DNA conformational change embrace ultraviolet photolysis: A dual-mode sensing platform for electrochemical and fluorescent signaling.

We developed a dual-mode biosensor that utilizes DNA conformational changes and ultraviolet photolysis for electrochemical (EC) and fluorescence (FL) detection. In this study, a stem-loop-structured carcinoembryonic antigen (CEA) aptamer was modified on an Au electrode, and this aptamer contained a redox-labeled methylene blue (MB), short-chain DNA with a 6-carboxylic fluorescein (FAM) and a PC linker that can be cleaved by ultraviolet light. Subsequently, CEA and CEA antibody-modified upconversion nanoparticle bioconjugates (CEA-Ab@UCNPs) were added. In the presence of CEA, Ab@UCNPs can bind CEA and push the MB which was originally close to the electrode surface, away from the electrode surface, resulting in a reduced redox current. Under irradiation with a 980 nm laser, the UCNPs emit ultraviolet light, leading to photocleavage of the PC linker and the release of FAM for FL sensing. Under optimal conditions, the EC and FL modes showed good responses to CEA within 0.01-50 ng/mL and 0.1-80 ng/mL, respectively.

Multifunctional nanozymes for disease diagnosis and therapy.

The development of nanotechnology has brought about groundbreaking advancements in diseases' diagnostics and therapeutics. Among them, multifunctional nanomaterials with enzyme-like activities (i.e., nanozymes) featured with high stability, large surface area for bioconjugation, and easy storage, offer unprecedented opportunities for disease diagnostics and treatment. Recent years have witnessed the great progress of nanozyme-based theranostics. To highlight these achievements, this review first introduces the recent advancements on nanozymes in biosensing and diagnostics. Then, it summarizes the applications of nanozymes in therapeutics including anti-tumor and antibacterial treatment, anti-inflammatory treatment, and other diseases treatment. In addition, several targeted strategies to improve the therapeutic efficacy of nanozyme are discussed. Finally, the opportunities and challenges in the field of diagnosis and therapy are summarized.

Insights into Photothermally Enhanced Photocatalytic U(VI) Extraction by a Step-Scheme Heterojunction.

In this work, a CdS/BiVO4 step-scheme (S-scheme) heterojunction with self-photothermally enhanced photocatalytic effect was synthesized and applied for efficient U(VI) photoextraction. Characterizations such as transient absorption spectroscopy and Tafel test together confirmed the formation of S-scheme heterojunctions, which allows CdS/BiVO4 to avoid photocorrosion while retaining the strong reducing capacity of CdS and the oxidizing capacity of BiVO4. Experimental results such as radical quenching experiments and electron spin resonance show that U(VI) is rapidly oxidized by photoholes/•OH to insoluble UO2(OH)2 after being reduced to U(IV) by photoelectrons/•O2 -, which precisely avoids the depletion of electron sacrificial agents. The rapid recombination of electron-hole pairs triggered by the S-scheme heterojunction is found to release large amounts of heat and accelerate the photocatalysis. This work offers a new enhanced strategy for photocatalytic uranium extraction and presents a direction for the design and development of new photocatalysts.

Multistimuli-Responsive Materials Based on Zn(II)-Viologen Coordination Polymers and Their Applications in Inkless Print and Anticounterfeiting.

Recently, stimuli-responsive materials have attracted great attention, while most of them respond to single or two stimuli. Thus, it is essential to design multifunctional stimuli-responsive materials and develop their applications. The strategy that constructing high-dimensional coordination polymers facilitates the application scope of a viologen-based photochromic system is put forward and confirmed for the first time. Herein, a novel multistimuli-responsive viologen-based Zn-MOF with a two-dimensional framework has been successfully designed and synthesized. Complex 1 exhibits chromic behavior under a variety of external stimuli such as 365 nm UV, X-rays, heat, electricity, and ethylamine. More interestingly, the crystal state of complex 1 displays dual fluorescence and room-temperature phosphorescence (RTP) emission and emits a yellow afterglow when turning off the UV lamp. In addition, Eu(III)-functionalized hybrids, Eu3+@Zn-MOF, were prepared by coordinated postsynthetic modification based on viologen complexes for the first time. The sample of Eu3+@Zn-MOF inherits the photochromic characteristics of the viologen complexes and gives the distinctive fluorescence of the europium ions. Based on the multicolor switching of 1 and Eu3+@Zn-MOF, their possible practical utilization was successfully developed in the fields of inkless, erasable print media, electrochromic information tag printing, information encryption, and anticounterfeiting.

Synthesis and Characteristics of Self-Assembled Multifunctional Ln3+ -DNA Hybrid Coordination Polymers.

Owing to the unique catalytic, optical and magnetic properties, lanthanides (Ln) as multicomponent biomarkers, are widely used in the field of optical sensing, mass spectrometry and magnetic resonance imaging. As ligands, DNA molecules have good biocompatibility, high stability, cost efficiency, programmability and biodegradability. Based on the coordination-driven self-assembly between Ln ions (Ln3+ ) and DNA molecules, a multifunctional Ln3+ -DNA hybrid coordination polymers (CPs) were synthesized. Not only a series of different Ln3+ (single Ln3+ ) and DNA hybrid CPs were synthesized, but one hybrid CP contains two kinds of Ln3+ was obtained. Besides, the synthetic CPs in cell fluorescence imaging and miRNA sensing also exhibited high performance. This work provides a novel idea for the synthesis of DNA based nanomaterials, which is promising for biologically-related applications.

Spatiotemporally Controlled DNA Nanoclamps: Single-Molecule Imaging of Receptor Protein Oligomerization.

Cell membrane surface receptor proteins play an important role in cellular biological processes. There are numerous methods to detect receptors, yet developing an artificially controlled and specific detection and treatment strategy remains a challenge. Herein, we develop such a strategy based on upconversion nanoparticles (UCNPs) loaded DNA probes that enable two-color ratiometric imaging excitated by a 980 nm laser. The light response controllable signal opening strategy avoids waste during probe transportation and improves sensitivity. Thereby the number of receptors on individual DU145 cell membranes is counted by single-molecule detection. Due to the different expression of specific receptor proteins, the number of single fluorescent dots counted can be used as a basis for distinguishing DU145 from other cells. This work is highly controllable to increase sensitivity, providing a platform for cancer diagnosis and treatment.

Target-triggered and controlled release plasmon-enhanced fluorescent AIE probe for conformational monitoring of insulin fibrillation.

In this work, we constructed a target-triggered and controlled-release plasmon-enhanced fluorescent AIE probe to realize the purpose of conformational monitoring of insulin fibrillation. We synthesized a novel water-soluble anthracene derivative, 4,4',4'',4'''-(anthracene-9,10-diylbis(ethene-2,1,1-triyl))tetrakis(N,N,N-trimethylbenzenaminium) iodide (BDVAI), with AIE properties, high biocompatibility and good self-assembly effect. Gold nanocages (AuNCs) were selected as the substrate for PEF, and the inner space of hollow AuNCs was filled with BDVAI. Thiol-modified DNA chains were bonded to the surface of AuNCs by Au-S bonds, and an insulin aptamer was combined with the sulfhydryl chain to seal the AuNCs. This PEF-AIE sensor produces different fluorescence signals when interacting with native insulin and fibrillar insulin; thus, monitoring conformational changes in insulin can be realized by detecting fluorescence intensity changes during insulin fibrillation. Based on this design, this system realized sensitive detection of fibrillar insulin with a detection limit of 23.6 pM. This AIE molecular-based PEF fluorescence enhancement system improves the optical properties of fluorescent substances, which is of great significance in improving the detection sensitivity of amyloid fibrils conformational changes and providing a reliable basis for further understanding the pathogenesis of amyloidosis.

Integrating Near-Infrared Visual Fluorescence with a Photoelectrochemical Sensing System for Dual Readout Detection of Biomolecules.

Compared with traditional visible light-driven fluorescence visualization (FV), near-infrared (NIR)-induced FV is an interesting and promising method, while photoelectrochemical (PEC) immunoassay sensing possesses the advantages of high sensitivity, low cost, and simple instrumentation. We combined PEC sensing with NIR-induced FV together and developed a dual readout sensing platform. In this protocol, based on the antibody-analyte (i.e., antigen, DNA, and RNA) reaction and the sandwich-type structure, CuInS2 microflowers as the matrix provided the original background photocurrent; chlorin e6 (Ce6) was conjugated to antibody-modified upconversion nanoparticles and formed a signal label for the PEC sensing and naked-eye readout. Different from traditional PEC immunosensors, under NIR illumination, the developed dual mode sensing platform could achieve quick qualitative analysis and quantitative analysis. Preliminary application performance of the proposed biosensor in prostate-specific antigen analysis is acceptable, indicating its promising potential in clinical/biological studies.

Preparation of PbS NPs/RGO/NiO nanosheet arrays heterostructure: Function-switchable self-powered photoelectrochemical biosensor for H2O2 and glucose monitoring.

On the basis of synthesized PbS nanoparticles (PbS NPs)/reduced graphene oxide (RGO)/NiO nanosheet arrays (NiO NSAs) heterostructure, we constructed a function-switchable self-powered PEC sensing platform for the analysis of H2O2 and glucose. Ordered NiO NSAs have high electron mobility, modifying RGO onto the surfaces of NiO NSAs can connect the NiO NSAs with the PbS NPs and promoted the electron transfer rate between them, as well as enhance their photocurrent response. The PbS NPs/RGO/NiO NSAs heterostructure own excellent catalase-like activity can achieve H2O2 detection, only with one more step, after introducing glucose oxidase (GOD) onto the surface of PbS NPs/RGO/NiO NSAs heterostructure, we realized the detection conversion between H2O2 and glucose. Under optimal conditions, the proposed biosensor exhibited superior analytical performance toward H2O2 and glucose, a limit of detection (LOD) of 0.018 mM (S/N = 3) and 5.3 × 10-8 M (S/N = 3) were obtained, respectively. Moreover, good accuracy was obtained in the real samples analysis of H2O2 disinfectant and human serum samples.

Using PbS-Au heterodimers as signal quencher for the sensitive photoelectrochemical immunoassay of amyloid ß-protein.

By using PbS-Au heterodimers as the signal quencher, TiO2/BiOI as matrix, a novel sandwich-type photoeletrochemical (PEC) biosensor for sensitive determination of amyloid ß-protein (Aß, ∼4 KDa) was developed. BiOI was attached to the surface of TiO2 and formed a heterogeneous structure (p-n junction), which enlarged the light harvest range and enhanced the electron transfer rate of TiO2. In order to quench the PEC signal, PbS-Au heterodimers were used as the labels to combine with Aß. Owing to the competitively light energy harvesting and electron donor consuming effect of PbS-Au heterodimers, less light energy and electron donor arrived at TiO2/BiOI. In addition, Au directly contacted with PbS could enhance the electron seperation and transfer rate, and lead to improved competitiveness consumption of the electron donor. PbS-Au integrated with secondary antibodies formed PbS-Au-Ab2 bioconjugate, which would further obstruct the electron transfer and impede the interreaction between electron donor and photoelectrode surfaces. Owing to the unique PbS-Au heterodimer structure and the quenching effect of PbS-Au-Ab2 bioconjugate, the fabricated immunosensor for Aß detection exhibited good stability, high sensitivity, and a low detection limit of 0.028 pg/mL (S/N = 3).

Electrochemiluminescent immunoassay for insulin by using a quencher pair consisting of CdS:Eu nanoclusters loaded with multiwalled carbon nanotubes on reduced graphene oxide nanoribbons and gold nanoparticle-loaded octahedral Cu2O.

A sensitive electrochemiluminescence (ECL) immunosensor was constructed for detection of insulin. It is based on the quenching effect of octahedral cuprous oxide decorated with gold nanoparticles (Cu2O@Au NPs). A composite constructed from multiwalled carbon nanotubes/reduced graphene oxide nanoribbons provides a large specific surface that promotes electron transfer on the surface of electrodes. In parallel, CdS nanoclusters were loaded with europium(III) to get CdS:Eu NCs. The Eu(III) ions exert a large enhancement in ECL intensity of the CdS NCs. Cu2O is biocompatible and has a large specific surface. It was used as a quencher for the ECL immunosensor. If Au NPs are loaded onto Cu2O, the green fluorescence of the CdS NCs (with emission peaks at 525 nm) is quenched. The Cu2O@Au NPs also can be employed as a label for the secondary antibodies (Ab2) to improve the sensitivity of the ECL immunosensor. The assay works in the 0.5 pg·mL-1 to 50 ng·mL-1 insulin concentration range and has a detection limit of 40 fg·mL-1. Graphical abstract The multiwalled carbon nanotubes/reduced graphene oxide nanoribbons (MWCNT/rGONRs-CdS: Eu NCs) was used as substrate. Europium(III) (Eu3+) improves the ECL intensity of CdS NCs. The synergistic effect between Cu2O and Au NPs decreases the electrochemiluminescence of MWCNTs/rGONRs-CdS:Eu NCs.

Manganese doped CdS sensitized graphene/Cu2MoS4 composite for the photoelectrochemical immunoassay of cardiac troponin I.

As a newly emerged photoactive material, Cu2MoS4 has motivated wide research interests in the field of photoelectrochemistry. Based on manganese doped CdS (CdS:Mn) sensitized graphene (G)/Cu2MoS4 composite, we developed a label-free photoelectrochemical (PEC) immunosensor for the detection of cardiac troponin I (cTnI). G as an excellent 2D conductive material, combined with Cu2MoS4 could improve its charge transfer efficiency. CdS:Mn nanoparticles (NPs) loaded on G/Cu2MoS4 further enlarged the light absorption range of Cu2MoS4 and restrained the electron-hole pairs recombination. Under optimal conditions, the proposed PEC immunosensor responded sensitively to cTnI with a low detection limit of 0.18 pg/mL and a wide linear range (0.005-1000 ng/mL). Moreover, as-fabricated immunosensor also exhibited high sensitivity, excellent selectivity and good stability. This work also was extended to real samples analysis and obtained satisfied results.

Preparation and characterization of 0D Au NPs@3D BiOI nanoflower/2D NiO nanosheet array heterostructures and their application as a self-powered photoelectrochemical biosensing platform.

In this work, we demonstrate that zero-dimensional Au nanoparticles (0D Au NPs)-decorated three-dimensional bismuth oxyiodide (BiOI) nanoflower (3D BiOI NFs)/two-dimensional nickel oxide (NiO) nanosheet array (2D NiO NSAs) hybrid nanostructures can be used as a self-powered cathodic photoelectrochemical (PEC) biosensing platform. The in situ formation of 3D BiOI NFs on 2D NiO NSAs was carried out by a chemical bath deposition method, while 0D Au NPs were coated on 3D BiOI NFs/2D NiO NSAs through a dip-coating method. Subsequently, glucose oxidase (GOD) as an enzyme model was immobilized on the surface of a Au@BiOI/NiO electrode via the adhesion of poly-(diallyldimethylammonium chloride) (PDDA). The proposed heterostructure exhibited excellent PEC properties because the unique structure of the Au NPs@BiOI NFs/NiO NSAs increased the specific surface area, light harvesting ability and the surface plasmon resonance effect of the Au NPs. The system displayed high sensitivity toward glucose in the presence of an air-saturated electrolyte. At the optimum conditions, the biosensor showed a promising application for the self-powered cathodic PEC biosensing of glucose, with a dynamic linear range of 1 × 10-7 M to 5 × 10-2 M and a low limit of detection of 8.71 × 10-8 M. Moreover, the proposed self-powered PEC biosensor was evaluated for the determination of diluted glucose injections, with the results indicating the potential of the proposed biosensor for bioanalysis applications.

Electrochemical immunosensor for ochratoxin A detection based on Au octahedron plasmonic colloidosomes.

The accurate and rapid fungaltoxin detection at early stage can prevent people from getting cancer to a great extent. Here, an ultrasensitive electrochemical immunosensor for the detection of ochratoxin A was reported. Octahedral gold nanoparticles (Oct Au NPs) with edge and sharp corners as substrate materials can connect more primary antibodies and Au octahedron plasmonic colloidosomes (Au Oct PCs) were formed by the natural settlement of the Oct Au NPs in the inverse emulsion system. Au Oct PCs with high specific surface area and good electron transfer ability can hybridize with electron mediator toluidine blue to act as labels to amplify the output signal and ameliorate the stability of the immunosensor. The immunoassay was performed via the square wave voltammetry and showed a strong current response. The proposed immunosensor obtained a wide linear range from 0.1 pg mL-1 to 10 ng mL-1 and a low detection limit of 39 fg mL-1. This new strategy achieved favorable stability, reproducibility and selectivity, which had potential application in real sample analysis.

Ultra-thin wrinkled NiOOH-NiCr2O4 nanosheets on Ni foam: an advanced catalytic electrode for oxygen evolution reaction.

Here, we report the in situ electrochemical conversion of NiCr2O4 on Ni foam prepared using a hydrothermal strategy to give ultra-thin wrinkled NiOOH-NiCr2O4 amorphous-crystalline nanosheets on Ni foam (NiOOH-NiCr2O4/NF) via anode oxidation in 1.0 M KOH. Owing to the coordination of NiCr2O4 and NiOOH, NiOOH-NiCr2O4/NF shows superior catalytic activity toward the oxygen evolution reaction (OER) with the demand of overpotential as low as 271 mV to drive a geometrical current density of 20 mA cm-2 under alkaline conditions. Notably, it also displays strong long-term electrochemical durability for at least 30 h.

Label-free photoelectrochemical aptasensor for tetracycline detection based on cerium doped CdS sensitized BiYWO6.

A novel photoelectrochemical (PEC) aptasensor based on cerium (Ce) doped CdS modified graphene (G)/BiYWO6 was designed, which exhibits enhanced PEC intensity compared with pure BiYWO6, G/BiYWO3 and BiYWO6/Ce:CdS. In this scenario, ascorbic acid (AA) was exploited as an efficient and non-poisonous electron donor for scavenging photogenerated holes. The doping of Ce in CdS promoted its visible light absorption range and facilitated the charge transfer rate as well as hindered the h+/e- recombination. Moreover, the combination of G further promoted the electron carrier separation and transfer process due to its excellent electron collection and shuttling characteristic. Thus, the G/BiYWO6/Ce:CdS heterostructure was successfully served as a matrix for the PEC detection of tetracycline (Tc) at 0 V (vs Hg/Hg2Cl2). Under optimal conditions, the PEC aptasensor could offer a sensitive and specific detection limit (3 S/N) of Tc down to 0.01 ng/mL, as well as acceptable reproducibility, selectivity and storage stability, which opened up a promising pathway for the development of PEC biosensors.

Label-free photoelectrochemical immunoassay for CEA detection based on CdS sensitized WO3@BiOI heterostructure nanocomposite.

In this work, a label-free photoelectrochemical (PEC) immunosensor for the detection of carcino embryonic antigen (CEA) was developed based on CdS nanowires (NWs) sensitized WO3@BiOI heterostructure. The construction procedure of ITO/WO3@BiOI@CdS electrode was done by dipping the WO3@BiOI modified indium-tin oxide (ITO) electrode interchangeably into [Cd(NH3)4]2+ and S2- solution for several times. Then the ITO/WO3@BiOI@CdS electrode was used as a matrix for the subsequent immobilization of CEA antibody (Ab). The obtained label-free PEC immunosensor showed an excellent PEC performance toward CEA detection. Under optimal conditions, the PEC immunosensor have a sensitive response to CEA in a liner range of 0.01ng/mL to 50ng/mL with a detection limit of 3.2pg/mL. The proposed PEC immunosensor exhibited good stability, high sensitivity as well as reproducibility and storage stability. Moreover, the obtained PEC immunosensor also showed a satisfied result in human serum sample analysis.