As an early-stage tumor biomarker, microRNA (miRNA) has clinical application potential and its sensitive and accurate detection is significant for early tumor diagnosis. In this study, a photoelectrochemical (PEC) biosensing platform was fabricated for ultrasensitive miRNA-141 detection, which is based on a photocurrent polarity-switchable system using CdS quantum dots (QDs) in the presence of a 5,10,15,20-tetrakis (4-aminophenyl)-21H,23H-porphine (Tph-2H)-coated glassy carbon electrode (GCE). As an excellent photoactive material, Tph-2H has a narrow band gap that effectively gathers photoelectrons under visible light irradiation and improves the transfer ability of photogenerated electrons. Further, the detection sensitivity of miRNA-141 could be significantly improved by combining an enzyme-assisted recycle amplification reaction and a magnetic bead-based separation strategy. The proposed photocurrent polarity-switchable PEC biosensor could efficiently eliminate the false-positive or false-negative signals and achieve a wide linear response range from 1 fM to 1 nM with a low detection limit of 0.33 fM for miRNA-141, providing a potentially alternative solution for detecting other biomarkers in bioanalysis and clinical diagnosis.
Five
high-nuclear lanthanide (Ln) substituted heteropolytungstates
[H2N(CH3)2]16Na9LnH10{[W16Ln10(H2O)38O50][B-α-SeW9O33]8}·56H2O [Ln = LaIII (1), CeIII (2)], [H2N(CH3)2]22Na4H12{[W18Ln10(H2O)34O56][B-α-SeW9O33]8}·80H2O [Ln = LaIII (3), CeIII (4)], and Na4[H2N(CH3)2]18H21[Nd(H2O)7][W16Nd10O50(H2O)34(B-α-AsW9O33)8]·60H2O (5) were prepared
by reaction of Na2WO4·2H2O and
Ln(NO3)3·6H2O in the presence
of dimethylamine hydrochloride (DMAHC) and Na2SeO3 or NaAsO2 in an aqueous medium. The octameric polyoxoanions
{[W16Ln10(H2O)38O50][B-α-SeW9O33]8}38– in 1 and 2 are assembled
from eight [B-α-SeW9O33]8– building blocks linked by 16 extra bridging WVI centers
and ten LnIII cations, whereas the octameric polyoxoanions
{[W18Ln10(H2O)34O56][B-α-SeW9O33]8}38– in 3 and 4 are constructed
from eight [B-α-SeW9O33]8– building blocks joined by 18 additional bridging WVI centers
and ten LnIII cations [Ln = LaIII (3), CeIII (4)]. The octameric polyoxoanion
[W16Nd10O50(H2O)34(B-α-AsW9O33)8]40– in 5 is constituted by eight [B-α-AsW9O33]9– building blocks connected
by 16 extra bridging WVI centers and ten NdIII cations. It should be noted that neighboring {[W16Nd10(H2O)38O50][B-α-AsW9O33]8}46– polyoxoanions
in 5 are further polymerized by two W–O–Nd–O–W
linkers into a 1-D chain-like alignment. The thermolysis processes
of 1, 4, and 5 were investigated
by variable-temperature IR spectra, coloration changes, and variable-temperature
PXRD patterns. The solid-state NIR luminescence properties of 5 were systematically studied at room temperature.
Four acetate-decorated tri-Ln-substituted trimeric antimonotungstates (AMTs) Na 17 {(WO 4 )[Ln(H 2 O)(Ac)(B-α-SbW 9 O 31 (OH) 2 )] 3 }•50H 2 O [Ln = Eu 3+ (1), Dy 3+ (2), Ho 3+ (3), or Gd 3+ (4)] were isolated by reaction of Na 9 [B-α-SbW 9 O 33 ]• 19.5H 2 O, Na 2 WO 4 •2H 2 O, and Ln(NO 3 )•6H 2 O in a HAc/NaAc buffer solution. Interestingly, a tetrahedral {WO 4 } group plays a significant structure-directing template role in the formation of their polyoxoanions. With regard to luminescence properties, with a change in the excitation wavelength, it is available to switch emission colors from orange to red for 1, blue to green for 2, and blue to yellow for 3. Under the O → W LMCT excitation, energy transfer from AMT fragments to Eu 3+ , Dy 3+ , and Ho 3+ ions occurs because Ln 3+ ions can absorb energy from O → W LMCT emission of AMT segments. The temperature-dependent luminescence behaviors (25−720 °C) of 1 together with auxiliary emitting photographs illustrate that the growing emission in the temperature range of 25−100 °C results from the loss of lattice water molecules, the decline of emission between 100 and 320 °C may occur because crystals become amorphous powders, the slow emission decay (220−320 °C) is due to the case that the emission enhancement derived from the removal of water ligands on Eu 3+ ions in some degree compensates for the decline of emission intensity, the sharp decrease in emission (320−520 °C) may result from the change in the coordinate environment of Eu 3+ ions, and the weak recovery of emission (620−720 °C) may be ascribed to the formation of new phase Na 0.5 Eu 0.5 WO 4 . This work lays a significant foundation for preparing novel POM-based luminescent materials.
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