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Open AccessFeature PaperArticle

Elution of Artificial Sputum from Swab by Rotating Magnetic Field-Induced Mechanical Impingement

Department of Mechanical Engineering, School of Biomedical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada
Department of Pathology and Molecular Medicine, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada
Author to whom correspondence should be addressed.
Appl. Sci. 2017, 7(12), 1255;
Received: 2 October 2017 / Revised: 29 November 2017 / Accepted: 30 November 2017 / Published: 3 December 2017
(This article belongs to the Special Issue Microsystems for Bio Applications)
Cotton-tipped applicator swabs are used as a collection device for many biological samples and its complete elution is a desired step for clinical and forensic diagnostics. Swabs are used to collect infectious body fluids, where the concentration of pathogens can range from 1 × 104 CFU/mL (colony forming units/mL) in respiratory-tract infections and 1 × 105 in urinary-tract infections, to up to 1 × 109 CFU/mL in salivary samples. These samples are then eluted and lysed, prior to DNA (De-oxy Ribonucleic Acid) analysis. The recovery of micro-organisms from a matrix of swab fibres depends on the nature of the body fluid, the type of the swab fibres, and the process of elution. Various methods to elute samples from swab include chemical digestion of fibres (~20% recovery), centrifugation (~58% recovery), piezoelectric vibration, or pressurized fluid-flow (~60% recovery). This study reports a magnetically-actuated physical impingement method for elution and recovery of artificial sputum samples from cotton fibres. A device has been fabricated to induce a rotating magnetic field on smaller magnetic particles in a vial that strikes the swab within a confined gap. Elution from the swab in this device was characterized using 2% Methyl cellulose in deionised water, loaded with fluorescent-tagged polystyrene beads and E. coli at various concentrations. The recovery efficiency was found to increase with both rotational speed and elution time, but plateaus after 400 RPM (Revolutions per minute) and 120 s, respectively. At a higher concentration of polystyrene beads (5 × 108 particles/mL), a maximum recovery of ~85% was achieved. With lower concentration, (1 × 105 particles/mL) the maximum efficiency (~92.8%) was found to be almost twice of passive elution (46.7%). In the case of E. coli, the corresponding recovery efficiency at 3.35 × 105 CFU/mL is 90.4% at 500 RPM and 120 s. This elution method is expected to have a wide applicability in clinical diagnostics. View Full-Text
Keywords: swab; elution; magnetic field; recovery efficiency; impingement swab; elution; magnetic field; recovery efficiency; impingement
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MDPI and ACS Style

Banik, S.; Mahony, J.; Selvaganapathy, P.R. Elution of Artificial Sputum from Swab by Rotating Magnetic Field-Induced Mechanical Impingement. Appl. Sci. 2017, 7, 1255.

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