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Direct Extraction of Photosynthetic Electrons from Single Algal Cells by Nanoprobing System
Ryu, WonHyoung,Bai, Seoung-Jai,Park, Joong Sun,Huang, Zubin,Moseley, Jeffrey,Fabian, Tibor,Fasching, Rainer J.,Grossman, Arthur R.,Prinz, Fritz B. American Chemical Society 2010 NANO LETTERS Vol.10 No.4
<P>There are numerous sources of bioenergy that are generated by photosynthetic processes, for example, lipids, alcohols, hydrogen, and polysaccharides. However, generally only a small fraction of solar energy absorbed by photosynthetic organisms is converted to a form of energy that can be readily exploited. To more efficiently use the solar energy harvested by photosynthetic organisms, we evaluated the feasibility of generating bioelectricity by directly extracting electrons from the photosynthetic electron transport chain before they are used to fix CO<SUB>2</SUB> into sugars and polysaccharides. From a living algal cell, <I>Chlamydomonas reinhardtii</I>, photosynthetic electrons (1.2 pA at 6000 mA/m<SUP>2</SUP>) were directly extracted without a mediator electron carrier by inserting a nanoelectrode into the algal chloroplast and applying an overvoltage. This result may represent an initial step in generating “high efficiency” bioelectricity by directly harvesting high energy photosynthetic electrons.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-4/nl903141j/production/images/medium/nl-2009-03141j_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl903141j'>ACS Electronic Supporting Info</A></P>
Wet microcontact printing (µCP) for micro-reservoir drug delivery systems
Lee, Hong-Pyo,Ryu, WonHyoung IOP Publishing 2013 Biofabrication Vol.5 No.2
<P>When micro-reservoir-type drug delivery systems are fabricated, loading solid drugs in drug reservoirs at microscale is often a non-trivial task. This paper presents a simple and effective solution to load a small amount of drug solution at microscale using 'wet' microcontact printing (?CP). In this wet ?CP, a liquid solution containing drug molecules (methylene blue and tetracycline HCl) dissolved in a carrier solvent was transferred to a target surface (drug reservoir) by contact printing process. In particular, we have investigated the dependence of the quantity and morphology of transferred drug molecules on the stamp size, concentration, printing times, solvent types and surfactant concentration. It was also found that the repetition of printing using a non-volatile solvent such as polyethylene glycol (PEG) as a drug carrier material actually increased the transferred amount of drug molecules in proportion to the printing times based on asymmetric liquid bridge formation. Utilizing this wet ?CP, drug delivery devices containing different quantity of drugs in micro-reservoirs were fabricated and their performance as controlled drug delivery devices was demonstrated.</P>
A Parasitic Insensitive Catheter-Based Capacitive Force Sensor for Cardiovascular Diagnosis
Jeon, Sangkuk,Lee, JiYong,Hwang, Hyunseok,Ryu, WonHyoung,Chae, Youngcheol IEEE 2018 IEEE transactions on biomedical circuits and syste Vol.12 No.4
<P>This paper presents a catheter-based capacitive force sensor interface for cardiovascular diagnosis. The force sensor is implemented on a flexible printed circuit board (FPCB) substrate with a force-sensitive polydimethylsiloxane (PDMS), and a force-induced change in a capacitance of the sensor is measured by a precision capacitive sensor interface. To recover the performance degradation caused by the large parasitic capacitance <TEX>${\rm C}_{\rm P}$</TEX> of a long catheter, we present a parasitic insensitive analog front-end (AFE) with active <TEX>${\rm C}_{\rm P}$</TEX> cancellation, which employs a charge amplifier and a negative capacitor at the virtual ground of the charge amplifier. The prototype sensor was measured with a force loader in whole blood. The proposed AFE successfully cancels <TEX>${\rm C}_{\rm P}$</TEX> of 348 pF in a 0.9-m-long sensor and measurement results show the SNR of 53.8 dB and the capacitance resolution of 16 aF, a 19.6 dB improvement by canceling nonideal effect of <TEX>${\rm C}_{\rm P}$</TEX>. This corresponds to a force resolution of 2.22 gf, which is 9.29 <TEX>$\times$</TEX> reduction compared to the work without the <TEX>${\rm C}_{\rm P}$</TEX> cancellation. The proposed sensor interface is insensitive to <TEX>${\rm C}_{\rm P}$</TEX> from hundreds to 1-nF level, and the force-dependent stiffness of two different tissues has been successfully distinguished with an <I>ex-vivo</I> experiment. The proposed sensor interface enables the integration of capacitive force sensors in a smart catheter.</P>
Controlled release of bupivacaine HCl through microchannels of biodegradable drug delivery device.
Lee, Kang Ju,Yang, Sung Yeun,Ryu, WonHyoung Kluwer Academic Publishers 2012 BIOMEDICAL MICRODEVICES Vol.14 No.3
<P>Local and prolonged delivery of local analgesics is much desired for post-operative pain management. For delivery of local analgesics at a constant rate over couple of days, a microfluidic device comprised of a drug reservoir and microchannels for drug release was developed using a biodegradable polymer, 85/15 poly(lactic-co-glycolic acid). Unlike conventional methods relying on material property, this device enables convenient modulation of the release speed of drugs by a simple change of the channel geometry such as the length and cross-sectional area. Bupivacaine was selected as our model local analgesic drug and its diffusional transport through microchannels was studied using the microfluidic devices. However, since the salt form of bupivacaine, bupivacaine hydrochloride, has pH-dependent solubility, its precipitation in microchannels had an adverse impact on the release performance of the microfluidic drug delivery devices. Thus, in this investigation, the diffusional transport and precipitation of bupivacaine hydrochloride in microfluidic channels were studied using in vitro release experiments and optical analysis. Furthermore, a concept of co-delivery of bupivacaine hydrochloride together with acidic additives was demonstrated to achieve a zero-order delivery of bupivacaine hydrochloride without the clogging of microchannels by its precipitation.</P>