Prof. Mitchell A. Winnik

Mitch Winnik received a B.A. degree from Yale University in 1965. He obtained his Ph.D. degree in the area of organic chemistry at Columbia University in 1969, working under the direction of Prof. Ronald Breslow, and then spent a year as a postdoctoral fellow in the laboratory of Prof. George Hammond at Caltech studying organic photochemistry. He joined the faculty at the University of Toronto in 1970, and received tenure as an organic chemist. After his first sabbatical, in Bordeaux France, he decided that it was time to change directions and begin work on polymers in solution. He and his coworkers prepared a series of polymers with a pyrene group at both ends. The pyrene groups emit a blue fluorescence if the pyrenes are far apart, but if an excited pyrene during its lifetime can find a second pyrene, they form a sandwich structure which emits a green "excimer" fluorescence. In dilute solution, the rate of excimer formation from the end-labeled polymers measures the end-to-end cyclization rate of the polymer chain. For many years, the Winnik group used pyrene fluorescence as a probe of polymer dynamics in solution. In the early 1980's, the Winnik group broadened its interests to encompass polymers as materials. They first looked at polymer particles that formed stable colloidal dispersions (non-aqueous dispersions) in hydrocarbon media and then later turned their attention to latex nanoparticles prepared by emulsion polymerization. Working initially with postdoc Cheng-Le Zhao (now at BASF), he developed fluorescence resonance energy transfer (FRET) methods to study polymer diffusion in latex films. In this way, the Winnik group began a 20 year+ collaboration with various companies on the coatings area. In the 1990s, this was an exciting topic. It bridged fundamental science, where theorists were thinking about how polymer molecules diffuse across interfaces, and practical applications, where scientists in the coatings industry needed this knowledge about latex films to develop new technologies that complied with increasingly stringent environmental regulation. A quarter of a century later, this work continues, as the Winnik group tries to understand film formation in ever more complex industrial coatings systems.In 1998, we began a collaboration with Ian Manners on the self-assembly of polyferrocenylsilane block copolymers in solution.  Through these efforts they discovered crystallization-driven self-assembly (CDSA) leading to novel low-curvature structures. They developed concepts of seeded growth and self-seeding that enabled the generation of a broad range of uniform colloidally stable structures. CDSA has become its own defined area of polymer research and has been applied to many different crystalline-coil block copolymers.Very recently, we have become interested in exploring rod-like nanoparticles as potential drug/radioisotope delivery agents for cancer therapeutics. Our interests are focused on one aspect of this complex problem. We want to understand the factors that promote nanoparticle diffusion in the avascular region of tumors. To study this problem, we generate multicellular tumor spheroids (MCTS) as models for this type of diffusion coupled with cell uptake.  Mass cytometry was invented at the University of Toronto by the scientists who founded DVS Sciences (later Fluidigm Canada, now Standard BioTools). Mass cytometry is a bioanalytical technique for high throughput multiparameter detection of biomarkers on cells. In this technique, antibodies are labeled with heavy metal isotopes. Cells treated with these labeled antibodies are injected into the plasma torch of an inductively coupled plasma time-of-flight mass spectrometer, where the isotopes are analyzed with single mass resolution. As the first instrument was being built (2005 – 2009), it became clear that reagents were needed. Mitch Winnik was approached along with Mark Nitz with the idea of synthesizing metal-chelating polymers to bind lanthanide isotopes, and with end group functionality to attach to antibodies. Working together, we developed the polymers now sold as MaxparÔ reagents. Mass cytometry has had a huge impact on the field of single cell biology, and 2500 papers have been published since 2011 using this technique. Work continues in the Winnik and Nitz group to provide new reagents to expand the scope of this technique.From this list of projects, one can see that the Winnik group is particularly interested in projects that require students and postdocs from different backgrounds and with different areas of expertise to work together in teams. Projects involve polymer and organic synthesis, colloid science, instrumental analysis, especially the measurement and analysis of fluorescence decay profiles, self-assembly, electron microscopy and image analysis. More recently, cell culture and other biochemical techniques have become important. We work closely with industry and welcome students with chemistry, physics, biology, and/or chemical engineering background to the group. Graduates from the group have gone on to careers in industry and in academics.