| 1. |
- Østerberg, F. W., et al.
(författare)
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Measurements of Brownian relaxation of magnetic nanobeads using planar Hall effect bridge sensors
- 2012
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Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 40:S1, s. 147-152
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Tidskriftsartikel (refereegranskat)abstract
- We compare measurements of the Brownian relaxation response of magnetic nanobeads in suspension using planar Hall effect sensors of cross geometry and a newly proposed bridge geometry. We find that the bridge sensor yields six times as large signals as the cross sensor, which results in a more accurate determination of the hydrodynamic size of the magnetic nanobeads. Finally, the bridge sensor has successfully been used to measure the change in dynamic magnetic response when rolling circle amplified DNA molecules are bound to the magnetic nanobeads. The change is validated by measurements performed in a commercial AC susceptometer. The presented bridge sensor is, thus, a promising component in future lab-on-a-chip biosensors for detection of clinically relevant analytes, including bacterial genomic DNA and proteins.
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| 2. |
- 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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| 3. |
- Mezger, Anja, et al.
(författare)
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Scalable DNA-Based Magnetic Nanoparticle Agglutination Assay for Bacterial Detection in Patient Samples
- 2015
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 9:7, s. 7374-7382
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a nanoparticle-based assay for the detection of bacteria causing urinary tract infections in patient samples with a total assay time of 4 h. This time is significantly shorter than the current gold standard, plate culture, which can take several days depending on the pathogen. The assay is based on padlock probe recognition followed by two cycles of rolling circle amplification (RCA) to form DNA coils corresponding to the target bacterial DNA. The readout of the RCA products is based on optomagnetic measurements of the specific agglutination of DNA-bound magnetic nanoparticles (MNPs) using low-cost optoelectronic components from Blu-ray drives. We implement a detection approach, which relies on the monomerization of the RCA products, the use of the monomers to link and agglutinate two populations of MNPs functionalized with universal nontarget specific detection probes and on the introduction of a magnetic incubation scheme. This enables multiplex detection of Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa at clinically relevant concentrations, demonstrating a factor of 30 improvement in sensitivity compared to previous MNP-based detection schemes. Thanks to the universal probes, the same set of functionalized MNPs can be used to read out products from a multitude of RCA targets, making the approach truly scalable for parallel detection of multiple bacteria in a future integrated point of care molecular diagnostics system.
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| 4. |
- Österberg, Frederik W, et al.
(författare)
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On-Chip Detection of Rolling Circle Amplified DNA Molecules from Bacillus Globigii Spores and Vibrio Cholerae
- 2014
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 10:14, s. 2877-2882
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Tidskriftsartikel (refereegranskat)abstract
- For the first time DNA coils formed by rolling circle amplification are quantified on-chip by Brownian relaxation measurements on magnetic nanobeads using a magnetoresistive sensor. No external magnetic fields are required besides the magnetic field arising from the current through the sensor, which makes the setup very compact. Limits of detection down to 500 Bacillus globigii spores and 2 pM of Vibrio cholerae are demonstrated, which are on the same order of magnitude or lower than those achieved previously using a commercial macro-scale AC susceptometer. The chip-based readout is an important step towards the realization of field tests based on rolling circle amplification molecular analyses.
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