Professor Dan Chiu at the University of Washington is supported by the Analytical and Surface Chemistry Program in the Division of Chemistry with co-funding from the Office of International Science and Engineering for an International Collaboration in Chemistry (ICC) seeking to develop new methodology for monitoring the spatiotemporal dynamics of cellular releasates. Through the International Collaboration in Chemistry Program, the work includes collaboration with Professor David McGloin at the University of Dundee (UK); Dr. McGloin's work is supported by the Engineering and Physical Sciences Research Council (EPSRC) of the UK.
The approach is based on holographic optical trapping, sensitive microfluidic manipulation, and single-molecule assays. It targets orders of magnitude improvements in spatial resolution and sensitivity over current techniques, enabling progress toward answering biological questions that are currently inaccessible with existing methods. The technology pushes the current limits in holographic optical trapping and imaging, develops new techniques in microfluidic manipulation, and expands current capabilities in single-molecule assays. Applications address the spatial and temporal dynamics of cell secretion and cell-cell communication, seeking a new level of understanding on the functioning of immune cells.
In addition to the technical impacts, the project provides broader impact through a unique multidisciplinary international training experience for graduate students via bidirectional visits.
Few techniques exist for mapping the spatiotemporal dynamics of the release of peptides and proteins from single cells. Yet, the ability to follow the spatiotemporal patterns of cellular release is critical in deciphering the complex chemical communications between cells. In the nervous system, for example, the pattern of neurotransmitters and neuromodulators released directly dictates the spatiotemporal patterns of activity of the entire network. In the immune system, formation of the immunological synapse results in clustering of cytokine receptors and causes T cells to secrete their vesicular contents into the synapse. Availability of a chemical and physical tool to probe these processes will enhance our understanding of cell-cell communication. To meet this challenge, our project worked to develop a new methodology, based on holographic optical trapping, nanoparticle-based sensors, and microfluidics, for monitoring the spatiotemporal dynamics of cellular communication. Over the course of this project, we have made a number of major research achievements. As an example, we have developed an optical trapping instrument, together with the University of Dundee, that can position in real time a large number (hundred) of nano or microparticles around individual cells as sampling vessels for collecting cellular releasates. To chemically identify and quantify the collected releasates, we have designed and constructed nanoparticle based sensors for monitoring cellular signals when those nanoparticles are positioned around the cell using the optical instruments that we have developed. For this part of the project, we have explored different types of nanoparticles that are most suitable for use in our experiments, such as lipid-based vesicles that are very biocompatible. In addition, we have been exploring different methods to store lipid-based nanoparticles so they can be easily transported for use in other labs, such as to our collaborator at the University of Dundee. We have also found that Correlation Spectroscopy is a much better method for characterizing nanoparticles than established techniques documented in the literature. We have reported these findings in journal publications. Finally, for many of our experiments, we employ microfluidic system to deliver nanoparticles for optical trapping, manipulation, and delivery to cells. Towards this end, we developed a simple interferometric method that turned out to be extremely useful for characterizing microchannels. Shortly after we published this paper, we have already received inquiries from other labs that are planning to duplicate our setup. Some of these groups subsequently notified us that they have successfully implemented this method in their lab. Thus, this technique is already being adopted by other groups. On the educational front, this project provides multidisciplinary training to the graduate students involved: (1) Techniques of microfabrication, (2) Nanomaterial preparation and characterization, (3) Optical spectroscopy, (4) Single-molecule detection and trapping, (5)Colloidal chemistry, and (6) A wide range of biological applications, including cell culture and transfection. Furthermore, the students are trained in writing and presenting scientific data as they publish their results and give talks. The personnel in the lab that work on this project also receive valuable international training, both when our collaborators visit with us and when they go to their lab in Dundee to perform experiments.
