Development of an Original Piezoelectric Biosensor Platform for Real-Time Detection of Plasmodium falciparum Antigens in Whole Blood Samples

Rapid, accurate, and affordable malaria diagnosis is a critical unmet need in Nigeria, where laboratory microscopy is unavailable in most rural health facilities and rapid antigen detection tests have limitations in sensitivity at low parasite densities. Piezoelectric biosensors offer a label-free, real-time, quantitative detection platform that could overcome these limitations, but development of such a platform for Plasmodium falciparum antigen detection from whole blood has not been achieved. This study developed an original quartz crystal microbalance biosensor platform for real-time, quantitative detection of Plasmodium falciparum histidine-rich protein II antigen in whole blood samples. The biosensor surface modification strategy involved sequential deposition of cysteamine self-assembled monolayer, gold nanoparticle amplification layer, and oriented antibody immobilisation using protein A bridge chemistry, followed by blocking with bovine serum albumin and polyethylene glycol. Surface chemistry at each functionalization step was characterised by X-ray photoelectron spectroscopy, atomic force microscopy, electrochemical impedance spectroscopy, and quartz crystal microbalance measurements. Detection performance was evaluated in buffer, plasma, and whole blood matrices using clinical samples from malaria patients attending the University of Jos Teaching Hospital. Limit of detection in whole blood was 0.08 nanograms per millilitre, significantly more sensitive than commercial rapid diagnostic tests. Linear dynamic range spanned four orders of magnitude. Cross-reactivity against common interfering proteins in blood was negligible. Real-time mass change responses allowed kinetic analysis of antibody-antigen binding. Clinical sample testing achieved 97.6 percent sensitivity and 98.8 percent specificity against microscopy gold standard. This original biosensor represents a deployable, quantitative malaria diagnostic tool applicable to the Nigerian primary healthcare context.

Keywords: quartz crystal microbalance, piezoelectric biosensor, malaria diagnosis, Plasmodium falciparum, histidine-rich protein II