Department of Chemistry

Analytical Chemistry

Research ImageConsistently ranked as one of the top analytical divisions in the United States, ranked number 1 for the fifth year in a row by U.S. News and World Report magazine in its 2011 edition of "America's Best Graduate Schools," the analytical division is recognized as a world leader in this scientific area.

Following the tradition set by the late Professor Charles N. Reilley, the division extends the frontier of the field through a focus on fundamental studies related to chemical analysis and the development of innovative instrumentation. All traditional areas of research are represented, including electrochemistry, mass spectrometry, microscopy, sensors, separations and spectroscopy.

Research projects span a wide range of chemical analysis science and include, but are not limited to, biosensors, nanoscopic materials, neurochemistry, microvolume separations and analysis, protein adsorption, supercritical fluids and single-molecule analysis; for examples of currently active research projects please see the list below. The division has strong relationships with a large number of companies in the pharmaceutical, chemical and scientific instrumentation industries, which provide continued support of research fellowships and the Analytical Seminar series.

 

Recent Research Highlights

NO-Releasing Chitosan Oligosaccharides

As reported in Biomaterials, secondary amine-functionalized chitosan oligosaccharides of different molecular weights have been synthesized by the Schoenfisch Group. The process involved grafting 2-methyl aziridine from the primary amines on chitosan oligosaccharides, followed by reaction with nitric oxide, NO, gas under basic conditions to yield N-diazeniumdiolate NO donors. The total NO storage, maximum NO flux, and half-life of the resulting NO-releasing chitosan oligosaccharides were controlled by the molar ratio of 2-methyl aziridine to primary amines and the functional group surrounding the N-diazeniumdiolates respectively.

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The secondary amine-modified chitosan oligosaccharides greatly increased the NO payload over existing biodegradable macromolecular NO donors. In addition, the water-solubility of the chitosan oligosaccharides enabled their penetration across the extracellular polysaccharides matrix of Pseudomonas aeruginosa biofilms and association with embedded bacteria. The effectiveness of these chitosan oligosaccharides at biofilm eradication was shown to depend on both the molecular weight and ionic characteristics. Low molecular weight and cationic chitosan oligosaccharides exhibited rapid association with bacteria throughout the entire biofilm, leading to enhanced biofilm killing. At concentrations resulting in 5-log killing of bacteria in Pseudomonas aeruginosa (P. aeruginosa) biofilms, the NO-releasing and control chitosan oligosaccharides elicited no significant cytotoxicity to mouse fibroblast L929 cells in vitro.

 

Size and Shape Matter

Nitric oxide, NO, a reactive free radical, has proven effective in eradicating bacterial biofilms with reduced risk of fostering antibacterial resistance. Published in ACS Applied Materials & Interfaces, researchers in the Schoenfisch Group have evaluated the efficacy of NO-releasing silica nanoparticles against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus biofilms as a function of particle size and shape.

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Three sizes of NO-releasing silica nanoparticles with identical total NO release were utilized to study antibiofilm eradication as a function of size. To observe the role of particle shape on biofilm killing, the group varied the aspect ratio of the NO-releasing silica particles from 1 to 8 while maintaining constant particle volume and NO-release totals. Nitric oxide-releasing particles with decreased size and increased aspect ratio were more effective against both P. aeruginosa and S. aureus biofilms, with the Gram-negative species exhibiting the greatest susceptibility to NO.

To further understand the influence of these nanoparticle properties on NO-mediated antibacterial activity, the group visualized intracellular NO concentrations and cell death with confocal microscopy. Smaller NO-releasing particles exhibited better NO delivery and enhanced bacteria killing compared to the larger particles. Likewise, the rod-like NO-releasing particles proved more effective than spherical particles in delivering NO and inducing greater antibacterial action throughout the biofilm.

 

Representative Publications

In Vivo Analytical Performance of Nitric Oxide-Releasing Glucose Biosensors. Robert J. Soto, Benjamin J. Privett, and Mark H. Schoenfisch. Anal. Chem., 2014, 86 (14), pp 7141–7149.

Medullary Norepinephrine Neurons Modulate Local Oxygen Concentrations in the Bed Nucleus of the Stria Terminalis. Elizabeth S Bucher, Megan E Fox, Laura Kim, Douglas C Kirkpatrick, Nathan T Rodeberg, Anna M Belle and Mark Wightman. Journal of Cerebral Blood Flow & Metabolism (2014) 34, 1128–1137.

Dynamics and Evolution of β-Catenin-Dependent Wnt Signaling Revealed through Massively Parallel Clonogenic Screening. Pavak K. Shah, Matthew P. Walker, Christopher E. Sims, Michael B. Major, and Nancy L. Allbritton. Integr. Biol., 2014,6, 673-684.

Small Sample Sorting of Primary Adherent Cells by Automated Micropallet Imaging and Release. Pavak K. Shah, Silvia Gabriela Herrera-Loeza, Christopher E. Sims, Jen Jen Yeh, and Nancy L. Allbritton. Cytometry Part A, Volume 85, Issue 7, pages 642–649, July 2014.

Optimization of 3-D Organotypic Primary Colonic Cultures for Organ-on-Chip Applications. Asad A Ahmad, Yuli Wang, Adam D Gracz, Christopher E Sims, Scott T Magness and Nancy L Allbritton. Journal of Biological Engineering 2014, 8:9.

Immobilization of Lambda Exonuclease onto Polymer Micropillar Arrays for the Solid-Phase Digestion of dsDNAs. Nyoté J. Oliver-Calixte, Franklin I. Uba, Katrina N. Battle, Kumuditha M. Weerakoon-Ratnayake, and Steven A. Soper. Anal. Chem., 2014, 86 (9), pp 4447–4454.

Chemical Vapor Deposition of Aminopropyl Silanes in Microfluidic Channels for Highly Efficient Microchip Capillary Electrophoresis-Electrospray Ionization-Mass Spectrometry. Nicholas G. Batz, J. Scott Mellors, Jean Pierre Alarie, and J. Michael Ramsey. Anal. Chem., 2014, 86 (7), pp 3493–3500.

Micropallet Arrays for the Capture, Isolation and Culture of Circulating Tumor Cells from Whole Blood of Mice Engrafted with Primary Human Pancreatic Adenocarcinoma. Guohua Xu, Yansheng Ye, Xiaoli Liu, Shufen Cao, Qiong Wu, Kai Cheng, Maili Liu, Gary J. Pielak, and Conggang Li. Biosensors and Bioelectronics, Volume 54, 15 April 2014, Pages 476–483.

Fluorous Enzymatic Synthesis of Phosphatidylinositides. Weigang Huang, Angela Proctor, Christopher E. Sims, Nancy L. Allbritton, and Qisheng Zhang. Chem. Commun., 2014,50, 2928-2931.

Response of Single Leukemic Cells to Peptidase Inhibitor Therapy Across Time and Dose Using a Microfluidic Device. Michelle L. Kovarik, Alexandra J. Dickinson, Pourab Roy, Ranjit A. Poonnen, Jason P. Fine and Nancy L. Allbritton. Integr. Biol., 2014, 6, 164-174.