(2as) Engineering Macrophages and Biomaterials to Overcome Barriers in Immunotherapies and for Novel Biomedical Applications

Immunotherapy, Macrophages and Phagocytosis, Protein-based Materials, Mechanobiology

My proposed research as an independent investigator falls into two broad categories, which I anticipate will overlap extensively. I envision many opportunities to collaborate with colleagues with expertise in biomaterials science and engineering, protein, cell, and tissue engineering, immunology, and cancer.

(1) Macrophage immunoengineering: “large eaters” with large potential Applying insights from fundamental immunobiology studies of macrophages and phagocytosis toward macrophage immunoengineering for immunotherapy and regenerative engineering applications

Phagocytosis (“cell eating”) is the evolutionarily conserved process by which cells engulf large particulate matter including other cells. It is estimated that macrophages (“large eaters”) phagocytose >10¹¹ cells per day in humans just to maintain homeostasis, hinting at the immense potential that macrophages and phagocytosis could have in transforming health and biotechnology. An obvious application for enhancing macrophage phagocytosis is cancer. Still, there are considerable barriers to realizing this potential including the heterogeneity of macrophages and their potential targets as well as the paucity of studies of phagocytosis in tissues or tissue-like environments. I will leverage biomaterial approaches and cellular engineering methods to address these knowledge gaps. These studies will inform parallel efforts to engineer monocyte/macrophage-based cellular immunotherapies aimed at overcoming current challenges including systemic delivery with accumulation in tumors and scaling production of cell types with limited capacity for ex vivo expansion. Finally, in light of recent advances in vaccine technology including mRNA vaccines that generate high titer antibody responses in humans (e.g, COVID-19 vaccines), I plan to evaluate the potential for engineered macrophages to augment the effects of vaccine-induced antitumor antibodies through effector functions including phagocytosis.

Beyond these applications in immunotherapy, it is interesting to note that macrophages are among the earliest hematopoietic cells to appear in embryonic development, which probably reflects their requirement for shaping tissues via phagocytosis and other processes. Inspired by such developmental process – for example, the sculpting of limb digits – and motivated by my current work to understand how macrophages engulf targets in tissues, I propose to use engineered phagocytotic cells as a tool for tissue patterning toward applications in regenerative medicine.

(2) “Macromolecular chemical biology” Designing and synthesizing macromolecules and macromolecular assembles to interrogate mechanical and transport properties of biological systems, especially the immune system

This area of research builds on my PhD thesis on engineered proteins and protein-based materials and my postdoctoral research including elements of immunology and mechanobiology. One example in this research space is to use the engineered protein sequences I developed in my PhD research to construct particles, films, and gels with highly tunable viscoelastic properties, and to apply these materials to probe the time dependence of mechanobiological processes that underly cell spreading, migration, and differentiation. I am particularly interested in how the viscoelasticity of such materials influences macrophage behaviors like phagocytosis and the foreign body response. Understanding how to modulate such behaviors will help to overcome translational barriers in biomaterials science. A second example of macromolecular chemical biology will be to apply cellular engineering and protein engineering methods with materials science processing and characterization to make engineered cell-derived extracellular vesicles (EVs, including e.g., exosomes and microvesicles). There are several problems in this area I am interested in addressing including the role of the “marker of self” protein CD47 on EV trafficking and cellular uptake, EVs as a source of antigens for generating humoral antitumor immunity, and identifying cellular origins of rare EVs in biological fluids and tissues.

Postdoctoral Research: Macrophage Checkpoint Blockade for Cancer Immunotherapy

(Adviser: Dennis E. Discher, University of Pennsylvania)

In my postdoctoral research, I am developing new approaches to cancer immunotherapy using phagocytic macrophages as effector cells. I have shown that disruption of CD47 signaling from cancer cells, which eliminates the inhibitory CD47:SIRPα immune checkpoint, enhances phagocytosis in vitro and tumor clearance in vivo when combined with an opsonizing antitumor IgG monoclonal antibody. In my preclinical studies, I showed that surviving animals develop an endogenous IgG antibody response suggesting that adaptive immunity feeds back to enhance the effects of macrophage checkpoint disruption. We termed this phenomenon ‘phagocytic feedback’. As a translatable approach that overcomes depletion of healthy cells seen with injection with anti-CD47 monoclonal antibodies being pursued clinically, I am also developing a cellular immunotherapy using adoptive transfer of bone marrow-derived phagocytic cells that are treated ex vivo with anti-SIRPα. In parallel, I have developed in vitro tumoroid assays to begin to address how macrophages engulf cancer cells in solid tumor-like microenvironments. The findings of these experiments indicate that macrophages might work cooperatively to engulf target cells that adhere to one another. I have contributed to other projects in the Discher lab including materials for studying nuclear rupture and DNA damage in migrating cells and other aspects of mechanobiology.

Ph.D. Thesis: “Programming Molecular Association and Viscoelastic Behavior in Protein Hydrogels” (Adviser: David A. Tirrell, California Institute of Technology)

In my Ph.D. research, I designed, fabricated, and characterized protein-based hydrogels with the goal of developing programmable materials in which the primary protein sequence encodes macroscopic viscoelastic properties. This work combined substantial elements of materials science, molecular biology, and protein engineering. These hydrogels have applications as matrices for studying the effects of ECM viscoelasticity on cellular fate, as model systems for studying biomolecular condensates, and for developing tougher hydrogels using reversible, energy dissipating cross-links.

Teaching Interests

Biomaterials, Immunology, Biomolecular Engineering, Nanomedicine and Drug Delivery, Core Chemical Engineering Curriculum

My undergraduate and graduate training were both in Chemical Engineering, and I would be comfortable teaching the core undergraduate courses in transport phenomena, kinetics, and thermodynamics. My graduate and postdoctoral research and previous teaching experience has prepared me to teach courses in biotechnology and biomolecular engineering at the graduate and undergraduate levels. I envision designing graduate or advanced undergraduate level courses at the interface of immunology and chemical and biological engineering with a strong basis in recent literature and current health challenges. The course(s) would be a hybrid of immunological fundamentals (e.g., immune cells and tissues, immunological biomolecules and macromolecular assemblies, immune signaling) and biomedical applications (development and biomanufacturing of antibodies, vaccines, and cellular therapies, immunological assays and methods, immunological responses to biomaterials).

In addition to core and elective engineering courses, I am interested in developing or coordinating a course focusing on research skills for graduate students and upper-level undergraduates. Topics would be tailored to the specific needs of the students and potentially include data presentation and scientific illustration, library and digital resources, proposal writing and overviews of research funding organizations, responsible conduct of research, and others. I would seek to leverage existing resources at the university (e.g., librarians, graphic artists, research services) or within department to cover these topics.

Teaching Experience

My teaching experience includes teaching assistantships for a graduate level cell engineering course and an undergraduate (junior/senior) level biomolecular engineering laboratory. I have guest lectured (2-5 classes per semester) for Nanoscale Systems Biology and Biological Soft Matter Fundamentals courses. I view mentoring as an important component to teaching and have mentored researchers across multiple levels including undergraduates and master’s thesis students. I also supervised high students and teachers as part of summer research outreach program.