Sean Linder, Ph.D. 

Office of Regulatory Affairs (ORA)
Arkansas Regional Lab
Jefferson, AR

Background:

Ph.D., Bioanalytical Chemistry, University of Arkansas
FDA Experience – 1 year

Research Interests:

My primary research interests lie in the development and application of analytical methodologies for the detection of biologically relevant compounds in complex matrices. Over the last seven years, I have focused on the development of extraction and detection protocols in biological tissues, fluids, and foodstuffs. This work has been very diverse in that analytes of interest have been both organic and inorganic in origin. Notable work includes: 1) Analytical techniques for the determination of multiple classifications of anticoagulants in animal tissues at sub parts-per-million (ppm) levels. 2) Determination of elemental compounds, such as lead, arsenic, and selenium in multiple biologically relevance matrices at sub parts-per-million (ppm) levels. 3) Implementation of post-extraction automated cleanup technologies to increase sample throughput and laboratory efficiency. With experience in both organic and inorganic analytical methodologies, the opportunity to develop new methodologies in the evolving field of nanotechnology is of great personal and professional interest.

Proposed Research Project for FDA Fellow:

As nanomaterials emerge in commercially available products regulated by the FDA, a need will exist for quantitative methodologies for their detection and identification. This need will most likely be driven by consumer concern and/or any potential health risks associated with the consumption of nanomaterials by human or animals. The Fellow would work in conjunction with NCTR to adapt existing techniques for analysis of nanomaterials to applications for use within the structure of ORA. Due to the fact that nanoscale silver is already a commercially viable product in the world market, it seems prudent that it serve as the initial analyte of interest in phase one research. Nanoscale silver has the potential to proliferate as a food-borne contaminant from packaging and/or direct inclusion in food products. The research goals would include: 1) Determine the optimal analytical techniques for the rapid screening of nanoscale silver in a variety of FDA regulated products. 2) Develop extraction or digestion procedures to isolate nanoscale silver from products that contain interfering substances or difficult matrices. 3) Develop techniques for the quantitative evaluation of nanoscale silver in a variety of FDA regulated products using ICP-MS. 4) Develop protocols for the utilization of electron microscopy (EM) as a confirmatory tool in the final assessment of products that appears to contain nanoscale silver contamination. EM protocols potentially help in the differentiation between product adulteration and natural occurrence.

Selected Recent Publications:

1. D.R. Bobbitt and S.W. Linder, “Recent Advances in Chiral Detection for High Performance Liquid Chromatography”, Trends in Analytical Chemistry 2001, 20, 111-123.
2. S.W. Linder, G.W. Yanik, E.R. Francotte, and D.R. Bobbitt, “Real-Time Assessment of Enantiomeric Purity Via a Polarimetric/Absorption Detector Response Function”, Enantiomer 2002, 7, 41-47.
3. K. Ng, S.W. Linder, “HPLC Separation of Tetracycline Analogues: Comparison Study of Laser-Based Polarimetric Detection with UV Detection”, Journal of Chromatographic Science 2003, 41, 460-466.
4. S.W. Linder, G.W. Yanik, D.R. Bobbitt, “Evaluation of Laser-Based Polarimetry for the Determination of Enantiomeric Excess (EE) at the Extremes of the EE Scale”, Microchemical Journal 2004, 76, 105-112.
5. S.W. Linder, “Selectivity of Aflatoxin Analogs on Multiple Supelco Ascentis Stationary Phases”, The Reporter 2008, 26.1, 17-19.
6. B. Veach, C. Drake, A. Fong, and S.W. Linder, Method for Determination and Confirmation of Norfloxacin, Enrofloxacin, and Ciprofloxacin using LC/MS3, FDA Laboratory Information Bulletin, 2009, In Publication.

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Ken J. Yoshitomi, Ph.D. 

Applied Technology Center
Pacific Regional Laboratory Northwest
Office of Regulatory Affairs
Bothell, WA

Background:

B.A., University of San Diego
Ph.D., University of Cincinnati
FDA Experience – 8 years

Research Interests:

Development of rapid, molecular based assays targeting bacterial pathogens in complex food matrices: Design and utilization of nucleic acid based detection technology has greatly enhanced analytical capabilities in food microbiology. Multiplex conventional PCR and real-time PCR probe chemistries can rapidly provide genetic information on pathogens that may be present. These strategies have been successfully employed in the detection and characterization of virulence markers or conserved sequences associated with foodborne pathogens. Much of my interests lie in detection of E. coli O157:H7, as well as other shiga toxin-producing E. coli and Listeria. However, development of molecular assays alone is not sufficient for effective detection of bacterial pathogens from food. The complexity of the food matrix itself, associated background microflora, heterogeneous distribution of microorganisms in the sample, and nutrient requirements of the target organism presents a portion of the many challenges that must be overcome to successfully detect the pathogen of interest in a timely manner. Thus, we have investigated various enrichment procedures, immunomagnetic separation systems, and nucleic acid extraction techniques to improve specificity and sensitivity in our detection methodologies. Through the integration of rapid molecular screening techniques and standard cultural procedures is it possible to provide comprehensive detection strategies that are rapid, sensitive, and specific.

Proposed Research Project for FDA Fellow:

The proposed work will focus on the integration of molecular tools such as real-time PCR and nucleic acid hybridization array technology into high throughput testing methods for produce. The nature of this work may encompass the potential of field-use applications in addition to high throughput molecular screening methodology. It will be important to determine the critical points for the most effective utilization of molecular tools, including the effects of sample processing, enrichment techniques, nucleic acid extraction procedures, and multiplexing of appropriate gene target assays. The project will help identify limitations or obstacles involved in high volume sample analysis and seek to produce rapid, automated solutions that are scalable in nature. Work will involve knowledge of foodborne pathogens, real-time PCR detection chemistries, DNA/RNA extraction techniques, nucleic acid microarray technology, and immunocapture procedures.

Selected Recent Publications:

1. Jinneman, K.C. and K.J. Yoshitomi. 2009. "Evaluation of single-dilution MPN analysis for the estimation of L. monocytogenes at approximately 100 cfu/g food" LIB manuscript #4430.
2. Yoshitomi, K.J., Jinneman, K.C., and Weagant, S.D. 2006. Detection of Shiga toxin genes stx1, stx2, and the +93 uidA mutation of E. coli O157:H7/H- using SYBR Green I in a Real-time multiplex PCR. Molecular and Cellular Probes, 20:31-41.
3. Jinneman, K.C., K.J. Yoshitomi and S.D. Weagant. 2003. Multiplex real-time PCR method to identify shiga toxins, stx1 and stx2 and E. coli O157:H7 serogroup. Applied and Environmental Microbiology. 69:6327-6333.
4. Yoshitomi, K.J., K.C. Jinneman and S.D. Weagant. 2003 Optimization of a 3’-minor groove binder-DNA probe targeting the uidA gene for rapid identification of Escherichia coli O157:H7 using real-time PCR. Molecular and Cellular Probes, 17:275-280.

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