Surface charge, electroosmotic flow and DNA extension in chemically modified thermoplastic nanoslits and nanochannels

Uba, Franklin I.,Pullagurla, Swathi R.,Sirasunthorn, Nichanun,Wu, Jiahao,Park, Sunggook,Chantiwas, Rattikan,Cho, Yoon-Kyoung,Shin, Heungjoo,Soper, Steven A. The Royal Society of Chemistry 2015 The Analyst Vol.140 No.1

<P>Thermoplastics have become attractive alternatives to glass/quartz for microfluidics, but the realization of thermoplastic nanofluidic devices has been slow in spite of the rather simple fabrication techniques that can be used to produce these devices. This slow transition has in part been attributed to insufficient understanding of surface charge effects on the transport properties of single molecules through thermoplastic nanochannels. We report the surface modification of thermoplastic nanochannels and an assessment of the associated surface charge density, zeta potential and electroosmotic flow (EOF). Mixed-scale fluidic networks were fabricated in poly(methylmethacrylate), PMMA. Oxygen plasma was used to generate surface-confined carboxylic acids with devices assembled using low temperature fusion bonding. Amination of the carboxylated surfaces using ethylenediamine (EDA) was accomplished <I>via</I> EDC coupling. XPS and ATR-FTIR revealed the presence of carboxyl and amine groups on the appropriately prepared surfaces. A modified conductance equation for nanochannels was developed to determine their surface conductance and was found to be in good agreement with our experimental results. The measured surface charge density and zeta potential of these devices were lower than glass nanofluidic devices and dependent on the surface modification adopted, as well as the size of the channel. This property, coupled to an apparent increase in fluid viscosity due to nanoconfinement, contributed to the suppression of the EOF in PMMA nanofluidic devices by an order of magnitude compared to the micro-scale devices. Carboxylated PMMA nanochannels were efficient for the transport and elongation of λ-DNA while these same DNA molecules were unable to translocate through aminated nanochannels.</P> <P>Graphic Abstract</P><P>We report the surface modification of thermoplastic nanochannels and the evaluation of the surface charge density, zeta potential and electroosmotic flow (EOF). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4an01439a'> </P>

Impact of hydroxyethyl starch 70/0.5 on acute kidney injury after gastroenterological surgery

Takeshi Umegaki,Takeo Uba,Chisato Sumi,Sachiyo Sakamoto,Sachiko Jomura,Kiichi Hirota,Koh Shingu 대한마취통증의학회 2016 Korean Journal of Anesthesiology Vol.69 No.5

Background: Previous studies reported a higher mortality risk and a greater need for renal replacement therapy in patients administered hydroxyethyl starch (HES) rather than other fluid resuscitation preparations. In this study, we investigated the association between 6% HES 70/0.5 use and postoperative acute kidney injury (AKI) in gastroenterological surgery patients. Methods: We conducted retrospective full-cohort and propensity-score-based analyses of patients who underwent gastroenterological surgery between June 2011 and August 2013 in a Japanese university hospital. The study sample comprised 66 AKI and 2,152 non-AKI patients in the full-cohort analysis and 35 AKI and 1,269 non-AKI patients in the propensity-score-based analysis. Propensity scores were calculated using an ordered logistic regression model in which the dependent variable comprised three groups based on HES infusion volumes (0, 1–999, and ≥ 1,000 ml). The association between HES groups and postoperative AKI incidence was analyzed using multiple logistic regression models. Other candidate independent variables included patient characteristics and intraoperative measures. Results: In the full-cohort analysis, 40 (60.6%) AKI patients were diagnosed as “risk,” 15 (22.7%) as “injury,” and 11 (16.7%) as “failure.” In the propensity-score-based analysis, the corresponding values were 22 (62.9%), 8 (22.9%), and 5 (14.3%). There was no significant association between total infused HES and postoperative AKI incidence in either the full-cohort or the propensity-score-based analysis (P = 0.168 and P = 0.42, respectively). Conclusions: AKI incidence was not associated with clinical 6% HES 70/0.5 administration in gastroenterological surgery patients treated at a single center.

Optimization of Process Variables for the Soda Pulping of Carpolobia Lutea (Polygalaceae) G. Don

Ogunsile, B.O.,Uba, F.I. Korean Chemical Society 2012 대한화학회지 Vol.56 No.2

The selection of suitable delignification conditions and optimization of process variables is crucial to the successful operation of chemical pulping processes. Soda pulping of Carpolobia lutea was investigated, as an alternative raw material for pulp and paper production. The process was optimized under the influence of three operational variables, namely, temperature, time and concentration of cooking liquor. Equations derived using a second - order polynomial design predicted the pulp yield and lignin dissolution with errors less than 8% and 11% respectively. The maximum variations in the pulp yield using a second order factorial design was caused by changes in both time and alkali concentration. Optimum pulp yield of 43.87% was obtained at low values of the process variables. The selectivity of lignin dissolution was independent of the working conditions, allowing quantitative estimations to be established between the pulp yield and residual lignin content within the range studied.

Immobilization of Lambda Exonuclease onto Polymer Micropillar Arrays for the Solid-Phase Digestion of dsDNAs

Oliver-Calixte, Nyoté,J.,Uba, Franklin I.,Battle, Katrina N.,Weerakoon-Ratnayake, Kumuditha M.,Soper, Steven A. American Chemical Society 2014 ANALYTICAL CHEMISTRY - Vol.86 No.9

<P>The process of immobilizing enzymes onto solid supports for bioreactions has some compelling advantages compared to their solution-based counterpart including the facile separation of enzyme from products, elimination of enzyme autodigestion, and increased enzyme stability and activity. We report the immobilization of λ-exonuclease onto poly(methylmethacrylate) (PMMA) micropillars populated within a microfluidic device for the on-chip digestion of double-stranded DNA. Enzyme immobilization was successfully accomplished using 3-(3-dimethylaminopropyl) carbodiimide/<I>N</I>-hydroxysuccinimide (EDC/NHS) coupling to carboxylic acid functionalized PMMA micropillars. Our results suggest that the efficiency for the catalysis of dsDNA digestion using λ-exonuclease, including its processivity and reaction rate, were higher when the enzyme was attached to a solid support compared to the free solution digestion. We obtained a clipping rate of 1.0 × 10<SUP>3</SUP> nucleotides s<SUP>–1</SUP> for the digestion of λ-DNA (48.5 kbp) by λ-exonuclease. The kinetic behavior of the solid-phase reactor could be described by a fractal Michaelis–Menten model with a catalytic efficiency nearly 17% better than the homogeneous solution-phase reaction. The results from this work will have important ramifications in new single-molecule DNA sequencing strategies that employ free mononucleotide identification.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2014/ancham.2014.86.issue-9/ac5002965/production/images/medium/ac-2014-002965_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac5002965'>ACS Electronic Supporting Info</A></P>

Low-temperature synthesis and characterization of porous chromium terephthalate MIL-101(Cr) and its photocatalytic degradation of phenanthrene

Adamu Usman Abubakar,Abu Bakar Noor Hana Hanif,Zango Zakariyya Uba,Sambudi Nonni Soraya,Iqbal Anwar,Hussin Mohd Hazwan,Hamidon Tuan Sherwyn 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.9

Low-temperature hydrothermal technique was employed for the synthesis of highly porous and crystalline MIL-101(Cr) metal-organic frameworks series. The resulting as-synthesized MOFs were characterized by Fourier transform infrared (FTIR) spectroscopy, powdered X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption analysis, thermogravimetric analysis (TGA), photoluminescence (PL) spectroscopy, and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. The photocatalytic activity of the MOFs was evaluated for degradation of phenanthrene (PHE) under visible light irradiation. Among the MOFs, MIL-101@160 has the highest Brunner Emmett-Teller (BET) specific surface area and corresponding pore volume of 2,592.2 m2g−1 and 1.09 cm3g−1, respectively. Furthermore, it has shown higher photocatalytic degradation of the PHE than other samples with 98% degradation efficiency achieved within 150 minutes.

Recent progress in the preparation, characterization, and applications of modified halloysite nanotubes as adsorbents for wastewater treatment

Garba Zaharaddeen Nasiru,Haruna Abdurrashid,Tanimu Abdulkadir,Bello Binta Zakari,Zango Zakariyya Uba 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.6

The application of halloysite nanotubes (HNTs) in water purification is attracting extensive attention because they are inexpensive raw materials with a hollow nanotubular structure in the sub-micrometer range, a large specific surface area, pore volume, pore size, and adequate hydroxyl groups on their surface, thus enhancing their ability to be modified. These modified halloysite nanotubes (m-HNTs) have been widely used for a variety of applications, including chemocatalysis, biocatalysis, antibacterial action, drug delivery, gas separation, and adsorbents for wastewater treatment. They were reported to have been produced using a variety of synthetic processes which include self-assembly/vacuum filtering, extraction, solution casting, dehydration condensation, thermal polycondensation, chemical vapor deposition, and hydrothermal carbonization. In this review, we focus on the compilation of the most recent developments in the manufacture of m-HNTs, their characterization and possible uses in wastewater treatment. Finally, we present our personal views on the opportunities and challenges of future researches involving m-HNTs, hoping to inspire more researchers into participating in this fascinating area.