Combination of Three Functionalized Temperature-Sensitive Chromatographic Materials for Serum Protein Analysis

We have developed a methodology to capture acidic proteins, alkaline proteins, and glycoproteins separately in mouse serum using a combination of three functionalized temperature-responsive chromatographic stationary phases. The temperature-responsive polymer poly(N-isopropylacrylamide) was attached to the stationary phase, silica. The three temperature-responsive chromatographic stationary phase materials were prepared by reversible addition-fragmentation chain transfer polymerization. Alkaline, acidic, and boric acid functional groups were introduced to capture acidic proteins, alkaline proteins, and glycoproteins, respectively. The protein enrichment and release properties of the materials were examined using the acidic protein, bovine serum albumin; the alkaline protein, protamine; and the glycoprotein, horseradish peroxidase. Finally, the three materials were used to analyze mouse serum. Without switching the mobile phase, the capture and separation of mouse serum was achieved by the combination of three temperature-responsive chromatographic stationary phase materials. On the whole, 313 proteins were identified successfully. The number of different proteins identified using the new method was 1.46 times greater than the number of proteins that has been identified without applying this method. To our knowledge, this method is the first combinatorial use of three functionalized temperature-responsive chromatographic stationary phase silica materials to separate proteins in mouse serum.

Glycopolymer Grafted Silica Gel as Chromatographic Packing Materials

The modification of the surface of silica gel to prepare hydrophilic chromatographic fillers has recently become a research interest. Most researchers have grafted natural sugar-containing polymers onto chromatographic surfaces. The disadvantage of this approach is that the packing structure is singular and the application scope is limited. In this paper, we explore the innovative technique of grafting a sugar-containing polymer, 2-gluconamidoethyl methacrylamide (GAEMA), onto the surface of silica gel by atom transfer radical polymerization (ATRP). The SiO₂-g-GAEMA with ATRP reaction time was characterized by Fourier infrared analysis, Thermogravimetric analysis (TGA), and elemental analysis. As the reaction time lengthened, the amount of GAEMA grafted on the surface of the silica gel gradually increased. The GAEMA is rich in amide bonds and hydroxyl groups and is a typical hydrophilic chromatography filler. Finally, SiO₂-g-GAEMA (reaction time = 24 h) was chosen as the stationary phase of the chromatographic packing and evaluated with four polar compounds (uracil, cytosine, guanosine, and cytidine). Compared with unmodified silica gel, modified silica gel produces sharper peaks and better separation efficiency. This novel packing material may have a potential for application with highly isomerized sugar mixtures.

Packed hybrid silica nanoparticles as sorbents with thermo-switchable surface chemistry and pore size for fast extraction of environmental pollutants

Thermoresponsive poly(N-isopropylacrylamide)-grafted silica nanoparticles (SiNPs) have been synthesized and fully characterized by ATR-FTIR, TGA, HRTEM, BET and DLS analysis. Hybrid solid phase extraction (SPE) beds with tuneable pore size and switchable surface chemistry were prepared by packing the polymer-grafted nanoparticles inside SPE cartridges. The cartridges were tested by checking the thermo-regulated elution of model compounds, namely methylene blue, caffeine and amoxicillin. Extraction of the analytes and regeneration of the interaction sites on the sorbent surface was carried out entirely in water solution by changing the external temperature below and above the lower critical solution temperature (LCST) of the polymer. The results demonstrate that the elution of model compounds depends on the temperature-regulated size of the inter-particle voids and on the change of surface properties of the PNIPAM-grafted nanoparticles from hydrophilic to hydrophobic.

Thermoresponsive poly(N-isopropylacrylamide)-grafted silica nanoparticles were synthesized and used to prepare solid phase extraction sorbents with switchable pore size and surface chemistry for temperature-regulated extraction of water pollutants.

Synthesis of Polymer-Mesoporous Silica Nanocomposites

Polymer nanocomposites show unique properties combining the advantages of the inorganic nanofillers and the organic polymers. The mesoporous silica nanofillers have received much attention due to their ordered structure, high surface area and ease for functionalization of the nanopores. To accommodate macromolecules, the nanopores lead to unusually intimate interactions between the polymer and the inorganic phase, and some unusual properties can be observed, when compared with nonporous fillers. Whereas many review articles have been devoted to polymer/nonporous nanofiller nanocomposites, few review articles focus on polymer/mesoporous silica nanocomposites. This review summarizes the recent development in the methods for synthesizing polymer/mesoporous silica nanocomposites based on the papers published from 1998 to 2009, and some unique properties of these composites are also described.

Thermo-responsive columns for HPLC: The effect of chromatographic support and polymer molecular weight on the performance of the columns

Recently a novel technique has been developed in chromatography, namely thermo-responsive chromatography. This employs the use of thermo-responsive polymers grafted onto pre-formed stationary phases for the separation of hydrophobic analytes. The resultant thermo-responsive silica exhibits temperature-controlled hydrophilic-hydrophobic properties. In this study, the themo-responsive polymers were grafted in situ into the pre-packed aminated silica columns. It was found that the molecular weight of the grafted thermo-responsive polymers should be optimized in order to obtain an efficient thermo-responsive column. Furthermore, within this study it was observed that the type of stationary phase (monolithic or packed beads) and the presence of mesoporosity in the system are important parameters influencing the final performance of the thermo-responsive column.

PEGylated Chromatography: Efficient Bioseparation on Silica Monoliths Grafted with Smart Biocompatible Polymers

Novel oligo(ethylene glycol)-based thermoresponsive stationary phases have been studied for the separation of bioanalytes. Well-defined copolymers of (2-methoxyethoxy)ethyl methacrylate and oligo(ethylene glycol) methacrylate were synthesized by atom-transfer radical polymerization in the presence of an N-succinimidyl-functionalized initiator. The reactive chain ends of these copolymers were then reacted with amino-functionalized silica monoliths. The formed composites were studied as chromatography materials. For instance, it was demonstrated that thermoresponsive oligo(ethylene glycol)-based stationary phases allow rapid, efficient separation of steroid and protein mixtures in pure water under isocratic high-performance liquid chromatographic elution.

Living Radical Polymerization by the RAFT Process - A Second Update

This paper provides a second update to the review of reversible deactivation radical polymerization achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible addition–fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379–410). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669–692). This review cites over 500 papers that appeared during the period mid-2006 to mid-2009 covering various aspects of RAFT polymerization ranging from reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses and a diverse range of applications. Significant developments have occurred, particularly in the areas of novel RAFT agents, techniques for end-group removal and transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.