Minghuo Wu

P-Glycoprotein Antibody Functionalized Carbon Nanotube Overcomes the Multidrug Resistance of Human Leukemia Cells

Multidrug resistance (MDR), which is related to cancer chemotherapy, tumor stem cells, and tumor metastasis, is a huge obstacle for the effective cancer therapy. One of the underlying mechanisms of MDR is the increased efflux of anticancer drugs by overexpressed P-glycoprotein (P-gp) of multidrug resistant cells. In this work, the antibody of P-gp (anti-P-gp) functionalized water-soluble single-walled carbon nanotubes (Ap-SWNTs) loaded with doxorubicin (Dox), Dox/Ap-SWNTs, were synthesized for challenging the MDR of K562 human leukemia cells. The resulting Ap-SWNTs could not only specifically recognize the multidrug resistant human leukemia cells (K562R), but also demonstrate the effective loading and controllable release performance for Dox toward the target K562R cells by exposing to near-infrared radiation (NIR). The recognition capability of Ap-SWNTs toward the K562R cells was confirmed by flow cytometry (FCM) and confocal laser scanning microscopy (CLSM). The binding affinity of Ap-SWNTs toward drug-resistant K562R cells was ca. 23-fold higher than that toward drug-sensitive K562S cells. Additionally, CLSM indicated that Ap-SWNTs could specifically localize on the cell membrane of K562R cells and the fluorescence of Dox in K562R cells could be significantly enhanced after the employment of Ap-SWNTs as carrier. Moreover, the composite of Dox and Ap-SWNTs (Dox/Ap-SWNTs) expressed 2.4-fold higher cytotoxicity and showed the significant cell proliferation suppression toward K562R leukemia cells (p < 0.05) as compared with free Dox which is popularly employed in clinic trials. These results suggest that the Ap-SWNTs are the promising drug delivery vehicle for overcoming the MDR induced by the overexpression of P-gp on cell membrane. Ap-SWNTs loaded with drug molecules could be used to suppress the proliferation of multidrug resistant cells, destroy the tumor stem cells, and inhibit the metastasis of tumor.

Polyhedral Oligomeric Silsesquioxane as a Cross-linker for Preparation of Inorganic−Organic Hybrid Monolithic Columns

An inorganic-organic hybrid monolithic capillary column was synthesized via thermal free radical copolymerization within the confines of a capillary using a polyhedral oligomeric silsesquioxane (POSS) reagent as the inorganic-organic hybrid cross-linker and a synthesized long carbon chain quaternary ammonium methacrylate of N-(2-(methacryloyloxy)ethyl)-dimethyloctadecylammonium bromide (MDOAB) as the organic monomer. The preparation process was as simple as pure organic polymer-based monolithic columns instead of using POSS as the nanosized inorganic-organic hybrid blocks (cross-linker) of the monolithic matrix. The pore properties and permeability could be tuned by the composition of the polymerization mixture. The characterization and evaluation results indicated that the synthesized MDOA-POSS hybrid monolith possessed the merits of organic polymer-based monoliths and silica-based monoliths with good mechanical and pH (pH 1-11) stabilities, which may be attributed to the incorporation of the rigid nanosized silica core of POSS. Column efficiencies of 223 000 and 50 000 N/m were observed in capillary electro-driven chromatography (CEC) and mu-HPLC, respectively. Peptides and standard proteins were baseline separated by this hybrid column in CEC and mu-HPLC, respectively, as well. The separation of bovine serum albumin (BSA) tryptic digest was also attempted to show its potential application in proteome analysis.

Coupling Strong Anion-Exchange Monolithic Capillary with MALDI-TOF MS for Sensitive Detection of Phosphopeptides in Protein Digest

Protein phosphorylation is one of the most biologically relevant and ubiquitous post-translational modifications. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a powerful tool for the analysis of protein phosphorylation by detection of phosphopeptides in phosphoprotein digest. Enrichment of phosphopeptides by immobilized metal ion affinity chromatography (IMAC) or metal oxide affinity chromatography (MOAC) followed with MALDI analysis is the common approach. However, the pH for loading and elution of phosphopeptides is incompatible with protein digestion as well as the preparation of the MALDI matrix solution. Therefore, some pretreatment steps, such as pH adjustment and desalting, are required, which make the approach tedious and insensitive. In this study, a strong anion-exchange (SAX) capillary monolith was prepared to enrich phosphopeptides from protein digest for MALDI-TOF MS analysis. It was found that phosphopeptides could be specifically retained on the SAX column at high pH around 8 and could be eluted by 5% formic acid. Thus, the protein digests without any pretreatment could be loaded onto the SAX column under basic pH condition; after removing nonphosphopeptides by washing, the bound phosphopeptides could be eluted directly onto a MALDI target and analyzed by MALDI-TOF MS. This approach significantly simplified the analytical procedures and reduced the sample loss. Because of the excellent MALDI MS compatible procedure and the microscale SAX column, a detection limit as low as 50 amol for the analysis of phosphopeptides from beta-casein digest was achieved. To circumvent the inconvenience of the sample loading, a new simple sample introducing method based on capillary action was proposed, which further reduced the detection limit to 10 amol.

Preparation and application of organic-silica hybrid monolithic capillary columns†

Organic‐silica hybrid monolithic columns have drawn more and more attention due to the ease of preparation and good mechanical stability in recent years. Many synthetic approaches have been developed and a variety of hybrid monolithic capillary columns have been prepared. The sol–gel process is well recognized in the fabrication of hybrid monolithic columns, which can be mainly classified as one‐step, acid/base two‐step procedures. The new approaches such as the “one‐pot” and nano‐scaled inorganic–organic hybrid reagent of polyhedral oligomeric silsesquioxane used as a cross‐linker have also emerged for the preparation of hybrid monolithic columns. The applications of the organic‐silica hybrid monolithic capillary columns for capillary electrochromatography, micro high‐performance liquid chromatography, solid‐phase micro‐extraction and enzymatic reactor etc. are included in this review.

Halobenzoquinones in Swimming Pool Waters and Their Formation from Personal Care Products

Halobenzoquinones (HBQs) are a class of disinfection byproducts (DBPs) of health relevance. In this study, we aimed to uncover which HBQs are present in swimming pools. To achieve this goal, we developed a new method capable of determining eight HBQs while overcoming matrix effects to achieve reliable quantification. The method provided reproducible and quantitative recovery (67-102%) and detection limits of 0.03-1.2 ng/L for all eight HBQs. Using this new method, we investigated water samples from 10 swimming pools and found 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) in all the pools at concentrations of 19-299 ng/L, which was as much as 100 times higher than its concentration in the input tap water (1-6 ng/L). We also identified 2,3,6-trichloro-(1,4)benzoquinone (TriCBQ), 2,3-dibromo-5,6-dimethyl-(1,4)benzoquinone (DMDBBQ), and 2,6-dibromo-(1,4)benzoquinone (2,6-DBBQ) in some swimming pools at concentrations of <0.1-11.3, <0.05-0.7, and <0.05-3.9 ng/L, respectively, but not in the input tap water. We examined several factors to determine why HBQ concentrations in pools were much higher than in the input tap water. Higher dissolved organic carbon (DOC), higher doses of chlorine and higher temperatures enhanced the formation of HBQs in the pools. In addition, we conducted laboratory disinfection experiments and discovered that personal care products (PCPs) such as lotions and sunscreens can serve as precursors to form additional HBQs, such as TriCBQ, 2,6-dichloro-3-methyl-(1,4)benzoquinone (DCMBQ), and 2,3,5,6-tetrabromo-(1,4)benzoquinone (TetraB-1,4-BQ). These results explained why some HBQs existed in swimming pools but not in the input water. This study presents the first set of occurrence data, identification of new HBQ DBPs, and the factors for their enhanced formation in the swimming pools.

Recent progress of chiral monolithic stationary phases in CEC and capillary LC

As the development of monolithic stationary phases in CEC and capillary LC, the monoliths specifically related with the enantioseparations taking the advantages of monolithic stationary phases have attracted increased research interest in this field. This short review describes recent progress with emphasis on the preparation of the chiral monolithic stationary phases along with brief discussion and perspective on the future development of chiral monolithic stationary phases in CEC and capillary LC.

Recent progress of polar stationary phases in CEC and capillary liquid chromatography.

The stationary phases including the nonpolar and polar stationary phases in microscale separations have been greatly developed. This review describes the recent progress of the polar stationary phases (PSPs) with the focus on their preparation and the interesting applications in the field of CEC and capillary liquid chromatography (CLC) covering the literatures from the middle of 2006 to the middle of 2008. The PSPs described herein were summarized into three types as open‐tubular, particle‐packed and monolithic stationary phases for either CEC or CLC, and the separation mechanisms are of hydrophilic interaction, chiral selection, ion‐exchange and/or electrostatic interaction, etc. After overviewing the literatures published in the last 2 years, the research efforts on PSPs for CEC and CLC have been remaining in the fabrication of open‐tubular and monolithic capillary columns; whereas, the research endeavor of PSPs on particulate‐packed format seemed to decline most likely due to the commercial availability of various packing particles for CEC and CLC.

A mesoporous silica nanoparticles immobilized open-tubular capillary column with a coating of cellulose tris(3;5-dimethylphenyl-carbamate) for enantioseparation in CEC

An approach of immobilizing mobile crystalline material (MCM)‐41 mesoporous silica nanoparticles on the inner wall of an open‐tubular (OT) capillary as the support for coating chiral selector of cellulose tris(3,5‐dimethylphenyl‐carbamate) (CDMPC) was carried out. By taking advantage of the improved phase ratio of OT capillary with the immobilization of MCM‐41 mesoporous material, the cellulose derivative of CDMPC as the chiral selector was simply coated on the MCM‐41 nanoparticle layer via the hydrogen‐bonding interaction, and the enantioseparation was successively carried out. Eight pairs of acidic, neutral and basic enantiomers were resolved in capillary electrochromatography or capillary liquid chromatography mode. The concentration of CDMPC for coating was systematically investigated to obtain the optimized chromatographic properties on enantioseparation by controlling the supposed film thickness of CDMPC on MCM‐41 nanoparticle layer. Comparing with a bare fused silica capillary column coated with CDMPC under the same coating procedure as MCM‐41‐modified capillary did, the MCM‐41‐modified capillary column offered much higher enantioselectivity. This result indicated the significance of using the mesoporous nanoparticles as the electrochromatographic support to enhance the phase ratio of OT capillary column in capillary electrochromatography and capillary liquid chromatography. For investigating the effect of experimental conditions on the enantioseparation with this prepared OT capillary column, the content of organic modifier acetonitrile in the mobile phase was thus extensively evaluated to achieve a better chiral separation.

Polyacrylamide-based monolithic capillary column with coating of cellulose tris(3,5-dimethylphenyl-carbamate) for enantiomer separation in capillary electrochromatography

A hydrophilic chiral capillary monolithic column for enantiomer separation in CEC was prepared by coating cellulose tris(3,5‐dimethylphenyl‐carbamate) (CDMPC) on porous hydrophilic poly(acrylamide‐co‐N,N′‐methylene‐bisacrylamide) (poly(AA‐co‐MBA)) monolithic matrix with confine of a fused‐silica capillary. The coating conditions were optimized to obtain a stable and reproducible chiral stationary phase for CEC. The effect of organic modifier of ACN in aqueous mobile phase for the enantiomer separation by CEC was investigated, and the significant influence of ACN on the enantioresolution and electrochromatographic retention was observed. Twelve pairs of enantiomers including acidic, neutral, and basic analytes were tested and nine pairs of them were baseline‐enantioresolved with acidic and basic aqueous mobile phases. A good within‐column repeatability in retention time (RSD = 2.4%) and resolution (RSD = 3.2%) was obtained by consecutive injections of a neutral compound, benzoin, on a prepared chiral monolithic column, while the between‐column repeatability in retention time (RSD = 6.4%) and resolution (RSD = 9.6%) was observed by column‐to‐column examination. The prepared monolithic stationary phase showed good stability in either acidic or basic mobile phase.

The synthesis of chloropropyl-functionalized silica hybrid monolithic column with modification of N,N-dimethyl-N-dodecylamine for capillary electrochromatography separation☆

A chloropropyl-functionalized silica (CP-silica) hybrid monolithic column was synthesized within the confines of a capillary via the sol-gel process using tetramethoxysilane (TMOS) and (3-chloropropyl)-trimethoxysilane (CPTMS) as the precursors. The resulting CP-silica hybrid monolith inside the capillary showed homogeneous macroporous morphology and was well attached to the inner wall of the capillary. The obtained CP-silica hybrid monolithic capillary column demonstrated the inherent hydrophobic property and could be applied as a reversed-phase stationary phase in CEC directly. Due to the great chemical reactivity of the incorporated chloro groups on the hybrid silica monolithic matrix, the chloropropyl moieties on the surface of the hybrid silica monolith matrix could be conveniently further modified by a tertiary amine of N,N-dimethyl-N-dodecylamine (DMDA) via the nucleophilic substitution reaction at 70 degrees C to introduce a dodecyl groups (C12) onto the CP-silica hybrid monolithic matrix. The resulting C12-silica hybrid monolithic column not only demonstrated the significantly enhanced hydrophobic property in the separation of alkylbenzenes in reversed-phase capillary electrochromatography (RP-CEC), but also the strong electroosmotic flow (EOF) in a wide pH range. Five alkylbenzenes could be baseline separated in 3 min with column efficiency ranging from 189700 to 221000 N/m with a 70% ACN running buffer in CEC.