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- Cornelis, Geert, et al.
(author)
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Challenges and current approaches toward environmental monitoring of nanomaterials
- 2021
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In: Monitoring Environmental Contaminants : A volume in Environmental Contaminants. - 9780444643360 ; , s. 73-108
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Book chapter (peer-reviewed)abstract
- Engineered nanomaterials (ENMs), i.e., man-made particles having at least one dimension smaller than 100nm, have found their way into the environment. Parallel to the efforts to elucidate the possible harmful effects of ENMs, techniques have been developed to monitor environmental ENM concentrations. This chapter discusses the techniques that can currently distinguish ENMs from naturally occurring particles at realistic concentration detection limits without a tedious sample pretreatment procedure. For inorganic ENMs, the most promising approach is based on single particle ICP-MS, and this technique has been developed in recent years to measure solid samples in addition to aquatic samples and distinguish the many different forms of occurrence of ENMs in realistic samples from naturally occurring particles. The detection capabilities for C-based particles are lagging and will likely be the focus of analytical developments in the coming years.
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| 3. |
- Farkas, Julia, et al.
(author)
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Characterization of the effluent from a nanosilver producing washing machine
- 2011
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In: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 37:6, s. 1057-1062
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Journal article (peer-reviewed)abstract
- The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11 mu g L(-1), as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10 nm measured with transmission electron microscopy (TEM) and 60-100 nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment.
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| 5. |
- Gallego-Urrea, Julian A., 1977, et al.
(author)
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Measurements of nanoparticle number concentrations and size distributions in contrasting aquatic environments using nanoparticle tracking analysis
- 2010
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In: Environmental Chemistry. - 1449-8979. ; 7, s. 67-81
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Journal article (peer-reviewed)abstract
- A feasibility study of nanoparticle tracking analysis (NTA) for aquatic environmental samples is presented here. The method has certain virtues such as minimum perturbation of the samples, high sensitivity in terms of particle concentration, and provision of number-based size distributions for aquatic samples. NTA gave linear calibration curves in terms of number concentration and accurately reproduced size measurements of certified reference material nanoparticles. However, the accuracy of the size distributions obtained with this method exhibited a high dependence on set-up parameters and the concentrations were shown to be strongly correlated with the refractive index of the material under examination. Different detection cameras and different data acquisition modeswere compared and evaluated. Also, the effect of filtration of the samples was assessed. The size distributions for the contrasting environmental samples were fairly reasonable compared with other studies but an underestimation of small sizes was observed, which can be explained by a materialdependent lower detection limit in terms of size. The number concentrations obtained for the natural nanoparticles ranged from 0.5 to 20×108 particles mL−1 and correlated well with conventional turbidity measurements.
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| 7. |
- Ma, Su, et al.
(author)
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Direct Electron-Transfer Anisotropy of a Site-Specifically Immobilized Cellobiose Dehydrogenase
- 2019
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In: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; , s. 7607-7615
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Journal article (peer-reviewed)abstract
- To study the direct electron transfer (DET) of the multicofactor enzyme cellobiose dehydrogenase (CDH) in regard to its orientation on an electrode surface, a recently published, maleimide-based immobilization method was used in combination with site-directed mutagenesis to establish different orientations on an electrode surface. CDH from Myriococcum thermophilum was chosen for this study because its protein structure is resolved and the factors influencing the movement of its mobile cytochrome domain (CYT) are established. Seven CDH variants with a surface-exposed cysteine residue in different spatial positions were generated for site-specific maleimide coupling. Surface plasmon resonance and cyclic voltammetry showed that all CDH variants, but not the wild-type CDH, bound covalently to gold electrodes or glassy carbon electrodes and were catalytically active. For DET, the CYT domain needs to move from the closed-state conformation, where it obtains an electron from the catalytic flavin adenine dinucleotide (FAD) cofactor to the open state where it can donate an electron to the electrode. We therefore hypothesized that the mobility of the CYT domain and its distance to the electrode is central for DET. We found that the uniform spatial orientations of CDH influenced DET as follows: an orientation of the two-domain enzyme on the side, with CYT in proximity to the electrode, resulted in high DET currents. Orientations with a bigger distance between CYT and the electrode, or orientations where CYT could not swing back to the dehydrogenase domain to form the closed enzyme conformation, reduced DET. In the latter case, calcium ions that stabilize the closed conformation of CDH fully recovered DET. The study demonstrates that a mobile CYT domain can compensate unfavorable orientations of the catalytic domain to a great extent and allows CDH as a multicofactor enzyme to transfer electrons even in awkward orientations. The mobile CYT domain reduces the anisotropy of DET, which is also essential for CDH's physiological function as an extracellular, electron-transferring enzyme.
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| 8. |
- Minelli, Caterina, et al.
(author)
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Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles
- 2022
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 14, s. 4690-4704
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Journal article (peer-reviewed)abstract
- We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles.
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| 9. |
- Moreira, Beatriz, et al.
(author)
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Surface Plasmon Resonance for Measuring Exocytosis from Populations of PC12 Cells: Mechanisms of Signal Formation and Assessment of Analytical Capabilities
- 2017
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 89:5, s. 3069-3077
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Journal article (peer-reviewed)abstract
- Because of cell to cell variation, it is difficult to obtain statistically significant data on the frequency of exocytosis events (R-exocytosis, t(-1) m(-2)) with traditional single cell electrophysiological or fluorescence microscopy based methods. Here we take the first steps toward a rapid cost-effective surface plasmon resonance (SPR) based method for measuring the R-exocytosis for populations of PC12 cells. The conditions for culturing confluent monolayers on the sensor slides were optimized, and neurotransmitter exocytosis was evoked by injecting solutions with elevated Exocytosis caused a shift of the resonance angle (Delta theta(r)) that was linearly proportional to R-exocytosis The Delta theta(r) was mainly due to elevated concentration of secretory vesicles close to the cell membrane. The increased vesicle concentration thus acted as a proxy for the Rexocytosis that could not be measured directly. The Delta theta(r) was calibrated for it R-exocytosis using single cell amperometry on parallel cell cultures. The cell populations were large enough for variation in responses between sensor slides to only reflect actual differences in biological condition. The applicability for drug screening is demonstrated by studying the effects of EGTA, reserpine, and prolonged stimulation by K+
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| 10. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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A new peak recognition algorithm for detection of ultra-small nano-particles by single particle ICP-MS using rapid time resolved data acquisition on a sector-field mass spectrometer
- 2015
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In: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 30:8, s. 1723-1729
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Journal article (peer-reviewed)abstract
- The applicability of single particle inductively coupled plasma mass spectrometry (spICPMS) is currently limited to particles larger than similar to 10 nm in diameter. In this work, the size detection limit (DLs) was improved by resolving the ion bursts originating from silver or gold nanoparticles (AgNPs or AuNPs) using real time data acquisition with 0.1 ms time resolution. Such acquisition is here called the Fast Acquisition Speed Technique (FAST). The analytical capabilities of the FAST were evaluated on a sector field instrument with high ion transmission efficiency (ITE). An algorithm for distinguishing particle events from dissolved and/or background signals was developed, and it was possible to detect 6.4 nm AuNPs that delivered only 2 ions to the detector. The influence of dwell time was investigated and it was concluded that the minimum DLs is achieved for dwell times close to the duration of particle events similar to 0.2 ms. Attempts to further improve the DLs should therefore be focused on increasing the ITE of the mass spectrometer.
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