In this paper, we describe the newly designed liposomes modified with amphiphilic far-red squaraine dye and folic acid for its application in folate receptor-targeted bioimaging. Enhanced intracellular uptake of the engineered liposomes has been demonstrated on SKOV-3 ovarian cancer cells.

Thermosensitive fluorescent dyes can convert thermal signals into optical signals as a molecular nanoprobe. These nanoprobes are playing an increasingly important part in optical temperature sensing and imaging at the nano- and microscale. However, the ability of a fluorescent dye itself has sensitivity and accuracy limitations. Here we present a molecular strategy based on self-assembly to overcome such limitations. We found that thermosensitive nanovesicles composed of lipids and a unique fluorescent dye exhibit fluorescence switching characteristics at a threshold temperature. The switch is rapid and reversible and has a high signal to background ratio (>60), and is also highly sensitive to temperature (10–22%/°C) around the threshold value. Furthermore, the threshold temperature at which fluorescence switching is induced, can be tuned according to the phase transition temperature of the lipid bilayer membrane forming the nanovesicles. Spectroscopic analysis indicated that the fluorescence switching is induced by the aggregation-caused quenching and disaggregation-induced emission of the fluorescent dye in a cooperative response to the thermotropic phase transition of the membrane. This mechanism presents a useful approach for chemical and material design to develop fluorescent nanomaterials with superior fluorescence sensitivity to thermal signals for optical temperature sensing and imaging at the nano- and microscales.

Thermosensitive lipid-based nanoparticle (liposome) is a key platform for the controlled release of functional molecules by regional heating. Temperature monitoring in a three-dimensional matrix is necessary to conduct controlled heating at the targeted region. Currently, conventional liposomes do not possess a function for temperature monitoring. Herein, an extended concept for temperature monitoring using the liposomes was examined using near-infrared (NIR) laser-induced heating of water in hydrogel. The temperature distribution in hydrogel by photothermal conversion can now be traced by fluorescence in real time, with the use of liposomes that release the fluorescence cargo at different threshold temperatures. The liposome platform, equipped with temperature-sensing capability, extend the concept of temperature monitoring for temperature-triggered drug release, as well as thermotherapy.

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.

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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 a chloroquine-BODIPY (borondipyrromethene) conjugate. 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 potentiates it to be further developed as a promising diagnostic bioimaging tool with drug efficacy against chloroquine-resistant P. falciparum.