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With cancer seriously hampering the increasing life expectancy of people, developing an instant diagnostic method has become an urgent objective. In this work, we developed a label-free laser-induced breakdown spectroscopy (LIBS) method for high-throughput recognition of tumor cells. LIBS spectra were straightly collected from cells dropped on a silicon substrate and built into a deep learning model for simultaneous classification of various cancers. To interpret the result of the deep learning algorithm, gradient-weighted class activation mapping was utilized to a one-dimensional convolution neural network (1D-CNN), and the saliency maps thus obtained amplified the differences between the spectra of cell lines. Overall results showed that the 1D-CNN algorithms achieved a mean sensitivity of 94.00%, a mean specificity of 98.47%, and a mean accuracy of 97.56%. Thus, the proposed method performed satisfactorily and is seen as an interpretable classification process for cancer cell lines.

Quantum dots (QDs), with unique and tunable optical properties, have been widely used in many fields closely related to our daily lives, such as biomedical application and electronic products. Therefore, the potential toxicity of QDs on the human health should be understood. Autophagy plays an important role in cell survival and death. Endoplasmic reticulum autophagy (ER-phagy), a selective autophagy that degrades ER, responds to the accumulation of misfolded proteins and ER stress. Although many reports have revealed that autophagy can be disturbed by cadmium telluride (CdTe)-QDs and other nanomaterials, there are still lack more detailed researches to illustrate the function of autophagy in CdTe-QDs-treated cells, and the function of ER-phagy in CdTe-QDs-treated cells remains to be illustrated. On the basis of transcriptome analysis, we explored the effect of CdTe-QDs on Saccharomyces cerevisiae and first illustrated that both of autophagy and ER-phagy were protective mechanisms in CdTe-QDs-treated cells. It was found that CdTe-QDs inhibited the proliferation of yeast cells, disrupted homeostasis of cells, membrane integrity, and metabolism process. All of these can be reasons of the reduction of cell viability. The abolishment of autophagy and ER-phagy reduce the cell survival, indicating both of them are cell protective mechanisms against CdTe-QDs toxicity in yeast cells. Therefore, our data are significant for the application of CdTe-QDs and provide precious information for understanding of nanomaterials-related ER-phagy.

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The development of rapid and sensitive detection methods for pathogenic bacteria is crucial for the therapy and prevention of related diseases. However, the rapid and ultrasensitive assays are difficult to be realized simultaneously. To solve the problem, a sandwich method based on Ω-shaped fiber optic localized surface resonance (Ω-FOLSPR) was constructed, where poly adenine-tailed aptamer (PolyA-apt) and SH modified gold nanoparticles tags (AuNPs tags) were chosen as the capturing aptamer and amplifying tags, respectively. The small AuNPs were modified on the surface of fiber-optic (FO) rapidly, which saved the preparation time. Then, the PolyA-apt was modified on the AuNPs surface to capture the bacteria effectively due to its ability to adjust the density and conformation of aptamer on the AuNPs surface. Finally, the large AuNPs tags were used to generate intense signal enhancement. It is found that the sandwich method enables the unique characteristic of a time-dependent sensitivity enhancement. Specifically, the LOD of 108.0 CFU/mL and 7.4 CFU/mL was achieved with the analysis time of 10 min and 100 min, respectively. Besides, the Ω-FOLSPR sensor exhibits excellent selectivity against the other bacteria and good performance for detecting the spiked and natural samples. This sandwich method provides a time-flexible strategy due to the combination of effective signal amplification and real-time analysis for bacterial detection, displaying great potential for practical bacterial detection.

Signal amplification is critical to achieving sensitive biosensing, but complex strategies often bring problems like system instability, false positive, or narrow target spectrum. Here, a self-extending DNA-mediated isothermal amplification (SEIA) system with simple reaction components is introduced to achieve rapid, robust, and significant signal amplification. In SEIA, based on spontaneous refolding of specific DNA domains and using the previous generation product as a template, a DNA strand can extend continuously in an approximate exponential growth pattern, which was accurately predicted by our formula and well supported by AFM results. Based on a set of proof-of-concept experiments, it was proved that the SEIA system can output different signals and flexibly integrate various functional nucleic acids, which makes it suitable for different scenarios and realizes broad-spectrum target detection. Taking into account the advantages of simplicity, flexibility, and efficiency, the SEIA system as an independent signal amplification module will enrich the toolbox of biosensing design.

In this study, an innovative rapid detection technology for quickly screening and quantifying organophosphorus pesticides (OPPs) in vegetables was developed based on ambient micro-fabricated glow discharge plasma desorption/ionization mass spectrometry (MFGDP-MS), where Fe

Sensitive and efficient monitoring of food-borne bacteria is of great importance for food safety control. Herein, a novel biosensor for highly sensitive detection of

Rapid detection and efficient removal of heavy metal ions from environmental water are of considerable importance to tackle the water pollution problem. In this work, a simple but efficient strategy named metal-chelate induced nanoparticle aggregation enhanced laser-induced breakdown spectroscopy (MINAELIBS) was proposed for signal enhancement aiming at ultra-sensitive detection of trace levels of metal elements in liquid samples. Unlike the surface contact approach previously reported in the literature, direct mixing of gold nanoparticles (AuNPs) and metal chelates increased the contact area, adhesion force, and uniformity between analytes and AuNPs. As a result, under the optimal conditions, the limits of detection (LODs) of Cd, Cu, Ag, Pb, and Cr were 4.6, 1.5, 3.4, 3.5, and 3.5 ng mL−1, respectively. The LODs of target elements were notably 7–10 times lower than those of chelating reagent enrichment alone and 3–4 orders of magnitude lower compared to traditional LIBS methods, which demonstrates the feasibility of MINAELIBS in analysis of liquid samples at the ppb level. Application of AuNPs for high-performance signal enhancement has undoubtedly pushed the method sensitivity of traditional LIBS analyses to a new level. In addition, the recoveries of all the analytical elements in the environmental water samples were in the range from 88.6% to 109.9%, which further proves the feasibility and potential of MINAELIBS in practical liquid sample analysis.

As photonic crystals (PCs) are one of the most widely studied artificial biomimetic periodic nanostructures, their preparation methods have attracted significant attention. Recently, several methods have been developed for the self-assembly of PCs at solid and air/water interfaces. However, to date, their self-assembly at a hydrogel interface (HI) with special properties has not been explored and that at an air/gel interface is also rarely reported. Herein, a simple and novel strategy for the rapid self-assembly of PCs using a HI as an assembly interface is demonstrated. This approach is completely different from the preparation strategy of polymerized crystalline colloidal arrays (PCCAs), which involves the entrapment of a colloidal array inside a gel. Unlike the self-assembly at solid or air/water interfaces, the proposed method is faster and simpler and has the ability to prepare three-dimensional (3D) PCs on flat or curved surfaces. The reflection intensity of the hydrogel interface-photonic crystals (HI-PCs) could exceed 80%. Particularly, the transmissivity at a specific wavelength reached as low as 0.1%. Therefore, with the recent progress in the self-assembly of interfaces, soft matter interfaces, such as a hydrogel interface, will play an important new role, which is expected to open up an interesting field of research and provide more ideas for the preparation of advanced materials.

Widespread use of organophosphorus pesticides poses serious environmental threats, and hence calls for effective analysis methods for these classes of compounds. In this study, a lab-made graphene-based solid-phase microextraction (SPME) fiber was fabricated by the sol-gel method and combined with a gas chromatography-flame photometry detector (GC-FPD) to realize the detection of trace OPPs in water samples. Compared to the commercial fiber coatings, the new sol-gel graphene fiber coatings showed advantages of good durability and solvent resistance, which were attributed to the hydrophobic and antibacterial properties of the functionalized graphene and 3-(trimethoxysilyl)propyldimethyloctadecylammonium chloride (QAS). A headspace SPME method in combination with a GC-FPD was established to evaluate the performance of the novel fibers. The proposed method showed a good linear relationship for the eight OPPs (R2≥ 0.9957) in the concentration range of 1 to 1000 μg L-1, with limits of quantification of 0.11-3.37 μg L-1 and limits of detection of 0.03-1.01 μg L-1. Furthermore, the developed method also exhibited good recoveries for the analysis of OPPs both in rainwater and lake water, which demonstrates that this method is an alternative choice for multi-residue analysis of OPPs, and it has the potential for broader applications in the future.

DNA nanostructure-based drug delivery system (DDS) has become an advanced therapeutic strategy for cancer because of its unsurpassed editability, intrinsic biodegradability, and tunable multifunctionality. An intelligent DNA nanosystem integrating targeting, immunostimulation, and chemotherapy was constructed based on unmethylated cytosine-phosphate-guanine oligonucleotides (CpG ODNs) DNA nanohydrogels (CpG-MUC1-hydrogel). By facile one-step self-assembly, the cross-shaped DNAs (C-DNAs) assembled from pH-responsive I-motif sequences and targeted MUC1 aptamer-immunoadjuvant CpG-fused sequences (CpG-MUC1) were integrated into DNA nanohydrogels with controllable size by the hybridization of DNA linkers. Subsequently, DOX was successively intercalated into the base pairs of CpG-MUC1-hydrogel, resulting in CpG-MUC1-hydrogel/Dox that would disassemble and release DOX and CpGs at acidic conditions. After MUC1-mediated internalization, CpG-MUC1-hydrogel/Dox dissociated in the endo/lysosomes and induced favorable apoptosis of tumor cells. Afterward, liberated CpGs triggered vast cytokine secretion from immune cells which elicited potent immune response against malignancy. Notably, CpG-MUC1-hydrogel induced an apoptosis effect on MCF-7 cells via significantly increasing the Bax/Bcl2 ratios and a higher level of tumor necrosis factor (TNF-α) on RAW264.7 cells than naked CpGs. Our results demonstrated that self-assembled CpG-MUC1-hydrogel represented an attractive DDS for precise delivery, potent immunostimulating activity, and considerable combination efficiency with few adverse effects, which is expected to make breakthroughs in clinical translation.

A filamentary plasma jet was produced by a cylindrical dielectric-barrier discharge (DBD) equipped with a thin quartz tube. This plasma jet consists of many filaments, and the filaments bifurcate into thinner branches close to the ground electrode. Only a single filament is produced in each current pulse, and this filament is distorted in the long gas gap. The maximum electron density in the filament is on the order of $10^{15}$ cm $^{-3}$ . Optical emission examination shows a decrease of optical emissions from OH and Ar but an increase of optical emissions from N2 along the plasma jet. The vapor in the working gas argon rather than in the ambient air dominates the optical emissions from the de-excitation of OH along the plasma jet. Near the ground electrode, the nitrogen emission spectra mainly resulted from the direct electron effect on the ground state or metastable nitrogen and the collisions between nitrogen metastables. The rotational temperature is lower than the vibrational temperature but much higher than the room temperature. This feature makes the filamentary plasma jet only suitable for processing samples bearing high temperature.

Fifty three elements (both major and trace amounts) such as P, Mg, Al, As, and Pb etc. in Sanqi (Panax notoginseng) sampled from different spots around Laojun Mountain (Wenshan Zhuang and Miao Autonomous Prefecture, Yunnan Province, China) were determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The elemental distribution was extracted by means of Principle Component Analysis (PCA) and Cluster Analysis (CA). It was found that the major elements distributed in different content zones, thus providing possibility for differentiating Sanqi from other medicinal herbs. Furthermore, Metal Pollution Index (MPI) could be used to advise consumers on safety of Sanqi.

An instrument combining laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy was developed for the in situ atomic and molecular composition analysis of minerals. The apparatus consist...

Label-free and in situ detection of N-glycan expression on surface of cells is vital for understanding the progression of cancer. Herein, cytosensing based on U-shaped fiber optic local surface plasmon resonance (LSPR) was developed for cancer cell detection and N-glycan evaluation on cell surface. The U-shaped fiber optic LSPR has high refractive index sensitivity (RIS). Therefore, U-shaped fiber optic LSPR cytosensing afforded ultrasensitivity for cancer cell detection with the limit of detection (LOD) of 30 cells/mL and good linearity in a wide range of 1×102-1×106 cells/mL under the optimal conditions of modified AuNPs size and Con A concentration. The U-shaped fiber optic LSPR cytosensing shows more than 29 times lower limit of detection than the straight ones. More importantly, the prepared U-shaped cytosensing was applied to evaluate the N-glycan expression level on the surface of cancer cells under different concentration external stimuli of inhibitor tunicamycin (TM). Noticeably, U-shaped fiber optic LSPR cytosensing showed an acceptable reproducibility, satisfactory anti-interference and good selectivity, and was also applied in the assessment of N-glycan expression on surface of six kinds of cell lines. Therefore, the U-shaped fiber optic LSPR offers a feasible tool in biophysical research and clinical diagnosis for cancer.

A label-free and enzyme-free colorimetric sensor for rapid detection of Pb2+ is reported, which is based on the strategy of DNAzyme-mediated RNA cleavage combined with an annealing-accelerated DNA hybridization chain reaction (HCR). As a trigger DNA, the substrate strand (STM) of DNAzyme can initiate HCR effectively. However, when it is cleaved by DNAzyme in the presence of Pb2+, the separation of DNA functional domains leads to a serious decrease in HCR efficiency. As a result, the difference in Pb2+ concentration converts into the difference of DNA assembly, which eventually leads to the color change of colloidal gold nanoparticles (AuNPs). In this work, a DNA strand (cGR5) completely complementary to the catalytic strand (GR5) of DNAzyme is used to improve the dissociation of STM to enhance the HCR efficiency. In addition, the simple operation of DNA annealing is first used to accelerate the HCR process, enabling the Pb2+ detection to be completed in about 30 min. As advantages of high sensitivity, goo...

Thirty six elements (both macro- and micro-amounts) such as Mg, Al, Fe, Co etc. in Danshen (Salvia miltiorrhiza) samples collected from different origins, Nanyang (Henan province, origin production area), Nanchong (Sichuan province, main production area), Harbin, Shanghai, Wuhan, Chongqing and Guangzhou, were determined by ICP-AES (inductively coupled plasma-atomic emission spectrometry) and ICP-MS (inductively coupled plasma-mass spectrometry). The relationship between elemental distribution and production place was reported after analyzing those data by use of PCA (Principle Component Analysis) and CA (cluster analysis). The sample from Nanyang was quite different from others in characteristic of P, S, Al, Fe and Ba contents, and this may provide possibility for identifying the geological origin of Danshen samples. MPI (metal pollution index) could also help people to consume proper amount of Danshen products by describing metal pollution situation of all the samples.

Endoplasmic reticulum autophagy (ER-phagy) is an important strategy for cells against ER stress and maintain ER homeostasis. ER stress is considered as a potential toxicity of nanoparticles, but only a few studies have explored whether the nanoparticles-induced ER stress can trigger ER-phagy, and the precise molecular mechanism of ER-phagy mediated by nanoparticle-induced ER stress is still poorly understood. Therefore, our study focuses on the relationship between ER stress and ER-phagy caused by emerging nanoparticles CdTe-QDs and its molecular mechanism. The results showed that the accumulation of ROS and ER stress induced by CdTe-QDs contributed to the activation of autophagy and ER-phagy. Importantly, our study unraveled that CdTe-QDs activate autophagy by up-regulating the transcription of core autophagy machinery. It was found that the induced ER-phagy was mediated by Atg11/Atg40/Lst1-Sec23 instead of the autophagy machinery genes. We speculated that the ER-phagy caused by CdTe-QDs may include micro-ER-phagy and macro-ER-phagy. Collectively, this work provided valuable information for the application of CdTe-QDs in the field of biology and a theoretical basis for further understanding of ER-phagy.

Ultrasensitive detection of metallic elements in liquids has attracted considerable attention in fields such as environmental pollution monitoring and drinking water quality control. Hence, it is of great significance to develop a sensitive and simultaneous detection strategy for multiple metal elements in liquid. Laser-induced breakdown spectroscopy (LIBS) technology shows unique advantages because of its simple, rapid, and real-time in situ detection, but the laser energy will be greatly attenuated in the liquids; thus, the sensitivity of LIBS for direct detection of metal elements in liquid samples will decrease sharply. In this study, inspired by the structure of Stenocara beetle's back, a superhydrophobic biomimetic interface with hydrophilic array was prepared for enriching low-concentration targets into detection regions, and the biomimetic array LIBS (BA-LIBS) was successfully established. The ultrasensitive and simultaneous detection of nine metal elements in drinking water was realized based on the effective enrichment method. The limits of detection of the nine metal elements in mixed solution ranged from 8.3 ppt to 13.49 ppb. With these excellent properties, this facile and ultrasensitive BA-LIBS strategy might provide a new idea for the prevention and control of metal hazards in the liquid environment.

Inadequate sensitivity and side-effect are the main challenges to develop cytosensors combining with therapeutic potential simultaneously for cancer diagnosis and treatment. Herein, localized surface plasma resonance (LSPR) based on hybridized nanolayer modified Ω-shaped fiber-optic (HN/Ω-FO) was developed to integrate cytosensor and plasmonic photothermal treatment (PPT). On one hand, hybridized nanolayers improve the coverage of nanoparticles and refractive index sensitivity (RIS). Moreover, the hybridized nanoploymers of gold nanorods/gold nanoparticles (AuNRs/AuNPs) also result in intense enhancement in electronic field intensity (I). On the other hand, Ω-shaped fiber-optic (Ω-FO) led to strong bending loss in its bending part. To be specific, a majority of light escaped from fiber will interact with HN. Thus, HN/Ω-FO synergistically enhances the plasmonic, which achieved the goal of ultrasensitive cytosensor and highly-efficient plasmonic photothermal treatment (PPT). The proposed cytosensor exhibits ultrasensitivity for detection of cancer cells with a low limit of detection down to 2.6 cells/mL was realized just in 30 min. HN/Ω–FO–based LSPR exhibits unique characteristics of highly efficient, localized, and geometry-dependent heat distribution, which makes it suitable for PPT to only kill the cancer cells specifically on the surface or surrounding fiber-optic (FO) surface. Thus, HN/Ω-FO provides a new approach to couple cytosensor with PPT, indicating its great potential in clinical diagnosis and treatment.

Antibiotic residues have become the major source of environmental pollutants. In order to monitor tetracycline (TC) in the environment, we have established a highly sensitive and wash-free homogeneous time-resolved immunoassay. This analytical method was based on a rare earth chelate with excellent fluorescence properties. The cryptate organic ligand had good stability and acted as an antenna for Eu3+ excitation. In a homogeneous system, the Eu3+ cryptate complex was used as a label to bind to antibodies. Under the action of immunoaffinity, fluorescent donors and acceptors were close to each other, which induced the FRET effect to produce proportional fluorescence. Under the optimal parameters, the half-inhibitory concentration (IC50) and limit of detection (LOD, IC10) of TC were 0.4188 ng mL-1 and 0.0106 ng mL-1, respectively. The linear range (IC20-IC80) was 0.0273-9.2645 ng mL-1. With the environmental samples, the recovery rate of TC was 84.3-107.2%, and the standard deviation (RSD) was 4.6-12.9%. The results showed the good sensitivity and reliability of the method. Compared with the traditional ELISA, our method has less background interference, only one step was required without the washing procedure, and the detection result can be obtained by 30 min incubation, which improves the detection efficiency. Because of the characteristics of immunoassays, different pollutants can be monitored by changing the antibodies. This method provides an alternative path for detecting environmental pollutants and has the potential to develop into an on-site detection kit.

This study proposes steganography based on laser-induced breakdown spectroscopy (LIBS) for the first time. LIBS inks containing different elements in varying concentrations were fabricated to write steganographic text. LIBS was combined with machine learning as an ideal tool to efficiently extract hidden information. The proposed steganography strategy has the advantages of low cost, high security, and good stability, thus providing a practical tool for information transfer.

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal human cancers with a lower 5-year survival rate. N6-methyladenosine (m6A) methylation, an important epigenetic modification, has been reported to associate with physiological and pathological processes of cancers. However, its role in ESCC remains unclear. In this work, we found that the m6A levels were elevated in ESCC cancer tissues and ESCC cells. The PPI network demonstrated that METTL3, METTL14, WTAP, RBM15, and KIAA1429 were all significantly associated with each other. Moreover, we found a significant upregulation of METTL3 mRNA and protein amounts in ESCC tissues. The METTL3 mRNA expression level of tissues had associations with ESCC differentiation extent and sex (p

Here, we show that molecular N2 was efficiently captured by organic arylium cations in a well-defined manner at ambient pressure and temperature, which was monitored by on-line mass spectrometry analysis. A kinetic picture was proposed to disclose the principle of the ion-molecule reaction behavior for exclusive aryldiazonium production. The observation has an implication for direct nitrogen fixation into an organic framework via the intermediacy of such cationic species.

Based on microwave plasma torch optical emission spectrometry combined with laser ablation, a direct solid sample detection device was developed for sensitive determination of heavy metals in soil. In the proposed laser ablation microwave plasma torch optical emission spectrometry (LA-MPT-OES) device, a new ablation chamber was designed, which the washout time and the relative standard deviation of this chamber were almost one-third of those of the conventional one, indicating that the proposed chamber had a smaller dead volume to provide efficient and stable transport of ablated sample particles. Meanwhile, to ensure a high signal intensity during a long exposure time, the moving sampling method was used to guarantee a sufficient injection amount. With the optimal experimental parameters, the limits of detection (LODs) of Cu, Pb, Cr and Ag were 0.075, 0.093, 0.068, 0.009 mg·kg

Bacteria, especially foodborne pathogens, seriously threaten human life and health. Rapid discrimination techniques for foodborne pathogens are still urgently needed. At present, laser-induced breakdown spectroscopy (LIBS), combined with machine learning algorithms, is seen as fast recognition technology for pathogenic bacteria. However, there is still a lack of research on evaluating the differences between different bacterial classification models. In this work, five species of foodborne pathogens were analyzed via LIBS; then, the preprocessing effect of five filtering methods was compared to improve accuracy. The preprocessed spectral data were further analyzed with a support vector machine (SVM), a backpropagation neural network (BP), and k -nearest neighbor (KNN). Upon comparing the capacity of the three algorithms to classify pathogenic bacteria, the most suitable one was selected. The signal-to-noise ratio and mean square error of the spectral data after applying a Savitzky–Golay filter reached 17.4540 and 0.0020, respectively. The SVM algorithm, BP algorithm, and KNN algorithm attained the highest classification accuracy for pathogenic bacteria, reaching 98%, 97%, and 96%, respectively. The results indicate that, with the support of a machine learning algorithm, LIBS technology demonstrates superior performance, and the combination of the two is expected to be a powerful tool for pathogen classification.

Measurement and reconstruction of an elemental image of large brain tissue will be beneficial to the diagnosis of neurological brain diseases. Herein, laser-induced breakdown spectroscopy (LIBS) is introduced for three dimensional (3D) elemental analysis of paraffin-embedded mouse brain tissue blocks. It is used for the first time towards the mapping of mouse brain block samples. A micro-LIBS prototype is developed for brain elemental imaging and a layer-by-layer approach is used to reconstruct the 3D distribution of Ca, Mg, Na, Cu, and P in the brain tissue. Images are captured with 50 μm lateral resolution and 300 μm depth resolution. The images show that the reclamation area of the cortex surface is enriched with Ca and Mg. In contrast, the Cu distribution is circular and is found primarily in the entirety of the cerebral cortex for the paraffin-embedded brain samples. Elemental imaging results suggest that the highest P intensity is found in the cerebellum nearby the middle sagittal plane in the left-brain paraffin block. These preliminary results indicate that LIBS is a potentially powerful tool for elemental bioimaging of the whole brain and may further improve the understanding of complex brain mechanisms.

A low-cost and multi-channel smartphone-based spectrometer was developed for LIBS. As the CMOS detector is two-dimensional, simultaneous multichannel detection was achieved by coupling a linear array of fibres for light collection. Thus, besides the atomic information, the spectral images containing the propagation and spatial distribution characters of a laser induced plasma plume could be recorded. With these additional features, accurate rock type prediction was achieved by processing the raw data directly through a deep learning model.

We studied the effect of optical clearing (OC) by glycerol on laser-induced tissue plasma using the immersion method. The results demonstrated the apparently enhanced effect of glycerol on the molecular spectra of the laser induced plasma. The OC is more sensitive to the molecular bands than atomic lines. After tissue immersion in the glycerol, the electron density of tissue plasma is decreased. The laser plasma temperature of the glycerol treated tissue is higher than for virgin fresh tissue. The tissue plasma after the glycerol application is still in the local thermal equilibrium plasma state. This work presents a new perspective for OC application that can extend from tissue better imaging quality to improvement of laser plasma generation.

Current industrial production of HNO

With the continuous development of biosensors, researchers have focused increasing attention on various signal amplification strategies to pursue superior performance for more applications. In comparison with other signal amplification strategies, hybridization chain reaction (HCR) as a powerful signal amplification technique shows its certain charm owing to nonenzymatic and isothermal features. Recently, on the basis of conventional HCR, this technique has been developed and improved rapidly, and a variety of HCR-based biosensors with excellent performance have been reported. Herein, we present a systematic and critical review on the research progress of HCR in biosensors in the last five years, including the newly developed HCR strategies such as multibranched HCR, migration HCR, localized HCR, in situ HCR, netlike HCR, and so on, as well as the combination strategies of HCR with isothermal signal amplification techniques, nanomaterials, and functional DNA molecules. By illustrating some representative works, we also summarize the advantage and challenge of HCR in biosensors, and offer a deep discussion of the latest progress and future development trends of HCR in biosensors.

Bacteria seriously endanger human life and health, and the detection of bacteria is vital for the prevention and treatment of related diseases. Surface-enhanced Raman scattering (SERS) is considered as a powerful technique for bacterial detection due to the inherent richness of spectral data. In this work, a novel SERS strategy based on three-dimensional (3D) DNA walker was developed for quantitative analysis of Salmonella typhimurium (S. ty). The complimentary DNA of S.ty-recognizing aptamer (cApt) was replaced from the double-stranded DNA (dsDNA) of Apt@cApt in the presence of S.ty, which can trigger the endonuclease mediated “DNA walker” on the surface of gold modified magnetic nanoparticles (AuMNPs). The DNA residues on the surface of AuMNPs can bind to SERS tag through base complementary pairing, and the complex of “AuMNPs@SERS tag” can be separated from the fluid by an external magnetic field for SERS analysis. It was found that the SERS intensity showed a good linear relationship with both lower (10–104 CFU/mL) and higher (104–106 CFU/mL) S.ty concentration. A superior limit of detection (LOD) as low as 4 CFU/mL was achieved due to the signal amplification effect of “DNA walker”, and the preeminent selectivity of the proposed method was determined by the selectivity of the aptamer sequence. This strategy of separating the SERS tag from the biological matrix enables high stability and good repeatability of the SERS spectra, which presents a new method for SERS detection of biomaterials that can benefit various application scenarios.

At present, two-dimensional (2D) materials have shown great application potential in numerous fields based on their physical chemical and electronic properties. Raman spectroscopy and derivative techniques are effective tools for characterizing 2D materials. Raman spectroscopy conveys lots of knowledge on 2D materials, including layer number, doping type, strain and interlayer coupling. This review summarized advanced applications of Raman spectroscopy in 2D materials. The challenges and possible applied directions of Raman spectroscopy to 2D materials are discussed in detail.

A single-beam-splitting approach was used to enhance the signal intensity of LIBS under the extreme conditions of laser beam grazing of the surface of non-flat samples. Time-resolved spectra show that the laser-ablated plasma presents a stronger spectral intensity and a slower plasma decay in the split beam mode because of the higher laser irradiance. The temporal evolutions of signal enhancement factors indicate that the enhancement effect first rises and then drops with delay time and the maximum enhancement factor of Al plasma comes later than that of Cu plasma under the same laser energy. The mechanisms behind it are discussed. It is also found that the electron density exhibits a faster decay with delay time in the split beam mode, mainly due to the faster plasma expansion. And a slower increase of electron density with laser energy is observed in the split beam mode because of the plasma shielding effect.

A new ambient ionization technique named laser ablation micro-fabricated glow discharge plasma (LA-MFGDP) was developed for mass spectrometry in this study. This technique used low energy laser for sample ablation and ionized sample aerosol with MFGDP in sequence. The combination of laser ablation and MFGDP exhibited a synergetic effect that significantly improved the performance of MFGDP. Experimental results showed that MFGDP dominated the ionization process while laser played the role of desorption in LA-MFGDP. [M+H]+ and M+ proved that proton transfer reactions and charge transfer reactions were involved in the ionization process, respectively, indicating that the ionization character was the same as MFGDP. LA-MFGDP could analyze less volatile samples that were unable to be detected by MFGDP because laser significantly improved the ionization capability of MFGDP. Strong ion signals were obtained by LA-MFGDP with low sample consumption. The limits of detection (LODs) of LA-MFGDP was as low as three orders of magnitude than that of MFGDP, which demonstrated that LA-MFGDP possessed an outstanding advantage in detecting trace substances. LA-MFGDP was successfully applied to detect pharmaceutical tablets without any pretreatment. Benefited from the excellent performance, LA-MFGDP offers great potential in broadening the application of ambient mass spectrometry.

In this paper, the CO2 splitting process was performed under atmospheric pressure in a multi-electrode cylindrical dielectric barrier discharge (DBD) plasma reactor. The influence of the plasma processing parameters including discharge voltage, discharge length and gas flow rate was investigated. Besides, the effect of the similar specific energy input (SEI) values obtained using different plasma powers and gas flow rates was studied. The experimental results indicated that the CO2 conversion and energy efficiency increased along with the increased discharge length due to the increased residence time and the enhanced electric field. The increase of the applied voltage and hence the plasma power or the decrease of the gas flow rate generated enhanced effect on CO2 conversion while negative influence on energy efficiency. In addition, by comparing the energy efficiency at similar SEI values obtained with different discharge powers and gas flow rates, it was found that the gas flow rate played a more important role in CO2 conversion. The proposed multi-electrode plasma reactor led to the highest CO2 conversion of 18.50% and maximum energy efficiency of 12.83%. Compared with other types of cylindrical DBD plasma reactors, the multi-electrode design proposed in this work can give a similar CO2 conversion and higher energy efficiency. The multi-electrode design can enhance the local electric field at the electrode edges, leading to the enhanced corona discharge and the generation of more micro-discharges, which is considered to be responsible for enhanced CO2 conversion process.

Ambient mass spectrometry (AMS) has grown as a group of advanced analytical techniques that allow for the direct sampling and ionization of the analytes in different statuses from their native environment without or with minimum sample pretreatments. As a significant category of AMS, plasma-based AMS has gained a lot of attention due to its features that allow rapid, real-time, high-throughput, in vivo, and in situ analysis in various fields, including bioanalysis, pharmaceuticals, forensics, food safety, and mass spectrometry imaging. Tens of new methods have been developed since the introduction of the first plasma-based AMS technique direct analysis in real-time. This review first provides a comprehensive overview of the established plasma-based AMS techniques from their ion source configurations, mechanisms, and developments. Then, the progress of the representative applications in various scientific fields in the past 4 years (January 2017 to January 2021) has been summarized. Finally, we discuss the current challenges and propose the future directions of plasma-based AMS from our perspective.

Current rapid bacterial detection methods are dedicated to the classification and identification of bacteria. However, there is still a lack of a method for specific quantitative analysis of certain bacteria. In this work, a method based on elemental-tags laser-induced breakdown spectroscopy (ETLIBS) was developed for the rapid and specific quantitative analysis of

Laser-induced breakdown spectroscopy (LIBS) is capable of providing elemental analysis while Raman spectroscopy is powerful for molecular and structural characteristics of crystalline substances. T...