title: Single-step, paper-based concentration and detection of a malaria biomarker.
abstract: The lateral-flow immunoassay (LFA) is an inexpensive and rapid paper-based assay that can potentially detect infectious disease biomarkers in resource-poor settings. Despite its many advantages that make it suitable for point-of-care diagnosis, LFA is limited by its inferior sensitivity relative to sophisticated laboratory-based assays. Our group previously introduced the use of a micellar aqueous two-phase system (ATPS), comprised of the nonionic Triton X-114 surfactant, to concentrate biomarkers in a sample and enhance their detection with LFA. However, achieving complete phase separation and target concentration using the Triton X-114 system required many hours, and the concentrated sample needed to be manually extracted and applied to LFA. Here, we successfully integrated the concentration and detection steps into a single step that occurs entirely within a portable paper-based diagnostic strip. In a novel approach, we applied the micellar ATPS to a 3-D paper design and effectively reduced the macroscopic phase separation time from 8 h to approximately 3 min. The 3-D design was integrated with LFA to simultaneously concentrate and detect Plasmodium lactate dehydrogenase (pLDH), a malaria biomarker, in both phosphate-buffered saline and fetal bovine serum within 20 min at room temperature. Compared to a conventional LFA setup with a pLDH detection limit of 10 ng μL(-1), our single-step diagnostic successfully detected pLDH at 1.0 ng μL(-1), demonstrating a 10-fold detection limit improvement and resulting in a sensitive and user-friendly assay that can be used at the point-of-care. The integration of a micellar ATPS and LFA represents a new platform that can improve and promote the use of paper-based diagnostic assays for malaria and other diseases within resource-poor settings.
authors.affiliation: Department of Bioengineering, University of California, 420 Westwood Plaza, 5121J Engineering V, P.O. Box 951600, Los Angeles, CA 90095-1600, USA.
authors.forename: David Y
authors.initials: DY
authors.lastname: Pereira
authors.affiliation: Department of Bioengineering, University of California, 420 Westwood Plaza, 5121J Engineering V, P.O. Box 951600, Los Angeles, CA 90095-1600, USA.
authors.forename: Ricky Y T
authors.initials: RY
authors.lastname: Chiu
authors.affiliation: Department of Bioengineering, University of California, 420 Westwood Plaza, 5121J Engineering V, P.O. Box 951600, Los Angeles, CA 90095-1600, USA.
authors.forename: Samantha C L
authors.initials: SC
authors.lastname: Zhang
authors.affiliation: Department of Bioengineering, University of California, 420 Westwood Plaza, 5121J Engineering V, P.O. Box 951600, Los Angeles, CA 90095-1600, USA; Division of Advanced Prosthodontics & Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, CA 90095-1600, USA.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Wu
authors.affiliation: Department of Bioengineering, University of California, 420 Westwood Plaza, 5121J Engineering V, P.O. Box 951600, Los Angeles, CA 90095-1600, USA. Electronic address: kamei@seas.ucla.edu.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Kamei
mesh_terms: D015415:Biomarkers / Q000032:analysis*; D006801:Humans; D057230:Limit of Detection; D008288:Malaria / Q000175:diagnosis*; D010209:Paper
chemical_list: D015415:Biomarkers
keywords: Diagnostic; Lateral-flow immunoassay; Malaria; Micellar aqueous two-phase system; Triton X-114