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Water soluble porphyrins have many perfect analytical figures of merit. A water-soluble sulfonated porphyrin (H2TEHPPS) was used to build a novel platform for sensitive assays of hydrogen peroxide and glucose based on the different effects of Fe2+ and Fe3+ on H2TEHPPS. H2O2 or Fe2+ alone cannot induce a fluorescence change in H2TEHPPS, but Fe3+ can quench the fluorescence of H2TEHPPS significantly. Interestingly, glucose is oxidized to gluconolactone by GOD and generates an equivalent hydrogen peroxide, and the produced H2O2 also oxidizes Fe2+ to Fe3+ and causes the fluorescence quenching of H2TEHPPS. According to this, a sensitive sensor for hydrogen peroxide and glucose has been demonstrated, which can determine H2O2 and glucose in a relative simple and sensitive way. The detection limits were 1.3 × 10−7 M and 3.2 × 10−7 M for H2O2 and glucose, respectively. In addition, the glucose in serum samples was determined successfully using this sensing platform. It is also noteworthy that H2O2 can be released in almost all oxidations catalyzed by oxidases, which suggests that this newly proposed H2O2 probe can be readily extended to sense other oxidases and their specific substrates. [ABSTRACT FROM AUTHOR]

A fluorescent probe for fulfilling a lysosome targeting function in hypoxic tumor cells is reported, wherein azoreductase triggers a dramatic fluorescence enhancement and specific imaging of lysosomes in hypoxic cancer cells.

A metal-to-metal relay recognition was discovered with sequence specificity via a fluorescence 'off-on-off' phenomenon. We present here the synthesis of a new N,N-bis(2-pyridylmethyl)amine-based fluorescent sensor termed NBPA and its application as a selective relay probe for sensing of free trace zinc and copper ions. The addition of Zn(2+) to NBPA causes a drastic enhancement of fluorescent intensity by the formation of a 1 : 1 NBPA-Zn(2+) complex whereas other cations have no response. Moreover, Cu(2+) can induce fluorescence quenching in the NBPA-Zn(2+) system by the formation of a 1 : 1 NBPA-Cu(2+) complex confirmed by Job's Plot. The signal change of the sensor is based on the chelation-enhanced fluorescence (CHEF) effect of NBPA-Zn(2+) with the inhibition of the photoinduced electron transfer (PET) effect and the paramagnetic nature of Cu(2+) to the NBPA-Zn(2+) system. Under optimized conditions, the fluorescence intensity is linear to the concentration of Zn(2+) and Cu(2+) separately, exhibiting good linearities from 1.0 × 10(-6) M to 8.0 × 10(-6) M and 1.0 × 10(-6) M to 1.0 × 10(-5) M (R(2) = 0.9996 and R(2) = 0.9914) with detection limits of 7.89 × 10(-7) M and 1.27 × 10(-7) M, respectively. Furthermore, the rapid, selective feature enables the proposed sensor to be promising in monitoring Zn(2+) and Cu(2+) in biological and environmental research with good accuracy and precision.

A novel geometry-independent neutral desorption (GIND) device was successfully developed, which made neutral desorption (ND) sampling easier and more robust on virtually all types of surfaces. The GIND device features a small air-tight enclosure with fixed space between the ND gas emitter, the sample surface, and the sample collector. Besides easy fabrication and convenient use, this configuration facilitates efficient neutral sample transfer and results in high sensitivity by preventing material loss during the ND process. The effects of various operating parameters of the GIND device such as desorption gas composition, surface wetness, gas flow rate, distance between the surface and the gas emitter, internal diameter of the sample outlet, and GIND device material were experimentally investigated. By using the GIND device, trace amounts of typical explosives such as TNT, RDX, HMX, TATP, etc., were successfully sampled from many different kinds of surfaces, including human skin, glove, glass, envelope, plastic, leather, glass, and clothes. GIND-sampled explosives were detected by multiple-stage extractive electrospray ionization mass spectrometry (EESI-MS). Ion/molecule reactions of explosives such as RDX and TATP were implemented in the EESI source for the rapid detection with enhanced sensitivity and specificity. The typical time for a single sample analysis was a few seconds. Successful transportation of the neutral analytes over a distance longer than 10 m was demonstrated, without either significant signal loss or serious delay of signal response. The limit of detection for these explosives in the study was in the range of ca. 59-842 fg (S/N = 3, n = 8) on various surfaces. Acceptable relative standard deviation (RSD) values (ca. 4.6-10.2%, n = 8) were obtained for all the surfaces tested, showing the successful sampling of trace non-volatile explosive compounds (sub-picogram) by the GIND device for the EESI mass spectrometric analysis.