Dual-force aggregation of magnetic particles enhances label-free quantification of DNA at the sub-single cell level |
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Authors: | Daniel A Nelson Briony C Strachan Hillary S Sloane Jingyi Li James P Landers |
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Institution: | 1. Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22904, USA;2. Department of Pathology, University of Virginia Health Science Center, Charlottesville, VA 22908, USA;3. Department of Mechanical Engineering, University of Virginia, Engineer''s Way, Charlottesville, VA 22904, USA |
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Abstract: | We recently reported the ‘pinwheel effect’ as the foundation for a DNA assay based on a DNA concentration-dependent aggregation of silica-coated magnetic beads in a rotating magnetic field (RMF). Using a rotating magnet that generated a 5 cm magnetic field that impinged on a circular array of 5 mm microwells, aggregation was found to only be effective in a single well at the center of the field. As a result, when multiple samples needed to be analyzed, the single-plex (single well) analysis was tedious, time-consuming and labor-intensive, as each well needed to be exposed to the center of the RMF in a serial manner for consistent well-to-well aggregation. For more effective multiplexing (simultaneous aggregation in 12 wells), we used a circular array of microwells and incorporated ‘agitation’ as a second force that worked in concert with the RMF to provide effective multiplexed aggregation-based DNA quantitation. The dual-force aggregation (DFA) approach allows for effective simultaneous aggregation in multiple wells (12 demonstrated) of the multi-well microdevice, allowing for 12 samples to be interrogated for DNA content in 140 s, providing a ∼35-fold improvement in time compared to single-plex approach (80 min) and ∼4-fold improvement over conventional fluorospectrometric methods. Furthermore, the increased interaction between DNA and beads provided by DFA improved the limit of detection to 250 fg μL−1. The correlation between the DFA results and those from a fluorospectrometer, demonstrate DFA as an inexpensive and rapid alternative to more conventional methods (fluorescent and spectrophotometric). |
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Keywords: | Aggregation Rotating magnetic field Deoxyribonucleic acid Quantification |
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