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M. Irfan et al.
order to make suitable medical decisions. In the same way, therapeutic methods for
disease treatment need to shift from broad spectrum medications toward the use of
more tailored drugs personalized to each patient [3]. Out of numerous approaches
for meeting these demands, the use of DNA aptamers is a handy tool, whose progress
matches that of personalized medicine [4]. In this chapter we will decipher the potential of aptamers in personalized medicine at different levels right starting from primitive scale, the hurdles, their advantages and disadvantages, the examples which are
successfully integrated in personalized medicines, and the gaps which are still under
consideration by the scientific community. Aptamers alone or in combination such
as aptamer chimeras and aptamer-decorated multimodal nanosystems make them a
robust tool for targeting and delivery of various therapeutic systems. At the end, we
will present a brief future perspective.
7.1.1 Advantages of Aptamer
Target specificity of a diagnostic tool or delivery of therapeutic drug to its site of
action is the foremost hurdle in personalized medicine [5]. Aptamers, being merely
short stretches of single-strand nucleic acids with their characteristic 3D structures,
are capable of recognizing corresponding targets specifically and have become one
of the most promising tools to be used in personalized medicine [6–8]. Systematic
evolution of ligands by exponential enrichment (SELEX) is the method for aptamers
selection from pools of oligonucleotides with random or tailored DNA/RNA libraries
[9]. Till date aptamers have been selected for a vast range of targets, including metal
ions, small molecules, peptides and proteins, nucleotides, nucleic acids, targets inside
cells, and on surface of cells demonstrating excellent affinity and high specificity [10].
Aptamer–target interactions involve binding via hydrogen bonds, electrostatic and
hydrophobic interactions, stacking of the aromatic rings, and weak van der Waals
forces. These molecular interactions and forces impart to aptamers the properties
such as high binding affinity (nanomolar to picomolar range dissociation constants
(Kds) and selectivity to their cognate target molecules [11, 12]. Given their binding
properties, aptamers are often compared with antibodies; however, aptamers offer
notable advantages over antibodies and have been proposed as an alternative to antibodies for research, as well as for diagnostic and therapeutic applications (Fig. 7.1)
[13]. Advantages include the following:
1. Owing to their small size, aptamers can penetrate tissues efficiently and are
rapidly cleared from the circulation (an advantage for imaging applications) [14].
2. Chemically optimized aptamers are non-immunogenic when delivered systemically and studies have shown that they do not elicit an immune reaction even after
repeated injections. This is a considerable advantage over protein-based drugs
and antibodies, which can be immunogenic and require optimization prior to use
in humans [15].
M. Irfan et al.
order to make suitable medical decisions. In the same way, therapeutic methods for
disease treatment need to shift from broad spectrum medications toward the use of
more tailored drugs personalized to each patient [3]. Out of numerous approaches
for meeting these demands, the use of DNA aptamers is a handy tool, whose progress
matches that of personalized medicine [4]. In this chapter we will decipher the potential of aptamers in personalized medicine at different levels right starting from primitive scale, the hurdles, their advantages and disadvantages, the examples which are
successfully integrated in personalized medicines, and the gaps which are still under
consideration by the scientific community. Aptamers alone or in combination such
as aptamer chimeras and aptamer-decorated multimodal nanosystems make them a
robust tool for targeting and delivery of various therapeutic systems. At the end, we
will present a brief future perspective.
7.1.1 Advantages of Aptamer
Target specificity of a diagnostic tool or delivery of therapeutic drug to its site of
action is the foremost hurdle in personalized medicine [5]. Aptamers, being merely
short stretches of single-strand nucleic acids with their characteristic 3D structures,
are capable of recognizing corresponding targets specifically and have become one
of the most promising tools to be used in personalized medicine [6–8]. Systematic
evolution of ligands by exponential enrichment (SELEX) is the method for aptamers
selection from pools of oligonucleotides with random or tailored DNA/RNA libraries
[9]. Till date aptamers have been selected for a vast range of targets, including metal
ions, small molecules, peptides and proteins, nucleotides, nucleic acids, targets inside
cells, and on surface of cells demonstrating excellent affinity and high specificity [10].
Aptamer–target interactions involve binding via hydrogen bonds, electrostatic and
hydrophobic interactions, stacking of the aromatic rings, and weak van der Waals
forces. These molecular interactions and forces impart to aptamers the properties
such as high binding affinity (nanomolar to picomolar range dissociation constants
(Kds) and selectivity to their cognate target molecules [11, 12]. Given their binding
properties, aptamers are often compared with antibodies; however, aptamers offer
notable advantages over antibodies and have been proposed as an alternative to antibodies for research, as well as for diagnostic and therapeutic applications (Fig. 7.1)
[13]. Advantages include the following:
1. Owing to their small size, aptamers can penetrate tissues efficiently and are
rapidly cleared from the circulation (an advantage for imaging applications) [14].
2. Chemically optimized aptamers are non-immunogenic when delivered systemically and studies have shown that they do not elicit an immune reaction even after
repeated injections. This is a considerable advantage over protein-based drugs
and antibodies, which can be immunogenic and require optimization prior to use
in humans [15].