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Hess, David,Rane, Anandkumar,deMello, Andrew J.,Stavrakis, Stavros American Chemical Society 2015 ANALYTICAL CHEMISTRY - Vol.87 No.9
<P>Droplet-based microfluidic systems offer a range of advantageous features for the investigation of enzyme kinetics, including high time resolution and the ability to probe extremely large numbers of discrete reactions while consuming low sample volumes. Kinetic measurements within droplet-based microfluidic systems are conventionally performed using single point detection schemes. Unfortunately, such an approach prohibits the measurement of an individual droplet over an extended period of time. Accordingly, we present a novel approach for the extensive characterization of enzyme–inhibitor reaction kinetics within a single experiment by tracking individual and rapidly moving droplets as they pass through an extended microfluidic channel. A series of heterogeneous and pL-volume droplets, containing varying concentrations of the fluorogenic substrate resorufin β-<SMALL>d</SMALL>-galactopyranoside and a constant amount of the enzyme β-galactosidase, is produced at frequencies in excess of 150 Hz. By stroboscopic manipulation of the excitation laser light and adoption of a dual view detection system, “blur-free” images containing up to 150 clearly distinguishable droplets per frame are extracted, which allow extraction of kinetic data from all formed droplets. The efficiency of this approach is demonstrated via a Michaelis–Menten analysis which yields a Michaelis constant, <I>K</I><SUB>m</SUB>, of 353 μM. Additionally, the dissociation constant for the competitive inhibitor isopropyl β-<SMALL>d</SMALL>-1-thiogalactopyranoside is extracted using the same method.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2015/ancham.2015.87.issue-9/acs.analchem.5b00766/production/images/medium/ac-2015-00766c_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac5b00766'>ACS Electronic Supporting Info</A></P>
Thermoset polyester droplet-based microfluidic devices for high frequency generation
Kim, Jin-young,deMello, Andrew J.,Chang, Soo-Ik,Hong, Jongin,O'Hare, Danny Royal Society of Chemistry 2011 Lab on a chip Vol.11 No.23
<P>The vast majority of droplet-based microfluidic devices are made from polydimethylsiloxane (PDMS). Unfortunately PDMS is not suitable for high frequency droplet generation at high operating pressure due to its low shear modulus. In this paper, we report the fabrication and testing of microfluidic devices using thermoset polyester (TPE). The optical characteristics of the fabricated devices were assessed and substrate resistance to pressure also investigated. TPE devices bonded using an O<SUB>2</SUB> plasma treated PET substrate at 76 °C were shown to function efficiently at pressures up to 18 MPa. TPE material retains many of the attractive features of PDMS such as ease of fabrication but significantly, has superior mechanical properties. The improved resistance of TPE to high pressures enabled investigation of high frequency droplet generation as a function of a wide range of flow-rates with three different oils as continuous phase.</P> <P>Graphic Abstract</P><P>Droplet-based microfluidic devices to withstand high pressure have been successfully fabricated using thermoset polyester (TPE) materials for high frequency generation of droplets. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1lc20603f'> </P>
Ding, Yun,Choo, Jaebum,deMello, Andrew J. Springer-Verlag 2017 Microfluidics and Nanofluidics Vol.21 No.3
<P>Droplet-based microfluidic technologies have proved themselves to be of significant utility in the performance of high-throughput chemical and biological experiments. By encapsulating and isolating reagents within femtoliter-nanoliter droplet, millions of (bio) chemical reactions can be processed in a parallel fashion and on ultra-short timescales. Recent applications of such technologies to genetic analysis have suggested significant utility in low-cost, efficient and rapid workflows for DNA amplification, rare mutation detection, antibody screening and next-generation sequencing. To this end, we describe and highlight some of the most interesting recent developments and applications of droplet-based microfluidics in the broad area of nucleic acid analysis. In addition, we also present a cursory description of some of the most essential functional components, which allow the creation of integrated and complex workflows based on flowing streams of droplets.</P>
Kim Jin-young,Chang Soo-Ik,deMello Andrew J,O’Hare Danny 나노기술연구협의회 2014 Nano Convergence Vol.1 No.3
In this paper, a porous polymer nanostructure has been integrated with droplet-based microfluidics in a single planar format. Monolithic porous polymer (MPP) was formed selectively within a microfluidic channel. The resulting analyte bands were sequentially comartmentalised into droplets. This device reduces band broadening and the effects of post-column dead volume by the combination of the two techniques. Moreover it offers the precise control of nano/picoliter volume samples. Background
Interfacial Tension-Mediated Droplet Fusion in Rectangular Microchannels
홍종인,최민석,Joshua B. Edel,Andrew J. deMello 한국바이오칩학회 2009 BioChip Journal Vol.3 No.3
We successfully demonstrate the merging of aqueous droplets within a microfluidic channel mediated by a difference in interfacial tension. Interfacial tension is shown to have a significant influence on the hydrodynamic forces associated with a segmented flow in a rectangular microchannel and results in the possibility of merging multiple droplets in a simple fashion. This facility is important in allowing droplet-based microfluidic systems to be used as synthetic tools in complex reaction processing.
“V-junction”: a novel structure for high-speed generation of bespoke droplet flows
Ding, Yun,Casadevall i Solvas, Xavier,deMello, Andrew The Royal Society of Chemistry 2015 The Analyst Vol.140 No.2
<P>We present the use of microfluidic “V-junctions” as a droplet generation strategy that incorporates enhanced performance characteristics when compared to more traditional “T-junction” formats. This includes the ability to generate target-sized droplets from the very first one, efficient switching between multiple input samples, the production of a wide range of droplet sizes (and size gradients) and the facile generation of droplets with residence time gradients. Additionally, the use of V-junction droplet generators enables the suspension and subsequent resumption of droplet flows at times defined by the user. The high degree of operational flexibility allows a wide range of droplet sizes, payloads, spacings and generation frequencies to be obtained, which in turn provides for an enhanced design space for droplet-based experimentation. We show that the V-junction retains the simplicity of operation associated with T-junction formats, whilst offering functionalities normally associated with droplet-on-demand technologies.</P> <P>Graphic Abstract</P><P>We present the use of microfluidic “V-junctions” as a droplet generation strategy that incorporates enhanced performance characteristics when compared to more traditional “T-junction” formats. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4an01730g'> </P>
Optofluidic platforms based on surface-enhanced Raman scattering
Lim, Chaesung,Hong, Jongin,Chung, Bong Geun,deMello, Andrew J.,Choo, Jaebum Royal Society of Chemistry 2010 The Analyst Vol.135 No.5
<P>We report recent progress in the development of surface-enhanced Raman scattering (SERS)-based optofluidic platforms for the fast and sensitive detection of chemical and biological analytes. In the current context, a SERS-based optofluidic platform is defined as an integrated analytical device composed of a microfluidic element and a sensitive Raman spectrometer. Optofluidic devices for SERS detection normally involve nanocolloid-based microfluidic systems or metal nanostructure-embedded microfluidic systems. In the current review, recent advances in both approaches are surveyed and assessed. Additionally, integrated real-time sensing systems that combine portable Raman spectrometers with microfluidic devices are also reviewed. Such real-time sensing systems have significant utility in environmental monitoring, forensic science and homeland defense applications.</P> <P>Graphic Abstract</P><P>We report recent progress in the development of surface-enhanced Raman scattering-based optofluidic platforms for the fast and sensitive detection of chemical and biological analytes. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b919584j'> </P>
Choi, Jae-Won,Jo, Byung-Gwan,deMello, Andrew J.,Choo, Jaebum,Kim, Hak Yong The Royal Society of Chemistry 2016 The Analyst Vol.141 No.24
<P>Fluorescence polarization (FP) is a sensitive, robust, and homogeneous assay format, able to probe a diversity of biological molecules and their interactions. Herein, we describe a new FP strategy based on the use of streptavidin as a signal amplifier. Such signal amplified fluorescence polarization (SAFP) was used to monitor the binding affinity of human angiogenin and a single-stranded DNA aptamer. Streptavidin was bound to a biotinylated single-stranded DNA aptamer and the interaction between this complex and Alexa Fluor 488 labelled human angiogenin was measured. A dissociation constant of 135.3 ± 32.9 nM and a limit of detection of 6.3 nM were successfully extracted only when the FP signal was increased (without binding hindrance) <I>via</I> streptavidin. Moreover, the demonstrated approach was specific to target molecules without any non-specific binding. The streptavidin-triggered SAFP method unlike amplification strategies that utilize nanomaterials (such as graphene oxides, carbon nanotubes, and metal nanoparticles) is not compromised by fluorescence quenching, and it is able to operate within nanomolar concentration regimes. Furthermore, unlike the other FP signal amplification strategies that use dual binding DNA probes, the presented method is simple to implement with signal amplification only requiring the binding of streptavidin with biotinylated DNA. This method could be expanded to analyze molecular interactions and it may be a useful tool for FP measurement by reducing the concentration of rare and expensive protein samples.</P>
Bezinge, Leonard,Maceiczyk, Richard M.,Lignos, Ioannis,Kovalenko, Maksym V.,deMello, Andrew J. American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.22
<P>Recent advances in the development of hybrid organic-inorganic lead halide perovskite (LHP) nanocrystals (NCs) have demonstrated their versatility and potential application in photovoltaics and as light sources through compositional tuning of optical properties. That said, due to their compositional complexity, the targeted synthesis of mixed-cation and/or mixed-halide LHP NCs still represents an immense challenge for traditional batch-scale chemistry. To address this limitation, we herein report the integration of a high-throughput segmented-flow microfluidic reactor and a self-optimizing algorithm for the synthesis of NCs with defined emission properties. The algorithm, named <U>M</U>ultiparametric <U>A</U>utomated <U>R</U>egression Kriging <U>I</U>nterpolation and <U>A</U>daptive Sampling (MARIA), iteratively computes optimal sampling points at each stage of an experimental sequence to reach a target emission peak wavelength based on spectroscopic measurements. We demonstrate the efficacy of the method through the synthesis of multinary LHP NCs, (Cs/FA)Pb(I/Br)<SUB>3</SUB> (FA = formamidinium) and (Rb/Cs/FA)Pb(I/Br)<SUB>3</SUB> NCs, using MARIA to rapidly identify reagent concentrations that yield user-defined photoluminescence peak wavelengths in the green-red spectral region. The procedure returns a robust model around a target output in far fewer measurements than systematic screening of parametric space and additionally enables the prediction of other spectral properties, such as, full-width at half-maximum and intensity, for conditions yielding NCs with similar emission peak wavelength.</P> [FIG OMISSION]</BR>