School of Molecular Sciences

Seminars

Seminar schedules

All Seminars are on Fridays at 10:00 AM in Biodesign B (BDB) Auditorium B105, unless otherwise stated.

Previous Seminars

1/24/2020

Milica Radisic
University of Toronto  
Towards heart and kidney on-a-chip

Abstract:
Recent advances in human pluripotent stem cell (hPSC) biology enable derivation of essentially any cell type in the human body, and development of three-dimensional (3D) tissue models for drug discovery, safety testing, disease modelling and regenerative medicine applications. However, limitations related to cell maturation, vascularization, cellular fidelity and inter-organ communication still remain. Relying on an engineering approach, microfluidics and microfabrication techniques our laboratory has developed new technologies aimed at overcoming them. Since native heart tissue is unable to regenerate after injury, induced pluripotent stem cells (iPSC) represent a promising source for human cardiomyocytes. Here, biological wire (Biowire) technology will be described, developed to specifically enhance maturation levels of hPSC based cardiac tissues, by controlling tissue geometry and electrical field stimulation regime (Nunes et al Nature Methods 2013, Zao et al Cell 2019). We will describe new applications of the Biowire technology in engineering a specifically atrial and specifically ventricular cardiac tissues, safety testing of small molecule kinase inhibitors, potential new cancer drugs, and modelling of left ventricular hypertrophy using patient derived cells. For probing of more complex physiological questions, dependent on the flow of culture media or blood, incorporation of vasculature is required, most commonly performed in organ-on-a-chip devices. Current organ-on-a-chip devices are limited by the presence of non-physiological materials such as glass and drug-absorbing PDMS as well as the necessity for specialized equipment such as vacuum lines and fluid pumps that inherently limit their throughput. An overview of two new technologies, AngioChip (Zhang et al Nature Materials 2016) and inVADE (Lai et al Advanced Functional Materials 2017) will be presented, that overcome the noted limitations and enable engineering of vascularized liver, heart and kidney as well as studies of cancer metastasis. These platforms enable facile operation and imaging in a set-up resembling a 96-well plate. Using polymer engineering, we were able to marry two seemingly opposing criteria in these platforms, permeability and mechanical stability, to engineer vasculature suitable for biological discovery and direct surgical anastomosis to the host vasculature.
Host: Steve Presse
1/31/2020

Derek Pratt
University of Ottawa  
Mechanisms of Free Radical Oxidation and their Inhibition: from Hydrocarbons to Lipid Bilayers and Living Organisms

Abstract:
The free radical mediated oxidation of hydrocarbons (autoxidation) limits the longevity of all petroleum-derived products. The most important strategy in slowing this process is via the intervention of radical-trapping antioxidants, which are included as additives to most hydrocarbon-based commercial products. Over the years, we have developed new methods to study autoxidation and its inhibition, carried out detailed mechanistic investigations to elucidate how the 4 most common classes of antioxidants (phenols, diarylamines, hindered amines and organosulfur compounds) function, and have used this knowledge to develop new compounds with significantly increased efficacy that are under development for several different applications. In parallel with these efforts, we have strived to apply our knowledge in biological contexts, where lipid autoxidation (peroxidation) has been implicated in virtually every degenerative disease. Yet, the hundreds of clinical trials intended to probe the potential of antioxidants for the treatment and/or prevention of disease have been disappointing at best. Most recently we have developed chemical tools that can be deployed to rigorously quantify the reactivity of antioxidants and investigate the mechanisms that underlie their activity under physiological conditions. These methods, along with advances in chemical and cell biology that enable the specific initiation and monitoring of cellular lipid peroxidation, have enabled us to demonstrate very clearly that the vast majority of the most celebrated compounds simply aren’t very potent – and for very basic chemical reasons. We have identified the molecular characteristics that contribute to potent antioxidant activity under relevant conditions, which underlie the activity of several recently-identified cytoprotective agents that are being advanced to the clinic to treat neurodegeneration and ischemia reperfusion injury. These insights have also enabled the bottom-up design of promising new chemical entities under active investigation.
Host: Sid Hecht
2/7/2020

Emily Pentzer
Texas A&M University  
Using Fluid-Fluid Interfaces and Fundamental Organic Chemistry Reactions to Build Better Materials

Abstract:
Research in the Pentzer lab focuses on using fundamental organic chemistry reactions to dictate materials properties and assemblies. We use the interface between two fluids to prepare higher order hybrid structures and dictate the interfacial properties and intimate connection of dissimilar materials. This talk will report our use of 2D particle surfactants and interfacial polymerization to address composite formation for a number of different applications- from the preparation of Janus nanosheets to the encapsulation of active materials for solvent remediation and imaging. We will show that based on modification of graphene oxide nanosheets, that oil-water, oil-oil, ionic liquid-oil, ionic liquid-water, etc. emulsions can be prepared and that interfacial polymerization results in the formation of capsules with a core of, e.g., ionic liquid, and shell, e.g., of polymer and nanoparticle. We will describe the benefits of these tailored materials, as well as current limitations. Moreover, we will highlight the application of these capsules for: enhanced uptake of carbon dioxide, overcoming mass transfer limitations, removing the need for handling controls upon volume change, as a column packing material for contaminant removal, and as the active material for super capacitors. This work gives access to unique structures and assemblies of interest in a scalable fashion.
Host: Anne Jones
2/14/2020

Leslie Schoop
Princeton University  
From chemical bonds to high mobility in layered materials

Abstract:
In the discipline of chemistry, it is common to have guidelines and heuristics that help to predict how chemical reactions will proceed. We are interested to expand these heuristics to understand electronic properties of inorganic solids. In this talk, I will show how delocalized chemical bonds in certain structural networks allow us to define chemical descriptors that predict so-called topological materials, which is a new form of quantum matter, of interest for their exotic electronic and optical properties. Using these descriptors, we found a layered, antiferromagnetic van der Waals material with very high mobility. These properties have preciously not coexisted in a material that can be mechanically exfoliated. We further implemented our heuristics to discover novel complex topological phases, including magnetic ones, and phases that are in competition with complex structural distortions. The second part of my talk will focus on the concept of chemical exfoliation. With this method, we can exfoliate materials for which the scotch tape method fails. I will show how we were able to synthesize a new chromium chalcogenide this way, which might be a new 2D magnetic material.
Host: Christina Birkel
2/21/2020


 
Visitation weekend: No seminar


Host:
2/28/2020

Justin Sambur
Colorado State University  
Nanoscale imaging of electrochemical energy conversion and storage systems

Abstract:
Energy needs and environmental trends demand a large-scale transition to clean, renewable energy. Nanostructured materials are poised to play an important role in this transition. However, nanomaterials are chemically and structurally heterogeneous in size, shape, and surface structural features. My research group focuses on understanding the correlation between nanoparticle chemistry/structure and functional properties. The first part of my talk will focus on characterizing charge storage mechanisms in single nanoparticles. My lab has developed a high-throughput electro-optical imaging method to selectively probe the battery-like and capacitive-like (i.e., pseudocapacitive) contributions to overall charge stored in single metal oxide nanoparticles. Pseudocapacitors are a promising class of electrochemical energy storage materials that behave electrochemically like capacitors even though the underlying charge storage mechanism is faradaic in nature (like a battery). Pseudocapacitors have the potential to charge/discharge at capacitor-like rates and maintain high energy density. A major challenge in the field is to demonstrate that pseudocapacitors behave electrochemically like a capacitor and the charge storage process is faradaic in nature. It is challenging to do so because pseudocapacitive charging has the same electrical signatures as non-faradaic electrical double layer charging. I will present our recent single particle-level measurements that show (1) individual particles exhibit different charge storage mechanisms at the same applied potential and (2) particle size-dependent pseudocapacitive charge storage properties. The second part of my talk will focus on solar energy conversion using ultrathin semiconductors such as monolayer-thick (ML) two-dimensional (2D) materials such as MoS2 and WS2. ML semiconductors represent the ultimate miniaturization limit for lightweight and flexible power generation applications. However, the underlying solar energy conversion processes in 2D materials is not entirely understood. We developed a correlated laser reflection and scanning photocurrent microscopy approach to study how layer thickness and surface structural features (edges versus basal planes) influence solar energy conversion efficiency. I will highlight our recent wavelength-dependent photocurrent microscopy and current-voltage measurements that revealed charge separation, transport, and recombination pathways in monolayer heterojunction ITO/MoS2/WS2 and ITO/WS2/MoS2 photoelectrodes.
Host: Gary Moore
3/6/2020

Lian Yu
University of Wisconsin - Madison  
Fast surface diffusion of molecular glasses and its role in crystallization and formation of ultrastable glasses by vapor deposition

Abstract:
Glasses are remarkable materials that combine the mechanical strength of crystals and the spatial uniformity of liquids, finding applications in telecommunication, organic electronics, and drug delivery. A central issue in this area is the stability of glasses against crystallization and structural relaxation (aging). We report that surface diffusion can be extremely fast in molecular glasses, outpacing bulk diffusion by up to 8 orders of magnitude at T¬g. This high surface mobility enables fast crystal growth on free surfaces, fast crystal growth in the bulk through micro-fracture, and the formation of ultrastable glasses by vapor deposition with density and energy expected for ordinary glasses aged for millennia. Unlike bulk diffusion, surface diffusion exhibits greater system-to-system variation, slowing down with molecular size and intermolecular hydrogen bonds; this property is associated with the mobility gradient beneath the free surface.
Host: Ranko Richert
3/13/2020


 
Spring Break


Host:
3/20/2020

Kim See
CalTech  
The Subtleties of Redox Chemistry with Multivalent Cations for Next-Generation Batteries

Abstract:
Rechargeable Li-ion batteries revolutionized energy storage but the fundamental limitations imposed by intercalation chemistry and the cost associated with common components in Li-ion cells drive the need for new, less expensive batteries. The search for these so called “beyond Li-ion” technologies include systems based on alternative charge storage mechanisms that promise high theoretical capacity including multielectron redox and redox-induced solid-state phase transitions. To this end, we study sulfur conversion electrodes, multi-electron intercalation cathodes, and metal anodes based on new working ions. This talk will focus on chemistries based on divalent working ions as promising alternatives to lithium-based chemistry. Divalent cations open the door to reversible metal anodes while using abundant and inexpensive resources. The intricacies of divalent cation electrochemistry range from the complex coordination complexes in electrolyte solutions, to unstable interfaces, to difficulties in divalent cation conduction in the solid-state. We will explore aspects of these key challenges in the context of pursuing a new chemistry based on a divalent working ion and a conversion cathode.
Host: Christina Birkel
3/27/2020

Anne Co
Ohio State University  
TBA


Host: Candace Chan
4/2/2020
Thursday
6:30 PM
PSH
Paul Weiss
University of Southern California  
General Lecture - Nanotechnology Approaches to Biology and Medicine

Abstract:
Biology functions at the nanoscale. Thus, there are special opportunities not only to make biological measurements using nanotechnology, but also to interact directly in order to influence biological outcomes. Nanoscience and nanotechnology developed from chemistry, physics, biology, engineering, medicine, toxicology, and a host of other fields. Along the way, we taught each other our problems, challenges, and approaches. The interdisciplinary communication skills that were developed and are now part of our training remain unique to the field. As a result, nanoscience contributes to a wide range of other fields, such as neuroscience and the microbiome.
Host: Ian Gould
4/3/2020

Paul Weiss
UCLA  
Technical Lecture - Precise Chemical, Physical, and Electronic Nanoscale Contacts

Abstract:
Two seemingly conflicting trends in nanoscience and nanotechnology are our increasing ability to reach the limits of atomically precise structures and our growing understanding of the importance of heterogeneity in the structure and function of molecules and nanoscale assemblies. By having developed the “eyes” to see, to record spectra, and to measure function at the nanoscale, we have been able to fabricate structures with precision as well as to understand the important and intrinsic heterogeneity of function found in these assemblies. The physical, electronic, mechanical, and chemical connections that materials make to one another and to the outside world are critical. Just as the properties and applications of conventional semiconductor devices depend on these contacts, so do nanomaterials, many nanoscale measurements, and devices of the future. We discuss the important roles that these contacts can play in preserving key transport and other properties. Initial nanoscale connections and measurements guide the path to future opportunities and challenges ahead. Band alignment and minimally disruptive connections are both targets and can be characterized in both experiment and theory. I discuss our initial forays into this area in a number of materials systems.
Host: Neal Woodbury
4/10/2020

Dongyan Tan
Stony Brook University Medical School  
TBA


Host: Po-Lin Chiu
4/17/2020

Claudia Turro
Ohio State University  
Dual Action Photoactive Transition Metal Complexes for Photochemotherapy

Abstract:
The use of light to activate the action of a drug has become important as mode of cancer therapy, in some cases superior to traditional treatments, because it significantly less invasive and poses low levels of systemic toxicity to the patient. Photoinduced ligand exchange, which can be used to release drugs with spatiotemporal control, together with the production of 1O2, represent important reactions initiated by light with potential applications in photochemotherapy (PCT). These photoinduced reactions of Ru(II) complexes will be presented, along with their activity towards biological targets and cancer cells. Importantly, Ru(II) complexes were recently discovered to undergo multiple photochemical pathways following activation with light, and this property was used to design new dual-action compounds. These new complexes are able to both release a medically relevant compound and to produce 1O2 from the same molecule. These dual-action compounds were shown to exhibit significant enhancement of activity stemming from their ability to target cancer and/or induce cell death via two different, independent pathways. New strategies developed for the photoinduced exchange of pyridine-containing drugs and methods to selectively target cancer tissue. These new dual- action complexes provide a new platform for drug delivery and enhanced therapeutic activity upon excitation with low energy light.
Host: Gary Moore
4/24/2020

Sheryl L. Wiskur
University of South Carolina  
Asymmetric Silylation: Understanding catalyst substrate interactions and reaction selectivity

Abstract:
Asymmetric silylation has been employed recently to obtain enantiomercially enriched alcohols that have been difficult to obtain otherwise. We have also been exploring the mechanism of this reaction and the supramolecular interactions that control the selectivity of the reaction. Specifically, electrostatic interactions, such as cation-pi interactions are hypothesized to be one of many controlling factors in reaction selectivity, and we are interested in obtaining a better understanding of this supramolecular interaction as it relates to asymmetric catalysis. Our group uses physical organic techniques, such as linear free energy relationships, to understand reaction mechanisms which includes the intermolecular interactions that aid in controlling these reactions. In this talk we will show how we use our silylation-based kinetic resolution as a model reaction to explore how changes in the pi system of the substrate affect the selectivity of the reaction. Since the hypothesized intermediate is a silylated cationic catalyst, changes in the substrate’s pi system should affect the affinity to the catalyst which ultimately affects the selectivity. This talk will focus on some of these aspects, and some other new areas we are working in.
Host: Ryan Trovitch