Synthesis and CO2 Capture of Porous Hydrogel Particles Consisting of Hyperbranched Poly(amidoamine)s.

We successfully synthesized new macroporous hydrogel particles consisting of hyperbranched poly(amidoamine)s (HPAMAM) using the Oil-in-Water-in-Oil (O/W/O) suspension polymerization method at both the 50 mL flask scale and the 5 L reactor scale. The pore sizes and particle sizes were easily tuned by controlling the agitation speeds during the polymerization reaction. Since O/W/O suspension polymerization gives porous architecture to the microparticles, synthesized hydrogel particles having abundant amine groups inside polymers exhibited a high CO2 absorption capacity (104 mg/g) and a fast absorption rate in a packed-column test.

Controlled transformation of CdTe nanoparticles into nanoribbons via self-assembling process.

CdTe nanorribons were successfully synthesized from individual nanoparticle. Slow oxidation of Te(2-) in CdTe nanoparticles resulted in the assembly of ribbons consisting of several layers of individual nanocrystals. The light-controlled self-assembly of CdTe nanoparticles led to twisted ribbons with variable pitch. Transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were performed to characterize the synthesized nanostructures. The suggested synthetic procedure provides a viable pathway for the fabrication of nanomaterials with helical conformations.

Electrochemical preparation of ionic liquid-stabilized palladium nanoparticles.

We have successfully synthesized ionic liquid (IL)-stabilized palladium (Pd) nanoparticles (NPs) by electrochemical reduction. The particle size was controlled by adjusting the current density. Transmission electron microscopic (TEM) images showed that the average diameters of the Pd NPs were 2.4, 3.2, and 3.5 nm, depending on the synthetic conditions. Particle size increased as the current density and the length of the alkyl chain in the cation decreased. X-ray diffraction of the resulting NPs indicated that the particles had a crystalline structure. Overall, the results show that NPs can be finely tuned according to the kinds of ILs employed, as well as by electrochemical reduction.

Fabrication of metal nanoparticles using hydroxylated ionic liquids.

Metal nanoparticles were successfully synthesized from the self-regulated reduction of hydroxylated ionic liquids in aqueous phase without additives. A new water-phase synthesis of gold and palladium nanoparticles using N-(2-hydroxyethyl)-N-methylmorpholinium tetrafluoroborate is described. Transmission electron microscopy was performed to characterize the metal nanoparticles. The average sizes of the gold and palladium nanoparticles were 4.3 nm and 3.2 nm, respectively. Hydroxylated ionic liquids served as both reductants and protective agents, significantly simplifying the preparation of nanoparticles. The produced particles were highly crystalline in structure with a face-centered cubic (fcc) lattice. Finally, we showed preliminary results that suggest different hydroxylated ionic liquids can also be used to prepare various metal nanoparticles.

Advanced cleanup process of the free-flow microfluidic device for protein analysis.

The treatment of samples preparation is generally recognized as a bottleneck for the rapid analysis of protein because of the off-chip performance in many cases. In this study, we used the charge characteristics of protein to develop a simple and rapid electro-microfluidic desalting system as an effective means of cleaning up protein sample. When we loaded a urea-rich protein sample and a buffer solution into a free-flow zone electrophoresis (FFZE) chamber, the microfluidic device was able to separate the charged protein sample and the non-charged urea. With a 90 V electric field in the FFZE chamber, the removal efficiency of the urea was about 88% and the recovery of the protein was 78%. In addition, the desalted protein sample used in this device showed significant improvement with respect to the MALDI-TOF-MS spectrum signal of a fusion protein, which was fused to the gold-binding polypeptide with enhanced green fluorescent protein, as a model protein. The inflow of the purified fusion protein sample can be successfully immobilized on the gold surface and analyzed by confocal fluorescence microscopy and surface plasmon resonance for biotechnological sensors.

Removal of bovine serum albumin using solid-phase extraction with in-situ polymerized stationary phase in a microfluidic device.

Serum albumin, one of the most abundant serum proteins, blocks the expression of other important biomarkers. The objective of this study is to remove serum albumin effectively by using solid-phase extraction (SPE) in microfluidic devices. Photo-polymerized adsorbent as a stationary phase of SPE was used to remove bovine serum albumin (BSA). The adsorption capacity was examined with the effect of pH and concentration in BSA solution, and adjustment of monomer concentration such as hydrophilic 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylamide in the adsorbent. The effect of hydrophobic butyl methacylate on BSA adsorption was also studied. Selective removal in a bicomponent with BSA and bovine gamma-globulin was performed by adjusting the pH as required.

Microfluidic cell disruption system employing a magnetically actuated diaphragm.

A microfluidic cell lysis chip equipped with a micromixer and SPE unit was developed and used for quantitative analysis of intracellular proteins. This miniaturized sample preparation system can be employed for any purpose where cell disruption is needed to obtain intracellular constituents for the subsequent analysis. This system comprises a magnetically actuated micromixer to disrupt cells, a hydrophobic valve to manipulate the cell lysate, and a packed porous polymerized monolith chamber for SPE and filtering debris from the cell lysate. Using recombinant Escherichia coli expressing intracellular enhanced green fluorescent protein (EGFP) and lipase as model bacteria, we optimized the cell disruption condition with respect to the lysis buffer composition, mixing time, and the frequency of the diaphragm in the micromixer, which was magnetically actuated by an external magnetic stirrer in the micromixer chamber. The lysed sample prepared under the optimal condition was purified by the packed SPE in the microfluidic chip. At a frequency of 1.96 Hz, the final cell lysis efficiency and relative fluorescence intensity of EGFP after the cell disruption process were greater than 90 and 94%, respectively. Thus, this microfluidic cell disruption chip can be used for the efficient lysis of cells for further analysis of intracellular contents in many applications.

Recovery of succinic acid produced by fermentation of a metabolically engineered Mannheimia succiniciproducens strain.

There have recently been much advances in the production of succinic acid, an important four-carbon dicarboxylic acid for many industrial applications, by fermentation of several natural and engineered bacterial strains. Mannheimia succiniciproducens MBEL55E isolated from bovine rumen is able to produce succinic acid with high efficiency, but also produces acetic, formic and lactic acids just like other anaerobic succinic acid producers. We recently reported the development of an engineered M. succiniciproducens LPK7 strain which produces succinic acid as a major fermentation product while producing much reduced by-products. Having an improved succinic acid producer developed, it is equally important to develop a cost-effective downstream process for the recovery of succinic acid. In this paper, we report the development of a simpler and more efficient method for the recovery of succinic acid. For the recovery of succinic acid from the fermentation broth of LPK7 strain, a simple process composed of a single reactive extraction, vacuum distillation, and crystallization yielded highly purified succinic acid (greater than 99.5% purity, wt%) with a high yield of 67.05wt%. When the same recovery process or even multiple reactive extraction steps were applied to the fermentation broth of MBEL55E, lower purity and yield of succinic acid were obtained. These results suggest that succinic acid can be purified in a cost-effective manner by using the fermentation broth of engineered LPK7 strain, showing the importance of integrating the strain development, fermentation and downstream process for optimizing the whole processes for succinic acid production.

Kinetics of the extraction of succinic acid with tri-n-octylamine in 1-octanol solution.

Kinetic studies for the extraction of succinic acid from aqueous solution with 1-octanol solutions of tri-n-octylamine (TOA) were carried out using a stirred cell with a microporous hydrophobic membrane. The interfacial concentrations of species were correlated and thus the intrinsic kinetics was obtained. The overall extraction process was controlled by the chemical reaction at or near the interface between the aqueous and organic phases. The formation reaction of succinic acid-TOA complex was found to be first order with respect to the concentration of succinic acid in the aqueous phase and the order of 0.5 with respect to that of TOA in the organic phase with a rate constant of (3.14 +/- 0.6) x 10(-8) m(2.5) x mol(-0.5) x s(-1). The dissociation reaction of succinic acid-TOA complex was found to be the second-order with respect to that of succinic acid-TOA complex in the organic phase and the order of -2 with respect to that of TOA in the organic phase with a rate constant of (1.44 +/- 1.4) x 10(-4) mol x m(-2) x s(-1).

Selective extraction of acetic acid from the fermentation broth produced by Mannheimia succiniciproducens.

Acetic acid is by-product from fermentation processes for producing succinic acid using Mannheimia succiniciproducens . To obtain pure succinic acid from the final fermentation broth, acetic acid was selectively removed based on the different extractability of succinic acid and acetic acid with pH using tri-n-octylamine (TOA) as extractant. When successive batch extractions were performed using 0.25 mol TOA kg(-1) dissolved in 1-octanol at pH 5, the mol ratio of succinic acid to acetic acid before extraction was 4.9 and the final ratio after the fourth batch was 9.4.