12 research outputs found
Contribution of exogenous humic substances to phosphorus availability in soil-plant ecosystem: A review
Phosphorus (P) is one of the largest nutrients limiting crop productivity. Meanwhile, P deficiency is a common phenomenon in agricultural soils around the world. Humic substances, as macromolecular polymer, accelerate and strengthen process which transforms P into bio-available forms via a range of chemical reactions and biological interactions. There is now an urgent need to comprehend the work carried out on the interaction among humic substances, soil and plant to better understand their role in the transformation and promotion of soil bioavailable P for plant growth. Herein, we discuss the factors and mechanisms of humic substances influencing P cycling in soil-plant systems, which focus on their contribution to soil P mobilization and plant P acquisition. This review covers how humic substances influence the mobilization and transformation of P in soils, including release of P from residues, and competitive adsorption of P and humic acid or fulvic acid to metallic minerals, as well as exchange with P adsorbed by humic substances. It then discusses a range of contributions to plant available P acquisition such as the release of organic acids from roots caused by humic substances, and promoting the solubilize and/or hydrolyze phosphate by plant and their associated microbes. Notably, we also discuss the challenges of artificial humic substances influencing P cycling in soil-plant systems, which may alleviate the global deficit of soil P resources. Overall, humic substances have become promising for sustainable agriculture over time and have great potential to meet specific soil-plant systems.</p
Facet-Specific Mineralization Behavior of Nano-CaP on Anatase Polyhedral Microcrystals
Biomimetic mineralization
of nanocalcium phosphate (CaP) on metal
oxide surfaces has gained great interest because of their relevance
to osseointegration performance of implant materials. However, precisely
controlling the nucleation behavior of mineralized nano-CaP on metal
oxide at selective sites still remains a challenge. Here, we demonstrate
a phenomenon on facet-specific mineralization on anatase TiO<sub>2</sub> polyhedral microcrystals organized by two facets of {101} and {001}
in complete cell culture medium: nano-CaP covers up {101} facets,
while there are a few on {001} facets. The comparative experimental
results indicate that the preadsorbed fetal bovine serum (FBS) protein
on {001} facets might play a barrier role in preventing sequential
nucleation of nano-CaP. This work thus provides insight into the understanding
of mineralization on metal oxides, and a way to control the mineralization
Visible-Light-Responsive Surfaces for Efficient, Noninvasive Cell Sheet Harvesting
Effective regulation
of cell-surface interactions is critical for regenerative medicine
and other cell-based therapies. Herein, visible-light-induced cell
sheet harvesting based on silicon wafers with a p/n junction [SiĀ(p/n)]
is introduced. Cell sheets could quickly detach from the SiĀ(p/n) surface
after 10 min of visible-light illumination with maintained cell viability
and functions. It is found that preadsorbed proteins on the SiĀ(p/n)
surface like BSA and collagen-I show light-induced desorption behaviors.
Molecular dynamics simulation also indicates that long-range force
caused by the photovoltaic effect of SiĀ(p/n) under visible-light illumination
plays a key role in triggering the release of the preadsorbed protein.
It is suggested that such protein desorption behavior mediated by
the photovoltaic effect is responsible for cell release. This work
not only shows promising potential for cell sheet harvesting, but
also provides new insights into proteināmaterial interactions
Cell-Sheet-Derived ECM Coatings and Their Effects on BMSCs Responses
Extracellular matrix
(ECM) provides a dynamic and complex environment
to determine the fate of stem cells. In this work, light harvested
cell sheets were treated with paraformaldehyde or ethanol, which eventually
become ECM. Such ECM was then immobilized on titanium substrates via
polydopamine chemistry. Their effects on bone marrow mesenchymal stromal
cells (BMSCs) behaviors were investigated. It was found that paraformaldehyde-treated
ECMĀ coating (PT-ECM) showed a well-maintained microstructure,
whereas that of ethanol-treated (ET-ECM) was completely changed. As
a result, different amide structures and distributions of ECM components,
such as laminin and collagen I, were exhibited. Alkaline phosphatase
activity, osteocalcin secretion, related gene expression, and mineral
deposition were evaluated for BMSCs cultured on both ECM coatings.
PT-ECM was demonstrated to promote osteogenic differentiation much
more efficiently than that of ET-ECM. That is ascribed to the preservation
of native ECM milieu of PT-ECM. Such ECM acquirement and immobilization
method could establish surfaces being able to direct stem cell responses
on various materials. That shows promising potential in bone tissue
engineering and other related biomedical applications
Ternary Transition Metal Sulfides Embedded in Graphene Nanosheets as Both the Anode and Cathode for High-Performance Asymmetric Supercapacitors
Owing
to their low electronegativity, excellent electrical conductivity,
high specific capacitance, and rich electrochemical redox sites, various
transition metal sulfides have attracted significant attention as
promising pseudocapacitive electrode materials for supercapacitors.
However, their relatively poor electrical conductivity and large volume
changes seriously hinder their commercial applications. Herein, ternary
Co<sub>0.33</sub>Fe<sub>0.67</sub>S<sub>2</sub> nanoparticles are
in situ embedded between graphene nanosheets through a facile one-step
hydrothermal approach to form a sandwich-like composite. Because of
its unique and robust structure, the graphene nanosheet/Co<sub>0.33</sub>Fe<sub>0.67</sub>S<sub>2</sub> composite (GCFS-0.33) exhibits a high
specific capacitance (310.2 C g<sup>ā1</sup> at 2 mV s<sup>ā1</sup>) and superb rate capability (61.8% at 200 mV s<sup>ā1</sup>) in 3 M KOH aqueous electrolyte. Using transition
metal sulfides simultaneously as both positive and negative electrodes,
for the first time, an aqueous asymmetric supercapacitor (ASC) was
fabricated with the GCFS-0.33 composite as the negative electrode
and sulfidized graphene/CoNiAl-layered double hydroxides as the positive
electrode with well-separated potential windows. Our fabricated ASC
delivered an excellent energy density of 66.8 Wh kg<sup>ā1</sup> at a power density of 300.5 W kg<sup>ā1</sup> and still retained
13.1 Wh kg<sup>ā1</sup> even at a high power density of 29.4
kW kg<sup>ā1</sup>, which is highly comparable with that of
previously reported transition-metal-sulfide-based ASC devices. Moreover,
the as-fabricated ASC cell displays impressive long-term cycling stability
with a capacitance retention of 102.2% relative to the initial capacitance
after 10āÆ000 cycles. This versatile synthetic strategy can
be readily extended to synthesize other transition-metal-sulfide-based
composites with excellent electrochemical performances
Enhanced Osteointegration of Hierarchical Structured 3D-Printed Titanium Implants
Three-dimensional
(3D) printing technology has been widely used
to fabricate of various titanium and its alloy implants. However,
engineering the 3D printing nanoscaled feature to realize a hierarchical
micronano structured surface topography still remains a challenge.
On one hand, enhanced bioactivity is always expected on micronano-hybrid
biomimetic topography; on the other hand, a typical functional protein
in extracellular matrix (ECM) is nanoscaled; therefore, nanoscaled
features might affect its binding to specific receptor and subsequent
cell response. Here, we engineered a novel hierarchical structure
with microparticles and rutile TiO<sub>2</sub> nanorods topography
that fabricated by 3D printing of pure titanium followed by a hydrothermal
process. Although there was no difference on the microscaled feature
before/after nanonization, cellular behaviors including adhesion,
proliferation, and osteogenic differentiation of mesenchymal stem
cells (MSCs) were significantly upregulated on the hierarchical micronano
structured topography. Moreover, we demonstrated that the distinct
conformation of the initially fibronectin proteins adsorbed on nanorods
was more beneficial to cellular adhesion. <i>In vivo</i> test in a rabbit femur model also demonstrated the favorable for
new bone formation on the novel hierarchical micronano structured
implantābone interface. These results therefore suggest that
the hierarchical micronano structured topography might be a promising
surface feature for the new generation of bone implants
Light-Induced Cell Alignment and Harvest for Anisotropic Cell Sheet Technology
Well-organized
orientation of cells and anisotropic extracellular matrix (ECM) are
crucial in engineering biomimetic tissues, such as muscles, arteries,
and nervous system, and so on. This strategy, however, is only beginning
to be explored. Here, we demonstrated a light-induced cell alignment
and harvest for anisotropic cell sheets (ACS) technology using light-responsive
TiO<sub>2</sub> nanodots film (TNF) and photo-cross-linkable gelatin
methacrylate (GelMA). Cell initial behaviors on TNF might be controlled
by micropatterns of light-induced distinct surface hydroxyl features,
owing to a sensing mechanism of myosin II-driven retraction of lamellipodia.
Further light treatment allowed ACS detachment from TNF surface while
simultaneously solidified the GelMA, realizing the automatic transference
of ACS. Moreover, two detached ACS were successfully stacked into
a 3D bilayer construct with controllable orientation of individual
layer and maintained cell alignment for more than 7 days. Interestingly,
the anisotropic HFF-1 cell sheets could further induce the HUVECs
to form anisotropic capillary-like networks via upregulating VEGFA
and ANGPT1 and producing anisotropic ECM. This developed integrated-functional
ACS technology therefore provides a novel route to produce complex
tissue constructs with well-defined orientations and may have a profound
impact on regenerative medicine
Harnessing Cell Dynamic Responses on Magnetoelectric Nanocomposite Films to Promote Osteogenic Differentiation
The
binding of cell integrins to proteins adsorbed on the material
surface is a highly dynamic process critical for guiding cellular
responses. However, temporal dynamic regulation of adsorbed proteins
to meet the spatial conformation requirement of integrins for a certain
cellular response remains a great challenge. Here, an active CoFe<sub>2</sub>O<sub>4</sub>/polyĀ(vinylidene fluoride-trifluoroethylene)
nanocomposite film, which was demonstrated to be an obvious surface
potential variation (Ī<i>V</i> ā 93 mV) in
response to the applied magnetic field intensity (0ā3000 Oe),
was designed to harness the dynamic binding of integrin-adsorbed proteins
by in situ controlling of the conformation of adsorbed proteins. Experimental
investigation and molecular dynamics simulation confirmed the surface
potential-induced conformational change in the adsorbed proteins.
Cells cultured on nanocomposite films indicated that cellular responses
in different time periods (adhesion, proliferation, and differentiation)
required distinct magnetic field intensity, and synthetically programming
the preferred magnetic field intensity of each time period could further
enhance the osteogenic differentiation through the FAK/ERK signaling
pathway. This work therefore provides a distinct concept that dynamically
controllable modulation of the material surface property fitting the
binding requirement of different cell time periods would be more conducive
to achieving the desired osteogenic differentiation
Controlled Release of Naringin in Metal-Organic Framework-Loaded Mineralized Collagen Coating to Simultaneously Enhance Osseointegration and Antibacterial Activity
Two
important goals in orthopedic implant research are to promote osseointegration
and prevent infection. However, much previous effort has been focused
on the design of coatings to either enhance osseointegration while
ignoring antibacterial activity or vice versa, to prevent infection
while ignoring bone integration. Here, we designed a multifunctional
mineralized collagen coating on titanium with the aid of metal-organic
framework (MOF) nanocrystals to control the release of naringin, a
Chinese herbal medicine that could promote osseointegration and prevent
bacterial infection. The attachment, proliferation, osteogenic differentiation,
and mineralization of mesenchymal stem cells on the coating were significantly
enhanced. Meanwhile, the antibacterial abilities against Staphylococcus aureus were also promoted. Furthermore,
release kinetics analysis indicated that the synergistic effect of
a primary burst release stage and secondary slow release stage played
a critical role in the performance and could be controlled by the
relative concentrations of MOF and naringin. This work thus provides
a novel strategy to engineer multifunctional orthopedic coatings that
can enhance osseointegration and simultaneously inhibit microbial
cell growth
Surface Atomic Structure Directs the Fate of Human Mesenchymal Stem Cells
Stem
cells in contact with materials are able to sense their surface features,
integrate extracellular matrix (ECM) protein cues through a signal
transduction pathway, and ultimately direct cell fate decisions. However,
discovering the interdisciplinary mechanisms of how stem cells respond
to inherent material surface features still remains a challenge due
to the complex, multicomponent signaling milieu present in the ECM
environment. Here, we demonstrate that the fate of human mesenchymal
stem cells (hMSCs) can be regulated by the inherent physical cue of
the material surface down to atomic-scale features. hMSCs on a TiO-terminated
SrTiO<sub>3</sub> {110} substrate tend to differentiate into specific
lineage cells (osteoblast, chondrocyte, adipocyte), whereas on a TiO<sub>2</sub>-terminated SrTiO<sub>3</sub> {100} substrate they are prone
to maintain pluripotency. The experimental observations and molecular
dynamics simulations indicate that the distinct conformations of the
initially adsorbed serum albumin and fibronectin proteins activate
the integrināfocal adhesion cytoskeleton actin transduction
pathway and, subsequently, direct the gene and protein expressions
of hMSCs. Moreover, we demonstrate that the initial protein adsorption
behaviors are dependent on the distinct hydroxyl groups originating
from different surface atomic structures as well as the work functions.
This work, therefore, provides new insights into the fundamental understanding
of cellāmaterial interactions and will have a profound impact
on further designing materials to direct the stem cell fate