2 research outputs found
Using EPR Spectroscopy as a Unique Probe of Molecular-Scale Reorganization and Solvation in Self-Assembled Gel-Phase Materials
We describe the synthesis of spin-labeled
bis-ureas which coassemble
with bis-urea gelators and report on self-assembly as detected using
electron paramagnetic resonance spectroscopy (EPR). Specifically,
EPR detects the gel–sol transition and allows us to quantify
how much spin-label is immobilized within the gel fibers and how much
is present in mobile solvent poolsî—¸as controlled by temperature,
gelator structure, and thermal history. EPR is also able to report
on the initial self-assembly processes below the gelation threshold
which are not macroscopically visible and appears to be more sensitive
than NMR to intermediate-sized nongelating oligomeric species. By
studying dilute solutions of gelator molecules and using either single
or double spin-labels, EPR allows quantification of the initial steps
of the hierarchical self-assembly process in terms of cooperativity
and association constant. Finally, EPR enables us to estimate the
degree of gel-fiber solvation by probing the distances between spin-labels.
Comparison of experimental data against the predicted distances assuming
the nanofibers are only composed of gelator molecules indicates a
significant difference, which can be assigned to the presence of a
quantifiable number of explicit solvent molecules. In summary, EPR
provides unique data and yields powerful insight into how molecular-scale
mobility and solvation impact on assembly of supramolecular gels
3D Protein-Based Bilayer Artificial Skin for the Guided Scarless Healing of Third-Degree Burn Wounds in Vivo
Severe
burn injuries can lead to delays in healing and devastating
scar formation. Attempts have been made to develop a suitable skin
substitute for the scarless healing of such skin wounds. Currently,
there is no effective strategy for completely scarless healing after
the thermal injuries. In our recent work, we fabricated and evaluated
a 3D protein-based artificial skin made from decellularized human
amniotic membrane (AM) and electrospun nanofibrous silk fibroin (ESF)
in vitro. We also characterized both biophysical and cell culture
investigation to establish in vitro performance of the developed bilayer
scaffolds. In this report, we evaluate the appropriate utility of
this fabricated bilayered artificial skin in vivo with particular
emphasis on healing and scar formation due to the biochemical and
biomechanical complexity of the skin. For this work, AM and AM/ESF
membranes alone or seeded with adipose-tissue-derived mesenchymal
stem cells (AT-MSCs) are implanted on full-thickness burn wounds in
mice. The healing efficacy and scar formation are evaluated at 7,
14, and 28 days post-implantation in vivo. Our data reveal that ESF
accelerates the wound-healing process through the early recruitment
of inflammatory cells such as macrophages into the defective site
as well as the up-regulation of angiogenic factors from the AT-MSCs
and the facilitation of the remodeling phase. In vivo application
of the prepared AM/ESF membrane seeded with the AT-MSCs reduces significantly
the post-burn scars. The in vivo data suggest that the potential applications
of the AM/ESF bilayered artificial skin may be considered a clinical
translational product with stem cells to guide the scarless healing
of severe burn injuries