Silver nanoparticles (AgNPs) have been one of the most attractive nanomaterials in biomedicine due to their unique physicochemical properties. In this paper, we review the state-of-the-art advances ...of AgNPs in the synthesis methods, medical applications and biosafety of AgNPs. The synthesis methods of AgNPs include physical, chemical and biological routes. AgNPs are mainly used for antimicrobial and anticancer therapy, and also applied in the promotion of wound repair and bone healing, or as the vaccine adjuvant, anti-diabetic agent and biosensors. This review also summarizes the biological action mechanisms of AgNPs, which mainly involve the release of silver ions (Ag+), generation of reactive oxygen species (ROS), destruction of membrane structure. Despite these therapeutic benefits, their biological safety problems such as potential toxicity on cells, tissue, and organs should be paid enough attention. Besides, we briefly introduce a new type of Ag particles smaller than AgNPs, silver Ångstrom (Å, 1 Å = 0.1 nm) particles (AgÅPs), which exhibit better biological activity and lower toxicity compared with AgNPs. Finally, we conclude the current challenges and point out the future development direction of AgNPs.
Very recently, the LHCb collaboration has observed in the final state
Λ
c
+
K
-
π
+
π
+
a resonant structure that is identified as the doubly charmed baryon
Ξ
cc
+
+
. Inspired by this observation, ...we investigate the weak decays of doubly heavy baryons
Ξ
cc
+
+
,
Ξ
cc
+
,
Ω
cc
+
,
Ξ
bc
(
′
)
+
,
Ξ
bc
(
′
)
0
,
Ω
bc
(
′
)
0
,
Ξ
bb
0
,
Ξ
bb
-
and
Ω
bb
-
and focus on the decays into spin 1 / 2 baryons in this paper. At the quark level these decay processes are induced by the
c
→
d
/
s
or
b
→
u
/
c
transitions, and the two spectator quarks can be viewed as a scalar or axial vector diquark. We first derive the hadronic form factors for these transitions in the light-front approach and then apply them to predict the partial widths for the semileptonic and nonleptonic decays of doubly heavy baryons. We find that the number of decay channels is sizable and can be examined in future measurements at experimental facilities like LHC, Belle II and CEPC.
In elderly people particularly in postmenopausal women, inadequate bone formation by osteoblasts originating from bone marrow mesenchymal stem cells (BMSCs) for compensation of bone resorption by ...osteoclasts is a major reason for osteoporosis. Enhancing osteoblastic differentiation of BMSCs is a feasible therapeutic strategy for osteoporosis. Here, bone marrow stromal cell (ST)-derived exosomes (STExos) are found to remarkably enhance osteoblastic differentiation of BMSCs
in vitro
. However, intravenous injection of STExos is inefficient in ameliorating osteoporotic phenotypes in an ovariectomy (OVX)-induced postmenopausal osteoporosis mouse model, which may be because STExos are predominantly accumulated in the liver and lungs, but not in bone. Hereby, the STExo surface is conjugated with a BMSC-specific aptamer, which delivers STExos into BMSCs within bone marrow. Intravenous injection of the STExo-Aptamer complex enhances bone mass in OVX mice and accelerates bone healing in a femur fracture mouse model. These results demonstrate the efficiency of BMSC-specific aptamer-functionalized STExos in targeting bone to promote bone regeneration, providing a novel promising approach for the treatment of osteoporosis and fracture.
A novel strategy to deliver therapeutic exosomes to bone is developed for the first time by conjugating a specific BMSC-targeting aptamer to the exosomal surface.
We calculate the weak decay form factors of doubly-heavy baryons using three-point QCD sum rules. The Cutkosky rules are used to derive the double dispersion relations. We include perturbative ...contributions and condensation contributions up to dimension five, and point out that the perturbative contributions and condensates with lowest dimensions dominate. An estimate of a part of the gluon–gluon condensates show that it plays a less important role. With these form factors at hand, we present a phenomenological study of semileptonic decays. The future experimental facilities can test these predictions, and deepen our understanding of the dynamics in the decays of doubly-heavy baryons.
Super‐hydrophilic cellulose nanocrystals (CNCs) hold great potential in fabricating antifouling surfaces based on their high‐water binding affinity. However, integrating CNCs as a robust surface ...coating on substrate still remains a challenge due to its limited surface adhesion property. Herein, inspired by marine bio‐adhesive strategy, a facile yet universal surface coating method is developed for tightly anchoring CNCs on various substrates with an intermediate adhesive layer composed of tannic acid (TA)/polyethylenimine (PEI)/vanadium(V). Introducing V3+ ions in the assembly process significantly reduces the roughness of the TA/PEI/V bio‐glue layer via coordination chemistry, thus achieving a CNCs coating with a highly‐dense structure and outstandingly low root‐mean‐square roughness (≈2 nm). The super‐hydrophilic CNCs coating exhibits universal and outstanding antifouling properties in inhibiting oil adhesion, protein adsorption or cell attachment, and maintaining its structural integrity and wettability over 100 friction cycles. Additionally, the CNCs‐coated polyvinylidene fluoride (PVDF) membrane shows an ultra‐high water flux over 6000 L m–2 h–1 bar–1 and achieves nearly 100% permeating flux recovery ratio for separation of toluene‐in‐water emulsion containing various foulants. This study demonstrates a universal coating method to settle the long‐standing challenge of robust integration of rigid materials to various substrates for broad engineering and environmental applications.
A universal and scalable cellulose nanocrystals (CNCs) coating strategy is proposed and developed via robustly grafting CNCs onto various substrates by constructing an intermedia adhesive layer. The highly dense CNCs coating exhibits outstanding antifouling and anti‐wear performance for water purification. This study provides a useful method for addressing a long‐standing challenge of the integration of rigid materials as robust surface coatings.
Adipocyte differentiation of bone marrow mesenchymal stem/stromal cells (BMSCs) instead of osteoblast formation contributes to age- and menopause-related marrow adiposity and osteoporosis. Vascular ...calcification often occurs with osteoporosis, a contradictory association called "calcification paradox". Here we show that extracellular vesicles derived from aged bone matrix (AB-EVs) during bone resorption favor BMSC adipogenesis rather than osteogenesis and augment calcification of vascular smooth muscle cells. Intravenous or intramedullary injection of AB-EVs promotes bone-fat imbalance and exacerbates Vitamin D3 (VD3)-induced vascular calcification in young or old mice. Alendronate (ALE), a bone resorption inhibitor, down-regulates AB-EVs release and attenuates aging- and ovariectomy-induced bone-fat imbalance. In the VD3-treated aged mice, ALE suppresses the ovariectomy-induced aggravation of vascular calcification. MiR-483-5p and miR-2861 are enriched in AB-EVs and essential for the AB-EVs-induced bone-fat imbalance and exacerbation of vascular calcification. Our study uncovers the role of AB-EVs as a messenger for calcification paradox by transferring miR-483-5p and miR-2861.
The pursuit of single-molecule magnets (SMMs) with better performance urges new molecular design that can endow SMMs larger magnetic anisotropy. Here we report that two-coordinate cobalt imido ...complexes featuring highly covalent CoN cores exhibit slow relaxation of magnetization under zero direct-current field with a high effective relaxation barrier up to 413 cm–1, a new record for transition metal based SMMs. Two theoretical models were carried out to investigate the anisotropy of these complexes: single-ion model and Co–N coupling model. The former indicates that the pseudo linear ligand field helps to preserve the first-order orbital momentum, while the latter suggests that the strong ferromagnetic interaction between Co and N makes the CoN+ fragment a pseudo single paramagnetic ion, and that the excellent performance of these cobalt imido SMMs is attributed to the inherent large magnetic anisotropy of the CoN+ core with |M J = ± 7/2⟩ ground Kramers doublet.
Combining Ising‐type magnetic anisotropy with collinear magnetic interactions in single‐molecule magnets (SMMs) is a significant synthetic challenge. Herein we report a Dy15‐MCCu‐5 (1‐Dy) SMM, where ...a DyIII ion is held in a central pseudo‐D5h pocket of a rigid and planar Cu5 metallacrown (MC). Linking two Dy15‐MCCu‐5 units with a single hydroxide bridge yields the double‐decker {Dy15‐MCCu‐5}2 (2‐Dy) SMM where the anisotropy axes of the two DyIII ions are nearly collinear, resulting in magnetic relaxation times for 2‐Dy that are approximately 200 000 times slower at 2 K than for 1‐Dy in zero external field. Whereas 1‐Dy and the YIII‐diluted Dy@2‐Y analogue do not show remanence in magnetic hysteresis experiments, the hysteresis data for 2‐Dy remain open up to 6 K without a sudden drop at zero field. In conjunction with theoretical calculations, these results demonstrate that the axial ferromagnetic Dy–Dy coupling suppresses fast quantum tunneling of magnetization (QTM). The relaxation profiles of both complexes curiously exhibit three distinct exponential regimes, and hold the largest effective energy barriers for any reported d–f SMMs up to 625 cm−1.
The magnetic hysteresis of a metallacrown magnet opens after introducing axial ferromagnetic by linking two mono‐decker Dy15‐MCCu‐5 units with a single hydroxide bridge to give the double‐decker {Dy15‐MCCu‐5}2 single‐molecule magnet in which the anisotropy axes of the two DyIII ions are nearly collinear and the magnetic relaxation times are approximately 200 000 times slower than for the mono‐decker unit.
Chronoamperometry was used to study the dynamics of Pt nanoparticle (NP) collision with an inert ultramicroelectrode via electrocatalytic amplification (ECA) in the hydrogen evolution reaction. ECA ...and dynamic light scattering (DLS) results reveal that the NP colloid remains stable only at low proton concentrations (1.0 mm) under a helium (He) atmosphere, ensuring that the collision events occur at genuinely single NP level. Amperometry of single NP collisions under a He atmosphere shows that each discrete current profile of the collision event evolves from spike to staircase at more negative potentials, while a staircase response is observed at all of the applied potentials under hydrogen‐containing atmospheres. The particle size distribution estimated from the diffusion‐controlled current in He agrees well with electron microscopy and DLS observations. These results shed light on the interfacial dynamics of the single nanoparticle collision electrochemistry.
Evolution or stability? Under a helium atmosphere, the electrochemical catalytic current profile of the hydrogen evolution reaction on a single platinum nanoparticle (Pt NP) evolves from a spike to a staircase at more negative potentials on the underlying inert ultramicroelectrode (UME). Under a hydrogen atmosphere, the current profile stabilizes as a staircase at all polarized potentials but at least 5 times lower than that in helium.
In this study, to overcome the inherent hydrophobicity and improve the comprehensive performance of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes, hydrophilic TiO2 particles were ...utilized to modify PVDF UF membranes. To obtain the strong binding force and homogenous TiO2 distribution on PVDF UF membranes, polydopamine (pDA) as the “bio-glue” was architecturally built between TiO2 and PVDF membranes, and the modification process was facilely designed via self-polymerization of dopamine and subsequent hydrolysis of ammonium fluotitanate. Water contact angle tests proved the significant improvement in the hydrophilicity of PVDF membranes after modification. The morphologies of various membranes before and after modification were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and the chemical reactions during different modification stages were evaluated by X-ray photoelectron spectroscopy (XPS) tests. It was found that the pDA layer via self-polymerization of dopamine on PVDF membranes could assist TiO2 to tightly and homogeneously bind onto PVDF surface for improving the stability and anti-fouling property of membranes because of the coordination bond (CO···Ti) formed between TiO2 and pDA, and the pore sizes of PVDF membranes obviously decreased after modifications. The possible mechanisms during modifications were discussed. The comprehensive properties of PVDF membranes after such facile modifications had been greatly enhanced according to the results of water flux, bovine serum albumin (BSA) rejection, anti-fouling performance, and TiO2 binding performance characterizations. Both the water flux and BSA rejection could be simultaneously improved at the optimized hydrolysis time. Furthermore, the static and dynamic BSA adsorption tests were carried out. Interestingly, the amounts of BSA adsorption onto modified membranes demonstrated the opposite trends for the static and dynamic BSA adsorption tests. The possible reason was clarified based on the competition between the improved hydrophilicity and the adsorption ability of TiO2. Therefore, TiO2 modified PVDF UF membranes developed by this novel strategy have attractive potential for water environmental remediation.
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•A facile strategy was utilized to modify PVDF UF membranes.•PVDF membranes were homogenously and tightly modified by TiO2 with the aid of pDA.•The comprehensive properties of PVDF membrane had been greatly enhanced.•Modified PVDF membranes had great potential for water environmental remediation.
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