1. Conjugates of folic acids with BSA coated quantum dots for cancer cell targeting and imaging by single-photon and two-photon excitations
He Meng, Ji-Yao Chen, Lan Mi, Pei-Nan Wang, Mei-Ying Ge, Yang Yu, Ning Dai
Phys. Dept., Fudan Univ., Shanghai, People’s Republic of China
The BSA coated CdTe/ZnS quantum dots (BSA-QDs) were selected to conjugate with folic acid (FA) forming FA-BSA-QDs to develop these small size FA-BSA-QDs (< 10 nm) for the diagnosis of cancers in which the FA receptor is overexpressed. The enhancement of cellular uptake in for FA-BSA-QDs was found by means of confocal fluorescence microscopy with single-photon and two-photon excitations. The enhancement for FA-BSA-QDs was further evaluated as about 3 times higher averagely as compared to BSA-QDs, measured by flow cytometric analysis. Such uptake enhancement for FA-BSA-QDs was suppressed when KB cells had been pretreated with excess FA, reflecting that the enhancement was mediated by the association of FR in cell membranes with FA-BSA-QDs. When human embryonic kidney cells (293T) (FR negative cells) and KB cells were incubated with FA-BSA-QDs respectively, the FA-BSA-QD uptake of 293T cells was much weak as compared with that of KB cells, demonstrating that FA-BSA-QDs can take a preferential binding on FR positive cancer cells.
A comparison of cellular uptakes of FA-BSA-QDs into
KB cells (a) and 293T cells (b)
In vitro viability of KB cells treated with BSA-QDs or MPA-QDs at different concentrations
A comparison of cellular uptakes of FA-BSA-QDs (a) and BSA-QDs (b) for KB cells by confocal fluorescence and flow cytometric analysis
SPE
TPE
Confocal fluorescence images of FA-BSA-QDs in KB cells. (a) Cells incubated with FA-BSA-QDs (b) Cells treated with excess FA
Comparison of the SPE image and TPE image for the same cells
Excess FA suppressed the uptake enhancement of FA-BSA-QDs
The absorption of QDs for two-photon is lower than that for single photon
We prepared new FA-BSA-QD conjugates for cancer diagnosis,which improve the cellular uptake of FR positive KB cells as compared to BSA-QDs and have a preferential binding on KB cells but not the FR negative 293T cells, demonstrating a specific selection to FR positive cancer cells. The cell imaging of FA-BSA-QDs measured TPE suggest a potential application for in vivo tumor detections with a near-infrared fs laser. FA-BSA-QDs seem suitable for tumor diagnosis and worth investigating further.