Surface Modification of Nanoparticles Used in Biomedical Applications | InTechOpen, Published on: 2013-05-22. Authors: Evrim Umut

²⁰⁹Bi containing species have the potential to become novel contrast agents for MRI.

Fluorescent graphitic carbon nitride (g-C₃N₄) doped with various heteroatoms, such as B, P, and S, named ^Bg-C₃N₄, ^Pg-C₃N₄, and ^Sg-C₃N₄, were synthesized with variable band-gap values as diagnostic materials. Furthermore, they were embedded within hyaluronic acid (HA) microgels as g-C₃N₄@HA microgel composites. The g-C₃N₄@HA microgels had a 0.5–20 μm size range that is suitable for intravenous administration. Bare g-C₃N₄ showed excellent fluorescence ability with 360 nm excitation wavelength and 410–460 emission wavelengths for possible cell imaging application of g-C₃N₄@HA microgel composites as diagnostic agents. The g-C₃N₄@HA-based microgels were non-hemolytic, and no clotting effects on blood cells or cell toxicity on fibroblasts were observed at 1000 μg/mL concentration. In addition, approximately 70% cell viability for SKMEL-30 melanoma cells was seen with ^Sg-C₃N₄ and its HA microgel composites. The prepared g-C₃N₄@HA and ^Sg-C₃N₄@HA microgels were used in cell imaging because of their excellent penetration capability for healthy fibroblasts. Furthermore, g-C₃N₄-based materials did not interact with malignant cells, but their HA microgel composites had significant penetration capability linked to the binding function of HA with the cancerous cells. Flow cytometry analysis revealed that g-C₃N₄ and g-C₃N₄@HA microgel composites did not interfere with the viability of healthy fibroblast cells and provided fluorescence imaging without any staining while significantly decreasing the viability of cancerous cells. Overall, heteroatom-doped g-C₃N₄@HA microgel composites, especially ^Sg-C₃N₄@HA microgels, can be safely used as multifunctional theragnostic agents for both diagnostic as well as target and treatment purposes in cancer therapy because of their fluorescent nature.