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•Metal nanozyme-based detection of heavy metal ions is reviewed.•Detection strategies for improving selectivity and reliability are reviewed.•The challenges in nanozyme-based assays ...for heavy metal ions are highlighted.•Future perspective of nanozyme-based assays for heavy metal ions is discussed.
Large scale mining, manufacturing industries, exploitation of underground water, depletion of groundwater level, and uncontrolled discharge of industrial wastes have caused severe heavy metal ion pollution to the environment throughout the world. Therefore, the rapid detection of such toxic metal ions is inevitable. However, conventional methods require sophisticated instruments and skilled manpower and are difficult to operate in on-field conditions. Recently, metal nanozyme-based assays have been found to have the potential as an alternative to conventional methods due to their portability, simplicity, and high sensitivity to detect metal ion concentration to as low as parts per trillion (ppt). Metal nanozyme-based systems for heavy metal ions enable rapid and cheap screening on the spot with a very simple instrument such as a UV–vis absorption spectrophotometer and therefore, are convenient for use in field operations, especially in remote parts of the world. The sensing mechanism of a nanozyme-based sensor is highly dependent on its surface properties and specific interactions with particular metal ion species. Such method often encounters selectivity issues, unlike natural enzyme-based assays. Therefore, in this review, we mainly focus our discussion on different types of target recognition and inhibition/enhancement mechanisms, and their responses toward the catalytic activity in the sensing of target metal ions, design strategies, challenges, and future perspectives.
Exosomes are secreted into the extracellular space by most cell types and contain various molecular constituents, which play roles in many biological processes. Adipose‐derived mesenchymal stem cells ...(ADSCs) can differentiate into a variety of cell types and secrete a series of paracrine factors through exosomes. ADSC‐derived exosomes have shown diagnostic and therapeutic potential in many clinical diseases. The molecular components are critical for their mechanisms. Several methods have been developed for exosome purification, including ultracentrifugation, ultrafiltration, density gradient purification, size‐based isolation, polymer precipitation and immuno‐affinity purification. Thus, we employed four methods to isolate exosomes from the hADSC culture medium, including ultracentrifugation, size exclusion chromatography, ExoQuick‐TC precipitation and ExoQuick‐TC ULTRA isolation. Following exosome isolation, we performed quantitative proteomic analysis of the exosome proteins using isobaric tags for relative and absolute quantification (iTRAQ) labelling, combined with 2D‐LC‐MS/MS. There were 599 universal and 138 stably expressed proteins in hADSC‐derived exosomes. We proved that these proteins were potential hADSC‐derived exosomes markers, including CD109, CD166, HSPA4, TRAP1, RAB2A, RAB11B and RAB14. From the quantitative proteomic analysis, we demonstrated that hADSC‐derived exosome protein expression varied, with lipopolysaccharide (LPS) treatment, in the different isolation methods. Pathway analysis and proliferation, migration and endothelial tube formation assays showed varying effects in cells stimulated with hADSC‐derived exosomes from different isolation methods. Our study revealed that different isolation methods might introduce variations in the protein composition in exosomes, which reflects their effects on biological function. The pros and cons of these methods are important points to consider for downstream research applications.
This paper investigates the effect of R&D internationalization on firm innovation performance. Using a longitudinal dataset of Taiwanese high-tech firms, we test the effects of R&D ...internationalization in terms of intensity and diversity. Results reveal a curvilinear U-shaped relationship, suggesting the benefits of R&D internationalization eventually outweigh the costs after critical levels of intensity and diversity. Additionally, we find that a firm's experience in foreign expansion may have a positive moderating impact on the relationship between R&D internationalization and innovation performance, which suggests that the effect is contingent on the firm's capability in dealing with the complexities and uncertainties inherent in international business.
A self-assembled nanocomposite is prepared from an aqueous mixture of aptamer-modified gold nanoparticles (Apt–Au NPs), bismuth ions and chloride ions. The Apt–Au NPs are immobilized on bismuth ...oxychloride (BiOCl) nanosheets in situ to form Apt–Au NPs/BiOCl nanocomposites. The as-prepared nanocomposites exhibit high peroxidase-like activity for the catalytic conversion of Amplex Red (AR) to fluorescent resorufin in the presence of H2O2. The catalytic activity of Apt–Au NPs/BiOCl nanocomposites is at least 90-fold higher than that of Apt–Au NPs or BiOCl nanosheets, revealing synergistic effects on their activity. The catalytic activity of Apt–Au NPs/BiOCl nanocomposites is suppressed by vascular endothelial growth factor-A165 (VEGF-A165) molecules that specifically interact with the aptamer units (Del-5-1 and v7t-1) on the nanocomposite surface. The AR/H2O2–Apt–Au NPs/BiOCl nanocomposites probe shows high selectivity (>1000-fold over other proteins) and sensitivity (detection limit ~0.5nM) for the detection of VEGF-A165. Furthermore, the probe is employed for the detection of VEGF isoforms and for the study of interactions between VEGF and VEGF receptors. The practicality of this simple, rapid, cost-effective probe is validated by the analysis of VEGF-A165 in cell culture media, showing its great potential for the analysis of VEGF in biological samples.
Aptamer-modified gold nanoparticles (Apt–Au NPs) are immobilized onto bismuth oxychloride (BiOCl) nanosheets in situ to form Apt–Au NPs/BiOCl nanocomposites. The peroxidase-like activity of Apt–Au NPs/BiOCl nanocomposites is suppressed by vascular endothelial growth factor-A165 (VEGF-A165) molecules that specifically interact with the aptamer units on the nanocomposite surface.
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•Aptamer-modified gold nanoparticles are immobilized on BiOCl nanosheets.•The nanocomposites exhibit high peroxidase-like activity.•Catalytic activity of the nanocomposites is suppressed by VEGF.•Analysis of VEGF isoforms and their interaction to receptors.
Exosomes secreted by adipose-derived stem cells (ADSC-exo) reportedly improve nerve regeneration after peripheral nerve injury. Herein, we investigated whether pretreatment of ADSCs with FK506, an ...immunosuppressive drug that enhances nerve regeneration, could secret exosomes (ADSC-F-exo) that further augment nerve regeneration. Designed exosomes were topically applied to injured nerve in a mouse model of sciatic nerve crush injury to assess the nerve regeneration efficacy. Outcomes were determined by histomorphometric analysis of semi-thin nerve sections stained with toluidine blue, mouse neurogenesis PCR array, and neurotrophin expression in distal nerve segments. Isobaric tags for relative and absolute quantitation (iTRAQ) were used to profile potential exosomal proteins facilitating nerve regeneration. We observed that locally applied ADSC-exo and ADSC-F-exo significantly enhanced nerve regeneration after nerve crush injury. Pretreatment of ADSCs with FK506 failed to produce exosomes possessing more potent molecules for enhanced nerve regeneration. Proteomic analysis revealed that of 192 exosomal proteins detected in both ADSC-exo and ADSC-F-exo, histone deacetylases (HDACs), amyloid-beta A4 protein (APP), and integrin beta-1 (ITGB1) might be involved in enhancing nerve regeneration.
Functional logic gates based on lead ions (Pb2+) and mercury ions (Hg2+) that induce peroxidase-like activities in gold nanoparticles (Au NPs) in the presence of platinum (Pt4+) and bismuth ions ...(Bi3+) are presented. The “AND” logic gate is constructed using Pt4+/Pb2+ as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as “Pt4+/Pb2+(AND)–Au NPPOX”. When Pt4+ and Pb2+ coexist, strong metallophilic interactions (between Pt and Pb atoms/ions) and aurophilic interactions (between Au and Pb/Pt atoms/ions) result in significant increases in the deposition of Pt and Pb atoms/ions onto the Au NPs, leading to enhanced peroxidase-like activity. The “INHIBIT” logic gate is fabricated by using Bi3+ and Hg2+ as the input and the peroxidase-like activity of the Au NPs as the output; this logic gate is denoted as “Bi3+/Hg2+(INHIBIT)–Au NPPOX”. High peroxidase-like activity of Au NPs in the presence of Bi3+ is a result of the various valence (oxidation) states of Bi3+ and Au (Au+/Au0) atoms on the nanoparticle’s surface. When Bi3+ and Hg2+ coexist, strong Hg–Au amalgamation results in a large decrease in the peroxidase-like activity of the Au NPs. These two probes (Pt4+/Pb2+(AND)–Au NPPOX and Bi3+/Hg2+(INHIBIT)–Au NPPOX) allow selective detection of Pb2+ and Hg2+ down to nanomolar quantities. The practicality of these two probes has been validated by analysis of Pb2+ and Hg2+ in environmental water samples (tap water, river water, and lake water). In addition, an integrated logic circuit based on the color change (formation of reddish resorufin product) and generation of O2 bubbles from these two probes has been constructed, allowing visual detection of Pb2+ and Hg2+ in aqueous solution.
Conventional IB theories stress the importance and implications of a firm's exploitative strategy. However, the unprecedented competitive nature of contemporary business necessitates firm ...“ambidexterity” — the simultaneous execution of exploitation and exploration activities. Using balanced panel data of 207 Taiwanese firms spanning six years, this research examines the effects of international ambidexterity on firm performance. Findings reveal that ambidexterity promotes a firm's performance. For firms from small emerging economies, international ambidexterity is highly vulnerable to environmental complexity and sensitive to previous international experience and the firm's capability to conduct international business. These factors significantly moderate firm performance.
Platelet-rich plasma (PRP) is beneficial for clinical applications in various medical fields. Although commercial PRP preparation kits are already available in the market, most of these kits employ ...centrifugation.
We used a new cationic copolymer coating on a polyurethane (PU) sponge to promote platelet separation from the blood. This copolymer showed no cytotoxicity against cell viability or hemolysis. We further evaluated the efficiency of the new PRP preparation device by comparing it with that of a commercially available kit (RegenKit-THT).
We demonstrated that PRP obtained using copolymer device contains high concentrations of platelets and angiogenic growth factors (epidermal growth factor, vascular endothelial growth factor-A, growth differentiation factor 2, and interleukin-8). The separated PRP also displayed beneficial effects on cell migration, angiogenesis, and matrix metalloproteinase gene expression.
Based on these results, we developed a cationic copolymer-coated PU sponge as a PRP preparation device without the need for any centrifugation.
•We described the positive ionic copolymers (PICs) with platelet adsorption ability.•PICs adsorb platelet without destroying RBC and with a good WBC removal.•PICs provide a convenient method for PRP separation without centrifugation.
In this study we employed self-deposition and competitive or synergistic interactions between metal ions and gold nanoparticles (Au NPs) to develop OR, AND, INHIBIT, and XOR logic gates through ...regulation of the enzyme-like activity of Au NPs. In the presence of various metal ions (Ag(+), Bi(3+), Pb(2+), Pt(4+), and Hg(2+)), we found that Au NPs (13 nm) exhibited peroxidase-, oxidase-, or catalase-like activity. After Ag(+), Bi(3+), or Pb(2+) ions had been deposited on the Au NPs, the particles displayed strong peroxidase-like activity; on the other hand, they exhibited strong oxidase- and catalase-like activities after reactions with Ag(+)/Hg(2+) and Hg(2+)/Bi(3+) ions, respectively. The catalytic activities of these Au NPs arose mainly from the various oxidation states of the surface metal atoms/ions. Taking advantage of this behavior, we constructed multiplex logic operations-OR, AND, INHIBIT, and XOR logic gates-through regulation of the enzyme-like activity after the introduction of metal ions into the Au NP solution. When we deposited Hg(2+) and/or Bi(3+) ions onto the Au NPs, the catalase-like activities of the Au NPs were strongly enhanced (>100-fold). Therefore, we could construct an OR logic gate by using Hg(2+)/Bi(3+) as inputs and the catalase-like activity of the Au NPs as the output. Likewise, we constructed an AND logic gate by using Pt(4+) and Hg(2+) as inputs and the oxidase-like activity of the Au NPs as the output; the co-deposition of Pt and Hg atoms/ions on the Au NPs was responsible for this oxidase-like activity. Competition between Pb(2+) and Hg(2+) ions for the Au NPs allowed us to develop an INHIBIT logic gate-using Pb(2+) and Hg(2+) as inputs and the peroxidase-like activity of the Au NPs as the output. Finally, regulation of the peroxidase-like activity of the Au NPs through the two inputs Ag(+) and Bi(3+) enabled us to construct an XOR logic gate.
In this paper, we report a simple one-step synthesis method for silver-gold bimetallic nanoparticles deposition on silver chloride nanosheets to form Ag-Au/AgCl nanohybrid with oxidase-like and ...peroxidase-like catalytic activity. We used these nanohybrid in the detection of spermine. First, 13 nm-sized Au NPs were synthesized by citrate reduction of HAuCl4 solution, and then, Ag+ ions were added to the solution without any purification. The added Ag+ reacted with the Cl− ions in the dispersion, thus immediately forming AgCl nanosheets through a precipitation reaction, and the aurophilic interactions with the Au NPs resulted in the formation and in situ self-deposition of Ag-Au NPs on the AgCl nanosheets at room temperature. We investigated the enzyme-mimicking activity of the Ag-Au/AgCl nanohybrid in detail via the O2- or H2O2-Amplex Red (AR) redox system. The Ag-Au/AgCl nanohybrid exhibited at least 150-fold higher catalytic activity than that of Ag-Au NPs or AgCl nanosheets, due to synergistic effect. Spermine inhibited the enzyme-mimic activity of the Ag-Au/AgCl nanohybrid, thereby allowing for the construction of a probe for detecting nanomolar concentrations of spermine in urine samples. This cost-effective sensing system was used to easily and rapidly detect the concentrations of spermine in complex urine samples.
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•Silver-gold bimetallic nanoparticles deposited on silver chloride nanosheets to form Ag-Au/AgCl nanohybrid.•Ag-Au/AgCl nanohybrid exhibit high peroxidase-like and oxidase-like activities.•Catalytic activity of Ag-Au/AgCl nanohybrid is suppressed by spermines.•H2O2/AR–Ag-Au/AgCl nanohybrid allowed for the detection of spermine in human urine samples.
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