Abstract
Cancer cells contain a unique set of cell surface receptors that provide potential targets for tumor theranostics. Here, we propose an efficient approach to construct G-quadruplex-based aptamers that specifically recognize cell-surface receptors and monitor them in an amplified manner. This designed aptamer combined particular sequence for the c-Met on the cell surface and poly-G-quadruplexes structures that allow a rapid and amplified fluorescent readout upon the binding of thioflavin T (ThT). The poly-G-quadruplexes also function as a carrier for photosensitizers such as TMPyP4 in that, the aptamer further trigger the production of reactive oxygen species (ROS) to commit cells to death. This unique c-Met targeting aptamer enabled simultaneous monitoring of c-Met on the cell surface with ThT and photodynamic killing of these lung cancer cells with TMPyP4. This strategy is expected to enhance the development of tumor-targeted diagnosis and drug delivery.
Highlights
A few analyses including western blotting, enzyme-linked immunosorbent assay (ELISA) and flow cytometry are widely used to examine the levels of cell-surface receptors[10,11,12,13]
To construct the poly-G-quadruplexes conjugated probe, we first designed an aptamer-primer with three parts: the 3′-end region with a random primer sequence for in vitro TdT polymerization; the 5′-terminal region with an aptamer sequence; a 17 poly-T bases linker between the two regions (Supplemental Fig. 1)
Fluorescent signal of thioflavin T (ThT) at 485 nm decreased with the increased the level of TMPyP4 (Fig. 5d), which is consistent with quantification result from confocal imaging. These results indicated that the TMPyP4 competed with ThT and formed a complex with the poly-G-quadruplexes at the cell surface of A549 cells
Summary
A few analyses including western blotting, enzyme-linked immunosorbent assay (ELISA) and flow cytometry are widely used to examine the levels of cell-surface receptors[10,11,12,13] These techniques are highly dependent on the qualities of antibodies conjugated with either fluorescent organic dyes or nanoparticles. These methods require tedious cell fixation and washing steps to achieve sufficient signal to background ratios for cell imaging and analysis. Most cell-surface sensors anchor the cell surface with low selectivity, and some fabrication processes require toxic chemical reactions or intrinsic genetic manipulations Those drawbacks limit the practical usage and further clinical application of some sensors[16,17,18,19]. The development of PDT may bring novel opportunities to future cancer treatment
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