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Biosens Bioelectron ; 150: 111862, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31740256


Salmonella is the leading risk factor in food safety. Rapid, sensitive and accurate detection of Salmonella is a key to prevent and control the outbreaks of foodborne diseases caused by Salmonella. In this study, we reported a colorimetric biosensor for ultrasensitive detection of Salmonella Typhimurium using a magnetic grid separation column to efficiently separate target bacteria from large volume of sample and platinum loaded zeolitic imidazolate framework-8 (Pt@ZIF-8) nanocatalysts to effectively amplify biological signal. The target Salmonella cells in large volume of sample were first separated and concentrated using the magnetic grid separation column with immune magnetic particle chains, then conjugated with the immune Pt@ZIF-8 nanocatalysts to mimic peroxidase for catalysis of hydrogen peroxide-3,3',5,5'-tetramethylbenzidine, and finally determined by measuring the catalysate at characteristic wavelength of 450 nm. This proposed biosensor was able to separate ∼70% of target Salmonella cells from 50 mL of bacterial sample and quantitatively detect Salmonella from 101 to 104 CFU/mL in 2.5 h with the lower detection limit of 11 CFU/mL. The mean recovery for Salmonella in spiked chicken carcass was about 109.8%. This new magnetic grid separation method was first time reported for efficient separation of target bacteria from very large volume of sample to greatly improve the sensitivity of this biosensor and could be used with various biosensing assays for practical applications in routine detection of foodborne pathogens without any bacterial pre-enrichment.

Micromachines (Basel) ; 10(10)2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31557924


Separation and concentration of target bacteria has become essential to sensitive and accurate detection of foodborne bacteria to ensure food safety. In this study, we developed a bacterial separation system for continuous-flow separation and efficient concentration of foodborne bacteria from large volume using a nickel nanowire (NiNW) bridge in the microfluidic chip. The synthesized NiNWs were first modified with the antibodies against the target bacteria and injected into the microfluidic channel to form the NiNW bridge in the presence of the external arc magnetic field. Then, the large volume of bacterial sample was continuous-flow injected to the channel, resulting in specific capture of the target bacteria by the antibodies on the NiNW bridge to form the NiNW-bacteria complexes. Finally, these complexes were flushed out of the channel and concentrated in a lower volume of buffer solution, after the magnetic field was removed. This bacterial separation system was able to separate up to 74% of target bacteria from 10 mL of bacterial sample at low concentrations of ≤102 CFU/mL in 3 h, and has the potential to separate other pathogenic bacteria from large volumes of food samples by changing the antibodies.

Nanomaterials (Basel) ; 8(12)2018 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-30518091


Early screening of pathogenic bacteria is key to preventing and controlling outbreaks of foodborne diseases. In this study, protein-inorganic hybrid nanoflowers were synthesized for signal amplification and used with a calcium ion selective electrode (Ca-ISE) to establish a new enzyme-free assay for rapid and sensitive detection of Salmonella. Calcium hydrophosphate crystals were first conjugated with polyclonal antibodies against Salmonella to synthesize immune calcium nanoflowers (CaNFs), and streptavidin modified magnetic nanobeads (MNBs) were conjugated with biotinylated monoclonal antibodies against Salmonella to form immune MNBs. After target bacteria were separated using immune MNBs to form magnetic bacteria, immune CaNFs were conjugated with magnetic bacteria to form nanoflower conjugated bacteria. Then, hydrogen chloride was used to release calcium ions from nanoflower conjugated bacteria. After magnetic separation, the supernatant was finally injected as a continuous-flow to fluidic chip with Ca-ISE for specific detection of calcium ions. The supernatant's potential had a good linear relationship with bacteria concentration, and this assay was able to detect the S. Typhimurium cells as low as 28 colony forming units/mL within two hours. The mean recovery of target bacteria in spiked chicken samples was 95.0%. This proposed assay shows the potential for rapid, sensitive, and on-line detection of foodborne pathogens.

Biomed Res Int ; 2018: 7069192, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29967782


Objective: To evaluate the diagnostic ability of rs-DWI to detect subtle acute infarction lesion in the different regions of the brain in comparison to routine DWI and the comparison between different b-values. Method: 35 acute brain infarction patients were included. The subtle acute infarction lesions in ss-DWI and rs-DWI sequence were evaluated in 9 anatomical regions of the brain, and the ss-EPI DWI was also acquired with different b-values of 0, 1000, 2000, and 3000s/mm2. The McNemar test was performed for comparing the diagnostic ability of ss-DWI and rs-DWI and different b-values. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for the whole brain and in each anatomical region were calculated. Result: A total of 406 subtle acute infarction lesions were confirmed. The ss-DWI detected 338 subtle lesions, out of which 318 were true positive and 20 were false positive lesions. The rs-DWI detected 386 subtle lesions, out of which 385 were true positive lesions and 1 was true negative lesion. Sensitivity, specificity, positive predictive value, and negative predictive value in rs-DWI were better than ss-DWI in all anatomical regions of the brain. In the comparison of different b-values, b2000 was found better among b1000, b2000, and b3000. Conclusion: The rs-DWI offers a useful alternative to routine DWI for detecting the subtle acute infarctions, especially in the regions that are susceptible to distortion as in frontal cortex. In addition, high b-value can also provide benefit by increasing diffusion weighting but further raising can deteriorate image quality as SNR is decreased.

Infarto Cerebral/diagnóstico por imagem , Imagem Ecoplanar , Idoso , Encéfalo , Imagem de Difusão por Ressonância Magnética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Sensibilidade e Especificidade