4,5-Diaminofluorescein (DAF-2) is widely used for detection and imaging of NO based on its sensitivity, noncytotoxicity, and specificity. In the presence of oxygen, NO and NO-related reactive nitrogen species nitrosate 4,5-diaminofluorescein to yield the highly fluorescent DAF-2 triazole (DAF-2T). However, as reported here, the DAF-2 reaction to form a fluorescent product is not specific to NO because it reacts with dehydroascorbic acid (DHA) and ascorbic acid (AA) to generate new compounds that have fluorescence emission profiles similar to that of DAF-2T. When DHA is present, the formation of DAF-2T is attenuated because the DHA competes for DAF-2, whereas AA decreases the nitrosation of DAF-2 to a larger extent, possibly because of additional reducing activity that affects the amount of available N 2 O 3 from the NO. The reaction products of DAF-2 with DHA and AA have been characterized using capillary electrophoresis with laser-induced fluorescence detection and electrospray mass spectrometry. The reactions of DAF-2 with DHA and AA are particularly significant because DHA and AA often colocalize with nitric-oxide synthase in the central nervous, cardiovascular, and immune systems, indicating the importance of understanding this chemistry.NO is involved in a variety of important biological functions in the cardiovascular system, the central and peripheral nervous system, the reproductive system, and the immune system (1-6). NO is normally generated via an enzymatically regulated pathway with the conversion of L-arginine to citrulline by a family of at least three distinct nitric-oxide synthase (NOS) 1 enzymes, the neuronal, inducible, and endothelial NOS forms (or NOS-I, -II, and -III) (7-9). Endothelial and neuronal NOS, also named constitutive NOS, are calcium-dependent. Although cells expressing constitutive NOS generally produce small amounts of NO (submicromolar at the cellular level), inducible NOS, which is synthesized in immune-competent cells when stimulated by cytokines, endotoxins, and other biologically active compounds, is calcium-independent and produces NO at higher levels (1-10 M in microphages) (10). Although in situ and immunohistochemical techniques allow one to determine whether NOS is present in a particular tissue, whether the NOS is actively producing NO under specific conditions and the amount of NO produced are important questions to answer to understand the physiological roles of NOS.Direct detection (or imaging) of NO production in a biological system was unsatisfactory until the development of a series of fluorescent indicators for NO, the diaminofluoresceins (DAFs) in 1998 by the Nagano group (11). In the presence of oxygen, NO nitrosates DAFs to produce the highly fluorescent triazofluoresceins. DAFs provide the advantages of sensitivity (detection limits of 5 nM), simple protocols, and noncytotoxicity, and they are also believed to offer high specificity to NO. Since then, an increasing number of researchers have used them for NO detection and NO imaging (10, 12).The specificity...

A miniaturized lead sensor has been developed by combining a lead-specific DNAzyme with a microfabricated device containing a network of microfluidic channels that are fluidically coupled via a nanocapillary array interconnect. A DNAzyme construct, selective for cleavage in the presence of Pb 2+ and derivatized with fluorophore (quencher) at the 5′ (3′) end of the substrate and enzyme strands, respectively, forms a molecular beacon that is used as the recognition element. The nanocapillary array membrane interconnect is used to manipulate fluid flows and deliver the small-volume sample to the beacon in a spatially confined detection window where the DNAzyme is interrogated using laser-induced fluorescence detection. A transformed log plot of the fluorescent signal exhibits a linear response (r 2 ) 0.982) over a Pb 2+ concentration range of 0.1-100 µM, and a detection limit of 11 nM. The sensor has been applied to the determination of Pb 2+ in an electroplating sludge reference material, the result agreeing with the certified value within 4.9%. Quantitative measurement of Pb 2+ in this complex sample demonstrates the selectivity of this sensor scheme and points favorably to the application of such technologies to analysis of environmental samples. The unique combination of a DNAzyme with a microfluidic-nanofluidic hybrid device makes it possible to change the DNAzyme to select for other compounds of interest, and to incorporate multiple sensing systems within a single device for greater flexibility. This work represents the initial steps toward creation of a robust field sensor for lead in groundwater or drinking water.

Chitosan is a naturally occurring polysaccharide, which has exhibited antioxidant, antimicrobial, and anti-cancer activities among others. Modification of chitosan by grafting phenolic compounds is a good strategy for improvement of bioactivities of chitosan. We investigated the anti-inflammatory action of gallic acid-grafted-chitosan (GAC) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. GAC inhibited the production of nitric oxide (NO) and prostaglandin E2 (PGE2) by inhibiting inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-stimulated RAW264.7 macrophages. GAC also suppressed the production and mRNA expression of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). GAC inactivated nuclear factor-κB (NF-κB) via inhibiting the phosphorylation and degradation of the NF-κB inhibitor, IκB. In addition, GAC suppresses the activation of activator protein-1 (AP-1) through the phosphorylation of mitogen-activated protein kinase (MAPK) such as extracellular signal-regulated kinase (ERK1/2), p38 MAPK, and c-Jun N-terminal kinase/stress-activated protein kinase (JNK). These results suggest that GAC has the potential anti-inflammatory action by downregulating transcriptional factors (NF-κB and AP-1) through MAPK signaling pathways.