Use of Gold Nanoparticles To Enhance Capillary Electrophoresis

We describe here the use of gold nanoparticles to manipulate the selectivity between solutes in capillary electrophoresis. Two different gold-based nanoparticles were added to the run buffer. In one case, the nanoparticles were stabilized with citrate ions, but in another study, the gold nanoparticles were capped with mercaptopropionate ions (thiol-stablized). Citrate-stabilized gold nanoparticles were used in conjunction with capillaries treated with poly(diallyldimethylammonium chloride) (PDADMAC). The positively charged PDADMAC layer on the capillary walls adsorbs the negatively charged gold nanoparticles. The model solutes that were used to study the effect of the presence of the citrate-stabilized gold nanoparticles are structural isomers of aromatic acids and bases. The presence of the PDADMAC layer and the PDADMAC plus the gold nanoparticles changes both the electroosmotic mobility and the observed mobility of the solutes. These changes in the mobilities influence the observed selectivities and the separations of the system. Thiol-stabilized gold nanoparticles were used without PDADMAC in the capillary. The model solutes studied in this part are various aromatic amines. In this case as well, the presence of the gold nanoparticles modifies the electroosmotic mobility and the observed mobility of the solutes. These changes in the mobilities are manifested in selectivity alterations. The largest change in the selectivities occurs at low concentrations of the gold nanoparticles in the run buffer. The presence of nanoparticles improves the precision of the analysis and increases the separation efficiency. Nanodispersions have attracted extensive attention in various fields of physics, biology, and chemistry. [1][2][3][4][5] Physicists and chemists are intrigued by the gradual transition of the nanomaterial properties from molecule-like to those of solid-state properties by a change of a single variable, the particle size. This property has practical and future applications for nonlinear optics and electronics. The large surface area of nanomaterials intrigues chemical engineers and catalysis scientists. Surprisingly, very little research has been devoted to the application of nanoparticles for chemical separation. In this work, we demonstrate the utility and versatility of organically modified gold nanoparticles in capillary electrophoresis (CE) separations. The nanoparticles serve as large surface area platforms for organofunctional groups that interact with the capillary surface, the analytes, or both. Thus, the apparent mobilities of target analytes, as well as the electroosmotic flow, can be altered leading to enhanced selectivities. Separation of various benzene derivatives demonstrates these capabilities. Metallic nanodispersions can be prepared in aqueous and organic solvents using diverse procedures. 1,2,6-9 Nanodispersions can be stabilized in organic solvents by the solvent itself, 10 by the addition of long chain surfactants, 11,12 or by specific ligands. 13 Stabilization of metal nanodispersions in aqueous solutions is somewhat more complicated. Several successful stabilization methods are available that are based on capping of the metal nanoparticles (e.g., citrate, 6 3-mercaptopropionate, 1

Increasing the Sensitivity and Single-Base Mismatch Selectivity of the Molecular Beacon Using Graphene Oxide as the "Nanoquencher"

Here, we report a novel, highly sensitive, selective and economical molecular beacon using graphene oxide as the "nanoquencher". This novel molecular beacon system contains a hairpin-structured fluorophore-labeled oligonucleotide and a graphene oxide sheet. The strong interaction between hairpin-structured oligonucleotide and graphene oxide keep them in close proximity, facilitating the fluorescence quenching of the fluorophore by graphene oxide. In the presence of a complementary target DNA, the binding between hairpin-structured oligonucleotide and target DNA will disturb the interaction between hairpin-struclured oligonucleotide and graphene oxide, and release the oligonucleotide from graphene oxide, resulting in restoration of fluorophore fluorescence. In the present study, we show that this novel graphene oxide quenched molecular beacon can be used to detect target DNA with higher sensitivity and single-base mismatch selectivity compared to the conventional molecular beacon.National Natural Science Foundation of China [20775019, 20975023, 20735002]; National Basic Research Program of China [2010CB732403

Bright and sensitive ratiometric fluorescent probe enabling endogenous FA imaging and mechanistic exploration of indirect oxidative damage due to FA in various living systems

As a notorious toxin, formaldehyde (FA) poses an immense threat to human health. Aberrantly elevated FA levels lead to serious pathologies, including organ damage, neurodegeneration, and cancer. Unfortunately, current techniques limit FA imaging to general comparative studies, instead of a mechanistic exploration of its biological role, and this is presumably due to the lack of robust molecular tools for reporting FA in living systems. More importantly, despite being reductive, FA, however, can induce oxidative damage to organisms, thus providing a challenge to the mechanistic study of FA using fluorescence imaging. Herein, we presented the design and multi-application of a bright sensitive ratiometric fluorescent probe 1-(4-(1H-phenanthro[9,10-d] imidazol-2-yl) phenyl) but-3-en-1-amine (PIPBA). With a p-extended phenylphenanthroimidazole fluorophore and an allylamine group, PIPBA exhibited high quantum yield (phi = 0.62) in blue fluorescent emission and selective reactivity toward FA. When sensing FA, PIPBA transformed to PIBE, which is a product capable of releasing bright green fluorescence (phi = 0.51) with its enhanced intramolecular charge transfer (ICT). Transformation of PIPBA to PIBE contributed to 80 nm of red shift in emission wavelength and a highly sensitive ratiometric response (92.2-fold), as well as a quite low detection limit (0.84 mu M). PIPBA was successfully applied to various living systems, realizing, for the first time, ratiometric quantification (in cells), in vivo imaging (zebrafish), and living tissue imaging (vivisectional mouse under anaesthetic) of endogenous FA that was spontaneously generated by biological systems. Furthermore, with the aid of PIPBA, we obtained visual evidence for the oxidative damage of FA in both HeLa cells and renal tissue of a living mouse. The results demonstrated that FA exerted indirect oxidative damage by interacting with free radicals, thus producing more oxidizing species, which eventually caused aggravated oxidative damage to the organism. The indirect oxidative damage due to FA could be alleviated by an exogenous or endogenous antioxidant. The excellent behaviors of PIPBA demonstrate that a chemical probe can detect endogenous FA in cells/tissue/vivo, promising to be an effective tool for further exploration of the biological mechanism of FA in living systems

Wide-Acidity-Range pH Fluorescence Probes for Evaluation of Acidification in Mitochondria and Digestive Tract Mucosa

The cells control their pH change in a very accurate range. pH plays important roles in cell autophagy and apoptosis. Previous evidence implies that the internal milieu of a tumor is acidified. Although the acidification in cells is investigated, the biological effects from multiple stimulating factors under the complex intracellular environment have not been thoroughly elaborated yet. Currently, there are few pH probes that perform in a wide acidity range, and a probe that is capable of measuring a wide pH range needs to be developed. Herein, we report two new fluorescent probes (BHNBD and CM-BHNBD) for the detection of mitochondrial and intramucosal acidification. The two probes respond to pH via an H+-driven TICT (twist intramolecular charge transfer) mechanism, and they can linearly report pH within a wide pH range: 7.00-2.00 following similar to 148-fold fluorescence increase. The two probes also possess excellent membrane permeability, good photostability, and negligible cytotoxicity. The probes are successfully applied for quantifying the acidification in HeLa cells under the simultaneous stimulation of nutrient deprivation and oxidative stress. Our results demonstrate that the mitochondrial pH is in a dynamic fluctuating state during the acidification process, which suggests a potential cross-talk effect between cell autophagy and apoptosis. We also use the probes for quantifying the intramucosal pH variation in stomach and esophagus via manipulating cellular proton pump. The development of our probes is potentially expected to be used to monitor the intracellular/intramucosal acidification for biomedical research

Rhodamine-based ratiometric fluorescence sensing for the detection of mercury(II) in aqueous solution

Novel ratiometric fluorescent silica nanoparticles with high selectivity towards Hg2+ were synthesized for the detection of Hg2+, Hg2+ promoted the ring opening of spirolactam in the rhodamine moiety grafted onto the silica nanoparticles, resulting in a change in the fluorescence intensity. The fluorescence intensity was proportional to the Hg2+ concentration, and the detection limit (S/N = 3) for Hg2+ was found to be 2.59 x 10(-9) mol L-1 with a linear range from 0.4 to 8 x 10(-7) mol L-1. In addition, the morphology of the silica nanoparticles, the effects of pH and co-existing substances, and the reversibility were investigated. The proposed approach was successfully applied to the determination of Hg2+ in water samples. (C) 2010 Elsevier B.V. All rights reserved.National Nature Scientific Foundation of China (NSFC) [20775064, 20735002]; National Basic Research Program of China [2010CB732402

Visualization of nitroxyl (HNO) in vivo via a lysosome-targetable near-infrared fluorescent probe

We have presented a near-infrared fluorescent probe Lyso-JN for the detection of nitroxyl (HNO) in cells and in vivo. Lyso-JN is comprised of three moieties: an Aza-BODIPY fluorophore, a HNO-response modulator, diphenylphosphino-benzoyl, and a lysosomal locator, alkylmorpholine. The detection mechanism is based on aza-ylide intramolecular ester aminolysis reaction with HNO. The probe holds the ability to capture lysosomal HNO in RAW 264.7 cells, and it is also successfully employed to visualize HNO in mice.We have presented a near-infrared fluorescent probe Lyso-JN for the detection of nitroxyl (HNO) in cells and in vivo. Lyso-JN is comprised of three moieties: an Aza-BODIPY fluorophore, a HNO-response modulator, diphenylphosphino-benzoyl, and a lysosomal locator, alkylmorpholine. The detection mechanism is based on aza-ylide intramolecular ester aminolysis reaction with HNO. The probe holds the ability to capture lysosomal HNO in RAW 264.7 cells, and it is also successfully employed to visualize HNO in mice