Luminescence-enhanced Diagnosis and Quantitative Assessment of Malaria Infection through Lateral Flow Immunoassay using CdTe Quantum Dots

Lateral flow immunoassay (LFI) is a simple, low-cost and quick diagnostic tool to identify various diseases by detecting analytes such as antibodies, parasites, or other relevant biomarkers. However, most LFIs diagnose the infections only qualitatively. Also, the conventional LFIs, which rely on visual inspection of the test line suffer from the low-sensitivity in case of mild or early infections and might cause false-negative interpretations. Here, we report the application of thioglycolic acid (TGA) capped CdTe quantum dots (QDs) as a label to enhance the luminescence and subsequently the detection sensitivity of the LFIs for diagnosis of Malaria. The chemical route synthesis of TGA capped CdTe QDs was optimized systematically by probing optical properties of the QDs. These optimized QDs of TGA capped CdTe have been conjugated with the anti-malaria antibodies against HRP2 protein (P. falciparum) and were subsequently incorporated into the LFIs. Further, an image processing code has been developed to carry out the quantification of malaria parasites in terms of the ratio on intensities of control (C) and test (T) lines on the LFIs. The results have been compared with the standard, colloidal gold based, LFIs. It has been demonstrated that the sensitivity of the detection of malaria infection under low parasite concentration improves significantly due to enhanced luminescence of C and T lines under UV illumination, owing to the TGA capped CdTe QDs. It has also been shown that the image processing based quantification of malaria infection can reduce the chances of false-negative results under low parasite concentration and help in carrying out early diagnosis of malaria.