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Conductive polylactic-acid filament for dose monitoring in syringe-less wearable infusion pump
Jeon, Sangbin,Chua, Beelee Elsevier 2018 Sensors and actuators. B Chemical Vol.258 No.-
<P><B>Abstract</B></P> <P>We have demonstrated the use of conductive polylactic acid (PLA) filament for dose monitoring in a syringe-less wearable infusion pump. A channel reservoir is inlaid with conductive PLA filament. As the liquid medium is dispensed via gas pressurization by an built-in electrolysis chamber, the effective impedance of the conductive PLA filament/liquid medium column changes as well. This allows the dispensed volume to be monitored via the output voltage across a series resistor. Using 5V sinusoidal input voltage, the output voltage decreased from ∼1.3 to ∼0.13V as the dispensed volume of 0.1mol/L PBS increased from 0 to 1000μL. Similarly, the output voltage for insulin analog decreased from ∼0.64 to 0.126V for the same volume displaced. Repeated dispensing runs with 0.1mol/L PBS showed good consistency (standard deviation less than 10mV). The rate of change of the output voltage with elapsed time varied accordingly for the different flow rates (0.25–1.00mL/h or ∼4–17μL/min). At electrolysis voltages of 1.5 and 5V, the respective output voltage were 1.04 and 0.33V. These corresponded to flow rates of ∼3 and 10mL/h (∼50 and 160μL/min).</P> <P><B>Highlights</B></P> <P> <UL> <LI> We demonstrated the use of conductive PLA filament as a low cost and disposable dose monitoring method. </LI> <LI> Dose monitoring is achieved via the combined impedance change of the conductive PLA filament/liquid medium column. </LI> <LI> It allows syringe-less dispensing methods to be used in wearable infusion pumps. </LI> <LI> Size profile limitation by the use of syringe-based dispensing methods is circumvented. </LI> <LI> Contributes to the realization of ultra-low size profile insulin pumps. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Detection of Cyanobacteria in Eutrophic Water Using a Portable Electrocoagulator and NanoGene Assay
Lee, Eun-Hee,Chua, Beelee,Son, Ahjeong American Chemical Society 2018 Environmental science & technology Vol.52 No.3
<P>We have demonstrated the detection of cyanobacteria in eutrophic water samples using a portable electrocoagulator and NanoGene assay. The electrocoagulator is designed to preconcentrate cyanobacteria from water samples prior to analysis via NanoGene assay. Using <I>Microcystis aeruginosa</I> laboratory culture and environmental samples (cell densities ranging from 1.7 × 10<SUP>5</SUP> to 4.1 × 10<SUP>6</SUP> and 6.5 × 10<SUP>3</SUP> to 6.6 × 10<SUP>7</SUP> cells·mL<SUP>–1</SUP>, respectively), the electrocoagulator was evaluated and compared with a conventional centrifuge. Varying the operation duration from 0 to 300 s with different cell densities was first investigated. Preconcentration efficiencies (obtained via absorbance measurement) and dry cell weight of preconcentrated cyanobacteria were then obtained and compared. For laboratory samples at cell densities from 3.2 × 10<SUP>5</SUP> to 4.1 × 10<SUP>6</SUP> cells·mL<SUP>–1</SUP>, the preconcentration efficiencies of electrocoagulator appeared to be stable at ∼60%. At lower cell densities (1.7 and 2.2 × 10<SUP>5</SUP> cells·mL<SUP>–1</SUP>), the preconcentration efficiencies decreased to 33.9 ± 0.2 and 40.4 ± 5.4%, respectively. For environmental samples at cell densities of 2.7 × 10<SUP>5</SUP> and 6.6 × 10<SUP>7</SUP> cells·mL<SUP>–1</SUP>, the electrocoagulator maintained its preconcentration efficiency at ∼60%. On the other hand, the centrifuge’s preconcentration efficiencies decreased to nondetectable and below 40%, respectively. This shows that the electrocoagulator outperformed the centrifuge when using eutrophic water samples. Finally, the compatibility of the electrocoagulator with the NanoGene assay was verified via the successful detection of the microcystin synthetase D (<I>mcyD</I>) gene in environmental samples. The viability of the electrocoagulator as an in situ compatible alternative to the centrifuge is also discussed.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2018/esthag.2018.52.issue-3/acs.est.7b05055/production/images/medium/es-2017-05055w_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es7b05055'>ACS Electronic Supporting Info</A></P>
Detection of bisphenol A using palm-size NanoAptamer analyzer
Lim, Hyun Jeong,Chua, Beelee,Son, Ahjeong Elsevier Applied Science 2017 Biosensors & bioelectronics Vol. No.
<P><B>Abstract</B></P> <P>We have demonstrated a palm-size NanoAptamer analyzer capable of detecting bisphenol A (BPA) at environmentally relevant concentrations (<1ng/mL or ppb). It is designed for performing reaction and fluorescence measurement on single cuvette sample. Modified NanoGene assay was used as the sensing mechanism where signaling DNA and QD<SUB>655</SUB> was tethered to QD<SUB>565</SUB> and magnetic bead via the aptamer. Aptamer affinity with BPA resulted in the release of the signaling DNA and QD<SUB>655</SUB> from the complex and hence corresponding decrease in QD<SUB>655</SUB> fluorescence measurement signal. Baseline characterization was first performed with empty cuvettes, quantum dots and magnetic beads under near-ideal conditions to establish essential functionality of the NanoAptamer analyzer. Duration of incubation time, number of rinse cycles, and necessity of cuvette vibration were also investigated. In order to demonstrate the capability of the NanoAptamer analyzer to detect BPA, samples with BPA concentrations ranging from 0.0005 to 1.0ng/mL (ppb) were used. The performance of the NanoAptamer analyzer was further examined by using laboratory protocol and commercial spectrofluorometer as reference. Correlation between NanoAptamer analyzer and laboratory protocol as well as commercial spectrofluorometer was evaluated via correlation plots and correlation coefficients.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Palm-size NanoAptamer analyzer for bisphenol A detection in environmentally relevant concentration. </LI> <LI> Based on modified NanoGene assay using magnetic beads, quantum dots and bisphenol A specific aptamer. </LI> <LI> Employs on-system vibrating motor, articulated magnet, LED array and photodiodes. </LI> <LI> Results from NanoAptamer analyzer well-correlated with laboratory protocol. </LI> </UL> </P>
Park, Miri,Son, Ahjeong,Chua, Beelee Elsevier 2018 Sensors and actuators. B, Chemical Vol.276 No.-
<P><B>Abstract</B></P> <P>In this paper, we have demonstrated the feasibility of using microorganism-ionizing respirators with reduced breathing resistance to remove airborne bacteria. Using a miniaturized corona ionizer and two pairs of separator electrodes, airborne bacteria were ionized and removed from the airflow. Two microorganism-ionizing respirator designs were experimentally evaluated with flow rates ranging from ∼10 to 20 L/min and yielded airborne bacterial removal efficiencies of ∼75%–100%. Further, they were in close agreement with the analytical airborne particle removal efficiencies, at a similar range of flow rates. These flow rates also correspond to the breathing rates of standing and walking adults. More importantly, the breathing resistance could be reduced by more than 50% for flow rates of ∼200 L/min. Using manganese (IV) oxide coated mesh, the ozone concentration in the air outflow was reduced to less than 0.1 ppm, at a flow rate of ∼20 L/min, thus enabling safe use. The power consumption was less than 1 W.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We demonstrated the ability of microorganisms ionizing respirator to remove airborne bacteria. </LI> <LI> It uses miniaturized corona ionizer and separator electrodes. </LI> <LI> Airborne bacteria was electrically charged and removed from air flow. </LI> <LI> Its breathing resistance was less than that of commercial N95 respirator. </LI> <LI> Contributes to the comfort and ease of breathing of the wearer. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>