Development of a Single Stranded DNA Aptamer as a Molecular Probe for LNCap Cells Using Cell-SELEX

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Background:Nowadays, highly specific aptamers generated by cell SELEX technology
(systematic evolution of ligands by exponential enrichment) are being applied for
early detection of cancer cells. Prostate Specific Membrane Antigen (PSMA), over expressed in prostate cancer, is a highly specific marker and therefore can be used for
diagnosis of the prostate cancer cells. The aim of the present study was to select singlestranded DNA aptamers against LNCap cells highly expressing PSMA, using cell–
SELEX method which can be used as a diagnostic tool for the detection of prostate
cancer cells.
Methods:After 10 rounds of cell-SELEX, DNA aptamers were isolated against PSMA
using LNCaP cells as a target and PC-3 cell lines for counter SELEX. Five DNA aptamers with more than 70% affinity were selected up on flowcytometry analysis of positive clones.
Results:Dissociation constants of two selected sequences (A12-B1) were estimated in
the range of 33.783.77 and 57.492.214 pmol, respectively. Conserved secondary structures of A12 and B1 sequences suggest the necessity of these structures for binding with
high affinity to native PSMA. Comparison of the secondary structures of our isolated
aptamers and aptamer A10 obtained by protein SELEX showed similar stem-loop
structures which could be responsible for the recognition of PSMA on LNCap cell surface.
Conclusion: Our results indicated that selected aptamers may turn out to be ideal
candidates for the development of a detection tool and also can be used in targeted
drug delivery for future smart drugs.

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