Page 50 - ASME_NEMB_2016_Program

Technical Program TRACK 4

lical segment is decreased through prolonged plateau regimes where the regeneration. In this regard, current study is expected to set a benchmark
peptide helical content remains constant, and second, the proportion of re- for the upcoming similar research studies as well as in the development of
folding to unfolding is increased. These mechanisms are achieved through clinically feasible biomaterials.
a shielding effect imparted by the PEG chain surrounding the helix surface.
This serves to prevent competing water molecules from replacing forcibly [1] Goldberg M + Crit Rev Oral Biol Med 2004; [2] Gelse K + Adv Drug Deliv
exposed backbone hydrogen bonds, evidenced by an increase in time Rev 2003; [3] Yuan Z + Tissue Eng Part B Rev 2011
required for irreversible breakage of backbone hydrogen bonds and forma-
tion of backbone-water hydrogen bonds. Furthermore, conformation and
proximity of PEG to the helix surface can be tied to specific unfolding events, 4-2
the proportion of which dictates overall unfolding time, indicating that meth-
ods to control PEG conformation such as controlling sequence distribution, NEURAL PROCESSES
conjugation site, or molecular weight are promising avenues for improving
protein stability. Our findings open a new field of research by demonstrating Navarro 9:30am - 11:00am
the feasibility of improving peptide mechanical stability with conjugation.
This provides a basis for future studies on optimizing conjugation location
and chemistry to build novel biomolecules with tunable mechanical proper- Session Organizer: Ying Li, University of Connecticut, Storrs, CT,
ties and tailored functionalities. United States

12:40pm Viscoelastic Properties of Dental Pulp Tissue for Bio- 9:30am Memory under tension
material Development
Keynote. NEMB2016-6147
Technical Presentation. NEMB2016-5925
Taher Saif, University of Illinois At Urbana-Champaign, Urbana, IL,
Burak Ozcan, TOBB University of Economics and Technology, United States
Ankara, Turkey, Dilhan M. Kalyon, Stevens Institute of Technology,
Hoboken, NJ, United States, Jian Zhou, Sahn G. Kim, Jeremy J. The most profound question in biology is how a cluster of neurons gives
Mao, Columbia University, New York, NY, United States, Cevat Er- rise to memory, learning, and ultimately our consciousness and individuali-
isken, TOBB University of Economics and Technology, Ankara, ty. Over the last century, the working principles of neurons and their circuits
Turkey have been looked at from a biochemical and electrical paradigm. Me-
chanical force played no role. In contrast to muscles and bones, neurons
are not part of any load bearing or generation system. Over the last three
A critical step in biomaterial selection effort is the determination of material decades, it has been observed that neurons in vitro generate force, and
as well as biological properties of the target tissue. Previously, selection the direction of the growth cone advance depends on the force on the ax-
of biomaterials and carriers for dental pulp regeneration has based on ons. But the link between neuronal force in vitro and neuronal functionality
empirical experience. However, effective tailoring of biomaterials for tissue
regeneration strictly requires availability of properties of native tissues. The in vivo was not clear. During embryogenesis, growth cones of developing
neurons form junctions with muscle or other neurons creating synapses.
objective of this study is to, for the first time, characterize the linear visco- They cluster neurotransmitters, packed is small (50 nm) vesicles, at the
elastic material functions and compressive properties of dental pulp tissue presynaptic terminal of the synapse. When an action potential arrives at
obtained from miniature pig using small-amplitude oscillatory shear and the synapse, neurotransmitters are released through exocytosis of some
uniaxial compression. These properties were also compared with the prop-
erties of select hydrogels (agarose, alginate and collagen), that are widely of the vesicles. These neurotransmitters excite the post-synaptic terminal.
It is well understood that memory and learning in animals is mediated by
used as biometarials in tissue regeneration.
neurotransmission at the synaptic junctions. The more a synapse is used,
higher is the neurotransmission efficiency (plasticity), i.e., the junction “re-
Pulp tissue is the only soft tissue in tooth, and serves primarily to maintain its members” its use in the near past, and modifies accordingly. This usage
own physiological functions as well as those of dentin through blood supply
and nerves. It is a reservoir of multiple cell types including fibroblasts pop- dependent plasticity offers the basic mechanism of memory and learning.
A central dogma in neuroscience is that, clustering of neurotransmitter ves-
ulated in a matrix of blood vessels and nerve endings. Extracellular matrix icles is the result of a complex biochemical signaling process. We show,
of dental pulp is also rich in terms of collagenous (mostly type 1 and 3) and using embryonic Drosophila (fruit fly) nervous system, that mechanical ten-
non-collagenous (sulfates and proteoglycans) proteins [1]. The cells and the sion in axons is essential for vesicle clustering. Axons of the motor neurons
organic components of the dental pulp all together determine the structural
and functional nature of pulp tissue, with collagen type I likely contributing to develop tension after forming the synapse by shortening. They maintain
the rest tension actively, i.e., if the axon is slackened, it develops tension
its biomechanical properties [2], and proteoglycans mostly contributing to its by shortening. On the other hand, axons relax by growing if tension is
viscoelasticity [1]. Despite reported clinical success, endodontically treated increased by mechanical stretching. In search of the origin of the tension,
teeth become de-vitalized and brittle, as well as susceptible to re-infections we employed a suite of cytoskeleton inhibitory drugs. We found that ax-
due to coronal leakage or microleakage [3]. If dental pulp can be regener-
ated, these complications may be avoided, and many teeth can be saved to ons employ actin-myosin II machinery to generate tension. If tension is
relaxed by severing the axon, vesicle clustering disappears, but reappears
function as native teeth.
if tension is re-supplied to the severed axon. Vesicle clustering increases
with increase in tension in axons applied mechanically. We propose a hy-
The comparisons of the linear viscoelastic material functions of the native pothesis that links axonal tension with vesicle clustering. Initial evidence
pulp tissue with those of the three hydrogels revealed the gel-like behavior
of the pulp tissue over a relatively large range of time-scales, i.e., over the supporting the hypothesis is presented. The study offers a new paradigm
in understanding neurological diseases.
frequency range of 0.1-100 rps. At the constant gelation agent concentration
of 2%, the dynamic properties, i.e., storage and loss moduli, and the tan del-
ta, of the collagen-based gel approached those of the native tissue. Under 10:00am Axonal SK channels Revealed by Force Nanoscopy
uniaxial compression, the peak normal stresses and compressive moduli of
the agarose gel were similar to those of the native tissue, while alginate and Technical Presentation. NEMB2016-6019
collagen exhibited significantly lower compressive properties.
50 Krithika Abiraman, Anastasios Tzingounis, George Lykotrafitis,
Findings suggest that these properties of dental pulp tissue should provide University of Connecticut, Storrs, CT, United States
valuable inputs for the selection of an appropriate biomaterial for dental pulp