Green synthesis of amino acid functionalized CuInS/ZnS- mTHPP conjugate for biolabeling application

Quantum dots (QDs) have been resourceful in bio-applications such as fluorescent tagging, sensing, and bio-assays. Their bio-recognition and subsequent acceptance as foreign bodies by biomolecules largely depend on the surface structure of the QDs. Surface functionalization is thus a critical factor in their synthesis and design. In this work, we report on the surface modification of CuInS/ZnS QDs by an α-amino acid which plays an essential role in cell division and wound healing. The CuInS/ZnS QDs was synthesized via one-step eco-friendly method in a pressure cooker. To improve the biocompatibility and stability, the purified QDs were functionalized with L-arginine using carbodiimide chemistry to produce arginine (Arg) functionalized CuInS/ZnS QDs. Interest in the use of L-arginine amino acid in this study is a result of its zwitterion state, physiological properties, and most importantly its backbone structure which enables ease of conjugation. The Arg-CuInS/ZnS QDs were then conjugated to 5, 10, 15, 20-meso (hydroxyphenyl) porphyrin (mTHPP), a second-generation photosensitizing drug to improve the absorption efficiency of the porphyrin and tagging of cancer cells. This study examined for the first time the effect of amino acid functionalization on the luminescent, absorption and morphology properties of ternary CuInS/ZnS QDs and its porphyrin conjugate using various optical analyses. Furthermore, this study investigated the bio-labeling properties of the prepared material and tested this against leukemia (THP-1) cancer cell lines. The as-synthesized water-soluble biocompatible Arg-CuInS/ZnS - mTHPP conjugate proved to be useful for surface functionalization and as a possible bio-labeling agent.