.8 years of effective running time. No
significant evidence for this signal was found. As a consequence, an upper
limit on the flux of upward-going muons from high-energy neutrinos was set at
the level of 1.7 10^(-14) cm^(-2) s^(-1) sr^(-1).
The corresponding upper limit for the diffuse neutrino flux was evaluated
assuming a neutrino power law spectrum. Our result was compared with
theoretical predictions and upper limits from other experiments.Comment: 19 pages, 8 figures, 2 table
Neutrino astronomy with the MACRO detector
High energy gamma ray astronomy is now a well established field and several
sources have been discovered in the region from a few GeV up to several TeV. If
sources involving hadronic processes exist, the production of photons would be
accompanied by neutrinos too. Other possible neutrino sources could be related
to the annihilation of WIMPs at the center of galaxies with black holes.
We present the results of a search for point-like sources using 1100
upward-going muons produced by neutrino interactions in the rock below and
inside the MACRO detector in the underground Gran Sasso Laboratory. These data
show no evidence for a possible neutrino point-like source or for possible
correlations between gamma ray bursts and neutrinos. They have been used to set
flux upper limits for candidate point-like sources which are in the range
10^-14-10^-15 cm-2 s-1.Comment: 37 pages, 15 figures, replacement due to a typo in tab. 6, AASLaTex,
submitted to Ap
Limits on dark matter WIMPs using upward-going muons in the MACRO detector
We perform an indirect search for Weakly Interacting Massive Particles
(WIMPs) using the MACRO detector to look for neutrino-induced upward-going
muons resulting from the annihilation of WIMPs trapped in the Sun and Earth.
The search is conducted in various angular cones centered on the Sun and Earth
to accommodate a range of WIMP masses. No significant excess over the
background from atmospheric neutrinos is seen and limits are placed on the
upward-going muon fluxes from Sun and Earth. These limits are used to constrain
neutralino particle parameters from supersymmetric theory, including those
suggested by recent results from DAMA/NaI.Comment: 14 pages, 7 figures, submitted to Phys. Rev.
Measurement of the residual energy of muons in the Gran Sasso underground Laboratories
The MACRO detector was located in the Hall B of the Gran Sasso underground
Laboratories under an average rock overburden of 3700 hg/cm^2. A transition
radiation detector composed of three identical modules, covering a total
horizontal area of 36 m^2, was installed inside the empty upper part of the
detector in order to measure the residual energy of muons. This paper presents
the measurement of the residual energy of single and double muons crossing the
apparatus. Our data show that double muons are more energetic than single ones.
This measurement is performed over a standard rock depth range from 3000 to
6500 hg/cm^2.Comment: 28 pages, 9 figure
Observation of the Shadowing of Cosmic Rays by the Moon using a Deep Underground Detector
Using data collected by the MACRO experiment during the years 1989-1996, we
show evidence for the shadow of the moon in the underground cosmic ray flux
with a significance of 3.6 sigma. This detection of the shadowing effect is the
first by an underground detector. A maximum-likelihood analysis is used to
determine that the angular resolution of the apparatus is 0.9+/-0.3 degrees.
These results demonstrate MACRO's capabilities as a muon telescope by
confirming its absolute pointing ability and quantifying its angular
resolution.Comment: 14 pages, 8 figures Submitted to Phys. Rev.
The Observation of Up-going Charged Particles Produced by High Energy Muons in Underground Detectors
An experimental study of the production of up-going charged particles in
inelastic interactions of down-going underground muons is reported, using data
obtained from the MACRO detector at the Gran Sasso Laboratory. In a sample of
12.2 10^6 single muons, corresponding to a detector livetime of 1.55 y, 243
events are observed having an up-going particle associated with a down-going
muon. These events are analysed to determine the range and emission angle
distributions of the up-going particle, corrected for detection and
reconstruction efficiency. Measurements of the muon neutrino flux by
underground detectors are often based on the observation of through-going and
stopping muons produced in interactions in the rock below the
detector. Up-going particles produced by an undetected down-going muon are a
potential background source in these measurements. The implications of this
background for neutrino studies using MACRO are discussed.Comment: 18 pages, 9 figures. Accepted by Astrop. Physic
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