Nano-sized cellulose crystals were fabricated from microcrystalline cellulose (MCC) using combined sulfuric acid hydrolysis and high-pressure homogenization techniques. The crystals were then ...utilized to prepare polymethylmethacrylate (PMMA) nanocomposites by the solution casting method. The cellulose nanocrystals had diameters from about 8 to 10
nm and lengths in the range of 60–120
nm. Wide-angle X-ray diffraction (WXRD) results on the freeze-dried crystals revealed a slight increase in the degree of crystallinity after acid treatment. The composite sheets retained good transparency due to the size effect and dispersion of the cellulose nanocrystals. The thermogravimetric analysis indicated retained thermal stability of the composites. The storage modulus of the nanocomposite sheets from dynamic mechanical analysis showed significantly enhanced property in comparison with that of the pure PMMA sheets. The glass transition of the nanocomposites was shifted to lower temperatures with respect to the pure PMMA material.
•Au nanoparticles and Cu-MOFs cooperatively catalyze the oxidation of glucose.•The target initiates strand displacement reaction cycle for signal amplification.•An origami electrochemical device with ...portable owns extremely high sensitivity.
A novel electrochemical biosensor based on hairpin assembly target recycling for signal amplification and Au nanoparticles (AuNPs) modified Cu-based metal-organic frameworks (Cu-MOFs) for catalysis was constructed for highly sensitive detection of microRNA (miRNA). It was worth noting that the recycling of target was finished only based on strand displacement reaction without nuclease. In addition, a novel catalytic material of Cu-MOFs was prepared, which could provide more large surface area for AuNPs enveloping and DNA strand 1 (S1) immobilization. In this sensing process, the released target was available for initiating many of cycles, and the prepared S1-AuNPs@Cu-MOFs was linked to the modified electrode by chain hybridization, which was promising for signal amplification. All electrical signal measurements and chain displacement reactions are carried out on a compatibly designed origami electrochemical device (OECD). In the presence of glucose, AuNPs and Cu-MOFs cooperatively catalyzed the oxidation of glucose, resulting in the wide linear detection range from 1.0fM to 10nM and the detection limit of 0.35fM for miRNA-155 with extremely high sensitivity. As we expect, the newly designed biosensor was successfully applied to the detection of miRNA-155 in serum samples from healthy people to cancer patients. Therefore, this proposed method could provide a promising and safe pathway for sensitive detection of miRNAs in clinical applications.
The estimation of efficiency of industry-specific exports is very important to find exports' gap and to frame exports promotion policy for targeted industry. This study attempts to investigate the ...main determinants of chemical products' exports of Pakistan with 62 trading partners by applying Stochastic Frontier Analysis (SFA) on an augmented gravity model for a period 1995-2015. The results corroborate that chemical products' exports follow gravity patterns. This study finds a negative and significant impact of import tariff on exports of chemical products while the positive impact of devaluation has been observed. Further, the estimations also take into account the impact of Preferential Trade Agreements (PTA), colonial links, common language, political disputes and contiguity by incorporating dummy variable for each variable and the expected positive effects are found except an insignificant effect of Contiguity. Further, the negative impact of political disputes is observed. The exports' efficiency analyses reveal that Pakistan's chemical exports are well below the optimal level and there exists a huge untapped exports' potential with its neighboring, Middle Eastern and European countries.
In frequency‐hopping (FH) communication systems, frequency‐hopping sequences (FHSs) determine systems' performance. For the quasi‐synchronous FH communication systems, no‐hit‐zone (NHZ) frequency ...sequences are good at preventing multi‐path interferences. If the two neighbouring frequency components of an FHS have enough gap, the FH communication system's anti‐interference ability will be significantly improved. Here, a Chinese remainder theorem‐based construction of optimal NHZ‐FHS sets with wide gap is proposed.
One-dimensional PtPd porous nanorods (PtPd PNRs) were successfully synthesized through a bromide-induced galvanic replacement reaction between Pd nanowires and K2PtCl6. The PtPd PNRs were porous and ...alloy-structured with Pt/Pd atomic ratio up to 1:1 which were demonstrated by spectroscopic methods. We had also proved that the nanorods could function as peroxidase mimetic for the detection of H2O2, with the detection limit of 8.6nM and the linear range from 20nM to 50mM. The result demonstrated that PtPd PNRs exhibited much higher affinity to H2O2 over other peroxidase mimetics due to synergistically integrating highly catalytic activity of two metals. On the basis of the peroxidase-like activity, the PtPd PNRs were used as a signal transducer to develop a novel and simple colorimetric method for the study of the flux of H2O2 released from living cell. By using 3,3,5,5-tetramethylbenzidine as substrate, the H2O2 concentration could be distinguished by naked-eye observation without any instrumentation or complicated design. The method developed a new platform for a reliable collection of information on cellular reactive oxygen species release. And the nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine.
•The PtPd PNRs were porous and alloy-structured and showed much higher affinity to H2O2.•Colorimetric method for the flux of H2O2 release from living cell was developed using PtPd PNRs as a peroxidase mimetic.•The PtPd PNRs have good stability, and fine biocompatibility which can greatly overcome the intrinsic shortcomings.
For the communication systems, no‐hit‐zone (NHZ) frequency hopping sequences have good anti‐interference performance. However, the system's time delay may be out of the NHZ. In this situation, the ...maximum Hamming correlation is needed to be taken into consideration. When the maximum Hamming correlation of an optimal NHZ‐FHS set is minimal, the NHZ‐FHSs will be called strong NHZ‐FHSs. It is also hoped that FHSs have a wide gap property to resist the enemy's intentional interferences. In this letter, a tighter bound for optimal NHZ‐FHSs' maximum Hamming correlation is proposed and an optimal strong NHZ‐FHS set is constructed with widegap.
MicroRNAs (miRNAs) play significant roles in a diverse range of biological progress and have been regarded as biomarkers and therapeutic targets in cancer treatment. Sensitive and accurate detection ...of miRNAs is crucial for better understanding their roles in cancer cells and further validating their function in clinical diagnosis. Here, we developed a stable, sensitive, and specific miRNAs detection method on the basis of cooperative amplification combining with the graphene oxide (GO) fluorescence switch-based circular exponential amplification and the multimolecules labeling of SYBR Green I (SG). First, the target miRNA is adsorbed on the surface of GO, which can protect the miRNA from enzyme digest. Next, the miRNA hybridizes with a partial hairpin probe and then acts as a primer to initiate a strand displacement reaction to form a complete duplex. Finally, under the action of nicking enzyme, universal DNA fragments are released and used as triggers to initiate next reaction cycle, constituting a new circular exponential amplification. In the proposed strategy, a small amount of target miRNA can be converted to a large number of stable DNA triggers, leading to a remarkable amplification for the target. Moreover, compared with labeling with a 1:1 stoichiometric ratio, multimolecules binding of intercalating dye SG to double-stranded DNA (dsDNA) can induce significant enhancement of fluorescence signal and further improve the detection sensitivity. The extraordinary fluorescence quenching of GO used here guarantees the high signal-to-noise ratio. Due to the protection for target miRNA by GO, the cooperative amplification, and low fluorescence background, sensitive and accurate detection of miRNAs has been achieved. The strategy proposed here will offer a new approach for reliable quantification of miRNAs in medical research and early clinical diagnostics.
In this paper, a padlock probe-based exponential rolling circle amplification (P-ERCA) assay is developed for highly specific and sensitive detection of microRNA (miRNA). The padlock probe is ...composed of a hybridization sequence to miRNA and a nicking site for nicking endonuclease. Using the miRNA as a template, specific ligation to the padlock probe and linear rolling circle reaction (LRCA) are achieved under isothermal conditions. After multiple nicking reactions, many copies of short DNA products are successively produced and then used as triggers in next circle amplification. Thus, a small amount of miRNAs are converted to a large number of triggers to initiate the rolling circle amplification reaction, and circular exponential signal amplification is achieved. This padlock probe-based exponential rolling circle amplification assay exhibits a remarkable sensitivity of 0.24 zmol using optimized sequences of the padlock probe. The target-dependent circularization of the padlock probe and the ligation reaction could improve the specificity effectively, leading to single–nucleotide difference discrimination between miRNA family members. The miRNA analysis in human lung cells was performed with this method. The result indicates this highly sensitive P-ERCA strategy will become a promising miRNA quantification method in early clinical diagnostics.
•The method can realize the simultaneous detection of two kinds of mutations.•The collection of saliva sample is convenient and painless for patients.•The whole process of modification is relatively ...simple, less time consuming.
In this paper, a microfluidic paper-based electrochemical DNA biosensor was constructed for sensitive detection of EGFR mutations in patients with saliva. In order to achieve the purpose of detection, oligonucleotides were modified on the electrode surface, and the outputs of the electrochemical signal were gained by analyzing DNA hybridization reaction, after that, the horseradish peroxidase (HRP) recognized the indicator labeled on DNA and exhibited excellent electrocatalytic behavior to H2O2, bringing the rapid enhancement of current response. Under optimum conditions, the as-prepared biosensor showed a good linear relationship between the current value and logarithm of the target DNA concentration ranging from 0.5nM to 500.0nM and a detection limit as low as 0.167nM. Meanwhile, the DNA biosensor emerged good stability and high specificity in distinguishing single nucleotide polymorphism of target DNA. This work not only opened a different horizon for investigating biomarker in biological fluids but also offered a promising and reliable method in biosensing and clinical diagnosis in general.
Efficient apoptotic cell clearance and induction of immunologic tolerance is a critical mechanism preventing autoimmunity and associated pathology. Our laboratory has reported that apoptotic cells ...induce tolerance by a mechanism dependent on the tryptophan catabolizing enzyme indoleamine 2,3 dioxygenase 1 (IDO1) in splenic macrophages (MΦ). The metabolic-stress sensing protein kinase GCN2 is a primary downstream effector of IDO1; thus, we tested its role in apoptotic cell-driven immune suppression. In vitro, expression of IDO1 in MΦs significantly enhanced apoptotic cell-driven IL-10 and suppressed IL-12 production in a GCN2-dependent mechanism. Suppression of IL-12 protein production was due to attenuation of IL-12 mRNA association with polyribosomes inhibiting translation while IL-10 mRNA association with polyribosomes was not affected. In vivo, apoptotic cell challenge drove a rapid, GCN2-dependent stress response in splenic MΦs with increased IL-10 and TGF-β production, whereas myeloid-specific deletion of GCN2 abrogated regulatory cytokine production with provocation of inflammatory T-cell responses to apoptotic cell antigens and failure of long-tolerance induction. Consistent with a role in prevention of apoptotic cell driven autoreactivity, myeloid deletion of GCN2 in lupus-prone mice resulted in increased immune cell activation, humoral autoimmunity, renal pathology, and mortality. In contrast, activation of GCN2 with an agonist significantly reduced anti-DNA autoantibodies and protected mice from disease. Thus, this study implicates a key role for GCN2 signals in regulating the tolerogenic response to apoptotic cells and limiting autoimmunity.
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