1. Theresa Rizk
Mooney Lab for Cell and Tissue Engineering
PI: Dr. David Mooney
Mentor: Theresa Raimondo
Exploring the Role of Phagocytosis in Nanoparticle Directed Macrophage Polarization
Introduction
A current medical challenge involves the complications of chronic inflammation, which
can contribute to many inflammatory diseases including atherosclerosis, asthma, rheumatoid
arthritis, and even cancer [1]. Acute inflammation is a necessary, protective response that kills
invading pathogens, which could otherwise lead to disease and progressive tissue destruction.
Uncontrolled activation of immune cells however, specifically macrophages, leads to chronic
inflammation and can result in tissue damage. Classically-activated macrophages (M1) promote
inflammation through the release of several proinflammatory signals, while alternatively-
activated macrophages (M2) serve a regulatory function as anti-inflammatory cells (M2c), and
play a key role in tissue healing (M2a). Initial research by my mentor suggests that IL-4
conjugated gold nanoparticles promote macrophage polarization towards the M2a phenotype in
vivo, in an animal model of ischemic inflammation. This results in improved functional recovery
of muscle strength following ischemic injury. The aim of my research was to study the
mechanism by which the nanoparticles direct macrophage polarization; more specifically, to
study the role of macrophage phagocytosis in nanoparticle-directed polarization. These results
will be used to direct the next iterations of nanoparticle design.
ResearchSummary
Three drugs are used extensively in the literature to inhibit phagocytosis by different
mechanisms: Chlorpromazine, an inhibitor of clahtrin-dependant endocytosis; Nystatin, an
inhibitor of caveolae-dependent endocytosis; and Cytochalasin D, an inhibitor of
phagocytosis/macropinocytosis [2]. Initial attempts at comparing the effects of these three drugs

2. Theresa Rizk
Mooney Lab for Cell and Tissue Engineering
PI: Dr. David Mooney
Mentor: Theresa Raimondo
indicated cytotoxicity, despite using dosages reported in the literature. The increased cytotoxicity
likely resulted from the increased duration of treatment (3d), as compared to that reported in the
literature (<3hrs); this longer duration was required to observe macrophage polarization and
better represent the in vivo process. This challenge was addressed by making a concentration
curve for each compound, in order to determine the appropriate concentration of each. The
results allowed for choosing adjusted drug concentrations for future experiments which
minimized cell toxicity.
The most recent experiment was then designed to compare the effects of IL4-conjugated
nanoparticles on macrophage polarization with and without phagocytosis inhibition. This was
accomplished by establishing two main experimental groups: cells exposed to free IL4 in
solution, and cells exposed to IL4-conjugated nanoparticles. Each main subset contained a
positive control without inhibiting drugs, in which phagocytosis could occur freely, and
experimental groups with each of the three phagocytosis inhibiting drugs, along with a negative
control group in which cells were not exposed to IL4 at all. The experiment was run successfully,
and several unexpected but informative results were observed. Some were due to unanticipated
interference from the drugs, which continued to reduce viability and interfered with polarization.
Cytochalasin D and Nystatin continued to reduce viability at the adjusted doses; interestingly
however, the viability was improved more significantly following treatment with IL-4
conjugated particles as opposed to soluble IL4. It was also observed that Chlorpromazine was
not effective at inhibiting phagocytosis at the concentration required to minimize cytoxicity,
indicated by a pink cell pellet in the condition containing Chlorpromazine and the red
nanoparticles. Reduced macrophage polarization following treatment with either Cytochalasin D
or Nystatin in the presence of IL4 conjugated nanoparticles or soluble IL4 suggests that

3. Theresa Rizk
Mooney Lab for Cell and Tissue Engineering
PI: Dr. David Mooney
Mentor: Theresa Raimondo
membrane caveolae and actin polymerization are required for IL4 driven M2a macrophage
polarization.
The next priority in the ongoing research is to determine a more effective method of
controlling phagocytosis, either by adjusting the design of the nanoparticles, or conjugating the
IL4 to the surface of the well plate, in order to avoid the unwanted side effects of the drugs
we’ve experimented with thus far. This will allow progress with cleanly examining the effects of
phagocytosis on polarization.
Reflection
My research project thus far has proven to be a wonderful learning experience in
research, experimental design, and overcoming challenges and obstacles. It has been one of my
most involved experiences in terms of problem solving and thinking through complicated results,
as well as a unique opportunity to be part of a project from its beginning. I have enjoyed the
opportunity to guide the project. I have also greatly expanded my knowledge and awareness of
chronic inflammation, it’s implications and solutions, and am continuously more fascinated by
its medical consequences.
Mentors
My faculty mentor, Dr. Mooney, has been kept informed of my research endeavors and
has been very supportive. I plan to present the comprehensive results from the past semester to
him soon after the winter holidays. My lab mentor, Theresa Raimondo, has been closely working
with me from the beginning and has been an invaluable source of experience and guidance.
Funds
The funds thus far have been used to cover my time working in the lab since the
beginning of the semester, in lieu of my usual part-time semester jobs.

4. Theresa Rizk
Mooney Lab for Cell and Tissue Engineering
PI: Dr. David Mooney
Mentor: Theresa Raimondo
References:
1. Cotran; Kumar, Collins (1998). Robbins Pathologic Basis of Disease. Philadelphia: W.B
Saunders Company. ISBN 0-7216-7335-X.
2. Kim, S., & Choi, I.-H. (2012). Phagocytosis and Endocytosis of Silver Nanoparticles
Induce Interleukin-8 Production in Human Macrophages. Yonsei Medical Journal, 53(3),
654–657. http://doi.org/10.3349/ymj.2012.53.3.654