Optimizing soyasaponin–carbon quantum dots for targeting multiple myeloma cells as a natural-derived and cost-effective theranostic system

Multiple myeloma is a malignant plasma cell disorder in which monoclonal plasma cells proliferate in the bone marrow, resulting in a high concentration of monoclonal paraprotein, bone damage, and the displacement of other hematopoietic cell types. The cancer's drug resistance, due to its complex growth in the bone marrow microenvironment, has limited many medical treatments from overcoming its aggressiveness. Thus, there is an urgent need to develop ultra-small "nano-dots” capable of penetrating bone marrow and selectively targeting multiple myeloma. Natural Carbon Quantum Dots have attracted much attention owing to their remarkable qualities, including low toxicity, luminescence, photostability, nanoscale size, water solubility, biocompatibility, and affordability. To create carbon quantum dots, isolated soyasaponin was first coupled to chitosan–biotin and used in the hydrothermal process. 2-bromoresorcinol (2Br) or 4-bromoresorcinol (4Br) were used to dope the dots with bromine. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), UV–Vis absorption spectroscopy, and fluorescence spectroscopy have all been used to clarify the physical and chemical characteristics of soyasaponin carbon quantum dots. The distinctive fluorescence characteristics of bromine-doped soyasaponin CQDs make them highly promising for biological applications. The FTIR and XRD demonstrated the effective attachment of biotin to carbon quantum dots during fabrication. As a natural substance, CQDs made from isolated soyasaponin have enormous potential for the creation of tailored imaging and treatment strategies after incubation with K562 and MMS1 multiple myeloma cell lines. The cell inhibitory assay, Annexin V/PI, intracellular ROS measurement and Mitotracker were investigated. The results confirmed that 4Br-CQDs and 2Br-CQDs induced the necrotic stage in MMS1 (38.1±1% and 22.5±0.21%, respectively) and induced late apoptosis in K562 (42.8±3.6 % and 47.9±9.3 %, respectively) after incubation for 24 h. It can be summarised that functionalized CQDs doped with bromine represent an alternative, promising strategy for cancer diagnosis and treatment.