Wen Weng

Aptamer-based portable biosensor for platelet-derived growth factor-BB (PDGF-BB) with personal glucose meter readout.

A novel portable biosensor for sensitive and selective detection of platelet-derived growth factor-BB (PDGF-BB) had been developed based on the specific recognition between aptamer and protein using a personal glucose meter (PGM) as readout. In the presence of PDGF-BB, the primary aptamer of PDGF-BB which is bound to the surface of streptavidin magnespheres paramagnetic particles (SA-PMPs) reacts quantitatively with invertase-functionalized secondary aptamer of PDGF-BB to form a stable complex, resulting in the attachment of invertase on the SA-PMPs. Subsequently, the invertase catalyzes the hydrolysis of sucrose to produce a large amount of glucose and quantitative readout by the PGM. The enhanced signal of the PGM has a relationship with the concentration of PDGF-BB in the range of 1.0 × 10(-14) M~3.16 × 10(-12) M, and the detection limit is 2.9 fM. The proposed portable biosensor had been successfully applied to assay the PDGF-BB in saliva samples.

Unusual chromatographic enantioseparation behavior of naproxen on an immobilized polysaccharide-based chiral stationary phase

Enantioseparation of naproxen was performed on an immobilized polysaccharide-based chiral stationary phase (CSP), Chiralpak IA, in the normal-phase mode. The effects of polar alcohol modifier in mobile phase and column temperature on retention, enantioseparation, and elution order were investigated. Two unusual phenomena were observed. One was solvent-induced reversal of elution order for the two enantiomers. Not only the type but also the content of polar alcohol modifier could induce the reversal. Another uncommon phenomenon was peak deformation under some chromatographic conditions.

Synthesis, crystal structure, and fluorescence properties of several schiff-base compounds

Two new Schiff-base compounds, 1,6-bis(4-dimethylaminobenzyl)-2,5-diaza-1,5-hexadiene (bdh), 1,4-bis(4-dimethylaminobenzyl)-2,3-diaza-1,3-butadiene (bdb), and a silver complex of the latter ([Ag2(bdb)3(NO3)2]·H2O, 1) have been synthesized and characterized. The crystal structure of complex 1 was determined. 1 is a dinuclear complex, with the silver ions lying in coordination tetrahedra formed by two nitrogen atoms from the bdb ligands and two oxygen atoms from the nitrate anions. The fluorescence properties of bdh and bdb were studied; the fluorescence of bdb was quenched by the addition of silver ions, indicating that it is a potential fluorescent reagent for the analysis of silver. *Email: gcguo@ms.fjirsm.ac.cn

Signal on fluorescence biosensor for MMP-2 based on FRET between semiconducting polymer dots and a metal organic framework

A signal on fluorescence biosensor for ultrasensitive detection of MMP-2 based on fluorescence resonance energy transfer (FRET) between semiconducting polymer dots (Pdots) and a metal–organic framework (MOF) has been developed. Carboxyl-rich PFO has been modified firmly with a polypeptide chain (COOH–GHHYYGPLGVRGC–NH2) through a carboxy ammonia reaction first. The polypeptide chain comprises the specific MMP-2 substrate domain (PLGVR) and the π-rich motif (HHYY) can be absorbed by the MOF (H2dtoaCu used in this study) through π-staking interactions. Hence, the fluorescence from Pdots can be quenched by the MOF with the assistance of the polypeptide chain linker through the FRET process. Upon the cleavage of the substrate by the protease (MMP-2) at the amide bond between Gly and Val, the Pdots has been separated from the MOF surface and therefore the FRET process can be inhibited, and the fluorescence of the system recovered. Under optimal conditions, the fluorescence recovery was found to be proportional to the concentration of MMP-2 within the range of 0.1 to 2.5 pg mL−1.

Cationic Carbon Dots for Modification-Free Detection of Hyaluronidase via an Electrostatic-Controlled Ratiometric Fluorescence Assay

Carbon dots (CDs) emerge as excellent fluorescent nanomaterials, but the full exploitation and application of their exceptional properties in the development of fluorescence assay are still rare. In this work, cationic carbon dots (C-CDs) covered with plenty of positive charges on the surface were synthesized through a facile ultrasonic method. Negatively charged hyaluronic acid (HA) caused the aggregation of positively charged C-CDs and neutral red (NR) along its linear chain via electrostatic adsorption, leading to a remarkable Förster resonance energy transfer (FRET) from C-CDs to NR. However, the presence of hyaluronidase (HAase) resulted in the enzymolysis of HA, as well as the liberation of C-CDs and NR. The corresponding change of fluorescence color from red to green-yellow afforded a reliable ratiometric assay for HAase. Also the ratio of fluorescence intensity for C-CDs (I525) to that for NR (I630) was used for quantitative detection of HAase. The proposed sensing system was easily operated in aqueous media with a detection limit of 0.05 U/mL. This strategy provides a new approach for the wider application of some special CDs in detecting biomolecules.

A novel hybridization indicator for the low-background detection of short DNA fragments based on an electrically neutral cobalt(II) complex.

An electrically neutral cobalt complex, Co(Eim)(4)(NCS)(2) (Eim=1-ethylimidazole, NCS=isothiocyanate) was synthesized and its interaction with double-stranded DNA (dsDNA) was comprehensively studied by electrochemical methods on a glassy carbon electrode (GCE). The experimental results revealed that the cobalt complex could interact with dsDNA via a specific groove-binding mode with an affinity constant of 3.6×10(5)M(-1). The surface-based studies showed that Co(Eim)(4)(NCS)(2) could electrochemically accumulate within the immobilized dsDNA layer rather than single-stranded DNA (ssDNA) layer. Based on this fact, the cobalt complex was utilized as an electrochemical hybridization indicator for the detection of oligonucleotides related to CaMV35S promoter gene. The results showed that the developed biosensor presented very low background interference due to the negligible affinity of the Co(Eim)(4)(NCS)(2) complex with ssDNA. The hybridization specificity experiments further indicated that the biosensor could well discriminate the complementary sequence from the base-mismatched and the non-complementary sequences. The complementary target sequence could be quantified over the range from 5.0×10(-9)M to 2.0×10(-6)M with a detection limit of 2.0×10(-10)M.

One-pot fabrication of hollow cross-linked fluorescent carbon nitride nanoparticles and their application in the detection of mercuric ions.

Hollow cross-linked fluorescent carbon nitride nanoparticles (CNNPs) were fabricated via a facile one-pot solvothermal process. The obtained CNNPs were characterized by multiple analytical techniques including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The excitation-dependent fluorescence emission spectra showed significant differences for the CNNPs derived from various proportions of citric acid monohydrate and urea. The fluorescence quantum yield of the obtained CNNPs could reach 31%. The CNNPs exhibited good fluorescence quenching selectivity to mercuric ions. Concentration experiments showed that there existed two parts of linear relationship between fluorescence intensity and concentration of Hg(2+) ions in the range of 0.1-8 and 8-32 μM. The limit of detection (LOD) was estimated to be 0.094 μM. This method can be applied to the detection of Hg(2+) ions in tap water samples.

A novel three-dimensional coordination polymer constructed from pyrazine and copper(I): poly[[copper(I)-di-μ2-pyrazine-κ4N:N′] 3,5-dicarboxybenzenesulfonate monohydrate]

In the title metal-organic framework complex, {[Cu(C(4)H(4)N(2))(2)](C(8)H(5)O(7)S).H(2)O}(n) or {[Cu(I)(pyz)(2)](H(2)SIP).H(2)O}(n) (pyz is pyrazine and H(3)SIP is 5-sulfoisophthalic acid or 3,5-dicarboxybenzenesulfonic acid), the asymmetric unit is composed of one copper(I) center, one whole pyrazine ligand, two half pyrazine ligands lying about inversion centres, one H(2)SIP(-) anion and one lattice water molecule, wherein each Cu(I) atom is in a slightly distorted tetrahedral coordination environment completed by four pyrazine N atoms, with the Cu-N bond lengths in the range 2.017 (3)-2.061 (3) A. The structure features a three-dimensional diamondoid network with one-dimensional channels occupied by H(2)SIP(-) anions and lattice water molecules. Interestingly, the guest-water hydrogen-bonded network is also a diamondoid network, which interpenetrates the metal-pyrazine network.

Development of a Composite Chiral Stationary Phase from BSA and β-Cyclodextrin-Bonded Silica

A composite chiral stationary phase (CSP) derived from bovine serum albumin (BSA) and β-cyclodextrin (CD)-bonded silica was prepared. 2,4,6-Trichloro-1,3,5-triazine was used as a cross-linker. The obtained CSP was applied to the enantioseparation of tryptophan, hydrobenzoin, phenylalanine and mandelic acid. The influences of eluent pH value, organic modifier and column temperature on the retention and enantioseparation were discussed. Tryptophan and hydrobenzoin achieved excellent resolution on the composite CSP. For tryptophan, the highest selectivity, 2.79, was achieved with 1% of methanol at pH 8.0. For hydrobenzoin, the selectivity could reach 1.42. The chromatographic results were compared with that on β-CD-bonded or BSA-immobilized CSP.

(μ-4,4'-Bipyridine-κN:N')bis-[triaqua-(4,4'-bipyridine-κN)(3-nitro-phthalato-κO)cobalt(II)].

The title binuclear complex, [Co2(C8H3NO6)2(C10H8N2)3(H2O)6], has been synthesized hydrothermally from 3-nitrophthalic acid (H2NPA), Co(NO3)2·6H2O and 4,4′-bipyridine (4,4′-bipy). The molecule of the complex occupies a special position on an inversion centre. The CoII atom has a slightly distorted octahedral environment formed by two N atoms from two 4,4′-bipy ligands, one carboxylate O atom from NPA, and three O atoms of water molecules. An extensive O—H⋯O and N—H⋯O hydrogen-bonding system links molecules of the complex into a three-dimensional network.