Acidity-activated aggregation and accumulation of self-complementary zwitterionic peptide-decorated gold nanoparticles for photothermal biofilm eradication.

Drug-resistant biofilm infection is an extremely serious clinical problem, that easily leads to failure of antibiotic treatment. Although gold nanoparticles (AuNPs) as photothermal agents have been widely used in biofilm eradication, there are still challenges to be addressed, such as insignificantly redshifted absorption and slow assembly process of aggregated AuNPs. Herein, we developed an acidity-activated dispersion-to-aggregation transition to enhance the accumulation of self-complementary zwitterionic peptide-decorated AuNPs for photothermal eradication of drug-resistant biofilm infections. AuNPs were decorated with self-complementary zwitterionic peptides (ZP1 and ZP2) coupled with pH-sensitive anhydride (DMA) and pH-insensitive anhydride (SA), respectively. ZP2-decorated AuNPs with DMA modification (AuNP@ZP2(DMA)) exhibited prolonged blood circulation and enhanced accumulation in acidic biofilm microenvironment. Moreover, the electrostatic attraction between self-complementary ligands drove AuNPs to form closely packed aggregates with strong near-infrared absorption, leading to in vivo photoacoustic imaging ability and photothermal effect against drug-resistant bacteria and fungus, as well as microbial biofilms. AuNP@ZP2(DMA) with longer charge domains and a polyethylene glycol oligomer spacer showed greater photothermal antimicrobial and biofilm resistance in vitro and in vivo. This study develops an innovative acidity-activated AuNP photothermal agent, which provides an effective approach for treatment of biofilm infections.

Adverse effects of pristine and aged polystyrene microplastics in mice and their Nrf2-mediated defense mechanisms with tissue specificity.

Health hazards associated with microplastics (MPs) remain largely unknown, and the effects of aged MPs, one of their persistent forms, are poorly characterized. Male ICR mice were intratracheally instilled with 0.01 and 1 mg/day pristine and ultraviolet (UV)-aged polystyrene microplastics (PS and APS) with an average diameter of 4 - 5 µm daily for 1 week. UV irradiation caused the PS to have a rough surface, become fragmented, and increase their carbonyl groups. Both PS and APS caused structural damage to the mouse gut, liver, spleen, and testis. Inflammatory infiltration in liver, swollen and congested gut, and loose spleen globules, as well as the loose interstitium of the seminiferous tubules in testis were found in 1 mg/day APS group. Increases in serum alanine aminotransferase and immunoglobulin A levels in 1 mg/day APS group (p < 0.05) demonstrated that APS exposure could induce greater liver and spleen functional damage than PS. Meanwhile, triglyceride and total cholesterol levels in liver were enhanced in 1 mg/day APS group (p < 0.05). Superoxide dismutase and glutathione contents in 0.01 and 1 mg/day APS groups significantly decreased (p < 0.05), which suggesting that PS and APS could interfere with the antioxidant capacity in mice. Nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) levels in the PS and APS groups showed significant increases in the liver and testis (p < 0.05), and a significant decrease in the spleen (p < 0.05), which were analyzed to get a first survey for Nrf2/HO-1-mediated tissue-specific defense mechanisms. In conclusion, acute exposure to PS and APS induced potential metabolic disorders, and APS could produce more serious immune damage and reproductive toxicity. These findings provide new insights in health risk assessment of aged MPs.

Advances in Artificial Layers for Stable Lithium Metal Anodes.

Lithium (Li) metal is considered as the most promising anode material for rechargeable high-energy batteries. Nevertheless, the practical implement of Li anodes is significantly hindered by the growth of Li dendrites, which can cause severe safety issues. To inhibit the formation of Li dendrites, coating an artificial layer on the Li metal anode has been shown to be a facile and effective approach. This review mainly focuses on recent advances in artificial layers for stable Li metal anodes. It summarizes the progress in this area and discusses the different types of artificial layers according to their mechanisms for Li dendrite inhibition, including regulation of uniform deposition of Li metal and suppression of Li dendrite growth. By doing this, it is hoped that this contribution will provide instructional guidance for the future design of new artificial layers.

An Interfacial Layer Based on Polymers of Intrinsic Microporosity to Suppress Dendrite Growth on Li Metal Anodes.

The performance and safety of lithium (Li) metal batteries can be compromised owing to the formation of Li dendrites. Here, the use of a polymer of intrinsic microporosity (PIM) is reported as a feasible and robust interfacial layer that inhibits dendrite growth. The PIM demonstrates excellent film-forming ability, electrochemical stability, strong adhesion to a copper metal electrode, and outstanding mechanical flexibility so that it relieves the stress of structural changes produced by reversible lithiation. Importantly, the porous structure of the PIM, which guides Li flux to obtain uniform deposition, and its strong mechanical strength combine to suppress dendrite growth. Hence, the electrochemical performance of the anode is significantly enhanced, promising excellent performance and extended cycle lifetime for Li metal batteries.

Grape-Like Fe3O4 Agglomerates Grown on Graphene Nanosheets for Ultrafast and Stable Lithium Storage.

An in situ simple and effective synthesis method is effectively exploited to construct MOF-derived grape-like architecture anchoring on nitrogen-doped graphene, in which ultrafine Fe3O4 nanoparticles are uniformly dispersed (Fe3O4@C/NG). In this hybrid hierarchical structure, new synergistic features are accessed. The graphene oxide plane with functional groups is expected to alleviate the aggregation problem in the MOFs' growth. Moreover, the morphology and size of iron-based MOFs and carbon content are conveniently controlled by controlling the solution concentration of precursor. Through making use of in situ carbonization of the organic ligands in MOFs, Fe3O4 subunits are effectively protected by 3D interconnected conductive carbon at microscale. Consequently, when applied as anode materials, even as high as 10 A g(-1) after 1000 cycles, Fe3O4@C/NG still maintains as high as 458 mA h g(-1).

Organic solvent-assisted free-standing Li2MnO3·LiNi(1/3)Co(1/3)Mn(1/3)O2 on 3D graphene as a high energy density cathode.

A novel organic solvent-assisted freeze-drying pathway, which can effectively protect and uniformly distribute active particles, is developed to fabricate a free-standing Li2MnO3·LiNi1/3Co1/3Mn1/3O2 (LR)/rGO electrode on a large scale. Thus, very high energy density and power density are realized for LR materials with robust long-term cyclability.

Reprocessable squeezing electrode fabrication of olive-like Fe/Co/O nanoparticle@three dimensional nitrogen-doped reduced graphene oxides for high performance lithium batteries.

A one step in situ synthesis approach is developed to construct 3D nitrogen-doped reduced graphene oxides, in which olive-like multi-component metal oxides are homogeneously dispersed. The novel hybrid nanoarchitecture shows some particular properties derived from synergistic effects. The size of Fe/Co/O oxides is reduced and better controlled compared to that of individual oxides due to mutual dispersant interactions. Furthermore, the positive synergistic interaction between heterogeneous oxides and graphene nanosheets has effective control on the particle size and dispersion of nanoparticles. Taking advantage of the flexibility and the cohesiveness of graphene nanosheets, the obtained composite can be directly processed into a binder-free electrode through a unique time-saving "squeezing" process. The obtained electrode possesses a reprocessable feature, which provides possibilities for convenient storage and quick fabrication at any time and presents attractive electrochemical performance of robust long-term capability retention (562 mA h g(-1) after 300 cycles at 10 A g(-1)) and superior rate performances (1162 mA h g(-1) at 0.5 A g(-1), 737 mA h g(-1) at 5 A g(-1), and 585 mA h g(-1) at 10 A g(-1)).

Pump-free and low-cost negative pressure sampling device for rapid sample loading in MCE.

A pump-free and low-cost negative pressure sampling device for injecting well-defined non-biased sample plugs into the separation channel of MCE was developed. It was composed of a pipet bulb, a 3-way electromagnetic valve and a single voltage supply at constant voltage. A sub-atmospheric pressure was created by hand-pressing air out of the pipet bulb and retained in it by switching the 3-way electromagnetic valve at cutoff position. During the sample loading stage, the sub-atmospheric pressure in the pipet bulb was applied via a 3-way electromagnetic valve to the headspace of the sealed sample waste reservoir (SW). A pinched sample plug was formed at the channel intersection in less than 0.5 s. Once the 3-way electromagnetic valve was switched to connect SW to ambient atmosphere to release the vacuum in SW, electrophoresis separation was consequently activated under the electric potentials applied. Experimental results demonstrated the pump-free negative pressure sampling device worked well in a wide vacuum degree ranged from -250 to -30 mbar with a satisfactory analytical precision. The sample consumption for each cycle was calculated to be 51-12 nL under the sampling pressure. Theoretical deduction indicates that the volume of the pipet bulb can be further reduced to 1 mL, which is critical for minimizing the sampling device for MCE.

Rapid and efficient isotachophoretic preconcentration in free solution coupled with gel electrophoresis separation on a microchip using a negative pressure sampling technique.

We present a novel isotachophoresis-gel electrophoresis (ITP-GE) microchip system designed for rapid and efficient isotachophoretic preconcentration coupled with gel electrophoresis separation by using a negative pressure sampling technique. The overall ITP-GE procedure involves only three steps: sample loading, ITP preconcentration and GE separation and was controlled by a simple and compact negative pressure sampling device, which is composed of a vacuum vessel, a three-way electromagnetic valve and a single high voltage power supply. During the sample loading stage, a negative pressure was applied via a three-way electromagnetic valve in headspace of the two sealed sample waste reservoirs (SWs). A sandwiched sample zone between a leading and a terminating electrolyte zone was formed in the channel intersection in less than 1s. Once the three-way electromagnetic valve was switched to connect SWs to ambient atmosphere to release vacuum in SWs, ITP preconcentration in free solution and GE separation in the 4% hydroxyethylcellulose (HEC) sieving material were consequently activated under the electric potentials applied. The performance of present approach was evaluated by using DNA fragments as model analytes. Compared to conventional cross microchip GE using electrokinetic pinched injection, an average signal enhancement of 185-fold was obtained with satisfactory resolution. The results demonstrated the ITP-GE approach possessing an exciting potential of high sensitivity and short sampling time with significant simplification in operation and instrumentation.

Rapid and variable-volume sample loading in sieving electrophoresis microchips using negative pressure combined with electrokinetic force.

A rapid and variable-volume sample loading scheme for chip-based sieving electrophoresis was developed by negative pressure combined with electrokinetic force. This was achieved by using a low-cost microvacuum pump and a single potential supply at a constant voltage. Both 12% linear polyacrylamide (LPA) with a high viscosity of 15000 cP and 2% hydroxyethylcellulose (HEC) with a low viscosity of 102 cP were chosen as the sieving materials to study the behavior and the versatility of the proposed method. To reduce the hydrodynamic resistance in the sampling channel, sieving material was only filled in the separation channel between the buffer waste reservoir (BW) to the edge of the crossed intersection. By applying a subambient pressure to the headspace of sample waste reservoir (SW), sample and buffer solution were drawn immediately from sample reservoir (S) and buffer reservoir (B) across the intersection to SW. At the same time, the charged sample in the sample flow was driven across the interface between the sample flow and the sieving matrix into the sieving material filled separation channel by the applied electric field. The injected sample plug length is in proportion with the loading time. Once the vacuum in SW reservoir was released to activate electrophoretic separation, flows from S and B to SW were immediately terminated by the back flow induced by the difference of the liquid levels in the reservoirs to prevent sample leakage during the separation stage. The sample consumption was about 1.7 x 10(2) nL at a loading time of 1 s for each cycle. Only 0.024 s was required to transport bias-free analyte to the injection point. It is easy to freely choose the sample plug volume in this method by simply changing the loading time and to inject high quality sample plug with non-distorted shape into the separation channel. The system has been proved to possess an exciting potential for improving throughput, repeatability, sensitivity and separation performance of chip-based sieving electrophoresis.