Publications by Year: 2016

2016
Choi, C. - H. ; Lee, H. ; Abbaspourrad, A. ; Kim, J. H. ; Fan, J. ; Caggioni, M. ; Wesner, C. ; Zhu, T. ; Weitz, D. A. Triple Emulsion Drops with An Ultrathin Water Layer: High Encapsulation Efficiency and Enhanced Cargo Retention in Microcapsules. Advanced Materials 2016, 28, 3340–3344. Publisher's VersionAbstract

Triple emulsion drops with an ultrathin water layer are developed to achieve high encapsulation efficiency of hydrophobic cargo in a hydrophobic polymeric shell, directly dispersed in water. Furthermore, enhanced retention of volatile hydrophobic cargo is achieved by forming a hydrogel network within this water layer that serves as a physical barrier.

2016_advmater_choi.pdf
Chen, Q. ; Utech, S. ; Chen, D. ; Prodanovic, R. M. ; Lin, J. - M. ; Weitz, D. A. Controlled Assembly of Heterotypic cells in a Core-Shell Scaffold: Organ in a Droplet. Lab on a Chip 2016, 16, 1346-1349. Publisher's VersionAbstract

This paper reports a droplet-based microfluidic approach to fabricate a large number of monodisperse, portable microtissues, each in an individual drop. We use water–water–oil double emulsions as templates and spatially assemble hepatocytes in the core and fibroblasts in the shell, forming a 3D liver model in a drop.

2016_labchip_chen.pdf
Zhao, X. ; Liu, S. ; Yildirimer, L. ; Zhao, H. ; Ding, R. ; Wang, H. ; Cui, W. ; Weitz, D. Injectable Stem Cell-Laden Photocrosslinkable Microspheres Fabricated Using Microfluidics for Rapid Generation of Osteogenic Tissue Constructs. Advanced Functional Materials 2016, 26. Publisher's VersionAbstract

Direct injection is a minimally invasive method of stem cell transplantation for numerous injuries and diseases. However, despite its promising potential, its clinical translation is difficult due to the low cell retention and engraftment after injection. With high versatility, high‐resolution control and injectability, microfabrication of stem‐cell laden biomedical hydrogels holds great potential as minimally invasive technology. Herein, a strategy of microfluidics‐assisted technology entrapping bone marrow‐derived mesenchymal stem cells (BMSCs) and growth factors in photocrosslinkable gelatin (GelMA) microspheres to ultimately generate injectable osteogenic tissue constructs is presented. Additionally, it is demonstrated that the GelMA microspheres can sustain stem cell viability, support cell spreading inside the microspheres and migration from the interior to the surface as well as enhance cell proliferation. This finding shows that encapsulated cells have the potential to directly and actively participate in the regeneration process. Furthermore, it is found that BMSCs encapsulated in GelMA microspheres show enhanced osteogenesis in vitro and in vivo, associated with a significant increase in mineralization. In short, the proposed strategy can be utilized to facilitate bone regeneration with minimum invasiveness, and can potentially be applied along with other matrices for extended applications.

2016_adfm_zhao.pdf
Cui, N. ; Zhang, H. ; Schneider, N. ; Tao, Y. ; Asahara, H. ; Sun, Z. ; Cai, Y. ; Koehler, S. A. ; de Greef, T. F. A. ; Abbaspourrad, A. ; et al. A mix-and-read drop-based in vitro two-hybrid method for screening high-affinity peptide binders. Scientific reports 2016, 6 22575. Publisher's VersionAbstract

Drop-based microfluidics have recently become a novel tool by providing a stable linkage between phenotype and genotype for high throughput screening. However, use of drop-based microfluidics for screening high-affinity peptide binders has not been demonstrated due to the lack of a sensitive functional assay that can detect single DNA molecules in drops. To address this sensitivity issue, we introduced in vitro two-hybrid system (IVT2H) into microfluidic drops and developed a streamlined mix-and-read drop-IVT2H method to screen a random DNA library. Drop-IVT2H was based on the correlation between the binding affinity of two interacting protein domains and transcriptional activation of a fluorescent reporter. A DNA library encoding potential peptide binders was encapsulated with IVT2H such that single DNA molecules were distributed in individual drops. We validated drop-IVT2H by screening a three-random-residue library derived from a high-affinity MDM2 inhibitor PMI. The current drop-IVT2H platform is ideally suited for affinity screening of small-to-medium-sized libraries (103–106). It can obtain hits within a single day while consuming minimal amounts of reagents. Drop-IVT2H simplifies and accelerates the drop-based microfluidics workflow for screening random DNA libraries, and represents a novel alternative method for protein engineering and in vitro directed protein evolution.

2016_srep_cui.pdf
Ridge, K. M. ; Shumaker, D. ; Robert, A. ; Hookway, C. ; Gelfand, V. I. ; Janmey, P. A. ; Lowery, J. ; Guo, M. ; Weitz, D. A. ; Kuczmarski, E. ; et al. Chapter Fourteen - Methods for Determining the Cellular Functions of Vimentin Intermediate Filaments. In Intermediate Filament Proteins; Omary, M. B. ; Liem, R. K. H., Ed. Academic Press, 2016; Vol. 568, pp. 389 - 426. Publisher's VersionAbstract

The type III intermediate filament protein vimentin was once thought to function mainly as a static structural protein in the cytoskeleton of cells of mesenchymal origin. Now, however, vimentin is known to form a dynamic, flexible network that plays an important role in a number of signaling pathways. Here, we describe various methods that have been developed to investigate the cellular functions of the vimentin protein and intermediate filament network, including chemical disruption, photoactivation and photoconversion, biolayer interferometry, soluble bead binding assay, three-dimensional substrate experiments, collagen gel contraction, optical-tweezer active microrheology, and force spectrum microscopy. Using these techniques, the contributions of vimentin to essential cellular processes can be probed in ever further detail.

2016_methods_in_enzymology_ridge.pdf
Keita, E. ; Koehler, S. A. ; Faure, P. ; Weitz, D. A. ; Coussot, P. Drying kinetics driven by the shape of the air/water interface in a capillary channel. The European Physical Journal E 2016, 39, 23. Publisher's VersionAbstract

We look at the drying process in a simple glass channel with dominant capillary effects as is the case in microfluidics. We find drying kinetics commonly observed for confined geometry, namely a constant period followed by a falling rate period. From visualization of the air/water interface with high resolution, we observe that the drying rate decreases without a drying front progression although this is the usually accepted mechanism for confined geometries. We show with FEM that in our specific geometry the falling rate period is due to changes in the shape of the air-water interface at the free surface where most evaporation occurs. Our simulations show that the sensitivity of the drying rate to the shape of the first air-water interface from the sample free surface implies that slight changes of the wetting or pinning conditions can significantly modify the drying rate.

2016_eurphysje_keita.pdf
Lee, H. ; Choi, C. - H. ; Abbaspourrad, A. ; Wesner, C. ; Caggioni, M. ; Zhu, T. ; Weitz, D. A. Encapsulation and Enhanced Retention of Fragrance in Polymer Microcapsules. ACS Applied Materials & Interfaces 2016, 8 4007-4013. Publisher's VersionAbstract

Fragrances are amphiphilic and highly volatile, all of which makes them a challenging cargo to efficiently encapsulate and retain in microcapsules using traditional approaches. We address these limitations by introducing a new strategy that combines bulk and microfluidic emulsification: a stable fragrance-in-water (F/W) emulsion that is primarily prepared from bulk emulsification is incorporated within a polymer microcapsule via microfluidic emulsification. On the basis of the in-depth study of physicochemical properties of the microcapsules on fragrance leakage, we demonstrate that enhanced retention of fragrance can be achieved by using a polar polymeric shell and forming a hydrogel network within the microcapsule. We further extend the utility of these microcapsules by demonstrating the enhanced retention of encapsulated fragrance in powder state.

2016_acsappliedmaterialsinterface_lee.pdf
Verissimo, C. ; Abbaspourrad, A. ; Sunter, K. ; Capasso, F. ; Moshkalev, S. ; Weitz, D. Hydrothermal Synthesis and Properties of Hierarchical ZnO and Eu-doped ZnO 3D Structures. In une; 2016; Vol. 13, pp. 15. 2016_verissimo.pdf
Spencer, S. J. ; Tamminen, M. V. ; Preheim, S. P. ; Guo, M. T. ; Briggs, A. W. ; Brito, I. L. ; Weitz, D. A. ; Pitkanen, L. K. ; Vigneault, F. ; Virta, M. P. J. ; et al. Massively parallel sequencing of single cells by epicPCR links functional genes with phylogenetic markers. ISME JOURNAL 2016, 10, 427-436. Publisher's VersionAbstract

Many microbial communities are characterized by high genetic diversity. 16S ribosomal RNA sequencing can determine community members, and metagenomics can determine the functional diversity, but resolving the functional role of individual cells in high throughput remains an unsolved challenge. Here, we describe epicPCR (Emulsion, Paired Isolation and Concatenation PCR), a new technique that links functional genes and phylogenetic markers in uncultured single cells, providing a throughput of hundreds of thousands of cells with costs comparable to one genomic library preparation. We demonstrate the utility of our technique in a natural environment by profiling a sulfate-reducing community in a freshwater lake, revealing both known sulfate reducers and discovering new putative sulfate reducers. Our method is adaptable to any conserved genetic trait and translates genetic associations from diverse microbial samples into a sequencing library that answers targeted ecological questions. Potential applications include identifying functional community members, tracing horizontal gene transfer networks and mapping ecological interactions between microbial cells.

2016_isme_spencer.pdf
Wagner, O. ; Thiele, J. ; Weinhart, M. ; Mazutis, L. ; Weitz, D. A. ; Huck, W. T. S. ; Haag, R. Biocompatible fluorinated polyglycerols for droplet microfluidics as an alternative to PEG-based copolymer surfactants. Lab on a Chip 2016, 16, 65–69. Publisher's VersionAbstract

In droplet-based microfluidics, non-ionic, high-molecular weight surfactants are required to stabilize droplet interfaces. One of the most common structures that imparts stability as well as biocompatibility to water-in-oil droplets is a triblock copolymer surfactant composed of perfluoropolyether (PFPE) and polyethylene glycol (PEG) blocks. However, the fast growing applications of microdroplets in biology would benefit from a larger choice of specialized surfactants. PEG as a hydrophilic moiety, however, is a very limited tool in surfactant modification as one can only vary the molecular weight and chain-end functionalization. In contrast, linear polyglycerol offers further side-chain functionalization to create custom-tailored, biocompatible droplet interfaces. Herein, we describe the synthesis and characterization of polyglycerol-based triblock surfactants with tailored side-chain composition, and exemplify their application in cell encapsulation and in vitro gene expression studies in droplet-based microfluidics.

2016_labchip_wagner.pdf
Park, J. - S. ; Kim, D. ; Shin, J. H. ; Weitz, D. A. Efficient nematode swimming in a shear thinning colloidal suspension. Soft Matter 2016, 12, 1892-1897. Publisher's VersionAbstract

The swimming behavior of a nematode Caenorhabditis elegans (C. elegans) is investigated in a non-Newtonian shear thinning colloidal suspension. At the onset value ([curly or open phi] [similar] 8%), the suspension begins to exhibit shear thinning behavior, and the average swimming speed of worms jumps by approximately 12% more than that measured in a Newtonian solution exhibiting no shear dependent viscosity. In the shear thinning regime, we observe a gradual yet significant improvement in swimming efficiency with an increase in [curly or open phi] while the swimming speed remains nearly constant. We postulate that this enhanced swimming can be explained by the temporal change in the stroke form of the nematode that is uniquely observed in a shear thinning colloidal suspension: the nematode features a fast and large stroke in its head to overcome the temporally high drag imposed by the viscous medium, whose effective viscosity ([small eta]s) is shown to drop drastically, inversely proportional to the strength of its stroke. Our results suggest new insights into how nematodes efficiently maneuver through the complex fluid environment in their natural habitat.

2016_soft_matter_park.pdf
Henderson, S. J. ; Xia, J. ; Wu, H. ; Stafford, A. R. ; Leslie, B. A. ; Fredenburgh, J. C. ; Weitz, D. A. ; Weitz, J. I. ; others,. Zinc promotes clot stability by accelerating clot formation and modifying fibrin structure. Thrombosis and haemostasis 2016, 115, 533-542. Publisher's VersionAbstract

Zinc released from activated platelets binds fibrin(ogen) and attenuates fibrinolysis. Although zinc also affects clot formation, the mechanism and consequences are poorly understood. To address these gaps, the effect of zinc on clot formation and structure was examined in the absence or presence of factor (F) XIII. Zinc accelerated a) plasma clotting by 1.4-fold, b) fibrinogen clotting by 3.5- and 2.3-fold in the absence or presence of FXIII, respectively, c) fragment X clotting by 1.3-fold, and d) polymerisation of fibrin monomers generated with thrombin or batroxobin by 2.5– and 1.8-fold, respectively. Whereas absorbance increased up to 3.3-fold when fibrinogen was clotted in the presence of zinc, absorbance of fragment X clots was unaffected by zinc, consistent with reports that zinc binds to the αC-domain of fibrin(ogen). Scanning electron microscopic analysis revealed a twofold increase in fibre diameter in the presence of zinc and in permeability studies, zinc increased clot porosity by 30-fold with or without FXIII. Whereas FXIII increased clot stiffness from 128 ± 19 Pa to 415 ± 27 Pa in rheological analyses, zinc reduced clot stiffness by 10– and 8.5-fold in the absence and presence of FXIII, respectively. Clots formed in the presence of zinc were more stable and resisted rupture with or without FXIII. Therefore, zinc accelerates clotting and reduces fibrin clot stiffness in a FXIII-independent manner, suggesting that zinc may work in concert with FXIII to modulate clot strength and stability.

2016_thrombosis_haemostasis_henderson.pdf

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