6 research outputs found
Biomolecule Gradient in Micropatterned Nanofibrous Scaffold for Spatiotemporal Release
Controlled molecule release from scaffolds can dramatically
increase
the scaffold ability of directing tissue regeneration <i>in vitro</i> and <i>in vivo</i>. Crucial to the regeneration is precise
regulation over release direction and kinetics of multiple molecules
(small genes, peptides, or larger proteins). To this end, we developed
gradient micropatterns of electrospun nanofibers along the scaffold
thickness through programming the deposition of heterogeneous nanofibers
of poly(ε-caprolactone) (PCL) and poly(d,l-lactide-<i>co</i>-glycolide) acid (PLGA). Confocal images of the scaffolds
containing fluorophore-impregnated nanofibers demonstrated close matching
of actual and designed gradient fiber patterns; thermal analyses further
showed their matching in the composition. Using acid-terminated PLGA
(PLGAac) and ester-terminated PLGA (PLGAes) to impregnate molecules
in the PCL-PLGA scaffolds, we demonstrated for the first time their
differences in nanofiber degeneration and molecular weight change
during degradation. PLGAac nanofibers were more stable with gradual
and steady increase in the fiber diameter during degradation, resulting
in more spatially confined molecule delivery from PCL-PLGA scaffolds.
Thus, patterns of PCL-PLGAac nanofibers were used to design versatile
controlled delivery scaffolds. To test the hypothesis that molecule-impregnated
PLGAac in the gradient-patterned PCL-PLGAac scaffolds can program
various modalities of molecule release, model molecules, including
small fluorophores and larger proteins, were respectively used for
time-lapse release studies. Gradient-patterns were used as building
blocks in the scaffolds to program simultaneous release of one or
multiple proteins to one side or, respectively, to the opposite sides
of scaffolds for up to 50 days. Results showed that the separation
efficiency of molecule delivery from all the scaffolds with a thickness
of 200 μm achieved >88% for proteins and >82% for small
molecules.
In addition to versatile spatially controlled delivery, micropatterns
were designed to program sequential release of proteins. The hierarchically
structured materials presented here may enable development of novel
multifunctional scaffolds with defined 3D dynamic microenvironments
for tissue regeneration
Processing Influence on Molecular Assembling and Structural Conformations in Silk Fibroin: Elucidation by Solid-State NMR
This study is devoted to the deep
evaluation of processing-induced
protein conformation changes by using silk fibroin fibers and their
cast films stabilized by different methods as a model. The control
of the hierarchical assembling of silk fibroin is the key for finely
tuning the biological functions and physical-chemical properties of
the final materials for applications in biomedical fields. However,
previous methods usually only focused on the change of beta-sheet
crystallinity in silk materials, which can not explain a lot of their
specific prosperities generated from different processing methods.
By using complementary solid-state NMR, together with FTIR and DSC
techniques, we for the first time established the correlations between
processing conditions and silk fibroin molecular configurations, and
experimentally assess the presence and quantify the percentage of
the asymmetric 3-fold helical conformation (Silk III) in silk materials,
together with their well-known Silk I-like helix/coil dominated and
Silk II beta-sheet dominated configurations. This work provides a
roadmap for researchers to quantify the percentage of different silk
structures by solid NMR, and further understand how silk molecular
conformations (Silk I-like, II, III) can impact the properties and
functions of different silk materials, that are broadly used today
for different biomedical applications
Silk fibroin porous scaffolds by N<sub>2</sub>O foaming
<p>Silk fibroin has acquired increasing interest for biomedical applications, and namely for the fabrication of scaffolds for tissue engineering, because of its highly positive biological interaction and the possibility to adapt the material to several application requirements by adopting different fabrication methods, in order to make films, sponges, fibers, nets or gels with predictable degradation times. For tissue engineering, in most cases porous scaffolds are required, in some cases possibly <i>in situ</i> forming and therefore fabricated in mild body-compatible conditions. In this work, we present a novel one-step method for the preparation of silk fibroin foams starting from water solutions and using low-pressure nitrous oxide gas as foaming agent. This foaming technique allows preparing fibroin porous scaffolds with easily tunable porosity, in mild processing conditions with the use of a relatively inert foaming agent saturating a fibroin water solution, that could be occasionally injected through a thin needle in the implantation site where expansion and foaming would occur. Optimal foaming processing conditions have been investigated, and the prepared foams have been characterized with Fourier Transform Infrared Spectroscopy (FTIR) compressive mechanical and rheological properties measurements, and by scanning electron microscopy and microCT.</p
Silk Hydrogels of Tunable Structure and Viscoelastic Properties Using Different Chronological Orders of Genipin and Physical Cross-Linking
Catering the hydrogel manufacturing
process toward defined viscoelastic properties for intended biomedical
use is important to hydrogel scaffolding function and cell differentiation.
Silk fibroin hydrogels may undergo “physical” cross-linking
through β-sheet crystallization during high pressure carbon
dioxide treatment, or covalent “chemical” cross-linking
by genipin. We demonstrate here that time-dependent mechanical properties
are tunable in silk fibroin hydrogels by altering the chronological
order of genipin cross-linking with β-sheet formation. Genipin
cross-linking before β-sheet formation affects gelation mechanics
through increased molecular weight, affecting gel morphology, and
decreasing stiffness response. Alternately, genipin cross-linking
after gelation anchored amorphous regions of the protein chain, and
increasing stiffness. These differences are highlighted and validated
through large amplitude oscillatory strain near physiologic levels,
after incorporation of material characterization at molecular and
micron length scales
Biomedical applications of silk and its role for intervertebral disc repair
Intervertebral disc (IVD) degeneration (IDD) is the main contributor to chronic low back pain. To date, the present therapies mainly focus on treating the symptoms caused by IDD rather than addressing the problem itself. For this reason, researchers have searched for a suitable biomaterial to repair and/or regenerate the IVD. A promising candidate to fill this gap is silk, which has already been used as a biomaterial for many years. Therefore, this review aims first to elaborate on the different origins from which silk is harvested, the individual composition, and the characteristics of each silk type. Another goal is to enlighten why silk is so suitable as a biomaterial, discuss its functionalization, and how it could be used for tissue engineering purposes. The second part of this review aims to provide an overview of preclinical studies using silk-based biomaterials to repair the inner region of the IVD, the nucleus pulposus (NP), and the IVD's outer area, the annulus fibrosus (AF). Since the NP and the AF differ fundamentally in their structure, different therapeutic approaches are required. Consequently, silk-containing hydrogels have been used mainly to repair the NP, and silk-based scaffolds have been used for the AF. Although most preclinical studies have shown promising results in IVD-related repair and regeneration, their clinical transition is yet to come. </p
Suicide prevention discussed at the WHO European Ministerial Conference on Mental Health. (Editorial).
Injectable
hyaluronic acid (HA)-based hydrogels compose a promising
class of materials for tissue engineering and regenerative medicine
applications. However, their limited mechanical properties restrict
the potential range of application. In this study, cellulose nanocrystals
(CNCs) were employed as nanofillers in a fully biobased strategy for
the production of reinforced HA nanocomposite hydrogels. Herein we
report the development of a new class of injectable hydrogels composed
of adipic acid dihydrazide-modified HA (ADH-HA) and aldehyde-modified
HA (a-HA) reinforced with varying contents of aldehyde-modified CNCs
(a-CNCs). The obtained hydrogels were characterized in terms of internal
morphology, mechanical properties, swelling, and degradation behavior
in the presence of hyaluronidase. Our findings suggest that the incorporation
of a-CNCs in the hydrogel resulted in a more organized and compact
network structure and led to stiffer hydrogels (maximum storage modulus, <i>E</i>′, of 152.4 kPa for 0.25 wt % a-CNCs content) with
improvements of <i>E</i>′ up to 135% in comparison
to unfilled hydrogels. In general, increased amounts of a-CNCs led
to lower equilibrium swelling ratios and higher resistance to degradation.
The biological performance of the developed nanocomposites was assessed
toward human adipose derived stem cells (hASCs). HA-CNCs nanocomposite
hydrogels exhibited preferential cell supportive properties in in
vitro culture conditions due to higher structural integrity and potential
interaction of microenvironmental cues with CNC’s sulfate groups.
hASCs encapsulated in HA-CNCs hydrogels demonstrated the ability to
spread within the volume of gels and exhibited pronounced proliferative
activity. Together, these results demonstrate that the proposed strategy
is a valuable toolbox for fine-tuning the structural, biomechanical,
and biochemical properties of injectable HA hydrogels, expanding their
potential range of application in the biomedical field