Topics in Current Chemistry (2020) 378:13
1 3
preferred to electrostatic interaction due to the high specific binding. Taking this
fact into account, the manipulation of click-reactions, phosphoramidate bond formation, thiolated DNA, and 4-pyridyldithiol-derivatized peptide nucleic acid (PNA)
are taken into consideration in the fabrication of DNA hybridization biosensors [23,
100–102].
According to Robinson et al., many possibilities are derived by exploiting the
chemistry of gold–sulfur (Au–S) complexes [23]. These authors reported the synthesis and characterization of Co–Au and Fe 3 O 4 @Au core–shell nanoparticles by
reducing a gold (III) salt in a dispersion of such MNPs. The presence of the Au shell
leads the functionalization of nanoparticles with thiolated single-stranded DNA
(ssDNA) and subsequently its use for hybridization processes. The Cu(I)-catalyzed
azide-alkyne cycloaddition (CuAAC) “click” reaction has also been employed to
achieve the attachment of DNA to ferrite nanoparticles. For example, the research
group of Sreenivasulu have studied the self-assembly of multiferroic nanocomposites using DNA–DNA hybridization [100]. In this case, the azide-alkyne cycloaddition mediates the interaction between azide-functionalized barium titanate or nickel
ferrite nanoparticles and alkyne-modified single-stranded oligonucleotide (ssODN).
Such complex hybridized nanocomposites allow the combination of ferroelectric
and ferromagnetic phases to study the mechanical strain of the related system. Along
with the above-mentioned approaches, the covalent conjugation of DNA fragments
to MNPs by forming a carbodiimide-mediated phosphoramidate bond is considered
to be another useful route for developing hybridization biosensors. For example, Zhu
et al. have investigated the application of such nanocomposites for electrochemical
DNA hybridization [101], taking advantage of ssDNA immobilization on MNPs and
using zinc sulfide nanoparticles as the oligonucleotide label.
In most of the above-mentioned reports, oligonucleotides were used as conventional sequence-specific fragments. However, although Watson–Crick base pairing is
remarkably specific, the mismatch discrimination of the ODN recognizer is not sufficiently selective and, in addition, it is susceptible to hydrolyzation by endogenous
nucleases and proteases. To overcome such limitations during biomedical applications, the strategy of utilizing 4-pyridyldithiol-derivatized PNA as the sequence-specific gene recognizer can be considered. As a DNA analog, PNA comprises a polyamine instead of a sugar-phosphate backbone; as such, it is capable of binding DNA
oligomers following Watson–Crick base pairing rules to form a PNA–DNA duplex
that is significantly more stable than the corresponding DNA–DNA duplex. Wang
et al. studied the use of PNA–MNPs biocomposites in gene recognition using surface-enhanced Raman scattering [102] and reported that PNA-modified MNPs can
be easily prepared via a thiol-disulfide exchange reaction followed by the hybridization protocol.
While Coulombic interactions of DNA with charged surfaces show a lack of
specificity, the avidin–biotin complex is considered to be one of the most specific
and stable noncovalent interactions. Since conjugations of biotin and its binding proteins (avidin and analogs such as streptavidin and neutravidin) are stable and highly
specific and do not involve unstable intermediates, they could serve as a promising tool in biomedical and nanotechnological applications. Avidin is a basic tetrameric glycoprotein composed of four identical subunits that binds to biotin with
28
Reprinted from the journal
1 3
preferred to electrostatic interaction due to the high specific binding. Taking this
fact into account, the manipulation of click-reactions, phosphoramidate bond formation, thiolated DNA, and 4-pyridyldithiol-derivatized peptide nucleic acid (PNA)
are taken into consideration in the fabrication of DNA hybridization biosensors [23,
100–102].
According to Robinson et al., many possibilities are derived by exploiting the
chemistry of gold–sulfur (Au–S) complexes [23]. These authors reported the synthesis and characterization of Co–Au and Fe 3 O 4 @Au core–shell nanoparticles by
reducing a gold (III) salt in a dispersion of such MNPs. The presence of the Au shell
leads the functionalization of nanoparticles with thiolated single-stranded DNA
(ssDNA) and subsequently its use for hybridization processes. The Cu(I)-catalyzed
azide-alkyne cycloaddition (CuAAC) “click” reaction has also been employed to
achieve the attachment of DNA to ferrite nanoparticles. For example, the research
group of Sreenivasulu have studied the self-assembly of multiferroic nanocomposites using DNA–DNA hybridization [100]. In this case, the azide-alkyne cycloaddition mediates the interaction between azide-functionalized barium titanate or nickel
ferrite nanoparticles and alkyne-modified single-stranded oligonucleotide (ssODN).
Such complex hybridized nanocomposites allow the combination of ferroelectric
and ferromagnetic phases to study the mechanical strain of the related system. Along
with the above-mentioned approaches, the covalent conjugation of DNA fragments
to MNPs by forming a carbodiimide-mediated phosphoramidate bond is considered
to be another useful route for developing hybridization biosensors. For example, Zhu
et al. have investigated the application of such nanocomposites for electrochemical
DNA hybridization [101], taking advantage of ssDNA immobilization on MNPs and
using zinc sulfide nanoparticles as the oligonucleotide label.
In most of the above-mentioned reports, oligonucleotides were used as conventional sequence-specific fragments. However, although Watson–Crick base pairing is
remarkably specific, the mismatch discrimination of the ODN recognizer is not sufficiently selective and, in addition, it is susceptible to hydrolyzation by endogenous
nucleases and proteases. To overcome such limitations during biomedical applications, the strategy of utilizing 4-pyridyldithiol-derivatized PNA as the sequence-specific gene recognizer can be considered. As a DNA analog, PNA comprises a polyamine instead of a sugar-phosphate backbone; as such, it is capable of binding DNA
oligomers following Watson–Crick base pairing rules to form a PNA–DNA duplex
that is significantly more stable than the corresponding DNA–DNA duplex. Wang
et al. studied the use of PNA–MNPs biocomposites in gene recognition using surface-enhanced Raman scattering [102] and reported that PNA-modified MNPs can
be easily prepared via a thiol-disulfide exchange reaction followed by the hybridization protocol.
While Coulombic interactions of DNA with charged surfaces show a lack of
specificity, the avidin–biotin complex is considered to be one of the most specific
and stable noncovalent interactions. Since conjugations of biotin and its binding proteins (avidin and analogs such as streptavidin and neutravidin) are stable and highly
specific and do not involve unstable intermediates, they could serve as a promising tool in biomedical and nanotechnological applications. Avidin is a basic tetrameric glycoprotein composed of four identical subunits that binds to biotin with
28
Reprinted from the journal