Rapid quantification of artemisinin derivatives in antimalarial drugs with dipstick immunoassays.

Substandard antimalarial drugs will result in unsatisfied therapeutic efficacy and increase the risk of resistance development. The point-of-care, qualitative, or semi-quantitative dipstick immunoassays cannot differentiate the substandard drugs with confidence. A rapid and quantitative analytical method that can be used under field conditions is needed. Here, three lateral flow immunoassays (LFIAs) based on colloidal gold nanobeads (CGN) as labels were developed for quantification of artemether, dihydroartemisinin and artesunate contents in antimalarial drugs with the aid of a portable optical scanner. Also, time-resolved fluorescent nanobeads (TRFN)-LFIA, coupled with a portable fluorescent lateral flow reader, was developed for quantification of artesunate. Commercial antimalarial drugs were used to validate these LFIAs with comparison to the gold standard high-performance liquid chromatography (HPLC) method. The drug contents estimated with these CGN-LFIAs were in the range of 85.5-109.3% of the contents determined by HPLC with a coefficient of variation (CV) of 4.5-13.0%. The TRFN-LFIA results were in the range of 93.7-108.4% of contents determined by HPLC with a CV of 5.2-8.9%. There were no significant differences between the results of CGN-LFIA and TRFN-LIFA (P = 0.5277, t-test). Both types of LFIAs with portable readers may be used for quantitation of active ingredients in antimalarial drugs and for screening substandard antimalarial drugs in resource-limiting settings.