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TRACK 6 TRACK 6 Technical Program

We hypothesize that the large excess of non-aggregated GNPs (thus back- 4. Philippar, U., et al. Developmental Cell, 2008. 15(6): p. 813-28.
ground) for higher probe concentration explains the less sensitive detection. 5. Hernandez, L., et al. Cancer Research, 2009. 69(7): p. 3221-7.
Increasing the GNP size (from 15nm to 50nm) improves the sensitivity as 6. Mosadegh, B., et al. Biotechnol Bioeng, 2008. 100(6): p. 1205-13.
well as peak shift (thus signal) by up to 3-fold. Current sensitivity is similar to 7. Saadi, W., et al. Biomedical Microdevices, 2006. 8(2): p. 109-118.
lateral flow assay and future work is needed to improve sensitivity. Our work 8. Wang, S.J., et al. Exp Cell Res, 2004. 300(1): p. 180-9.
presents guidelines to rationally design this nanoparticle assay for better 9. Yamada, K.M. and E. Cukierman. Cell, 2007. 130(4): p. 601-610.
sensitivity and signal strength. 10. Griffith, L.G. and M.A. Swartz. Nat Rev Mol Cell Biol, 2006. 7(3): p. 211-24.
11. Abhyankar, V.V., et al., Lab on a Chip, 2008. 8(9): p. 1507-15.
12. Haessler, U., et al., Biomedical Microdevices, 2009. 11(4): p. 827-35.
Development of a Microfluidic Device with Dual Channels for 13. Polacheck, W.J. et al. Proceedings of the National Academy of Sciences
Growth Factor Gradient on Breast Cancer Chemotaxis in Three of the United States of America, 2011. 108(27): p. 11115-11120.
Dimensions
Utilization of a 3D In Vitro Tumor Platform to Study Nanoparticle
Poster Presentation. NEMB2016-6107
Transport
Alican Ozkan, The University of Texas at Austin, Austin, TX, United Poster Presentation. NEMB2016-6111
States, M Nichole Rylander, Univeristy of Texas at Austin, Austin,
TX, United States
Kameel Isaac, The University of Texas at Austin, Austin, TX, United
An important factor in tumor development and metastatic potential is directed States, M Nichole Rylander, Univeristy of Texas at Austin, Austin,
migration of cancerous cells. Spatial and temporal gradients intrinsic to the TX, United States
tumor microenvironment, significantly mediates migration. Current research
suggests that the altered tumor microenvironment may drive cancer aggres- Cancer is a major health problem worldwide, accounting for one in 4
sion and metastatic potential [1]. Steep growth factor gradients in tumor mi- deaths in the United States alone. Significant progress in nanomedicine has
croenvironment, result from the combined effects of high interstitial fluid pres- been made in order to develop therapies for cancer, particularly related to
sure, dense extracellular matrix (ECM), and poor perfusion [2, 3]. It has been enhanced photothermal and photochemical treatments. These nanotech-
hypothesized that tumor motility and aggressive migration may be caused in nology-based cancer treatments have the potential to provide localized,
part by chemotaxis in response to these gradients [1]. In particular, breast tu- targeted therapies to enhance efficacy and reduce side effects, thereby im-
mor cells are susceptible to gradients in epidermal growth factor (EGF) due to proving patients’ quality of life. Understanding the distribution and transport
overexpression of EGF receptors and related proteins and receptors [4,5]. of nanoparticles (NPs) in the tissue as a function of physiological conditions
(e.g. matrix properties and hemodynamics) and nanoparticle dimensionality
With recent advances in tissue engineering, microfluidic techniques and is critical to optimizing particle design for maximizing delivery and efficacy.
fabrication, using soft lithography-based two-dimensional polydimethylsilox- Most commonly, 2D in vitro cell cultures have been used to study NPs and
ane (PDMS) perfusion chambers, of in vitro tissue microenvironments. Some their interaction with tumor cells, but do not capture the essential features
studies have been performed investigating the effect of EGF concentration of the tumor microenvironment including matrix mechanics, hemodynamics,
on chemotaxis [6, 7]. Additionally, other studies investigated how the shape and the elevated interstitial pressure. In vivo models have been used and
of EGF gradients (linear or nonlinear polynomial) and the magnitude regulate do capture the tumor microenvironment, but they can be highly variable and
chemotaxis of MDA-MB-231 metastatic human breast cancer cells [8]. a large number of animals are needed making them cost prohibitive for NP
Although, these studies are insightful, the complex mechanical, chemical, optimization. 3D in vitro platforms however are capable of characterizing the
and perfusion components of the tumor microenvironment have not yet transport and efficacy of NPs as well as facilitating cell attachment, prolifer-
been successfully recapitulated. Previous studies have focused on un- ation, and infiltration, reducing the expense associated with in vivo models
derstanding specific biological cues rather than improving the fidelity of and inaccuracy of 2D in vitro models.
the microenvironment platform. Experiments performed on 2D substrates,
even those treated with extracellular matrix proteins such as collagen or In this study, a 3D microchannel system was employed previously devel-
fibronectin, are unable to provide the three-dimensional microenvironment oped by the Rylander lab. This 3D in vitro model contains a vascularized
which has been repeatedly shown to have a momentous effect on cell collagen type I tumor microchannel polymerized in FEP tubing. Within the
morphology, signaling, and migration through mechanical and structural in- microchannel we created an endothelialized vessel by fitting in a stainless
teractions [9,10]. Studies in three-dimensional matrices generally lack direct steel needle capped with PDMS sleeves. After polymerization and removal
perfusion of the microenvironment [11, 12] and therefore cells are subjected of the stainless steel needle, the vessel was created and seeded with endo-
to gradients in all growth factors and nutrients. Furthermore, although the thelial cells. Previous studies by the Rylander lab have employed the same
importance of the role of matrix mechanics in tumor aggression has been 3D in vitro microchannel system to study tumor-endothelial signaling and
noted, previous chemotaxis studies have not considered parameters such vascular organization as a function of flow through the channel. This channel
as ECM stiffness [8]. Interactions between microenvironment mechanics and was able to withstand a range of normal, high and low flow shear stresses
self-expressed chemical cues have been studied, but still at low cell con- that are relevant to the tumor microvasculature.
centrations relative to those found in vivo [13].
To replicate the tumor vasculature and investigate the vessel properties on
In this study, we developed a microfluidic tumor platform incorporating a NP transport, we introduced inflammatory agonists such as thrombin (10 U/
physiological concentration of MDA-MB-231 cells in a collagen I hydrogel mL) or histamine (100 M), altering endothelium permeability. To measure ves-
scaffold with a fully three-dimensional geometry. The device is perfused at sel permeability, 70 kDa Oregon green-conjugated dextran was perfused
physiological flow rates using two parallel channels (dual channels) with di- into the channel and imaged to measure fluorescence intensity over time.
ameters comparable to microvasculature. We have quantified chemotaxis in The FEP tubing and the water bath were used to allow refractive matching
response to EGF gradients of varying magnitude formed by diffusion of EGF for undistorted imaging. Flow was introduced into the microfluidic chan-
from one channel into the surrounding hydrogel. nel with a syringe pump producing wall shear stresses of 1-15 dynes/cm2.
Nanoparticles of different sizes ranging from 50-100 nm were introduced
1. Roussos, E.T., J.S. Condeelis, and A. Patsialou. Nature Reviews Cancer, into the flow of the microchannel and images were acquired using a Zeiss
2011. 11(8): p. 573-587. epifluorescent microscope in the span of 72 hours recorded at 10 minute in-
2. Minchinton, A.I. and I.F. Tannock. Nature Reviews Cancer, 2006. 6(8): p. tervals. By imaging the channels, we were able to determine the transport of
583-592. nanoparticles as a function of time, permeability, and NP dimensionality. Use 83
3. Whatcott, C.J., et al., P.J. Grippo and H.G. Munshi, Editors. 2012: Trivan- of our 3D in vitro system enabled investigation of the dynamic nanoparticle
drum (India). transport within a physiologically relevant system providing fundamental un-