Login In
2019 Volume 47 Issue 5
2019, 47(5): 643-651
doi: 10.19756/j.issn.0253-3820.181464
Abstract:
Due to the limitation of optical diffraction, traditional optical microscopes have insufficient resolution to observe subcellular microstructures. Super-resolution microscopy, awarded the Nobel Prize in Chemistry in 2014, has been extensively used in single-molecule imaging of microstructures. As a new super-resolution microscope, expansion microscope has the advantages of short imaging time and can mark dense biological macromolecules. This review describes the imaging principles and characteristics of expansion microscope, and reviews its applications in subcellular structures, neurobiology and other fields.
Due to the limitation of optical diffraction, traditional optical microscopes have insufficient resolution to observe subcellular microstructures. Super-resolution microscopy, awarded the Nobel Prize in Chemistry in 2014, has been extensively used in single-molecule imaging of microstructures. As a new super-resolution microscope, expansion microscope has the advantages of short imaging time and can mark dense biological macromolecules. This review describes the imaging principles and characteristics of expansion microscope, and reviews its applications in subcellular structures, neurobiology and other fields.
2019, 47(5): 652-660
doi: 10.19756/j.issn.0253-3820.181659
Abstract:
To solve the problems of low accuracy and poor reliability of the citrus Huanglongbing identification model, a method of Citrus Huanglongbing identification based on Contractive auto-encoder combined extreme learning machine (CAE-ELM) was proposed. To reduce the running time and improve the stability and classification ability of the model, extreme learning machine was used to replace the Softmax of Contractive auto-encoder top layer and reverse fine-tuning stage. Among them, the Contractive auto-encoding realized the extraction of deep features of the samples, and the extreme learning machine realized the identification. To evaluate the performance of CAE-ELM model, experiments were carried out using near infrared spectroscopy data of citrus leaves with different proportions as training sets. Meanwhile, summation wavelet extreme learning machine (SWELM), ELM, support vector machine (SVM), stacked denoising auto-encoder (SDAE), back propagation (BP) and CAE were used as comparative methods. In the identification experiment of citrus Huanglongbing, CAE-ELM maintained the highest classification accuracy no matter how the training sets change. Especially, when the ratio of training sets and test sets was 1080/165, the classification accuracy reached 100.00. At the same time, CAE-ELM model trained faster than SDAE, CAE and BP, but slower than SVM, ELM and SWELM. The results showed that the CAE-ELM model could be used to accurately identify the citrus Huanglongbing, with good robustness and scalability.
To solve the problems of low accuracy and poor reliability of the citrus Huanglongbing identification model, a method of Citrus Huanglongbing identification based on Contractive auto-encoder combined extreme learning machine (CAE-ELM) was proposed. To reduce the running time and improve the stability and classification ability of the model, extreme learning machine was used to replace the Softmax of Contractive auto-encoder top layer and reverse fine-tuning stage. Among them, the Contractive auto-encoding realized the extraction of deep features of the samples, and the extreme learning machine realized the identification. To evaluate the performance of CAE-ELM model, experiments were carried out using near infrared spectroscopy data of citrus leaves with different proportions as training sets. Meanwhile, summation wavelet extreme learning machine (SWELM), ELM, support vector machine (SVM), stacked denoising auto-encoder (SDAE), back propagation (BP) and CAE were used as comparative methods. In the identification experiment of citrus Huanglongbing, CAE-ELM maintained the highest classification accuracy no matter how the training sets change. Especially, when the ratio of training sets and test sets was 1080/165, the classification accuracy reached 100.00. At the same time, CAE-ELM model trained faster than SDAE, CAE and BP, but slower than SVM, ELM and SWELM. The results showed that the CAE-ELM model could be used to accurately identify the citrus Huanglongbing, with good robustness and scalability.
2019, 47(5): 661-668
doi: 10.19756/j.issn.0253-3820.181800
Abstract:
A microfluidic device integrated with a microchannel stacked by two kinds of microbeads with different sizes and a capillary microchannel array was designed and fabricated. When whole blood sample flowed through these channels, blood cells were filtered and adsorbed by the stacked microbeads, and plasma could be separated rapidly. The microbeads were introduced into the channel by negative pressure and thus stacked compactly. Protein blocking solution was used to improve the hydrophilicity of the bead surface. Then the microchip was dried and cooled before 20 μL blood was dropped in the inlet. Driven by capillary force, the blood proceeded in the channel. The influences of microbeads with different sizes and a locally widened microchannel were investigated. Experimental results showed that, when microbeads with 10 μm in diameter were filled in the locally widened microchannel, the separation rate of plasma was the fastest. The collection rate of plasma could reach up to 0.16 μL/min in this case, which could meet the requirement of most clinical applications. On the chip device, collected plasma was used to carry out the agglutination test, and the blood group could be determined quickly, which verified the usefulness of this method.
A microfluidic device integrated with a microchannel stacked by two kinds of microbeads with different sizes and a capillary microchannel array was designed and fabricated. When whole blood sample flowed through these channels, blood cells were filtered and adsorbed by the stacked microbeads, and plasma could be separated rapidly. The microbeads were introduced into the channel by negative pressure and thus stacked compactly. Protein blocking solution was used to improve the hydrophilicity of the bead surface. Then the microchip was dried and cooled before 20 μL blood was dropped in the inlet. Driven by capillary force, the blood proceeded in the channel. The influences of microbeads with different sizes and a locally widened microchannel were investigated. Experimental results showed that, when microbeads with 10 μm in diameter were filled in the locally widened microchannel, the separation rate of plasma was the fastest. The collection rate of plasma could reach up to 0.16 μL/min in this case, which could meet the requirement of most clinical applications. On the chip device, collected plasma was used to carry out the agglutination test, and the blood group could be determined quickly, which verified the usefulness of this method.
2019, 47(5): 669-677
doi: 10.19756/j.issn.0253-3820.181775
Abstract:
Nuclear magnetic resonance (NMR)-based metabonomics was applied to analyze the alterations of fecal metabolites induced by Euphorbia fischeriana Steud (E. fischeriana). A total of 36 SPF male Sprague-Dawley rats were randomly divided into three groups. The administered groups were intraperitoneally injected with different dosages of the extract, while the control group was given the same volume of normal saline containing 3% Tween 80. Rats were administered once a day for 15 consecutive days and withdrawal period lasted for 15 days, and the fecal samples of rats in each group were collected. NMR technology was applied to analyze the fecal samples of rats. The obtained 1H-NMR data were subjected to multivariate statistical analysis to select the altered endogenous metabolites in rat feces, and student test followed by multivariate statistical analysis to obtain the statistically significant biomarkers. Consequently, the metabolic signature of feces exhibited increased levels of glucose and butyrate, together with decreased levels of leucine, alanine, lysine, glutamate, methionine, aspartate, trimethylamine, dimethylamine, phenylalanine, and uracil in E. fischeriana extract administered groups. It could be seen that the significant altered metabolites associated with the metabolism of intestinal flora were futher induced disturbance in amino acid metabolism, short-chain fatty acids and glucose metabolism. The results provided experimental evidence to elucidate toxicity of E. fischeriana.
Nuclear magnetic resonance (NMR)-based metabonomics was applied to analyze the alterations of fecal metabolites induced by Euphorbia fischeriana Steud (E. fischeriana). A total of 36 SPF male Sprague-Dawley rats were randomly divided into three groups. The administered groups were intraperitoneally injected with different dosages of the extract, while the control group was given the same volume of normal saline containing 3% Tween 80. Rats were administered once a day for 15 consecutive days and withdrawal period lasted for 15 days, and the fecal samples of rats in each group were collected. NMR technology was applied to analyze the fecal samples of rats. The obtained 1H-NMR data were subjected to multivariate statistical analysis to select the altered endogenous metabolites in rat feces, and student test followed by multivariate statistical analysis to obtain the statistically significant biomarkers. Consequently, the metabolic signature of feces exhibited increased levels of glucose and butyrate, together with decreased levels of leucine, alanine, lysine, glutamate, methionine, aspartate, trimethylamine, dimethylamine, phenylalanine, and uracil in E. fischeriana extract administered groups. It could be seen that the significant altered metabolites associated with the metabolism of intestinal flora were futher induced disturbance in amino acid metabolism, short-chain fatty acids and glucose metabolism. The results provided experimental evidence to elucidate toxicity of E. fischeriana.
2019, 47(5): 678-685
doi: 10.19756/j.issn.0253-3820.191045
Abstract:
The early accurate diagnosis is key to the successful treatment of tumours. However, single magnetic resonance imaging (MRI) mode cannot satisfy the high requirement of accurate diagnosis owing to their inherent defects. Herein, we constructed poly(acrylic) acid (PAA)-modified Fe3O4@MnO2 nanoparticles (Fe3O4@MnO2@PAA NPs) as a kind of pH-responsive T1/T2 dual-model MRI guiding photothermal therapy (PTT). Fe3O4 core enabled Fe3O4@MnO2@PAA NPs to weaken T2 signal in clinical MRI examination, and MnO2 nanoshells were able to decompose into paramagnetic manganous ions under the weakly acidic environment of tumours, achieving pH-responsive T1-weighted MRI. Such pH-responsive T1/T2 dual-model CAs with sensitivity and specificity provided more comprehensive information for diagnosis of tumours. Moreover, Fe3O4@MnO2@PAA NPs exhibited excellent absorption in near-infrared (NIR) region, making them as good NIR photothermal agents for PTT. This work presented novel pH-responsive theranostic agents integrated dual-model imaging and PTT functionalities, and demonstrated their potential for stimuli-responsive MRI guided PTT of cancer.
The early accurate diagnosis is key to the successful treatment of tumours. However, single magnetic resonance imaging (MRI) mode cannot satisfy the high requirement of accurate diagnosis owing to their inherent defects. Herein, we constructed poly(acrylic) acid (PAA)-modified Fe3O4@MnO2 nanoparticles (Fe3O4@MnO2@PAA NPs) as a kind of pH-responsive T1/T2 dual-model MRI guiding photothermal therapy (PTT). Fe3O4 core enabled Fe3O4@MnO2@PAA NPs to weaken T2 signal in clinical MRI examination, and MnO2 nanoshells were able to decompose into paramagnetic manganous ions under the weakly acidic environment of tumours, achieving pH-responsive T1-weighted MRI. Such pH-responsive T1/T2 dual-model CAs with sensitivity and specificity provided more comprehensive information for diagnosis of tumours. Moreover, Fe3O4@MnO2@PAA NPs exhibited excellent absorption in near-infrared (NIR) region, making them as good NIR photothermal agents for PTT. This work presented novel pH-responsive theranostic agents integrated dual-model imaging and PTT functionalities, and demonstrated their potential for stimuli-responsive MRI guided PTT of cancer.
2019, 47(5): 686-694
doi: 10.19756/j.issn.0253-3820.181750
Abstract:
The changes of concentrations of O2 and CO2 in the tail gas of fermentation industry reflect some important physiological and metabolic parameters in the fermentation process. Monitoring of the tail gas of fermentation has important significance for guiding the fermentation process. However, traditional monitoring methods are time-consuming with low precision and poor versatility, and are not suitable to monitor fermentation tail gas accurately in real time. In the process mass spectrometry, the traditional 70 eV electron impact ionization source will produce a large number of fragment ions, which may overlap with different substances, thus increasing the difficulty of qualitative analysis and causing inaccurate monitoring results. In order to realize real-time, on-line accurate monitoring of fermentation tail gas, a quadrupole process mass spectrometry based on electron impact ionization was developed for on-line analysis. Through investigation of the relationship between emission current of filament and the electron receiving pole at low ionization energy, the ionization efficiency of the electron impact ionization source under low ionization energy mode was improved, and CO2, O2 and N2 were tested. Experimental results showed that under the conditions including electron energy of 22 eV, electron receiving voltage of 22 V and filament emission current of 20-25 mA, the relative errors of quantitative detection of CO2 with volume fraction of higher than 0.023% and O2 with volume fraction of higher than 0.021% were all less than 1%. The instrument and the developed method had ideal application prospect in the rapid real-time, on-line monitoring of industrial processes.
The changes of concentrations of O2 and CO2 in the tail gas of fermentation industry reflect some important physiological and metabolic parameters in the fermentation process. Monitoring of the tail gas of fermentation has important significance for guiding the fermentation process. However, traditional monitoring methods are time-consuming with low precision and poor versatility, and are not suitable to monitor fermentation tail gas accurately in real time. In the process mass spectrometry, the traditional 70 eV electron impact ionization source will produce a large number of fragment ions, which may overlap with different substances, thus increasing the difficulty of qualitative analysis and causing inaccurate monitoring results. In order to realize real-time, on-line accurate monitoring of fermentation tail gas, a quadrupole process mass spectrometry based on electron impact ionization was developed for on-line analysis. Through investigation of the relationship between emission current of filament and the electron receiving pole at low ionization energy, the ionization efficiency of the electron impact ionization source under low ionization energy mode was improved, and CO2, O2 and N2 were tested. Experimental results showed that under the conditions including electron energy of 22 eV, electron receiving voltage of 22 V and filament emission current of 20-25 mA, the relative errors of quantitative detection of CO2 with volume fraction of higher than 0.023% and O2 with volume fraction of higher than 0.021% were all less than 1%. The instrument and the developed method had ideal application prospect in the rapid real-time, on-line monitoring of industrial processes.
2019, 47(5): 695-701
doi: 10.19756/j.issn.0253-3820.171330
Abstract:
For analysis and identification of binding media used in the polychrome of Qin Shihuang Terracotta and Horses, gas chromatography-mass spectrometry combined with pretreatments such as solid phase extraction, ultrasonic assisted extraction, ion exchange resin purification and microwave-assisted hydrolysis was used for amino acids analysis, fatty acids analysis and saccharides analysis. By comparing the protein amounts, ester amounts and polysaccharide amounts in the samples, it was found that only the protein binding media was used in Terracotta and Horses of Qin Shihuang. The residue of protein was very low (only 0.89‰ in weight). According to the features of hydroxyproline, glycine, glutamic acid and proline in binder and principle component analysis, it could be confirmed that the binder of seven samples were the mixture of animal glue and egg, two samples were the mixture of animal glue and casein, and one sample was the mixture of casein, egg and animal glue. From the analysis results, it was inferred that there might be not strict and consistent regulations about the usage of binding media in Terracotta and Horses in Qin dynasty. And for the Qin Shihuang Terracotta and Horses, the low amount of binding media residue was another important reason of color decoration falling off. So the Terracotta and Horses should be consolidated immediately after excavation.
For analysis and identification of binding media used in the polychrome of Qin Shihuang Terracotta and Horses, gas chromatography-mass spectrometry combined with pretreatments such as solid phase extraction, ultrasonic assisted extraction, ion exchange resin purification and microwave-assisted hydrolysis was used for amino acids analysis, fatty acids analysis and saccharides analysis. By comparing the protein amounts, ester amounts and polysaccharide amounts in the samples, it was found that only the protein binding media was used in Terracotta and Horses of Qin Shihuang. The residue of protein was very low (only 0.89‰ in weight). According to the features of hydroxyproline, glycine, glutamic acid and proline in binder and principle component analysis, it could be confirmed that the binder of seven samples were the mixture of animal glue and egg, two samples were the mixture of animal glue and casein, and one sample was the mixture of casein, egg and animal glue. From the analysis results, it was inferred that there might be not strict and consistent regulations about the usage of binding media in Terracotta and Horses in Qin dynasty. And for the Qin Shihuang Terracotta and Horses, the low amount of binding media residue was another important reason of color decoration falling off. So the Terracotta and Horses should be consolidated immediately after excavation.
2019, 47(5): 702-708
doi: 10.19756/j.issn.0253-3820.191016
Abstract:
Tandem mass spectrometric analysis is one primary function of ion trap mass analyzer. In linear ion trap, this function is conducted by collision induced dissociation (CID), which is realized via applying dipolar excitation voltage on one couple of electrodes, so the CID method is also known as unidirectional ion excitation. In this work, bidirectional resonance excitation method was introduced. By applying dipolar excitation voltage on two couples of electrodes, the ion excitation energy and associated dissociation efficiency of this method were increased. The simulation and experimental results indicated that based on this method, higher ion dissociation efficiency was obtained with different q values and excitation frequencies. Besides, more small fragments could be detected in tandem mass analysis of leucine enkephalin via bidirectional resonance excitation with q=0.352, V=0.5 V0-p, ω=107.93 kHz and t=5 ms, suggesting that the method could effectively decrease low mass cut-off effect and strength ability of ion trap on tandem mass analysis.
Tandem mass spectrometric analysis is one primary function of ion trap mass analyzer. In linear ion trap, this function is conducted by collision induced dissociation (CID), which is realized via applying dipolar excitation voltage on one couple of electrodes, so the CID method is also known as unidirectional ion excitation. In this work, bidirectional resonance excitation method was introduced. By applying dipolar excitation voltage on two couples of electrodes, the ion excitation energy and associated dissociation efficiency of this method were increased. The simulation and experimental results indicated that based on this method, higher ion dissociation efficiency was obtained with different q values and excitation frequencies. Besides, more small fragments could be detected in tandem mass analysis of leucine enkephalin via bidirectional resonance excitation with q=0.352, V=0.5 V0-p, ω=107.93 kHz and t=5 ms, suggesting that the method could effectively decrease low mass cut-off effect and strength ability of ion trap on tandem mass analysis.
2019, 47(5): 709-718
doi: 10.19756/j.issn.0253-3820.181698
Abstract:
An effective, accurate and stable colorimetric detection method for aluminium ion (Al3+) through chelation based on the large-sized gold nanoparticles (AuNPs) asymmetrically modified with polyethylene glycol (PEG) and citrate was developed. Initially, citrate-stabilized AuNPs with different sizes (13 nm, 26 nm, 38 nm) were synthesized to explore the correlation between particle dimensions and detection sensitivity. The detection limit of 38 nm AuNPs was as low as 1 μmol/L by visual observation which demonstrated that sensitivity couold be improved by increasing the particle size. In the following, citrate-stabilized AuNPs were modified on the glass slide, through which some binding sites on the surface of AuNPs were concealed. The stabilizing agent PEG was introduced onto the exposed surface of AuNPs and characterized by laser dynamic scattering instrument (DLS), field-Emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS). The aggregation behavior was further adjusted in an oriented and controllable manner to form oligomers which could remain stable in aqueous solution for a long time. Such an asymmetrical modification could significantly improve the dynamic detection range (1 μmol/L-100 mmol/L), and a linear correction curve (y=0.06485x + 0.60851, R2=0.99) was obtained. Nine common metal ions were also investigated, which exhibited the good selectivity of detection system to Al3+. PEG and citrate modified AuNPs could be applied in the detection of spiked tap water sample.
An effective, accurate and stable colorimetric detection method for aluminium ion (Al3+) through chelation based on the large-sized gold nanoparticles (AuNPs) asymmetrically modified with polyethylene glycol (PEG) and citrate was developed. Initially, citrate-stabilized AuNPs with different sizes (13 nm, 26 nm, 38 nm) were synthesized to explore the correlation between particle dimensions and detection sensitivity. The detection limit of 38 nm AuNPs was as low as 1 μmol/L by visual observation which demonstrated that sensitivity couold be improved by increasing the particle size. In the following, citrate-stabilized AuNPs were modified on the glass slide, through which some binding sites on the surface of AuNPs were concealed. The stabilizing agent PEG was introduced onto the exposed surface of AuNPs and characterized by laser dynamic scattering instrument (DLS), field-Emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy dispersive spectrum (EDS). The aggregation behavior was further adjusted in an oriented and controllable manner to form oligomers which could remain stable in aqueous solution for a long time. Such an asymmetrical modification could significantly improve the dynamic detection range (1 μmol/L-100 mmol/L), and a linear correction curve (y=0.06485x + 0.60851, R2=0.99) was obtained. Nine common metal ions were also investigated, which exhibited the good selectivity of detection system to Al3+. PEG and citrate modified AuNPs could be applied in the detection of spiked tap water sample.
2019, 47(5): 719-724
doi: 10.19756/j.issn.0253-3820.181788
Abstract:
In the research of fuel cells, the development of cathode oxygen reduction electrocatalysts with low cost and high performance to replace platinum based catalyst is a critical path of realizing the commercialization of fuel cell. Carbon nanomaterials supported transition metal macrocyclic compounds have many advantages including low cost, high activity, strong catalytic selectivity, good electrical conductivity and high stability. Herein, the CNT-VB12 composite was prepared based on the Co-Nx center structure of Vitamin B12 (VB12) through high temperature pyrolysis and with VB12 as the active sites precursor and carbon nanotubes as carrier. We characterized the morphology and the composition of the as-prepared composite, and analyzed its electrocatalytic activity, stability, selectivity and the anti-interference performance for oxygen reduction reaction (ORR). The results showed that the CNT-VB12 exhibited high ORR electrocatalytic activity in alkaline electrolyte (0.1 mol/L KOH). The corresponding electron transfer number was calculated to be close to 4, which suggested that the electrocatalyst reduced O2 predominately to H2O. Moreover, the synthesized CNT-VB12 electrocatalyst outperformed commercial Pt/C in terms of better methanol tolerance and stability. All these performance made this CNT-VB12 composite very promising non-precious metal ORR electrocatalyst for practical fuel cell application.
In the research of fuel cells, the development of cathode oxygen reduction electrocatalysts with low cost and high performance to replace platinum based catalyst is a critical path of realizing the commercialization of fuel cell. Carbon nanomaterials supported transition metal macrocyclic compounds have many advantages including low cost, high activity, strong catalytic selectivity, good electrical conductivity and high stability. Herein, the CNT-VB12 composite was prepared based on the Co-Nx center structure of Vitamin B12 (VB12) through high temperature pyrolysis and with VB12 as the active sites precursor and carbon nanotubes as carrier. We characterized the morphology and the composition of the as-prepared composite, and analyzed its electrocatalytic activity, stability, selectivity and the anti-interference performance for oxygen reduction reaction (ORR). The results showed that the CNT-VB12 exhibited high ORR electrocatalytic activity in alkaline electrolyte (0.1 mol/L KOH). The corresponding electron transfer number was calculated to be close to 4, which suggested that the electrocatalyst reduced O2 predominately to H2O. Moreover, the synthesized CNT-VB12 electrocatalyst outperformed commercial Pt/C in terms of better methanol tolerance and stability. All these performance made this CNT-VB12 composite very promising non-precious metal ORR electrocatalyst for practical fuel cell application.
2019, 47(5): 725-730
doi: 10.19756/j.issn.0253-3820.181680
Abstract:
Polyphenols are very important secondary metabolites that affect the aroma types and quality of tobacco. For this purpose, a simple ultrasonic assisted solvent extraction combined with liquid chromatography was developed for rapid determination of polyphenols in tobacco. Multivariate analyses including principal component analysis (PCA), cluster analysis (CA) and discriminant analysis (DA) were employed to provide a visual comparison of three aroma types of tobacco. The first two principal components which explained 67.9% of the total variation showed obvious distinction from principal component score. All samples could be classified into three clusters which corresponded to the three aroma types, and were consistence with an average recognition ability of 90.2% of Fisher's discriminant analysis. In addition, the relationship between polyphenols and geographical origin was also studied, and the results showed their potential relationship. These results demonstrated that polyphenols could be used as the useful variables to characterize the aroma types and geographical origin of tobacco, which might be suitable for monitoring quality of tobacco.
Polyphenols are very important secondary metabolites that affect the aroma types and quality of tobacco. For this purpose, a simple ultrasonic assisted solvent extraction combined with liquid chromatography was developed for rapid determination of polyphenols in tobacco. Multivariate analyses including principal component analysis (PCA), cluster analysis (CA) and discriminant analysis (DA) were employed to provide a visual comparison of three aroma types of tobacco. The first two principal components which explained 67.9% of the total variation showed obvious distinction from principal component score. All samples could be classified into three clusters which corresponded to the three aroma types, and were consistence with an average recognition ability of 90.2% of Fisher's discriminant analysis. In addition, the relationship between polyphenols and geographical origin was also studied, and the results showed their potential relationship. These results demonstrated that polyphenols could be used as the useful variables to characterize the aroma types and geographical origin of tobacco, which might be suitable for monitoring quality of tobacco.
2019, 47(5): 731-738
doi: 10.19756/j.issn.0253-3820.191034
Abstract:
A convenient and green strategy was developed for the synthesis of water-soluble carbon dots (CDs) with blue fluorescence by one-step hydrothermal synthesis method using mandelic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet visible spectroscopy (UV) and fluorescence, respectively. The CDs were quasi spherical nano-particles with perfect monodispersity, and the average size was 2.62 ±0.20 nm. They possessed crystal structures and the distinct lattice spacing was 0.21 nm. Abundant groups like C=C, hydroxyl, carboxylic and amine groups, etc, were linked on the surface of the synthesized CDs. The CDs showed typical excitation-dependent photoluminescent behavior with the maximum excitation and emission wavelengths of 360 nm and 450 nm, respectively. The effects of ionic strength, pH and storage time on the fluorescence intensity of the CDs were slight, which demonstrated the perfect fluorescence stability of the CDs. Based on fluorescence resonance energy transfer (FRET) mechanism between donor CDs and acceptor Mn(Ⅶ), the fluorescence of CDs could be effectively quenched by Mn(Ⅶ). On the basis of this, a method was developed for detection of Mn(Ⅶ). The method showed a linear range of 1-100 μmol/L (i.e., 0.055-5.500 mg/L) with a correlation coefficient (R2) of 0.9986. The limit of detection was 0.04 μmol/L (i.e., 2.20 μg/L), showing excellent sensitivity and selectivity. Due to low toxicity and excellent biocompatibility of CDs, HepG2 cells emitted blue fluorescence after incubated with CDs, and intracellular fluorescence intensities were roughly linear with Mn(Ⅶ) concentration, which enabled the potential applications of CDs in Mn(Ⅶ) biosensing. In brief, the CDs were designed as successful fluorescent sensors for direct determination of Mn(Ⅶ) content in aqueous solution and living cell.
A convenient and green strategy was developed for the synthesis of water-soluble carbon dots (CDs) with blue fluorescence by one-step hydrothermal synthesis method using mandelic acid and proline as carbon precursor and nitrogen dopant, respectively. The synthesized CDs were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet visible spectroscopy (UV) and fluorescence, respectively. The CDs were quasi spherical nano-particles with perfect monodispersity, and the average size was 2.62 ±0.20 nm. They possessed crystal structures and the distinct lattice spacing was 0.21 nm. Abundant groups like C=C, hydroxyl, carboxylic and amine groups, etc, were linked on the surface of the synthesized CDs. The CDs showed typical excitation-dependent photoluminescent behavior with the maximum excitation and emission wavelengths of 360 nm and 450 nm, respectively. The effects of ionic strength, pH and storage time on the fluorescence intensity of the CDs were slight, which demonstrated the perfect fluorescence stability of the CDs. Based on fluorescence resonance energy transfer (FRET) mechanism between donor CDs and acceptor Mn(Ⅶ), the fluorescence of CDs could be effectively quenched by Mn(Ⅶ). On the basis of this, a method was developed for detection of Mn(Ⅶ). The method showed a linear range of 1-100 μmol/L (i.e., 0.055-5.500 mg/L) with a correlation coefficient (R2) of 0.9986. The limit of detection was 0.04 μmol/L (i.e., 2.20 μg/L), showing excellent sensitivity and selectivity. Due to low toxicity and excellent biocompatibility of CDs, HepG2 cells emitted blue fluorescence after incubated with CDs, and intracellular fluorescence intensities were roughly linear with Mn(Ⅶ) concentration, which enabled the potential applications of CDs in Mn(Ⅶ) biosensing. In brief, the CDs were designed as successful fluorescent sensors for direct determination of Mn(Ⅶ) content in aqueous solution and living cell.
2019, 47(5): 739-747
doi: 10.19756/j.issn.0253-3820.181532
Abstract:
A novel electrochemical sensor was prepared by electrodeposition of copper nanoparticles (CuNPs) on a zinc oxide/graphene (ZnO/GO) modified ITO electrode and applied to the determination of kanamycin sulfate (KANA). The morphology of material and modified electrodes was characterized by scanning electron microscope. With optimization of measurement conditions systematically, the result showed that the electrochemical response of KANA on CuNPs/ZnO/GO/ITO electrode was the largest when the number of electrodeposition scanning circles were 40 in 0.15 mol/L PBS (pH=6.5) solution. The mechanism of electrode reaction of KANA involved one electron process, and the effective area (0.482 cm2) of CuNPs/ZnO/GO/ITO electrode was 2.42 times as large as that of a bare ITO electrode. Moreover, the linear response range for determination of KANA was 0.99-30.6 μmol/L, the linear equation was Ipc=-5.183c-4.544×10-6 with the detection limit of 0.31 μmol/L, and the recoveries of standard addition experiments were 97.8%-103.6%. The sensor shows good stability and reproducibility, and can be used to detect kanamycin sulfate in the drug samples.
A novel electrochemical sensor was prepared by electrodeposition of copper nanoparticles (CuNPs) on a zinc oxide/graphene (ZnO/GO) modified ITO electrode and applied to the determination of kanamycin sulfate (KANA). The morphology of material and modified electrodes was characterized by scanning electron microscope. With optimization of measurement conditions systematically, the result showed that the electrochemical response of KANA on CuNPs/ZnO/GO/ITO electrode was the largest when the number of electrodeposition scanning circles were 40 in 0.15 mol/L PBS (pH=6.5) solution. The mechanism of electrode reaction of KANA involved one electron process, and the effective area (0.482 cm2) of CuNPs/ZnO/GO/ITO electrode was 2.42 times as large as that of a bare ITO electrode. Moreover, the linear response range for determination of KANA was 0.99-30.6 μmol/L, the linear equation was Ipc=-5.183c-4.544×10-6 with the detection limit of 0.31 μmol/L, and the recoveries of standard addition experiments were 97.8%-103.6%. The sensor shows good stability and reproducibility, and can be used to detect kanamycin sulfate in the drug samples.
2019, 47(5): 748-755
doi: 10.19756/j.issn.0253-3820.181699
Abstract:
Nitrogen-doped carbon quantum dots (N-CQDs) with good water solubility, pH stability and salt tolerance were synthesized by hydrothermal method (180℃) with Escherichia coli as precursor. The structure of N-CQD was characterized by transmission electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. The results showed that the particle size was uniform with a diameter of 4.1 nm, the dispersibility was good, and the surface contained a large amount of hydrophilic groups. UV-visible absorption and fluorescence spectra were used to study optical properties, and it was found that Fe3+ could selectively quench the N-CQDs fluorescence. In the concentration range of 0.58 nmol/L-100 μmol/L, the quenching degree had a good linear relationship with the concentration of Fe3+ ion. The detection limit was 0.58 nmol/L, and the recoveries were 93.9%-108.7%. At the same time, the interference of pH, salt content and coexistence metal ion on Fe3+ determination was studied. The results showed that the method was especially suitable for selective fluorescent detection of Fe3+ in offshore seawater with high salt content, large range of pH and diverse metal ions.
Nitrogen-doped carbon quantum dots (N-CQDs) with good water solubility, pH stability and salt tolerance were synthesized by hydrothermal method (180℃) with Escherichia coli as precursor. The structure of N-CQD was characterized by transmission electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. The results showed that the particle size was uniform with a diameter of 4.1 nm, the dispersibility was good, and the surface contained a large amount of hydrophilic groups. UV-visible absorption and fluorescence spectra were used to study optical properties, and it was found that Fe3+ could selectively quench the N-CQDs fluorescence. In the concentration range of 0.58 nmol/L-100 μmol/L, the quenching degree had a good linear relationship with the concentration of Fe3+ ion. The detection limit was 0.58 nmol/L, and the recoveries were 93.9%-108.7%. At the same time, the interference of pH, salt content and coexistence metal ion on Fe3+ determination was studied. The results showed that the method was especially suitable for selective fluorescent detection of Fe3+ in offshore seawater with high salt content, large range of pH and diverse metal ions.
2019, 47(5): 756-764
doi: 10.19756/j.issn.0253-3820.191040
Abstract:
An analytical method for determination of 10 kinds of caine-type prohibited ingredients in cosmetics was developed using supramolecular solvent-based dispersive liquid-liquid microextraction followed by ultra-performance liquid chromatography coupled with differential mobility spectrometry-mass spectrometry. The supramolecular solvent was prepared with dodecanol as extraction solvent and tetrahydrofuran as dispersing agent for dispersive liquid-liquid microextraction of cosmetic samples under vortexing. The effects of the composition and amount of supramolecular solvent and vortex time on the extraction efficiency and the separation of isomers by differential mobility spectrometry were systemitically investigated. Results showed that the sample could be effectively extracted by 4 mL of supramolecular solvent consisting of dodecanol and tetrahydrofuran after vortexing for 3 min. Under the optimized conditions including carrier gas, separation voltage and compensation voltage, the isomers of benzocaine and tricaine could be well separated by differential mobility spectrometry for qualitative confirmation and quantitative determination, which could hardly be chromatographically separated. The 10 kinds of caine-type compounds exhibited good linearity in their respective concentration ranges, with correlation coefficients of better than 0.99. The limits of detection and quantitation were 0.2-8.0 μg/kg and 0.4-20.0 μg/kg, respectively. The average recoveries at low, medium and high spiked levels ranged from 70.7% to 94.7% with relative standard deviations of 1.2% to 12.7% (n=6). The method is simple, rapid, efficient, and is suitable for the simultaneous determination of the 10 kinds of caine-type prohibited ingredients in cosmetics.
An analytical method for determination of 10 kinds of caine-type prohibited ingredients in cosmetics was developed using supramolecular solvent-based dispersive liquid-liquid microextraction followed by ultra-performance liquid chromatography coupled with differential mobility spectrometry-mass spectrometry. The supramolecular solvent was prepared with dodecanol as extraction solvent and tetrahydrofuran as dispersing agent for dispersive liquid-liquid microextraction of cosmetic samples under vortexing. The effects of the composition and amount of supramolecular solvent and vortex time on the extraction efficiency and the separation of isomers by differential mobility spectrometry were systemitically investigated. Results showed that the sample could be effectively extracted by 4 mL of supramolecular solvent consisting of dodecanol and tetrahydrofuran after vortexing for 3 min. Under the optimized conditions including carrier gas, separation voltage and compensation voltage, the isomers of benzocaine and tricaine could be well separated by differential mobility spectrometry for qualitative confirmation and quantitative determination, which could hardly be chromatographically separated. The 10 kinds of caine-type compounds exhibited good linearity in their respective concentration ranges, with correlation coefficients of better than 0.99. The limits of detection and quantitation were 0.2-8.0 μg/kg and 0.4-20.0 μg/kg, respectively. The average recoveries at low, medium and high spiked levels ranged from 70.7% to 94.7% with relative standard deviations of 1.2% to 12.7% (n=6). The method is simple, rapid, efficient, and is suitable for the simultaneous determination of the 10 kinds of caine-type prohibited ingredients in cosmetics.
2019, 47(5): 765-771
doi: 10.19756/j.issn.0253-3820.181704
Abstract:
Potassium is an indispensable element of the human body. The disorder of potassium concentration is one of the most common electrolyte disorders in the clinic. The imbalance of potassium concentration makes the myocardial contraction ability abnormal, causing arrhythmia, leading to shock and even death. Therefore, real-time and accurate detection of blood potassium is extremely important for saving lives. In this paper, a 2D MnO2 nanosheet was used as an ion-electron conversion layer (solid contact layer) to construct an all solid-state Potassium ion selective electrode whose membrane based on a glassy carbon electrode and a polymer membrane containing valinomycin as an ionophore. The results showed that MnO2 nanosheets had the characteristics of rapid charge and discharge, and their use as ion-electron transducing layers could effectively improve the ion-electron conversion efficiency and reduce the resistance of potassium ion selective electrodes in water layer testing and anti-interference experiments. It exhibited good performance and improved electrode potential response speed and stability. The linear response range of the all-solid potassium ion selective electrode was 1.0×10-5-1.0×10-2 mol/L, and the detection limit was 6.3×10-6 mol/L. Rapid and accurate detection of serum potassium was achieved using this all-solid-states potassium ion selective electrode.
Potassium is an indispensable element of the human body. The disorder of potassium concentration is one of the most common electrolyte disorders in the clinic. The imbalance of potassium concentration makes the myocardial contraction ability abnormal, causing arrhythmia, leading to shock and even death. Therefore, real-time and accurate detection of blood potassium is extremely important for saving lives. In this paper, a 2D MnO2 nanosheet was used as an ion-electron conversion layer (solid contact layer) to construct an all solid-state Potassium ion selective electrode whose membrane based on a glassy carbon electrode and a polymer membrane containing valinomycin as an ionophore. The results showed that MnO2 nanosheets had the characteristics of rapid charge and discharge, and their use as ion-electron transducing layers could effectively improve the ion-electron conversion efficiency and reduce the resistance of potassium ion selective electrodes in water layer testing and anti-interference experiments. It exhibited good performance and improved electrode potential response speed and stability. The linear response range of the all-solid potassium ion selective electrode was 1.0×10-5-1.0×10-2 mol/L, and the detection limit was 6.3×10-6 mol/L. Rapid and accurate detection of serum potassium was achieved using this all-solid-states potassium ion selective electrode.
2019, 47(5): 772-778
doi: 10.19756/j.issn.0253-3820.191009
Abstract:
A library of Nanoparticles hydrogel (NPs) was synthesized by emulsion polymerization method in aqueous solution. The feasibility of NPs applying to the DNA fragments separation in capillary electrophoresis was investigated based on the dynamic coating method. The diameters of the particles were proved uniform with good mono-dispersion by dynamic light scattering method. The experimental results indicated that three factors had an effect on the DNA separation, including the amount of monomer, the particle size and the concentration of NPs in capillary electrophoresis buffer solution. NPs exhibited the best performance in DNA separation when the monomer molar ratios were optimized to N-isopropylacrylamide (87%), hydroxyethylacrylate (8%), acrylic acid (4%) and N,N'-methylene bisacrylamide(1%). Meanwhile, the particle size of the prepared NPs could be changed by changing the amount of the surfactant sodium dodecyl sulfate (SDS). A completely separation among the three different length of DNA frament samples (20 nt, 50 nt and 80 nt) could be obtained when 8.0 mg/mL NPs (400 nm) were added in the TG buffer solution (25 mmol/L Tris, 192 mmol/L glycine, at pH 8.3) in the capillary electrophoresis study. These hydrogel nanoparticles showed potential capability in DNA separation due to their well-developed crosslinking network structure.
A library of Nanoparticles hydrogel (NPs) was synthesized by emulsion polymerization method in aqueous solution. The feasibility of NPs applying to the DNA fragments separation in capillary electrophoresis was investigated based on the dynamic coating method. The diameters of the particles were proved uniform with good mono-dispersion by dynamic light scattering method. The experimental results indicated that three factors had an effect on the DNA separation, including the amount of monomer, the particle size and the concentration of NPs in capillary electrophoresis buffer solution. NPs exhibited the best performance in DNA separation when the monomer molar ratios were optimized to N-isopropylacrylamide (87%), hydroxyethylacrylate (8%), acrylic acid (4%) and N,N'-methylene bisacrylamide(1%). Meanwhile, the particle size of the prepared NPs could be changed by changing the amount of the surfactant sodium dodecyl sulfate (SDS). A completely separation among the three different length of DNA frament samples (20 nt, 50 nt and 80 nt) could be obtained when 8.0 mg/mL NPs (400 nm) were added in the TG buffer solution (25 mmol/L Tris, 192 mmol/L glycine, at pH 8.3) in the capillary electrophoresis study. These hydrogel nanoparticles showed potential capability in DNA separation due to their well-developed crosslinking network structure.
2019, 47(5): 779-784
doi: 10.19756/j.issn.0253-3820.181734
Abstract:
Broadband microwave spectrometers based on the chirped pulse, a linear frequency modulation technology, have become indispensable experimental instruments for many rotational spectroscopy laboratories, with significant efficiency advantage in measuring molecular rotational transitions compared with traditional narrow-band spectrometers. In this work, a broadband chirped-pulse Fourier transform microwave spectrometer with frequency coverage of 1-18 GHz was designed and constructed with a single scan bandwidth about 2 GHz. The homodyne detection scheme was adopted along with the multiple FID technique applied. Using OCS molecules diluted to 0.5% in argon gas as the standard sample, rotational transitions of 6 OCS isotopologues were successfully detected by the present broadband microwave spectrometer. On this basis, the rotational spectrum of Ar-OCS van der Waals dimer was measured, and the reaction of tertiary-butyl alcohol with HCl was monitored in real time as well.
Broadband microwave spectrometers based on the chirped pulse, a linear frequency modulation technology, have become indispensable experimental instruments for many rotational spectroscopy laboratories, with significant efficiency advantage in measuring molecular rotational transitions compared with traditional narrow-band spectrometers. In this work, a broadband chirped-pulse Fourier transform microwave spectrometer with frequency coverage of 1-18 GHz was designed and constructed with a single scan bandwidth about 2 GHz. The homodyne detection scheme was adopted along with the multiple FID technique applied. Using OCS molecules diluted to 0.5% in argon gas as the standard sample, rotational transitions of 6 OCS isotopologues were successfully detected by the present broadband microwave spectrometer. On this basis, the rotational spectrum of Ar-OCS van der Waals dimer was measured, and the reaction of tertiary-butyl alcohol with HCl was monitored in real time as well.
2019, 47(5): 785-793
doi: 10.19756/j.issn.0253-3820.181721
Abstract:
To solve the problem of low signal-to-noise ratio in detection of rice amylose content by long wavelength near infrared diffuse transmission spectroscopy, 3 spectral data acquisition systems were built. In the wavelength range of 900-1700 nm, the original spectrum curves of 62 kinds of rice samples before and after light compensation were collected, normalized, smoothed by SG, and treated by Savitzky-Golay derivative convolution. After that, partial least squares regression modeling was performed for amylose content analysis of rice, by which the light diffuse transmission spectrum curves of rice sample with different thicknesses before and after light compensation were comparatively investigated, and the physical and chemical standard values before and after light compensation were subjected to significant analysis. The results showed that the prediction model was improved with the increase of sample thickness before light compensation, but with the increase of sample thickness, the transmitted light intensity was weakened, the signal-to-noise ratio was decreased, the noise was increased, and the model modeling effect became worse. When the sample thickness was 9 mm, the prediction model of near-infrared diffuse transmission spectroscopy for rice amylose had the best result. Under this condition, the correlation coefficients of correction set (RC) and prediction set (RP) were 0.9103 and 0.9049, respectively, and their root mean square errors (RMSEC and RMSEP) were 1.4209% and 1.5654%, respectively. After the optical compensation, the signal-to-noise ratio of near-infrared diffuse transmission spectrum curve of the rice sample was significantly improved, especially the spectral absorption near 1203 nm and 1465 nm after the pretreatment, and the prediction model accuracy under different sample thicknesses was also significantly improved. When the thickness of rice samples was 9 mm, the effect of optical compensation prediction model for amylose detection was the best. The correlation coefficient of model correction set (RC) and prediction set (RP) were increased to 0.9654 and 0.9577, respectively, and their root mean square errors (RMSEC and RMSEP) were reduced to 0.8902% and 1.4261%, respectively. In addition, the significance of the light compensation was reduced compared with that before the light compensation, and the correlation coefficient and error of the model were improved compared with other methods. Finally, 20 samples were selected for external testing of the optical compensation model with a sample thickness of 9 mm, the model correlation coefficient (RV) was 0.9363, the root mean square error (RMSEV) was 1.4139%, and the RPD value was 2.85. The results showed that the light compensation method could effectively solve the problem of low signal-to-noise ratio caused by relatively weak penetrating power of diffuse transmission spectrum in detection of rice amylose by long wavelength near infrared spectrometry, which improved the accuracy of forecasting model, realized the rapid and nondestructive testing of rice amylose content, and provided technical support for rice quality detection.
To solve the problem of low signal-to-noise ratio in detection of rice amylose content by long wavelength near infrared diffuse transmission spectroscopy, 3 spectral data acquisition systems were built. In the wavelength range of 900-1700 nm, the original spectrum curves of 62 kinds of rice samples before and after light compensation were collected, normalized, smoothed by SG, and treated by Savitzky-Golay derivative convolution. After that, partial least squares regression modeling was performed for amylose content analysis of rice, by which the light diffuse transmission spectrum curves of rice sample with different thicknesses before and after light compensation were comparatively investigated, and the physical and chemical standard values before and after light compensation were subjected to significant analysis. The results showed that the prediction model was improved with the increase of sample thickness before light compensation, but with the increase of sample thickness, the transmitted light intensity was weakened, the signal-to-noise ratio was decreased, the noise was increased, and the model modeling effect became worse. When the sample thickness was 9 mm, the prediction model of near-infrared diffuse transmission spectroscopy for rice amylose had the best result. Under this condition, the correlation coefficients of correction set (RC) and prediction set (RP) were 0.9103 and 0.9049, respectively, and their root mean square errors (RMSEC and RMSEP) were 1.4209% and 1.5654%, respectively. After the optical compensation, the signal-to-noise ratio of near-infrared diffuse transmission spectrum curve of the rice sample was significantly improved, especially the spectral absorption near 1203 nm and 1465 nm after the pretreatment, and the prediction model accuracy under different sample thicknesses was also significantly improved. When the thickness of rice samples was 9 mm, the effect of optical compensation prediction model for amylose detection was the best. The correlation coefficient of model correction set (RC) and prediction set (RP) were increased to 0.9654 and 0.9577, respectively, and their root mean square errors (RMSEC and RMSEP) were reduced to 0.8902% and 1.4261%, respectively. In addition, the significance of the light compensation was reduced compared with that before the light compensation, and the correlation coefficient and error of the model were improved compared with other methods. Finally, 20 samples were selected for external testing of the optical compensation model with a sample thickness of 9 mm, the model correlation coefficient (RV) was 0.9363, the root mean square error (RMSEV) was 1.4139%, and the RPD value was 2.85. The results showed that the light compensation method could effectively solve the problem of low signal-to-noise ratio caused by relatively weak penetrating power of diffuse transmission spectrum in detection of rice amylose by long wavelength near infrared spectrometry, which improved the accuracy of forecasting model, realized the rapid and nondestructive testing of rice amylose content, and provided technical support for rice quality detection.
