| 1. |
- Abdelhamid, Hani Nasser, et al.
(author)
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A water-stable lanthanide metal-organic framework for fluorimetric detection of ferric ions and tryptophan
- 2017
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In: Microchimica Acta. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 184:9, s. 3363-3371
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Journal article (peer-reviewed)abstract
- The preparation of a highly water stable and porous lanthanide metal-organic framework (MOF) nanoparticles (denoted SUMOF-7II; SU refers to Stockholm University) is described. SUMOF-7II was synthesized starting from the tritopic linker of 2,4,6-tri-p-carboxyphenyl pyridine (H3L2) and La(III) as metal clusters. SUMOF-7II forms a stable dispersion and displays high fluorescence emission with small variation over the pH range of 6 to 12. Its fluorescence is selectively quenched by Fe(III) ions compared to other metal ions. The intensity of the fluorescene emission drops drops linearly in 16.6–167 μM Fe(III) concentration range, and Stern-Volmer plots are linear. The limit of detection (LOD) is 16.6 μM (at an S/N ratio of >3). This indicator probe can also be used for selective detection of tryptophan among several amino acids. Compared to the free linker H3L2, SUMOF-7II offers improved sensitivity and selectivity of the investigated species.
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| 2. |
- Adeel, Muhammad, et al.
(author)
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2D metal azolate framework as nanozyme for amperometric detection of glucose at physiological pH and alkaline medium
- 2021
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In: Microchimica Acta. - : Springer. - 0026-3672 .- 1436-5073. ; 188:3
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Journal article (peer-reviewed)abstract
- The synthesis of Co-based two-dimensional (2D) metal azolate framework nanosheets (MAF-5-CoII NS) is described using a simple hydrothermal method. The product was isostructural to MAF-5 (Zn). The as-prepared MAF-5-CoII NS exhibited high surface area (1155 m2/g), purity, and crystallinity. The MAF-5-CoII NS–modified screen-printed electrode (MAF-5-CoII NS/SPE) was used for nonenzymatic detection of glucose in diluted human blood plasma (BP) samples with phosphate buffer saline (PBS, pH 7.4) and NaOH (0.1 M, pH 13.0) solutions. The MAF-5-CoII NS nanozyme displayed good redox activity in both neutral and alkaline media with the formation of CoII/CoIII redox pair, which induced the catalytic oxidation of glucose. Under the optimized detection potential, the sensor presented a chronoamperometric current response for the oxidation of glucose with two wide concentration ranges in PBS-diluted (62.80 to 180 μM and 305 to 8055 μM) and NaOH-diluted (58.90 to 117.6 μM and 180 to 10,055 μM) BP samples, which were within the limit of blood glucose levels of diabetic patients before (4.4–7.2 mM) and after (10 mM) meals (recommended by the American Diabetes Association). The sensor has a limit of detection of ca. 0.25 and 0.05 μM, respectively, and maximum sensitivity of ca. 36.55 and 1361.65 mA/cm2/mM, respectively, in PBS- and NaOH-diluted BP samples. The sensor also displayed excellent stability in the neutral and alkaline media due to the existence of hydrophobic linkers (2-ethyl imidazole) in the MAF-5-CoII NS, good repeatability and reproducibility, and interference-free signals. Thus, MAF-5-CoII NS is a promising nanozyme for the development of the disposable type of sensor for glucose detection in human body fluids.
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| 3. |
- Alpeeva, IS, et al.
(author)
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Bi-enzyme alcohol biosensors based on genetically engineered alcohol oxidase and different peroxidases
- 2005
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In: Microchimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 152:1-2, s. 21-27
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Journal article (peer-reviewed)abstract
- We report on the development of a bi-layer bi-enzyme biosensor architecture using different peroxidases and alcohol oxidase from Hansenula polymorpha C-105 as biological recognition elements. The sensor architecture comprises a first layer containing either horseradish peroxidase or royal palm tree peroxidase crosslinked with an Osmium complex-modified redox hydrogel. On top, a second layer was formed by electrochemically induced precipitation of a cathodic electrodeposition paint simultaneously entrapping alcohol oxidase isolated from a genetically modified strain of Hansenula polymorpha C-105. The sensor architecture was optimized with respect to effective electron transfer and stability of the enzyme. The main characteristics of the biosensors are an apparent maximal current I-max(app) of 572-940 nA, an apparent Michaelis constant K-M(app) of 9.5 mM, a sensitivity of 60-98 nA mM(-1) and an improved operational stability represented by a deactivation constant of 1.5-2.0 x 10(-4) min(-1).
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| 4. |
- Augustsson, Per, et al.
(author)
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Buffer medium exchange in continuous cell and particle streams using ultrasonic standing wave focusing
- 2009
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In: Microchimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 164:3-4, s. 269-277
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Journal article (peer-reviewed)abstract
- A microfluidic strategy to perform buffer exchange of particle and cell suspensions in a continuous flow format on, chip is presented. Ultrasonic standing wave technology is utilized to confine particulate matter to the centre of a buffer exchange channel while particle free buffer is sequentially aspirated via capillaries that branch off from the buffer exchange channel. At each such branch, clean buffer is supplied at an equal flow-rate from a capillary at the opposing channel wall, generating a sideways translation of the original buffer, laminated with a wash buffer stream. Each such junction increases the buffer exchange ratio accordingly. The reported buffer exchange system provides means to adjust buffer exchange conditions on-line by tuning the ratio of the cross-flow wash buffer relative the sample suspension flow, rate. The system performance was evaluated using 5 mu m polystyrene microbeads and a dye as the model contaminant. Wash efficiencies up to 96.4% were accomplished with a 0.2% solid content bead suspension, using eight cross-flow junctions, effectively exchanging the carrier buffer twice. The corresponding data for erythrocyte washing was recorded to be 98.3% at a haematocrit of 2%.
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| 5. |
- Bradley, Siobhan J., et al.
(author)
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Heterogeneity in the fluorescence of graphene and graphene oxide quantum dots
- 2017
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In: Microchimica Acta. - : Springer Science and Business Media LLC. - 0026-3672 .- 1436-5073. ; 184:3, s. 871-878
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Journal article (peer-reviewed)abstract
- Heterogeneity is an inherent property of a wealth of real-world nanomaterials and yet rarely in the reporting of new properties is its effect sufficiently addressed. Graphene quantum dots (GQDs) – fluorescent, nanoscale fragments of graphene - are an extreme example of a heterogeneous nanomaterial. Here, top-down approaches – by far the most predominant – produce batches of particles with a distribution of sizes, shapes, extent of oxidation, chemical impurities and more. This makes characterization of these materials using bulk techniques particularly complex and comparisons of properties across different synthetic methods uninformative. In particular, it hinders the understanding of the structural origin of their fluorescence properties. We present a simple synthetic method, which produces graphene quantum dots with very low oxygen content that can be suspended in organic solvents, suggesting a very pristine material. We use this material to illustrate the limitations of interpreting complex data sets generated by heterogeneous materials and we highlight how misleading this “pristine” interpretation is by comparison with graphene oxide quantum dots synthesized using an established protocol. In addition, we report on the solvatochromic properties of these particles, discuss common characterization techniques and their limitations in attributing properties to heterogeneous materials.
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| 6. |
- Cagnini, A, et al.
(author)
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Ruthenized screen-printed choline oxidase-based biosensors for measurement of anticholinesterase activity
- 1995
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In: Microchimica Acta. - : Springer Science Business Media. - 0026-3672 .- 1436-5073. ; 121:04-jan, s. 155-166
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Journal article (peer-reviewed)abstract
- Plastic disposable choline biosensors based on ruthenized-carbon screen-printed electrodes were prepared and their use for monitoring organophosphorus pesticides and carbamates is described. The presence of 0.5% ruthenium on activated carbon mixed to form a simple graphite-based ink for the working electrode surface increased the sensitivity towards hydrogen peroxide. The choline biosensor is based on such an electrode coupled with choline oxidase immobilized by adsorption and was used to detect the inhibition effect of carbamates and organophosphorus pesticides on acetylcholinesterase. With the optimized procedure described (pH, buffer composition, incubation time, substrate concentration), concentrations of pesticides (Carbofuran) as low as 1 nM could be detected.
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| 7. |
- Carugati, Gabriele, 1980, et al.
(author)
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Experimental assessment of a large sample cell for laser ablation-ICP-MS, and its application to sediment core micro-analysis
- 2010
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In: Mikrochimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 170:1-2, s. 39-45
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Journal article (peer-reviewed)abstract
- The coupling of laser ablation (LA) to inductively coupled plasma-mass spectrometry (ICP-MS) enables the direct analysis of solid samples with micrometric resolution. Analysis is often restricted to relatively small samples owing to the dimensions of conventional ablation cells. Here, we assess the performance of a large rectangular, commercially-available sample cell which enables analysis over a 10.2 x 5.2 cm(2) area. Comparison with the conventional cell shows a small to moderate performance decrease for the large cell resulting from the dilution of ablated particles in a larger volume with a 4-31% lower signal output and longer signal tailings. The performance of this cell is however sufficient for the determination of both major and trace elements in many kinds of samples. The applicability of the large cell LA-ICP-MS setup was demonstrated by the determination of Al, Si, Mn, Fe, Cu, Zn Pb and U in sediment core sections at a resolution of 0.6 mm. Detection limits for sediment analysis were 7 mg Al kg(-1), 68 mg Si kg(-1), 0.5 mg Mn kg(-1), 20 mg Fe kg(-1), 0.2 mg Cu kg(-1), 0.3 mg Zn kg(-1), 0.08 mg Pb kg(-1) and 0.003 mg U kg(-1). Cyclic patterns, which would have been overlooked by conventional analysis at cm resolution, were observed in analysed sediments. This study demonstrates the potential of LA-ICP-MS in environmental analysis, with the large sample cell setup offering the possibility to analyse a wider range of samples without sectioning.
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| 8. |
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| 9. |
- Cui, Yang, et al.
(author)
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Magnetic solid-phase extraction of trace-level mercury(II) ions using magnetic core-shell nanoparticles modified with thiourea-derived chelating agents
- 2015
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In: Microchimica Acta. - : Springer Verlag (Germany). - 0026-3672 .- 1436-5073. ; 182:7-8, s. 1337-1344
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Journal article (peer-reviewed)abstract
- We describe a method for magnetic solid phase extraction of trace-levels of Hg(II) ions by using Fe3O4 nanoparticles (NPs) covered with a shell of silica and modified with the chelator N-(2-acetylaminoethyl)-N-(3-triethoxysilylpropyl)thiourea. The new magnetic NPs enable rapid magnetic separation, thus leading to higher efficiency and accuracy. The extracted Hg(II) ions on the NPs were directly quantified using a mercury analyzer. Possible interferents are widely eliminated in this highly selective extraction process, and the NPs are not exerting an interfering effect either. The method has an enrichment factor of 100, and extraction recoveries are between 95 and 107 % when using 10 mg of the extracting NPs. The method works over a wide range of pH values and can be applied to even complex natural samples. The effects of pH value, extraction time, sample volume and adsorbent amount on the extraction efficiency were optimized. Under the optimal conditions, the detection limit is as low as 17 ng L-1. The method was applied to the preconcentration and detection of Hg(II) in three natural water samples using the standard addition method.
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| 10. |
- Dong, B., et al.
(author)
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Local surface plasmon resonance of single silver nanorice particles in the near-infrared
- 2014
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In: Mikrochimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 181:7-8, s. 791-795
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Journal article (peer-reviewed)abstract
- We report on the synthesis and optical spectra of silver nanorice particles. Two strong absorption bands are resolved in the near UV and near-IR region, and the dark field scattering spectra are consistent with the absorption spectra. Finite-difference time-domain simulations reveal that the peak in the IR region can be attributed to the E field that is parallel to the long axis, while the peak in the UV can be attributed to the E field perpendicular to the short axis of the silver nanorice particles.
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