Quantum dots (QDs), as a new class of biological nanoprobe, its fluorescence properties are related to the detection sensitivity. QDs with different core-shell structures vary in the resistance to the fluorescence quenching during surface modification. In this study, a series of core and core-shell QDs with different structure and composition were designed and synthesized. And they were modified with amphiphilic polymer. Their fluorescence properties during the surface modification were monitored by fluorescence spectroscopy. Experimental results show core QDs are the most easily quenched during the surface modification; the ability of resistance to quenching is enhanced after shell coating on core QDs, and this ability increases with the shell layers increase. Results also indicate the structure and composition of shells affect the resistance to fluorescence quenching. The resistance to fluorescence quenching is greatly enhanced when the core-shell QDs has a reasonable shell structure and composition. Furthermore, specific QD nanoprobes are constructed based on selecting appropriate structure of QDs and coupling with folic acid. The prepared QD nanoprobes are used for detection of breast cancer cells on flow cytometry. The results show that by optimizing the structure of core-shell QDs, the modified hydrophilic QDs have good fluorescence property. And the optimized hydrophilic QDs coupled with folic acid have targeting capability of cancer cells.

Key words: quantum dots, hydrophilic modification, fluorescence property, core-shell structure, cell targeting