9 research outputs found
Synthesis of a Novel Biodegradable Polyurethane with Phosphatidylcholines
A novel polyurethane was successfully synthesized by chain-extension of biodegradable poly (l-lactide) functionalized phosphatidylcholine (PC) with hexamethylene diisocyanate (HDI) as chain extender (PUR-PC). The molecular weights, glass transition temperature (Tg) increased significantly after the chain-extension. The hydrophilicity of PUR-PC was better than the one without PC, according to a water absorption test. Moreover, the number of adhesive platelets and anamorphic platelets on PUR-PC film were both less than those on PUR film. These preliminary results suggest that this novel polyurethane might be a better scaffold than traditional biodegradable polyurethanes for tissue engineering due to its better blood compatibility. Besides, this study also provides a new method to prepare PC-modified biodegradable polyurethanes
Polymerization of Affinity Ligands on a Surface for Enhanced Ligand Display and Cell Binding
Surfaces
functionalized with affinity ligands have been widely
studied for applications such as biological separations and cell regulation.
While individual ligands can be directly conjugated onto a surface,
it is often important to conjugate polyvalent ligands onto the surface
to enhance ligand display. This study was aimed at exploring a method
for surface functionalization via polymerization of affinity ligands,
which was achieved through ligand hybridization with DNA polymers
protruding from the surface. The surface with polyvalent ligands was
evaluated via aptamer-mediated cell binding. The results show that
this surface bound target cells more effectively than a surface directly
functionalized with individual ligands in situations with either equal
amounts of ligand display or equal amounts of surface reaction sites.
Therefore, this study has demonstrated a new strategy for surface
functionalization to enhance ligand display and cell binding. This
strategy may find broad applications in settings where surface area
is limited or the surface of a material does not possess sufficient
reaction sites
Programmable Hydrogels for Controlled Cell Catch and Release Using Hybridized Aptamers and Complementary Sequences
The ability to regulate cell–material interactions
is important
in various applications such as regenerative medicine and cell separation.
This study successfully demonstrates that the binding states of cells
on a hydrogel surface can be programmed by using hybridized aptamers
and triggering complementary sequences (CSs). In the absence of the
triggering CSs, the aptamers exhibit a stable, hybridized state in
the hydrogel for cell-type-specific catch. In the presence of the
triggering CSs, the aptamers are transformed into a new hybridized
state that leads to the rapid dissociation of the aptamers from the
hydrogel. As a result, the cells are released from the hydrogel. The
entire procedure of cell catch and release during the transformation
of the aptamers is biocompatible and does not involve any factor destructive
to either the cells or the hydrogel. Thus, the programmable hydrogel
is regenerable and can be applied to a new round of cell catch and
release when needed
Aptamer-Based Polyvalent Ligands for Regulated Cell Attachment on the Hydrogel Surface
Natural
biomolecules are often used to functionalize materials
to achieve desired cell-material interactions. However, their applications
can be limited owing to denaturation during the material functionalization
process. Therefore, efforts have been made to develop synthetic ligands
with polyvalence as alternatives to natural affinity biomolecules
for the synthesis of functional materials and the control of cell-material
interactions. This work was aimed at investigating the capability
of a hydrogel functionalized with a novel polyvalent aptamer in inducing
cell attachment in dynamic flow and releasing the attached cells in
physiological conditions through a hybridization reaction. The results
show that the polyvalent aptamer could induce cell attachment on the
hydrogel in dynamic flow. Moreover, cell attachment on the hydrogel
surface was significantly influenced by the value of shear stress.
The cell density on the hydrogel was increased from 40 cells/mm<sup>2</sup> to nearly 700 cells/mm<sup>2</sup> when the shear stress
was decreased from 0.05 to 0.005 Pa. After the attachment onto the
hydrogel surface, approximately 95% of the cells could be triggered
to detach within 20 min by using an oligonucleotide complementary
sequence that displaced polyvalent aptamer strands from the hydrogel
surface. While it was found that the cell activity was reduced, the
live/dead staining results show that ≥98% of the detached cells
were viable. Therefore, this work has suggested that the polyvalent
aptamer is a promising synthetic ligand for the functionalization
of materials for regulated cell attachment
Chimeric Aptamer–Gelatin Hydrogels as an Extracellular Matrix Mimic for Loading Cells and Growth Factors
It is important to synthesize materials
to recapitulate critical
functions of biological systems for a variety of applications such
as tissue engineering and regenerative medicine. The purpose of this
study was to synthesize a chimeric hydrogel as a promising extracellular
matrix (ECM) mimic using gelatin, a nucleic acid aptamer, and polyethylene
glycol. This hydrogel had a macroporous structure that was highly
permeable for fast molecular transport. Despite its high permeability,
it could strongly sequester and sustainably release growth factors
with high bioactivity. Notably, growth factors retained in the hydrogel
could maintain ∼50% bioactivity during a 14-day release test.
It also provided cells with effective binding sites, which led to
high efficiency of cell loading into the macroporous hydrogel matrix.
When cells and growth factors were coloaded into the chimeric hydrogel,
living cells could still be observed by day 14 in a static serum-reduced
culture condition. Thus, this chimeric aptamer–gelatin hydrogel
constitutes a promising biomolecular ECM mimic for loading cells and
growth factors