Lingulodinium polyedra is a microalga capable of producing toxins with antibacterial, antitumoral, and antifungal properties. Our aim was to internalize molybdenum trioxide nanoparticles (MoO3NPs) into the microalgae Lingulodinium polyedra, leveraging the optical properties of MoO3NPs to enhance its solar absorption and other mechanisms such as charge carriers in its photosynthetic system, thereby increasing redox reactions during the photosynthesis process. Molybdenum nanoparticles (MoNPs) were synthesized using the Laser Ablation of Solids in Liquids (LASL) method with ultrashort pulse lasers. MoNPs were characterized by UV-Vis spectroscopy, Raman spectroscopy, and Transmission Electron Microscopy (TEM). Notably, the MoNPs exhibited interesting optical properties, including an absorption peak around 800 nm, identified as a plasmonic band absorption. Using the Tauc model for semiconductors, we determined the band gap energy to be approximately 2.7 eV. We compared the evolution of MoNPs in distilled water and sterilized seawater (SSW). Over time, both environments led to the formation of MoO3 nanoparticles (MoO3NPs), with the MoNPs in distilled water showing a significantly different absorption spectrum compared to those in SSW. Furthermore, MoNPs were internalized into the microalgae L. polyedra. Growth curve analyses revealed that treatments with MoO3NPs resulted in increased cell density and a longer lifespan compared to untreated algae. Additionally, through Multiple Reaction Monitoring (MRM), characteristic molecular compounds of pectenotoxins (PTXs) were detected exclusively in the dinoflagellates that internalized the MoO3 nanoparticles.
The importance of a constant blood glucose concentration monitoring in order to keep a regular control for diabetic patients, had been established from the medical approach. Several studies accept the necessity of exploring alternatives for the traditional digital glucometer, given the pain and discomfort related to this technique, which can lead to a compromised control of the disease. Numerous efforts based on the application of IR spectroscopy for non-invasive glucose quantification had been done with favorable, yet not conclusive results, given in part from the research protocols defined, which had not considered the compounds involved in the glucose regulation mechanism, it’s known that this substances have an important role from both the biochemical and optical perspective. Therefore it’s necessary to apply an interdisciplinary study based on the properties of the glucose in the human body, to understand the interaction between this substance, its surroundings and light from the mid-IR region. From our results, the window of interest for blood glucose is in the spectral range of 1150-950cm-1. This study proposes a comprehensive approach of glucose quantification by means of mid-IR absorption spectroscopy, considering important biochemical, physiological and optical properties, we also propose the use of chemometric tools for the analysis of the bio-optical signals. The results of this work would help to define the right parameters aiming to obtain an optical glucose quantification system and protocol.
Bacterial infection of cranial implants remains a major cause of implant failure, and often requires surgical intervention to remove and replace the fouled implant. Novel transparent implants may allow for mitigation of infection using optical therapies, without the need for invasive surgeries. In this study, we investigate a combined treatment with ZnO nanoparticles and femtosecond laser pulses to inhibit the growth of Escherichia coli (E. Coli) in vitro. The combined effect has shown a substantial reduction in the number of CFU/mL after incubation compared with no treatment.
We demonstrate a total bacterial inactivation technique by ultrashort pulse direct-laser irradiation that does not require any external agent. Near-infrared fs laser pulses at 89 MHz repetition rate were used to irradiate solutions of distilled water with >107 cell/ml of wild strain of E. coli, showing they can be inactivated with fluences per pulse as low as ~1mJ/cm2.
We present a time-resolved study of the interaction of nanosecond laser pulses with tissue phantoms. When a laser pulse interacts with a material, optical energy is absorbed by a combination of linear (heat generation and thermoelastic expansion) and nonlinear absorption (expanding plasma), according to both the laser light irradiance and material properties. The objective is to elucidate the contribution of linear and nonlinear optical absorption to bubble formation. Depending on the local temperatures and pressures reached, both interactions may lead to the formation of bubbles. We discuss three experimental approaches: piezoelectric sensors, time-resolved shadowgraphy, and time-resolved interferometry, to follow the formation of bubbles and measure the pressure originated by 6 ns laser pulses interacting with tissue phantoms. We studied the bubble formation and pressure transients for varying linear optical absorption and for radiant exposures above and below threshold for bubble formation. We report a rapid decay (of 2 orders of magnitude) of the laser-induced mechanical pressure measured (by time-resolved shadowgraphy) very close to the irradiation spot and beyond 1 mm from the irradiation site (by the piezoelectric sensor). Through time-resolved interferometry measurements, we determined that bubble formation can occur at marginal temperature increments as low as 3°C.
We report on the interaction of high repetition rate (MHz) Ti: sapphire laser pulses with a spiropyran polymer (MIC1).
Such a polymer is photochromic, wich has potential applications in integrated optical devices. A thin film of polymer
deposited on a glass substrate is irradiated with ultrashort pulses (66 fs) from a Ti: sapphire laser. We demonstrate that it
is possible to induce an absorption band in the visible by the use of femtosecond pulses via a two-photon excitation
process; this might be useful to accomplish waveguide-like structures formation with photochromic response.
Nanosecond long laser pulses are used in medical applications where precise tissue ablation with minimal
thermal and mechanical collateral damage is required. When a laser pulse is incident on a material, optical energy will be
absorbed by a combination of linear and nonlinear absorption according to both: laser light irradiance and material
properties. In the case of water or gels, the first results in heat generation and thermoelastic expansion; while the second
results in an expanding plasma formation that launches a shock wave and a cavitation/boiling bubble. Plasma formation
due to nonlinear absorption of nanosecond laser pulses is originated by a combination of multiphoton ionization and
thermionic emission of free electrons, which is enhanced when the material has high linear absorption coefficient. In this
work, we present three experimental approaches to study pressure transients originated when 6 ns laser pulses are
incident on agar gels and water with varying linear absorption coefficient, using laser radiant exposures above and below
threshold for bubble formation: (a) PVDF sensors, (b) Time-resolved shadowgraphy and (c) Time-resolved
interferometry. The underlying hypothesis is that pressure transients are composed of the superposition of both: shock
wave originated by hot expanding plasma resulting from nonlinear absorption of optical energy and, thermoelastic
expansion originated by heat generation due to linear absorption of optical energy. The objective of this study is to carry
out a comprehensive experimental analysis of the mechanical effects that result when tissue models are irradiated with
nanosecond laser pulses to elucidate the relative contribution of linear and nonlinear absorption to bubble formation.
Furthermore, we investigate cavitation bubble formation with temperature increments as low as 3 °C.
Nanosecond long laser pulses are used in medical applications where precise tissue ablation with minimal thermal and
mechanical collateral damage is required. When a laser pulse is incident on a material, optical energy will be absorbed
by a combination of linear and nonlinear absorption according to both: laser light intensity and material properties. In the
case of water or gels, the first results in heat generation and thermoelastic expansion; while the second results in an
expanding plasma formation that launches a shock wave and a cavitation/boiling bubble. Plasma formation due to
nonlinear absorption of nanosecond laser pulses is originated by a combination of multiphoton ionization and thermionic
emission of free electrons, which is enhanced when the material has high linear absorption coefficient. In this work, we
present measurements of pressure transients originated when 6 ns laser pulses are incident on agar gels with varying
linear absorption coefficient, mechanical properties and irradiation geometry using laser radiant exposures above
threshold for bubble formation. The underlying hypothesis is that pressure transients are composed of the superposition
of both: shock wave originated by hot expanding plasma resulting from nonlinear absorption of optical energy and,
thermoelastic expansion originated by heat generation due to linear absorption of optical energy. The objective of this
work is to evaluate the relative contribution of each absorption mechanism to mechanical effects in agar gel. Real time
pressure transients are recorded with PVDF piezoelectric sensors and time-resilved imaging from 50 μm to 10 mm away
from focal point.
Cell mono-layers were irradiated with nanosecond laser pulses under two distinct scenarios: (a) with culturing medium
positioning the beam waist at different stand-off distances γ and (b) without cell culturing medium, positioning the beam
waist directly on top of the cell mono-layer. Damaged cells were marked with Trypan Blue, a vital cell marker. Three
different zones of damage were identified: (1) a zone of complete cell clearance, surrounded by (2) a ring of dead cells
marked with Trypan Blue and (3) the rest of the cell culture where the cells remain alive and viable. Different
hydrodynamic mechanisms damage cells as it was shown by high speed video for γ=0 and comparison with time
resolved imaging. The cell damage mechanism has its origin on the optical breakdown plasma formation. For the case
with culturing medium, a combination of plasma formation and shear stresses are responsible for cell damage; wheras
for the case without cell culturing medium, the plasma formation is the only mechanism of interaction between laser
pulses and cells. The rapidly expanding plasma generates shock waves whose pressure is most likely responsible for the
cell detachment observed.
Our work presents a study of the physical phenomena produced in biological-tissue irradiated by pulsed lasers. It is of
special interest to us to apply short (Nd:YAG, 5ns) and ultrashort (Ti:Sapphire, 90fs) laser pulses into biological-tissue
samples in order to study and understand the interaction features. These laser pulses posses interaction features with
tissue that could offer, depending on the pulse parameters, good advantages for medical applications; such features
include free heat laser pulse-tissue interaction and excellent mechanical damage confinement. This study was carried out
in porcine corneal tissue and biological-tissue models made by agar gel layers combined with organic dye, which
allowed us to emulate vascular tissue. The main objective of our study is to understand photo-induced thermal effects
and bubble formation in biological-tissue irradiated by short and ultrashort laser pulses. Our results on corneal tissue
showed a good potential for novel ophthalmic applications, especially in refractive surgery. In the case of the agar gel
biological-tissue models, similar results can be applied in dermatology in order to remove port wine stain or other similar
birthmarks.
Bubble formation is a well identified phenomenon within short (ns) and ultrashort (fs) laser pulses-aqueous media interactions. Bubble formation might be produced by three different mechanisms: (1) optical breakdown, (2) rarefraction wave and (3) overheating of the material. Experiments where transparent and scattering tissue models
that mimic biological tissue were irradiated with a Q-switched, 532 nm, 5 nanosecond, Nd:YAG and Ti:sapphire femtosecond laser systems. The type of bubble (transient or permanent) and initial bubble diameter were characterized as a function of time as well as the number of pulses and repetition rate at which they were delivered.
Threshold fluence for bubble formation in scattering tissue model was also studied. Two types of bubbles were identified depending on the number of pulses and the repetition rate at which they were delivered: transient (type 1) and permanent (type 2) bubbles. There is an insignificant difference in the fluence required to form a bubble in transparent tissue models regardless of the depth at which the beam was focused; in contrast, for scattering tissue models, the fluence required to form a bubble in deep positions is significantly higher than that of more superficial beam focus positions.
In this work we present experimental findings in the field of laser matter interaction on the topic of laser induced oxidation and crystalline structure change. It has been shown in the past few years that lasers can be used to induce both oxidization of metals as well changes the crystal in the crystalline structure of the metal oxide. Conventional theory has proven to be mildly successful in predicting these effects with a thermal model; drawing its influence from the traditional method of inducing material change by baking the metal. We reformed a scan of varying values of laser intensity and accumulated fluence. We will show evidence of an increase in the oxygen content in Ti and W thin films irradiated by a frequency doubled Nd:YAG laser source with a pulse duration of 4 ns and per pulse energies of 26 to 60 μJ (peak intensities of 1.7 x 107 to 3.8 x 107W/cm2). We will also show that other effects, that may include crystalline structure change, are also occurring.
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