title: Dual-force aggregation of magnetic particles enhances label-free quantification of DNA at the sub-single cell level.
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 5mm 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).
authors.affiliation: Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22904, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Nelson
authors.affiliation: Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22904, USA.
authors.forename: Briony C
authors.initials: BC
authors.lastname: Strachan
authors.affiliation: Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22904, USA.
authors.forename: Hillary S
authors.initials: HS
authors.lastname: Sloane
authors.affiliation: Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22904, USA.
authors.forename: Jingyi
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Virginia, McCormick Road, Charlottesville, VA 22904, USA; Department of Pathology, University of Virginia Health Science Center, Charlottesville, VA 22908, USA; Department of Mechanical Engineering, University of Virginia, Engineer's Way, Charlottesville, VA 22904, USA. Electronic address: landers@virginia.edu.
authors.forename: James P
authors.initials: JP
authors.lastname: Landers
mesh_terms: D010582:Bacteriophage lambda / Q000235:genetics; D002477:Cells / Q000737:chemistry / Q000821:virology*; D004267:DNA Viruses / Q000737:chemistry / Q000235:genetics; D004279:DNA, Viral / Q000032:analysis*; D059346:Magnets; D013499:Surface Properties
chemical_list: D004279:DNA, Viral
keywords: Aggregation; Deoxyribonucleic acid; Quantification; Rotating magnetic field