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Y. Cheng and H. Jin
single-strand oligonucleotide sequences with high specificity and affinity for target
substances screened from random oligonucleotide libraries based on SELEX protocol
as follows.
Firstly, a random oligonucleotide library was synthesized artificially, with a total
length of 70–100 nt and a random sequence of 20–40 nt in the middle. After incubation with target substances for a particular time, the nucleic acid-target complex will
be formed. Certain methods are used to remove library sequences that are not bound
to the target. The complex can thermally be dissociated to obtain the target-bound
sequence, which is used as a template of PCR amplification for the preparation of the
next enriched library. After 8–20 rounds of continuous screening, oligonucleotide
sequences with high specificity and high affinity to the target, namely aptamers, can
be obtained [2, 3]. For RNA SELEX [2], a library of single-stranded RNA molecules
is usually prepared by in vitro transcription of double-stranded DNA templates using
recombinant T7 RNA polymerase. For DNA SELEX [4], a library of single-stranded
DNA molecules is usually prepared by strand separation of double-stranded PCR
products.
Researchers have successfully identified high-affinity aptamers for a variety of
medical targets, including cytokines, proteases, kinases, cell-surface receptors, and
cellular adhesion molecules [1]. Since the aptamer is produced entirely in vitro,
its physical and chemical properties can be adjusted according to its application
requirements. Aptamers are currently being widely developed and used as tools for
diagnosis, treatment, biosensor, and detection of basic cellular processes [5]. The
broad-spectrum application of aptamers stems from their versatility, high selectivity,
superior sensitivity, and ease of screening and production.
Hormones are any of a class of signaling molecules produced by glands in multicellular organisms, and they have various chemical structures which are mainly
divided into three categories: eicosanoids, steroids, and amino acid derivatives. These
molecules are transported through the circulatory system to target distant organs
to regulate physiological regulation and behavioral activities between organs and
tissues. Theoretically, hormones affect distant cells by binding to specific receptor
proteins in target cells, resulting in changes in cell function. When the hormone
binds to the receptor, it activates a signaling pathway, which leads to cell-type-specific
responses, including rapid non-genomic effects or slower genomic reactions in which
hormones activate gene transcription through their receptors, thereby increasing the
expression of target proteins.
Aptameric ligand-binding sites are highly modular and can be combined with
other functional nucleic acids or non-nucleic acid chemical entities or even linked
to a wide variety of carriers and surfaces. Because aptamers are generated entirely
in vitro, it is possible to tailor their physicochemical properties to the requirements
of their applications. Furthermore, it is straightforward to equip aptamers with additional chemical functions that outfit them for various applications in biomedicine,
nanotechnology, and cell biology [6]. These qualities enable aptamers as highly
versatile capture agents for developing various biosensors and sensor arrays. In addition to high affinity and specificity, aptamers have more advantages than antibodies,
embracing production automation, excellent stability, desirable biocompatibility, and
Y. Cheng and H. Jin
single-strand oligonucleotide sequences with high specificity and affinity for target
substances screened from random oligonucleotide libraries based on SELEX protocol
as follows.
Firstly, a random oligonucleotide library was synthesized artificially, with a total
length of 70–100 nt and a random sequence of 20–40 nt in the middle. After incubation with target substances for a particular time, the nucleic acid-target complex will
be formed. Certain methods are used to remove library sequences that are not bound
to the target. The complex can thermally be dissociated to obtain the target-bound
sequence, which is used as a template of PCR amplification for the preparation of the
next enriched library. After 8–20 rounds of continuous screening, oligonucleotide
sequences with high specificity and high affinity to the target, namely aptamers, can
be obtained [2, 3]. For RNA SELEX [2], a library of single-stranded RNA molecules
is usually prepared by in vitro transcription of double-stranded DNA templates using
recombinant T7 RNA polymerase. For DNA SELEX [4], a library of single-stranded
DNA molecules is usually prepared by strand separation of double-stranded PCR
products.
Researchers have successfully identified high-affinity aptamers for a variety of
medical targets, including cytokines, proteases, kinases, cell-surface receptors, and
cellular adhesion molecules [1]. Since the aptamer is produced entirely in vitro,
its physical and chemical properties can be adjusted according to its application
requirements. Aptamers are currently being widely developed and used as tools for
diagnosis, treatment, biosensor, and detection of basic cellular processes [5]. The
broad-spectrum application of aptamers stems from their versatility, high selectivity,
superior sensitivity, and ease of screening and production.
Hormones are any of a class of signaling molecules produced by glands in multicellular organisms, and they have various chemical structures which are mainly
divided into three categories: eicosanoids, steroids, and amino acid derivatives. These
molecules are transported through the circulatory system to target distant organs
to regulate physiological regulation and behavioral activities between organs and
tissues. Theoretically, hormones affect distant cells by binding to specific receptor
proteins in target cells, resulting in changes in cell function. When the hormone
binds to the receptor, it activates a signaling pathway, which leads to cell-type-specific
responses, including rapid non-genomic effects or slower genomic reactions in which
hormones activate gene transcription through their receptors, thereby increasing the
expression of target proteins.
Aptameric ligand-binding sites are highly modular and can be combined with
other functional nucleic acids or non-nucleic acid chemical entities or even linked
to a wide variety of carriers and surfaces. Because aptamers are generated entirely
in vitro, it is possible to tailor their physicochemical properties to the requirements
of their applications. Furthermore, it is straightforward to equip aptamers with additional chemical functions that outfit them for various applications in biomedicine,
nanotechnology, and cell biology [6]. These qualities enable aptamers as highly
versatile capture agents for developing various biosensors and sensor arrays. In addition to high affinity and specificity, aptamers have more advantages than antibodies,
embracing production automation, excellent stability, desirable biocompatibility, and