Self-assembly of fibronectin mimetic peptide-amphiphile nanofibers.
2010-06
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Self-assembly of fibronectin mimetic peptide-amphiphile nanofibers.
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2010-06
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Abstract
Many therapeutic strategies incorporate peptides into their designs to
mimic the natural protein ligands found in vivo. A few examples are the
short peptide sequences RGD and PHSRN that mimic the primary and
synergy-binding domains of the extracellular matrix protein, fibronectin,
which is recognized by the cell surface receptor, α5β1 integrin. Even
though scaffold modification with biomimetic peptides remains one of the
most promising approaches for tissue engineering, the use of these
peptides in therapeutic tissue-engineered products and drug delivery
systems available on the commercial market is limited because the
peptides are not easily able to mimic the natural protein. The design of a
peptide that can effectively target the α5β1 integrin would greatly increase
biomimetic scaffold therapeutic potential. A novel peptide containing
both the RGD primary binding domain and PHSRN synergy-binding
domain for fibronectin joined with the appropriate linker should bind α5β1
integrin more efficiently and lead to greater cell adhesion over RGD
alone.
Several fibronectin mimetic peptides were designed and coupled to
dialkyl hydrocarbon tails to make peptide-amphiphiles. The peptides
contained different linkers connecting the two binding domains and
different spacers separating the hydrophobic tails from the hydrophilic headgroups. The peptide-amphiphiles were deposited on mica
substrates using the Langmuir-Blodgett technique. Langmuir isotherms
indicated that the peptide-amphiphiles that contained higher numbers of
serine residues formed a more tightly packed monolayer, but the
increased number of serines also made transferring the amphiphiles to
the mica substrate more difficult. Atomic force microscopy (AFM) images of the bilayers showed that the headgroups might be bent, forming small
divots in the surface. These divots may help expose the PHSRN
synergy-binding domain. Parallel studies undertaken by fellow group
members showed that human umbilical vein endothelial cells and α5β1
integrins immobilized on an AFM tip preferred binding to a fibronectin
mimetic peptide that contained both hydrophilic and hydrophobic
residues in the linker and a medium length spacer.
Most cells require a three-dimensional scaffold in order to thrive. To
incorporate the fibronectin mimetic peptide into a three-dimensional
structure, a single hydrocarbon tail was attached to form a peptideamphiphile.
Single-tailed peptide-amphiphiles have been shown to form
nanofibers in solution and gel after screening of the electrostatic charges
in the headgroup. These gels show promise as scaffolds for tissue
engineering. A fibronectin mimetic peptide-amphiphile containing a linker
with alternating hydrophobic and hydrophilic residues was designed to form nanofibers in solution. The critical micelle concentration of the
peptide-amphiphile was determined to be 38 μM, and all subsequent
experiments were performed above this concentration. Circular
dichroism (CD) spectroscopy indicated that the peptide headgroup of the
peptide-amphiphile forms an α+β secondary structure; whereas, the free
peptide forms a random secondary structure. Cryogenic-transmission
electron microscopy (cryo-TEM) and small angle neutron scattering
showed that the peptide-amphiphile self-assembled into nanofibers. The
cryo-TEM images showed single nanofibers with a diameter of 10 nm
and lengths on the order of microns. Images of higher peptideamphiphile
concentrations showed evidence of bundling between
individual nanofibers, which could give rise to gelation behavior at higher
concentrations. The peptide-amphiphile formed a gel at concentrations
above 6 mM. A 10 mM sample was analyzed with oscillating plate
rheometry and was found to have an elastic modulus within the range of
living tissue, showing potential as a possible scaffold for tissue
engineering.
Description
University of Minnesota Ph.D. dissertation. June 2010. Major: Chemical Engineering. Advisor: Efrosini Kokkoli. 1 computer file (PDF); xv, 124 pages. Ill. (some col.)
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Rexeisen, Emilie Lynn. (2010). Self-assembly of fibronectin mimetic peptide-amphiphile nanofibers.. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/94027.
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