Nanodroplet chemical microarrays and label-free assays

Microfluidics and coagulation biology

The study of blood ex vivo can occur in closed or open systems, with or without flow. Microfluidic devices, which constrain fluids to a small (typically submillimeter) scale, facilitate analysis of platelet function, coagulation biology, cellular biorheology, adhesion dynamics, and pharmacology and, as a result, can be an invaluable tool for clinical diagnostics. An experimental session can accommodate hundreds to thousands of unique clotting, or thrombotic, events. Using microfluidics, thrombotic events can be studied on defined surfaces of biopolymers, matrix proteins, and tissue factor, under constant flow rate or constant pressure drop conditions. Distinct shear rates can be generated on a device using a single perfusion pump. Microfluidics facilitated both the determination of intraluminal thrombus permeability and the discovery that platelet contractility can be activated by a sudden decrease in flow. Microfluidic devices are ideal for multicolor imaging of platelets, fibrin, and phosphatidylserine and provide a human blood analog to mouse injury models. Overall, microfluidic advances offer many opportunities for research, drug testing under relevant hemodynamic conditions, and clinical diagnostics.

Surface preparation strategies for improved parallelization and reproducible MALDI-TOF MS ligand binding assays

Immunoassays are employed in academia and the healthcare and biotech industries for high-throughput, quantitative screens of biomolecules. We have developed monolayer-based immunoassays for MALDI-TOF MS. To improve parallelization, we adapted the workflow to photolithography-generated arrays. Our work shows Parylene-C coatings provide excellent "solvent pinning" for reagents and biofluids, enabling sensitive MS detection of immobilized components. With a unique MALDI-matrix crystallization technique we show routine interassay RSD <10% at picomolar concentrations and highlight platform compatibility for relative and label-free quantitation applications. Parylene-arrays provide high sample densities and promise screening throughputs exceeding 1000 samples/h with modern liquid-handlers and MALDI-TOF systems.

High-throughput small molecule identification using MALDI-TOF and a nanolayered substrate

Encoderless combinatorial chemistry requires high-throughput product identification without the use of chemical or other tags. We developed a novel nanolayered substrate plate and combined it with a microarraying robot, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, and custom software to produce a high-throughput small molecule identification system. To optimize system performance, we spotted 5 different chemical entities, spanning a m/z range of 195 to 1338, in 20,304 spots for a total of 101,520 molecules. The initial spot identification rate was 99.85% (20,273 spots), and after a proofreading algorithm was added, 100% of 20,304 spots and 101,520 molecules were identified. An internal recalibration algorithm also significantly improved mass accuracy to as low as 45 ppm. Using this optimized system, 47 different chemical entities, spanning a m/z range of 138 to 1,592, were spotted over 5,076 spots and could be identified with 100% accuracy. Our study lays the foundation for improved encoderless combinatorial chemistry.