Boron carbon oxyphosphide heterostructured nanodots with phosphate tunable emission for switchable dual detection channels of 6-mercaptopurine assay.

The preparation of boron-carbon-oxygen (BCO)-based heterostructure needs commonly high temperature, high pressure and/or auxiliary strong oxidant. And the BCO-based probe for the sensing application is still rare owing to their few active groups, low quantum yield or missing specificity. Exploring BCO-based heterostructured probe via simple routes and application in sensing, therefore, is highly challenging. Herein, we proposed a novel boron-carbon-phosphorus-oxygen (BCPO) nanodot with phosphate tunable near-ultraviolet emission performance and narrow full width at half maximum by a facile, green and gentle synthesis process. The BCPO not only exhibits a distinctive colorimetric response to 6-mercaptopurine (6-MP), but also displays 6-MP-sensitive photoluminescence quenching. Thus, dual detection channels for 6-MP based on BCPO probe have been developed, and the mechanism has been speculated. Enrichment-electron of the 6-MP can be adsorbed at the boron vacancy orbits of the BCPO by the chemical action. The formation of 6-MP/BCPO complexes trigger the efficient photoluminescence quenching and light-absorbing enhancing of the BCPO, owing to the synergistic effect of the acceptor-excited photo-induced electron/energy transfer, inner filter effect and p/π-π conjugated stacking. Furthermore, the presence of ClO- anion efficaciously sparks the release of the 6-MP molecule from the 6-MP/BCPO complexes, thereby a rapid photo-switch of the BCPO for the 6-MP has been developed. Thus, this study can not only guide the further rational design of the BCPO probe, but also inspire the in-depth application of the BCPO and other nanomaterial-based probes.

Excitation-independent emission carbon nanoribbon polymer as a ratiometric photoluminescent probe for highly selective and sensitive detection of quercetin.

In this study, sulfur-nitrogen co-doped carbon nanoribbon (SNCNR) polymers with stable dual-emission fluorescence were synthesized using a one-step traditional hydrothermal method of 6-mercaptopurine in an aqueous methanol solution. Unexpectedly, the as-prepared SNCNRs with excitation-independent emission, as carbon nanomaterial derivatives, showed stable dispersions of a reticular-like shape and different lengths in the skeleton diameter. Compared with other carbon nanomaterials, the SNCNRs dramatically improved the electronic properties and surface chemical reactivities, and exhibited a sensitive ratiometric response to quercetin (Que) because of the Meisenheimer-like complexes formed through π-π stacking and electrostatic interaction. By using this SNCNR sensor, excellent ratiometric linear relationships (FL345 nm/FL420 nm) existed between the degree of quenching of the SNCNRs and the concentrations of Que in the range of 50.0 nM to 200 µM, and the limit of detection was 21.13 nM (3σ/k). Meanwhile, this sensor shows high selectivity for Que over other biomolecules, most amino acids and metal ions under the same conditions. Finally, this fluorescent probe was successfully applied to the direct analysis of Que in bovine serum and some beverage samples, which showed that it has potential for use in applications in clinical diagnosis and food analysis, and may pave the way for the design of effective fluorescent probes for other biologically related targets and food protection.

Carbon nanospheres with dual-color emission and their application in ratiometric pyrophosphate sensing.

Herein, we employ pH-dependent solubility equilibrium to develop the one-pot aqueous synthesis of dual-color emission fluorescent carbon nanosphere (DFCSs) with novel physicochemical properties. Unexpectedly, some of the DFCSs have a regular nanosphere shape, containing uniform carbon dots (∼20 nm) on their surface. This may be attributed to the change in the surface composition of the carbon nanospheres under the strong alkaline conditions (pH 13), which results in dual-wavelength emission by single-wavelength excitation. Interestingly, the fluorescence intensities of the two emission peaks of the DFCSs at 315/410 nm can be simultaneously quenched upon the addition of Co2+ due to the strong coordination between Co2+ and the O-containing luminescent groups from the carbon dots and DFCSs. Also, the results demonstrate that one Co2+ simultaneously combines with two chromophoric groups. Furthermore, the quenched DFCSs exhibit high sensitivity for pyrophosphate (PPi) in the range of 0.075-200.0 µM through a fluorescence recovery process, which can be attributed to the stronger Co2+-O[double bond, length as m-dash]P bond. This results in the removal of Co2+ from the surface of DFCSs-Co2+ system via competitive adsorption interactions. Meanwhile, this sensor shows high selectivity for PPi over mercapto amino acid and phosphate in aqueous solution. These results indicate the DFCSs can act as a dual-signal PPi-selective sensor via a ratiometric competitive mechanism.

Photoluminescent coral-like carbon-branched polymers as nanoprobe for fluorometric determination of captopril.

The authors describe the synthesis of fluorescent coral-like carbon nano-branched polymers (PCNBPs) co-doped with nitrogen and phosphorus. Uric acid and phosphoric acid act as nitrogen and phosphorus sources, respectively. The PCNBPs have a coral-like branched structure, are cross-connected, and < 20 nm in skeleton diameter. Their blue fluorescence, best measured at excitation/emission wavelengths of 330/425 nm, is quenched by mercury (II) ions due to the specifically restricted rigid conformation caused by the interaction of phosphorus, nitrogen, and oxygen groups on the surface of the PCNBPs. Fluorescence is selectivity quenched by Hg(II) but restored in addition of the hypertension drug captopril (CAP) in the range 50 nM to 40 µM concentration range. Fluorescence recovery is attributed to the effectively specific interactions between the thiol group of CAP and Hg(II). The method was applied to the determination of the concentration of Cap in pharmaceutical samples, and recoveries were between 97.6 and 105.1%. Graphical abstract Fluorescent coral-like carbon nano-branched polymers (PCNBPs) co-doped with nitrogen and phosphorus are described. Their fluorescence is selectivity quenched by Hg(II) but restored in addition of the hypertension drug captopril (Cap) in the range 50 nM to 40 µM concentration range.

Multiplexed ratiometric photoluminescent detection of pyrophosphate using anisotropic boron-doped nitrogen-rich carbon rugby ball-like nanodots.

The shape of nanoparticles is decisive for their intrinsic physicochemical properties, as well as for the anisotropic behavior of individual particles in many instances. Herein, boron-doped nitrogen-rich carbon rugby ball-like nanodots (BNCRDs) have been synthesized by a heterophase polymerization route at a vital mass ratio of phenylboronic acid and uric acid in the precursor solution. Unexpectedly, the as-prepared BNCRDs showed stable dispersions of ellipsoidal carbonaceous polymer nanodots (rugby ball-like structures that are approximately 150 nm in length) as novel carbon dot derivatives. The anisotropic BNCRDs are water-soluble compounds that have highly enhanced photoluminescence (PL), which is accompanied by a large red shift of the emission peak upon the addition of Hg2+ and is nearly quenched upon the addition of Cu2+. This is due to the chelation-enhanced fluorescence property of the BNCRDs following Hg2+ complexation with sterically efficient heteroaromatics in the BNCRDs and the chelation enhancement quenching effect of the BNCRDs following Cu2+ complexation with the N/O donor atoms of the surface of the BNCRDs, respectively. Importantly, the BNCRD PL, which is changed by Hg2+ and Cu2+, exhibits high selectivity and sensitivity for the pyrophosphate ion (PPi) in the ranges 50 nM-280 µM and 10 nM-100 µM through a photoluminescent reset process, respectively, and could be attributed to the effective coordination/chelation interactions between Hg2+/Cu2+ and the plentiful oxygen groups of PPi. These results indicate that anisotropic BNCRDs can act not only as a ratiometric sensor for Hg2+ but also as a dual-mode PPi-selective sensor via ratiometric displacement and a competitive mechanism. With the broad diversity in the molecular backbone of the carbon dots via rich chemical routes, anisotropic BNCRDs have been developed with unique structural, electrical, and attractive functions, which greatly expands the research horizon of carbon-based composites.

Construction and screening of SARS-CoV S protein-specific phage displayed antigen library / 病毒学报

The aim of this study is to construct a SARS-CoV S protein-specific phage displayed antigen library for the epitope characterization of anti-S monoclonal antibodies (mAbs). First, the full-length gene of SARS-S protein was PCR amplified, purified and then digested with DNase I to obtain DNA fragments in the size range of 50-500 bp. The resulting fragments were blunt-end ligated to the modified phage display vector pComb3XSS. The reactions were electrotransformed into XL1-Blue and infected with VCSM13 helper phage. The SARS-CoV S protein-specific phage displayed antigen library was biopanned and screened against two anti-S mAbs, S-M1 and S-M2. The results showed that we successfully constructed the phage displayed antigen library with a size of 5.7 x 10(6). After three-rounds of biopanning, 14 positive phage clones for S-M1 and 15 for S-M2 were respectively identified. Sequence analyses revealed the possible epitopes of two mAbs. Therefore, the S protein-specific phage displayed antigen library provides a crucial platform for the epitope characterization of anti-S antibodies and it is highly valuable for development of SARS vaccines and diagnostics.

Identification of human monoclonal HIV-1-neutralizing antibodies from phage antibody library by cell-based screening / 病毒学报

To identify human monoclonal HIV-l-neutralizing antibodies from an HIV-1 CRF07BC specific phage display antibody library by cell-based screening. 293T cells were transfected by pCH064. 2-Env plas mid and then used to biopan the phage antibody library. The positive phage clones were screened by cell based ELISA and sequenced for the variable region of heavy (VH) and light (VL) chains. The expressed Fabs were purified by Ni(+2) -NTA column and analyzed by SDS-PAGE. The cell- and gp120 protein-based ELISA as well as flow cytometry were used to measure Fab's binding activity. The neutralizing activity of Fabs was assessed by HIV-1 pseudoviruses. After 4-round biopanning, the binding phages to transfected cells were enriched about 650-folds. A total of 28 positive clones were screened out by cell ELISA and sequence analysis identified 5 different Fabs possessing unique VH and VL (2801, 2837, 2863, 2870 and 2920). Interestingly, these Fabs reacted with the Env-transfected 293T cells but not soluble gp120 proteins, suggesting that they might target conformation-dependent epitopes presenting on viral Env complex. We found that three Fabs (2801, 2863, 2870) exhibited potent neutralizing activity against CRF07_BC isolate CH120. 6 with IC50 of 2.24, 0.89 and 3.09 microg/mL respectively, and that 2801 and 2863 cross-neutral ized the subtype B isolate SF162 at IC50 of 0.69 and 3.52 microg/mL respectively. In conclusion, the HIV-1 Env-transfected 293T cells can be used to efficiently enrich and screen the phage antibody library and isolate human monoclonal HIV-1-neutralizing Fabs that target the Env complex-dependent conformational epitopes. Therefore, our studies provide a powerful platform for exploring the mechanism of HIV-1 neu tralizing response and for designing AIDS vaccines.