Label free detection of auramine O by G-quadruplex-based fluorescent turn-on strategy.

Auramine o (AO) is a synthetic dye used in paper and textile industries. Although it has been an unauthorized food additive in many countries due to its toxic and carcinogenic possibility, its illegal uses have been detected in certain food products such as pasta, semolina and spices and also in pharmaceuticals. The presence of AO in food products should be monitored, therefore, to minimize the negative health effects on consumers. In this study, a simple, highly sensitive and selective label free detection method was investigated for AO by G-quadruplex-based fluorescent turn-on strategy. The optimum fluorescent detection assay was achieved with a specific G-quadruplex DNA sequence, c-myc, at 400 nM in Tris-HCl buffer at pH 7.4. The linearity of fluorescence intensity depending on AO concentration ranged from 0 to 0.07 µM and LOD and LOQ were 3 nM and 10 nM, respectively. The G-quadruplex-based detection assay was highly specific for AO as compared to other two synthetic food colorings and successfully applied to determine AO in pasta, bulgur and curry powder with recoveries in the range from 70.33% to 106.49%. This G-quadruplex-based label free detection assay has a significant potential to be used in the detection of AO in food products.

Inhibition of cell migration and invasion by ICAM-1 binding DNA aptamers.

Cancer is the second leading cause of death worldwide and most of the cancer-related deaths result from metastasis. As expressed on the surface of various cancer cell types, intercellular adhesion molecule-1 (ICAM-1) has been shown to play a role in the attachment, invasion and migration of tumor cells. In this study, DNA aptamers were generated against ICAM-1 by cell-SELEX and protein SELEX method using ICAM-1(+) CHO-ICAM-1 cells and ICAM-1 protein, respectively. The pools obtained at the end of the 10th round of both SELEX were sequenced and the most enriched sequences were characterized for their binding behaviors and affinities to ICAM-1(+) CHO-ICAM-1 and ICAM-1(-) MIA PaCa-2 cells. Moreover, the inhibition abilities of sequences on migration and invasion were measured. The seven aptamer sequences were obtained selectively binding to CHO-ICAM-1 cells with Kd values in the ranging from 13.8 to 47.1 nM. Four of these aptamers showed inhibition in both migration and invasion of CHO-ICAM-1 cells at least 61%. All these results suggested that these aptamers have potential to detect specifically ICAM-1 expressing tumor cells and inhibit migration and invasion by blocking ICAM-1 related interactions of circulating tumor cells.