Bailing Liu

Technological Advances in High-Throughput Screening

High-throughput screening (HTS) is the process of testing a large number of diverse chemical structures against disease targets to identify ‘hits’. Compared to traditional drug screening methods, HTS is characterized by its simplicity, rapidness, low cost, and high efficiency, taking the ligand-target interactions as the principle, as well as leading to a higher information harvest. As a multidisciplinary field, HTS involves an automated operation-platform, highly sensitive testing system, specific screening model (in vitro), an abundant components library, and a data acquisition and processing system. Various technologies, especially the novel technologies such as fluorescence, nuclear-magnetic resonance, affinity chromatography, surface plasmon resonance, and DNA microarray, are now available, and the screening of more than 100 000 samples per day is already possible.Fluorescence-based assays include the scintillation proximity assay, time-resolved energy transfer, fluorescence anisotropy, fluorescence correlation spectroscopy, and fluorescence fluctuation spectroscopy. Fluorescence-based techniques are likely to be among the most important detection approaches used for HTS due to their high sensitivity and amenability to automation, giving the industry-wide drive to simplify, miniaturize, and speed up assays. The application of NMR technology to HTS is another recent trend in drug research. One advantage afforded by NMR technology is that it can provide direct information on the affinity of the screening compounds and the binding location of protein. The structure-activity relationship acquired from NMR analysis can sharpen the library design, which will be very important in furnishing HTS with well-defined drug candidates. Affinity chromatography used for library screening will provide the information on the fundamental processes of drug action, such as absorption, distribution, excretion, and receptor activation; also the eluting curve can give directly the possibility of candidate drug.SPR can measure the quantity of a complex formed between two molecules in real-time without the need for fluorescent or radioisotopic labels. SPR is capable of characterizing unmodified biopharmaceuticals, studying the interaction of drug candidates with macromolecular targets, and identifying binding partners during ligand fishing experiments. DNA microarrays can be used in HTS be used to further investigate the expression of biological targets associated with human disease, which then opens new and exciting opportunities for drug discovery. Without doubt, the addition of new technologies will further increase the application of HTS in drug screening and its related fields.

Application of Scintillation Proximity Assay in Drug Discovery

Scintillation proximity assay (SPA), characterized by its speed, sensitivity, reliability, and the fact that no separation step is required, has become an important technique in high-throughput screening (HTS) for new drugs, and for investigating their biological interactions. The SPA technique now plays a key role in HTS, in that it can be used in many assay formats including radioimmunoassays (RIAs), ligand-receptor binding assays, and enzyme assays. The SPA-based enzyme assay is usually designed in three formats corresponding to different enzymes: signal removal format for hydrolytic enzymes, signal addition format for polymerase and transferase enzymes, and product capture format for antibodies, DNA probes, receptors or other specific binding proteins. The use of SPA in RIAs has been facilitated by new carriers, such as membranes that can be configured in various shapes and sizes, allowing the assay to be performed on samples from many sources including tissue, serum, plasma or cells. This review presents the principles of SPA, discusses supporting materials and quenching effects, as well as detailed examples of the latest advances.

The Preparation and Enzyme Immobilization of Hydrophobic Polysiloxane Supports

Enzymes are versatile biocatalysts and find increasing applications in many areas. The major advantages of using enzymes in biocatalytic transformations are their chemo-, regio-, and stereospecificity, as well as the mild reaction conditions that can be used. However, even when an enzyme is identified as being useful for a given reaction, its application is often hampered by its lack of long-term stability under process conditions, and also by difficulties in recovery and recycling. For ease of application and stabilization purposes, enzymes are often immobilized on solid supports. Among support matrices, hydrophobic biomaterials have been extensively used as supports for enzyme immobilization because the hydrophobic interactions not only can effectively increase the amount of enzyme immobilization, but also exhibit higher activity and retention of activity compared with hydrophilic supports. On the other hand, polysiloxane can evidently increase the amount of enzyme immobilization because of its hydrophobicity and strong affinity with enzyme. Therefore, this research details the first preparation and use of a hydrophobic polysiloxane support for enzyme immobilization in which the structural and functional characteristics of new supports have been investigated by using glucose oxidase (GOD) and a simple Fentons assay method, and extremely interesting features were revealed. The results showed that the amount of GOD immobilization and the stability of GOD loaded, which are fundamental properties for enzyme separation and purification, can be significantly improved by adsorption. Moreover, the results indicated that hydrophobic polysiloxane supports can effectively increase the enzymatic affinity and durability of GOD, and decrease the rate of GOD desorbed.

Synthesis and Sand-Fixing Property of Cationic Poly(Vinyl Acetate-Butyl Acrylate-DMC) Copolymer Emulsions

The novel cationic poly(vinyl acetate-butyl acrylate-DMC) copolymer emulsion used as chemical sand-fixing material was successfully prepared. The morphology, structure and composition, and thermal property of the emulsion were characterized by TEM, FTIR and DSC, respectively. The correlations between the concentration of prepared emulsion and the sand-fixing properties were investigated. The results show that the emulsion could significantly improve the water retaining, compressive strength and anti-wind erosion ability to prevent the loose sand surface from forming a sand dune in the wind erosion conditions. Also, the prepared emulsion has good thermal and freeze-thaw stabilities to withstand the changes in temperature.

Chemical sand stabilization: A review of material, mechanism, and problems

Chemical sand stabilization has potential for desertification control and this method is characterized by its speed and convenience in operation compared with other stabilization technologies. The materials used in chemical sand stabilization are the key point of this technology and various materials have been developed and investigated. In this review, we present the classification, performance of the materials adopted in sand stabilization, and their stabilizing mechanism as well. We wish to find the relationship between the material structures and their application performance to prevent blind use. However, the consideration for the materials used in chemical sand stabilization is far behind the requirement of desertification control, thus greater efforts have to be paid in this area.

Preparation and Characterization of PDMS-PMMA Interpenetrating Polymer Networks with Indistinct Phase Separation

This paper describes the preparation and characterization of the interpenetrating polymer networks (IPNs) of polydimethylsiloxane-polymethyl methacrylate (PDMS-PMMA) via 3-(methacryloxypropyl)-trimethoxy-silane (MPS) as the crosslinking agent. The structure of synthesized IPNs was characterized by 1HNMR, DSC, FT-IR, XPS, SEM and AFM, respectively. The experimental results show that, with the method adopted in this preparation process, the phase separation between PDMS and PMMA in PDMS-PMMA IPNs has been reduced to a smaller extent than other previous reports.

Preparation and Flammability of a Flame-Retardant Poly(Butyl Acrylate-Vinyl Acetate) System Based on Gemin-Surfactant Modified Montmorillonite and Ammonium Polyphosphate

Gemin-surfactant modified montmorillonite (G-MMT) was successfully prepared by an ion exchange reaction and characterized via Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The P(BA-VAc)/G-MMT emulsion was prepared via an in-situ polymerization method using potassium persulfate (K2S2O8, KPS) as an initiator. Ammonium polyphosphate (APP) was introduced for obtaining P(BA-VAc)/APP/G-MMT flame-retardant latex with a constant total content of 15 wt% of APP and G-MMT in P(BA-VAc). The flame retardancy and thermal behavior of the latex films were investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and thermal gravimetric analysis (TG/DTA). Compared with the P(BA-VAc)/APP composite, the LOI value of P(BA-VAc)/APP/G-MMT containing 0.5 wt% G-MMT at the same total additive loading increased to 29.1 from 20.0 and its UL-94 increased from no rating to V-0. Thermal gravimetric (TG) data showed that the amount of residues increased significantly with the loading of G-MMT. In addition, the LOI values increased with the increase in char residues. The morphology and microstructure of the residues generated during LOI testing were investigated by scanning electron microscopy (SEM). The outer surfaces of P(BA-VAc)/APP/G-MMT charred layers were more continuous and compact than those of P(BA-VAc)/APP.

Synergistic Effect Between Organically Modified Montmorillonite and Ammonium Polyphosphate on Thermal and Flame-Retardant Properties of Poly(Butyl Acrylate/Vinyl Acetate) Copolymer Latex

Hexadecyl trimethyl ammonium bromide modified montmorillonite (1631-MMT) was successfully synthesized via an ion exchange reaction and characterized through Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Various poly(butyl acrylate/vinyl acetate) P(BA-VAc) copolymer P(BA-VAc)/1631-MMT emulsions were prepared via in-situ polymerization method using potassium persulphate (K2S2O8, KPS) as an initiator. Ammonium polyphosphate (APP) was introduced for obtaining P(BA-VAc)/APP/1631-MMT flame-retardant latex. The flame retardancy and thermal behavior of the latex films were investigated through limiting oxygen index (LOI) and vertical burning test (UL-94) and thermo-gravimetric analysis (TGA/DTA [differential thermal analysis]) analysis. Compared with the P(BA-VAc)/APP composite, the LOI value of P(BA-VAc)/APP/1631-MMT sample was increased from 27.7 to 30.3 with a concentration of 1631-MMT 0.5 wt% in composition, and its UL-94 was raised to V-0 from no rating. TG date showed that the amount of residues increased significantly when 1631-MMT was added. The morphology and microstructure of the residues generated during LOI testing were investigated by scanning electron microscopy (SEM). The outer surface of the P(BA-VAc)/APP/1631-MMT charred layer was more continuous and compact than that of P(BA-VAc)/APP.

Scale inhibitors with a hyper-branched structure: preparation, characterization and scale inhibition mechanism

In order to improve the scale inhibition efficiency of existing scale inhibitors for industrial water and to reduce the phosphorus pollution of water bodies, a new type of scale inhibitor with a hyper-branched structure has been developed in this study. First, an AB′ type of functional monomer (AMA) was synthesized from maleic anhydride (MAH) and propylene glycol, then copolymerized with monomer B (MAH) through radical polymerization, resulting in a hyper-branched polycarboxylic acid. The synthesis conditions, such as reaction temperature and time, monomer ratio and initiator dosage, have been investigated for obtaining the expected hyper-branched polymer with good scale inhibition performance. The scale inhibition efficiency of the obtained products was determined according to their resistance to the crystallization of calcium sulfate and calcium carbonate under the optimal application conditions. The experimental results show that the hyper-branched polycarboxylic acid provides a scale inhibiting efficiency for CaCO3 and CaSO4 as high as 95.2% and 92.3%, respectively. In addition, XRD analysis showed that the good scale inhibition of the hyper-branched polycarboxylic acid is attributed to its ability to inhibit and destroy the formation of crystals, changing the crystal forms of the calcium scale. This conclusion indicates that the prepared hyper-branched polycarboxylic acid has great application potential in the treatment of industrial water.

The Influence of 2-Hydroxyethyl Acrylate on the Properties of Cationic Poly(VAc-BA-HEA) Terpolymer Latexes

The cationic poly(vinyl acetate-butyl acrylate-2-hydroxyethyl acrylate) terpolymer latexes (Poly(VAc-BA-HEA)) were successfully prepared using the emulsion polymerization. The structure and composition, morphology, and thermal property of the latexes were characterized by FTIR, TEM and DSC, respectively. Also, the correlations between the particle size, zeta potential, viscosity and water absorption of prepared cationic latexes and 2-hydroxyethyl acrylate concentration were established. The results show that the concentration of 2-hydroxyethyl acrylate could affect the properties of the latexes significantly. This offers an attractive opportunity for adjusting the particle size and viscosity of latexes over a wide range by feeding 2-hydroxyethyl acrylate with varying concentration.