Self-assembly of diblock molecular polymer brushes in the spherical confinement of nanoemulsion droplets

Understanding the self-assembly behavior of polymers of various topologies is key to a reliable design of functional polymer materials. Self-assembly under confinement conditions emerges as a versatile avenue to design polymer particles with complex internal morphologies while simultaneously facilitating scale-up. However, only linear block copolymers have been studied to date, despite the increasing control over macromolecule composition and architecture available. This study extends the investigation of polymer self-assembly in confinement from regular diblock copolymers to diblock molecular polymer brushes (MPBs). Block-type MPBs with polystyrene (PS) and polylactide (PLA) compartments of different sizes are incorporated into surfactant-stabilised oil-in-water (chloroform/water) emulsions. The increasing confinement in the nanoemulsion droplets during solvent evaporation directs the MPBs to form solid nano/microparticles. Microscopy studies reveal an intricate internal particle structure, including interpenetrating networks and axially-stacked lamellae of PS and PLA, depending on the PS/PLA ratio of the brushes.Australian Research Council. Grant Number: DE180100007 endowed professorship. Grant Number: 2016‐2022 German Research Foundation (DFG). Grant Numbers: 2017‐2022, 37692067

Confinement Assembly of ABC Triblock Terpolymers for the High-Yield Synthesis of Janus Nanorings

Block copolymers are versatile building blocks for the self-assembly of functional nanostructures in bulk and solution. While spheres, cylinders, and bilayer sheets are thermodynamically preferred shapes and frequently observed, ring-shaped nanoparticles are more challenging to realize due to energetic penalties that originate from their anisotropic curvature. Today, a handful of concepts exist that produce core-shell nanorings, while more complex (e.g. patchy) nanorings are currently out of reach and have only been predicted theoretically. Here, we demonstrate that confinement assembly of properly designed ABC triblock terpolymers is a general route to synthesize Janus nanorings in high purity. The triblock terpolymer self-assembles in the spherical confinement of nanoemulsion droplets into prolate ellipsoidal microparticles with an axially-stacked lamellar-ring (lr)-morphology. We clarified and visualized this complex, yet well-ordered, morphology with transmission electron tomography (ET). Blocks A and C formed stacks of lamellae with the B microdomain sandwiched in-between as nanorings. Cross-linking of the B-rings allows disassembly of the microparticles into Janus nanorings (JNRs) carrying two strictly separated polymer brushes of A and C on top and bottom. Decreasing the B volume leads to Janus spheres and rods, while an increase of B results in perforated and filled Janus disks. The confinement assembly of ABC triblock terpolymers is a general process that can be extended to other block chemistries and will allow to synthesize a large variety of complex micro- and nanoparticles that inspire studies in self-assembly, interfacial stabilization, colloidal packing, and nanomedicine

Screening and Characterization of RAPD Markers in Viscerotropic <i>Leishmania</i> Parasites

<div><p>Visceral leishmaniasis (VL) is mainly due to the <i>Leishmania donovani</i> complex. VL is endemic in many countries worldwide including East Africa and the Mediterranean region where the epidemiology is complex. Taxonomy of these pathogens is under controversy but there is a correlation between their genetic diversity and geographical origin. With steady increase in genome knowledge, RAPD is still a useful approach to identify and characterize novel DNA markers. Our aim was to identify and characterize polymorphic DNA markers in VL <i>Leishmania</i> parasites in diverse geographic regions using RAPD in order to constitute a pool of PCR targets having the potential to differentiate among the VL parasites. 100 different oligonucleotide decamers having arbitrary DNA sequences were screened for reproducible amplification and a selection of 28 was used to amplify DNA from 12 <i>L. donovani</i>, <i>L. archibaldi</i> and <i>L. infantum</i> strains having diverse origins. A total of 155 bands were amplified of which 60.65% appeared polymorphic. 7 out of 28 primers provided monomorphic patterns. Phenetic analysis allowed clustering the parasites according to their geographical origin. Differentially amplified bands were selected, among them 22 RAPD products were successfully cloned and sequenced. Bioinformatic analysis allowed mapping of the markers and sequences and priming sites analysis. This study was complemented with Southern-blot to confirm assignment of markers to the kDNA. The bioinformatic analysis identified 16 nuclear and 3 minicircle markers. Analysis of these markers highlighted polymorphisms at RAPD priming sites with mainly 5′ end transversions, and presence of inter– and intra– taxonomic complex sequence and microsatellites variations; a bias in transitions over transversions and indels between the different sequences compared is observed, which is however less marked between <i>L. infantum</i> and <i>L. donovani</i>. The study delivers a pool of well-documented polymorphic DNA markers, to develop molecular diagnostics assays to characterize and differentiate VL causing agents.</p></div

Comparative inter-species analysis of mutations within the RAPD priming sites.

<p>Comparative inter-species analysis of mutations within the RAPD priming sites.</p

RAPD profiles obtained with primers OP-O7 (A) and OP-O13 (B) to illustrate examples of monomorphic and polymorphic profiles.

<p>Laboratory codes of the strains are indicated for each lane. SD: Sudan; TN: Tunisia; M: 100 bp DNA size marker. Indicated sizes are in bp.</p

Panel of <i>Leishmania</i> strains used for screening of RAPD markers.

<p>WHO that summarizes Host, geographical origin, year of isolation and laboratory code is presented together with pathology and zymodeme code whenever available. MON– corresponds to zymodeme code attributed by the reference center in Montpellier. The table also gathers study codes assigned to some of the isolates in other studies: D21, D28, D29, D31 and D32: strains used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109773#pone.0109773-Mauricio1" target="_blank">[20]</a>; DON-39 and ARC-43: strains used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109773#pone.0109773-Kuhls1" target="_blank">[21]</a>; Devi, H9, LRC-L57, ADDIS 164: strains used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109773#pone.0109773-Jamjoom1" target="_blank">[18]</a>; Devi, GEBRE1 and KA-Jeddah: strains used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109773#pone.0109773-Thiel1" target="_blank">[53]</a>; DON-81and ARC-43 (LG11): strains used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109773#pone.0109773-Kuhls2" target="_blank">[28]</a>; DON-09, DON-31, DON-39 and ARC-11: strains used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109773#pone.0109773-Chocholov1" target="_blank">[25]</a>. Country abbreviations are shown as specified by WHO recommendations (SD: Sudan; TN: Tunisia; ET: Ethiopia; SA: Saudi Arabia; KE: Kenya; IN: India). ND: Not Determined; CL: cutaneous leishmaniasis; VL: visceral leishmaniasis; PKDL: Post Kala azar Dermal Leishmaniasis.</p><p>Panel of <i>Leishmania</i> strains used for screening of RAPD markers.</p

Selected features characterizing the cloned RAPD markers.

a<p>: Non coding Sequence;</p>b<p>: Overlap with a coding sequence;</p>c<p>: Matching with a coding sequence;</p>d<p>: Minicircle sequence;</p><p>* Imperfect Microsatellite: one mutation in one repeat;</p><p>**Imperfect Microsatellite: one mutation in two repeats;</p><p>*** Imperfect Microsatellite: one mutation in three repeats; (d): a 58 bp deletion associated to the microsatellite; NA: not applicable; −: no microsatellite observed or no mutations at priming site; +: presence of mismatch at priming site.</p><p>Selected features characterizing the cloned RAPD markers.</p