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Sci Rep. 2018 Mar 7;8(1):4122. doi: 10.1038/s41598-018-22378-7.

Detection of the Malaria causing Plasmodium Parasite in Saliva from Infected Patients using Topoisomerase I Activity as a Biomarker.

Author information

Zymonostics, Aarhus, Denmark.
Department of Molecular Biology and Genetics, University of Aarhus, Aarhus, Denmark.
Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon.
Department of Medicine, I, Division of Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria.
Institut für Tropenmedizin, Universität Tübingen, Tübingen, Germany.
Department of Infectious Diseases, Aarhus University Hospital, Aarhus, Denmark.
Department of Infectious Diseases, The Royal Hospital, Muscat, Oman.
Department of Clinical Medicine, University of Aarhus, Aarhus, Denmark.
Division of Biomedical Engineering, Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
Department of Mathematics, University of Aarhus, Aarhus, Denmark.
Department of Molecular Biology and Genetics, University of Aarhus, Aarhus, Denmark.


Malaria is among the major threats to global health with the main burden of disease being in rural areas of developing countries where accurate diagnosis based on non-invasive samples is in high demand. We here present a novel molecular assay for detection of malaria parasites based on technology that may be adapted for low-resource settings. Moreover, we demonstrate the exploitation of this assay for detection of malaria in saliva. The setup relies on pump-free microfluidics enabled extraction combined with a DNA sensor substrate that is converted to a single-stranded DNA circle specifically by topoisomerase I expressed by the malaria causing Plasmodium parasite. Subsequent rolling circle amplification of the generated DNA circle in the presence of biotin conjugated deoxynucleotides resulted in long tandem repeat products that was visualized colorimetrically upon binding of horse radish peroxidase (HRP) and addition of 3,3',5,5'-Tetramethylbenzidine that was converted to a blue colored product by HRP. The assay was directly quantitative, specific for Plasmodium parasites, and allowed detection of Plasmodium infection in a single drop of saliva from 35 out of 35 infected individuals tested. The results could be determined directly by the naked eye and documented by quantifying the color intensity using a standard paper scanner.

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