Biomimetic Assembly of a Polydopamine Layer on Graphene as an Electron Gate for Fluorescent MicroRNA Detection in Living Cells.

A novel strategy was developed for microRNA detection based on the fluorescence quenching of polydopamine (PDA)-coated reduced graphene oxide (RGO) nanosheets (RGO@PDA). Compared with graphene oxide (GO), the reduction of GO and modification of the surface of RGO by PDA not only improve the stability, dispersity, biocompatibility, and cellular uptake without degeneration of the unique electronic properties of graphene, but also add an electron gate for harvesting electrons, as well as enabling efficient and forward electron transfer to avoid unwanted electron transfer and realize highly sensitive miRNA detection; thus a lower detection limit can be achieved in this sensing system. Remarkably, nanoprobes consisting of RGO@PDA and fluorescein-labeled single-stranded DNA can naturally enter cancer cells without the aid of transfection agents, as well as resisting enzymatic lysis and showing almost no effect on the cell viability. More importantly, intense and time-dependent fluorescence responses were observed from the important tumor marker microRNA-21 (miR-21) in living cells; thus suggesting that the proposed sensing platform shows great promise for applications in disease diagnosis and fundamental research into biochemistry.

Fe-nitrilotriacetic acid coordination polymer nanowires: an effective sensing platform for fluorescence-enhanced nucleic acid detection.

The determination of specific nucleic acid sequences is key in identifying disease-causing pathogens and genetic diseases. In this paper we report the utilization of Fe-nitrilotriacetic acid coordination polymer nanowires as an effective nanoquencher for fluorescence-enhanced nucleic acid detection. The detection is fast and the whole process can be completed within 15 min. This nanosensor shows a low detection limit of 0.2 nM with selectivity down to single-base mismatch. This work provides us with an attractive sensing platform for applications.

Hydrogen therapy: recent advances and emerging materials.

Hydrogen therapy, leveraging its selective attenuation of hydroxyl radicals (˙OH) and ONOO-, has emerged as a pivotal pathophysiological modulator with antioxidant, anti-inflammatory, and antiapoptotic attributes. Hydrogen therapy has been extensively studied both preclinically and clinically, especially in diseases with an inflammatory nature. Despite the substantial progress, challenges persist in achieving high hydrogen concentrations in target lesions, especially in cancer treatment. A notable breakthrough lies in water/acid reactive materials, offering enhanced hydrogen generation and sustained release potential. However, limitations include hydrogen termination upon material depletion and reduced bioavailability at targeted lesions. To overcome these challenges, catalytic materials like photocatalytic and sonocatalytic materials have surfaced as promising solutions. With enhanced permeability and retention effects, these materials exhibit targeted delivery and sustained stimuli-reactive hydrogen release. The future of hydrogen therapy hinges on continuous exploration and modification of catalytic materials. Researchers are urged to prioritize improved catalytic efficiency, enhanced lesion targeting effects, and heightened biosafety and biocompatibility in future development.

Conjugation polymer nanobelts: a novel fluorescent sensing platform for nucleic acid detection.

In this article, we report on the facile and rapid synthesis of conjugation polymer poly(p-phenylenediamine) nanobelts (PNs) via room temperature chemical oxidation polymerization of p-phenylenediamine monomers by ammonium persulfate in aqueous medium. We further demonstrate the proof-of-concept that PNs can be used as an effective fluorescent sensing platform for nucleic acid detection for the first time. The general concept used in this approach lies in the facts that the adsorption of the fluorescently labeled single-stranded DNA probe by PN leads to substantial fluorescence quenching, followed by specific hybridization with the complementary region of the target DNA sequence. This results in desorption of the hybridized complex from PN surface and subsequent recovery of fluorescence. We also show that the sensing platform described herein can be used for multiplexing detection of nucleic acid sequences.

Poly(2,3-diaminonaphthalene) microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection.

In this Communication, we report on the first preparation of conjugation polymer poly(2,3-diaminonaphthalene) (PDAN) microspheres via chemical oxidation polymerization of 2,3-diaminonaphthalene (DAN) monomers by ammonium persulfate (APS) at room temperature. We further demonstrate the use of PDAN microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection.

Coordination polymer nanobelts for nucleic acid detection.

Herein, coordination polymer nanobelts (CPNBs) were prepared rapidly and on a large scale, by directly mixing aqueous AgNO(3) solution and an ethanol solution of 4, 4'-bipyridine at room temperature. The application of such CPNBs as a fluorescent sensing platform for nucleic acid detection was further explored. CPNB is a π-rich structure, the strong π-π stacking interactions between unpaired DNA bases and CPNB leads to adsorption of fluorescently labeled single-stranded DNA (ssDNA) accompanied by 66% fluorescence quenching. However, the presence of target ssDNA will hybridize with the probe. The resultant helix cannot be adsorbed by CPNB due to its rigid conformation and the absence of unpaired DNA bases. Thus, a significant fluorescence enhancement, 73% fluorescence recovery, was observed in DNA detection as long as the target exists. The present system has excellent sensitivity; a substantial fluorescence enhancement was observed when the concentration of the target was as low as 5 nM. It also exhibits outstanding discrimination ability down to a single-base mismatch.

Coordination polymer nanobelts as an effective sensing platform for fluorescence-enhanced nucleic acid detection.

In this communication, the application of coordination polymer nanobelts (CPNs) assembled from H(2)PtCl(6) and 3,3',5,5'-tetramethylbenzidine (TMB) are explored as an effective fluorescent sensing platform for nucleic acid detection for the first time. The suggested method has a high selectivity down to single-base mismatch. DNA detection is accomplished by the following two steps: (1) CPN binds fluorecent dye-labeled single-stranded DNA (ssDNA) probe via both electrostatic attraction and π-π stacking interactions between unpaired DNA bases and CPN. As a result, the fluorescent dye is brought into close proximity to CPN and substantial fluorescence quenching occurs due to photoinduced electron transfer from the nitrogen atom in CPN to the excited fluorophore. (2) The hybridization of adsorbed ssDNA probe with its target generates a double stranded DNA (dsDNA). The duplex cannot be adsorbed by CPN due to its rigid conformation and the absence of unpaired DNA bases, leading to an obvious fluorescence enhancement.

Ultrathin graphitic carbon nitride nanosheets: a novel peroxidase mimetic, Fe doping-mediated catalytic performance enhancement and application to rapid, highly sensitive optical detection of glucose.

In this article, we demonstrate for the first time that ultrathin graphitic carbon nitride nanosheets (g-C3N4) possess peroxidase activity. Fe doping of the nanosheets leads to peroxidase mimetics with greatly enhanced catalytic performance and the mechanism involved is proposed. We further demonstrate the novel use of such Fe-g-C3N4 as a cheap nanosensor for simple, rapid, highly selective and sensitive optical detection of glucose with a pretty low detection limit of 0.5 µM.

Novel use of poly(3,4-ethylenedioxythiophene) nanoparticles for fluorescent nucleic acid detection.

In this paper, we demonstrate the novel use of poly(3,4-ethylene dioxythiophene) (PEDOT) nanoparticle as a very effective fluorescent sensing platform for the detection of nucleic acid sequences. The principle of the assay lies in the fact that the adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by PEDOT nanoparticle leads to substantial fluorescence quenching, followed by specific hybridization with the complementary region of the target DNA sequence. This results in desorption of the hybridized complex from PEDOT nanoparticle surface and subsequent recovery of fluorescence. A detection limit as low as 30 pM could be achieved in this sensing system. We also demonstrate its application for multiplexed detection of nucleic acid sequences. Furthermore, this sensing system can realize the detection of single-base mismatch even in multiplexed format. It is of importance to note that the successful use of this sensing platform in human blood serum system is also demonstrated.

Rectangular coordination polymer nanoplates: large-scale, rapid synthesis and their application as a fluorescent sensing platform for DNA detection.

In this paper, we report on the large-scale, rapid synthesis of uniform rectangular coordination polymer nanoplates (RCPNs) assembled from Cu(II) and 4,4'-bipyridine for the first time. We further demonstrate that such RCPNs can be used as a very effective fluorescent sensing platform for multiple DNA detection with a detection limit as low as 30 pM and a high selectivity down to single-base mismatch. The DNA detection is accomplished by the following two steps: (1) RCPN binds dye-labeled single-stranded DNA (ssDNA) probe, which brings dye and RCPN into close proximity, leading to fluorescence quenching; (2) Specific hybridization of the probe with its target generates a double-stranded DNA (dsDNA) which detaches from RCPN, leading to fluorescence recovery. It suggests that this sensing system can well discriminate complementary and mismatched DNA sequences. The exact mechanism of fluorescence quenching involved is elucidated experimentally and its use in a human blood serum system is also demonstrated successfully.

Hydrothermal treatment of grass: a low-cost, green route to nitrogen-doped, carbon-rich, photoluminescent polymer nanodots as an effective fluorescent sensing platform for label-free detection of Cu(II) ions.

Increasing reaction temperature produces photoluminescent polymer nanodots (PPNDs) with decreased particle size and increased quantum yield. Such PPNDs are used as an effective fluorescent sensing platform for label-free sensitive and selective detection of Cu(II) ions with a detection limit as low as 1 nM. This method is successfully applied to determine Cu(2+) in real water samples.

Fluorescence-enhanced nucleic acid detection: using coordination polymer colloids as a sensing platform.

Coordination polymer colloids have been used as an effective fluorescent sensing platform for multiplexing nucleic acid detection capable of distinguishing complementary and mismatched target sequences for the first time.

Mesoporous carbon microparticles as a novel fluorescent sensing platform for thrombin detection.

The present paper presents the novel use of MC microparticles (MCMPs) as a novel fluorescent sensing platform for thrombin detection. The MCMPs were prepared by a nanocasting method using mesoporous silica (MS) NPs as a hard template. The general concept used in this approach lies in the facts that the non-covalent adsorption of the dye-labeled TA on MCMP driven by π-π stacking of DNA bases on MCMP leads to substantial quenching of dye fluorescence due to their very close proximity. However, the presence of target TB results in the change of TA conformation to quadruplex due to the quadruplex-TB complex formation. Because the binding between the complex and MCMP is not strong enough to guarantee the close proximity of dyes to MCMP surface, fluorescence quenching is suppressed. This sensing system has a low detection limit down to 0.25 nM and exhibits excellent selectivity. We also demonstrate its application in human blood serum system.

Synthesis of Au nanoparticles decorated graphene oxide nanosheets: noncovalent functionalization by TWEEN 20 in situ reduction of aqueous chloroaurate ions for hydrazine detection and catalytic reduction of 4-nitrophenol.

In this paper, we develop a cost-effective and simple route for the synthesis of Au nanoparticles (AuNPs) decorated graphene oxide (GO) nanosheets using polyoxyethylene sorbitol anhydride monolaurate (TWEEN 20) as a stabilizing agent for GO as well as a reducing and immobilizing agent for AuNPs. The AuNPs assemble on the surface of TWEEN-functionalized GO by the in situ reduction of HAuCl(4) aqueous solution. The morphologies of these composites were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the resultant AuNPs decorated GO nanosheets (AuNPs/TWEEN/GO) exhibit remarkable catalytic performance for hydrazine oxidation. This hydrazine sensor has a fast amperometric response time of less than 3s. The linear range is estimated to be from 5 µM to 3 mM (r=0.999), and the detection limit is estimated to be 78 nM at a signal-to-noise ratio of 3. The AuNPs/TWEEN/GO composites also exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activity via a synergistic effect.