Abstract Description

Malaria is a leading cause of morbidity and mortality in sub-Saharan Africa, and occurrence of coinfection with other diseases of similar symptoms necessitates the development of malaria-specific and sensitive diagnostic tool for its diagnosis. Thus, we explored two aptamers (2008s and rLDH7) to detect the presence of a recombinant malaria biomarker – Plasmodium falciparum lactate dehydrogenase (rPfLDH) in a ligand exchange assay (LEA). Gold nanoparticles (AuNPs) were synthesized using citrate reduction method, conjugated to 2008s and rLDH7 aptamers, and characterized using UV-Visible spectrophotometer, dynamic light scattering (DLS) and polyacrylamide gel electrophoresis (PAGE). Following, the conjugates (AuNPs-rLDH7 and AuNPs-2008s) were validated to detect rPfLDH and two protein controls (Human and bovine serum albumin (HSA and BSA). Whilst rLDH7 demonstrated potential for rPfLDH detection in LEA, differentiating between target and non-targets, and achieving an apparent KD of 4.96 nM, 2008s did not show a convincing sensitivity in this biosensor format despite showing effectiveness in electrophoretic mobility shift assay (EMSA) and other designs. These results suggest that the chemistry of 2008s aptamer attachment to AuNPs surface might have caused conformational changes to its secondary structure preventing the target-binding arrangements. LEA is an easy-to-use biosensor configuration. However, aptamer sequences should be screened for efficiency before further development to avoid using excessive amounts (>10 µM), which would decrease affordability.