Fundamental and Applied Studies of Individual Blood Platelets
Blood platelets are critically important in hemostasis and thrombosis, carrying and delivering the chemical messengers that regulate these processes. While much is known about ensemble platelet behavior, little is known about how individual platelets store and deliver chemical messenger; this paucity of information is due to the small size of each platelet and their propensity to activate. The Haynes lab has performed the first real-time, single platelet measurements of chemical messenger exocytosis. The techniques employed are microelectrochemical fast scan cyclic voltammetry and amperometry, and the data reveal how much chemical messenger is stored and how it is released. In addition, controlled microelectrochemical experiments varying platelet environment (osmolarity, temperature, pH) and membrane cholesterol levels explore the driving forces and determining factors for platelet chemical messenger delivery. Recent platelet studies examine chemical messenger storage and delivery in platelets from human patients with storage pool disorders, in hopes that a fundamental understanding of the disordered platelets may lead to new therapeutic treatments.
This work is supported by a NIH New Innovator Award and was previously supported by a Kinship Foundation Searle Scholar Award.
Multifunctional Drug Delivery Nanoparticles
Mesoporous silica nanoparticles hold great potential as multifunctional drug delivery agents; however, they have been limited in application because it has not previously been possible to produce well-ordered, small (sub-100-nm-diameter) nanoparticles that were stable in high ionic strength environments. These limitations meant that any intravenously injected nanoparticles would circulate for very short periods of time before uptake by the reticuloendothelial system or that they would catastrophically aggregate in the bloodstream. The Haynes lab has developed a mesoporous silica nanoparticle preparation that overcomes both of these limitations while also incorporating superparamagnetic and fluorescent contrast agents. Extensive nanoparticle toxicity studies have demonstrated that theses multifunctional mesoporous silica nanoparticles are compatible with both red blood cells and other immune system cells.
This work is supported by a NSF CAREER award.
Nanoparticle toxicology is an emerging field, gaining importance as intentional public exposure to engineered nanoparticles increases. Many traditional molecular toxicology assays fail in the presence of nanoparticles due to either increased nanoparticle surface reactivity or nanoparticles acting via new, unexpected routes. The Haynes group has pioneered single cell functional assays for considerations of nanoparticle toxicity, with initial focus on noble metal and metal oxide nanomaterial toxicity in immune system cells. To date, the Haynes group has explored nanoparticle uptake by cells (both quantitation and localization), cell viability, cell exocytotic function, and intracellular changes in reactive oxygen species following nanoparticle interaction. With variations in nanoparticle composition, size, shape, porosity, and surface ligand charge within two different cell models, some general trends are emerging namely that nanoparticles tend to be taken up into cellular granules and interfere with chemical messenger delivery, decreasing both the quantity and kinetics of chemical messenger delivery. Intracellular generation of reactive oxygen species correlates with this change in exocytotic function. The Haynes group is currently exploring nanoparticle design routes that would minimize both reactive oxygen species generation and exocytosis interference. In addition, Prof. Haynes is significantly involved with the ethics related to nanoparticle regulation and oversight.
This work is supported by a NSF CAREER award and was previously supported by a 3M Non-Tenured Faculty Grant.
This recently funded project has multiple directions that will eventually merge at the creation of a simplified model of the immune system within a microfluidic platform. First, the Haynes group is developing microfluidic expertise droplet-based devices, gradient-creating devices, and co-culture devices. The droplet-based devices will be used to encapsulate single cells within controlled, small volume environments for analysis using spectroscopic, electrochemical, and mass spectrometric techniques. The gradient-creating devices are being used to probe how neutrophils respond to competing gradients of chemokines. The co-culture devices are being used to explore cell-cell interactions among the various cell types relevant within the immune system and, specifically, inflammatory disorders such as sickle cell anemia and type I hypersensitivities. In parallel, the Haynes lab has been developing protocols for mass spectrometric analysis of immune cell-secreted lipid species, including prostaglandins and leukotrienes.
This work is supported by a NIH New Innovator Award.
Surface-Enhanced Raman Scattering Detection of Non-Traditional Analytes
The Haynes group expends significant effort toward facilitating the practical application of surface-enhanced Raman scattering (SERS). One area of research is in SERS substrate development, especially designing inexpensive, simple ways to create high enhancement factor SERS substrates such as sub-10-nm nanogap substrates that do not require advanced lithographic techniques (e.g. electron beam lithography). Another area of research focuses on generalizing SERS signal transduction, usually limited to analytes with a chemical or physical affinity for noble metal substrates, to new classes of analytes by advancing partition layer-assisted SERS. In these experiments, partition layers are assembled on the nanostructured noble metal substrates to facilitate concentration of analytes within the zone of electromagnetic enhancements. The approach has been successfully employed in the Haynes lab for sensing of mixtures of polychlorinated biphenyls and polycyclic aromatic hydrocarbons. Current work in this area employs this approach for detection and discrimination of phospholipid species, moving toward measurement of cell-secreted lipid species.
This work is supported by a Alfred P. Sloan Fellowship and was previously supported by the Petroleum Research Fund.