title: Direct transfer of HRPII-magnetic bead complexes to malaria rapid diagnostic tests significantly improves test sensitivity.
abstract: The characteristic ease of use, rapid time to result, and low cost of malaria rapid diagnostic tests (RDTs) promote their widespread use at the point-of-care for malaria detection and surveillance. However, in many settings, the success of malaria elimination campaigns depends on point-of-care diagnostics with greater sensitivity than currently available RDTs. To address this need, a sample preparation method was developed to deliver more biomarkers onto a malaria RDT by concentrating the biomarker from blood sample volumes that are too large to be directly applied to a lateral flow strip.
  
  
  
  In this design, Ni-NTA-functionalized magnetic beads captured the Plasmodium falciparum biomarker HRPII from a P. falciparum D6 culture spiked blood sample. This transfer of magnetic beads to the RDT was facilitated by an inexpensive 3D-printed apparatus that aligned the sample tube with the sample deposition pad and a magnet beneath the RDT. Biomarkers were released from the bead surface onto the lateral flow strip using imidazole-spiked running buffer. Kinetics of HRPII binding to the Ni-NTA beads as a function of blood sample volume were explored prior to determining the effect of the proposed method on the limit of detection of Paracheck RDTs.
  
  
  
  More than 80 % of HRPII biomarkers were extracted from blood sample volumes ranging from 25 to 250 µL. The time required to reach 80 % binding ranged from 5 to 60 min, depending on sample volume. Using 250 μL of blood and a 30-min biomarker binding time, the limit of detection of the Paracheck Pf RDT brand was improved by 21-fold, resulting in a limit of detection below 1 parasite/μL.
  
  
  
  This approach has the sensitivity and simplicity required to assist in malaria elimination campaigns in settings with limited access to clinical and laboratory resources.
authors: Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA.
authors: Keersten M
authors: KM
authors: Ricks
authors: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors: Nicholas M
authors: NM
authors: Adams
authors: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors: Thomas F
authors: TF
authors: Scherr
authors: Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA.|Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, 37235, USA.
authors: Frederick R
authors: FR
authors: Haselton
authors: Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA. david.wright@vanderbilt.edu.
authors: David W
authors: DW
authors: Wright
mesh_terms: D000953:Antigens, Protozoan / Q000097:blood*; D015415:Biomarkers / Q000097:blood*; D002846:Chromatography, Affinity / Q000379:methods; D003955:Diagnostic Tests, Routine / Q000379:methods*; D006801:Humans; D016778:Malaria, Falciparum / Q000175:diagnosis*; D008863:Microspheres; D019095:Point-of-Care Systems; D015800:Protozoan Proteins / Q000097:blood*; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods*
chemical_list: D000953:Antigens, Protozoan; D015415:Biomarkers; C514457:HRP-2 antigen, Plasmodium falciparum; D015800:Protozoan Proteins
keywords: Biomarker concentration; Diagnostics; Extraction; Magnetic beads; Malaria