Ultrasensitive SERS Detection of Lysozyme by a Target‐Triggering Multiple Cycle Amplification Strategy Based on a Gold Substrate

An ultrasensitive surface enhanced Raman scattering (SERS) method has been designed to selectively and sensitively detect lysozyme. The gold chip as the detection substrate, the aptamer‐based target‐triggering cascade multiple cycle amplification, and gold nanoparticles (AuNPs) bio‐barcode Raman probe enhancement on the gold substrate are employed to enhance the SERS signals. The cascade amplification process consists of the nicking enzyme signaling amplification (NESA), the strand displacement amplification (SDA), and the circular‐hairpin‐assisted exponential amplification reaction (HA‐EXPAR). With the involvement of an aptamer‐based probe, two amplification reaction templates, and a Raman probe, the whole circle amplification process is triggered by the target recognition of lysozyme. The products of the upstream cycle (NESA) could act as the “DNA trigger” of the downstream cycle (SDA and circular HA‐EXPAR) to generate further signal amplification, resulting in the immobility of abundant AuNPs Raman probes on the gold substrate. “Hot spots” are produced between the Raman probe and the gold film, leading to significant SERS enhancement. This detection method exhibits excellent specificity and sensitivity towards lysozyme with a detection limit of 1.0×10^?15 M . Moreover, the practical determination of lysozyme in human serum demonstrates the feasibility of this SERS approach in the analysis of a variety of biological specimens.     

Rolling‐Circle Amplification Detection of Thrombin Using Surface‐Enhanced Raman Spectroscopy with Core‐Shell Nanoparticle Probe

An ultrasensitive surface‐enhanced Raman spectroscopy (SERS) sensor based on rolling‐circle amplification (RCA)‐increased “hot‐spot” was developed for the detection of thrombin. The sensor contains a SERS gold nanoparticle@Raman label@SiO₂ core‐shell nanoparticle probe in which the Raman reporter molecules are sandwiched between a gold nanoparticle core and a thin silica shell by a layer‐by‐layer method. Thrombin aptamer sequences were immobilized onto the magnetic beads (MBs) through hybridization with their complementary strand. In the presence of thrombin, the aptamer sequence was released; this allowed the remaining single‐stranded DNA (ssDNA) to act as primer and initiate in situ RCA reaction to produce long ssDNAs. Then, a large number of SERS probes were attached on the long ssDNA templates, causing thousands of SERS probes to be involved in each biomolecular recognition event. This SERS method achieved the detection of thrombin in the range from 1.0×10^?12 to 1.0×10^?8 M and a detection limit of 4.2×10^?13 M , and showed good performance in real serum samples.     

Multianalyte Electrochemical Biosensor Based on Aptamer‐ and Nanoparticle‐Integrated Bio‐Barcode Amplification

In the present work, a signal‐on electrochemical sensing strategy for the simultaneous detection of adenosine and thrombin is developed based on switching structures of aptamers. An Au electrode as the sensing surface is modified with two kinds of thiolated capture probes complementary to the linker DNA that contains either an adenosine aptamer or thrombin aptamer. The capture probes hybridize with their corresponding linker DNA, which has prehybridized with the reporter DNA loaded onto the gold nanoparticles (AuNPs). The AuNP contained two kinds of bio‐barcode DNA: one is complementary to the linker DNA (reporter), whereas the other is not (signal) and is tagged with different metal sulfide nanoparticles. Thus a “sandwich‐type” sensing interface is fabricated for adenosine and thrombin. With the introduction of adenosine and thrombin, the aptamer parts bind with their targets and fold to form the complex structures. As a result, the bio‐barcoded AuNPs are released into solution. The metal sulfide nanoparticles are measured by anodic stripping voltammetry (ASV), and the concentrations of adenosine and thrombin are proportional to the signal of either metal ion. With the dual amplification of the bio‐barcoded AuNP and the preconcentration of metal ions through ASV technology, detection limits as low as 6.6×10^?12 M for adenosine and 1.0×10^?12 M for thrombin are achieved. The sensor exhibits excellent selectivity and detectability in biological samples.     

One‐pot synthesis of surface‐functionalized molecularly imprinted polymer microspheres by iniferter‐induced “living” radical precipitation polymerization

This article describes for the first time the development of a new polymerization technique by introducing iniferter‐induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter‐induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant K_a and apparent maximum number N_max for the high‐affinity sites of the 2,4‐D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 10⁴ M^?1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2‐chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one‐pot synthesis of functional polymer/MIP microspheres with surface‐bound iniferter groups, which allows their direct controlled surface modification via surface‐initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010     

Ultrasensitive Electrochemiluminescence Biosensor for mRNA Based on Polymerase Assisted Signal Amplification

A novel biosensor for ultra‐trace mRNA sensing was constructed based on isothermal circular strand‐replacement polymerization (CSRP) to amplify the electrochmeiluminescence (ECL) signal by combining quantum dots (CdTe) as luminophore. After the hairpin‐like capture DNA was opened by hybridization with target mRNA, the additive primer (DNA1) was able to get access to its complementary sequence which is partially belong to the stem part and triggered a polymerization of DNA strand, leading to the release of target mRNA and another polymerization cycle. The remaining sequence of the stem part continued to hybridize with QDs labeled DNA, accomplishing ECL signal amplification. Target mRNA could be specifically assayed with a linear relationship between the signal intensity and the logarithm of concentrations of target DNA in the range of 1.0×10⁻¹⁴∼5.0×10⁻¹⁰ M, with a low detection limit of 1.4×10⁻¹⁵ M. The signal could discriminate perfect matched target mRNA from 1‐base mismatch sequence. This proposed ECL biosensor exhibited an efficient performance in serum sample, opening new opportunities for genetic target analysis in diagnostic and clinic biomedical fields.     

An Electrochemical Aptasensor for Detection of Thrombin based on Target Protein‐induced Strand Displacement

A sensitive electrochemical aptasensor for detection of thrombin based on target protein‐induced strand displacement is presented. For this proposed aptasensor, dsDNA which was prepared by the hybridization reaction of the immobilized probe ssDNA (IP) containing thiol group and thrombin aptamer base sequence was initially immobilized on the Au electrode by self‐assembling via Au? S bind, and a single DNA labeled with CdS nanoparticles (DP‐CdS) was used as a detection probe. When the so prepared dsDNA modified Au electrode was immersed into a solution containing target protein and DP‐CdS, the aptamer in the dsDNA preferred to form G‐quarter structure with the present target protein resulting that the dsDNA sequence released one single strand and returned to IP strand which consequently hybridized with DP‐CdS. After dissolving the captured CdS particles from the electrode, a mercury‐film electrode was used for electrochemical detection of these Cd²⁺ ions which offered sensitive electrochemical signal transduction. The peak current of Cd²⁺ ions had a good linear relationship with the thrombin concentration in the range of 2.3×10^?9–2.3×10^?12 mol/L and the detection limit was 4.3×10^?13 mol/L of thrombin. The detection was also specific for thrombin without being affected by the coexistence of other proteins, such as BSA and lysozyme.     

High‐Speed Living Polymerization of Polar Vinyl Monomers by Self‐Healing Silylium Catalysts

This contribution describes the development and demonstration of the ambient‐temperature, high‐speed living polymerization of polar vinyl monomers (M) with a low silylium catalyst loading (≤ 0.05 mol % relative to M). The catalyst is generated in situ by protonation of a trialkylsilyl ketene acetal (^RSKA) initiator (I) with a strong Brønsted acid. The living character of the polymerization system has been demonstrated by several key lines of evidence, including the observed linear growth of the chain length as a function of monomer conversion at a given [M]/[I] ratio, near‐precise polymer number‐average molecular weight (M_n, controlled by the [M]/[I] ratio) with narrow molecular weight distributions (MWD), absence of an induction period and chain‐termination reactions (as revealed by kinetics), readily achievable chain extension, and the successful synthesis of well‐defined block copolymers. Fundamental steps of activation, initiation, propagation, and catalyst “self‐repair” involved in this living polymerization system have been elucidated, chiefly featuring a propagation “catalysis” cycle consisting of a rate‐limiting C? C bond formation step and fast release of the silylium catalyst to the incoming monomer. Effects of acid activator, catalyst and monomer structure, and reaction temperature on polymerization characteristics have also been examined. Among the three strong acids incorporating a weakly coordinating borate or a chiral disulfonimide anion, the oxonium acid [H(Et₂O)₂]⁺[B(C₆F₅)₄]^? is the most effective activator, which spontaneously delivers the most active R₃Si⁺, reaching a high catalyst turn‐over frequency (TOF) of 6.0×10³ h^?1 for methyl methacrylate polymerization by Me₃Si⁺ or an exceptionally high TOF of 2.4×10⁵ h^?1 for n‐butyl acrylate polymerization by iBu₃Si⁺, in addition to its high (>90 %) to quantitative efficiencies and a high degree of control over M_n and MWD (1.07–1.12). An intriguing catalyst “self‐repair” feature has also been demonstrated for the current living polymerization system.     

Electrochemiluminescence of Supramolecular Nanorods and Their Application in the “On–Off–On” Detection of Copper Ions

In this work, an “on–off–on” switch system has been successfully applied through the construction of an electrochemiluminscent biosensor for copper ion (Cu²⁺) detection based on a new electrochemiluminescence (ECL) emitter of supramolecular nanorods, which was achieved through supramolecular interactions between 3,4,9,10‐perylenetetracarboxylic acid (PTCA) and aniline. The initial “signal‐on” state with strong and stable ECL emission was obtained by use of the supramolecular nanorods with a new signal amplification strategy involving a co‐reaction accelerator. In addition, ECL quencher probes (Fc‐NH₂/Cu‐Sub/nano‐Au) were fabricated by immobilizing aminoferrocene (Fc‐NH₂) on Cu‐substrate strand modified Au nanoparticles. The quencher probes were hybridized with the immobilized Cu‐enzyme strand to form Cu²⁺‐specific DNAzyme. Similarly, the “signal‐off” state was obtained by the high quenching effect of Fc‐NH₂ on the ECL of the excited‐state PTCA (¹PTCA*). As expected, the second “switch‐on” state could achieved by incubating with the target Cu²⁺, owing to the Cu²⁺‐specific DNAzyme, which was irreversibly cleaved, resulting in the release of the quencher probes from the sensor interface. Herein, on the basis of the ECL intensity changes (ΔI_ECL) before and after incubating with the target Cu²⁺, the prepared Cu²⁺‐specific DNAzyme‐based biosensor was used for the determination of Cu²⁺ concentrations with high sensitivity, excellent selectivity, and good regeneration.     

Ultrasensitive electrochemical analysis of two analytes by using an autonomous DNA machine that works in a two-cycle mode

We report a novel autonomous DNA machine for amplified electrochemical analysis of two DNAs. The DNA machine operates in a two‐cycle working mode to amplify DNA recognition events; the working mode is assisted by two different nicking endonucleases (NEases). Two bio‐barcode probes, a ZnS nanoparticle (NP)–DNA probe and a CdS NP–DNA probe, were used to trace two target DNAs. The detection system was based on a sensitive differential pulse anodic stripping voltammetry (DPASV) method for the simultaneous detection of Zn^II and Cd^II tracers, which were obtained by dissolving the two probes. Under the optimised conditions, detection limits as low as 5.6×10^?17 (3σ) and 4.1×10^?17 M (3σ) for the two target DNAs were achieved. It has been proven that the DNA machine system can simultaneously amplify two target DNAs by more than four orders of magnitude within 30 min at room temperature. In addition, in combination with an aptamer recognition strategy, the DNA machine was further used in the aptamer‐based amplification analysis of adenosine triphosphate (ATP) and lysozyme. With the amplification of the DNA machine, detection limits as low as 5.6×10^?9 M (3σ) for ATP and 5.2×10^?13 M (3σ) for lysozyme were simultaneously obtained. The satisfactory determination of ATP and lysozyme in Ramos cells reveals the good selectivity and feasibility of this protocol. The DNA machine is a promising tool for ultrasensitive and simultaneous multianalysis because of its remarkable signal amplification and simple machine‐like operation.     

Aptamer‐Based SERS Assay of ATP and Lysozyme by Using Primer Self‐Generation

A simple bifunctional surface‐enhanced Raman scattering (SERS) assay based on primer self‐generation strand‐displacement polymerization (PS‐SDP) is developed to detect small molecules or proteins in parallel. Triphosphate (ATP) and lysozyme are used as the models of small molecules and proteins. Compared to traditional bifunctional methods, the method possesses some remarkable features as follows: 1) by virtue of the simple PS‐SDP reaction, a bifunctional aptamer assembly binding of trigger 1 and trigger 2 was used as a functional structure for the simultaneous sensing of ATP or lysozyme. 2) The concept of isothermal amplification bifunctional detection has been first introduced into SERS biosensing applications as a signal‐amplification tool. 3) The problem of high background induced by excess bio‐barcodes is circumvented by using magnetic beads (MBs) as the carrier of signal‐output products and massive of hairpin DNA binding with SERS active bio‐barcodes relied on Au nanoparticles (Au NPs), SERS signal is significantly enhanced. Overall, with multiple amplification steps and one magnetic‐separation procedure, this flexible biosensing system exhibited not only high sensitivity and specificity, with the detection limits of ATP and lysozyme of 0.05 nM and 10 fM , respectively.     

Highly Sensitive Electrochemiluminescence Detection of Mercury(II) Ions Based on DNA‐Linked Luminol‐Au NPs Superstructure

A novel highly sensitive electrochemiluminescence (ECL) detection protocol for mercury(II) ions was developed. Based on the strong and stable thymine? thymine mismatches complexes coordination chemistry, mercury(II) ions can specifically bind to a designed DNA strand, leading to the release of the complimentary DNA strand. The released DNA strand was then captured by magnetic beads modified with specific DNA, and then through the formation of DNA‐linked luminol‐Au nanoparticles (NPs) superstructure, a specific ECL system for mercury(II) ions was developed. Using 3‐aminopropyl‐triethoxysilane as an effective enhancer, the ECL system can detect Hg²⁺ ion within a linear range from 2.0×10^?10 mol L^?1 to 2.0×10^?8 M, with a detection limit as low as 1.05×10^?10 M (3σ). Moreover, this ECL system is highly specific for Hg²⁺, without interference from other commonly coexisted metal ions, and it can be used for the analysis of real samples.     

Trapping of photogenerated group IV radicals by TEMPO: Potential new organometallic initiators for “living” free radical polymerization

A series of trialkyl and triaryl organometallic radicals from group IV generated by hydrogen abstraction by tert‐butoxyl radical from the parent hydrides have been examined using laser flash photolysis. The rate constants for the trapping of the metal‐centered radicals by the persistent radical TEMPO were measured and were found to be large and similar to those of the carbon‐centered radical systems, yet below the diffusion controlled limit. The metal‐centered radicals were found to be efficiently trapped by TEMPO and would appear to be candidates suitable for “living” free radical polymerization similar to carbon analogue stoichiometric initiators. The radical trapping rate constants for the trialkyl series (M = Si, Ge, Sn) were found to be 8.9 × 10⁸ M⁻¹ s⁻¹ (M = Si), 7.2 × 10⁸ M⁻¹ s⁻¹ (M = Ge), and 6.2 × 10⁸ M⁻¹ s⁻¹ (M = Sn), respectively. The triaryl (Ph₃M•) series gave slightly slower rates of 1.6 × 10⁸ M⁻¹ s⁻¹ (M = Si), 3.4 × 10⁸ M⁻¹ s⁻¹ (M = Ge), and 1.9 × 10⁷ M⁻¹ s⁻¹ (M = Sn), respectively. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 238–244, 2000     

Electrochemical Luminescent DNA Sensor Based on Polymerase-assisted Signal Amplification

A novel polymerase-based electrochemical luminescence (ECL) DNA sensor was constructed for messenger RNA (mRNA) detection by cyclic chain displacement polymerization, assisted by target mRNA cycle and quantum dots signal amplification. Firstly, the mercapto-modified capture-type probe DNA (CP) was immobilized on the surface of a magneto-controlled glassy carbon electrode via Au-S bond. After the addition of target mRNA, CP was opened and hybridized with mRNA to form double-stranded DNA (dsDNA). Then polymerase, primer chain (DNA1) and bases were added, which made the primer chain extend to replace the target mRNA. After one amplification cycle, the mRNA chain could open another hairpin in order to carry out next cycle of amplification. Finally, the ECL detection was carried out by adding DNA2 labeled thioglycolic acid-CdTe quantum dots. The amplification of the target mRNA by the addition of polymerase and the signal combined with the quantum dots label greatly improved the sensitivity of the sensor. The results showed that corresponding ECL signal had a good linear relationship with logarithm of target mRNA concentration in the range of 1 × 10^?15 to 1 × 10^?11 M, with a detection limit of 3.4 × 10^?16 M (S/N = 3). Under the optimal conditions, the recoveries of mRNA spiked in human serum sample were from 97.2 % to 102.3 %. This sensor exhibited good selectivity, stability and reproducibility.     

Pursuit of reinitiation efficiency of resonance‐stabilized monomeric allyl radical generated via “degradative monomer chain transfer” in allyl polymerization

For a deeper understanding of allyl polymerization mechanism, the reinitiation efficiency of resonance‐stabilized monomeric allyl radical was pursued because in allyl polymerization it is commonly conceived that the monomeric allyl radical generated via the allylic hydrogen abstraction of growing polymer radical from monomer, i.e., “degradative monomer chain transfer,” has much less tendency to initiate a new polymer chain and, therefore, this monomer chain transfer is essentially a termination reaction. Based on the renewed allyl polymerization mechanism in our preceding article, the monomer chain transfer constant in the polymerization of allyl benzoate was estimated to be 2.7 × 10^?2 at 80 °C under the polymerization condition, where the coupling termination reaction of growing polymer radical with allyl radical was negligible and, concurrently, the reinitiation reaction of allyl radical was enhanced significantly. The reinitiation efficiencies of monomeric allyl radical were pursued by the dead‐end polymerizations of allyl benzoate at 80, 105, and 130 °C using a small amount of initiators; they increased remarkably with raised temperature. Thus, the enhanced reinitiation reactivity of allyl radical at an elevated temperature could bias the well‐known degradative monomer chain transfer characteristic of allyl polymerization toward the chain transfer in common vinyl polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A microfluidic chip‐based fluorescent biosensor for the sensitive and specific detection of label‐free single‐base mismatch via magnetic beads‐based “sandwich” hybridization strategy

A novel microfluidic chip‐based fluorescent DNA biosensor, which utilized the electrophoretic driving mode and magnetic beads‐based “sandwich” hybridization strategy, was developed for the sensitive and ultra‐specific detection of single‐base mismatch DNA in this study. In comparison with previous biosensors, the proposed DNA biosensor has much more robust resistibility to the complex matrix of real saliva and serum samples, shorter analysis time, and much higher discrimination ability for the detection of single‐base mismatch. These features, as well as its easiness of fabrication, operation convenience, stability, better reusability, and low cost, make it a promising alternative to the SNPs genotyping/detection in clinical diagnosis. By using the biosensor, we have successfully determined oral cancer‐related DNA in saliva and serum samples without sample labeling and any preseparation or dilution with a detection limit of 5.6 × 10^?11 M, a RSD (n = 5) < 5% and a discrimination factor of 3.58–4.54 for one‐base mismatch.     

Macrocyclization of polymers via ring‐closing metathesis and azide/alkyne‐“click”‐reactions: An approach to cyclic polyisobutylenes

The end‐to‐end cyclization of telechelic polyisobutylenes (PIB's) toward cyclic polyisobutylenes is reported, using either ring‐closing metathesis (RCM) or the azide/alkyne‐“click”‐reaction. The first approach uses bisallyl‐telchelic PIB's (M_n = 1650, 3680, 9770 g mol^?1) and Grubbs 1st‐, 2nd‐, and 3rd‐generation catalyst leading to cyclic PIB's in 60–80% yield, with narrow polydispersities (M_w/M_n = 1.25). Azide/alkyne‐“click”‐reactions of bisalkyne‐telechelic PIB's (M_n = 3840 and 9820 g mol^?1) with excess of 1,11‐diazido‐undecane leads to the formation of mixtures of linear/cyclic PIB's under formation of oligomeric cycles. Subsequent reaction of the residual azide‐moieties in the linear PIB's with excess of alkyne‐telechelic PEO enables the chromatographic removal of the resulting linear PEO‐PIB‐block copolymers by column chromatography. Thus pure cyclic PIB's can be obtained using this double‐“click”‐method, devoid of linear contaminants. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 671–680, 2010     

Pyridinium‐Fused Pyridinone: A Novel “Turn‐on” Fluorescent Chemodosimeter for Cyanide

A new chemodosimeter based on pyridinium‐fused pyridinone iodide ( PI ) has been obtained through a “clean reaction” method. This compound can detect CN^? in aqueous solution with a high selectivity and rapid response. The detection of CN^? occurs through the nucleophilic attack of CN^? on the C?N bond, which induces the destruction of the π‐conjugation on the pyridinium ring. Support of this detection mechanism was obtained by ¹H NMR titration, HR‐MS, and DFT calculations. Upon the addition of 10 equivalents CN^? to a solution of PI in THF/H₂O (1:1, v/v), a 57‐fold enhancement in fluorescence intensity was observed at the maximum emission wavelength of 457 nm. Meanwhile, the maximum absorption wavelength was also blue‐shifted from 447 nm to 355 nm. Other common anions such as BF₄^?, PF₆^?, F^?, Cl^?, Br^?, I^?, H₂PO₄^?, ClO₄^?, CH₃COO^?, NO₂^?, N₃^?, and SCN^? had little effect on the detection of CN^?. The response time of PI for CN^? was less than 5 seconds. The detection limit was calculated to be 5.4×10^?8 M , which is lower than the maximum permission concentration in drinking water (1.9 μM ) set by the World Health Organization (WHO).     

Electrochemical Detection of DNA Hybridization Based on the Probe Labeled with Carbon‐Nanotubes Loaded with Silver Nanoparticles

A sensitive electrochemical method for the detection of DNA hybridization based on the probe labeled with multiwall carbon‐nanotubes (MWNTs) loaded with silver nanoparticles (Ag‐MWNTs) has been developed. MWNTs were electroless‐plated with a large number of silver nanoparticles to form Ag‐MWNTs. Probe single strand DNA (ss‐DNA) with a thiol group at the 3′‐terminal labeled with Ag‐MWNTs by self‐assembled monolayer (SAM) technique was employed as an electrochemical probe. Target ss‐DNA with a thiol group was immobilized on a gold electrode by SAM technique and then hybridized with the electrochemical probe. Binding events were monitored by differential pulse voltammetric (DPV) signal of silver nanoparticles. The signal difference permitted to distinguish the match of two perfectly complementary DNA strands from the near perfect match where just three base pairs were mismatched. There was a linear relation between the peak current at +120 mV (vs. SCE) and complementary target ss‐DNA concentration over the range from 3.1×10^?14 to 1.0×10^?11 mol/L with a detection limit of 10 fmol/L of complementary target ss‐DNA. The proposed method has been successfully applied to detection of the DNA sequence related to cystic fibrosis. This work demonstrated that the MWNTs loaded with silver nanoparticles offers a great promising approach for sensitive detection of DNA hybridization.     

Preparation of a NiAl‐Oxide@Polypyrrole Composite for High‐Performance Supercapacitors

A core‐shell NiAlO@polypyrrole composite (NiAlO@PPy) with a 3D “sand rose”‐like morphology was prepared via a facile in situ oxidative polymerization of pyrrole monomer, where the role of PPy coating thickness was investigated for high‐performance supercapacitors. Microstructure analyses indicated that the PPy was successfully coated onto the NiAlO surface to form a core‐shell structure. The NiAlO@PPy exhibited a better electrochemical performance than pure NiAlO, and the moderate thickness of the PPy shell layer was beneficial for expediting the electron transfer in the redox reaction. It was found that the NiAlO@PPy₅ prepared at 5.0 mL L^?1 addition amount of pyrrole monomer demonstrated the best electrochemical performance with a high specific capacitance of 883.2 F g^?1 at a current density of 1 A g^?1 and excellent capacitance retention of 91.82 % of its initial capacitance after 1000 cycles at 3 A g^?1. The outstanding electrochemical performance of NiAlO@PPy₅ were due to the synergistic effect of NiAlO and PPy, where the uniform network‐like PPy shell with the optimal thickness made electrolyte ions more easily accessible for faradic reactions. This work provided a simple approach for designing organic–inorganic core‐shell materials as high‐performance electrode materials for electrochemical supercapacitors.     

Enzyme‐Regulated Activation of DNAzyme: A Novel Strategy for a Label‐Free Colorimetric DNA Ligase Assay and Ligase‐Based Biosensing

The DNA nick repair catalyzed by DNA ligase is significant for fundamental life processes, such as the replication, repair, and recombination of nucleic acids. Here, we have employed ligase to regulate DNAzyme activity and developed a homogeneous, colorimetric, label‐free and DNAzyme‐based strategy to detect DNA ligase activity. This novel strategy relies on the ligation‐trigged activation or production of horseradish peroxidase mimicking DNAzyme that catalyzes the generation of a color change signal; this results in a colorimetric assay of DNA ligase activity. Using T4 DNA ligase as a model, we have proposed two approaches to demonstrate the validity of the DNAzyme strategy. The first approach utilizes an allosteric hairpin‐DNAzyme probe specifically responsive to DNA ligation; this approach has a wide detection range from 0.2 to 40 U mL^?1 and a detection limit of 0.2 U mL^?1. Furthermore, the approach was adapted to probe nucleic acid phosphorylation and single nucleotide mismatch. The second approach employs a “split DNA machine” to produce numerous DNAzymes after being reassembled by DNA ligase; this greatly enhances the detection sensitivity by a signal amplification cascade to achieve a detection limit of 0.01 U mL^?1.