A wearable AuNP enhanced metal-organic gel (Au@MOG) sensor for sweat glucose detection with ultrahigh sensitivity.

The demand for sensitive and non-invasive sensors for monitoring glucose levels in sweat has grown considerably in recent years. This study presents the development of a wearable sensor for sweat glucose detection with ultrahigh sensitivity. The sensor was fabricated by embedding Au nanoparticles (AuNPs) and metal-organic gels (MOGs) on nickel foam (NF). A non-enzymatic electrocatalytic glucose sensor has been developed to combine the three-dimensional network of MOGs with more active sites favourable for glucose diffusion and the transfer of electrons from glucose to the electrode. These results show that the sensor has an ultrahigh sensitivity of 13.94 mA mM-1 cm-2, a linear detection range between 2 and 600 µM, and a lower detection limit as low as 1 µM (signal/noise = 3) with comparable accuracy and reliability under non-alkaline conditions to those of high-pressure ion chromatography (HPIC). Furthermore, a wearable sweat glucose sensor has been constructed by sputtering an Au conductive layer on a flexible polydimethylsiloxane (PDMS) substrate and coating it with Au@MOGs. Our work demonstrates that the combination of Au NPs and MOGs can enhance the sensitivity and activity of these materials, making them useful for electrocatalytic glucose monitoring with ultrahigh sensitivity.

Tunable Gas-Gas Reactions through Nanobubble Pathway.

Combustible gas-gas reactions usually do not occur spontaneously upon mixing without ignition or other triggers to lower the activation energy barrier. Nanobubbles, however, could provide such a possibility in solution under ambient conditions due to high inner pressure and catalytic radicals within their boundary layers. Herein, a tunable gas-gas reaction strategy via bulk nanobubble pathway is developed by tuning the interface charge of one type of bulk nanobubble and promoting its fusion and reaction with another, where the reaction-accompanied size and number concentration change of the bulk nanobubbles and the corresponding thermal effect clearly confirm the occurrence of the nanobubble-based H2 /O2 combustion. In addition, abundant radicals can be detected during the reaction, which is considered to be critical to ignite the gas reaction during the fusion of nanobubbles in water at room temperature. Therefore, the nanobubble-based gas-gas reactions provide a safe and efficient pathway to produce energy and synthesize new matter inaccessible under mild or ambient conditions.

Au@bovine serum albumin nanoparticle-based acid-resistant nanozyme quartz crystal microbalance sensing of urine glucose.

A robust, efficient and sensitive quartz crystal microbalance (QCM) for glucose detection has been constructed using Au@bovine serum albumin (Au@BSA) nanoparticles as an active layer. The nanoparticles serve as tandem nanozymes and their stability over natural enzymes enable the sensor to show a wider linear dynamic range between 0.05 and 15 mM, a higher acid-resistance (pH 2.0-8.0) and heat-resistance (35-60 °C) than conventional glucose oxidase (GOx)-based sensors. The sensor has been further applied to measure glucose content in artificial urine directly without dilution, where the recovery of 99.6-105.2% and the relative standard deviations (RSDs) below 0.88% confirm a good reproducibility for the measurement results. In addition, the developed Au@BSA QCM sensor can retain 95% of its initial activity after 40 days of storage. Overall, the Au@BSA sensor shows better comprehensive performance than the commercial sensor strips for urine glucose analysis and provides a promising approach in a more precise and robust manner.

High-efficiency mechanically assisted alkaline extraction of nanoparticles from biological tissues for spICP-MS analysis.

The widespread use and increased exposure of nanoparticles call for technology to quantify their concentration and size distribution in biological matrices. As ex situ evaluation, facile extraction with high fidelity and efficiency is critical. In this work, single particle inductively coupled plasma mass spectrometry (spICP-MS) was used for nanoparticle number and distribution analysis, where a facile and highly efficient mechanically assisted alkaline digestion has been developed to extract nanoparticles at low alkali concentration. The optimization was performed using chicken tissues in vitro mixed with 30 nm gold nanoparticles, mixture of 30 nm and 60 nm gold nanoparticles, and 45 nm silver nanoparticles, respectively, which is, then, mechanically ground to form tissue homogenate and 2% TMAH is added. The nanoparticles are extracted with a recovery of more than 94% for all the spiked nanoparticle tissue samples. The extraction method has also been attempted to be applied to extract single-sized gold nanoparticles from various organs of mice mixed in vivo with the nanoparticles through intravenous injection, and led to consistent results with acid digestion. Mice injected intravenously with double-sized gold nanoparticle mixture were also studied, further showing that gold nanoparticles of 30 nm and 60 nm have no significant difference in their biodistribution in the same organ. To the best of our knowledge, this is the first attempt for multiple nanoparticles being extracted simultaneously and measured quantitatively from various organs, such as the heart, liver, spleen, lungs, and kidneys. We believe this method is beneficial to the safety assessment and toxicokinetics studies for nanoparticles in tissues.

Nanobubble boundary layer thickness quantified by solvent relaxation NMR.

HYPOTHESIS: The boundary layer holds the key to solve the puzzle of the unusual stability of the nanobubbles in solution. The quantitative determination on its mechanical and structural properties has not been achieved due to its diffusive and dynamic nature, lack of distinctive interfaces, and difficult differentiation from bulk background. Therefore, it is necessary to investigate this boundary using more sensitive interface analysis technologies to effectively differentiate the water molecules at the interface from those in the bulk. EXPERIMENTS: An in-situ and non-deconstructive method, solvent relaxation nuclear magnetic resonance, was used to investigate the boundary layer on bulk nanobubbles, where the relaxation rate of the water in the layer and its thickness were measured by solvent relaxation NMR and the ratio between the water molecules at the bubble interfaces and those in the bulk and the corresponding boundary layer thickness were determined. FINDINGS: The spin-spin relaxation time for the water in the layer (∼101ms) is found to be two orders of magnitude lower than that of the free water (∼103ms). As the first attempt, the determined boundary layer thickness is around 35-45 nm and 17.0 %-8.7 % of the effective gaseous size of the nanobubbles, which increases with the decrease of the bubble diameter. As a result, a quantitative measurement model for bubble boundary layer has been established in order to better understand the interfacial properties and stabilization mechanism for bulk nanobubbles.

Metal organic complexes as an artificial solid-electrolyte interface with Zn-ion transfer promotion for long-life zinc metal batteries.

Metal organic complexes as an artificial solid-electrolyte interface (MOC-SEI) have been generated via in situ coordinative polymerization between Zn2+ and organic ligand molecules. Compared to conventional anodes, the MOC-SEI coated anode significantly prolongs the lifespan from 100 h to 1450 h for the Zn||Zn symmetrical cells and increases the reversible capacity up to 160 mA h g-1 after 1100 cycles for the Zn||V2O5 full-cells.

Recent development for biomedical applications of magnetic nanoparticles.

In recent decades, the use of engineered nanoparticles has been increasing in various sectors, including biomedicine, diagnosis, water treatment, and environmental remediation leading to significant public concerns. Among these nanoparticles, magnetic nanoparticles (MNPs) have gained many attentions in medicine, pharmacology, drug delivery system, molecular imaging, and bio-sensing due to their various properties. In addition, various studies have reviewed MNPs main applications in the biomedical engineering area with intense progress and recent achievements. Nanoparticles, especially the magnetic nanoparticles, have recently been confirmed with excellent antiviral activity against different viruses, including SARS-CoV-2(Covid-19) and their recent development against Covid-19 also has also been discussed. This review aims to highlight the recent development of the magnetic nanoparticles and their biomedical applications such as diagnosis of diseases, molecular imaging, hyperthermia, bio-sensing, gene therapy, drug delivery and the diagnosis of Covid-19.

From dendritic mesoporous silica microspheres to waxberry-like hierarchical hollow carbon spheres: rational design of carbon host for lithium sulfur batteries.

Fabricating sulfur host for the cathode with strong confinement effect and high dispersion of sulfur is vitally important to the development of high-performance lithium sulfur batteries. Benefiting from their unique and tunable structure, good conductivity and chemical inertness, hollow porous carbon materials has been considered as a promising candidate. Herein, precisely designed waxberry-like hierarchical hollow carbon spheres (h-CNS) have been synthesized as the sulfur micro-containers for lithium sulfur batteries. The prepared h-CNS/S electrode shows a good rate capability of 1311 mAh g-1at 0.1 C and 962 mAh g-1at 1 C. In addition, the h-CNS/S electrode also shows satisfactory long cycle performance with 622 mAh g-1at 0.5 C and 400 mAh g-1at 4 C over 600 cycles. The desirable performance can be attributed to the wedge-shape micro-containers which improve the high dispersion of sulfur inside the channels and inhibit the loss of intermediate polysulfide. Moreover, the unique structure can also enhance the transfer of both lithium ions and electrons which benefits to the rate capability of the lithium sulfur batteries.

Estimation of non-constant variance in isothermal titration calorimetry using an ITC measurement model.

Isothermal titration calorimetry (ITC) is the gold standard for accurate measurement of thermodynamic parameters in solution reactions. In the data processing of ITC, the non-constant variance of the heat requires special consideration. The variance function approach has been successfully applied in previous studies, but is found to fail under certain conditions in this work. Here, an explicit ITC measurement model consisting of main thermal effects and error components has been proposed to quantitatively evaluate and predict the non-constant variance of the heat data under various conditions. Monte Carlo simulation shows that the ITC measurement model provides higher accuracy and flexibility than variance function in high c-value reactions or with additional error components, for example, originated from the fluctuation of the concentrations or other properties of the solutions. The experimental design of basic error evaluation is optimized accordingly and verified by both Monte Carlo simulation and experiments. An easy-to-run Python source code is provided to illustrate the establishment of the ITC measurement model and the estimation of heat variances. The accurate and reliable non-constant variance of heat is helpful to the application of weighted least squares regression, the proper evaluation or selection of the reaction model.

Chirality reversal, enhancement and transfer by pH-adjusted surfactant assembly.

The controllable chirality reversal and enhancement at a supramolecular level is crucial for the synthesis and applications of circularly active materials, which has been achieved by a pH-adjusted amphiphilic chiral surfactant assembly approach, and reveals the relationship between the chirality behavior and its assembly morphology in a non-covalent interaction regime and its ability to transfer chirality from chiral molecules to achiral ones under appropriate conditions.

Complementary autophagy inhibition and glucose metabolism with rattle-structured polydopamine@mesoporous silica nanoparticles for augmented low-temperature photothermal therapy and in vivo photoacoustic imaging.

Rattle-structured nanoparticles with movable cores, porous shells and hollow interiors have shown great effectiveness in drug delivery and cancer theranostics. Targeting autophagy and glucose have provided alternative strategies for cancer intervention therapy. Herein, rattle-structured polydopamine@mesoporous silica nanoparticles were prepared for in vivo photoacoustic (PA) imaging and augmented low-temperature photothermal therapy (PTT) via complementary autophagy inhibition and glucose metabolism. Methods: The multifunctional rattle-structured nanoparticles were designed with the nanocore of PDA and the nanoshell of hollow mesoporous silica (PDA@hm) via a four-step process. PDA@hm was then loaded with autophagy inhibitor chloroquine (CQ) and conjugated with glucose consumer glucose oxidase (GOx) (PDA@hm@CQ@GOx), forming a corona-like structure nanoparticle. Results: The CQ and GOx were loaded into the cavity and decorated onto the surface of PDA@hm, respectively. The GOx-mediated tumor starvation strategy would directly suppress the expression of HSP70 and HSP90, resulting in an enhanced low-temperature PTT induced by PDA nanocore. In addition, autophagy inhibition by the released CQ made up for the loss of low-temperature PTT and starvation efficiencies by PTT- and starvation-activated autophagy, realizing augmented therapy efficacy. Furthermore, the PDA nanocore in the PDA@hm@CQ@GOx could be also used for PA imaging. Conclusion: Such a "drugs" loaded rattle-structured nanoparticle could be used for augmented low-temperature PTT through complementarily regulating glucose metabolism and inhibiting autophagy and in vivo photoacoustic imaging.

The Role of the OH Group in Citric Acid in the Coordination with Fe3O4 Nanoparticles.

The role of the C?OH group in citric acid (CA) in the molecular coordination with Fe3O4 nanoparticles (NPs) has been elusive for a long time. In this study, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectral deconvolution and thermogravimetric analysis (TGA) have been used to quantitatively clarify its significance in CA adsorption and its corresponding conformation. The experimental results show that the coordination and the corresponding conformation are exclusively determined by COOH not C?OH at pH 3, where its adsorption behavior conforms to the Brunauer?Emmett?Teller (BET) multilayer model with a maximal monolayer coordination number of 2.1/nm2. However, C?OH is involved in the coordination at pH 10, and CA conforms to the Langmuir monolayer model with 1.4/nm2 as its maximal monolayer coordination number, which is more stable than the COOH-only coordination. Especially, the conformational transformation is observed for the first time at pH 3, where the CA molecules adjust their conformation upon elution to maximize the utilization of the available binding sites on Fe3O4 NPs. This finding deepens the understanding on the fundamental mechanism for the interaction between the C?OH and COOH groups containing the organic ligand and metal oxide.

Complex to simple: In vitro exposure of particulate matter simulated at the air-liquid interface discloses the health impacts of major air pollutants.

Particulate matter (PM) exposure poses many adverse effects on human health. However, it is challenging to clearly differentiate between the contributions of individual pollutants on toxicity from complex mixtures of ambient air pollutants. The aim of this study is to generate aerosols constituted by silica nanoparticles (NPs) and bisulfate to serve as simulators of particle-associated high-sulfur air pollution. Then, the health impacts of sulfur dioxide were evaluated at the cellular level using an air-liquid interface (ALI) exposure chamber. BEAS-2B cells were exposed to either nano-silica or bisulfite aerosol individually or bisulfate-coated silica (SiO2-NH2@HSO3) for 3 h using the ALI. The cellular toxicities were carefully compared based on the exposure dosages. The ALI exposure of SiO2 NPs alone did not produce any apparent cytotoxicity in cells, but the aerosol exposure of SiO2-NH2@HSO3 significantly decreased the cell viability and enhanced the production of cellular reactive oxygen species in a dose-dependent manner. Consequently, the excessive oxidative stress resulted in mitochondrial damage as well as cellular apoptosis. ALI exposure can possibly reflect the realistic physiological exposure condition of the human respiratory system. As a derivative of the sulfur dioxide component of air pollution, sulfate exacerbates the toxic effects of inhalable PMs. This result may be due to the large surface area of the nanoparticles, with the possibility of carrying more sulfite to the target cells during aerosol exposure. The sulfate levels offer a meaningful complement to the present PM2.5 index of air pollution for achieving better human health protection.

Effects of Hollow CeO2 Nanospheres on Flame Retardance and Smoke Suppression of Room-Temperature-Vulcanized Silicone Rubber.

The effects of hollow CeO2 nanospheres on the flame-retardance and smoke-suppression properties of room-temperature-vulcanized (RTV) silicone rubber were studied. It was observed that the flame retardance of RTV silicone rubber composites was improved by hollow CeO2 nanospheres. Surprisingly, the nanospheres also enhanced the smoke-suppression characteristics of the composites. The limited oxygen index of RTV/Mg(OH)2 was raised from 23.7 to 25.9 by the addition of hollow CeO2 nanospheres, while the smoke density was reduced markedly, from 35.1 to 17.6. The thermal stability and char yield of the RTV silicone rubber composites were characterized by thermogravimetric techniques. Furthermore, the degradation product of the composites was analyzed by pyrolysis-gas chromatography-mass spectroscopy. A mechanism to explain the observed results is proposed.

Conformation-Dependent Coordination of Carboxylic Acids with Fe3O4 Nanoparticles Studied by ATR-FTIR Spectral Deconvolution.

The coordination of valeric acid (VA), glutaric acid (GA), and tricarballylic acid (TA) with Fe-OH on the Fe3O4 nanoparticle surface has been systematically studied to elucidate the effects of COOH, molecular configuration, and ligand concentration on the coordination by the combined use of attenuated total reflectance Fourier transform infrared (ATR-FTIR) and thermogravimetric analysis (TGA). The results show that the binding ability of the acids increases with the increase in the COOH number. Multiple conformations coexist for the dicarboxylic and tricarboxylic acid coordinated on the iron oxide NPs. Saturated coordination formed with only a one-, two-, or three-COOH conformation for VA, GA, and TA, respectively, occurs under ligand-scarce conditions, while unsaturated coordination formed with the mixture of uncoordinated, one-, and/or two-COOH conformations for VA, GA, and TA, respectively, exists under ligand-abundant conditions. The maximum coordination numbers for monolayer adsorption for VA, GA, and TA on Fe3O4 NPs are 9, 2.4, and 2.7 nm-2, respectively. This study helps us to understand the fine coordination mechanism caused by the acid molecules with different configurations and elucidates, for the first time, the fine conformational variance incurred by the surrounding ligand with different concentrations and the way in which the ligand is added.

Auto-fluorescent polymer nanotheranostics for self-monitoring of cancer therapy via triple-collaborative strategy.

Aberrant regulation of angiogenesis supply sufficient oxygen and nutrients to exacerbate tumor progression and metastasis. Taking this hallmark of cancer into account, reported here is a self-monitoring and triple-collaborative therapy system by auto-fluorescent polymer nanotheranostics which could be concurrently against angiogenesis and tumor cell growth by combining the benefits of anti-angiogenesis, RNA interfere and photothermal therapy (PTT). Auto-fluorescent amphiphilic polymer polyethyleneimine-polylactide (PEI-PLA) with positive charge can simultaneously load hydrophobic antiangiogenesis agent combretastatin A4 (CA4), NIR dye IR825 and absorb negatively charged heat shock protein 70 (HSP70) inhibitor (siRNA against HSP70) to construct self-monitoring nanotheranostics (NPICS). NPICS can effectively restrain the expression of HSP70 to reduce their endurance to the IR825-mediated PTT, leading to an enhanced photocytotoxicity. In a xenograft mouse tumor model, NPICS show an effect of inhibition of tumor angiogenesis and also display a highly synergistic anticancer efficacy with NIR laser irradiation. Significantly, based on its inherent auto-fluorescence, PEI-PLA not only serves as the drug carrier, but also as the self-monitor to real-time track NPICS biodistribution and tumor accumulation via fluorescence imaging. Moreover, IR825 endows NPICS could also be used as photoacoustic (PA) agents for in vivo PA imaging. This nanoplatform shows enormous potentials in cancer theranostics.

Size-dependent adsorption and its application in determining the number of surfactant molecule adsorbed on multimodal SiO2 particles by 2D-DCS.

Quantitative analysis using surfactant-particles interaction is the basis for many applications. In situ measurements of surfactant adsorption on nanoparticles are important to understanding adsorption kinetics. However, it is quite difficult to determine the individual numbers for each monomodal particles in a multimodal mixture system by current technologies. To cope with this problem, a new method, i.e. 2D differential centrifugal sedimentation (2D-DCS), has been developed and applied in situ to measure the number of CTAB molecules adsorbed on the surface of silica particles, assuming that the adlayer is composed of a compact CTAB monolayer. Results show that 2D-DCS can measure the adsorption amount for particles not only with single size distribution but also with multiple size distributions. The number of adsorbed CTAB per nm2 on silica particles determined by 2D-DCS are 1.4 and 3.9 for the monomodal particles of 210 and 1000 nm, respectively, which is similar to that measured by ζ-potential, DLS and UV-vis spectrometry, and 1.4, 2.3 and 2.5 for 210, 430 and 700 nm particles, respectively, for a trimodal particle system, where the size-dependent adsorption is difficult to be simultaneously measured by other technologies.

Experimental and Modeling Studies on the Filtration of SiO2 Nanoparticles Aerosolized from Different Solvents.

The filtration performance of a fibrous filter in removing nano-SiO2 aerosols atomized using different solvents including methanol, ethanol, 1-propanol, water, and the ethanol/water mixture has been investigated. Through discrete element method (DEM) simulation and filtration experiments, the efficiency variation caused by the combinative interaction of the particle-filter adhesion and interparticle attraction has been analyzed and verified. The adhesion force between the solvent-coated nanoparticles and the filter is considered as the key factor to influence their initial filtration efficiency and can be balanced by their interparticle interaction. The stronger the adhesion, the higher the initial filtration efficiency. Primary aggregate is formed through the particle-fiber interaction, and further agglomerate is caused by particle migration on the fibers, i.e. secondary aggregate. Hydrogen bonding interaction is considered as the main factor causing interparticle secondary agglomeration, and plenty of OH groups existing in the nano-SiO2 aerosols yielded from alcohol promotes the particle secondary aggregation. As a result, the Brown diffusion capture of the filter is significantly abated, and the as-formed agglomerate is scraped off the filter surface by the alcohol molecules, causing the filtration efficiency decreases. This study highlights the surface affinity properties of nanoaerosols and their balance between particle-particle and particle-fiber interactions in the filtration process.

Synergetic Determination of Thermodynamic and Kinetic Signatures Using Isothermal Titration Calorimetry: A Full-Curve-Fitting Approach.

Thermodynamic and kinetic signatures are pivotal information for revealing the binding mechanisms of biomolecules, and they play an indispensable role in drug discovery and optimization. While noncalorimetric methods measure only a part of these signatures, isothermal titration calorimetry (ITC) is considered to have the potential to acquire full signatures in an experiment. However, kinetic parameters are generally difficult to extract from ITC curves, as they are inevitably affected by the instrument-response function and the collateral heat of associated process during titrations. Thus, we herein report the development and validation of a full-curve-fitting method to resolve thermal power curves and to maximize the signal extraction using ITC. This method is then employed to quantify the dilution of an aqueous n-propanol solution and examine the inhibition of carbonic anhydrase by 4-carboxybenzenesulfonamide using a commercial instrument with a long apparent response time of ∼13 s.

In Situ Measurement of Surface Functional Groups on Silica Nanoparticles Using Solvent Relaxation Nuclear Magnetic Resonance.

In situ analysis and study on the surface of nanoparticles (NPs) is a key to obtain their important physicochemical properties for the subsequent applications. Of them, most works focus on the qualitative characterization whereas quantitative analysis and measurement on the NPs under their storage and usage conditions is still a challenge. In order to cope with this challenge, solvation relaxation-based nuclear magnetic resonance (NMR) technology has been applied to measure the wet specific surface area and, therefore, determine the number of the bound water molecules on the surface of silica NPs in solution and the hydrophilic groups of various types grafted on the surface of the NPs. By changing the surface functional group on silica particles, the fine distinction for the solvent-particle interaction with different surface group can be quantitatively differentiated by measuring the number of water molecules absorbed on the surface. The results show that the number of the surface hydroxyl, amine, and carboxyl group per nm2 is 4.0, 3.7, and 2.3, respectively, for the silica particles with a diameter of 203 nm. The method reported here is the first attempt to determine in situ the number of bound solvent molecules and any solvophilic groups grafted on nanoparticles.