Folate Receptor Targeted Fluorescent Carbon Dots : Its Application In Tumor Cells Imaging

In recent years, compared with organic dyes and semiconductor quantum dots, fluorescent carbon dots(CDs) have attracted intensive interest because of their excellent fluorescence performance such as low toxicity、 high photostability against photobleaching and blinking.An efficient approach for targeting and detecting folate-receptor(FR)-positive cancer cells was developed through non-covalent conjugation of folic acid(FA) on polyethyleneimine modified CDs(PEI-CDs).The FA targeted PEI modified CDs(FA-PEI-CDs) can be used as a turn-on fluorescent nanoprobe for folate receptor(FR)-positive cancer cells in vivo and in vitro. The main results are as follows:1. The preparation and characterization of CDs、PEI-CDs and FA-PEI-CDs: To investigate PEI and FA real modification on the CDs surface, we carry out a series of analytical tests of CDs、PEI-CDs and FA-PEI-CDs. By TEM、Zeta potential、AFM、IR 、UV/vis and fluorescence results, it verified that PEI and FA were wrapped in the surface of CDs, and through electrostatic interaction, and preliminary confirmed fluorescence from quenching to recovery.2. The impact of PEI on the fluorescence properties of PEI-CDs: This chapter further validated the turn-on property of the PEI-CDs, first, the pH, ionic strength and storage time was studied. These findings indicated that PEI-CDs had superior stability and has great potential applications in biological imaging. Then, we explore the optical properties of FA-PEI-CDs, indicating that the FL intensity of PEI-CDs is sensitive to the presence of FA and the fluorescence quenching of PEI-CDs by FA. Besides, As a result of the presence of FR, FA desorbs from the surface of PEI-CDs and binds with FR, leading to the recovery of the fluorescence of the PEI-CDs. The fluorescence intensity rapidly increased to original 2.5 times only in 10 min. In the end, the reason of the fluorescence quenching of PEI-CDs by FA,may be because the electron transfer. To sum up, FA-PEI-CDs as a non-toxic, high compatibility of probe has great potential in the targeted and imaging cancer cells.3. The target and imaging of FA-PEI-CDs in cancer cells: we further explored the ability of FA-PEI-CDs to targeted and imaging cancer cells by confocal. All these results indicated that the as-synthesized FA-PEI-CDs can serve as an effective turn-on probe for FR+ cells after incubation for 10 min.