Hernandez L, Flenker K, Hernandez F, Klingelhutz A, McNamara J, Giangrande P (2013) Methods for evaluating cell-specific, cell-internalizing RNA aptamers. Pharmaceuticals (Basel) 6:295-319. doi: 10.3390/ph6030295
Objective: Isolate aptamers that internalize upon binding to their cognate receptor on the cell surface
Summary: Among the methods used to characterize aptamers that internalize is a way to monitor for cytoplasmic delivery using the ribosome inactivating protein-based (RNA-RIP) assay. Biotin-labeled A9g was conjugated to streptavidin-modified saporin (streptavidin-ZAP). First, it was verified that conjugation of biotinylated aptamer to Streptavidin-ZAP (A9g-SAP) did not affect the inhibitory effect of the aptamer. Next, the effect was examined of A9g-SAP on PC3(PSMA+) and PC3(PSMA-) cells. Cells were treated with varying amounts of aptamer-saporin conjugate for 72 h at 37°C and then an assay was performed to determine potential cytotoxicity of the conjugate. Results confirm that A9g is internalized preferentially into target cells and that A9g is efficiently accessing the cytoplasm of target cells possibly through a mechanism of endosomal escape, resulting in inhibition of protein synthesis and ultimate cell-death. FGF-SAP was used as a control.