Purification of quantum dot-based bioprobes with a salting out strategy.

A salting out strategy is reported for purification of IgG-conjugated QD (IgG-QD) bioprobes. Adding NaCl can precipitate free IgG selectively, while the IgG-QD maintains good colloidal stability. The dynamic light scattering technique reveals that this is due to the relatively positive zeta potential of free IgG than that of the IgG-QD.

Online discovery of the molecular mechanism for directionally detoxification of Fuzi using real-time extractive electrospray ionization mass spectrometry.

ETHNOPHARMACOLOGICAL RELEVANCE: Aconitum carmichaelii Debeaux, a famous traditional medicinal herb for collapse, rheumatic fever, and painful joints, always raises global concerns about its fatal toxicity from toxic alkaloids when improperly processed. Therefore, it is urgent to clarify the internal molecular mechanism of processing detoxification on Aconitum and develop simple and reliable approaches for clinical application, which is also of great significance to the rational medicinal use of Aconitum. AIM OF THE STUDY: The study aimed at developing a complete molecular mechanism exploration strategy in complex medicinal herb decocting system, clarifying the internal molecular mechanism of processing detoxification on Aconitum, and exploring valid approaches for detoxification. MATERIALS AND METHODS: Aconiti Lateralis Radix Praeparata (Fuzi) was selected as the model for exploring the complex Aconitum detoxification mechanism using an advanced online real-time platform based on extractive electrospray ionization mass spectrometry. The methods realized the sensitive capture of dynamic trace intermediates, accurate qualitative and quantitative analysis, and real-time and long-term monitoring of multi-components with satisfactory accuracy and resistance to complex matrices. RESULTS: Components in the complex Aconitum decocting system were real-timely characterized and fat meat was discovered and verified to directionally detoxify Aconitum while reserving the therapy effect. More importantly, the dynamic detoxification mechanism in the chemically complex Aconitum decoction was molecularly profiled. A novel reaction pathway based on nucleophilic substitution reaction mechanism was proposed. As confirmed by the theoretic calculations at DFT B3LYP/6-31G (d) levels, fatty acids (e.g., palmitic acid) acted as a green, cheap, and high-performance catalyst and promote the decomposition of toxic diester alkaloids to non-toxic and active benzoyl-monoester alkaloids through the discovered mechanism. CONCLUSION: The study exposed a novel detoxification molecular mechanism of Aconitum and provided an effective method for the safe use of Aconitum, which could effectively guide the development of traditional processing technology and compatibility regulation of the toxic herb and had great value to the modernization and standardization development of traditional medicine.

Limitation standard of toxic aconitines in Aconitum proprietary Chinese medicines using on-line extraction electrospray ionization mass spectrometry.

Development of rapid analytical methods and establishment of toxic component limitation standards are of great importance in quality control of traditional Chinese medicine. Herein, an on-line extraction electrospray ionization mass spectrometry (oEESI-MS) coupled with a novel whole process integral quantification strategy was developed and applied to direct determination of nine key aconitine-type alkaloids in 20 Aconitum proprietary Chinese medicines (APCMs). Multi-type dosage forms (e.g., tablets, capsules, pills, granules, and liquid preparation) of APCM could be determined directly with excellent versatility. The strategy has the characteristics of high throughput, good tolerance of matrix interference, small amount of sample (∼0.5 mg) and reagent (∼240 µL) consumption, and short analysis time for single sample (<15 min). The results were proved to be credible by high performance liquid chromatography-mass spectrometry (LC-MS) and electrospray ionization mass spectrometry, respectively. Moreover, the limitation standard for the toxic aconitines in 20 APCMs was established based on the holistic weight toxicity (HWT) evaluation and the Chinese Pharmacopoeia severally, and turned out that HWT-based toxicity evaluation results were closer to the real clinical applications. Hence, a more accurate and reliable APCM toxicity limitation was established and expected to play an important guiding role in clinics. The current study extended the power of ambient MS as a method for the direct quantification of molecules in complex samples, which is commonly required in pharmaceutical analysis, food safety control, public security, and many other disciplines.

Stretchable and Photocatalytically Renewable Electrochemical Sensor Based on Sandwich Nanonetworks for Real-Time Monitoring of Cells.

Stretchable electrochemical (EC) sensors have broad prospects in real-time monitoring of living cells and tissues owing to their excellent elasticity and deformability. However, the redox reaction products and cell secretions are easily adsorbed on the electrode, resulting in sensor fouling and passivation. Herein, we developed a stretchable and photocatalytically renewable EC sensor based on Au nanotubes (NTs) and TiO2 nanowires (NWs) sandwich nanonetworks. The external Au NTs are used for EC sensing, and internal TiO2 NWs provide photocatalytic performance to degrade contaminants, which endows the sensor with excellent EC performance, high photocatalytic activity, and favorable mechanical tensile property. This allows highly sensitive recycling monitoring of NO released from endothelial cells and 5-HT released from mast cells under their stretching states in real time, therefore providing a promising tool to unravel elastic and mechanically sensitive cells, tissues, and organs.

Conductive Polymer-Coated Carbon Nanotubes To Construct Stretchable and Transparent Electrochemical Sensors.

Carbon nanotube (CNT)-based flexible sensors have been intensively developed for physical sensing. However, great challenges remain in fabricating stretchable CNT films with high electrochemical performance for real-time chemical sensing, due to large sheet resistance of CNT film and further resistance increase caused by separation between each CNT during stretching. Herein, we develop a facile and versatile strategy to construct single-walled carbon nanotubes (SWNTs)-based stretchable and transparent electrochemical sensors, by coating and binding each SWNT with conductive polymer. As a polymer with high conductivity, good electrochemical activity, and biocompatibility, poly(3,4-ethylenedioxythiophene) (PEDOT) acting as a superior conductive coating and binder reduces contact resistance and greatly improves the electrochemical performance of SWNTs film. Furthermore, PEDOT protects the SWNTs junctions from separation during stretching, which endows the sensor with highly mechanical compliance and excellent electrochemical performance during big deformation. These unique features allow real-time monitoring of biochemical signals from mechanically stretched cells. This work represents an important step toward construction of a high performance CNTs-based stretchable electrochemical sensor, therefore broadening the way for stretchable sensors in a diversity of biomedical applications.

High-Efficiency Capture of Individual and Cluster of Circulating Tumor Cells by a Microchip Embedded with Three-Dimensional Poly(dimethylsiloxane) Scaffold.

Effective isolation of circulating tumor cells (CTCs) has great significance for cancer research but is highly challenged. Here, we developed a microchip embedded with a three-dimensional (3D) PDMS scaffold by a quadratic-sacrificing template method for high-efficiency capture of CTCs. The microchip was gifted with a 3D interconnected macroporous structure, strong toughness, and excellent flexibility and transparency, enabling fast isolation and convenient observation of CTCs. Especially, 3D scaffold chip perfectly integrates the two main strategies currently used for enhancement of cell capture efficiency. Spatially distributed 3D scaffold compels cells undergoing chaotic or vortex migration in the channel, and the spatially distributed nanorough skeleton offers ample binding sites, which synergistically and significantly improve CTCs capture efficiency. Our results showed that 1-118 CTCs/mL were identified from 14 cancer patients' blood and 5 out of these cancer patients showed 1-14 CTC clusters/mL. This work demonstrates for the first time the development of microchip with transparent interconnected 3D scaffold for isolation of CTCs and CTC clusters, which may promote in-depth analysis of CTCs.

Photocatalysis-Induced Renewable Field-Effect Transistor for Protein Detection.

The field-effect transistor (FET) biosensor has attracted extensive attentions, due to its unique features in detecting various biomolecules with high sensitivity and selectivity. However, currently used FET biosensors obtaining from expensive and elaborate micro/nanofabrication are always disposable because the analyte cannot be efficiently removed after detection. In this work, we established a photocatalysis-induced renewable graphene-FET (G-FET) biosensor for protein detection, by layer-to-layer assembling reduced graphene oxide (RGO) and RGO-encapsulated TiO2 composites to form a sandwiching RGO@TiO2 structure on a prefabricated FET sensor surface. After immobilization of anti-D-Dimer on the graphene surface, sensitive detection of D-Dimer was achieved with the detection limits of 10 pg/mL in PBS and 100 pg/mL in serum, respectively. Notably, renewal of the FET biosensor for recycling measurements was significantly realized by photocatalytically cleaning the substances on the graphene surface. This work demonstrates for the first time the development and application of photocatalytically renewable G-FET biosensor, paving a new way for G-FET sensor toward a plethora of diverse applications.

Stretchable Electrochemical Sensor for Real-Time Monitoring of Cells and Tissues.

Stretchable electrochemical sensors are conceivably a powerful technique that provides important chemical information to unravel elastic and curvilinear living body. However, no breakthrough was made in stretchable electrochemical device for biological detection. Herein, we synthesized Au nanotubes (NTs) with large aspect ratio to construct an effective stretchable electrochemical sensor. Interlacing network of Au NTs endows the sensor with desirable stability against mechanical deformation, and Au nanostructure provides excellent electrochemical performance and biocompatibility. This allows for the first time, real-time electrochemical monitoring of mechanically sensitive cells on the sensor both in their stretching-free and stretching states as well as sensing of the inner lining of blood vessels. The results demonstrate the great potential of this sensor in electrochemical detection of living body, opening a new window for stretchable electrochemical sensor in biological exploration.

Photochemical Synthesis of Shape-Controlled Nanostructured Gold on Zinc Oxide Nanorods as Photocatalytically Renewable Sensors.

Biosensors always suffer from passivation that prevents their reutilization. To address this issue, photocatalytically renewable sensors composed of semiconductor photocatalysts and sensing materials have emerged recently. In this work, we developed a robust and versatile method to construct different kinds of renewable biosensors consisting of ZnO nanorods and nanostructured Au. Via a facile and efficient photochemical reduction, various nanostructured Au was obtained successfully on ZnO nanorods. As-prepared sensors concurrently possess excellent sensing capability and desirable photocatalytic cleaning performance. Experimental results demonstrate that dendritic Au/ZnO composite has the strongest surface-enhanced Raman scattering (SERS) enhancement, and dense Au nanoparticles (NPs)/ZnO composite has the highest electrochemical activity, which was successfully used for electrochemical detection of NO release from cells. Furthermore, both of the SERS and electrochemical sensors can be regenerated efficiently for renewable applications via photodegrading adsorbed probe molecules and biomolecules. Our strategy provides an efficient and versatile method to construct various kinds of highly sensitive renewable sensors and might expand the application of the photocatalytically renewable sensor in the biosensing area.

Processing and properties of magnesium containing a dense uniform dispersion of nanoparticles.

Magnesium is a light metal, with a density two-thirds that of aluminium, is abundant on Earth and is biocompatible; it thus has the potential to improve energy efficiency and system performance in aerospace, automobile, defence, mobile electronics and biomedical applications. However, conventional synthesis and processing methods (alloying and thermomechanical processing) have reached certain limits in further improving the properties of magnesium and other metals. Ceramic particles have been introduced into metal matrices to improve the strength of the metals, but unfortunately, ceramic microparticles severely degrade the plasticity and machinability of metals, and nanoparticles, although they have the potential to improve strength while maintaining or even improving the plasticity of metals, are difficult to disperse uniformly in metal matrices. Here we show that a dense uniform dispersion of silicon carbide nanoparticles (14 per cent by volume) in magnesium can be achieved through a nanoparticle self-stabilization mechanism in molten metal. An enhancement of strength, stiffness, plasticity and high-temperature stability is simultaneously achieved, delivering a higher specific yield strength and higher specific modulus than almost all structural metals.

Real-time monitoring of H2O2 release from single cells using nanoporous gold microelectrodes decorated with platinum nanoparticles.

Here, we report a self-supported nanoporous gold microelectrode decorated with well-dispersed and tiny platinum nanoparticles as an electrochemical nonenzymatic hydrogen peroxide biosensor. Nanoporous gold was fabricated by electrochemical alloying/dealloying and then small-sized platinum nanoparticles were electrodeposited uniformly on them. This novel hybrid nanostructure endows the sensor with high sensitivity and selectivity towards the reduction of hydrogen peroxide with a low detection limit of 0.3 nM. The sensor has been successfully applied for the measurement of H2O2 release from a single isolated human breast cancer cell, demonstrating its great potential for further physiological and pathological applications.

Functionalized graphene-based biomimetic microsensor interfacing with living cells to sensitively monitor nitric oxide release.

It is a great challenge to develop electrochemical sensors with superior sensitivity that concurrently possess high biocompatibility for monitoring at the single cell level. Herein we report a novel and reusable biomimetic micro-electrochemical sensor array with nitric oxide (NO) sensing-interface based on metalloporphyrin and 3-aminophenylboronic acid (APBA) co-functionalized reduced graphene oxide (rGO). The assembling of high specificity catalytic but semi-conductive metalloporphyrin with high electric conductive rGO confers the sensor with sub-nanomolar sensitivity. Further coupling with the small cell-adhesive molecule APBA obviously enhances the cytocompatibility of the microsensor without diminishing the sensitivity, while the reversible reactivity between APBA and cell membrane carbohydrates allows practical reusability. The microsensor was successfully used to sensitively monitor, in real-time, the release of NO molecules from human endothelial cells being cultured directly on the sensor. This demonstrates its potential application in the detection of NO with very low bioactive concentrations for the better understanding of its physiological function and for medical tracking of patient states.

Photocatalytically Renewable Micro-electrochemical Sensor for Real-Time Monitoring of Cells.

Electrode fouling and passivation is a substantial and inevitable limitation in electrochemical biosensing, and it is a great challenge to efficiently remove the contaminant without changing the surface structure and electrochemical performance. Herein, we propose a versatile and efficient strategy based on photocatalytic cleaning to construct renewable electrochemical sensors for cell analysis. This kind of sensor was fabricated by controllable assembly of reduced graphene oxide (RGO) and TiO2 to form a sandwiching RGO@TiO2 structure, followed by deposition of Au nanoparticles (NPs) onto the RGO shell. The Au NPs-RGO composite shell provides high electrochemical performance. Meanwhile, the encapsulated TiO2 ensures an excellent photocatalytic cleaning property. Application of this renewable microsensor for detection of nitric oxide (NO) release from cells demonstrates the great potential of this strategy in electrode regeneration and biosensing.

Rapid control of phase growth by nanoparticles.

Effective control of phase growth under harsh conditions (such as high temperature, highly conductive liquids or high growth rate), where surfactants are unstable or ineffective, is still a long-standing challenge. Here we show a general approach for rapid control of diffusional growth through nanoparticle self-assembly on the fast-growing phase during cooling. After phase nucleation, the nanoparticles spontaneously assemble, within a few milliseconds, as a thin coating on the growing phase to block/limit diffusion, resulting in a uniformly dispersed phase orders of magnitude smaller than samples without nanoparticles. The effectiveness of this approach is demonstrated in both inorganic (immiscible alloy and eutectic alloy) and organic materials. Our approach overcomes the microstructure refinement limit set by the fast phase growth during cooling and breaks the inherent limitations of surfactants for growth control. Considering the growing availability of numerous types and sizes of nanoparticles, the nanoparticle-enabled growth control will find broad applications.