Anthocyanins extract as a non-toxic and green fluorescent label for bioimaging of HER2-positive breast cancer cells

Breast cancer is one of the most common causes of death among women. Fluorescent labeling is an essential research and diagnostic tool in the detection of cancer cells. The development of inexpensive and easily accessible fluorescent probes for the detection of cancerous cells is of great importance. Herein we report a green and inexpensive method for extraction of natural anthocyanin fluorophore from Red Cabbage and demonstrate its application for fluorescent bioimaging of human epidermal growth factor receptor 2 (HER2) positive breast cancer cells using non-covalent conjugation of anthocyanin fluorophores to Trastuzumab antibody. In this work, the extracted anthocyanins were characterized by Fourier transform infrared spectroscopy (FTIR), Ultraviolet-Visible (UV-Vis) and fluorescent spectroscopy. The anthocyanin extract showed proper fluorescent intensity for microscopic fluorescent cell imaging, negligible photobleaching and no sign of cytotoxicity (more than 90% viability). The presence of hydroxy and carboxyl functional groups in the structure of anthocyanins provided the opportunity for the non-covalent conjugation of anthocyanins to antibodies. The fluorescent probe made by non-covalent conjugation of the anthocyanin fluorophores to Trastuzumab antibody was used for specific fluorescent imaging of HER2 receptors on HER2 positive breast cancer cells. This green fluorescent probe may have several future applications in biological diagnosis and bio-imaging techniques.