My research mostly focuses on using quantitative and standardized flow cytometry to measure clinically and biomanufacturing relevant biological substances, cells, extracellular vesicles/exosomes, virus, proteins, DNA and RNA. Current effort under the flow cytometry standards consortium includes: 1) development of additional reference fluorophore solutions, methods, and data for standardizing flow cytometer intensity scale and performance characteristics in the unit of the equivalent number of reference fluorophores (ERF) through ERF measurement service; 2) development of biological reference standards, control materials, and best practice procedures and methods for standardizing flow cytometric assays in counting of bio-entities and analysis of biomarker expression levels; 3) building infrastructure for flow cytometry data repository and multi-modal simultaneous data analysis for reference data generation. In addition to the consortium activities, current projects include: 1) characterization of biological reference materials including cell lines, engineered cell lines, primary cells, lyophilized cells, synthetic cell mimics, viral vectors, and exosomes; 2) quantifying expression of cell surface and intracellular biomarkers by estimating the antibodies bound per cell (ABC); 3) enumeration of cells with specific phenotypic characteristics and function, e.g. CD34+ stem cells and cytokine producing T cells; 4) harmonizing flow cytometry data across different cytometer platforms through panel design, antibody titration, instrument calibration, reference cell controls, and data analysis.
Memberships and Committees
- CLSI Committee on Validation of Assays Performed by Flow Cytometry, 2017-2022
- CDRH/FDA Hematology and Pathology Devices Panel Advisory Committee, Member, January 2023 – February 2026
- ISAC Flow Cytometry Data Standards Committee, 2022-present
- ICCS Quality and Standards Committee, 2016-present
- ISEV Rigor and Standardization: EV Reference Materials Task Force, 2020-present
- Number Concentration Measurements of Polystyrene Submicrometer Particles. Nanomaterials, 12: 3118 (2022).
- Evaluation protocol for CRISPR/Cas9 mediated CD19 knockout GM 24385 cells by flow cytometry and Sanger sequencing. Biotechniques 72: 279-286 (2022).
- Towards quantitative and standardized serological and neutralization assays for COVID-19. Int. J. Mol. Sci. 22: 2723 (2021).
- Development and validation of measurement traceability for in situ immunoassays. Clin Chem. 67(5): 763-771 (2021).
- Establishing CD19 B-cell reference control materials for comparable and quantitative cytometric expression analysis. PLoS ONE, 16(3): e0248118 (2021).
- Expanding NIST’s Calibration of Fluorescent Microspheres for Flow Cytometry to More Fluorescence Channels and Smaller Particles. Materials, 13: 4111 (2020).
- Measurement and Standardization Challenges for Extracellular Vesicle Therapeutic Delivery Vectors. Nanomedicine 15(22): 2149-2170 (2020).
- An accurate and rapid single step protocol for enumeration of cytokine positive T lymphocytes. J Immunol Regen Med. 9: 100032 (2020).
- Building Measurement Assurance in Flow Cytometry. Cytometry Part A, 95A, 626-630 (2019).
- Comparison of volumetric and bead-based counting of CD34 cells by single-platform flow cytometry. Cytometry Part B 96B: 508-513 (2019).
- Quantitative Fluorescence Measurements with Multicolor Flow Cytometry. Flow Cytometry Protocols, 4th Edition, Humana Press/Springer, New York, p93-110 (2018).
- Assignment of the Number of Equivalent Reference Fluorophores to Dyed Microspheres. J. Res. Natl. Inst. Stand. Technol. 121, 269-286 (2016).
- Quantitative Flow Cytometry Measurements in Antibodies Bound per Cell Based on a CD4 Reference. Curr. Protoc. Cytom. 75:1.29.1-1.29.14 (2016).
- Determination of CD4+ Cell Count per µL in Reconstituted Lyophilized Human PBMC Pre-labelled with Anti-CD4 FITC Antibody. Cytometry Part A 87A, 244-253 (2015).
- Quantification of Cells with Specific Phenotypes II: Determination of CD4 Expression Level on Lyophilized Human PBMC Surface Labeled with Anti-CD4 FITC Antibody. Cytometry Part A 87A, 254-261 (2015).
- Quantifying CD4 receptor protein in two human CD4+ lymphocyte preparations for quantitative flow cytometry. Clin Proteomics 11:43 (2014).
- NIST/ISAC standardization study: variability in assignment of intensity values to fluorescence standard beads and in cross calibration of standard beads to hard dyed beads. Cytometry Part A, 81A, 785-796 (2012).
- Human CD4+ Lymphocytes for Antigen Quantification: Characterization Using Conventional Flow Cytometry and Mass Cytometry. Cytometry Part A 81A, 567-575 (2012).
- A Model for Harmonizing Flow Cytometry in Clinical Trials. Nature Immunology 11(11), 975-978 (2010).
NIST-NRC and NIH/NIST NRC Postdoctoral Fellowship Opportunities
- Quantitative Flow Cytometry Measurements; RO#: 50.64.41.B6740
- Multiplexed Assays for Cell-based Production of Biopharmaceuticals; RO#: 50.64.41.B8223
- Analytical Metrology for Isolating, Purifying and Characterizing Extracellular Vesicles (EVs) for Development and Delivery of Gene and Protein-Based Therapeutics; (RO#: 50.64.41.C0414)