Optical spectrophotometry into hemozoin: towards sensitive malaria diagnosis

The lack of prompt and sensitive diagnosis hampers malaria control and elimination, highlighting the need for next generation technology alternative for the established optical microscopy and Rapid Diagnostic Tests (RDTs) as means of in situ point-of-care malaria parasite detection. Hemozoin (Hz), a byproduct of hemoglobin (Hb) degradation inside human infected red blood cells (RBCs), has been extensively explored as a malaria biomarker. Along with malaria parasite maturation inside the RBC, Hb and Hz proportion is inversely related, which originates specific optical spectra of healthy and infected samples. Herein, we characterized the optical spectra of Plasmodium falciparum-infected RBCs, aiming the development of an innovative diagnostic device, detecting malaria without finger prick blood sampling, measuring directly in patients’ skin. Absorbance and reflectance spectrophotometry demonstrate their potential by increasing the limit of detection (LoD: 12 parasites/μL of RBC) when compared with microscopy or RDT (LoD: 50-200 parasites/μL of RBC). This sensitivity, coupled with the possible integration into a low-cost, fast, and non-invasive diagnostic device meets the growing clinical demands for malaria control and elimination.This work was supported by Fundação para a Ciência e Tecnologia (FCT) national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020. It is also supported by NORTE-01-0145- FEDER-028178 funded by NORTE 2020 Portugal Regional Operational Program under PORTUGAL 2020 Partnership Agreement through the European Regional Development Fund and the FCT. V. Baptista thanks FCT for the SFRH/BD/145427/2019 grant. Maria Isabel Veiga thanks FCT for her contract funding provided through 2020.03113.CEECIND. Susana Catarino thanks FCT for her contract funding provided through 2020.00215.CEECIND