The need for new electronic devices and applications is driving the use of transition metal dichalcogenides (TMDCs) as suitable materials to integrate the next generation of novel applications. Thickness control of semiconductors is the great importance to attain specific electrochemical properties. In this work we investigate the thickness fluctuation of 2D MoSe2 structures synthesized by pulsed laser ablation in liquids (PLAL) by changing the choice of liquid phase. For the characterization we used atomic absorption spectrometer, high resolution electron microscopy, Raman spectroscopy and photoluminescence spectroscopy. Thinner MoSe2 nanosheets resulted from PLAL synthesis in reline compared with those produced in water.
Biocompatible colloidal nanomaterials are of great interest in the biomedical field due to their ability to modulate redox reactions that translates into antioxidant aides. Common wet syntheses processes utilized to obtain chalcogens nanoparticles have limitations such as low yield, high cost and use environmentally unfriendly chemical precursors and solvents. Pulsed laser ablation in liquids (PLAL) has shown to be an affordable, clean and rapid technique to produce chalcogen nanoparticles. Among the chalcogens, selenium (Se) has well-known capabilities of regulating the glutathione to reduced glutathione (GSH/GSSG) ratio, an established marker of ROS antioxidant activity in eukaryotic cells. Recently there has been an interest to include heavier chalcogens, e.g., tellurium (Te), in biological enzymatic interactions; however, due to its relative cytotoxicity, use of Te nanoparticles as an alternative to reduce glutathione, has not been fully investigated. In this work, we introduce the synthesis and characterization of a selenium-tellurium (SeTe) nano-alloy by PLAL using a deep eutectic solvent (DES), water and acetone as the liquid phase to exploit DES’s biocompatible composition and its influence on the PLAL synthesis kinetics that result in production of polycrystalline, sub-100nm nanoparticles. To investigate the formation of nano-alloy, we compare the features and properties of colloidal nanoparticles produced by PLAL at three wavelengths, 1064, 532 and 355 nm, respectively. We test bioactivity of SeTe nano-alloys, using A-375 (malignant melanoma) and C-33A (epithelial retinoblastoma) cells through assessing viability and proliferation to determine their capabilities towards use as anticancer treatments.
In recent years, bioessential element-based chalcogenides, namely Selenium (Se) and Tellurium (Te), have established noted fundamentals as metal-based protective agents. In relation to anti-cancer therapeutics, Se in particular exhibits promising characteristics as potentially effective treatment alternatives due to its notoriety as a highly selective, drug-coordinating element. In addition to their competitive clinical resume, Se nanoparticles packaged as chalcogenides are believed to support anti-inflammatory, antimicrobial and antifungal efforts. Though more is needed to understand the biological effect these materials play within the body, studies postulate that there is significant potential for Se based nanoalloys. Partnering Se with elemental neighbor Te, SexTel-x, these alloys function as target mediators. They are believed to sustain cell viability ARPE-19 cells while initiating apoptotic effects on MDA-MB-453 cancer cells, along with promoting the reduction of reactive oxygen species (ROS) activity. Lastly, cellular integrity is maintained by the lack of DNA fragmentation within normal cells, further supporting the efforts of employing SexTel-x alloys as potential anti-cancer agents. Ultimately, this research will serve as fundamental currency marketing SexTel-x nanoalloys as synergistically compliant anti-inflammatory, anti-cancer therapeutic agents, priming the tone for treatment efficacy.
Lanthanide doped upconversion nanoparticles (UCNPs) are promising luminescent materials for biomedical applications due to their ability to convert low energy, non-scattering NIR light to higher energy wavelength emissions. Sensing, bioimaging, drug delivery, therapy and photobiomodulation are the expected biomedical fields that will be impacted by the combination of NIR stimulation and upconversion emission. In the case of a typical upconversion from NIR, energy transfer occurs from Yb3+ sensitizer ions, which can be excited at 980 nm, to the activator lanthanide ions such as Er3+, Tm3+, Ho3+, Eu3+. Synthesis and design of the UCNPs and their introduction into the biological system requires stringent procedures due to the complex nature of biological environment at the cellular level. Our goal in this study is to develop small size, biocompatible UCNPs with a facile microwave assisted synthesis method and utilize them for photobiomodulation of neuronal cells. We aim to elucidate the intracellular mechanisms that are impacted by the upconversion photons emitted from designed nanotransducers towards stimulation of cell function. For this purpose, we sensitized blue emitting NaYF4 UCNPs and in-vitro laser irradiation experiments are conducted with NG108-15 (neuroblastoma-glioma hybrid) cells. Experiments are designed to further investigate the thermal and chemical effects that contribute to the resulted modifications in the cell function.
Inorganic fluorescent nanoprobes have been widely used as passive agents for intracellular imaging for decades. An emerging field of research is the development of these contrast agents and using them actively in a way that they respond to external stimulation by inducing photo-chemical, thermal or mechanical actions that enable control and modulation over cell function. To achieve such control, methods which are remote, non-invasive and with low-thermal means of stimulation is preferable. Among a large variety of candidates, lanthanide doped upconverting nanoparticles (UCNPs) are one of the most interesting class of fluorescent materials. Non-scattering, low energy near infrared (NIR) light can be used for excitation of UCNPs as on-demand light sources resulting in emission peaks throughout the near-UV and visible wavelengths. Towards this goal, we developed nano-size, hydrophilic, non-toxic and biocompatible core-shell nanoparticles with enhanced upconversion intensity for photo-biomodulation studies. Under this approach, un-doped LaF3 (inert) shell and Yb3+ doped LaF3 (active) shell are grown on core LaF3:20% Yb, 2% Tm upconverting nanoparticles for enhanced luminescence for the first time with rapid microwave-assisted synthesis method that employs Polyvinylpyrrolidone (PVP) as biocompatible surfactant. The as-synthesized high efficiency UCNPs are analyzed through XRD, TEM, HRTEM, and Photoluminescence spectrum that is acquired under 980 nm laser excitation. Confocal microscopy is used to visualize nanoparticles in cells. The cellular response to NIR irradiation and upconverted light are visualized by luminescence microscopy.
We report an experimental study, where Cobalt Ferrite (CoFe2O4) nanoparticles exhibit Photoacoustic (PA) emission peak intensity of 235.2V/J when analyzed under the Opto-Acoustic measurement setup. PA emission peak intensity decreases to 210V/J when AC Magnetic field is applied and further when Barium Titanate coated cobalt ferrite nanoparticles were analyzed, the PA peak further reduces to 68.76667V/J and with application of AC magnetic field the peak completely disappears. The measurement depicts the Photoacoustic and magnetoelastic behavior of cobalt ferrite nanoparticles.
As an increasing number of studies use gold nanoparticles (AuNPs) for potential medicinal, biosensing and therapeutic applications, the synthesis and use of readily functional, bio-compatible nanoparticles is receiving much interest. For these efforts, the particles are often taken up by the cells to allow for optimum sensing or therapeutic measures. This process typically requires incubation of the particles with the cells for an extended period. In an attempt to shorten and control this incubation, we investigated whether nanosecond pulsed electric field (nsPEF) exposure of cells will cause a controlled uptake of the particles. NsPEF are known to induce the formation of nanopores in the plasma membrane, so we hypothesized that by controlling the number, amplitude or duration of the nsPEF exposure, we could control the size of the nanopores, and thus control the particle uptake. Chinese hamster ovary (CHO-K1) cells were incubated sub-10 nm AuNPs with and without exposure to 600-ns electrical pulses. Contrary to our hypothesis, the nsPEF exposure was found to actually decrease the particle uptake in the exposed cells. This result suggests that the nsPEF exposure may be affecting the endocytotic pathway and processes due to membrane disruption.
Optoacoustic microscopy (OAM) is an emerging technology combining the beneficial features of optical contrast and ultrasound resolution, to form a hybrid imaging technique capable of multi-scale, high-contrast and high-resolution imaging through optically scattering biological tissues. In the past 15 years, two system modifications have been developed for optoacoustic / photoacoustic microscopy: acoustic-resolution AR-OAM and optical-resolution OR-OAM. Typically, acoustic resolution systems can image deeper tissues structures, however, with resolution at least an order of magnitude worse than the systems of optical-resolution. It would be attractive for variety of biomedical applications to attain high (submicron) resolution at a depth exceeding the present limit of the optical resolution optoacoustic microscopy. Here we introduce a novel, all-optical method for OAM, in which not only thermal energy deposition, but also optoacoustic signal detection is achieved optically. In our design the probe laser beam was used as an ultrawide-band ultrasonic transducer. In this method the acoustic pressure wave amplitude is proportional to the angle of deflection of the probing CW laser beam incident on a balanced dual photodiode. Such laser beam deflection (LBD) method overcomes the limitations of conventional piezoelectric ultrasound transducers and optical interferometers. LBD method allows one to use high numerical aperture objectives for better focusing, avoid distortions associated with the system elements that separate optical and acoustic paths, and provides better sensitivity than any optical interferometer. It also provides a non-contact method that is insensitive to optical and acoustic artifacts typical of backward mode of optoacoustic imaging. The LBD sensitivity depends on a large number of system parameters such as probe beam power, spot size, interaction length, optical refraction index of the coupling medium, laser wavelength, photodiode sensitivity, proximity to the optoacoustic source, and thus, can be optimized. The basic setup of OR-LBD-OAM shows high sensitivity competitive with commercial ultrasonic transducers. We report first images of biological cells and tissues obtained using this technique.
The exposure of nanosecond pulsed electric fields (nsPEF) to living cells has been shown to create nanopores in the
plasma membranes. These nanopores allow the passage of small ions but exclude the transport of larger molecules
such as Propidium ions, with permeabilization persisting for many minutes. To characterize these nanopores and the
effect of temperature of the formation and resealing of these pores, we have chosen to use 6-Propionyl-2-(N,NDimethylamo)
Naphthalene (PRODAN) as an indicator of membrane organization. PRODAN is a fluorescent dye
with a large excited-state dipole moment that displays extensive solvent polarity-dependent fluorescent shifts. By
monitoring this shift in fluorescence spectrum, disruption of the membrane after an electric exposure is observed as
an immediate increase in the membrane fluidity, likely indicating poration of the membrane. High-speed imaging
results indicate that a change in membrane organization occurs instantly (<5 ms), with longer pulse widths having a
more dramatic effect on the membrane. This instantaneous membrane disruption was shown to recover within 500
ms.
Several studies, over recent years, focus on the use of chitosan, a biocompatible macromolecule, to form gold
nanoparticles (GNPs). In this study, gold nanoparticles were synthesized using chitosan and Chloroauric acid, under
stirring which cause micro/nano-gels to form. Ultraviolet (UV) light is used to reduce solution into gold nanoparticles,
in which the resulting nanoparticles are biocompatible after this reduction. In effort to obtain nanoparticles of different
shape and size using the chitosan, different concentrations of monovalent salt, were added to the chitosan solution. The
different signatures of the particles based on the concentration of the salt in the solution are observed using an optoacoustic
setup to detect morphological changes in the particles due to shifts in the absorption resonance. The optoacoustic
measurements are compared to the absorption spectra of the gold nanoparticles. The overall goal of this study
is to investigate the influence of chitosan, with the addition of the monovalent salt, on the formation
of the biocompatible gold nanoparticles. This characterization will aid in the preparation of measurements to take on
these particles in other portions of the electromagnetic spectrum such as radio frequencies.
Oxidative stress (OS) is increasingly implicated as an underlying pathogenic mechanism in a wide range of diseases, resulting from an imbalance between the production of reactive oxygen species (ROS) and the system's ability to detoxify the reactive intermediates or repair the resulting damage. ROS can be difficult to detect directly; however, they can be detected indirectly from the effects on oxidative stress biomarkers (OSB), such as glutathione (GSH), 3-nitrotyrosine, homocysteine, and cysteine. Moreover the reaction of transition metals with thiol-containing amino acids (for example GSH) oxidized by ROS can yield reactive products that accumulate with time and contribute to aging and diseases. The study of the interaction between OSB using functionalized nanoparticles (fNPs) has attracted interest because of potential applications in bio-sensors and biomedical diagnostics. A goal of the present work is to use fNPs to detect and ultimately quantitate OS in retinal pigment epithelial (RPE) cells subjected to external stressors, e.g. nonionizing (light) and ionizing (gamma) radiation. Specifically, we are investigating the assembly of gold fNPs mediated by the oxidation of GSH in irradiated RPE cells. The dynamic interparticle interactions had been characterized in previously reported work by monitoring the evolution of the surface plasmon resonance band using spectroscopic analysis (UV-VIS absorption). Here we are comparing the dynamic evolution of fNP assembly using photoacoustic spectroscopy (PAS). We expect that PAS will provide a more sensitive measure allowing these fNP sensors to measure OS in cell-based models without the artifacts limiting the use of current methods, such as fluorescent indicators.
With recently developed diode-lasers to resonantly pump solid-state crystalline lasers, new opportunities arise for
systems such as Tb3+ as an activator ion in different host matrices. For example the observed fluorescence from 5D4→
7F5 transition (540 to 560 nm) of Tb3+ in TbAlO3 represents such a possibility. There is little fluorescence quenching in
this crystal involving this transition, and the measured lifetime is approximately 2 ms, long enough to sustain sufficient
population for stimulated emission. The quantum efficiency is better than 50 % as measured in this material. For this
same transition, others have reported room-temperature pulsed laser operation at 544 nm for Tb:YLF, where the lifetime
is comparable. Mid- and long wavelength infrared laser emission has been observed for Tb3+ in chalcogenide glass fibers
that complement our spectroscopic findings for Tb3+ in pedestal-grown Y2O3 and YAG fibers. We have identified the
infrared transitions that may lase at transitions between different manifolds within the 7FJ multiplet. In the present study
we first evaluate the various visible and infrared experimental findings with a Judd-Ofelt analysis of Tb3+ in TbAlO3. We
predict a radiative lifetime of 3.5 ms for the excited 5D4 manifold to the 7FJ manifolds with more than 50% of the
emission represented by the 5D4→ 7F5 transition. To account for the visible stimulated emission, we report transition
probabilities for 5D4→ 7FJ transitions and for diode-pumped infrared transitions we report similar spectroscopic
properties for transitions within the 7FJ multiplet.
Highly luminescent nanoparticles, such as, trivalent erbium-doped yttrium-oxide, Er3+:Y2O3, are expected to have a wide
range of applications, including imaging, range finding, flash lidar, and other remote-sensing possibilities as well as
medical applications. These particles are synthesized by the precipitation from a homogeneous solution of the metal ions
and urea at elevated temperatures. The morphology of the calcinated materials, revealed through SEM, shows uniformly
spherical aggregates 200 nm or less depending on the ratio of the metal ions in the initial solution. Room temperature
optical absorption and emission spectra show that the trivalent erbium ions in Er3+:Y2O3 nanocrystals possess sharp
absorption lines and strong emission in near infrared region that are characteristic of Er 3+:Y2O3 grown as large single
crystals. Low temperature (8 K) spectra obtained from these particles were analyzed in detail for the crystal-field
splitting of the 2S+1LJ multiplet manifolds of Er3+(4f11) including the ground-state manifold 4I15/2, and excited manifolds
4I9/2, 4F9/2, 4S3/2, 2H11/2, 4F7/2, 4F5/2, and 4F3/2. Fluorescence lifetimes and results from an analysis of the intensities of
manifold-to-manifold transitions are also reported. Similarity of the nanocrystalline and large single crystal Er3+:Y2O3,
we propose that the simple, inexpensive method described in this study will lead to further investigation of these
nanocrystals for their optical properties, especially in the near infrared region of the spectrum.
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