A new publication for Steve, Melissa and Jamy- congrats on a job well done!

C3PE: counter-current continuous phase extraction for improved precision of in-droplet chemical reactions

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Abstract

To improve tools for controlling and optimizing miniaturized chemistry, a novel oil extraction architecture, designated as the Counter-Current Continuous Phase Extraction (C3PE) module, was developed to enable precise control over reaction incubation in water-in-oil droplet microfluidic reactors. Using a symmetric pillar array coupled to adjustable oil flows prevented sample loss and droplet breakup, even at high final volume fractions, and cross-flow added novel stabilization of oil extraction against instability in control pressures. By integrating this dynamic functionality, C3PE enabled rational selection of the oil extraction magnitude across a range of achievable final droplet volume fractions (up to 85%) when processing droplets at 40–200 Hz. Further, this versatile device handled many droplet sizes (70–500 pL demonstrated here). Next, this approach to controlling droplet volume fraction enabled incubation time monitoring and optimization when coupled to a K-channel direct injection feature to label selected droplets. In profiling system characteristics like volume fraction, channel geometry, and continuous phase viscosity, this technique provided a powerful tool to control, measure, and improve incubation performance. Finally, applying C3PE principles to an in-droplet β-galactosidase enzyme reaction (useful in immunoassay systems) increased product formation while significantly decreasing variance in product yield among droplets relative to a non-extracted comparison. We envision that this method will inform future design and implementation of high precision in-droplet chemistry while being of general interest in the study of emulsion fluid dynamics.


Read the full paper here!



Congratulations to Nina and Cole on the New Publication!

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Impact of Silanization Parameters and Antibody Immobilization Strategy on Binding Capacity of Photonic Ring Resonators

Abstract

Ring resonator-based biosensors have found widespread application as the transducing principle in “lab-on-a-chip” platforms due to their sensitivity, small size and support for multiplexed sensing. Their sensitivity is, however, not inherently selective towards biomarkers, and surface functionalization of the sensors is key in transforming the sensitivity to be specific for a particular biomarker. There is currently no consensus on process parameters for optimized functionalization of these sensors. Moreover, the procedures are typically optimized on flat silicon oxide substrates as test systems prior to applying the procedure to the actual sensor. Here we present what is, to our knowledge, the first comparison of optimization of silanization on flat silicon oxide substrates to results of protein capture on sensors where all parameters of two conjugation protocols are tested on both platforms. The conjugation protocols differed in the chosen silanization solvents and protein immobilization strategy. The data show that selection of acetic acid as the solvent in the silanization step generally yields a higher protein binding capacity for C-reactive protein (CRP) onto anti-CRP functionalized ring resonator sensors than using ethanol as the solvent. Furthermore, using the BS3 linker resulted in more consistent protein binding capacity across the silanization parameters tested. Overall, the data indicate that selection of parameters in the silanization and immobilization protocols harbor potential for improved biosensor binding capacity and should therefore be included as an essential part of the biosensor development process.

You can read the article here!

New Feature Article from Yi and Steve in Analytical Chemistry!

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Translational Opportunities for Microfluidic Technologies to Enable Precision Epigenomics

Abstract

Personalizing health care by taking genetic, environmental, and lifestyle factors into account is central to modern medicine. The crucial and pervasive roles epigenetic factors play in shaping gene−environment interactions are now well recognized. However, identifying robust epigenetic biomarkers and translating them to clinical tests has been difficult due in part to limitations of available platforms to detect epigenetic features genome-wide (epigenomic assays). This Feature introduces several important prospects for precision epigenomics, highlights capabilities and limitations of current laboratory technologies, and emphasizes opportunities for microfluidic tools to facilitate translation of epigenetic analyses to the clinic, with a particular focus on methods to profile gene-associated histone modifications and their impacts on chromatin structure and gene expression.

You can read the featured article here!

Congrats to Emily on the New Publication in Analyst!

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A linear mass concentration detector for solvent gradient polymer separations

Abstract

Characterization of copolymers requires the measurement of two distributions—molecular weight (MW) and chemical composition (CC). Molecular weight distributions (MWD) are traditionally determined using size exclusion chromatography (SEC) run under isocratic solvent conditions. Chemical composition distributions (CCD) are often determined using liquid adsorption chromatography (LC) with solvent gradients. The use of solvent gradients, however, often limits options of compatible detectors. A gradient compatible, universal linear mass concentration detector is a longstanding unmet need. Many industrially-relevant polymers lack chromophores or other discriminating moieties requiring detectors with a universal response. Differential refractive index (dRI) is incompatible with gradient elution due to its small dynamic range. Charged aerosol detectors (CAD) and evaporative light scattering detectors (ELSD) are probably the most promising options for gradient elution detection, but both suffer from a nonlinear mass concentration response. Silicon photonic microring resonators are optical sensors that are responsive to changes in the local refractive index (RI). The substantial dynamic range of this technology makes it attractive for refractive index-based detection during solvent gradient elution. Previously, the microring resonator platform was used as a SEC detector to characterize the MWD of broadly dispersed polystyrene (PS) standards. In this study, we demonstrate the gradient compatibility of the microring resonator platform for polymer detection by quantifying the CCD of polymer blend components. Control experiments were run with UV and ELSD detection, highlighting the uniqueness of the platform as a linear mass concentration detector with a universal detector response.

You can read the full publication here!

separationsNOW Highlights Lab's Work with Capillary Electrophoresis

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Here’s a snippet from the article:

All the main detection techniques commonly used with capillary electrophoresis (CE) can only detect analytes with specific properties. Fluorescence detectors can only detect analytes that fluoresce, UV detectors can only detect analytes that absorb UV light and amperometric detectors can only detect analytes that can be oxidized or reduced at an electrode. Even mass spectrometry, which is generally considered a universal detection technique, can only detect analytes separated by CE that can be efficiently converted into ions by electrospray ionization.

The one detection technique that can work with CE and is truly universal is refractive index (RI) detection, in which analytes are detected by changes they cause in the extent to which light is bent, or refracted, as it passes through the CE buffer. The problem is that RI detection isn’t particularly sensitive, especially at the small scales of CE.

You can read the full article here!

New Publication from John in Analytical Chemistry

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Silicon Photonic Microring Resonator Arrays as a Universal Detector for Capillary Electrophoresis

Abstract

Electrophoretic separations conventionally rely on chromogenic, fluorogenic, or redox properties for analyte detection that, in many instances, involve chemical modification of samples prior to analysis. For analytes natively lacking chemical signatures, refractive index-based measurements are appealing as a method to detect these molecules without pre-treatment. Microring resonators are a type of whispering gallery mode sensor capable of detecting bulk changes in refractive index. Here, we demonstrate the use of silicon photonic microring resonator arrays as a post-column detector for capillary electrophoresis. In this approach, we establish the universal detection capabilities of microrings through calibration with analytes lacking unique spectral signatures. Separations of small molecule mixtures are demonstrated using capillary zone electrophoresis. For these separations, the microring resonators maintain a linear response over several orders of magnitude in concentration for three candidate small molecules. Successful separation of three sugars with direct detection is also demonstrated. We further present the successful separation and detection of three model proteins, exemplifying the promise of microring resonators arrays as a biocompatible detector for capillary electrophoresis. Additionally, the spatially offset, array-based nature of the sensing platform enables real-time analysis of analyte mobility and performance characterization—a combination that is not typically provided using single-point detectors.

You can find the full publication here!

New Review from Mari and Heather in Current Opinion in Environmental Science & Health

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Recent advances in environmental and clinical analysis using microring resonator–based sensors

ABSTRACT

Progress in the development of biosensors has dramatically improved analytical techniques. Biosensors have advantages over more conventional analytical techniques arising from attributes such as straightforward analyses, higher throughput, miniaturization, smaller sample input, and lower cost. Microring optical resonators have emerged in the area of optical sensors as an exceptional choice because of their sensitivity, ease of fabrication, multiplexity capability, and label-free detection. In this article, the sensing principle of these sensors is described. In addition, we summarize and highlight their most recent and relevant applications in environmental and clinical detection analysis.


Click here to read the manuscript!