Layered nanocomposites by shear-flow-induced alignment of nanosheets.

Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness1-3. Such properties are attributed to the elaborate layered microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix4-6. Inspired by these biological structures, several assembly strategies-including layer-by-layer4,7,8, casting9,10, vacuum filtration11-13 and use of magnetic fields14,15-have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young's modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites.

S-glutathionylation proteome profiling reveals a crucial role of a thioredoxin-like protein in interspecies competition and cariogenecity of Streptococcus mutans.

S-glutathionylation is an important post-translational modification (PTM) process that targets protein cysteine thiols by the addition of glutathione (GSH). This modification can prevent proteolysis caused by the excessive oxidation of protein cysteine residues under oxidative or nitrosative stress conditions. Recent studies have suggested that protein S-glutathionylation plays an essential role in the control of cell-signaling pathways by affecting the protein function in bacteria and even humans. In this study, we investigated the effects of S-glutathionylation on physiological regulation within Streptococcus mutans, the primary etiological agent of human dental caries. To determine the S-glutathionylated proteins in bacteria, the Cys reactive isobaric reagent iodoacetyl Tandem Mass Tag (iodoTMT) was used to label the S-glutathionylated Cys site, and an anti-TMT antibody-conjugated resin was used to enrich the modified peptides. Proteome profiling identified a total of 357 glutathionylated cysteine residues on 239 proteins. Functional enrichment analysis indicated that these S-glutathionylated proteins were involved in diverse important biological processes, such as pyruvate metabolism and glycolysis. Furthermore, we studied a thioredoxin-like protein (Tlp) to explore the effect of S-glutathionylation on interspecies competition between oral streptococcal biofilms. Through site mutagenesis, it was proved that glutathionylation on Cys41 residue of Tlp is crucial to protect S. mutans from oxidative stress and compete with S. sanguinis and S. gordonii. An addition rat caries model showed that the loss of S-glutathionylation attenuated the cariogenicity of S. mutans. Taken together, our study provides an insight into the S-glutathionylation of bacterial proteins and the regulation of oxidative stress resistance and interspecies competition.

Stable and Highly Efficient Antibody-Nanoparticles Conjugation.

Functional ligands and polymers have frequently been used to yield target-specific bio-nanoconjugates. Herein, we provide a systematic insight into the effect of the chain length of poly(oligo (ethylene glycol) methyl ether acrylate) (POEGMEA) containing polyethylene glycol on the colloidal stability and antibody-conjugation efficiency of nanoparticles. We employed Reversible Addition-Fragmentation Chain Transfer (RAFT) to design diblock copolymers composed of 7 monoacryloxyethyl phosphate (MAEP) units and 6, 13, 35, or 55 OEGMEA units. We find that when the POEGMEA chain is short, the polymer cannot effectively stabilize the nanoparticles, and when the POEGMEA chain is long, the nanoparticles cannot be efficiently conjugated to antibody. In other words, the majority of the carboxylic groups in larger POEGMEA chains are inaccessible to further chemical modification. We demonstrate that the polymer containing 13 OEGMEA units can effectively bind up to 64% of the antibody molecules, while the binding efficiency drops to 50% and 0% for the polymer containing 35 and 55 OEGMEA units. Moreover, flow cytometry assay statistically shows that about 9% of the coupled antibody retained its activity to recognize B220 biomarkers on the B cells. This work suggests a library of stabile, specific, and bioactive lanthanide-doped nanoconjugates for flow cytometry and mass cytometry application.

Bispecific Antibody-Functionalized Upconversion Nanoprobe.

Upconversion nanoparticles (UCNPs) are new optical probes for biological applications. For specific biomolecular recognition to be realized for diagnosis and imaging, the key lies in developing a stable and easy-to-use bioconjugation method for antibody modification. Current methods are not yet satisfactory regarding conjugation time, stability, and binding efficiency. Here, we report a facile and high-yield approach based on a bispecific antibody (BsAb) free of chemical reaction steps. One end of the BsAb is designed to recognize methoxy polyethylene glycol-coated UCNPs, and the other end of the BsAb is designed to recognize the cancer antigen biomarker. Through simple vortexing, BsAb-UCNP nanoprobes form within 30 min and show higher (up to 54%) association to the target than that of the traditional UCNP nanoprobes in the ELISA-like assay. We further demonstrate its successful binding to the cancer cells with high efficiency and specificity for background-free fluorescence imaging under near-infrared excitation. This method suggests a general approach broadly suitable for functionalizing a range of nanoparticles to specifically target biomolecules.

Theory on Capillary Filling of Polymer Melts in Nanopores.

A unified theory for the imbibition dynamics of entangled polymer melting into nanopores is presented. Experiments demonstrate the validity of t1/2 dependence but contradict the predictions of the classical Lucas-Washburn equation because of the prefactor. A reversal in dynamics of capillary filling is reported with increasing polymer molecular weight. Polymer imbibition under nanometer confinement can be discussed by two mechanisms: one is the standard hydrodynamic flow, resulting in a parabolic flow profile. When the inner wall has a strong attraction to the polymer, a layer of immobile chains is created, resulting in an increase of the effective viscosity and to slower imbibition. The other is the reptation model proposed by Johner et al., leading to a plug flow profile and to the reduction in the effective viscosity (faster imbibition). The reversal in dynamics of polymer imbibition can be explained by the competition between these two mechanisms.

Nitrogen removal performance of bioretention cells under polyethylene (PE) microplastic stress.

The use of bioretention cells as a stormwater control measure allows stormwater runoff to be collected and filtered, effectively removing microplastics and other pollutants from stormwater. This study investigated the effect of polyethylene microplastics (PE-MPs) retention on the bioretention cell, in terms of denitrification performance and microbial community structure. Four PE-MP exposures were compared at different concentrations of 0, 250, 500 and 1000 mg/L under alternating dry and wet period conditions. Results showed that the removal efficiency reduced by 14.99%, 28.37% and 18.59% with PE-MP concentrations of 250, 500 and 1000 mg/L. The NO3--N removal efficiency increased by 36.19%, 20.19% and 35.39%. After 8 days of dry conditions, the NO3--N removal efficiencies of the bioretention cells were reduced by 36.66%, 46.86% and 31.11% compared to those after 2 days of dry conditions. Microbial sequencing results indicated that the accumulation of PE-MPs changed the microbial community structure within the bioretention cell filler material, promoting the growth of bacteria such as Actinobacteria, Bacteroidetes and Firmicutes. Furthermore, PE-MPs reduced the relative abundance of nitrifying bacteria (e.g. Nitrospira) within the bioretention cell and promoted denitrifying bacteria (e.g. Dechloromonas and Hydrogenophaga), along with numerous other genera such as Azotobacter and Nocardia.

Colorectal Tumor Microenvironment-Activated Bio-Decomposable and Metabolizable Cu2 O@CaCO3 Nanocomposites for Synergistic Oncotherapy.

Rational design of tumor microenvironment (TME)-activated nanocomposites provides an innovative strategy to construct responsive oncotherapy. In colorectal cancer (CRC), the specific physiological features are the overexpressed endogenous H2 S and slightly acidic microenvironment. Here, a core-shell Cu2 O@CaCO3 nanostructure for CRC "turn-on" therapy is reported. With CaCO3 responsive to pH decomposition and Cu2 O responsive to H2 S sulfuration, Cu2 O@CaCO3 can be triggered "on" into the therapeutic mode by the colorectal TME. When the CaCO3 shell decomposes and releases calcium in acidic colorectal TME, the loss of protection from the CaCO3 shell exposes the Cu2 O core to be sulfuretted by H2 S to form metabolizable Cu31 S16 nanocrystals that gain remarkably strong near-infrared absorption. After modifying hyaluronic acid, Cu2 O@CaCO3 can achieve synergistic CRC-targeted and TME-triggered photothermal/photodynamic/chemodynamic/calcium-overload-mediated therapy. Moreover, it is found that the generation of hyperthermia and oxidative stress from Cu2 O@CaCO3 nanocomposites can efficiently reprogram the macrophages from the M2 phenotype to the M1 phenotype and initiate a vaccine-like immune effect after primary tumor removal, which further induces an immune-favorable TME and intense immune responses for anti-CD47 antibody to simultaneously inhibit CRC distant metastasis and recurrence by immunotherapy.

Elastic property of membranes self-assembled from diblock and triblock copolymers.

The elastic property of membranes self-assembled from AB diblock and ABA triblock copolymers, as coarse-grained model of lipids and the bolalipids, are studied using the self-consistent field theory (SCFT). Specifically, solutions of the SCFT equations, corresponding to membranes in different geometries (planar, cylindrical, spherical, and pore) have been obtained for a model system composed of amphiphilic AB diblock copolymers and ABA triblock copolymers dissolved in A homopolymers. The free energy of the membranes with different geometries is then used to extract the bending modulus, Gaussian modulus, and line tension of the membranes. The results reveal that the bending modulus of the triblock membrane is greater than that of the diblock membrane. Furthermore, the Gaussian modulus and line tension of the triblock membrane indicate that the triblock membranes have higher pore formation energy than that of the diblock membranes. The equilibrium bridging and looping fractions of the triblock copolymers are also obtained. Implications of the theoretical results on the elastic properties of biologically equivalent lipid bilayers and the bolalipid membranes are discussed.

Protein corona composition of poly(ethylene glycol)- and poly(phosphoester)-coated nanoparticles correlates strongly with the amino acid composition of the protein surface.

Extensive molecular dynamics simulations reveal that the interactions between proteins and poly(ethylene glycol) (PEG) can be described in terms of the surface composition of the proteins. PEG molecules accumulate around non-polar residues while avoiding the polar ones. A solvent-accessible-surface-area model of protein adsorption accurately fits a large set of data on the composition of the protein corona of poly(ethylene glycol)- and poly(phosphoester)-coated nanoparticles recently obtained by label-free proteomic mass spectrometry.

Aqueous phase preparation of ultrasmall MoSe2 nanodots for efficient photothermal therapy of cancer cells.

Photothermal therapy (PTT) is a promising cancer treatment with both high effectiveness and fewer side effects. However, an ideal PTT agent not only needs strong absorption of near-infrared (NIR) light and high photothermal conversion efficiency, but also needs good biocompatibility, stability, and small size, which makes the design and preparation of a novel PTT agent a great challenge. In this work, we developed an ultrasonication-assisted liquid exfoliation method for the direct preparation of ultrasmall (2-3 nm) MoSe2 nanodots (NDs) in aqueous solution and demonstrated their superior properties as a PTT agent. The as-prepared MoSe2 NDs have strong absorption of NIR light and high photothermal conversion efficiency of about 46.5%. In vitro cellular experiments demonstrate that MoSe2 NDs have negligible cytotoxicity and can efficiently kill HeLa cells (human cervical cell line) under NIR laser (785 nm) irradiation.

[Preparation of 5-fluorouracil encapsulated in amphiphilic polysaccharide nano-micelles and its killing effect on hepatocarcinoma cell line HepG2].

BACKGROUND & OBJECTIVE: Biodegradable colloidal nano-micelles is a novel targeting drug delivery and controlled release system, which could prolong the biological half-life and lighten the toxicity of chemotherapeutant, meanwhile, present fine biocompatibility. This study was to prepare the biodegradable 5-fluorouracil (5-FU)/DEX-g-PLA nano-micelles, and investigate their killing effect on hepatocarcinoma cell line HepG2 in vitro and in vivo. METHODS: 5-FU/DEX-g-PLA nano-micelles were prepared by 'self-assembly'. Its morphology was observed by transmission electron microscopy. The encapsulating efficiency of 5-FU was determined by ultraviolet spectrophotometry. The in vivo releasing of 5-FU from nano-micelles was investigated by high-performance liquid chromatography (HPLC). The inhibitory effect of 5-FU/DEX-g-PLA on HepG2 cells in vitro was measured by MTT assay. RESULTS: 5-FU/DEX-g-PLA nano-micelles were round or elliptical; the diameter was about 50 nm. The encapsulating efficiency was about 9.3%. The concentration of 5-FU released from 5-FU/DEX-g-PLA nano-micelles was sustained for longer time than that of the naked drug. The in vitro inhibition rate of cell growth was similar in 5-FU/DEX-g-PLA group and naked 5-FU group (58.8% vs. 58.0%, P>0.05); the in vivo inhibition rate of tumor growth was significantly higher in 5-FU/DEX-g-PLA group than in naked 5-FU group (73.1% vs. 57.5%, P<0.05). CONCLUSION: 5-FU/DEX-g-PLA nano-micelles can effectively inhibit the growth of HepG2 cells.