Ultrasensitive detection of multiple Alzheimer's disease biomarkers by SERS-LFA.

Alzheimer's disease (AD) is one of the top public health crises in the 21st century, especially in an aging society. Early diagnosis, prevention, and intervention can significantly reduce the risk of AD. Detection of multiple AD biomarkers in blood is an effective strategy and has drawn more and more attention in recent years. However, the concentration of AD biomarkers is very low, therefore, point-of-care testing (POCT) techniques are needed for sensitive detection. Herein, a lateral flow assay, based on Surface-enhanced Raman scattering nanotags (SERS-LFA), is proposed for the simultaneous quantification of multiple AD biomarkers including Amyloid-beta 42, Amyloid-beta 40, tau proteins, and neurofilament light chain. The limit of detection for four AD biomarkers is 138.1, 191.2, 257.1, and 309.1 fg mL-1, respectively, which are two orders of magnitude lower than their concentrations in blood. Compared with the existing detection technology, SERS-LFA has the advantages of high specificity, high sensitivity, low cost, multiple detection, and rapid detection. Therefore, SERS-LFA has a broad application prospect in the early diagnosis and monitoring of AD in the future.

Effects of emergency treatment mode of damage-control orthopedics in pelvic fracture complicated with multiple fractures.

OBJECTIVE: This study aimed to observe the application effect of emergency treatment mode of damage-control orthopedics (DCO) in pelvic fracture complicated with multiple fractures. METHODS: Ninety-four patients with pelvic fracture complicated with multiple fractures in our hospital were recruited and divided into two groups according to the random number table method, with 47 cases in each group. Patients in the control group received traditional methods for emergency treatment (early complete treatment), and patients in the research group received DCO for emergency treatment (treatment performed in stages according to patient's physiological tolerance, with simplified initial surgery, followed by ICU resuscitation, and finally definitive surgery). The two groups were compared in terms of mortality, the incidence of acidosis and hypothermia three days after the first surgery, surgery-related indexes (time of the first surgery, blood transfusion volume, intraoperative blood loss, recovery time of temperature, and length of hospital stay), coagulation function indexes (activated partial thromboplastin time (APTT), thrombin time (TT), prothrombin time (PT) and fibrinogen (FIB)), postoperative reduction of fracture, complication rate, and quality of life. RESULTS: The incidences of acidosis, hypothermia, and mortality three days after the first surgery in the research group were lower than those in the control group (P<0.05). Compared with the control group, the research group experienced shorter time of the first surgery, less intraoperative blood transfusion volume, less intraoperative blood loss, shorter recovery time of body temperature, and shorter length of hospital stay (P<0.05). Seven days after surgery, PT, TT and APTT decreased and FIB increased in both groups (P<0.05), PT, TT and APTT in the research group were lower than those in the control group (P<0.05), while FIB was higher (P<0.05). The good rate of reduction in the research group was higher than that in the control group (P=0.025). The incidence of complications in the research group was lower than that in the control group (P=0.049). Six months after surgery, the scores of physiological function (PF), body pain (BP), role physical (RP), emotional function (EF), social function (SF), vitality, and general health (GH) of the research group were higher than those of the control group (P<0.05), but there was no significant difference in mental health (MH) between the two groups (P>0.05). CONCLUSION: The emergency treatment mode of DCO is effective in pelvic fracture complicated with multiple fractures, which can effectively improve postoperative reduction of patients, improve the coagulation function, reduce complications, and improve the quality of life.

Bio-barcode triggered isothermal amplification in a fluorometric competitive immunoassay for the phytotoxin abrin.

Abrin is one of the most toxic phytotoxins to date, and is a potential biological warfare agent. A bio-barcode triggered isothermal amplification for fluorometric determination of abrin is described. Free abrin competes with abrin-coated magnetic microparticles (MMP) probes to bind to gold nanoparticle (AuNP) probes modified with abrin antibody and bio-barcoded DNA. Abundant barcodes are released from the MMP-AuNP complex via dithiothreitol treatment. This triggers an exponential amplification reaction (EXPAR) that is monitored by real-time fluorometry, at typical excitation/emission wavelengths of 495/520 nm. The EXPAR assay is easily operated, highly sensitive and specific. It was used to quantify abrin in spiked commercial samples. The detection limit (at S/N = 3; for n = 6) is 5.6 pg·mL-1 which is considerably lower than previous reports. This assay provides a universal sensing platform and has great potential for determination of various analytes, including small molecules, proteins, DNA, and cells. Graphical abstract Schematic representation of the bio-barcode triggered exponential amplification reaction (EXPAR) for a fluorometric competitive immunoassay for abrin. The limit of detection is 5.6 pg mL-1 with a large dynamic range from 10 pg mL-1 to 1 µg mL-1.

Highly selective enrichment of phosphorylated proteins by using Spore@Fe3+ microspheres.

The advantages of spore-based microspheres include high monodispersity, presence of different functional groups (carboxylic, amino, and hydroxyl groups), facile industrial-scale preparation by using cell cultures via fermentation in a potentially cost effective and environment friendly manner, and high uniformity. We developed a novel spore@Fe3+ microsphere for specific capture of phosphoproteins. Caseins (α-casein and ß-casein) as phosphoproteins were used to evaluate binding capacity and enrichment factor. The spore@Fe3+ microspheres demonstrate high binding capacity and selectivity for phosphoproteins (1983 and 1818 mg g-1 for α-casein and ß-casein, respectively). A mixture of bovine serum albumin and ß-casein at 100:1 ratio displayed an enrichment factor higher than 173-fold, which can nearly be considered "purification" of phosphoproteins. The proposed method is a promising technique in developing more selective, rapid, low cost, and high-throughput platforms for phosphoprotein enrichment, and it presents potential application in investigation of protein functions and in personalized diagnostic tests.

Self-Assembled Ti4+@Biospore Microspheres for Sensitive DNA Analysis.

Ti4+ can be chemically adsorbed and assembled on the surface of the modified spore to form highly monodispersed Ti4+@spore microspheres. Moreover, we for the first time found that these biomicrospheres exhibit differential affinities toward ssDNA and dsDNA. As a principle-of-proof, we exploited the self-assembled Ti4+@spore microspheres for a hybridization analysis. Interestingly, in the hybridization analysis, residual ssDNA probes are selectively adsorbed on Ti4+@spore microspheres at pH 5.0 and then removed via centrifugation. By taking advantage of this property, the signal-to-noise ratio for DNA analysis was considerably increased by reducing the noise caused by the residual ssDNA probes. The proposed method features easy operation, high specificity, and sensitivity and thus exhibits potential for further applications on DNA biosensing.

Quantum dot incorporated Bacillus spore as nanosensor for viral infection.

In this paper, we report a high-throughput biological method to prepare spore-based monodisperse microparticles (SMMs) and then form the nanocomposites of CdTe quantum dot (QD)-loaded SMMs by utilizing the endogenous functional groups from Bacillus spores. The SMMs and QD-incorporated spore microspheres (QDSMs) were characterized by using transmission electron microscopy, high-resolution transmission electron microscopy, fluorescence microscopy, fluorescence and UV-visible absorption spectroscopy, zeta potential analysis, Fourier-transform infrared spectroscopy, potentiometric titrations, X-ray photo-electron spectroscopy. The thermodynamics of QD/SMM interaction and antigen/QDSM interaction was also investigated by isothermal titration microcalorimetry (ITC). Fluorescent QDSMs coded either with a single luminescence color or with multiple colors of controlled emission intensity ratios were obtained. Green QDSMs were used as a model system to detect porcine parvovirus antibody in swine sera via flow cytometry, and the results demonstrated a great potential of QDSMs in high-throughput immunoassays. Due to the advantages such as simplicity, low cost, high throughput and eco-friendliness, our developed platform may find wide applications in disease detection, food safety evaluation and environmental assessment.

Sustainable endospore-based microreactor system for antioxidant capacity assay.

A novel endospore-based microbial method for "post-additional" antioxidant capacity assay was developed. The technique was based on oxidation and catalysis of the 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) by Bacillus subtilis 168 endospores in the presence of dissolved oxygen. Coat protein A (CotA), which belongs to the endospore coat, was expressed, purified, and assessed for its ability to oxidize ABTS into the ABTS(•+) radical cation. The wild-type endospore necessary for oxidizing ABTS into ABTS(•+) radical cation was confirmed by knocking out the cotA gene from B. subtilis 168 by homologous double exchange. Findings revealed that the catalytic activity of the endospores may be attributed to the presence of the CotA protein. The use of endospores instead of purified enzymes to prepare ABTS(•+) greatly reduced the assay cost and eliminated the need to purify and store of enzymes. The self-life of the radical cation was kept stable for at least 12 days without addition of a stabilizer and laccase inhibitor. This behavior enables the large-scale preparation of ABTS(•+). The antioxidant capacities of the individual antioxidants and fruit samples were easily quantified and compared using the proposed method. The developed technique can be further developed as a high-throughput screening technique for antioxidants.

Sensitive chemiluminescence immunoassay for E. coli O157:H7 detection with signal dual-amplification using glucose oxidase and laccase.

A novel, sensitive chemiluminescence (CL) immunoassay for Escherichia coli O157:H7 detection with signal dual-amplification using glucose oxidase (GOx) and laccase was investigated. The method was based on the characterization of a luminol-H2O2-laccase reaction. Compared with the horseradish peroxidase-based biosensor, laccase exhibited high catalytic activity in strong alkaline medium, which was compatible with the luminol system. The capture antibody was immobilized onto the magnetic bead (MB) surfaces. The detection antibody was linked with GOx through biotin-avidin recognition. Accordingly, the bioconjugation of MB-caputure antibody- E. coli O157:H7-detection antibody-GOx catalyzed the substrate glucose, thereby generating H2O2. E. coli O157:H7 was then detected by measuring the CL intensity after H2O2 formation. Under optimal conditions, the calibration plot obtained for E. coli O157:H7 was approximately linear from 4.3 × 10(3) colony-forming unit (CFU) mL(-1) to 4.3 × 10(5) CFU mL(-1), and the total assay time was <2.0 h without any enrichment. The limit of detection for the assay was 1.2 × 10(3) CFU mL(-1) (3σ), which was considerably lower than that of enzyme-linked immunosorbent assay method (1.0 × 10(5) CFU mL(-1)) (3σ). A series of repeatability measurements of using 1.7 × 10(4) CFU mL(-1) E. coli O157:H7 exhibited reproducible results with a relative standard deviation (RSD) of 3.5% (n = 11). Moreover, the proposed method was successfully used to detect E. coli O157:H7 in synthetic samples (spring water, apple juice, and skim milk), which indicated its potential practical application. This protocol can be applied in various fields of study.

Sensitive and selective detection of Ag+ in aqueous solutions using Fe3O4@Au nanoparticles as smart electrochemical nanosensors.

Owing to the selective deposition reaction on the surface of magnetic nanoparticles, we reported a simple and selective magnetic electrochemical method for the detection of Ag(+) ions in aqueous solutions. The analyte deposited on the nanoparticles was brought to the surface of a homemade magnetic electrode and detected electrochemically in 0.1 mol/L KCl solution based on the reaction of Ag0 transferred to AgCl. Under the optimal conditions, the linear response range of Ag(+) ions was 0.117-17.7 µmol/L (R(2)=0.9909) with a detection limit of 59 nmol/L (S/N=3). A series of repeatability measurements 1.0 µmol/L Ag(+) gave reproducible results with a relative standard deviation (RSD) of 4.5% (n=11). The interference from other metal cations can be eliminated by adding EDTA as a co-additive to mask the metal cations. The recoveries ranging from 98.6% to 103.99% after standard additions demonstrate that this sensor has great potential in practical applications. The advantages of this developed method include remarkable simplicity, low cost, and no requirement for probe preparation, among others.