Femtomolar limit of detection with a magnetoresistive biochip

In this paper the biological limit of detection of a spin-valve-based magnetoresistive biochip applied to the detection of 20mer ssDNA hybridization events is presented. Two reactional variables and their impact on the biomolecular recognition efficiency are discussed. Both the influence of a 250nm...

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Bibliographic Details
Published in:Biosensors & bioelectronics 2009-04, Vol.24 (8), p.2690-2695
Main Authors: Martins, V.C., Cardoso, F.A., Germano, J., Cardoso, S., Sousa, L., Piedade, M., Freitas, P.P., Fonseca, L.P.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Biosensing Techniques - instrumentation
Biotechnology
DNA - analysis
DNA - chemistry
DNA - genetics
DNA hybridization
Electric Impedance
Electrochemistry - instrumentation
Equipment Design
Equipment Failure Analysis
Fundamental and applied biological sciences. Psychology
In Situ Hybridization - instrumentation
Limit of detection
Magnetic focusing
Magnetic labels
Magnetics - instrumentation
Magnetoresistive biochip
Nanotechnology - instrumentation
Oligonucleotide Array Sequence Analysis - instrumentation
Reproducibility of Results
Sensitivity and Specificity
Spin-valve
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Summary:In this paper the biological limit of detection of a spin-valve-based magnetoresistive biochip applied to the detection of 20mer ssDNA hybridization events is presented. Two reactional variables and their impact on the biomolecular recognition efficiency are discussed. Both the influence of a 250nm diameter magnetic particle attached to the target molecule during the hybridization event and the effect of a magnetic focusing system in the hybridization of pre-labeled target DNA (assisted hybridization) are addressed. The particles carrying the target molecules are attracted to the probe active sensor sites by applying a 40mA DC current on U-shaped aluminium current lines. Experiments comparing pre-hybridization versus post-hybridization magnetic labeling and passive versus magnetically assisted hybridization were conducted. The efficiency of a passive hybridization is reduced by about 50% when constrained to the operational conditions (sample volume, reaction time, temperature and magnetic label) of an on-chip real-time hybridization assay. This reduction has shown to be constant and independent from the initial target concentration. Conversely, the presence of the magnetic label improved the limit of detection when a magnetically assisted hybridization was performed. The use of a labeled target focusing system has permitted a gain of three orders of magnitude (from 1pM down to 1fM) in the sensitivity of the device, as compared with passive, diffusion-controlled hybridization.
ISSN:0956-5663
1873-4235
DOI:10.1016/j.bios.2009.01.040