Ultrasensitive and label-free biosensor for the detection of Plasmodium falciparum histidine-rich protein II in saliva

Gita V. Soraya,Chathurika D. Abeyrathne,Duc H. Huynh,Efstratios Skafidas,Jianxiong Chan,Patrick Kwan,Stephen J. Rogerson,Shah Mukim Uddin,Christelle Buffet

doi:10.1038/s41598-019-53852-5

Abstract

Malaria elimination is a global public health priority. To fulfil the demands of elimination diagnostics, we have developed an interdigitated electrode sensor platform targeting the Plasmodium falciparum Histidine Rich Protein 2 (PfHRP2) protein in saliva samples. A protocol for frequency-specific PfHRP2 detection in phosphate buffered saline was developed, yielding a sensitivity of 2.5 pg/mL based on change in impedance magnitude of the sensor. This protocol was adapted and optimized for use in saliva with a sensitivity of 25 pg/mL based on change in resistance. Further validation demonstrated detection in saliva spiked with PfHRP2 from clinical isolates in 8 of 11 samples. With a turnaround time of ~2 hours, the label-free platform based on impedance sensors has the potential for miniaturization into a point-of-care diagnostic device for malaria elimination.

Highlights

Malaria caused by intraerythrocytic Plasmodium parasites remains a significant public health threat
Clinical malaria diagnosis relies on light microscopy (LM) for visual confirmation of parasites or rapid diagnostic tests (RDTs) to detect parasite antigens using lateral-flow technology[5]
Optimization results of capture antibody concentration are provided in Supplementary Figure 1

Summary

Introduction

Malaria caused by intraerythrocytic Plasmodium parasites remains a significant public health threat. A more recent study[14] assessing the current best-in-class PfHRP2 RDTs according to the WHO-Foundation for Innovative New Diagnostics panel[15] found an analytical sensitivity of 0.8 ng/mL It can be inferred from these studies that to achieve the target sensitivity for elimination, PfHRP2 diagnostic tests need to be 1–2 logs lower than achievable by current RDTs. While PfHRP2 ELISAs16–18, PCR19,20 and loop-mediated isothermal amplification (LAMP)[21] assays have shown superior sensitivity to RDTs for detection of low-density infections, the platforms are slow and technically complex assays typically performed by highly-skilled technicians in centralized laboratories. While PfHRP2 ELISAs16–18, PCR19,20 and loop-mediated isothermal amplification (LAMP)[21] assays have shown superior sensitivity to RDTs for detection of low-density infections, the platforms are slow and technically complex assays typically performed by highly-skilled technicians in centralized laboratories Implementation of these methods is impractical in the low-resource settings of many countries striving for malaria elimination

Objectives

Methods

Results

Conclusion