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Open AccessArticle

Near Infrared Fluorophore-Tagged Chloroquine in Plasmodium falciparum Diagnostic Imaging

1
Department of Technology, Innovation and Enterprise (TIE), Singapore Polytechnic, 500 Dover Road, Singapore 139651, Singapore
2
Laboratory of Molecular and Cellular Parasitology, Department of Microbiology and Immunology, National University of Singapore, 5 Science Drive 2 Block MD4, Level 3, Singapore 117545, Singapore
3
Research Institute for Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
4
Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore
*
Author to whom correspondence should be addressed.
Molecules 2018, 23(10), 2635; https://doi.org/10.3390/molecules23102635
Received: 29 September 2018 / Revised: 11 October 2018 / Accepted: 12 October 2018 / Published: 14 October 2018
Chloroquine was among the first of several effective drug treatments against malaria until the onset of chloroquine resistance. In light of diminished clinical efficacy of chloroquine as an antimalarial therapeutic, there is potential in efforts to adapt chloroquine for other clinical applications, such as in combination therapies and in diagnostics. In this context, we designed and synthesized a novel asymmetrical squaraine dye coupled with chloroquine (SQR1-CQ). In this study, SQR1-CQ was used to label live Plasmodium falciparum (P. falciparum) parasite cultures of varying sensitivities towards chloroquine. SQR1-CQ positively stained ring, mature trophozoite and schizont stages of both chloroquine–sensitive and chloroquine–resistant P. falciparum strains. In addition, SQR1-CQ exhibited significantly higher fluorescence, when compared to the commercial chloroquine-BODIPY (borondipyrromethene) conjugate CQ-BODIPY. We also achieved successful SQR1-CQ labelling of P. falciparum directly on thin blood smear preparations. Drug efficacy experiments measuring half-maximal inhibitory concentration (IC50) showed lower concentration of effective inhibition against resistant strain K1 by SQR1-CQ compared to conventional chloroquine. Taken together, the versatile and highly fluorescent labelling capability of SQR1-CQ and promising preliminary IC50 findings makes it a great candidate for further development as diagnostic tool with drug efficacy against chloroquine-resistant P. falciparum. View Full-Text
Keywords: squaraine dye; near infrared; fluorescence; chloroquine; malaria; Plasmodium falciparium squaraine dye; near infrared; fluorescence; chloroquine; malaria; Plasmodium falciparium
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MDPI and ACS Style

Chan, L.Y.; Teo, J.D.W.; Tan, K.S.-W.; Sou, K.; Kwan, W.L.; Lee, C.-L.K. Near Infrared Fluorophore-Tagged Chloroquine in Plasmodium falciparum Diagnostic Imaging. Molecules 2018, 23, 2635.

AMA Style

Chan LY, Teo JDW, Tan KS-W, Sou K, Kwan WL, Lee C-LK. Near Infrared Fluorophore-Tagged Chloroquine in Plasmodium falciparum Diagnostic Imaging. Molecules. 2018; 23(10):2635.

Chicago/Turabian Style

Chan, Li Y.; Teo, Joshua D.W.; Tan, Kevin S.-W.; Sou, Keitaro; Kwan, Wei L.; Lee, Chi-Lik K. 2018. "Near Infrared Fluorophore-Tagged Chloroquine in Plasmodium falciparum Diagnostic Imaging" Molecules 23, no. 10: 2635.

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