Controlling “chemical nose” biosensor characteristics by modulating gold nanoparticle shape and concentration

Verma, M. S., Chen, P. Z., Jones, L., & Gu, F. X. (2015). Controlling “chemical nose” biosensor characteristics by modulating gold nanoparticle shape and concentration. Sensing and Bio-Sensing Research, 5, 13–18. https://doi.org/10.1016/j.sbsr.2015.04.007Conventional lock-and-key biosensors often only detect a single pathogen because they incorporate biomolecules with high specificity. “Chemical nose” biosensors are overcoming this limitation and identifying multiple pathogens simultaneously by obtaining a unique set of responses for each pathogen of interest, but the number of pathogens that can be distinguished is limited by the number of responses obtained. Herein, we use a gold nanoparticle-based “chemical nose” to show that changing the shapes of nanoparticles can increase the number of responses available for analysis and expand the types of bacteria that can be identified. Using four shapes of nanoparticles (nanospheres, nanostars, nanocubes, and nanorods), we demonstrate that each shape provides a unique set of responses in the presence of different bacteria, which can be exploited for enhanced specificity of the biosensor. Additionally, the concentration of nanoparticles controls the detection limit of the biosensor, where a lower concentration provides better detection limit. Thus, here we lay a foundation for designing “chemical nose” biosensors and controlling their characteristics using gold nanoparticle morphology and concentration

Branching and size of CTAB-coated gold nanostars control the colorimetric detection of bacteria

Rapid detection of pathogenic bacteria is challenging because conventional methods require long incubation times. Nanoparticles have the potential to detect pathogens before they can cause an infection. Gold nanostars have recently been used for colorimetric biosensors but they typically require surface modification with antibodies or aptamers for cellular detection. Here, CTAB-coated gold nanostars have been used to rapidly (<5 min) detect infective doses of a model Gram-positive pathogen Staphylococcus aureus by an instrument-free colorimetric method. Varying the amounts of gold nanoseed precursor and surfactant can tune the size and degree of branching of gold nanostars as studied here by transmission electron microscopy. The size and morphology of gold nanostars determine the degree and rate of color change in the presence of S. aureus. The optimal formulation achieved maximum color contrast in the presence of S. aureus and produced a selective response in comparison to polystyrene microparticles and liposomes. These gold nanostars were characterized using UV-Visible spectroscopy to monitor changes in their surface plasmon resonance peaks. The visual color change was also quantified over time by measuring the RGB components of the pixels in the digital images of gold nanostar solutions. CTAB-coated gold nanostars serve as a promising material for simple and rapid detection of pathogens.This work was financially supported by the Natural Sciences and Engineering Research Council of Canada (NSERC)and 20/20 NSERC Ophthalmic Materials Network.M. S. Verma is grateful for the NSERC Vanier Canada Graduate Scholarship.P. Z. Chen is thankful for the NSERC Undergraduate Student Research Award

Heterogeneity in transmissibility and shedding SARS-CoV-2 via droplets and aerosols

Background: Which virological factors mediate overdispersion in the transmissibility of emerging viruses remains a longstanding question in infectious disease epidemiology. Methods: Here, we use systematic review to develop a comprehensive dataset of respiratory viral loads (rVLs) of SARS-CoV-2, SARS-CoV-1 and influenza A(H1N1)pdm09. We then comparatively meta-analyze the data and model individual infectiousness by shedding viable virus via respiratory droplets and aerosols. Results: The analyses indicate heterogeneity in rVL as an intrinsic virological factor facilitating greater overdispersion for SARS-CoV-2 in the COVID-19 pandemic than A(H1N1)pdm09 in the 2009 influenza pandemic. For COVID-19, case heterogeneity remains broad throughout the infectious period, including for pediatric and asymptomatic infections. Hence, many COVID-19 cases inherently present minimal transmission risk, whereas highly infectious individuals shed tens to thousands of SARS-CoV-2 virions/min via droplets and aerosols while breathing, talking and singing. Coughing increases the contagiousness, especially in close contact, of symptomatic cases relative to asymptomatic ones. Infectiousness tends to be elevated between 1-5 days post-symptom onset. Conclusions: Intrinsic case variation in rVL facilitates overdispersion in the transmissibility of emerging respiratory viruses. Our findings present considerations for disease control in the COVID-19 pandemic as well as future outbreaks of novel viruses.</p

Amplitude Analysis of the Decays η′→π+π−π0\eta^\prime \rightarrow \pi^+\pi^-\pi^0 and η′→π0π0π0\eta^\prime \rightarrow \pi^0\pi^0\pi^0

Based on a sample of $1.31 \times 10^9$ $J/\psi$ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays $\eta^\prime \rightarrow \pi^+\pi^-\pi^0$ and $\eta^\prime \rightarrow \pi^0\pi^0\pi^0$ is performed. A significant $P$-wave contribution from $\eta^\prime \rightarrow \rho^{\pm} \pi^{\mp}$ is observed for the first time in $\eta^\prime \rightarrow \pi^+\pi^-\pi^0$. The branching fraction is determined to be ${\mathcal B}(\eta^\prime \rightarrow \rho^{\pm}\pi^{\mp})=(7.44\pm0.60\pm1.26\pm1.84)\times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant $S$-wave component, there is a significant $\sigma$ meson component. The branching fractions of the combined $S$-wave components are determined to be ${\mathcal B}(\eta^\prime \rightarrow \pi^+\pi^-\pi^0)_S=(37.63\pm0.77\pm2.22\pm4.48)\times 10^{-4}$ and ${\mathcal B}(\eta^\prime \rightarrow \pi^0\pi^0\pi^0)=(35.22\pm0.82\pm2.54)\times 10^{-4}$, respectively. The latter one is consistent with previous BESIII measurements.Comment: 7 pages, 3 figure

Targeted nanoparticle binding & detection in petroleum hydrocarbon impacted porous media

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.chemosphere.2018.10.046 © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Targeted nanoparticle binding has become a core feature of experimental pharmaceutical product design which enables more efficient payload delivery and enhances medical imaging by accumulating nanoparticles in specific tissues. Environmental remediation and geophysical monitoring encounter similar challenges which may be addressed in part by the adoption of targeted nanoparticle binding strategies. This study illustrates that engineered nanoparticles can bind to crude oil-impacted silica sand, a selective adsorption driven by active targeting based on an amphiphilic polymer coating. This coating strategy resulted in 2 mg/kg attachment to clean silica sand compared to 8 mg/kg attachment to oil-impacted silica sand. It was also shown that modifying the surface coating influenced the binding behaviour of the engineered nanoparticles – more hydrophobic polymers resulted in increased binding. Successful targeting of Pluronic-coated iron oxide nanoparticles to a crude oil and silica sand mixture was demonstrated through a combined quantitative Orbital Emission Spectroscopy mass analysis supported by Vibrating Scanning Magnetometer magnetometry, and a qualitative X-ray micro-computed tomography (CT) visualization approach. These non-destructive characterization techniques facilitated efficient analysis of nanoparticles in porous medium samples with minimal sample preparation, and in the case of X-Ray CT, illustrated how targeted nanoparticle binding may be used to produce 3-D images of contaminated porous media. This work demonstrated successful implementation of nanoparticle targeted binding toward viscous LNAPL such as crude oil in the presence of a porous medium, a step which opens the door to successful application of targeted delivery technology in environmental remediation and monitoring.Natural Sciences and Engineering Research Council of Canad

Brownian markets

Financial market dynamics is rigorously studied via the exact generalized Langevin equation. Assuming market Brownian self-similarity, the market return rate memory and autocorrelation functions are derived, which exhibit an oscillatory-decaying behavior with a long-time tail, similar to empirical observations. Individual stocks are also described via the generalized Langevin equation. They are classified by their relation to the market memory as heavy, neutral and light stocks, possessing different kinds of autocorrelation functions

Disparities and risks of sexually transmissible infections among men who have sex with men in China: a meta-analysis and data synthesis.

BACKGROUND: Sexually transmitted infections (STIs), including Hepatitis B and C virus, are emerging public health risks in China, especially among men who have sex with men (MSM). This study aims to assess the magnitude and risks of STIs among Chinese MSM. METHODS: Chinese and English peer-reviewed articles were searched in five electronic databases from January 2000 to February 2013. Pooled prevalence estimates for each STI infection were calculated using meta-analysis. Infection risks of STIs in MSM, HIV-positive MSM and male sex workers (MSW) were obtained. This review followed the PRISMA guidelines and was registered in PROSPERO. RESULTS: Eighty-eight articles (11 in English and 77 in Chinese) investigating 35,203 MSM in 28 provinces were included in this review. The prevalence levels of STIs among MSM were 6.3% (95% CI: 3.5-11.0%) for chlamydia, 1.5% (0.7-2.9%) for genital wart, 1.9% (1.3-2.7%) for gonorrhoea, 8.9% (7.8-10.2%) for hepatitis B (HBV), 1.2% (1.0-1.6%) for hepatitis C (HCV), 66.3% (57.4-74.1%) for human papillomavirus (HPV), 10.6% (6.2-17.6%) for herpes simplex virus (HSV-2) and 4.3% (3.2-5.8%) for Ureaplasma urealyticum. HIV-positive MSM have consistently higher odds of all these infections than the broader MSM population. As a subgroup of MSM, MSW were 2.5 (1.4-4.7), 5.7 (2.7-12.3), and 2.2 (1.4-3.7) times more likely to be infected with chlamydia, gonorrhoea and HCV than the broader MSM population, respectively. CONCLUSION: Prevalence levels of STIs among MSW were significantly higher than the broader MSM population. Co-infection of HIV and STIs were prevalent among Chinese MSM. Integration of HIV and STIs healthcare and surveillance systems is essential in providing effective HIV/STIs preventive measures and treatments. TRIAL REGISTRATION: PROSPERO NO: CRD42013003721