Nucleic acid aptamers can be selected from pool of randomly sequenced oligonucleotides to bind a wide range of biomedically
significant proteins with high affinities and specificities that are comparable to antibodies. While efforts to identify disease-
specific biomarkers using a variety of technologies has increased, effective use of disease-specific biomarkers is still scarce.
Additionally, it is straight forward to conjugate aptamers to other agents without losing their affinity and they have successfully
been used in vitro and in vivo to deliver drugs, siRNA, nanoparticles or contrast agents to target cells. Hence, aptamers identified
against cell surface biomarkers represent a promising class of ligands to detect specific type of cancer cells. Specific Cell-SELEX
method has been developed to identify aptamers for cell surface associated proteins as well as some of the methods that are used
to study their binding to living cells. In contrast to conventional methods, the novelty of cell-SELEX-based biomarker discovery
is rooted in its focus on finding specific cell membrane markers. Moreover, cell- SELEX does not require any prior knowledge
on the molecular contents of the cell surface. Trillions of random DNA sequences in the initial DNA library, combined with the
unique negative selection strategy, ensures that any disease marker molecules on cell membranes can be recognized whether they
are known or unknown to us. Provided the molecules in question are expressed in a substantially different way on diseased and
normal cells, they can be identified. In addition, the aptamers generated during this process can serve as high-affinity and specific
probes for the identified biomarkers. This will be great advancement in future diagnostic applications for cancer therapy.
Arghya Sett completed his MTech in Biotechnology from VIT University. He is currently pursuing his PhD in Dept. of Biotechnology, IIT Guwahati. His
current research interest is in development of novel molecular marker based breast cancer diagnostics.
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