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| 2. |
- Bejhed Stjernberg, Rebecca, et al.
(författare)
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Magnetic nanobeads present during enzymatic amplification and labeling for a simplified DNA detection protocol based on AC susceptometry
- 2015
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 5:12
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic biosensors are promising candidates for low-cost point-of-care biodiagnostic devices. For optimal efficiency it is crucial to minimize the time and complexity of the assay protocol including target recognition, amplification, labeling and read-out. In this work, possibilities for protocol simplifications for a DNA biodetection principle relying on hybridization of magnetic nanobeads to rolling circle amplification (RCA) products are investigated. The target DNA is recognized through a padlock ligation assay resulting in DNA circles serving as templates for the RCA process. It is found that beads can be present during amplification without noticeably interfering with the enzyme used for RCA (phi29 polymerase). As a result, the bead-coil hybridization can be performed immediately after amplification in a one-step manner at elevated temperature within a few minutes prior to read-out in an AC susceptometer setup, i.e. a combined protocol approach. Moreover, by recording the phase angle xi = arctan(chi ''/chi'), where chi and chi '' are the in-phase and out-of-phase components of the AC susceptibility, respectively, at one single frequency the total assay time for the optimized combined protocol would be no more than 1.5 hours, often a relevant time frame for diagnosis of cancer and infectious disease. Also, applying the phase angle method normalization of AC susceptibility data is not needed. These findings are useful for the development of point-of-care biodiagnostic devices relying on bead-coil binding and magnetic AC susceptometry.
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| 3. |
- Bejhed Stjernberg, Rebecca, et al.
(författare)
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Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:37, s. 10296-10302
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Tidskriftsartikel (refereegranskat)abstract
- A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.
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| 4. |
- Blacker, Christopher, et al.
(författare)
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Primary evaluation of an air-cooling device to reduce oral mucositis : a pilot study in healthy volunteers
- 2020
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Ingår i: Medical Oncology. - : Humana Press. - 1357-0560 .- 1559-131X. ; 37:12
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Tidskriftsartikel (refereegranskat)abstract
- Oral mucositis is a common side effect of chemo and radiotherapy causing painful ulcers in the oral mucosa. One of the preventive treatments recommended in international guidelines is oral cryotherapy (OC). Randomized clinical trials on OC have used ice and ice-chips to cool the mouth, but this cooling method can be difficult for the patients to tolerate. Studies have shown that OC with ice for a period of 60 min reduces the oral temperature by 12.9 degrees C. The aim of this pilot study was to evaluate the temperature reduction and tolerability of OC using an intra-oral air-cooling (IOAC) device in healthy volunteers. Twelve healthy volunteers, mean age 35.4 years, were included in the study. They were treated with OC using the IOAC device for 60 min. Measurements of temperature were obtained at baseline, 5 and 60 min using a FLIR (R) C2 camera. After the OC session, tolerability and adverse events were documented using a questionnaire. All participants were able to use the device for 60 min. The overall temperature reduction after 5 min of OC was 10.7 degrees C (p < 0.01) and after 60 min 14.5 degrees C (p < 0.01). The most common adverse events were bad fit of the mouthpiece (n = 6), hypersalivation (n = 6), and difficulties swallowing (n = 5). The oral device reduced the temperature of the oral mucosa as much as treatment with ice with tolerable adverse events. The mouthpiece will be remodeled to improve tolerability before further studies are conducted.
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| 5. |
- Donolato, Marco, et al.
(författare)
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Novel readout method for molecular diagnostic assays based on optical measurements of magnetic nanobead dynamics
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 87:3, s. 1622-1629
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate detection of DNA coils formed from a Vibrio cholerae DNA target at picomolar concentrations using a novel optomagnetic approach exploiting the dynamic behavior and optical anisotropy of magnetic nanobead (MNB) assemblies. We establish that the complex second harmonic optical transmission spectra of MNB suspensions measured upon application of a weak uniaxial AC magnetic field correlate well with the rotation dynamics of the individual MNBs. Adding a target analyte to the solution leads to the formation of permanent MNB clusters, namely, to the suppression of the dynamic MNB behavior. We prove that the optical transmission spectra are highly sensitive to the formation of permanent MNB clusters and, thereby to the target analyte concentration. As a specific clinically relevant diagnostic case, we detect DNA coils formed via padlock probe recognition and isothermal rolling circle amplification and benchmark against a commercial equipment. The results demonstrate the fast optomagnetic readout of rolling circle products from bacterial DNA utilizing the dynamic properties of MNBs in a miniaturized and low-cost platform requiring only a transparent window in the chip.
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| 6. |
- Persson, Anders, et al.
(författare)
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Modelling and design of planar Hall effect bridge sensors for low-frequency applications
- 2013
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 189, s. 459-465
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Tidskriftsartikel (refereegranskat)abstract
- The applicability of miniaturized magnetic field sensors is being explored in several areas of magneticfield detection due to their integratability, low mass, and potentially low cost. In this respect, differentthin-film technologies, especially those employing magnetoresistance, show great potential, being compatible with batch micro- and nanofabrication techniques. For low-frequency magnetic field detection,sensors based on the planar Hall effect, especially planar Hall effect bridge (PHEB) sensors, show promising performance given their inherent low-field linearity, limited hysteresis and moderate noise figure. Inthis work, the applicability of such PHEB sensors to different areas is investigated. An analytical modelis constructed to estimate the performance of an arbitrary PHEB sensor geometry in terms of, e.g., sensitivity and detectivity. The model is valid for an ideal case, e.g., disregarding shape anisotropy effects, andalso incorporates some approximations. To validate the results, modelled data was compared to measurements on actual PHEBs and was found to predict the measured values within 13% for the investigatedgeometries. Subsequently, the model was used to establish a design process for optimizing a PHEB to aparticular set of requirements on the bandwidth, detectivity, compliance voltage and amplified signalto-noise ratio. By applying this design process, the size, sensitivity, resistance, bias current and powerconsumption of the PHEB can be estimated. The model indicates that PHEBs can be applicable to severaldifferent areas within science including satellite attitude determination and magnetic bead detection inlab-on-a-chip applications, where detectivities down towards 1 nT Hz−0.5at 1 Hz are required, andmaybeeven magnetic field measurements in scientific space missions and archaeological surveying, where thedetectivity has to be less than 100 pT Hz−0.5at 1 Hz.
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| 7. |
- Sommertune, Jens, et al.
(författare)
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Polymer/iron oxide nanoparticle composites—A straight forward and scalable synthesis approach
- 2015
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 16:8, s. 19752-19768
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic nanoparticle systems can be divided into single-core nanoparticles (with only one magnetic core per particle) and magnetic multi-core nanoparticles (with several magnetic cores per particle). Here, we report multi-core nanoparticle synthesis based on a controlled precipitation process within a well-defined oil in water emulsion to trap the superparamagnetic iron oxide nanoparticles (SPION) in a range of polymer matrices of choice, such as poly(styrene), poly(lactid acid), poly(methyl methacrylate), and poly(caprolactone). Multi-core particles were obtained within the Z-average size range of 130 to 340 nm. With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles. The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.
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| 8. |
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| 9. |
- Stjernberg Bejhed, Rebecca, 1978-
(författare)
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Biomolecular Recognition Based on Field Induced Magnetic Bead Dynamics
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, three different read-out techniques for biomolecular recognition have been studied. All three techniques rely on the change in dynamic behaviour of probe functionalised magnetic beads after binding to a biomolecular target complementary to the probe.In the first technique presented, the sample is exposed to an AC magnetic field while the response to this field is probed using a laser source and a photodetector positioned at opposite sides of the sample. Beads bound to the target entity will experience an increase in their hydrodynamic volume, and will not be able to respond as rapidly to an alternating field as free beads. Here, the target entity is either DNA coils formed by rolling circle amplification or biotinylated bovine serum albumin (bBSA). The change in dynamic behaviour is measured as a frequency dependent modulation of transmitted light. Limit of detections (LODs) of 5 pM DNA coils originating from a V. cholerae target and 100 pM of bBSA have been achieved.In the second technique presented, the beads are magnetically transported across a probe functionalised detection area on a microchip. Beads bound to a target will be blocked from interaction with the detection area probes, whereas in the absence of a target, beads will be immobilised on the detection area. The LOD of biotin for this system proved to be in the range of 20 to 50 ng/ml.In the third technique presented, the sample is microfluidically transported to a detection area on a microchip. The read-out is performed using a planar Hall effect bridge sensor. A sinusoidal current is applied to the bridge in one direction and the sensor output voltage is measured across the sensor in the perpendicular direction. The AC current induced bead magnetisation contributing to the sensor output will appear different for free beads compared to beads bound to a target. LODs of 500 B. globigii spores and 2 pM of V. cholerae DNA coils were achieved.From a lab-on-a-chip point of view, all three techniques considered in this thesis show promising results with regards to sensitivity and integrability.
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| 10. |
- Stjernberg Bejhed, Rebecca, et al.
(författare)
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Optomagnetic bioassay for qualitative biplex detection of bacterial DNA sequences
- 2015
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Ingår i: Biotechnology Journal. - : Wiley. - 1860-6768 .- 1860-7314. ; 10:3, s. 469-472
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing need to develop novel bioassay methods for low-cost, rapid, and easy-to-use multiplex detection of pathogens in various fields ranging from human infectious disease diagnosis, drinking water quality control, to food safety applications. Due to their unique advantages, magnetic and optomagnetic bioassay principles are particularly promising for biodetection platforms that will be used in developing countries. In this paper, an optomagnetic method for rapid and cost-efficient qualitative biplex detection of bacterial DNA sequences is demonstrated. Within less than two hours, the assay gives an answer to whether none, both, or only one of the bacterial DNA sequences is present in the sample. The assay relies on hybridization of oligonucleotide-functionalized magnetic nanobeads of two different sizes to rolling circle amplification (RCA) products originating from two different bacterial targets. The different bead sizes are equipped with different oligonucleotide probes, complementary to only one of the RCA products, and the read-out is carried out in the same sample volume. In an optomagnetic setup, the frequency modulation of transmitted laser light in response to an applied AC magnetic field is measured. The presented methodology is potentially interesting for low-cost screening of pathogens relating to both human and veterinary medicine in resource-poor regions of the world.
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