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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>
Characterization of denaturation and renaturation of DNA for DNA hybridization
Xiaofang Wang,Hyun Jeong Lim,Ahjeong Son 환경독성보건학회 2014 환경독성보건학회지 Vol.29 No.-
Objectives : The present study was designed to systematically characterize the denaturation and the renaturation of double stranded DNA (dsDNA), which is suitable for DNA hybridization. Methods : A series of physical and chemical denaturation methods were implemented on well-defined 86-bp dsDNA fragment. The degree of each denaturation was measured and the most suitable denaturation method was determined. DNA renaturation tendency was also investigated for the suggested denaturation method. Results : Heating, beads mill, and sonication bath did not show any denaturation for 30 minutes. However probe sonication fully denatured DNA in 5 minutes. 1 mol/L sodium hydroxide (alkaline treatment) and 60% dimethyl sulfoxide (DMSO) treatment fully denatured DNA in 2-5 minutes. Conclusions : Among all the physical methods applied, the direct probe sonication was the most effective way to denature the DNA fragments. Among chemical methods, 60% DMSO was the most adequate denaturation method since it does not cause full renaturation during DNA hybridization.
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>