Abstract
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.
Highlights
Malaria is a deadly disease caused by the protozoan parasite Plasmodium falciparum that affects resource-limited regions such as Africa and South-east Asia [1]
The dyes were functionalized via conjugation with CQ for the CQ-tagged derivative compounds SQR1-CQ and SQR2-CQ, which could be developed as potential malaria drug or diagnostic probes
Synthesis of Squaraine near infrared (NIR) Dye Conjugated with Chloroquine
Summary
Malaria is a deadly disease caused by the protozoan parasite Plasmodium falciparum that affects resource-limited regions such as Africa and South-east Asia [1]. Several groups were focusing on resolving the problem of CQ resistance in malaria, such as by seeking ways towards new uses of CQ in practical applications against malaria [2,3,4,5]. Some of these novel approaches involve modification of CQ and related compounds towards fluorescence-based diagnostic applications [3,6,7]. The dyes were functionalized via conjugation with CQ for the CQ-tagged derivative compounds SQR1-CQ and SQR2-CQ, which could be developed as potential malaria drug or diagnostic probes
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