Carbon nanomaterials were usually exploited as nanocarriers in an electrochemical immunosensor but rarely acted as redox nanoprobes. Herein, our motivation is to adequately utilize the inner redox ...activity of fullerene (C60) to obtain a new type of redox nanoprobe based on a hydrophilic C60 nanomaterial. First, C60 nanoparticles (C60NPs) were prepared by phase-transfer method and functionalized with amino-terminated polyamidoamine (PAMAM) to obtain the PAMAM decorated C60NPs (PAMAM-C60NPs) which have better hydrophilicity compared to that of unmodified C60NPs and possesses abundant amine groups for further modification. Following that, gold nanoparticles (nano-Au) were absorbed on the PAMAM-C60NPs surface, and the resultant Au-PAMAM-C60NPs were employed as a new type of redox nanoprobe and nanocarrier to label detection antibodies (Ab2). Doping control has become the biggest problem facing international sport. Erythropoietin (EPO) as a blood doping agent has been a hotspot in doping control. After sandwich-type immunoreaction between EPO (as a model) and Ab2-labeled Au-PAMAM-C60NPs, the resultant immunosensor was further incubated with a drop of tetraoctylammonium bromide (TOAB) which acts as booster to arouse the inner redox activity of Au-PAMAM-C60NPs, thus a pair of reversible redox peaks is observed. As a result, the proposed immunosensor shows a wide linear range and a relatively low detection limit for EPO. This strategy paves a new avenue for exploring the redox nanoprobe based on carbon nanomaterials in the electrochemical biosensor field.
It is of great importance to develop biosensing methods for the sensitive and selective analysis of biomarkers at very low levels in biological samples. Using a new target-induced activation of the ...DNA polymerase activity for recycling amplification cascades, we describe an aptamer-based method for highly sensitive detection of platelet-derived growth factor BB (PDGF-BB) in human serums. The polymerase activity is initially inhibited by the binding of the polymerase to the enzyme aptamer sequence. PDGF-BB associates with and switches a PDGF-BB binding aptamer to trigger the release of an active polymerase, which further initiates the simultaneous recycling of the target PDGF-BB molecules and the enzyme aptamer sequence for the subsequent displacement of the fluorescently quenched probes to recover the fluorescence. Due to two recycling cascades, substantial fluorescence magnification is obtained for the highly sensitive detection of PDGF-BB with a low detection limit of 5.1 pM. Moreover, the potential applicability of this method for real samples was verified by determining PDGF-BB in diluted human serums, relying on the excellent specificity and selectivity of the aptamer. The demonstration of the PDGF-BB assay method here thus can be expanded for the construction of diverse sensing platforms for detecting different trace biomarkers with the integration of an elaborate design of the aptamer probes.
A voltammetric biosensor for lead(II) (Pb
2+
) is described that is based on signal amplification by using an ion-dependent split DNAzyme and template-free DNA extension reaction. The Pb
2+
...-dependent split DNAzyme was assembled on gold nanoparticles (Au@Fe
3
O
4
), and this nanoprobe then was exposed to Pb
2+
which causes the split-off of DNAzymes to release primers containing 3′-OH groups (S
1
and S
2
). The template-free DNA extension reaction triggers the generation of long ssDNA nanotails, which then can bind the free redox probe N,N′-bis(2-(trimethylammonium iodide)propylene)perylene-3,4,9,10-tetracarboxyldiimide (PDA
+
) via electrostatic adsorption. Hence, the concentration of PDA
+
in solution is reduced. Therefore, less free PDA
+
can be immobilized on a glassy carbon electrode modified with electrodeposited gold nanoparticles (depAu) to produce an electrochemical signal, typically measured at ∼0.38 V (
vs
. SCE) for quantitation of Pb
2+
. The use of a Pb
2+
-dependent split DNAzyme avoids the usage of a proteinic enzyme. It also increases the sensitivity of the sensor which has a lower detection limit of 30 pM of Pb
2+
.
Graphical abstract
Novel electrochemical biosensor based on the amplification of ion-dependent split DNAzyme and template-free DNA extension reaction for trace detection of Pb
2+
.
A signal on an electrochemiluminescence (ECL) biosensor using β-cyclodextrin (CD) functionalized graphitic carbon nitride (g-C3N4) as the luminophore was constructed for sensitive organophosphate ...pesticides (OPs) detection based on the enzyme inhibition of OPs, showing that the consumption of coreactant triethylamine (Et3N) decreased with a lessening of the acetic acid (HAc) in situ generated by enzymatic reaction.
The detection and quantification of microRNA (miRNA) plays essential roles in clinical and biomedical research. Yet, it is of major challenge to sense miRNA with high degree of selectivity and ...sensitivity due to its unique characteristics of short length, similarity of sequence among family members and low abundance. Here, with the design of a new hairpin/DNA ring ternary probe, we describe the development of a rolling circle amplification (RCA) method for sensitively and selectively sensing miRNA from cancer cells. The target miRNA binds the hairpin/DNA ring probes through toehold-mediated strand displacement (TSD) to form the ternary structures, in which the bound miRNA and DNA ring are respectively used as the primer and template to realize RCA, leading to the generation of many repeated metal ion-dependent DNAzyme sequences. The fluorescently quenched hairpin signal probes can be cyclically cleaved by these DNAzyme sequences with co-existence of the corresponding metal ions in buffer to show drastically enhanced fluorescence recovery for highly sensitive sensing of miRNA in the range between 10 fM and 10 nM with a detection limit of 1.51 fM. Besides, owing to the high base variation discrimination ability of TSD, selective detection of the target miRNA among the corresponding family members can be achieved by this method. Moreover, such a method can also be employed to differentiate miRNA expression variations in cancer cells for screening potential therapeutic drugs.
Display omitted
•A new hairpin/DNA ring ternary probe enables ligation-free initiation of RCA.•The coupling of RCA with DNAzyme recycling leads to drastic signal amplification.•This method can achieve highly sensitive and selective discrimination of microRNAs.
Despite the various synthesis approachs to obtain luminous carbon dots (CDs), it is still quite challenging to construct the efficient electrochemiluminescence (ECL) owing to their low ECL reactivity ...and easy agglomeration. Herein, an efficient and concise ECL system was skillfully constructed by taking advantage of the nitrogen and sulfur co-doped CDs (N,S-CDs) with surfaces rich in hydrazide groups as luminophors to emit intense ECL, and metal-organic framework (MOF) as the matrix to confine CDs in its nanospace. Surprisingly, the proposed CDs assembled MOF (CDs/ZIF-8) enhanced anodic ECL signal up to 250% of pure CDs under the exogenous coreactant-free condition. As a proof of concept, the highly sensitive detection of uric acid (UA) was realized by the constructed ECL platform with a low detection limit of 3.52 nmol/L ranging from 10 nmol/L to 50 µmol/L. This work expanded ideas for the application of pore confinement effect, and provided references for the detection of disease biomarkers of gout and hyperuricemia.
Display omitted
Herein, an efficient ECL nanoluminophor of the CDs assembled MOF was skillfully prepared by taking advantage of the nitrogen and sulfur co-doped CDs (N,S-CDs) with surfaces rich in hydrazide groups as luminophors and MOF as matrix. Due to the pore confinement-enhanced ECL, the anodic ECL signal rose up to 250% of the pure CDs under the exogenous coreactant-free condition.
A chloro 3,7,12,17-tetramethyl-8,13-divinylporphyrin-2,18-dipropanoato (2−)iron(III)/multi-walled carbon nanotubes (Fe(III)P/MWCNTs) composites and a modified glassy carbon electrode (GCE) was ...fabricated and successfully used for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and nitrite (NO
2
−). Fe(III)P/MWCNTs composites were characterized by ultraviolet–visible absorption spectroscopy (UV–vis) and scanning electron microscopy (SEM), and the results revealed a pair of direct redox peaks from the Fe
III/Fe
II couple. Moreover, the combination of Fe(III)P and MWCNTs endowed the electrode with a large surface area, good biological compatibility and stability and high selectivity and sensitivity. The linear calibration plots for AA, DA and UA were obtained over the range of 14.00
μM to 2.50
mM, 0.70
μM to 3.60
mM and 5.80
μM to 1.30
mM with detection limits of 3.00
μM, 0.09
μM and 0.30
μM, respectively. Two linear calibrations for NO
2
− were obtained over ranges of 1.00
μM to 0.60
mM and 0.60
mM to 1.60
mM with detection limits of 0.50
μM. In addition, the modified electrode was successfully applied for the determination of analytes in urine and serum samples using the standard adding method with satisfactory results.
In this work, we found that polyethyleneimine (PEI), a widely applied organic high-molecular polymer, could act as a new co-reactant to obviously improve the electrochemiluminescence (ECL) of ...S2O82−-O2 system. And owing to its abundant amine groups in the polymeric structure, PEI was further used to covalently crosslink with massive L-cysteine (L-Cys), an effective co-reactant of S2O82−-O2 ECL system, to obtain a new co-reactive high-molecular polymer (PEI-L-Cys) with higher co-reaction efficiency. As loading platform, hierarchically branched Au/Pd dendrimers (Au/Pd DRs G2) were prepared to immoblize the obtained PEI-L-Cys, detection antibody, and bolocking reagent glucose oxidase (GOD). With the existence of target carcinoembryonicantigen (CEA), an ECL immunosensor was constructed through the sandwiched immunoreaction between the capture antibody on the electrode and the bioconjugate based on Au/Pd DRs G2. Besides the high enhancement of PEI-L-Cys, the ECL signal was also greatly increased by the dual catalysis to generate O2 in situ around the electrode induced by the synergistic effect of GOD and Au/Pd DRs G2 in presence with D-glucose. Especially, due to the special hierarchically branched bimetallic structure, the Au/Pd DRs G2 had more excellent catalytic effect to H2O2 decomposition in this process. As a result, the proposed ECL immunosensor realized the ultrasensitive detection of CEA, which could provide meaningful reference to the prevention and treatment of related disease.
Display omitted
•PEI was used as a new co-reactant to obviously improve the ECL of S2O82−-O2 system.•The prepared high-molecular polymer PEI-L-Cys had more outstanding co-reactive efficiency.•The dual catalysis to generate O2 in situ induced by GOD and Au/Pd DRs G2 enhanced the sensitivity.•The immunosensor realized the measurement of CEA with ultra-sensitivity.
Photoelectrochemical (PEC) assay with low background, simple instrumentation and high sensitivity has deemed as one of the most potential strategies to simultaneous multi-component detection. How to ...distinguish photocurrent changes caused by various targets on a single sensing platform thus becomes the key issue to be resolved. Herein, we innovatively proposed a multiplex PEC biosensor based on wavelength distinguishable signal quenching and enhancing toward photoactive material 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) for simultaneous assay of dual metal ions. Briefly, S1 and S2 ssDNA containing sensitizer methylene blue and quencher ferrocene (termed as MB-S1 and Fc-S2), respectively, were first generated through target Pb2+ and Mg2+-induced DNAzyme-assisted target recycling, which thereafter were modified on PTCDA sensing platform specifically via host-guest recognition with β-cyclodextrin (β-CD). Interestingly, the sensitizer MB could enhance photocurrent of PTCDA under the excitation wavelength of 623 nm and 590 nm, respectively, while the quencher Fc just quencher the photocurrent of PTCDA under the excitation wavelength of 590 nm, thereby achieving wavelength distinguishable signal quenching and enhancing toward photoactive material PTCDA for simultaneous assay of dual metal ions. As a result, the conceived biosensor for Mg2+ and Pb2+ detection realized high sensitivity with detection limit of 0.3 pM and 0.3 nM, respectively. The proposed strategy not only for the first time achieved the discrimination of varied PEC signal caused by two targets with usage of sole photoelectric material, but also realized the simultaneous multiplex assay on a single sensing platform, providing a new way for constructing effective and sensitive PEC biosensor for multi-component detection.
•A multiplex PEC biosensor based on wavelength distinguishable signal quenching and enhancing to PTCDA was proposed for dual metal ions assay.•The proposed strategy achieved the discrimination of varied PEC signal so as to realize the simultaneous multiplex assay.•The target Pb2+ and Mg2+-induced DNAzyme-assisted target recycling could significantly improve the sensitivity of proposed strategy.
Based on specific target-induced cleavage of peptide, a sensitive electrochemical biosensor for MMP-2 was constructed by using Pt/Pd/mhCeO2NS as nanocarriers and electrocatalysts.
Display omitted
•A ...sensitive MMP-2 biosensor was constructed based on specific cleavage of peptide.•Pt/Pd/mhCeO2NS was used as nanocarriers and electrocatalysts for the biosensor.•The transduction of peptide cleavage events was combined with the electrocatalysts.•The catalytic capacity of Pt/Pd/mhCeO2NS was optimal to the signal amplification.•The electrochemical analytical performance was significantly improved and enhanced.
A facile electrochemical biosensor for matrix metalloproteinase 2 (MMP-2) was developed based on the target induced cleavage of a special designed peptide by using bimetallic Pt and Pd nanoparticles encapsulated mesoporous-hollow ceria nanospheres (Pt/Pd/mhCeO2NS) as nanocarriers and electrocatalysts. Briefly, employing l-lysine as bridge and linker, Pt/Pd/mhCeO2NS simply synthesized was used as a loading platform to immobilize electroactive thionine (Thi) and streptavidin (SA), resulting in the final formation of SA/Thi/Pt/Pd/mhCeO2NS nanoprobes. A specific biotin-labeled peptide (biotin-GPLGVRGKGGC, P1) acted as a molecular recognition element was firstly anchored on the Au nanoparticles modified electrode surface. In the presence of MMP-2, the P1 was specifically cleaved into two fragments at a certain site between G and V, while SA/Thi/Pt/Pd/mhCeO2NS nanoprobes were bonded onto the resulting electrode surface through the inherent interaction between streptavidin and biotin derived from uncleaved P1. In the proposed protocol, the electrochemical signal amplification was achieved by the effectively catalysis of Pt/Pd/mhCeO2NS to the decomposition of H2O2. This could result in the significant enhancement of the electrochemical response for determining MMP-2 in the range of 0.1pgmL−1–10ngmL−1 with a detection limit of 0.078pgmL−1. The present work demonstrated that the combination of the direct transduction of peptide cleavage events with the efficient Pt/Pd/mhCeO2NS catalysis method, providing a promising effective strategy for MMP-2 detection.
