Topics in Current Chemistry (2020) 378:28
1 3
DNA detection. Guided by density functional theory (DFT) calculations, Fu et al.
[22] developed plasmonic Au-modified, bulk/surface defect-engineered TiO 2 nanotube photonic crystals (Au/bsDE-TiO 2 NTPCs) for the in vivo near-infrared PEC
aptasensing of tetracycline (TET). Bulk defects were introduced into the TiO 2 lattice by high-temperature annealing in a reducing atmosphere or vacuum, and then
Au NPs were sputtered onto the defective TiO 2 surface. The PEC response of the
resulting Au/bsDE-TiO 2 NTPCs nanocomposite extended into the near-infrared
region (900 nm). The photocurrent of the proposed PEC system increased significantly when TET was captured by an aptamer on the nanocomposite. A thin (0.1
mm diameter) Ti wire modified with Au/bsDE-TiO 2 NTPCs was then successfully
used to monitor the TET in a mouse tail in vivo under near-infrared (NIR) light.
Speaking of NIR PEC detection, Qiu et al. [33] reported the application of
core–shell NaYF 4 :Yb,Tm@TiO 2 upconversion microrods for the detection of CEA
(carcinoembryonic antigen). The Yb
3+
ions acted as a photosensitizer, absorbing
the near-infrared light at 980 nm and generating two emission peaks at 453 and
479 nm. At the same time, the doped Tm
3+
emitted UV light (with emission peaks
at 291, 348, and 363 nm) that overlapped closely with the absorption peak of TiO 2 .
After modifying the the NaYF 4 :Yb,Tm with TiO 2 , the peak intensity of the photoluminescence of the resulting system in the UV region markedly decreased. The
proposed PEC system exhibited a good response to the guanine bases generated
during CEA aptasensing. Due to its low phototoxicity in biological systems, this
NaYF 4 :Yb,Tm@TiO 2 -based biosensor should expand the application of upconversion materials to PEC detection.
3 Applications of TiO 2 Nanomaterials in Electrochemiluminescence
Biosensing
Recently, TiO 2 nanomaterials and their composites have drawn considerable interest from those working in the field of ECL biosensing, given the biocompatibility,
large surface area, and unique ECL properties of these materials. TiO 2 nanomaterials can be applied in a variety of roles in ECL biosensors, including as a matrix for
biomolecules, as an ECL luminophore, and as a catalyst for the ECL reaction. In this
section, ECL bioassays based on TiO 2 nanomaterials are explored via a number of
illustrative examples.
TiO 2 is an ideal matrix for immobilizing biomolecules on an electrode. For
instance, Dai and coauthors [20] presented a dual-signal ECL biosensor based on
TiO 2 mesocrystals and CdTe QDs for the detection of metallothioneins. A considerable amount of Ru(bpy) 3
2+
was immbolized in the porous TiO 2 mesocrystal structure through ion exchange. In addition, the presence of TiO 2 mesocrystals on the
nanocomposite surface resulted in a higher pH, thus increasing the ECL intensity
of Ru(bpy) 3
2+
. TiO 2 is able to link to metallothioneins efficiently via strong interactions with the sulfhydryl groups of metallothioneins, which blocks electron transfer and hinders the diffusion of coreactants, thus decreasing the ECL intensity of
Ru(bpy) 3
2+
. The CdTe QDs can link to the remaining SH groups of metallothioneins,
generating a cathodic ECL. Therefore, a ratiometric biosensor was constructed for
8
Reprinted from the journal
1 3
DNA detection. Guided by density functional theory (DFT) calculations, Fu et al.
[22] developed plasmonic Au-modified, bulk/surface defect-engineered TiO 2 nanotube photonic crystals (Au/bsDE-TiO 2 NTPCs) for the in vivo near-infrared PEC
aptasensing of tetracycline (TET). Bulk defects were introduced into the TiO 2 lattice by high-temperature annealing in a reducing atmosphere or vacuum, and then
Au NPs were sputtered onto the defective TiO 2 surface. The PEC response of the
resulting Au/bsDE-TiO 2 NTPCs nanocomposite extended into the near-infrared
region (900 nm). The photocurrent of the proposed PEC system increased significantly when TET was captured by an aptamer on the nanocomposite. A thin (0.1
mm diameter) Ti wire modified with Au/bsDE-TiO 2 NTPCs was then successfully
used to monitor the TET in a mouse tail in vivo under near-infrared (NIR) light.
Speaking of NIR PEC detection, Qiu et al. [33] reported the application of
core–shell NaYF 4 :Yb,Tm@TiO 2 upconversion microrods for the detection of CEA
(carcinoembryonic antigen). The Yb
3+
ions acted as a photosensitizer, absorbing
the near-infrared light at 980 nm and generating two emission peaks at 453 and
479 nm. At the same time, the doped Tm
3+
emitted UV light (with emission peaks
at 291, 348, and 363 nm) that overlapped closely with the absorption peak of TiO 2 .
After modifying the the NaYF 4 :Yb,Tm with TiO 2 , the peak intensity of the photoluminescence of the resulting system in the UV region markedly decreased. The
proposed PEC system exhibited a good response to the guanine bases generated
during CEA aptasensing. Due to its low phototoxicity in biological systems, this
NaYF 4 :Yb,Tm@TiO 2 -based biosensor should expand the application of upconversion materials to PEC detection.
3 Applications of TiO 2 Nanomaterials in Electrochemiluminescence
Biosensing
Recently, TiO 2 nanomaterials and their composites have drawn considerable interest from those working in the field of ECL biosensing, given the biocompatibility,
large surface area, and unique ECL properties of these materials. TiO 2 nanomaterials can be applied in a variety of roles in ECL biosensors, including as a matrix for
biomolecules, as an ECL luminophore, and as a catalyst for the ECL reaction. In this
section, ECL bioassays based on TiO 2 nanomaterials are explored via a number of
illustrative examples.
TiO 2 is an ideal matrix for immobilizing biomolecules on an electrode. For
instance, Dai and coauthors [20] presented a dual-signal ECL biosensor based on
TiO 2 mesocrystals and CdTe QDs for the detection of metallothioneins. A considerable amount of Ru(bpy) 3
2+
was immbolized in the porous TiO 2 mesocrystal structure through ion exchange. In addition, the presence of TiO 2 mesocrystals on the
nanocomposite surface resulted in a higher pH, thus increasing the ECL intensity
of Ru(bpy) 3
2+
. TiO 2 is able to link to metallothioneins efficiently via strong interactions with the sulfhydryl groups of metallothioneins, which blocks electron transfer and hinders the diffusion of coreactants, thus decreasing the ECL intensity of
Ru(bpy) 3
2+
. The CdTe QDs can link to the remaining SH groups of metallothioneins,
generating a cathodic ECL. Therefore, a ratiometric biosensor was constructed for
8
Reprinted from the journal