Page 88 - ASME_NEMB_2016_Program

Technical Program TRACK 6

tinuous digital gradients of surface bound cues on ultra-soft substrates. We An Experimentally Validated Biophysical Model for Candida albi-
used this technique to compare myoblast growth and haptotaxis on soft and cans Interactions with Nanofiber-textured Surfaces
hard substrates. Our results show significant differences between the two
substrates when looking at cellular phenotype, migration speed, and re- Poster Presentation. NEMB2016-6130
sponse to patterned gradients. These results provide insight into the poten-
tial interplay between the wide range of mechanical and chemical cues that
cells are presented with in vivo, and our techniques may be used to probe Zhou Ye, AhRam Kim, Amrinder Nain, Bahareh Behkam, Virginia
these relationships more accurately in the future. Tech, Blacksburg, VA, United States

Candida albicans is a common human pathogen that can cause infection
of the skin, oral cavity, esophagus, vagina and vascular system. C. albicans
Cellular Plasma Membrane-Bound DNA Nanostructures
biofilms formed on prosthetic devices and implants are resistant to most of
the traditional antifungal treatments. Alternative strategies, such as applying
Poster Presentation. NEMB2016-6113 micro/nano-scale textures on such biomedical surfaces are envisioned to
provide an effective route to reduce the C. albicans adhesion and biofilm
Molly Y. Mollica, Ehsan Akbari, Christopher Lucas, Jonathan formation. Previous work by us and others has demonstrated the efficacy
Song, The Ohio State University, Columbus, OH, United States, Car- of nanopatterns in reducing microbial adhesion. However, a quantitative
los Castro, Ohio State university, Columbus, OH, United States study of the effect of the geometry and size of nanopatterns on microbial
adhesion and biofilm formation is lacking. Herein, we report a biophysical
Structural DNA Nanotechnology techniques have enabled the design and model that describes the total free energy of C. albicans cells adhered to
synthesis of complex 3D nanostructures with dynamically controllable fea- nanofiber-textured surfaces as a function of the nanofiber diameter and
tures that exploit molecular self-assembly principles. In order to enhance spacing, and the relative position of the cell with respect to the nanofibers.
our understanding of interactions and phenomena that govern membrane This total free energy is comprised of the adhesion energy and the elastic
function and behavior, multiple attempts have been made to anchor DNA deformation energy. Upon adhesion to a surface, cell undergoes deforma-
nanostructures to artificially synthesized vesicles. While attaching DNA tion to gain energy by maximizing its contact area with the substrate. The
nanostructures to vesicles has increased our understanding of their dy- adhesion process will also involve energy loss due to stretching of the cell
namics on a 2D lipid bilayer along with studying plasma membrane fluidity, membrane. The minimization of total free energy will then determine the
creating synthetic membrane channels, and programming vesicle transpor- final shape of the cell interacting with the fiber-textured surface. When the
tation, attaching DNA nanostructures to living cells is imperative in order to spacing of nanofibers is larger than the cell diameter, a cell can only interact
dynamically study the transmembrane cellular interactions. In addition, the with a single fiber. The cell shape and total free energy are both functions
ability to attach DNA nanostructures with strategically designed features of the cell position relative to the fiber. Our experimental results show that,
to a live cell enables novel techniques to study cell-cell and cell-substrate when interacting with a single fiber, a cell continuously moves and adjusts its
interactions. Due to obstacles such as membrane-bound protein interfer- position until it reaches the position with lowest free energy. Similar behavior
ence, cellular endocytosis, and DNA nanostructure instability in cell culture is observed when the spacing of fibers is smaller than the diameter of the
conditions, however, living cell membrane-bound DNA nanostructures have cell, and one cell interacts with multiple fibers. By extension, our model also
not yet been reported. The objective of this study is to establish robust predicts the extent of biofilm formation on nanopatterned surfaces wherein
methods to integrate DNA origami nanostructures onto cell membranes. We the surface design that yields the highest cell free energy is expected to
hypothesize that with appropriate structure design and attachment scheme, yield the least cell attachment density. The modeling results were experi-
we can overcome the aforementioned cell-specific barriers to nanostructure mentally validated by quantifying C. albicans attachment density on polysty-
binding. To achieve this, a honeycomb lattice DNA origami platform was de- rene nanofiber-textured surfaces as a function of fiber diameter (diameter:
signed in caDNAno with strategically located overhang oligonucleotides that 0.5 - 2 µm) for fixed fiber spacing of 2 µm. Consistent with the experimental
bind to cholesterol-modified oligonucleotides. Agarose gel electrophoresis findings, our model predicts a biphasic relation between cell attachment
and transmission electron microscopy were used to establish optimal folding density and fiber diameter wherein the minimum cell attachment density is
conditions, confirm well-folded structures, and verify nanostructure stability observed at 1 µm fiber diameter. This biophysical model can be extended to
in cell-culture conditions. Due to the hydrophobic nature of cholesterol, cho- other nanostructures and microorganisms for ab initio biomaterial design.
lesterol-modified oligonucleotides embed into the cell’s plasma membrane.
This was confirmed by fluorescently labeled oligonucleotides with the re-
verse complement sequence of the cholesterol-oligonucleotides binding Magnetite nano needles for single cell analysis
to the cell membrane in the presence of cholesterol-oligonucleotides and
not binding in their absence. Attachment of the DNA nanostructure to live Poster Presentation. NEMB2016-5947
B lymphocytes was confirmed by fluorescently labeling nanostructures and
imaging membrane binding via live cell fluorescence microscopy. These Mincho Kavaldzhiev, Jose Perez, King Abdullah University of Sci-
results are the first report of DNA nanostructure attachment to live cells and
display the importance of nanostructure overhang design and stability con- ence and Technology, Thuwal,Saudi Arabia, Jurgen kosel, King
siderations. Future studies include developing methods to attach the DNA Abdullah University of Science & Technology, Thuwal, Select State/
origami nanostructures to other cell types. A particular future focus of this Province,Saudi Arabia
work is the utilization of membrane-bound DNA origami nanostructures to
develop a FRET-output force sensor for inter-endothelial junctions in order Single cell analysis and manipulation is an active research domain that stud-
to enhance our understanding of how the inter-endothelial interactions are ies the heterogeneity of cell populations, investigates with high precision
regulated under the effect of both biomechanical and biochemical stimula- the inner components of living cells and tries to improve the understanding
tions. Moreover, the attachment of cell membrane components to the DNA of cell mechanisms. Developing tools to analyze, for example, drug efficacy,
nanostructure can be utilized to examine the influence of spatial arrange- protein levels, RNA transcripts or pH is key to develop novel treatments and
ment on juxtacrine-induced cell activation and mechanotransduction. An to better understand living organisms. This work focuses on the fabrication
understanding of these inter-endothelial interactions and biophysical param- and characterization of magnetic nano needles as an in-vitro tool for cell
eters will allow us to determine the influence of mechanics on cell growth analysis and manipulation. By using a magnetic material, the needles can be
and signaling, ultimately allowing us to better diagnose and treat diseases remotely actuated, for instance, to exert forces or to generate heat.
such as cancer.
Two different sizes of iron needles were fabricated: 400 nm and 4 µm in di-
88 ameter, with aspect ratios from 1:5 to 1:10. The fabrication of the needles was
done using electron beam lithography coupled with reactive ion etching and
iron electroplating.