Ionic liquid crosslinkers for chiral imprinted nanoGUMBOS.

Molecularly imprinted polymers (MIPs) are an important class of selective materials for molecular specific sensors and separations. Molecular imprinting using non-covalent interactions in aqueous conditions still remains a difficult challenge due to interruption of hydrogen-bonding or electrostatic interactions water. Newly developed crosslinking ionic liquids are demonstrated herein to overcome problems of synthesizing aqueous MIPs, adding to previous examples of ionic liquids used as monomers in non-aqueous conditions or used as MIP solvents. Vinylimidazole ionic liquid crosslinkers were synthesized and subsequently explored as matrix supports for fabrication of molecularly imprinted polymeric nanoGUMBOS (nanoparticles derived from a group of uniform materials based on organic salts). Each of the four crosslinkers incorporated a unique functional spacer between the vinylimidazole groups, and the performance of the corresponding molecularly imprinted polymers was evaluated using chiral recognition as the diagnostic. High uptake values for l-tryptophan were found in the 13-87µmol/g range; and chiral recognition was determined via binding ratios of l-tryptophan over d-tryptophan that ranged from 5:1 to 13:1 for polymers made using different crosslinkers. Not only are these materials good for chiral recognition, but the results highlight the utility of these materials for imprinting aqueous templates such as biological targets for theranostic agents.

Facile preparation of polysaccharide-coated capillaries using a room temperature ionic liquid for chiral separations.

In this study, the dissolution of polysaccharides into an ionic liquid was investigated and applied as a coating onto the capillary walls of a fused-silica capillary in open-tubular CEC. The coating was evaluated by examining the chiral separation of two analytes (thiopental, sotalol) with three cellulose derivatives (cellulose acetate, cellulose acetate phthalate, and cellulose acetate butyrate). Baseline separation of thiopental enantiomers was achieved by use of each polysaccharide coating (Rs: 7.0, 8.1, 7.1), while sotalol provided partial resolution (Rs: 0.7, 1.0, 0.9). In addition, reproducibility of the cellulose-coated capillaries was evaluated by estimating the run-to-run and capillary-to-capillary RSD values of the EOF. Both stability and reproducibility were very good with RSD values of less than 7%.

An immobilized graphene oxide stationary phase for open-tubular capillary electrochromatography.

The research literature currently abounds with studies of graphene-related materials as a result of the extraordinary properties of such materials. On the basis of these citations, it is clear that the range of applications for such materials is substantial. In this manuscript, we report the immobilization of graphene oxide (GO) onto a fused-silica capillary to form a potential stationary phase for use in open-tubular CEC. We successfully incorporated GO through an in situ condensation reaction with (3-aminopropyl)triethoxysilane after silanization with (3-aminopropyl)triethoxysilane on the inner surface of the capillary. This GO-incorporated capillary was then characterized by use of SEM, infrared spectroscopy, and measurements of EOF. The electrochromatographic features of this stationary phase have also been investigated. Evaluation of acquired data indicates high electrochromatographic resolution and good capillary efficiency. Highly reproducible results between runs, days, and capillaries were also obtained.

Chiral separation of Huperzine A using CE - method validation and application in pharmaceutical formulations.

The aim of this work is the development, validation and application of an MEKC method for the chiral separation of Huperzine A. Huperzine A is an important compound that is used to treat Alzheimer's disease. However, only the (-)-form of this compound is biologically active and behaves as a potential acetylcholinesterase inhibitor. Therefore, the separation of the (-)-form from the (+)-form is of greatest importance. Optimal conditions, regarding resolution and analysis time, were established by altering several experimental parameters, such as temperature, field strength, pH, type and concentration of BGE and chiral selector. A major problem that had to be solved in this study was the low intensity and efficiency of the peaks. More parameters were examined, such as the addition of modifiers, to optimize further the separation, and particularly the efficiency. Baseline enantioseparation was achieved by using a BGE of 50 mM acetate (pH 5.0), supplemented with 0.2% w/v poly(sodium N-undecanoyl-ll-alanyl-valinate) and 10% v/v tert-butanol. Finally, the optimum conditions were applied to a pharmaceutical formulation, to demonstrate the ability of the method to control the purity of the (-)-Huperzine A in pharmaceutical formulations.

Lysine-based zwitterionic molecular micelle for simultaneous separation of acidic and basic proteins using open tubular capillary electrochromatography.

In this work, a zwitterionic molecular micelle, poly-epsilon-sodium-undecanoyl lysinate (poly-epsilon-SUK), was synthesized and employed as a coating in open tubular capillary electrochromatography (OT-CEC) for protein separation. The zwitterionic poly-epsilon-SUK containing both carboxylic acid and amine groups can be either protonated or deprotonated depending on the pH of the background electrolyte; therefore, either an overall positively or negatively charged coating can be achieved. This zwitterionic coating allows protein separations in either normal or reverse polarity mode depending on the pH of the background electrolyte. The protein mixtures contained four basic proteins (lysozyme, cytochrome c, alpha-chymotrypsinogen A, and ribonuclease A) and six acidic proteins (myoglobin, deoxyribonuclease I, beta-lactoglobulin A, beta-lactoglobulin B, alpha-lactalbumin, and albumin). Protein separations were optimized specifically for acidic (reverse mode) and basic (normal mode) pH values. Varying the polymer thickness by changing the polymer and salt concentration had a great influence on protein resolution, while nearly all peaks were also baseline resolved in both modes using the optimized poly-epsilon-SUK coating concentration of 0.4% (w/v). Proteins in human sera were separated under optimized acidic and basic conditions in order to demonstrate the general utility of this coating. Nanoscale characterizations of the poly-epsilon-SUK micellar coatings on silicon surfaces were accomplished using atomic force microscopy (AFM) to gain insight into the morphology and thickness of the zwitterionic coating. The thickness of the polymer coating ranged from 0.9 to 2.4 nm based on local measurements using nanoshaving, an AFM-based method of nanolithography.

Mechanistic investigation of N-homocysteinylation-mediated protein-gold nanoconjugate assembly.

Herein we report the use of protein-gold nanoconjugate (PGNs) as probes for elucidating mechanistic events involved in protein homocystamide detection with gold nanoparticles (GNPs), as was previously reported by our laboratory. Three different PGN probes are synthesized by direct adsorption of cytochrome c, albumin, or human serum onto citrate-capped GNPs. The PGNs are subsequently purified and treated to confer N-homocysteinylation. Individual PGN systems are evaluated to assess the effect of modification on (1) surface plasmon resonance (SPR), (2) protein structural conformation, and (3) assembly-association. The degree of PGN assembly and colorimetric signal observed postmodification varies based on the type of conjugated protein. For example, results of time-resolved dynamic light scattering studies indicate that modification of cytochrome c-PGNs yields rapid formation of macroscopic nanoparticle assemblies that eventually precipitate from solution. In contrast, albumin and human serum PGNs exhibit higher stability toward modification. Additionally, findings from circular dichroism studies indicate significant modification-induced denaturation, which is what may initiate assembly via electrosteric destabilization of PGNs. The results of electrophoretic studies appear to confirm that the process of N-homocysteinylation-mediated PGN assembly culminates in covalent interparticle association by disulfide cross-linking among modified proteins.