Distinguishing Folate-Receptor-Positive Cells from Folate-Receptor-Negative Cells Using a Fluorescence Off–On Nanoprobe

Abstract

Based on the high affinity of folic acid (FA) for folate receptor (FR) that is overexpressed on the surface of many human cancer cells, we have developed a simple fluorescence nanoprobe (1) with multiple capability (fluorescence off-on response and cell-targeting ability) for imaging of FR-positive cells by covalently linking both FA and Rhodamine B (RB) to graphene oxide (GO) through disulfide bonds. The nanoprobe shows a weak fluorescence due to the electron transfer from GO to RB. However, the specific binding of FA to FR-positive cells leads to the internalization of the nanoprobe into the cells. As a result, the disulfide bonds of 1 are cleaved by intracellular glutathione, causing the release of the RB moiety from GO and thereby the generation of fluorescence. Compared to most of the reported fluorescence always-on nanoprobes for imaging FR-positive cells, the present fluorescence off-on nanoprobe can not only produce a high signal/background ratio but also avoid the false positive results often caused by nonspecific adsorption of the always-on nanoprobes on the surface of nontarget cells. Notably, the proposed off-on nanoprobe has been demonstrated to distinguish the cells with different expression levels of FR by culturing and analyzing different cell mixtures (Hela/NIH-3T3 and Hela/MCF-7 cells). Moreover, the nanoprobe is capable of discriminating FR-positive from FR-negative cells even with similar morphology. This method is simple and selective for fluorescence imaging of FR-positive cells.

Sensitive Fluorescence Probe with Long Analytical Wavelengths for γ-Glutamyl Transpeptidase Detection in Human Serum and Living Cells

“…The cytotoxicity of CV-Glu to HepG2 cells was evaluated using a standard MTT assay, as described previously. 22 Assay of Cell Lysates. Adherent HepG2 cells were pretreated with varied concentrations of NaBu at 37 °C for 48 h. Then, the cells were digested and adjusted to a density of 1 × 10 6 cells/mL, followed by transferring 2 mL of the cell suspension to a tube and centrifuging at 5000 rpm for 5 min.…”

Fluorescent small Au nanodots prepared from large Ag nanoparticles for targeting and imaging cancer cells

“…25 The level of FR appears to rise as the stage of the cancer increases, whereas in normal cells FR is only sparsely distributed. 26 These characteristics make FA a promising agent for targeting cancer cells by detecting FR. Hitherto, a number of nanomaterials with surface modication by FA have been applied in targeted bioimaging, including Cu nanomaterials, quantum dots, SnO 2 NPs and upconversion NPs.…”

Physicochemically functionalized carbon nanohorns for multi-dimensional cancer elimination

“…KB and FHs173We cells were from American Type Culture Collection [21]. KB cells are FA receptor-positive [22], whereas FHs173We cells were used as a FA receptor-negative control [9]. Before testing for the cellular uptake of FA-PEI-MAG-CN H ox and PEI-MAG-CNH ox , KB cells were grown in low-FA medium (Gibco) to obtain cells overexpressing FA receptors [23].…”