7 research outputs found
Controlling assembly of helical polypeptides via PEGylation strategies
Recent studies in our laboratories have demonstrated that a helical polypeptide (17H6), equipped with a histidine tag and a helical alanine-rich, glutamic-acid-containing domain, exhibits pH-responsive assembly behavior useful in the production of polymorphological nanostructures. In this study, the histidine tag in these polypeptides was replaced by polyethylene glycol (PEG) with different molecular masses (5 kDa, or 10 kDa), and the self-association behavior of 17H6 and the PEGylated conjugates was characterized via dynamic light scattering (DLS), small angle neutron scattering (SANS), and cryogenic transmission electron microscopy (cryo-TEM). DLS experiments illustrated that the polypeptide and its PEG-conjugates undergo reversible assembly under acidic conditions, suggesting that the aggregation state of the polypeptide and the conjugates is controlled by the charged state of the glutamic acid residues. Nanoscale aggregates were detected at polypeptide/conjugate concentrations as low as 20 μM (∼0.3-0.5 mg ml -1) at physiological and ambient temperatures. Scattering and microscopy results showed that the size, the aggregation number, and the morphology of the aggregates can be tuned by the size and the nature of the hydrophilic tag. This tunable nature of the morphology of the aggregates, along with their low critical aggregation concentration, suggests that PEG-alanine-rich polypeptide conjugates may be useful as drug delivery vehicles in which the alanine-rich block serves as a drug attachment domain.National Institutes of Health (NIH); National Center for Research Resources (NCRR) (1-P20-RR017716; 1-RO1-EB006006; P30-RR031160; National Aeronautics and Space Administration (NA68-01923); Center for Neutron Science at University of Delaware (70NANB7H6178
Injectable Solid Peptide Hydrogel as a Cell Carrier: Effects of Shear Flow on Hydrogels and Cell Payload
β-hairpin peptide-based hydrogels are a class of
injectable
solid hydrogels that can deliver encapsulated cells or molecular therapies
to a target site via syringe or catheter injection as a carrier material.
These physical hydrogels can shear-thin and consequently flow as a
low-viscosity material under a sufficient shear stress but immediately
recover back into a solid upon removal of the stress, allowing them
to be injected as preformed gel solids. Hydrogel behavior during flow
was studied in a cylindrical capillary geometry that mimicked the
actual situation of injection through a syringe needle in order to
quantify effects of shear-thin injection delivery on hydrogel flow
behavior and encapsulated cell payloads. It was observed that all
β-hairpin peptide hydrogels investigated displayed a promising
flow profile for injectable cell delivery: a central wide plug flow
region where gel material and cell payloads experienced little or
no shear rate, and a narrow shear zone close to the capillary wall
where gel and cells were subject to shear deformation. The width of
the plug flow region was found to be weakly dependent on hydrogel
rigidity and flow rate. Live–dead assays were performed on
encapsulated MG63 cells 3 h after injection flow and revealed that
shear-thin delivery through the capillary had little impact on cell
viability and the spatial distribution of encapsulated cell payloads.
These observations help us to fundamentally understand how the gels
flow during injection through a thin catheter and how they immediately
restore mechanically and morphologically relative to preflow, static
gels