Multiple semi-quantitative colorimetric assays in compact embeddable microfluidic cloth-based analytical device (mu CAD) for effective point-of-care diagnostic

Cotton fabric is proposed as an alternative material for low-cost point-of-care devices. Cotton fabrics are vastly available, low cost and flexible. Simple wax patterning method was applied to create hydrophilic channels in cotton fabric. Three-dimensional (3D) colorimetric microfluidic device was made by folding 2D pattern along certain predefined lines. Three-dimensional devices show better mixing uniformity between reagents and analyte across the detection zones. On-chip colorimetric calibration is also proposed by putting predefined serially diluted samples next to the detection zones. Multiple assays can be integrated within a small surface area by stacking layers of individual assay device separated by a wax-impregnated fabric. We were able to detect glucose, nitrite and protein having concentration as low as 0.5 mM, 30 μM and 0.8 mg/mL, respectively, by bare eyes. Results of the assays from an unknown analyte sample and precalibrated serially diluted sample standards were displayed in a side-by-side configuration, and the interference of each analyte on the other reaction zones was investigated. These results are better than if the detection is merely taken from the calibration curve without integrated standard calibration. The mechanical durability, robustness and flexibility of 3D microfluidic cloth-based analytical device (μCAD) also make it easily embeddable to daily wearable product. We demonstrated multiple single-step qualitative assays using embedded 3D μCAD and propose a new concept of “point-of-sampling diagnostic”

Active Packaging of Immobilized Zinc Oxide Nanoparticles Controls Campylobacter jejuni in Raw Chicken Meat

Zinc oxide nanoparticles (ZnO NPs) are regarded as a safe and stable antimicrobial that can inactivate bacteria by several potential working mechanisms. We aimed to incorporate ZnO NPs into packaging material to control Campylobacter in raw chicken meat. ZnO NPs were first incorporated into three-dimensional (3D) paper tubes to identify the lethal concentration against Campylobacter jejuni, which was selected as the working concentration to develop 2D functionalized absorbing pads by an ultrasound-assisted dipping technique. The functionalized pad was placed underneath raw chicken meat to inactivate C. jejuni and the predominant chicken microbiota at 4&deg;C within 8 days of storage. Immobilized ZnO NPs at 0.856&thinsp;mg/cm2 reduced C. jejuni from &sim;4 log CFU/25 g raw chicken meat to an undetectable level after 3 days of storage. Analysis by inductively coupled plasma-optical emission spectroscopy showed that the Zn level increased from 0.02 to 0.17&thinsp;mg/cm2 in treated raw chicken meat. Scanning electron microscopy validated the absence of nanoparticle migration onto raw chicken meat after treatment. Inactivation of C. jejuni was associated with the increase of lactic acid produced by Lactobacillus in raw chicken meat in a pH-dependent manner. Less than 5% of Zn2+ was released from ZnO NPs at neutral pH, while up to 88% was released when the pH was &lt;3.5 within 2 days. Whole-transcriptome sequencing (RNA-Seq) analysis demonstrated a broad effect of ZnO NPs on genes involved in various cellular developmental processes as annotated by gene ontology. Taken together, the results indicate that functionalized absorbing pads inactivated C. jejuni in raw chicken meat by immobilized ZnO NPs along with the controllable released Zn2+.IMPORTANCE Prevalence of Campylobacter in raw poultry remains a major food microbiological safety challenge. Novel mitigation strategies are required to ensure the safety and quality of poultry products. Active food packaging can control pathogens without directly adding antimicrobials into the food matrix and extend the food&rsquo;s shelf life. The functionalized absorbing pad with ZnO NPs developed in this study was able to inactivate C. jejuni in raw chicken meat and keep the meat free from C. jejuni contamination during shelf life without any observed migration of nanoparticles. The controllable conversion of immobilized ZnO NPs to free Zn2+ makes this approach safe and eco-friendly and paves the way for developing a novel intervention strategy for other high-risk foods. Our study applied nanotechnology to exploit an effective approach for Campylobacter control in raw chicken meat products.</jats:p

&quot;Periodic-table-style&quot; paper device for monitoring heavy metals in water

If a paper-based analytical device (mu-PAD) could be made by printing indicators for detection of heavy metals in chemical symbols of the metals in a style of the periodic table of elements, it could be possible for such mu-PAD to report the presence and the safety level of heavy metal ions in water simultaneously and by text message. This device would be able to provide easy solutions to field-based monitoring of heavy metals in industrial wastewater discharges and in irrigating and drinking water. Text-reporting could promptly inform even nonprofessional users of the water quality. This work presents a proof of concept study of this idea. Cu(II), Ni(II), and Cr(VI) were chosen to demonstrate the feasibility, specificity, and reliability of paper-based text-reporting devices for monitoring heavy metals in water

Surface modification of cellulose paper for quantum dot-based sensing applications

Cellulose paper specimens with and without surface modification were compared in order to study their physicochemical compatibility with quantum dots (QDs) for biochemical sensing applications. Silane and chitosan modification methods were applied. The distribution of QDs deposited on untreated paper and papers modified with silane and chitosan were investigated in order to understand the interaction between QDs and fibre. Modified papers were shown to significantly reduce the undesirable redistribution of QDs during paper drying. The retention ability and thermal resistance of QDs to the loss of fluorescence on modified papers were also studied for the purpose of determining the most suitable paper surface modification for developing QD-Paper-based analytical devices (QD-PADs). Furthermore, chitosan-modified paper was used to design QD-PADs to quantify glucose concentration in aqueous samples; the quenching effect of the enzymatic product on the fluorescent emission of QDs was used as the indicator system. The change of fluorescence of QDs was measured by a simple in-house constructed fluorescence imaging system. The detection limit of glucose was 5 mg/dL, which is comparable with other reported paper sensors for detection of glucose

Bilayer graphene nanoribbon mobility model in ballistic transport limit

Bilayer graphene nanoribbon (BGN) with tunable band gap which can be controlled by an external electric field is focused in our study. AB-stacked system with a stable structure is considered in a FET channel. Based on the assumed structure carrier density effect on charge mobility has been reported at different temperatures. Carrier mobility model is explained based on quantum confinement effect which indicates that carriers behave like traveling wave only in channel direction. Their behavior in other two directions can be approximated by standing wave as well. We prove that carrier mobility in BGNs is a function of temperature and carrier density which illustrate good agreement with experimental data