Colloidal synthesis of tunably luminescent AgInS-based/ZnS core/shell quantum dots as biocompatible nano-probe for high-contrast fluorescence bioimaging

Tremendous demands for simultaneous imaging of biological entities, along with the drawback of photo-bleaching in fluorescent dyes, have encouraged scientists to apply novel and non-toxic colloidal quantum dots (QDs) in biomedical researches. Herein, a novel aqueous-phase approach for the preparation of multicomponent In-based QDs is reported. Absorption and photoluminescence emission spectra of the as-prepared QDs were tuned by alteration of QDs' composition as Zn-Ag-In-S/ZnS, Ag-In-S/ZnS and Cu-Ag-In-S/ZnS core/shell QDs. In order to reach reproducibly intense and tunable light-emissive colloidal QDs with green, amber, and red color, various optimization steps were carefully performed. The structural characterizations such as EDX, ICP-AES, XRD, TEM and FT-IR measurements were also carried out to demonstrate the success of the present method to prepare extremely quantum-confined QDs capped with functional groups. Then, to ensure their promising biomedical applications, the generated intracellular reactive oxygen species (ROS) by QDs were quantitatively and qualitatively measured in dark conditions and under 405 nm laser irradiation. Our results verified an enhancement in the generation of reactive oxygen species (ROS) and cytotoxic effects in the presence of laser irradiation while their muted toxic effects in dark conditions confirmed biocompatible properties of un-excited In-based QDs. Moreover, bioimaging analysis revealed strong merits of the suggested synthetic route to achieve ideal fluorescent QDs as bright/multi-color optical nano-probes in imaging and transporting pumps in the cell membrane. This further emphasized the potential ability of the present AgInS-based/ZnS QDs in obtaining required results as theranostic agents for simultaneous treatment and imaging of cancer. The harmonized advantages in simplicity and effectiveness of synthesis procedure, excellent structural/optical properties enriched with confirmed biomedical merits in high contrast imaging and potential treatment highlight the present work.