'Technology development is a key ingredient for advancing biomedical research, including pre-symptomatic and molecular diagnosis of disease.  Biosensors and physics-based tools are needed to quantitate levels of biomolecules and flux in individual cells and in samples containing mixtures of biological constituents.  Engineering and materials science approaches may provide useful methods to build interfaces with biological systems.' (NIH/NIGMS "Visions of the Future")

Scale-dependent Phenomena Underpinning Technology Development

Large-scale study of protein structure, function, and expression (proteomics) is instrumental to molecular biomarker discovery.  Due to the constantly changing nature of protein expression and state, these profiles are notoriously difficult to study.   High-resolution analytical assays such as two-dimensional electrophoresis and mass spectrometry have proven essential to proteomics; nevertheless, these information-rich methods can be slow and labor intensive.  With these considerations in mind, our group is developing  techniques, implemented via microfluidic technologies, as a means to achieve a rapid, yet still quantitative, assessment of protein expression & state variations in complex samples. 

AE Herr, DJ Throckmorton, AA Davenport, AK Singh. "On-chip Native Gel Electrophoresis-Based Immunoassays for Tetanus Antibody and Toxin." Anal Chem, 2005, 77(2), 585-590.

AE Herr, JI Molho, KA Drouvalakis, JC Mikkelsen, PJ Utz, JG Santiago, TW Kenny, "On-Chip Coupling of Isoelectric Focusing and Free Solution Electrophoresis for Multi-Dimensional Separations," Anal Chem, 2003, 75(5), 1180-1187.

 Biomarker Validation

In spite of significant advances in proteomic technology, few new protein biomarkers have emerged from the proteomic discovery pool, progressed though the scrutiny of validation studies, and become incorporated in diagnostic tools.  The long-term goal of our work is development of flexible instruments for the rapid validation of putative disease-specific biomarkers in promising diagnostic fluids. An urgent need exists for robust bioanalytical capability that delivers high-throughput validation of putative biomarkers, thus allowing subsequent incorporation of validated markers into diagnostics. To achieve this aim, our group employs nascent microfluidic technologies to seamlessly integrate complex sample preparation, sample handling, and quantitative bioanalytical assays into tools amenable to automation. 

AV Hatch, AE Herr, DJ Throckmorton, JS Brennan, and AK Singh. "Integrated Preconcentration SDS-PAGE of Proteins in Microchips Using Photopatterned Cross-Linked Polyacrylamide Gels." Anal Chem, 2006, 78(14), 4976 - 4984.

VC Rucker, KL Havenstrite, AE Herr. "Antibody Microarrays for Native Toxin Detection." Anal Biochem, 2005, 339(2), 262-270.

AE Herr, AK Singh. "Photopolymerized cross-linked polyacrylamide gels for on-chip protein sizing." Anal Chem, 2004, 76(16), 4727-33.

Clinical & Point-of-Care Diagnostics

Appropriate, effective biomolecular analysis mechanisms are identified for diagnostic development based upon the physicochemical characteristics of putative, disease-specific biomarkers. Most disease states are complex -- diagnosis & monitoring require more than simple binary detection of a small set of proteins. To compound the difficulty in assessing disease state, analytical grade quantitation and specificity are difficult to achieve as part of a disease diagnostic, especially diagnostics employed in near-patient environments.   Consequently, our group is exploring the use of electrophoretic microfluidic formats, as such formats have been demonstrated to allow rapid, analytical-grade quantitation of small sample volumes through enhanced resolving power and high-efficiency operation.

AE Herr, AV Hatch, DJ Throckmorton, HM Tran , JS Brennan, WV Giannobile, AK Singh. "Microfluidic Immunoassays as Rapid Saliva-based Clinical Diagnostics." Proc Natl Acad Sci USA, 2007, 104(13), 5268-5273.