MATERIALS
▸ Making fillable, injectable polymer microparticles Three-dimensional printing is a powerful technique for rapid prototyping, but when put into practical use, the approach may not be compatible with materials used for biomedical applications such as drug delivery. Robert S. Langer, Ana Jaklenec, and coworkers at Massachusetts Institute of Technology have developed an alternative method for making microdevices from biomedically relevant materials, such
C R E D I T: S CI E NC E ( P O LYM ER ) ; F IL I P E N ATA LI O ( F LU OR ES C E N C E)
An indivdiual fabricated microparticle before it’s been filled and sealed (top) and an array of sealed microparticles. as poly(lactic-co-glycolic acid) (Science 2017, DOI: 10.1126/science. aaf7447). The researchers use polydimethylsiloxane molds to shape individual layers of multilayer polymeric devices. They then align, assemble, and bond the layers using heat. The MIT team used the method to make fillable polymer microparticles that release their contents according to a preprogrammed schedule on the basis of polymer composition. They built particle bases, filled them with drug solution, capped the bases with polymer lids, sealed them by heating, and then scraped the microparticles off the substrate. In a test application, the researchers made single-injection vaccines by placing antigen doses in microparticles that release the contents at desired intervals. They gave mice a single injection of a mixture of microparticles that released ovalbumin, a model antigen, nine and 41 days after injection. Those mice achieved antibody levels higher than those in mice given separate ovalbumin injections at days six and 36. In addition to drug delivery applications, the MIT researchers used the fabrication method to make a pH sensor and microfluidic devices.—CELIA ARNAUD
INORGANIC CHEMISTRY
Old palladium cluster yields intricate surprise In 1964, a team of Russian chemists reported an Originally proposed 1964 experiment in which they treated a palladium salt Ph Ph Cl with triphenylcyclopropenium chloride and ethCl Ph – ylene. They proposed a product structure consistPd – Pd Pd ing of a Pd3Cl4 chain capped by two cyclopropenyl Cl Cl Ph Ph ligands. When Christian Jandl, Karl Öfele, and Alexander Pöthig of Technical University of Munich recently noticed that some reactions of cyclopropenium ions with transition metals result in ring opening and formaH H tion of four-membered metallacycles, they became inH2PdCl4 C C H H terested in the actual structure of the 1964 molecule and + wanted to know more about cyclopropenium’s reactivity. Ph Ph The Munich team repeated the originally reported synthesis + Cl– and found out with the benefit of today’s analytical tools that the actual molecule is a more complex Pd6Cl8 cluster capped by Ph triphenylpropyl ligands (Organometallics 2017, DOI: 10.1021/acs. organomet.7b00525). The researchers believe the ring-opened ligand forms in a two-step process involving the partial reduction of Pd(II) to Pd(0) by ethylene followed by Newly identified oxidative addition of cyclopropenium to palladium. 2– Ph Ph They devised an alternative synthesis of the cluster using Pd(II) and Pd(0) salts with triphenylcyclopropenium Ph Cl Pd chloride to confirm the ring-opening event. Pöthig and Cl Cl Pd coworkers say this molecule represents the first isolated Pd Cl Cl Pd organometallic palladium cluster compound, although Cl Pd Cl that was not recognized in 1964, and one of the first Pd Cl Ph transition-metal clusters in general—the concept Ph of metal clusters wasn’t fully defined until 1966 by Ph Ph = phenyl MIT’s F. Albert Cotton.—STEVE RITTER
BIOBASED MATERIALS
▸ New route to glowing and magnetic fabrics Researchers have created a new approach for producing “smart” textiles by treating the ovules of cotton plants with glucose conjugates of fluorescent and magnetic compounds. Cotton fibers that grow from the ovules incorporate the compounds and could conceivably be used to make glowing or magnetic cotton fabrics. Filipe Natalio of Martin Luther University Halle-Wittenberg and the Weizmann Institute of
Cotton fibers containing fluorescent groups glow under UV light.
Science and coworkers developed the approach (Science, DOI: 10.1126/science. aan5830). The researchers point out that the incorporated functional compounds should be less likely to wear off fabrics than hydrophobic, conductive, or other types of fabric coatings applied by external chemical treatments. They synthesized a fluorescent glucose conjugate using a fluorescein compound and a magnetic glucose conjugate using a dysprosium complex and added the conjugates to cotton ovules in lab cultures. The conjugates enter cotton cells and weave together with other glucose molecules into cellulosic chains that make up cotton. No genetic engineering is involved. The fluorescent cotton fibers are weaker than normal ones, but the magnetic fibers are not weakened. Natalio and coworkers believe their biological fabrication approach can be extended to make functional, high-value products from other biological systems as well, such as bacteria, bamboo, silk, and flax.—STU BORMAN SEPTEMBER 18, 2017 | CEN.ACS.ORG | C&EN
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