Combined detection of SARS-CoV-2 neutralizing antibodies and specific IgG in plasma based on SERS magnetic sensor.

In this study, a surface-enhanced Raman spectroscopy (SERS) magnetic sensor is established based on SERS principle and magnetic separation technology, and a highly sensitive, simple and fast method for quantitative detection of neutralizing antibodies (nABs) and specific IgG of SARS-CoV-2 in plasma is established combined with immunoassay. Two kinds of Raman nanospheres (RNPs) with different characteristic Raman shifts are used as signal sources and coupled to ACE2 and anti-IgG (FC) antibodies respectively, and magnetic beads are coupled to RBD. The competitive relationship between ACE2 and nABs, the binding relationship between specific IgG and anti-IgG (FC) antibodies are determined. The results show that the concentrations of nABs and specific IgG in the range of 10-2000 ng ml-1are well correlated with SERS response intensity, and the recoveries are both between 90%-110%, with good precision. Bilirubin and common anticoagulants have no interference on the detection results. This method is accurate, reliable, sensitive and does not require complex pre-treatment, and is expected to be used for simultaneous detection of nABs and specific IgG in plasma of SARS-CoV-2. It has guiding significance for the development and evaluation of vaccines and the formulation of individualized vaccination schedule.

NiTi-Layered Double Hydroxide@Carbon Nanotube as a Cathode Material for Chloride-Ion Batteries.

Chloride-ion batteries (CIBs) are one of the promising candidates for energy storage due to their low cost, high theoretical energy density and high safety. However, the limited types of cathode materials in CIBs have hindered their development. In this work, a NiTi-LDH@CNT composite is prepared using a reverse microemulsion method and applied in CIBs for the first time. The specific surface area and the pore volume of the obtained NiTi-LDH@CNT composites can reach 266 m2 g-1 and 0.42 cm3 g-1, respectively. Electrochemical tests indicate that the composite electrode delivers a reversible specific capacity of 69 mAh g-1 after 150 cycles at a current density of 100 mA g-1 in 0.5 M PP14Cl/PC electrolyte. Ni2+/Ni3+ and Ti3+/Ti4+ valence changes during electrochemical cycling are demonstrated by X-ray photoelectron spectroscopy (XPS), while reversible migration of Cl- is revealed by ex-situ EDS and ex-situ XRD. The stable layered structure and abundant valence changes of the NiTi-LDH@CNT composite make it an exceptional candidate as a cathode material for CIBs.

FeOCl Nanoparticle-Embedded Mesocellular Carbon Foam as a Cathode Material with Improve d Electrochemical Performance for Chloride-Ion Batteries.

Chloride-ion batteries (CIBs) have been regarded as a promising alternative battery technology to lithium-ion batteries because of their abundant resources, high theoretical volumetric energy density, and high safety. However, the research on chloride-ion batteries is still in its infancy. Exploring appropriate cathode materials with desirable electrochemical performance is in high demand for CIBs. Herein, the FeOCl nanocrystal embedded in a mesocellular carbon foam (MCF) has been prepared and developed as a high-performance cathode material for CIBs. The MCF with uniform and large mesocells (15.7-31.2 nm) interconnected through uniform windows (15.2-21.5 nm) can provide high-speed pathways for electron and chloride-ion transport and accommodate the strain caused by the volume change of FeOCl during cycling. As a result, the optimized FeOCl@MCF cathode exhibits the highest discharge capacity of 235 mAh g-1 (94% of the theoretical capacity) among those of the previously reported metal (oxy)chloride cathodes for CIBs. A reversible capacity of 140 mAh g-1 after 100 cycles is retained. In contrast, only 18 mAh g-1 was kept for the FeOCl cathode.

Rapid and sensitive detection of amphetamine by SERS-based competitive immunoassay coupled with magnetic separation.

Amphetamine (AMP), as a psychiatric drug acting on the central nervous system, and has become one of the most common drugs of abuse in the illegal market at present, which adversely affects social public safety. We developed a SERS magnetic immunoassay with high sensitivity, specificity, and rapid and quantitative detection of AMP. We synthesized a high SERS intensity substrate (Au-XP013@Ag) using the "hot spot" effect and combined it with antibodies to form SERS immunotags (Au-XP013@Ag-AMP-mAb). Subsequently, the carboxyl magnetic beads were linked to label antigens as functional magnetic beads (carboxyl magnetic beads-AMP-BSA). Using the principle of competitive immunoassay, the Raman response value of the immune complex formed with SERS tags and functional magnetic beads was detected to realize the quantitative detection of AMP. The detection limit of this method for AMP was 2.28 ng mL-1. More importantly, a portable Raman instrument was used in this study, which can meet the requirements of point-of-care testing (POCT). Therefore, this SERS-based magnetic immunoassay can provide a favorable scientific basis for the control of drug abuse, monitoring by law enforcement agencies, and determination of drug users.

Synchronous detection of IgG subtypes based on SERS combined with immunoassay.

In this study, a rapid, simple, highly sensitive and anti-interference method for the joint detection of four IgG subtypes is established by using Raman microspheres with four characteristic Raman spectra. The results show that the concentrations of IgG1 in the range of 0-1500 ng ml-1, IgG2 in the range of 0-1100 ng ml-1, IgG3 in the range of 0-88.7 ng ml-1, IgG4 in the range of 0-77.2 ng ml-1, it shows a good correlation with the response value of The Raman signal. The lowest detection limits are 25.4 ng ml-1, 21.7 ng ml-1, 1.6 ng ml-1, 1.7 ng ml-1, respectively. Reproducibility is good, the coefficient of variation of low, medium and high concentration standard solution are within 10%. The recoveries of four IgG subtypes are in the range of 90%-110%, and the accuracy of the method is good. The coefficients of variation between and within the three batches of reagents are all less than 11%, showing good precision. There is no cross reaction with Procalcitonin (20 ng ml-1), Interleukin-6 (1 ng ml-1) and bovine serum albumin (10 mg ml-1), and the specificity is good. Common interfering substances such as bilirubin, triglyceride and trisodium citrate do not affect the determination results, and heparin sodium only affects the determination results of IgG1. This method has good anti-interference ability. The method has high sensitivity, simple operation and strong anti-interference ability, and has good correlation with the IgG detection methods commonly used in clinic. This simple and quantitative method can be used for the rapid detection of IgG subtypes in the future, which can improve the efficiency of clinical diagnosis.

Rapid, highly sensitive and quantitative detection of interleukin 6 based on SERS magnetic immunoassay.

Sepsis is a systemic inflammatory response syndrome caused by infection, and is a common disease in intensive care units (ICUs), whereby the mortality rate is as high as 30% to 50%. Early diagnosis and treatment can significantly reduce the mortality rate of patients with sepsis. We have developed a method based on SERS for the rapid and quantitative detection of IL-6. Using the principle of double antibody sandwich, the core-shell nanoparticles embedded with a Raman reporter (Au@4MBA@Ag NPs) are coupled to the tracer antibody, while the biotin was coupled to the capture antibody to form an antibody-antigen-antibody sandwich structure with the antigen during detection of the structure. Streptavidin (SA) and biotin had a strong affinity, and the sandwich structure was captured by SA magnetic beads and detected by Raman spectroscopy under the enrichment of an external magnetic field. The results showed a good linear relationship between the Raman signal and the concentration of IL-6 in the concentration range of 0-1000 pg mL-1 (r = 0.9997) with a limit of detection of 1.6 pg mL-1. Also, the recovery rate of standard addition was 93.9-99.1%, and the coefficient of variation intra-assay and inter-assay of the three batches of reagents was less than 15%. Furthermore, it showed excellent specificity with procalcitonin (PCT, 20 ng mL-1) and C-reactive protein (CRP, 100 µg mL-1) and had no cross-reactivity. Except for bilirubin (2 mg mL-1) and hemoglobin (10 mg mL-1), other common interferences in the serum did not interfere, showing good anti-interference performance. Moreover, 57 clinical serum samples were detected via the chemiluminescence method simultaneously, and the detection results showed a good correlation (R2 = 0.9793, P < 0.01). There was no significant difference between the two performances (P > 0.05). The proposed method has numerous advantages such as high sensitivity, wide linear range, short detection time and simple operation, which provide a new technical reference for the clinical detection of sepsis biomarkers.

Simultaneous Quantitative Detection of IL-6 and PCT Using SERS magnetic immunoassay with sandwich structure.

Sepsis is a systemic inflammatory response syndrome caused by infection. The mortality rate is as high as 30%-50%. Early diagnosis and treatment can significantly improve the mortality of patients with sepsis. Therefore, we have developed a SERS-based magnetic immunoassay method that uses the principle of sandwich method to quantitatively detect Interleukin 6 (IL-6) and Procalcitonin (PCT). In this article, two different Raman reporter molecules are embedded in the middle of the Au@Ag shell and coupled with the tracer antibody to form a SERS immunoprobe. Biotin was coupled with capture antibody to form a sandwich structure when participating in the immune response. Streptavidin and biotin systems have extremely high binding affinity. The sandwich structure is quickly captured by SA magnetic beads and then applied with a magnetic field to enrich the magnetic beads. Finally, simultaneous quantitative detection is achieved by the intensity of the two Raman reporter characteristic peaks on the solution magnetic beads. IL-6 and PCT showed a good relationship between 0-1000 pg ml-1and 0-20 ng ml-1, respectively, and the limits of detection were 0.54 pg ml-1and 0.042 ng ml-1, respectively. The recovery rate was between 89.8% and 104.2%, both intra-assay and inter-assay CV were ≤20%. No cross-reaction with C-reactive protein (100µg ml-1), showing good specificity. This method provides a new technical reference for the clinical detection of sepsis biomarkers.

Application of lectin-based biosensor technology in the detection of foodborne pathogenic bacteria: a review.

Foodborne diseases caused by pathogenic bacteria pose a serious threat to human health. Early and rapid detection of foodborne pathogens is urgently needed. The use of biosensors to identify and detect pathogenic bacteria has attracted ample attention because of their high sensitivity, near real-time quantification without enrichment, on-site detection, simple operation, and so on. As a promising alternative recognition element in biosensors, lectins have been widely studied in bacterial detection because of their high stability and low cost. In this review, we highlight the progress of lectin-based pathogen detection methods, including various electrochemical methods, optical methods and quartz crystal microbalance methods, as well as lectin based microfluidic methods. The interaction mechanism between lectins and bacterial recognition site-sugars is also studied. Finally, the future prospects and challenges in the development of lectin-based biosensors are discussed.

SERS-based magnetic immunoassay for simultaneous detection of cTnI and H-FABP using core-shell nanotags.

Acute myocardial infarction (AMI) is the single leading cause of worldwide mortality and morbidity. Heart-type fatty acid-binding protein (H-FABP) and cardiac troponin I (cTnI), as biomarkers emerging at different stages of AMI, have complementary advantages in terms of specificity and sensitivity. Therefore, we developed a magnetic immunoassay method based on surface-enhanced Raman scattering (SERS) to detect H-FABP and cTnI simultaneously. Herein, two mutually independent Raman reporter molecules were embedded between a gold core and silver shell and then combined with a tracer antibody to form a SERS immunoprobe. During detection, the SERS immunoprobe, target antigen and capture probe undergo an immune reaction to form a sandwich structure, and then the immune complex was enriched by a specific reaction of streptavidin on the surface of magnetic beads with biotin. Finally, the concentration of biomarkers was quantified by detecting the characteristic Raman peak intensities of the two Raman reporter molecules. Under the optimized conditions, the minimum detection limits of H-FABP and cTnI were 0.6396 and 0.0044 ng mL-1, respectively. Besides, the target antigen does not cross-react with non-specific proteins, showing good specificity. Therefore, our proposed SERS-based magnetic immunoassay method has the advantages of accuracy, rapidity and good selectivity, and has great potential for early diagnosis of acute myocardial infarction disease.

A novel surface-enhanced Raman scattering method for simultaneous detection of ketamine and amphetamine.

As common psychotropic drugs, ketamine (KET) and amphetamine (AMP) are often consumed by drug users at the same time, which seriously threatens people's health. Therefore, the study of simultaneous detection methods for KET and AMP is imperative. In this study, a novel method for the simultaneous detection of KET and AMP in serum was established on the basis of surface-enhanced Raman scattering (SERS). The antibodies were attached on Au@Ag core-shell nanoparticles embedded with different Raman reporters as the detection substrates. The labelled antigens KET-BSA and AMP-BSA were linked to carboxyl magnetic beads, and by adopting the principle of competitive immunoassay, the quantitative detections of ketamine and amphetamine were realized at the same time by detecting the Raman signals at different characteristic peaks on the magnetic beads. A good correlation was shown between ketamine and amphetamine and Raman signal response values were in the concentration range of 0-60 ng mL-1 and 0-200 ng mL-1, and the limits of detection were 1.64 and 2.44 ng mL-1. This method had the advantages of simple, rapid operation, and high sensitivity, and can realise double indicator simultaneous detection, which provided a more favorable scientific basis for preventing or reducing drug abuse, and identifying and monitoring drug users.

Cation-Disordered Lithium-Excess Li-Fe-Ti Oxide Cathode Materials for Enhanced Li-Ion Storage.

Cation-disordered Li-excess lithium-transition metal (Li-TM) oxides designed based on the percolation theory are regarded as a promising new type of high-performance cathode material for Li-ion batteries. Herein, cation-disordered rocksalt-type Li-Fe-Ti oxides of Li0.89Fe0.44Ti0.45O2, Li1.18Fe0.34Ti0.45O2, and Li1.24Fe0.38Ti0.38O2 with different Li-to-transition metal ratios (Li/TM = 1, 1.49, or 1.63) are investigated to understand the effect of a Li excess on the electrochemical Li-ion storage properties. The Li excess leads to local structural fluctuations of the as-prepared Li-Fe-Ti oxides, contributing to the formation of 0-TM diffusion channels for rapid Li-ion migration. The as-prepared Li-excess Li-Fe-Ti oxide cathodes (Li/TM = 1.49 and Li/TM = 1.63) deliver a higher reversible capacity of over 220 mAh g-1 and a better rate capability compared to the Li/TM = 1 electrode, which possesses a maximum discharge capacity of only about 165 mAh g-1. The redox reactions of Fe2+/Fe3+ and O2-/O22- achieve the main capacity of the Li-excess Li-Fe-Ti oxide cathodes during cycling, as supported by 57Fe Mössbauer spectroscopy, O 1s X-ray photoelectron spectroscopy, and O K-edge soft X-ray absorption spectroscopy.

Dual-doped hierarchical porous carbon derived from biomass for advanced supercapacitors and lithium ion batteries.

Nowadays, designing heteroatom-doped porous carbons from inexpensive biomass raw materials is a very attractive topic. Herein, we propose a simple approach to prepare heteroatom-doped porous carbons by using nettle leaves as the precursor and KOH as the activating agent. The nettle leaf derived porous carbons possess high specific surface area (up to 1951 m2 g-1), large total pore volume (up to 1.374 cm3 g-1), and high content of nitrogen and oxygen heteroatom doping (up to 17.85 at% combined). The obtained carbon as an electrode for symmetric supercapacitors with an ionic liquid electrolyte can offer a superior specific capacitance of 163 F g-1 at 0.5 A g-1 with a capacitance retention ratio as high as 67.5% at 100 A g-1, and a low capacitance loss of 8% after 10 000 cycles. Besides, the as-built supercapacitor demonstrates a high specific energy of 50 W h kg-1 at a specific power of 372 W kg-1, and maintains 21 W h kg-1 at the high power of 40 kW kg-1. Moreover, the resultant carbon as a Li-ion battery anode delivers a high reversible capacity of 1262 mA h g-1 at 0.1 A g-1 and 730 mA h g-1 at 0.5 A g-1, and maintains a high capacity of 439 mA h g-1 after 500 cycles at 1 A g-1. These results demonstrate that the nettle leaf derived porous carbons offer great potential as electrodes for advanced supercapacitors and lithium ion batteries.

Hierarchically ordered mesoporous Co3O4 materials for high performance Li-ion batteries.

Highly ordered mesoporous Co3O4 materials have been prepared via a nanocasting route with three-dimensional KIT-6 and two-dimensional SBA-15 ordered mesoporous silicas as templates and Co(NO3)2 · 6H2O as precursor. Through changing the hydrothermal treating temperature of the silica template, ordered mesoporous Co3O4 materials with hierarchical structures have been developed. The larger pores around 10 nm provide an efficient transport for Li ions, while the smaller pores between 3-5 nm offer large electrochemically active areas. Electrochemical impedance analysis proves that the hierarchical structure contributes to a lower charge transfer resistance in the mesoporous Co3O4 electrode than the mono-sized structure. High reversible capacities around 1141 mAh g(-1) of the hierarchically mesoporous Co3O4 materials are obtained, implying their potential applications for high performance Li-ion batteries.

Facile and Eco-Friendly Synthesis of Finger-Like Co3O4 Nanorods for Electrochemical Energy Storage.

Co3O4 nanorods were prepared by a facile hydrothermal method. Eco-friendly deionized water rather than organic solvent was used as the hydrothermal media. The as-prepared Co3O4 nanorods are composed of many nanoparticles of 30-50 nm in diameter, forming a finger-like morphology. The Co3O4 electrode shows a specific capacitance of 265 F g-1 at 2 mV s-1 in a supercapacitor and delivers an initial specific discharge capacity as high as 1171 mAh g-1 at a current density of 50 mA g-1 in a lithium ion battery. Excellent cycling stability and electrochemical reversibility of the Co3O4 electrode were also obtained.