Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 31
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Talanta ; 274: 126061, 2024 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-38583329

RESUMO

This work aims to demonstrate the potential of pulsed laser ablation synthesis (PLA) of tellurium nanoparticles (Te NPs) for use in matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) applications. An experimental laboratory setup for PLA synthesis of fresh Te NPs was designed to prevent unwanted aggregation of uncoated Te NPs and avoid the need to use additional modifiers. Performing pulsed laser ablation synthesis in liquid (PLAL) using acetone was found to be the optimal way of preparing Te NPs. Another possibility is to use commercially available laser ablation devices for laser ablation - inductively coupled plasma mass spectrometry (LA-ICP-MS) to perform PLA in a helium atmosphere, but this approach is less efficient and results in the formation of unwanted larger particles. The prepared Te NPs were studied using the transmission electron microscopy (TEM) and dynamic light scattering (DLS) methods. TEM images showed the formation of Te NP nanochains composed of many crystallized Te NPs with sizes ranging from 8 to 15 nm. The various size distributions of the synthesized Te NPs identified using the DLS method correspond to the size distributions of aggregations rather than individual Te NPs. The synthesized Te NPs were used for a pilot study of their possible use with the MALDI-MS technique. An important effect was observed when Te NPs were used to perform a MALDI-MS analysis of the α-cyclodextrin (α-CD) and cucurbit[7]uril (CB7) macrocycles, which consisted in a decline in the formation of matrix adducts. Furthermore, several changes in MALDI-MS mass spectra of intact cells and a positive effect of Te NPs on the crystallization of the MALDI-MS matrix were observed.

2.
Nanomaterials (Basel) ; 14(6)2024 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-38535644

RESUMO

ZrN-Cu coatings containing two different amounts of Cu (~11 at.% and ~25 at.%) were deposited using an industrial physical vapor deposition (PVD) system. The as-deposited coatings exhibited 100% bactericidal efficiency against Escherichia coli CCM 3988 for an exposure time of 40 min. Subsequently, the samples were attached onto our faculty's door handles for six months to study the coatings' long-term effectiveness and durability under actual operational conditions. The samples were periodically evaluated and it was observed that the coatings with 25 at.% Cu performed better than the ones with 11 at.% Cu. For example, following 15 days of being touched, the bactericidal effectiveness of the sample containing 25 at.% Cu dropped to 65% while it fell to 42% for the sample containing 11 at.%. After 6 months, however, both samples showed bactericidal efficiency of ~16-20%. The bactericidal efficiency of the samples touched for 6 months was successfully restored by polishing them. Furthermore, a group of samples was kept untouched and was also evaluated. The untouched samples with Cu content of ~25 at.% did not show any drop in their bactericidal properties after 6 months. ZrN-Cu coatings were concluded to be promising materials for self-sanitizing application on high-touch surfaces.

3.
Anal Chim Acta ; 1299: 342418, 2024 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-38499415

RESUMO

BACKGROUND: Laser-induced breakdown spectroscopy (LIBS) is a well-recognized analytical technique used for elemental analysis. This method is gaining considerable attention also in biological applications thanks to its ability for spatial mapping and elemental imaging. The implementation of LIBS in the biomedical field is based on the detection of metals or other elements that either naturally occur in the samples or are present artificially. The artificial implementation of nanoparticle labels (Tag-LIBS) enables the use of LIBS as a readout technique for immunochemical assays. However, one of the biggest challenges for LIBS to meet immunoassay readout standards is its sensitivity. RESULTS: This paper focuses on the improvement of LIBS sensitivity for the readout of nanoparticle-based immunoassays. First, the LIBS setup was optimized on photon-upconversion nanoparticle (UCNP) droplets deposited on the microtiter plate wells. Two collection optics systems were compared, with single pulse (SP) and collinear double pulse (DP) LIBS arrangements. By deploying the second laser pulse, the sensitivity was improved up to 30 times. The optimized SP and DP setups were then employed for the indirect detection of human serum albumin based on immunoassay with UCNP-based labels. Compared to our previous LIBS study, the detection limit was enhanced by two orders of magnitude, from 10 ng mL-1 to 0.29 ng mL-1. In addition, two other immunochemical methods were used for reference, based on the readout of upconversion luminescence of UCNPs and absorbance measurement with enzyme labels. Finally, the selectivity of the assay was tested and the practical potential of Tag-LIBS was demonstrated by the successful analysis of urine samples. SIGNIFICANCE AND NOVELTY: In this work, we improved the sensitivity of the Tag-LIBS method by combining new labels based on UCNPs with the improved collection optics and collinear DP configuration. In the instrumental setup optimization, the DP LIBS showed better sensitivity and signal-to-noise ratio than SP. The optimizations allowed the LIBS readout to surpass the sensitivity of enzyme immunoassay, approaching the qualities of upconversion luminescence readout, which is nowadays a state-of-the-art readout technique.


Assuntos
Nanopartículas , Humanos , Análise Espectral/métodos , Nanopartículas/química , Imunoensaio/métodos , Lasers , Metais
4.
Rapid Commun Mass Spectrom ; 37(12): e9520, 2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37038657

RESUMO

RATIONALE: Carbides, including tellurium carbides (TeC), play crucial roles in diverse applications, but TeC synthesis has not been described in the literature. Laser ablation synthesis (LAS) coupled with mass spectrometry was used here for in situ TeC clusters synthesis and identification of the reaction products to better understand TeC formation. METHODS: Laser desorption ionization time-of-flight mass spectrometry (LDI-TOFMS) was used to generate the TeC clusters and determine their stoichiometry via computer modeling of isotopic patterns. RESULTS: A simple one-pot procedure was developed for Te-nanodiamond nanocomposite preparation. A suspension of fine-powdered Te was mixed with a suspension of nanodiamonds (both in acetonitrile), and the resulting precipitated nanocomposite was suitable for the synthesis of TemCn clusters using LDI. Various unary and binary clusters were formed. The stoichiometry of the novel TemCn clusters, determined via computer modeling of isotopic patterns, is reported here for the first time. CONCLUSIONS: The Te-nanodiamond composite was found to be the most suitable precursor for the generation of TemCn clusters. In total, 35 binary TemCn clusters were identified, when several of them were not obtained using commercial TeC material.

5.
Anal Chim Acta ; 1225: 340224, 2022 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-36038235

RESUMO

Acoustics recordings from laser-induced plasmas are becoming increasingly regarded as a complementary source of information from the inspected sample. The propagation of these waves is susceptible to be modified by the physicochemical traits of the sample, thus yielding specific details that can be used for sorting and identification of targets. Still, the relative fragility of the acoustic wave poses major challenges to the applicability of laser-induced acoustics. Echoes and reflections sourcing from intrasample parameters as well as from interactions of the acoustic wave with the surroundings of the inspected target can dilute the analytical information directly related to the object contained within the recordings. The present work aims to experimentally scrutinize the impact of different parameters internal and external to the sample into the final acoustic signal from laser-induced plasmas in order to accurately use this information source for characterization purposes. Variables inherent to the sample such as dimensions, porosity and absorption coefficient, which guides the laser-matter coupling process, have been, for the first time, systematically studied using ad-hoc solids to thoroughly isolate their influence on the signal. Moreover, modulation of soundwave induced by the surroundings of the probed target and the anisotropy of the acoustic signal because of the angle at which the plasma is formed, have been evaluated.


Assuntos
Acústica , Modelos Teóricos , Anisotropia , Lasers , Porosidade
6.
Ann Vasc Surg ; 85: 156-166, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35304297

RESUMO

BACKGROUND: Critical limb ischemia (CLI) is considered the most severe pattern of peripheral artery disease. CLI is associated with high rates of morbidity and mortality with high risk of limb amputation. In the absence of appropriate autologous grafts, unsuitability of prosthetic bypasses, and endovascular methods, fresh cold-stored venous allografts is an option. Endovascular interventional methods are essential methods for maintaining primary and secondary patency. METHODS: A single-centre retrospective analysis of 82 surgical revascularizations using allogeneic vascular grafts and rescue endovascular techniques restoring and maintaining the patency of these allogeneic revascularizations in the period between July 2005 and July 2021. RESULTS: We have performed 82 allogeneic revascularizations in 75 patients (52 reconstructions in men/63.4%/, 30 reconstructions in women/36.6%/). The median age of patients was 68 years (49 min, 87 max). We subsequently had to intervene a total of 26 bypasses. We intervened in 30 acute occluded allogeneic bypass grafts and 9 failing stenotic bypass grafts. We performed 52 angiographies. The success rate of rescue endovascular procedures in primary allogeneic reconstruction with distal anastomosis to the popliteal artery is statistically significant (P < 0.02) compared to procedures with distal anastomosis to the tibial and pedal bed. The cumulative patency (primary at time) of allogeneic reconstructions in our group was 89% after 1 month, 51.9% after 12 months, 24.2% after 3 years, 9.8% after 5 years. Limb salvage was 72.6% in 1 year, 53% in 3 years, 36.5% in 5 years, respectively. CONCLUSIONS: Cold-stored venous allografts may be used for performing below-the-knee revascularization for CLI with acceptable results, despite the poor long-term patency. Rescue endovascular techniques are an essential method for restoring or maintaining the patency of these reconstructions. These techniques have a high success rate and no other alternative.


Assuntos
Procedimentos Endovasculares , Doença Arterial Periférica , Idoso , Aloenxertos/cirurgia , Procedimentos Endovasculares/efeitos adversos , Feminino , Humanos , Isquemia/diagnóstico por imagem , Isquemia/cirurgia , Salvamento de Membro , Masculino , Doença Arterial Periférica/diagnóstico por imagem , Doença Arterial Periférica/cirurgia , Estudos Retrospectivos , Resultado do Tratamento , Grau de Desobstrução Vascular
7.
Mikrochim Acta ; 188(5): 147, 2021 04 02.
Artigo em Inglês | MEDLINE | ID: mdl-33797618

RESUMO

Immunohistochemistry (IHC) and immunocytochemistry (ICC) are widely used to identify cancerous cells within tissues and cell cultures. Even though the optical microscopy evaluation is considered the gold standard, the limited range of useful labels and narrow multiplexing capabilities create an imminent need for alternative readout techniques. Laser-induced breakdown spectroscopy (LIBS) enables large-scale multi-elemental analysis of the surface of biological samples, e.g., thin section or cell pellet. It is, therefore, a potential alternative for IHC and ICC readout of various labels or tags (Tag-LIBS approach). Here, we introduce Tag-LIBS as a method for the specific determination of HER2 biomarker. The cell pellets were labeled with streptavidin-conjugated upconversion nanoparticles (UCNP) through a primary anti-HER2 antibody and a biotinylated secondary antibody. The LIBS scanning enabled detecting the characteristic elemental signature of yttrium as a principal constituent of UCNP, thus indirectly providing a reliable way to differentiate between HER2-positive BT-474 cells and HER2-negative MDA-MB-231 cells. The comparison of results with upconversion optical microscopy and luminescence intensity scanning confirmed that LIBS is a promising alternative for the IHC and ICC readout.


Assuntos
Biomarcadores Tumorais/análise , Nanopartículas/química , Receptor ErbB-2/análise , Anticorpos Imobilizados/imunologia , Biomarcadores Tumorais/imunologia , Linhagem Celular Tumoral , Estudos de Viabilidade , Fluoretos/química , Fluoretos/efeitos da radiação , Humanos , Imuno-Histoquímica/métodos , Luz , Nanopartículas/efeitos da radiação , Receptor ErbB-2/imunologia , Análise Espectral/métodos , Túlio/química , Túlio/efeitos da radiação , Ítrio/química , Ítrio/efeitos da radiação
8.
Prague Med Rep ; 121(3): 142-152, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33030143

RESUMO

A retrospective analysis of our group of patients, efficacy, safety and the results of endovascular treatment of descending thoracic aorta by using stentgraft implantation in polytraumatized patients. In the period between 6/2006 and 2/2020, in the processing of data, we analysed retrospectively patients with polytrauma diagnosed with thoracic aortic rupture or transection (TAT) and treated with multiple injuries. Clinical characteristics, complications, pathological features, and hospital follow-up data were retrieved from our group. In our group of 28 polytraumatized patients referred to our Trauma Centre with current TAT, all 28 patients with such a thoracic aortic injury were treated by using thoracic stentgraft implantation. In our group of patients, the average Injury Severity Score (ISS) was 22 for women (min 19, max 27) and 26 for men (min 17, max 41), respectively. We reached 100% technical implantation success rate with our patients. In our group, we had 30-day mortality of 10.7% (3 patients) and the in-hospital mortality was 17.8% (5 patients). Surviving patients had calculated ISS score of 25 (min 17, max 41); dead patients had an ISS score of 28 (min 19, max 34) - p≤0.05. Endovascular treatment of TAT, as a minimally invasive and effective procedure with rapid bleeding control, may increase survival chances for severely compromised polytraumatized patients in the context of multiple-organ damage and the need for a major cardio-vascular surgery.


Assuntos
Aorta Torácica , Procedimentos Endovasculares , Ferimentos não Penetrantes , Aorta Torácica/diagnóstico por imagem , Aorta Torácica/lesões , Feminino , Humanos , Escala de Gravidade do Ferimento , Masculino , Estudos Retrospectivos , Resultado do Tratamento , Ferimentos não Penetrantes/diagnóstico , Ferimentos não Penetrantes/terapia
9.
Chemosphere ; 251: 126174, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32151804

RESUMO

In this study, a model crop plant white mustard (Sinapis alba L.) was treated with an aqueous dispersion of silica-coated CdTe quantum dots (CdTe/SiO2 QDs) in a 72-h short-term toxicity test. The toxicity was established via measurements of (i) the root length and (ii) the chlorophyll fluorescence. These results were compared to two other sources of cadmium, free Cd ions (CdCl2) and prime un-shell nanoparticles CdTe QDs. Tested compounds were applied in concentrations representing 20 and 200 µM Cd. The uptake and translocation of Cd were investigated using inductively coupled plasma optical emission spectrometry (ICP-OES) and the spatial Cd distribution was investigated in detail applying laser induced breakdown spectroscopy (LIBS). The LIBS maps with a lateral resolution of 100 µm were constructed for the whole plants, and maps with a lateral resolution of 25 µm (micro-LIBS arrangement) were used to analyse only the most interesting parts of plants with Cd presence (e.g. root tips or a part crossing the root into the above-ground part). Our results show that the bioaccumulation patterns and spatial distribution of Cd in CdTe/SiO2 QDs-treated plants differ from the plants of positive control and CdTe QDs. Fluorescence microscopy photographs revealed that CdTe/SiO2 became adsorbed onto the plant surface in comparison to CdTe QDs. Further, a physico-chemical characterization of QDs before and after the test exposure showed only minor changes in the nanoparticle diameters and no tendencies of QDs for agglomeration or aggregation during the exposure.


Assuntos
Compostos de Cádmio/química , Pontos Quânticos/química , Adsorção , Bioacumulação , Cádmio , Compostos de Cádmio/toxicidade , Microscopia de Fluorescência , Pontos Quânticos/toxicidade , Dióxido de Silício/química , Sinapis/metabolismo , Cloreto de Sódio , Telúrio/química
10.
Mikrochim Acta ; 186(9): 629, 2019 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-31418079

RESUMO

Laser-induced breakdown spectroscopy (LIBS) was examined as a novel method for readout of microtiter plate immunoassays involving nanoparticles (NP). The so-called Tag-LIBS technique is a sensitive method for the detection of specific biomarkers. It was applied to the determination of NP labels using nanosecond ablation sampling. The NP labels were examined from the bottom of a standard 96-well microtiter plate. Thanks to the flexibility of LIBS instrumentation, both the plasma emission collection and the focusing optics arrangements can be collinearly arranged. The experiments showed that silver NPs and gold NPs can be readily quantified on the bottom of the microtiter plate. Utilizing this technique, a sandwich immunoassay for human serum albumin using streptavidin-coated AgNP labels was developed. The assay has a 10 ng·mL-1 detection limit which is comparable to the sensitivity of fluorometric readout. The main advantage of this LIBS technique is its wide scope in which it enables a detection of almost any type of NP labels, irrespective to any fluorescence or catalytic properties. Owing to the immediate signal response, the relatively simple instrumentation also enables assay automation. The LIBS capability of multi-elemental analyses makes it a promising and fast alternative to other readout techniques, in particular with respect to multiplexed detection of biomarkers. Graphical abstract Laser-induced breakdown spectroscopy (LIBS) is used as a novel readout method of nanoparticle-based immunoassays in microtiter plates. After formation of sandwich immunocomplex, the analyte concentration is quantified as the signal of Ag nanoparticle labels determined by LIBS.


Assuntos
Imunoensaio/métodos , Lasers , Nanopartículas Metálicas/química , Albumina Sérica Humana/análise , Biomarcadores/sangue , Ouro/química , Humanos , Tamanho da Partícula , Prata/química , Propriedades de Superfície
11.
Vasa ; 48(5): 399-404, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31063085

RESUMO

Background: A histopathological examination was conducted on vein samples from six patients who had undergone great saphenous vein sealing with Histoacryl and Lipiodol to treat chronic venous insufficiency of the superficial venous system. Patients and methods: In each patient a sample of the complete vein including the surrounding tissue was obtained through a minor incision under perioperative sonographic monitoring. Each patient had signed an informed consent form. Samples were taken at the following intervals: six days, six weeks, six months, one year, two years, and three years after treatment. Results: N-butyl-2-cyanoacrylate with Lipiodol induces a thrombotic reaction in the acute phase and endothelium is destroyed but no significant inflammation or substantial vascular wall damage is present. In the subsequent period, a foreign body giant cell reaction emerges accompanied by only moderate chronic inflammation that does not extend to the vascular wall or the surrounding tissue. The thrombus is organized with minimal recanalization. The foreign material is gradually degraded, and it is no longer detectable after three years. The vessel wall showed slight sclerotization. Conclusions: N-butyl-2-cyanoacrylate that has been applied gradually degrades over the course of three years accompanied by a giant cell reaction, mild chronic inflammation and cicatrices, but there is minimal recanalization of the obturated section.


Assuntos
Veia Safena , Varizes , Insuficiência Venosa , Embucrilato , Humanos , Resultado do Tratamento
12.
Chemosphere ; 225: 723-734, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30903846

RESUMO

In this study, radish (Raphanus sativus L.) and common duckweed (Lemna minor L.) were treated with an aqueous dispersion of carboxylated silica-coated photon-upconversion nanoparticles containing rare-earth elements (Y, Yb, and Er). The total concentration of rare earths and their bioaccumulation factors were determined in root, hypocotyl, and leaves of R. sativus after 72 h, and in L. minor fronds after 168 h. In R. sativus, translocation factors were determined as the ratio of rare earths concentration in hypocotyl versus root and in leaves versus hypocotyl. The lengths of the root and hypocotyl in R. sativus, as well as the frond area in L. minor, were monitored as toxicity endpoints. To distinguish rare earth bioaccumulation patterns, two-dimensional maps of elemental distribution in the whole R. sativus plant and L. minor fronds were obtained by laser-induced breakdown spectroscopy with a lateral resolution of 100 µm. Moreover, the bioaccumulation was inspected using a photon-upconversion laser microscanner. The results revealed that the tested nanoparticles became adsorbed onto L. minor fronds and R. sativus roots, as well as transferred from roots through the hypocotyl and into leaves of R. sativus. The bioaccumulation patterns and spatial distribution of rare earths in nanoparticle-treated plants therefore differed from those of the positive control. Overall, carboxylated silica-coated photon-upconversion nanoparticles are stable, can easily translocate from roots to leaves, and are expected to become adsorbed onto the plant surface. They are also significantly toxic to the tested plants at nominal concentrations of 100 and 1000 µg/mL.


Assuntos
Nanopartículas/química , Extratos Vegetais/química , Raphanus/efeitos dos fármacos , Análise Espectral/métodos , Fótons
13.
Anal Chem ; 90(20): 11820-11826, 2018 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-30126278

RESUMO

Nanoparticles (NPs) applied to the surface of some solids can increase signals in inductively coupled plasma mass spectrometry (ICPMS). Drops containing 20 and/or 40 nm nanoparticles of Ag and/or Au were deposited on metallic and ceramic/glass samples, and after being dried, both the samples treated with NPs and plain targets were ablated by one pulse per spot. The laser ablation ICPMS (LA-ICPMS) signals were enhanced for metallic samples modified with NPs in comparison to signals produced at the plain, untreated surface. Maps of LA-ICPMS signals recorded for several laser fluences show that the NP-induced signal enhancement exceeds even 2 orders of magnitude for metallic samples. No enhancement was achieved for nonconductive samples. This enhancement is limited to the peripheral annular region of the dried droplet area where NPs are concentrated due to the "coffee stain" effect. Ablation crater profilometric inspection revealed a more uniform material rearrangement over the NP-treated surface compared with the ablated plain target. However, besides a smoother crater bottom, no other evidence of an NP-enhancing effect was noticed, although an increased ablation rate was anticipated. Limits of detection dropped by 1 order of magnitude for the minor elements in the presence of NPs. Observed phenomena depend only on the NP surface concentration but not on the material or size of the NPs. An electron microprobe study of the collected ablation aerosol has shown that aerosol particles consisting of target material are aggregated around the NPs. The hypothesis is that such aggregates exhibit better transport/vaporization efficiency, thus enhancing signals for metallic samples. A detailed study of the suggested mechanism will be continued in ongoing work.

14.
Vasa ; 47(5): 416-424, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29890917

RESUMO

BACKGROUND: Treating great and small saphenous vein trunk insufficiency with cyanoacrylate glue is the least taxing treatment method of all available techniques. Due to long-term unavailability of commercial kits with n-butyl-2-cyanoacrylate (histoacryl) in the Czech Republic, we used a modified technique. PATIENTS AND METHODS: Fifty-six limbs in 49 patients suffering from great saphenous vein or small saphenous vein insufficiency in combination with symptomatic chronic venous insufficiency and complicating comorbidities were treated with a modified endovascular cyanoacrylate glue application technique. RESULTS: The immediate success rate of the treatment was 98 %. In follow-up intervals of six weeks, six months, one year, and two years, the anatomical success rates of embolization (recanalization of no more than 5 cm of the junction) were 98, 96, 94, and 94 %, respectively. At identical intervals the venous insufficiency was scored according to the Aberdeen Varicose Vein Questionnaire and the American Venous Clinical Severity Score. In both cases, improvement was demonstrated over the two-year follow-up, with a 0.5 % significance level. Specific clinical signs of venous insufficiency were also evaluated, such as pain, oedema, clearance of varicose veins, and healing of venous ulceration. One severe complication - a pulmonary embolism - was reported, without consequences. CONCLUSIONS: We demonstrated that treating insufficient saphenous veins with modified histoacryl application brought a relief from symptoms of venous insufficiency and that the efficiency of this technique is comparable to commonly used methods.


Assuntos
Embolização Terapêutica , Embucrilato/administração & dosagem , Procedimentos Endovasculares , Veia Safena , Varizes/terapia , Insuficiência Venosa/terapia , Adulto , Idoso , Idoso de 80 Anos ou mais , Doença Crônica , República Tcheca , Embolização Terapêutica/efeitos adversos , Embucrilato/efeitos adversos , Procedimentos Endovasculares/efeitos adversos , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Fatores de Risco , Veia Safena/diagnóstico por imagem , Veia Safena/cirurgia , Índice de Gravidade de Doença , Fatores de Tempo , Resultado do Tratamento , Varizes/diagnóstico por imagem , Varizes/cirurgia , Insuficiência Venosa/diagnóstico por imagem , Insuficiência Venosa/cirurgia
15.
Nanomaterials (Basel) ; 8(6)2018 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-29914152

RESUMO

The purpose of this study is to investigate the time dependent growth of silica shells on CdTe quantum dots to get their optimum thicknesses for practical applications. The core/shell structured silica-coated CdTe quantum dots (CdTe/SiO2 QDs) were synthesized by the Ströber process, which used CdTe QDs co-stabilized by mercaptopropionic acid. The coating procedure used silane primer (3-mercaptopropyltrimethoxysilane) in order to make the quantum dots (QDs) surface vitreophilic. The total size of QDs was dependent on both the time of silica shell growth in the presence of sodium silicate, and on the presence of ethanol during this growth. The size of particles was monitored during the first 72 h using two principally different methods: Dynamic Light Scattering (DLS), and Scanning Electron Microscopy (SEM). The data obtained by both methods were compared and reasons for differences discussed. Without ethanol precipitation, the silica shell thickness grew slowly and increased the nanoparticle total size from approximately 23 nm up to almost 30 nm (DLS data), and up to almost 60 nm (SEM data) in three days. During the same time period but in the presence of ethanol, the size of CdTe/SiO2 QDs increased more significantly: up to 115 nm (DLS data) and up to 83 nm (SEM data). The variances occurring between silica shell thicknesses caused by different methods of silica growth, as well as by different evaluation methods, were discussed.

16.
Ecotoxicol Environ Saf ; 153: 23-31, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29407734

RESUMO

We report on the toxicity and bioaccumulation of three different types of Cd-based quantum dots (QDs), dispersed in aqueous medium, for a model plant Allium cepa L. It is believed that encapsulation of nanoparticles should reduce their toxicity and increase their stability in different environments; in this work we studied how QD encapsulation affects their phytotoxicity. Core, core/shell, and core/shell/shell QDs (CdTe, CdTe/ZnS, and CdTe/CdS/ZnS QDs capped by 2-mercaptopropionic acid) were tested and CdCl2 was used as a positive control. After 24-h and 72-h exposure, total Cd content (MCd) and bioaccumulation factors (BAFs) were determined in all parts of A. cepa plants (roots, bulb, shoot), and the total length of the root system was monitored as a toxicity end-point. Measurements of total Cd content versus free Cd2+ content (with Differential Pulse Voltammetry, DPV) in exposure media showed differences in chemical stability of the three QD types. Correspondingly, selected QDs showed different toxicity for A. cepa and different Cd bioaccumulation patterns. CdTe QDs were the most toxic; their effect was similar to CdCl2 due to the release of free Cd2+, which was confirmed by the DPV measurements. Plants exposed to CdTe QDs also bioaccumulated the most Cd among all QD exposure groups. CdTe/ZnS QDs showed no toxicity and very low bioaccumulation of Cd in A. cepa; the main source of measured Cd in the plants were QDs adsorbed on their roots, which was confirmed by fluorescence microscopy. On the contrary, CdTe/CdS/ZnS QD toxicity and bioaccumulation patterns were similar to those of CdTe QDs and pointed to unstable CdS/ZnS shells.


Assuntos
Compostos de Cádmio/análise , Compostos de Cádmio/toxicidade , Cebolas/efeitos dos fármacos , Pontos Quânticos/análise , Pontos Quânticos/toxicidade , Adsorção , Microscopia de Fluorescência , Cebolas/química , Raízes de Plantas/química , Raízes de Plantas/efeitos dos fármacos
17.
Ecotoxicol Environ Saf ; 147: 334-341, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28858706

RESUMO

The purpose of this study was to determine the toxicity of two different sources of cadmium, i.e. CdCl2 and Cd-based Quantum Dots (QDs), for freshwater model plant Lemna minor L. Cadmium telluride QDs were capped with two coating ligands: glutathione (GSH) or 3-mercaptopropionic acid (MPA). Growth rate inhibition and final biomass inhibition of L. minor after 168-h exposure were monitored as toxicity endpoints. Dose-response curves for Cd toxicity and EC50168h values were statistically evaluated for all sources of Cd to uncover possible differences among the toxicities of tested compounds. Total Cd content and its bioaccumulation factors (BAFs) in L. minor after the exposure period were also determined to distinguish Cd bioaccumulation patterns with respect to different test compounds. Laser-Induced Breakdown Spectroscopy (LIBS) with lateral resolution of 200µm was employed in order to obtain two-dimensional maps of Cd spatial distribution in L. minor fronds. Our results show that GSH- and MPA-capped Cd-based QDs have similar toxicity for L. minor, but are significantly less toxic than CdCl2. However, both sources of Cd lead to similar patterns of Cd bioaccumulation and distribution in L. minor fronds. Our results are in line with previous reports that the main mediators of Cd toxicity and bioaccumulation in aquatic plants are Cd2+ ions dissolved from Cd-based QDs.


Assuntos
Araceae/efeitos dos fármacos , Cloreto de Cádmio/toxicidade , Compostos de Cádmio/toxicidade , Monitoramento Ambiental/métodos , Pontos Quânticos/toxicidade , Telúrio/toxicidade , Poluentes Químicos da Água/toxicidade , Ácido 3-Mercaptopropiônico/química , Adsorção , Araceae/crescimento & desenvolvimento , Araceae/metabolismo , Biomassa , Cloreto de Cádmio/metabolismo , Compostos de Cádmio/metabolismo , Água Doce/química , Glutationa/química , Modelos Teóricos , Pontos Quânticos/metabolismo , Telúrio/metabolismo , Poluentes Químicos da Água/química
18.
Sci Rep ; 7(1): 3160, 2017 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-28600563

RESUMO

In this work, we proposed a new data acquisition approach that significantly improves the repetition rates of Laser-Induced Breakdown Spectroscopy (LIBS) experiments, where high-end echelle spectrometers and intensified detectors are commonly used. The moderate repetition rates of recent LIBS systems are caused by the utilization of intensified detectors and their slow full frame (i.e. echellogram) readout speeds with consequent necessity for echellogram-to-1D spectrum conversion (intensity vs. wavelength). Therefore, we investigated a new methodology where only the most effective pixels of the echellogram were selected and directly used in the LIBS experiments. Such data processing resulted in significant variable down-selection (more than four orders of magnitude). Samples of 50 sedimentary ores samples (distributed in 13 ore types) were analyzed by LIBS system and then classified by linear and non-linear Multivariate Data Analysis algorithms. The utilization of selected pixels from an echellogram yielded increased classification accuracy compared to the utilization of common 1D spectra.

19.
Prague Med Rep ; 117(2-3): 117-123, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27668528

RESUMO

We report on a very rare case of diagnosis and successful surgical treatment of three young family members with a four-fold presentation of thoracic outlet syndrome. In the relevant family case, we are considering and discussing the population incidence, a possible HOX genes disorder, and a significant phenotypic presentation.


Assuntos
Fenótipo , Síndrome do Desfiladeiro Torácico/diagnóstico , Síndrome do Desfiladeiro Torácico/cirurgia , Adolescente , Adulto , Feminino , Humanos , Síndrome do Desfiladeiro Torácico/genética , Procedimentos Cirúrgicos Torácicos
20.
J Anat ; 229(3): 356-68, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-27173578

RESUMO

Chameleon teeth develop as individual structures at a distance from the developing jaw bone during the pre-hatching period and also partially during the post-hatching period. However, in the adult, all teeth are fused together and tightly attached to the jaw bone by mineralized attachment tissue to form one functional unit. Tooth to bone as well as tooth to tooth attachments are so firm that if injury to the oral cavity occurs, several neighbouring teeth and pieces of jaw can be broken off. We analysed age-related changes in chameleon acrodont dentition, where ankylosis represents a physiological condition, whereas in mammals, ankylosis only occurs in a pathological context. The changes in hard-tissue morphology and mineral composition leading to this fusion were analysed. For this purpose, the lower jaws of chameleons were investigated using X-ray micro-computed tomography, laser-induced breakdown spectroscopy and microprobe analysis. For a long time, the dental pulp cavity remained connected with neighbouring teeth and also to the underlying bone marrow cavity. Then, a progressive filling of the dental pulp cavity by a mineralized matrix occurred, and a complex network of non-mineralized channels remained. The size of these unmineralized channels progressively decreased until they completely disappeared, and the dental pulp cavity was filled by a mineralized matrix over time. Moreover, the distribution of calcium, phosphorus and magnesium showed distinct patterns in the different regions of the tooth-bone interface, with a significant progression of mineralization in dentin as well as in the supporting bone. In conclusion, tooth-bone fusion in chameleons results from an enhanced production of mineralized tissue during post-hatching development. Uncovering the developmental processes underlying these outcomes and performing comparative studies is necessary to better understand physiological ankylosis; for that purpose, the chameleon can serve as a useful model species.


Assuntos
Dentição , Arcada Osseodentária/anatomia & histologia , Calcificação de Dente/fisiologia , Dente/anatomia & histologia , Dente/fisiologia , Envelhecimento , Animais , Lagartos , Microtomografia por Raio-X
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...