Potential biomarkers and their applications for rapid and reliable detection of malaria

Abstract

Malaria has been responsible for the highest mortality in most malaria endemic countries. Even after decades of malaria control campaigns, it still persists as a disease of high mortality due to improper diagnosis and rapidly evolving drug resistant malarial parasites. For efficient and economical malaria management, WHO recommends that all malaria suspected patients should receive proper diagnosis before administering drugs. It is thus imperative to develop fast, economical, and accurate techniques for diagnosis of malaria. In this regard an in-depth knowledge on malaria biomarkers is important to identify an appropriate biorecognition element and utilize it prudently to develop a reliable detection technique for diagnosis of the disease. Among the various biomarkers, plasmodial lactate dehydrogenase and histidine-rich protein II (HRP II) have received increasing attention for developing rapid and reliable detection techniques for malaria. The widely used rapid detection tests (RDTs) for malaria succumb to many drawbacks which promotes exploration of more efficient economical detection techniques. This paper provides an overview on the current status of malaria biomarkers, along with their potential utilization for developing different malaria diagnostic techniques and advanced biosensors.

Figure 1

Schematic alignment of hrp II and hrp III genes including 5′ and 3′ UTRs. INT and SEC L stand for intron and secretory leader, respectively. The gene consists of a hydrophobic signal peptide (brown), an intervening intron, and an extensive region of tandem repeats (pink). The high homology (85–90%) between the tandem repeat domains and the regions flanking the repeats of hrp II and hrp III genes is shown [51].

Figure 2

Fe⁺³ PPIX (protoporphyrin IX) binding to HRP II is able to bring about an interaction between two monomers resulting in the formation of an intermolecular disulphide bond.

Figure 3

Detection of pLDH by electrochemical impedance spectroscopy. The aptamer is shown as a chain of different coloured circles, representing the four bases A, T, G, and C. Capture of pLDH by aptamer results in a decrease in electron transfer to electrode. The pLDH aptasensor can distinguish between malaria positive blood samples of two major species (P. vivax and P. falciparum) and has a detection limit of 1 pM. [115].

Figure 4

Fabrication of a sandwich immunoassay using screen-printed electrodes (SPEs) modified with gold nanoparticles and carbon nanotubes. This approach used ALP-conjugated antibodies which produce 1-naphthol as the hydrolyzed product of 1-naphthylphosphate (the enzymatic substrate) for the amperometric detection of HRP II [116]. BSA: bovine serum albumin; ALP: alkaline phosphatase.

Figure 5

Detection of HRP II based on a magnetic sandwich immunoassay performed on magnetic beads or nanoparticles modified with monoclonal anti-HRP II IgM antibody. Detection is done using a monoclonal IgG antibody labelled with horse radish peroxidase to obtain an optical or electrochemical signal [117].

Figure 6

The immunocapture Plasmodium lactate dehydrogenase (ICpLDH) assay. A schematic of the reaction is shown in which the pLDH is immobilized using a monoclonal antibody. The enzyme activity can be measured using a coupled enzyme assay that generates APADH. The latter reduces nitro blue tetrazolium, a chromogenic substrate, using an enzyme diaphorase. Activity is quantified spectrophotometrically at 650 nm and plotted as a function of percentage parasitemia [118].

Figure 7

Schematic diagram for preparation of piezoelectric immunosensor for HRP II. The mixed self-assembled monolayers (SAMs) of thioctic acid and 1-dodecanethiol were formed on gold surface of quartz crystal. The rabbit anti-PfHRP II antibodies were coupled on mixed SAM modified gold surface of quartz crystal via NHS/EDC activation method. The amount of HRP II molecules bound on the sensitive area of the electrodes is quantitatively measured as a decrease in resonant frequency [119].