Aptamers and Their Significant Role in Cancer Therapy and Diagnosis

Abstract

Aptamers are nucleic acid/peptide molecules that can be generated by a sophisticated, well-established technique known as Systematic Evolution of Ligands by EXponential enrichment (SELEX). Aptamers can interact with their targets through structural recognition, as in antibodies, though with higher specificity. With this added advantage, they can be made useful for clinical applications such as targeted therapy and diagnosis. In this review, we have discussed the steps involved in SELEX process and modifications executed to attain high affinity nucleic acid aptamers. Moreover, our review also highlights the therapeutic applications of aptamer functionalized nanoparticles and nucleic acids as chemo-therapeutic agents. In addition, we have described the development of "aptasensor" in clinical diagnostic application for detecting cancer cells and the use of aptamers in different routine imaging techniques, such as Positron Emission Tomography/Computed Tomography, Ultrasound, and Magnetic Resonance Imaging.

Keywords: SELEX (Systematic Evolution of Ligands by EXponential enrichment); aptamers; aptasensors; cancer imaging; cell surface biomarkers; nanoparticles.

Figure 1

Schematic representation of SELEX process—Oligonucleotide library generation, binding, washing, amplification, cloning and sequencing of aptamers.

Figure 2

T2-weighted MRI images of xenograft-bearing nude mice injected with VEGF165-aptamer-USPIO probe (A) and USPIO nanoparticles only (B) from tail vein at a dosage of 9.08nmol/kg body weight. Arrows point to tumor xenografts. Reprinted from [117] with permission from John Wiley and Sons, copyright 2014.

Figure 3

T2-weighted fast spin echo images at the level of the LNCaP tumor on the right side of the mouse taken at 0, 2, 24, 48 h after injection of Apt-hybr-TCL-SPIONs. Reprinted from [118] with permission from John Wiley and Sons, copyright 2011.