Cell‐Specific Internalization Study of an Aptamer from Whole Cell Selection

Abstract

Nucleic acid aptamers have been shown many unique applications as excellent probes in molecular recognition. However, few examples are reported which show that aptamers can be internalized inside living cells for aptamer functional studies and for targeted intracellular delivery. This is mainly due to the limited number of aptamers available for cell-specific recognition, and the lack of research on their extra- and intracellular functions. One of the major difficulties in aptamers' in vivo application is that most of aptamers, unlike small molecules, cannot be directly taken up by cells without external assistance. In this work, we have studied a newly developed and cell-specific DNA aptamer, sgc8. This aptamer has been selected through a novel cell selection process (cell-SELEX), in which whole intact cells are used as targets while another related cell line is used as a negative control. The cell-SELEX enables generation of multiple aptamers for molecular recognition of the target cells and has significant advantages in discovering cell surface binding molecules for the selected aptamers. We have studied the cellular internalization of one of the selected aptamers. Our results show that sgc8 is internalized efficiently and specifically to the lymphoblastic leukemia cells. The internalized sgc8 aptamers are located inside the endosome. Comparison studies are done with the antibody for the binding protein of sgc8, PTK7 (Human protein tyrosine kinase-7) on cell surface. We also studied the internalization kinetics of both the aptamer and the antibody for the same protein on the living cell surface. We have further evaluated the effects of sgc8 on cell viability, and no cytotoxicity is observed. This study indicates that sgc8 is a promising agent for cell-type specific intracellular delivery.

Self-assembled, aptamer-tethered DNA nanotrains for targeted transport of molecular drugs in cancer theranostics

“…For efficient drug transport, it is essential that macromolecular drug transporters be internalized by diseased cells. Previous work showed that sgc8 was specifically internalized by target CEM cells via endocytosis (35). Compared with the results of a study using sgc8-NTrs at 4°C (Fig.…”

“…Cells were treated with free Dox, as a control, or Dox transported by sgc8-NTrs, respectively, followed by microscopic examination. In addition, transferrin-Alexa 633 was used to locate the endosomes (35). The recovery of Dox fluorescence (fluorescence "ON") after release from nanotrains enabled the real-time signaling of intracellular drug unloading.…”

DNA-based aptamer fails as a simultaneous cancer targeting agent and drug delivery vehicle for a phenanthroline-based platinum(II) complex

“…The sgc8 aptamer, from which sgc8c is derived is known to be taken into cells via receptor mediated endocytosis [22]. Computer modelling.…”

Aptamer-based molecular imaging

“…Direct imaging of protein colocalization (nucleolin and integrin αvβ 3 ) based on FRET has also been reported (Kang et al, 2009b). In addition to cellular localization, fluorescence labeled aptamers have been used to study protein trafficking including endocytosis of human protein kinase-7 (PTK7) from membrane into endosome (Xiao et al, 2008) and endocytosis of angiogenin into cytoplasm and nuclei as scattered spots (Li et al, 2008). Particularly, protein trafficking dynamics has been imaged and quantified in real-time in living cells by an aptamer probe.…”