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Technical Program TRACK 6

derstanding for use in enhancing the effectiveness of nanoparticle therapies 4. Tomaiuolo G, Simeone M, Martinelli V, Rotoli B, and Guido S. Soft Matter
for cancer. 2009;5:3736-3740.
5. Tomaiuolo G. Biomicrofluidics 2014;8(5):051501-051501.
6. Kumar A and Graham MD. Soft Matter 2012;8(41):10536-10548.
Red blood cells improve margination of micro-particles for drug 7. Vahidkhah K and Bagchi P. Soft Matter 2015;11(11):2097-2109.
delivery in microcirculation. The effect of particles size and 8. D’Apolito R, Tomaiuolo G, Taraballi F, Minardi S, Kirui D, Liu X, Cevenini A,
shape Palomba R, Ferrari M, Salvatore F, Tasciotti E, and Guido S. Red blood cells
affect the margination of microparticles in synthetic microcapillaries and
intravital microcirculation as a function of their size and shape. J Control Re-
Poster Presentation. NEMB2016-6117 lease, vol. 217, 2015. pp. 263-272.

Giovanna Tomaiuolo, Rosa D’Apolito, Università di Napoli Fed-
erico II, Italy, Napoli, Italy, Francesca Taraballi, Silvia Minardi, A Microfluidic Assay Device for Study of Cell Migration on ECM
Department of NanoMedicine, Houston Methodist Research Insti- Mimicking Suspended Nanofibers in Presence of Biochemical
tute, Houston, TX, USA, Houston, TX, United States, Dickson Kirui, Cues
Naval Medical Research Unit San Antonio, San Antonio, TX, United
States, Armando Cevenini, CEINGE Biotecnologie avanzate, Nap- Poster Presentation. NEMB2016-6128
oli, Italy, Xuewu Liu, Department of NanoMedicine, Houston Meth-
odist Research Institute, Houston, TX, USA, Houston, TX, United Carmen Damico, Virginia Tech, Blacksburg, VA, United States, Ma-
States, Roberto Palomba, Mauro Ferrari, Houston Methodist Re- hama A. Traore, Washington University in St. Louis, St. Louis, MO,
search Institute, Houston, TX, United States, Francesco Salvatore, United States, Amrinder Nain, Bahareh Behkam, Virginia Tech,
CEINGE Biotecnologie avanzate, Naples, Italy, Ennio Tasciotti, The Blacksburg, VA, United States
Methodist Hospital Research Institute, Houston, TX, United States,
Stefano Guido, Università di Napoli Federico II, Italy, Naples, Italy Many in vivo biological processes including wound healing, cancer metas-
tasis, and embryogenesis are driven by chemotaxis and guided by physical
In the last years, nano-carriers have been recognized as a promising strategy stimuli. Many research works have investigated chemotaxis and durotaxis
in the drug development process, thanks to the many advantages in com- separately; however, the combined effect, critical to fully recapitulating in
parison with current therapies. Exploiting host physiological mechanisms, vivo processes, is not well studied. The fibrous extracellular matrix (ECM)
nano-delivery systems can been engineered ad hoc. In particular, the use of provides cells with simultaneous material (N.m-2) and structural stiffness
nano-scaled systems for the treatment of cancer has been focused on the (N.m-1) gradients. Durotaxis has traditionally been investigated by studying
well-known enhanced permeability and retention effect (EPR) [1]. EPR results cell migration on gels of varying elastic modulus, while the role of structural
in an increase of vessels permeability and impaired lymphatic drainage within stiffness gradients in cell motility remains largely unexplored. In this study,
the pathological tissues, allowing preferential passage and retention of circu- we present a microfluidic assay device that can be utilized to investigate the
lating drug carriers. A plethora of different carriers have been functionalized role of concurrent biochemical and biophysical cues of suspended fibers on
to exploit the EPR, but, most of them showed different limitations due to the single cell NIH/3T3 mouse fibroblast migration.
biological barriers [2]. The interaction with red blood cells (RBCs) in the micro-
circulatory network, and the carrier’s margination - the mechanism according The non-electrospinning Spinneret-based Engineered Tunable Parameters
to which particles migrate along vessel radius to the vessel wall - could rep- (STEP) fiber manufacturing technique was used to deposit ECM mimicking,
resent the two main limitations in the blood stream for the delivery carrier [3]. suspended, 500 nm diameter, polystyrene (PS) nanofibers on a 2 mm × 5
Blood cannot be considered as a homogeneous fluid but as a concentrated mm × 0.125 mm flat PS substrate with a 1.7 mm × 1.7 mm square cutout. The
suspension of RBCs. RBCs are deformable objects [4, 5], which are distanced nanofiber scaffold was integrated in a gradient-generating microfluidic de-
from vessel wall creating a RBC-rich core in the center of the vessel and a vice with a quasi-steady, linear biochemical gradient. The microfluidic device
cell-free layer (CFL) in proximity of the vessel’s wall [6]. The phenomenon of was fabricated from polydimethylsiloxane (PDMS) using standard soft lithog-
margination happens once a carrier is injected in the blood stream and it is raphy techniques. The device is composed of diffusive mixing channels and
normally displaced in the proximity of the CFL [7] in a size and shape depen- an observation channel (2.2 × 16 mm2). A linear gradient of platelet-derived
dent manner [8]. Independently on the targeting mechanism of choice in the growth factor (PDGF) was established in the observation channel (i.e. bio-
design of a drug delivery system, the margination propensity of a specific chemical cues) and scaffolds with suspended, aligned nanofibers were
particle is an essential parameter to maximize the interactions with the vessel placed in the microfluidic device observation channel. The nanofibers are
wall and potentially augment the targeting. oriented in the direction of the biochemical gradient and provide a struc-
tural stiffness gradient (i.e. biophysical cues). In such a configuration, the
Although margination has been modeled by numerical simulations and in- structural stiffness is highest at the fixed ends and lowest in the middle of
vestigated in model systems in vitro, experimental studies including RBCs the fiber span length, whereas the biochemical concentration is the lowest
are lacking. Here, we evaluated the effect of RBCs on different drug delivery at one fixed end and highest at the other end of the fiber span length. Cells
systems margination through microfluidic studies in vitro and by intravital were seeded onto the nanofibers in the microfluidic device and time-lapse
microscopy in vivo. We showed that margination, which is almost absent images of the fibroblast cells were taken every 10 minutes for 12 hours. Con-
when particles are suspended in a cell-free medium, have been drastically trol experiments without the biochemical gradient or without the structural
enhanced by RBCs. This effect is size- and shape-dependent, larger spher- stiffness gradient (flat) were also conducted to decouple the effects of these
ical/discoid particles being more effectively marginated both in vitro and in two stimuli on cell migration. The cell positions were used to evaluate veloc-
vivo [8]. We demonstrated that our in vitro system could be a good model to ity (displacement/time), persistence (displacement/total distance travelled),
study the margination of micro and nano-carriers. These results are relevant and chemotactic index (distance travelled in the direction of the biochemical
for the design of drug delivery strategies based on systemically adminis- signal/total distance travelled) as a function of the global biochemical gradi-
tered carriers. ent and local structural stiffness. Our preliminary results suggest durotactic
gradients presented by the structural stiffness (N.m-1) of suspended fibers
1. Matsumura Y and Maeda H. Cancer Res 1986;46(12 Pt 1):6387-6392. can influence cell response to the biochemical gradient. Cells migrating to-
2. Blanco E, Shen H, and Ferrari M. Principles of nanoparticle design for ward the region of increasing structural stiffness and increasing biochemical
overcoming biological barriers to drug delivery. Nat Biotechnol, vol. 33. Unit- concentration tend to have higher persistence than cells moving toward the
ed States, 2015. pp. 941-951. region of decreasing structural stiffness and increasing biochemical concen-
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3. Carboni E, Tschudi K, Nam J, Lu X, and Ma AW. AAPS PharmSciTech tration. This platform enables us to quantitatively investigate cell migration
2014;15(3):762-771. with both cooperating and opposing biochemical and structural stiffness