Simultaneous analysis of nine aromatic amines in mainstream cigarette smoke using online solid-phase extraction combined with liquid chromatography-tandem mass spectrometry.

A fully automated analytical method was developed and validated by this present study. The method was based on two-dimensional (2D) online solid-phase extraction liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) to determine nine aromatic amines (AAs) in mainstream smoke (MSS) simultaneously. As a part of validation process, AAs yields for 16 top-selling commercial cigarettes from China market were evaluated by the developed method under both Health Canada Intensive (HCI) and ISO machine smoking regimes.

Cationic Peptide Conjugation Enhances the Activity of Peroxidase-Mimicking DNAzymes.

Peroxidase-mimicking DNAzymes containing G-quadruplex structures are widely applied in chemistry as catalysts and signal amplification for biosensing. Enhancing the catalytic activity of these DNAzymes can therefore improve the performance of many catalysts and biosensors using them. In this work, we synthesized cationic peptide conjugates of peroxidase-mimicking DNAzymes, which were found to exhibit both enhanced peroxidase and oxidase activities up to 4-fold and 3-fold compared with the original DNAzymes, respectively.

A general approach for rational design of fluorescent DNA aptazyme sensors based on target-induced unfolding of DNA hairpins.

DNA aptazymes are allosteric DNAzymes activated by the targets of DNA aptamers. They take the advantages of both aptamers and DNAzymes, which can recognize specific targets with high selectivity and catalyze multiple-turnover reactions for signal amplification, respectively, and have shown their great promise in many analytical applications. So far, however, the available examples of DNA aptazyme sensors are still limited in utilizing only several DNAzymes and DNA aptamers, most likely due to the lack of a general and simple approach for rational design.

A ratiometric fluorescent chemosensor for Al³⁺ in aqueous solution based on aggregation-induced emission and its application in live-cell imaging.

A ratiometric fluorescent chemosensor 1 was developed for the detection of Al(3+) in aqueous solution based on aggregation-induced emmision (AIE). The chemosensor showed the fluorescence of its aggregated state and Al(3+)-chelated soluble state in the absence and in the presence of Al(3+), respectively, and resulted in a fluorescence ratio (I461/I537) response to Al(3+) in neutral aqueous solution at a detection limit as low as 0.29 μmol L(-1).

Simple and efficient method to purify DNA-protein conjugates and its sensing applications.

DNA-protein conjugates are very useful in analytical chemistry for target recognition and signal amplification. While a number of methods for conjugating DNA with proteins are known, methods for purification of DNA-protein conjugates from reaction mixture containing unreacted proteins are much less investigated. In this work, a simple and efficient approach to purify DNA-invertase conjugates from reaction mixture via a biotin displacement strategy to release desthiobiotinylated DNA-invertase conjugates from streptavidin-coated magnetic beads was developed.

A new colorimetric strategy for monitoring caspase 3 activity by HRP-mimicking DNAzyme-peptide conjugates.

A new method for caspase 3 activity assay has been developed based on HRP-mimicking DNAzyme-peptide conjugates. The mechanism of detection was based on the specific cleavage of DEVD-peptides by active caspase 3 for recognition and the catalytic properties of HRP-mimicking DNAzymes for signal amplification. Under optimal conditions, the detection limit of caspase 3 was 0.

A ratiometric fluorescent probe for hydrophobic proteins in aqueous solution based on aggregation-induced emission.

A novel fluorescent probe 1 is reported here with ratiometric response to hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction. Probe 1 underwent deprotonation in aqueous solution at pH 7.4 and emitted blue fluorescence at 436 nm.

Label-free catalytic and molecular beacon containing an abasic site for sensitive fluorescent detection of small inorganic and organic molecules.

In this work, two methods with complementary features, catalytic and molecular beacon (CAMB) and label-free fluorescent sensors using an abasic site, have been combined into new label-free CAMB sensors that possess advantages of each method. The label-free method using a dSpacer-containing molecular beacon makes CAMB more cost-effective and less interfering with the catalytic activity, while CAMB allows the label-free method to use true catalytic turnovers for signal amplifications, resulting in a new label-free CAMB sensor for Pb(2+) ion, with a detection limit of 3.8 nM while maintaining the same selectivity.

A new coumarin-based fluorescence turn-on chemodosimeter for Cu2+ in water.

A highly selective and sensitive coumarin-based chemodosimeter 1 for Cu(2+) in water is reported in this work. 1 was designed and facilely synthesized by a one-step reaction with coumarin as a fluorophore and 2-picolinic acid as the binding moiety, which showed very week fluorescence in buffer solution, and its fluorescence was considerably enhanced by the addition of Cu(2+) at room temperature in 5 min. Mechanism study suggested that Cu(2+) promoted the hydrolysis of 1 via the catalytic sensing cycle, generating a highly fluorescent product 7-hydroxycoumarin with fluorescence signal greatly amplified.