Publications by authors named "D F Weitz"

585 Publications

Attractive Pickering Emulsion Gels.

Adv Mater 2021 Jul 9:e2102362. Epub 2021 Jul 9.

College of Energy Engineering, Zhejiang University, Hangzhou, 310027, P. R. China.

Properties of emulsions highly depend on the interdroplet interactions and, thus, engineering interdroplet interactions at molecular scale are essential to achieve desired emulsion systems. Here, attractive Pickering emulsion gels (APEGs) are designed and prepared by bridging neighboring particle-stabilized droplets via telechelic polymers. In the APEGs, each telechelic molecule with two amino end groups can simultaneously bind to two carboxyl functionalized nanoparticles in two neighboring droplets, forming a bridged network. The APEG systems show typical shear-thinning behaviors and their viscoelastic properties are tunable by temperature, pH, and molecular weight of the telechelic polymers, making them ideal for direct 3D printing. The APEGs can be photopolymerized to prepare APEG-templated porous materials and their microstructures can be tailored to optimize their performances, making the APEG systems promising for a wide range of applications.
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http://dx.doi.org/10.1002/adma.202102362DOI Listing
July 2021

Microchannel measurements of viscosity for both gases and liquids.

Lab Chip 2021 07;21(14):2805-2811

Department of Physics and, John A. Paulson School of Engineering and Applied Sciences, Harvard University, 9 Oxford Street, Cambridge, Massachusetts 02138, USA.

Quantifying the viscosity of a fluid is of great importance in determining its properties and can even be used to identify what the fluid is. While many techniques exist for measuring the viscosity of either gases or liquids, it is very challenging to probe both gases and liquids with a single approach because of the significant difference in their nature, and the vast difference in the values of their viscosities. We introduce a facile approach to measuring the viscosity of a Newtonian fluid, either a gas or a liquid, by flowing it through a deformable microchannel where the deformation depends on the pressure required to induce the flow, which, in turn, depends on the fluid viscosity. A strain gauge embedded just above and across the microchannel transduces the flow-induced deformation into strain. The strain is proportional to the square of the flow-induced deformation enabling us to precisely discriminate not only gases but also liquids based on their viscosities with the same device.
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http://dx.doi.org/10.1039/d1lc00202cDOI Listing
July 2021

Cemental tear: An overlooked finding associated with rapid periodontal destruction. A case series.

Aust Dent J 2021 Apr 17. Epub 2021 Apr 17.

Division of Endodontics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.

Cemental tear is defined as cementum fragment completely or partially detached from the root surface, and it has been associated with localized rapid periodontal breakdown. Although history of trauma and/or attrition may be risk factors, the etiopathology of cemental tear remains unknown. This case series aims to discuss the clinical, radiographic and histopathologic features of cemental tears to aid clinicians in making differential diagnosis. Three teeth from three patients presenting a periradicular lesion underwent an exploratory surgery to determine the cause and provide treatment. Soft and hard tissue biopsies were obtained from each lesion and forwarded for histopathologic evaluation. Two patients received a guided tissue regeneration (GTR) procedure, which allowed the tooth to be retained. One patient received an extraction with simultaneous guided bone regeneration (GBR) due to a hopeless prognosis of the tooth. The results after histopathologic evaluation yielded a final diagnosis of cemental tear for all three patients. Cemental tears may be overlooked, and therefore, they should be included in the differential diagnosis of periapical periodontitis, endodontic-periodontal lesion and vertical root fracture (VRF).
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http://dx.doi.org/10.1111/adj.12844DOI Listing
April 2021

Sequencing-Based Protein Analysis of Single Extracellular Vesicles.

ACS Nano 2021 03 9;15(3):5631-5638. Epub 2021 Mar 9.

Center for Systems Biology, Massachusetts General Hospital, 185 Cambridge Street, CPZN 5206, Boston, Massachusetts 02114, United States.

Circulating extracellular vesicles (EVs)-biological nanomaterials shed from most mammalian cells-have emerged as promising biomarkers, drug delivery vesicles, and treatment modulators. While different types of vesicles are being explored for these applications, it is becoming clear that human EVs are quite heterogeneous even in homogeneous or monoclonal cell populations. Since it is the surface EV protein composition that will largely dictate their biological behavior, high-throughput single EV profiling methods are needed to better define EV subpopulations. Here, we present an antibody-based immunosequencing method that allows multiplexed measurement of protein molecules from individual nanometer-sized EVs. We use droplet microfluidics to compartmentalize and barcode individual EVs. The barcodes/antibody-DNA are then sequenced to determine protein composition. Using this highly sensitive technology, we detected specific proteins at the single EV level. We expect that this technology can be further adapted for multiplexed protein analysis of any nanoparticle.
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http://dx.doi.org/10.1021/acsnano.1c00782DOI Listing
March 2021

Anomalous mechanics of Zn-modified fibrin networks.

Proc Natl Acad Sci U S A 2021 Mar;118(10)

John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138;

Fibrin is the main component of blood clots. The mechanical properties of fibrin are therefore of critical importance in successful hemostasis. One of the divalent cations released by platelets during hemostasis is Zn; however, its effect on the network structure of fibrin gels and on the resultant mechanical properties remains poorly understood. Here, by combining mechanical measurements with three-dimensional confocal microscopy imaging, we show that Zn can tune the fibrin network structure and alter its mechanical properties. In the presence of Zn, fibrin protofibrils form large bundles that cause a coarsening of the fibrin network due to an increase in fiber diameter and reduction of the total fiber length. We further show that the protofibrils in these bundles are loosely coupled to one another, which results in a decrease of the elastic modulus with increasing Zn concentrations. We explore the elastic properties of these networks at both low and high stress: At low stress, the elasticity originates from pulling the thermal slack out of the network, and this is consistent with the thermal bending of the fibers. By contrast, at high stress, the elasticity exhibits a common master curve consistent with the stretching of individual protofibrils. These results show that the mechanics of a fibrin network are closely correlated with its microscopic structure and inform our understanding of the structure and physical mechanisms leading to defective or excessive clot stiffness.
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http://dx.doi.org/10.1073/pnas.2020541118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7958264PMC
March 2021
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