| 1. |
- Asif, Muhammad
(författare)
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Zinc Oxide Nanostructure Based Electrochemical Sensors and Drug Delivery to Intracellular Environments
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The nanoscale science and nanostructure engineering have well established in the fabrication of novel electrochemical biosensors with faster response and higher sensitivity than of planar sensor configurations. Moreover nanostructures are suggested and used as efficient carrier of photosensitizers for cancerous cell treatment. The semi-conductor zinc oxide (ZnO) nanostructures have attracted much interest because of its unique piezoelectric, polar semiconducting, large surface area, catalytic properties, and being biosafe and biocompatible combined with the easiness of growth. This implies that ZnO nanostructures have a wide range of applications in optoelectronics, sensors, transducers, energy conversion and medical sciences. The aim of this study is to highlight recent developments in materials and techniques for electrochemical biosensing, photodynamic therapy, design, operation, and fabrication. The sensors in this study were used to detect and monitor real changes of metal ions and glucose across human fat cells and frog cells using changes in the electrochemical potential at the interface to the intracellular microenvironments. This thesis relates specifically to “zinc oxide nanostructure based electrochemical sensors and drug delivery to intracellular environments” for biological, biochemical and chemical applications. The first part of the thesis presents extra and intracellular studies on metal ions such as Ca2+, Mg2+, and Na+…..etc selectively sensed by using ZnO nanorods grown on the tip of a borosilicate glass capillary (0.7 μm in diameter) with the aim to produce proto-type electrochemical extra/intracellular biosensors. The single human adipocyte and frog oocyte cells were used to selectively measure the intracellular free metal ions concentration. To make the sensors selective for metal ions with sufficient selectivity and stability, plastic membrane coatings containing specific ionophores were applied. These functionalized ZnO nanorods sensors showed high sensitivity and good stability with linear electrochemical potential versus a wide metal ion concentration range of interest. The measured intracellular values were consistent with values reported in the literature. Furthermore we have successfully determined that the intracellular potassium (K+) concentration decrease is not obligatory for apoptosis. The aim of this study is to show the possibility of using K+ selective microelectrode to detect and monitor intracellular changes of K+ concentration during injection of various test solution and chemically induced apoptosis in Xenopus laevis oocytes parallel with electrophysiological measurements to verify the accuracy. The second part, presents the calcium ion (Ca2+) detection using functionalized ZnO nanorods attached as an extended gate metal oxide semiconductor field effect transistor (MOSFET). The electrochemical response was coupled directly to the gate of a commercial MOSFET to study the I-V characterization. Here we verified that ZnO nanorods grown on any thin wire can be combined with conventional electronic component to produce a sensitive and selective biosensor. In the third part, we have performed the experiment to determine glucose concentration intracellularly and in airway surface liquid (ASL) with functionalized ZnO nanorod-coated microelectrodes. In this study, the GOD enzyme was immobilised electrostatically, drawing on the fact that there is a large difference in the isoelectric points of ZnO and glucose oxidase. Insulin has been found to affect the glucose uptake in human adipocytes and frog Xenopus laevis. The large size of these cells makes it possible to microinject specific reagents that interrupt or activate signal transmission to glucose. The measured glucose concentration in human adipocytes or frog oocytes and ASL using our ZnO nanorod sensor was consistent with values of glucose concentration reported in the literature by using other indirect techniques. The fourth and final part covers the application of ZnO nanorods to cancer cells for photodynamic therapy. The ZnO nanorods were conjugated with protoporphyrin for local mediated photochemistry and efficient treatment of a single cancer cell. The ZnO nanorods were used as an efficient photosensitizer carrier system and at the same time providing intrinsic white light to achieve necrosis of the cancer cell. Breast cancer cells were used to study the catalytic effect of ZnO for treatment. The grown ZnO nanorods were conjugated with protoporphyrin dimethyl ester (PPDME), which absorbs the light emitted by the ZnO nanorods and cause the cytotoxicity which appears to involve the generation of reactive singlet oxygen inside the cell.
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| 2. |
- Bhand, Sunil, et al.
(författare)
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Coupled biosensor, biomimetic and chemometrics strategies for analysis of the metals in complex environmental matrices
- 2003
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Ingår i: Journal de Physique IV - Proceedings. - : EDP Sciences. - 1764-7177 .- 1155-4339. ; 107, s. 169-172
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Konferensbidrag (refereegranskat)abstract
- An analytical strategy to determine metals in environmental samples contaminated with both organophosphate pesticides and metals is presented. In the first step, parathion and arsenate were determined separately. Inhibition of the enzyme butyrylcholinesterase was quantified employing an enzyme thermistor and also with a CCD camera. Subsequently, parathion mixed with arsenate was measured. A molecularly imprinted polymer catalyst was then introduced as a pre-column to degrade OPs. The catalytic MIP enabled the measurement of metal from the mixture containing OPs. Hydrolysis of parathion, ethyl paraoxon, O-Ethyl-O-(4-nitrophenyl)-phenylphosphonothioate EPN and dichlorvos were monitored by using catalytic MIPs in the enzyme thermistor. Finally, inhibition patterns of parathion and arsenate were obtained employing multivariate analysis. The patterns generated after eliminating the OPs can be used for monitoring and mapping of metals in various environmental matrices.
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| 3. |
- Bhand, Sunil, et al.
(författare)
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Fructose-selective calorimetric biosensor in flow injection analysis.
- 2010
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 668:1, s. 13-18
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Tidskriftsartikel (refereegranskat)abstract
- A highly selective, interference free biosensor for the measurement of fructose in real syrup samples was developed. The assay is based on the phosphorylation of D(-)fructose to fructose-6-phosphate by hexokinase and subsequent conversion of fructose-6-phosphate to fructose-1,6-biphosphate by fructose-6-phosphate-kinase. The heat liberated in the second reaction is monitored using an enzyme thermistor. The major advantages of this biosensor are rapid and selective measurement of fructose without the need to eliminate glucose and inexpensive FIA-based, mediator-free calorimetric measurement suitable for regular fructose analysis. This method was optimised for parameters, such as pH, ionic strength, interference, operational stability and shelf life. Good and reproducible linearity (0.5-6.0 mM) with a detection limit of 0.12 mM was obtained. Fructose determination in commercial syrup samples and spiked samples confirmed the reliability of this set-up and technique. The biosensor gave reproducible results with good overall stability for continuous measurements over a period of three months besides a useful shelf life of six months. The method could be used for routine fructose monitoring in food samples.
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| 4. |
- Bhand, Sunil, et al.
(författare)
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Immuno-arrays for multianalyte analysis of chlorotriazines
- 2005
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Ingår i: Talanta. - : Elsevier BV. - 1873-3573 .- 0039-9140. ; 65:2, s. 331-336
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel strategy for multicomponent analysis of two classes of pesticides such as triazines (atrazine and simazine) and phenoxyalkanoic acids (2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), 4-chlorophenoxyacetic acid (CPOAc), phenoxyacetic acid (POAc)) employing immuno-arrays is demonstrated. The approach is based on cross-reactive arrays of specific antibody pairs coupled to chemometric pattern recognition. The monoclonal antibody pairs employed in this work (atrazine–simazine and 2,4-D) are specific towards a set of analytes and preclude a particular set of others present in the sample matrix. Antibody pairs of atrazine, simazine, and 2,4-D are used to discriminate and quantify analyte of interest. Atrazine was quantified in presence of trace concentration of simazine and that of 2,4-D. The combinatorial cross-reactivity of antibody pairs towards simazine, atrazine and 2,4-D is used to distinguish among different classes of analytes and their influence on the signal suppression in immuno-techniques. These sensors exclude recognition by carbamates such as carbaryl and carbofuran.
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| 5. |
- Pal, Souvik, et al.
(författare)
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A miniaturized nanobiosensor for choline analysis
- 2014
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 54, s. 558-564
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Tidskriftsartikel (refereegranskat)abstract
- A novel reusable chemiluminescence choline nanobiosensor has been developed using aligned zinc oxide nanorod-films (ZnONR). The chemically fashioned ZnONR were synthesized by hybrid wet chemical route onto glass substrates and used to fabricate a stable chemiluminescent choline biosensor. The biosensor was constructed by co-immobilization of the enzymes choline oxidase and peroxidase. The covalent immobilization of the enzymes on the ZnONR was achieved using 16-phosphonohexadecanoic acid as a cross-linker. The phosphonation of the ZnONR imparted significant stability to the immobilized enzyme as against physisorbed enzyme. A lower value of Michaelis-Menten constant (K-m), of 0.062 mM for the covalently coupled enzyme over the physisorbed enzymes facilitated enhanced stability of ZnONR nanobiosensor. The ZnONR-choline biosensor has been investigated over a wide range of choline from 0.0005 mM to 2 mM. Importantly, the recovery of choline in milk samples was close to 99%. Using the developed biosensor, choline was measurable even after 30 days with 60 repeated measurements proving the stability of the sensor (Intraday RSD%=2.83 and Interday RSD%=3.51).
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| 6. |
- Risveden, Klas, et al.
(författare)
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Branched nanotrees with immobilized acetylcholine esterase for nanobiosensor applications.
- 2010
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:5
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Tidskriftsartikel (refereegranskat)abstract
- A novel lab-on-a-chip nanotree enzyme reactor is demonstrated for the detection of acetylcholine. The reactors are intended for use in the RISFET (regional ion sensitive field effect transistor) nanosensor, and are constructed from gold-tipped branched nanorod structures grown on SiN(x)-covered wafers. Two different reactors are shown: one with simple, one-dimensional nanorods and one with branched nanorod structures (nanotrees). Significantly higher enzymatic activity is found for the nanotree reactors than for the nanorod reactors, most likely due to the increased gold surface area and thereby higher enzyme binding capacity. A theoretical calculation is included to show how the enzyme kinetics and hence the sensitivity can be influenced and increased by the control of electrical fields in relation to the active sites of enzymes in an electronic biosensor. The possible effects of electrical fields employed in the RISFET on the function of acetylcholine esterase is investigated using quantum chemical methods, which show that the small electric field strengths used are unlikely to affect enzyme kinetics. Acetylcholine esterase activity is determined using choline oxidase and peroxidase by measuring the amount of choline formed using the chemiluminescent luminol reaction.
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| 7. |
- Risveden, Klas, et al.
(författare)
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Signal frequency studies of an environmental application of a 65 nm region ion sensitive field effect transistor sensor
- 2007
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 127:1, s. 198-203
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Tidskriftsartikel (refereegranskat)abstract
- A rapid and sensitive novel type of bioelectronic Region Ion Sensitive Field Effect Transistor (RISFET) nanosensor was constructed on a chip with a 65 nm sensing electrode gap. The RISFET nanosensor was demonstrated for the environmental pesticide analysis of neurotoxic organocarbamate/carbofuran. The linear range for carbofuran analysis is ac signal frequency dependent, studied in the range (500 down-0.5 Hz, 50 mV(peak-peak) ac) and a bias voltage applied between the bottom capacitor plate and the electrodes. The signal current response is measured using a low-noise pico ammeter. The inhibition of acetylcholinesterase (AChE) by carbofuran was detectable in a logarithmic linear range (0.1-100nM) at 1.08 Hz, with a lower limit of detection of inhibition 0.1 nM with 10 min incubation time. The sensor is based on the principle of focusing charged reaction products with an electrical field in a region between the sensing electrodes. The current measurement by the sensor electrodes is correlated to the composition of the sample. The carbofuran detection is based on the ability to inhibit the enzyme AChE. The RISFET sensor chip is fabricated using conventional electron beam lithography. The encompassed sensor volume in the "nanocell" is in the attoliter range.
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| 8. |
- Singh, Aruna Chandra, et al.
(författare)
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Nanoimmunosensor based on ZnO nanorods for ultrasensitive detection of 17 beta-Estradiol
- 2019
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Ingår i: Biosensors & bioelectronics. - : ELSEVIER ADVANCED TECHNOLOGY. - 0956-5663 .- 1873-4235. ; 126, s. 15-22
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Tidskriftsartikel (refereegranskat)abstract
- Advances in nanostructured materials have facilitated the development of novel sensitive techniques for detection of environmental and clinical analytes. There is immense need for development of devices that can detect analytes at concentrations as low as few pg mL(-1). The comparable size of nanostructured materials and biomolecules enabled the integration of biological systems with nanometer sized structures. Herein, we demonstrate a Zinc Oxide nanorods (ZnONRs) integrated ultrasensitive label-free biosensor with femtomolar (0.01 pg mL(-1)) sensitivity for the endocrine disruptor 17 beta-Estradiol (E2). The ZnONRs, average width 50 nm and length 325 nm, were grown on the silver electrode surface (Ag-ZnONRs). Monoclonal antibodies of E2 (mAb-E2) were covalently immobilized on ZnONRs surface and measured using electrochemical impedance spectroscopy (EIS). A linear detection range of 0.1-200 pg mL(-1) for E2 with R-2 = 0.99 and % RSD = 4.35 (n = 3, assay volume 90 mu L) was achieved for the developed nano-sensing system. A significant enhancement in the sensitivity was achieved in the presence of ZnONRs, enabling the limit of quantification down to 0.1 pg(-1) with 2.7 % capacitance change per decade. In addition, a further increase in sensitivity due to assay volume reduction (20 mu L) was observed enabling further scope of miniaturization.
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| 9. |
- Singh, Manish, et al.
(författare)
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Supercritical carbon dioxide impregnation of gold nanoparticles demonstrates a new route for the fabrication of hybrid silk materials
- 2022
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Ingår i: Insects. - : MDPI AG. - 2075-4450. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- How many nanoparticles can we load in a fiber? How much will leak? Underlying is the relatively new question of the “space available” in fibers for nanoparticle loading. Here, using supercritical carbon dioxide (scCO2 ) as a carrier fluid, we explored the impregnation in four Indian silks (Mulberry, Eri, Muga, and Tasar) with five standard sizes of gold nanoparticles (5, 20, 50, 100 and 150 nm in diameter). All silks could be permanently impregnated with nanoparticles up to 150 nm in size under scCO2 impregnation. Accompanying structural changes indicated that the amorphous silk domains reorganized to accommodate the gold NPs. The mechanism was studied in detail in degummed Mulberry silk fibers (i.e., without the sericin coating) with the 5 nm nanoparticle. The combined effects of concentration, time of impregnation, scCO2 pressure, and temperature showed that only a narrow set of conditions allowed for permanent impregnation without deterioration of the properties of the silk fibers.
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| 10. |
- Yakovleva, Maria, et al.
(författare)
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The enzyme thermistor-A realistic biosensor concept. A critical review.
- 2013
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 1873-4324 .- 0003-2670. ; 766, s. 1-12
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Forskningsöversikt (refereegranskat)abstract
- This review describes principles and features of thermal biosensors and microbiosensors in flow injection analysis. Examples are given that illustrate the great versatility and excellent operational stability offered by thermal biosensors. The examples are mostly from work with the original type of enzyme thermistor operating with an enzyme column, but there will also be work described involving miniaturised devices including thermal lab-on-chip constructions and other types of sensing materials, such as MIPs (molecularly imprinted polymers) for both affinity and catalytic reactions. Several recently presented thermal biosensor concepts are reviewed including a thermal-electrochemical hybrid sensor for lactose based on immobilised cellobiose dehydrogenase. Another recent method is the determination of fructose using a fructose-6-phosphate kinase column. Operation with complex sample matrices such as blood, plasma and milk and how to avoid non-specific temperature effects are considered.
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