93 research outputs found
Microstructural changes of globules in calcium-silicate-hydrate gels with and without additives determined by small-angle neutron and X-ray scattering
Fabrication Process Independent And Robust Aggregation Of Detonation Nanodiamonds In Aqueous Media
In the past detonation nanodiamonds (DNDs), sized 3–5 nm, have been praised for their colloidal stability in aqueous media, thereby attracting vast interest in a wide range of applications including nanomedicine. More recent studies have challenged the consensus that DNDs are monodispersed after their fabrication process, with their aggregate formation dynamics poorly understood. Here we reveal that DNDs in aqueous solution, regardless of their post-synthesis de-agglomeration and purification methods, exhibit hierarchical aggregation structures consisting of chain-like and cluster aggregate morphologies. With a novel characterization approach combining machine learning with direct cryo-transmission electron microscopy and with X-ray scattering and vibrational spectroscopy, we show that their aggregate morphologies of chain and cluster ratios and the corresponding size and fractal dimension distributions vary with the post-synthesis treatment methods. In particular DNDs with positive ζ-potential form to a hierarchical structure that assembles aggregates into large networks. DNDs purified with the gas phase annealing and oxidation tend to have more chain-like aggregates. Our findings provide important contribution in understanding the DND interparticle interactions to control the size, polydispersity and aggregation of DNDs for their desired applications
Fractal Structure of Hydrogels Modulates Stem Cell Behavior
Fractal
dimension (<i>D</i><sub>f</sub>) is an index
to describe the irregular continuous structure by quantifying the
complexity. The concept of fractals has been employed to describe
the complicated structure of polymer gel and human tissue. This study
examined the effect of <i>D</i><sub>f</sub> on cell proliferation
and stem cell differentiation in six polymer hydrogels with <i>D</i><sub>f</sub> ranging from 1.2 to 2.1. It was observed that
fibroblasts and mesenchymal stem cells (MSCs) grew faster in hydrogels
with higher <i>D</i><sub>f</sub>. Moreover, hydrogels with
a fractal structure of <i>D</i><sub>f</sub> ≤ 1.4,
≥1.6, and ≥1.8 promoted the neural, osteogenic, and
chondrogenic differentiation of MSCs, respectively. The fractal structure
of gel can modulate cell proliferation and fate, which provides an
insight into designing the appropriate fractal and molecular structure
of polymer hydrogel for biomedical applications
Structural Evolution of Poly(styrene-b-4-vinylpyridine) Diblock Copolymer/Gold Nanoparticle Mixtures from Solution to Solid State
Biodegradable Water-Based Polyurethane Shape Memory Elastomers for Bone Tissue Engineering
Shape
memory polymers (SMPs) are polymers with the shape memory
effect. The biodegradable SMPs are candidate materials for making
biomedical devices and scaffolds for tissue engineering. Superparamagnetic
iron oxide nanoparticles (SPIO NPs) have recently been reported to
promote the osteogenic induction of human mesenchymal stem cells (hMSCs).
In this study, we synthesized water-based biodegradable shape memory
polyurethane (PU) as the main component of the 3D printing ink for
fabricating bone scaffolds. The 3D printing ink contained 500 ppm
of SPIO NPs to promote osteogenic induction and shape fixity, and
it also contained polyethylene oxide (PEO) or gelatin for the improvement
of printability. Scaffolds were printed by the microextrusion-based
low-temperature fuse deposition manufacturing (LFDM) platform. Both
PU–PEO and PU–gelatin ink showed excellent printability.
Shape memory properties were evaluated in 50 °C air and 37 °C
water. PU–PEO scaffolds showed better shape fixity and recovery
than PU–gelatin scaffolds, while the shape memory properties
in water were better than those in air. hMSCs were seeded for evaluation
of bone regeneration. The proliferation of the hMSCs in PU/gelatin
and PU/gelatin/SPIO scaffolds was greater than that in PU/PEO and
PU/PEO/SPIO scaffolds, confirming the better compatibility of gelatin
vs PEO as the viscosity enhancer of the ink. The gradual release of
SPIO NPs from the scaffolds promoted the osteogenesis of seeded hMSCs.
With SPIO in the scaffolds, the osteogenesis increased 2.7 times for
PU/PEO and 1.5 times for PU/gelatin scaffolds based on the collagen
content. Meanwhile, SPIO release from PU/PEO/SPIO scaffolds was faster
than that from PU/gelatin/SPIO scaffolds at 14 days, consistent with
the better osteogenesis observed in PU/PEO/SPIO scaffolds. We concluded
that 3D printed PU scaffolds with shape memory properties, biodegradability,
and osteogenic effect may be employed to the minimally invasive surgical
procedures as customized-bone substitutes for bone tissue engineering
Functionalized Nanoporous Gyroid SiO<sub>2</sub> with Double-Stimuli-Responsive Properties as Environment-Selective Delivery Systems
Herein, we aim to fabricate nanoporous
gyroid SiO<sub>2</sub> from
templated sol–gel reaction using degradable block copolymer
with gyroid-forming nanostructure as a template and then to functionalize
the nanoporous materials using “smart” polymer, polyÂ(2-(dimethylamino)Âethyl
methacrylate) (PDMAEMA), brushes via the “grafting from”
method to give double-stimuli-responsive properties. By taking advantage
of the responses to environmental stimuli, both thermal and pH, the
pore features can be well-defined by the stretching and recoiling
of PDMAEMA brushes because of their adjustable chain conformations
with reversible character. The responsive properties with respect
to environmental stimuli can be successfully traced by temperature-resolved
small-angle X-ray scattering (SAXS) in aqueous environment. Owing
to the high specific surface area and porosity, 3D pore network, biocompatibility,
and environmental responses, the functionalized nanoporous gyroid
SiO<sub>2</sub> is further demonstrated as a stimuli-responsive controlled
release system
- …