NEWS OF THE WEEK
NANOCAGES FIRE UP CATALYST ACTIVITY MATERIALS: Shells of platinum
just a few atoms thick serve as active, robust catalysts
applies equally well to cooks, carpenters, and catalyst manufacturers. The last group has long tried to figure out ways to maximize the use of precious metals used for making catalysts. A new method for preparing hollow platinum nanocrystals just a few atoms thick may give those efforts a needed boost (Science 2015, DOI: 10.1126/science.aab0801). A standard way to optimize the amount of metal used in a catalyst is to reduce the size of the catalyst particles. The smaller the particle, the greater the fraction of atoms that reside on its surface, where they are accessible to catalyze chemical reactions. Chemists can prepare metal particles just a couple of nanometers in diameter and disperse Atomic layers of platinum them on a support structure. But under (yellow) are deposited on typical high-temperature and highpalladium (green) followed pressure industrial reaction conditions, by selective etching of the such small particles tend to diffuse and palladium nanocrystals to make coalesce, forming larger clumps, or they catalytically active, hollow detach from the support material, any of nanosized cubes and octahedra, as shown in these models. which reduces catalytic activity.
GREEN LIGHT FOR U.S. BIOSIMILAR DRUG BIOLOGICS: Biogen’s Zarxio prevails
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FEDERAL APPEALS COURT has cleared the
path for possible launch in September of the first biosimilar drug in the U.S.—Sandoz’s Zarxio, a version of the biologic filgrastim meant to help ward off infections in cancer patients. Sandoz developed and then obtained FDA approval of Zarxio, but in the process did not provide information relevant to possible patent claims with Amgen, the developer of the filgrastim reference drug marketed under the name Neupogen. Biosimilars are less expensive equivalents of FDA-licensed biologic drugs, which by definition can rarely be exactly duplicated. The take-home message of the federal apWIKIMEDIA COMMONS
Neupogen, a drug that helps cancer patients fight bacterial infections, is marketed by Amgen.
for now in court battle with Amgen, developer of Neupogen
CEN.ACS.ORG
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YOUNAN XIA/GEORGIA TECH
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ASTE NOT, WANT NOT. The familiar adage
Now, Lei Zhang and Younan Xia of Georgia Tech and colleagues have come up with a way to make hollow platinum nanoparticles with ultrathin walls that remain durable during extended catalytic reactions. The hollow nature of these atomically thin particles leaves a large fraction of the atoms accessible for catalysis, maximizing the particles’ activity. The team first deposited just a few atomic layers of platinum on palladium nanocrystals and then selectively etched the palladium in an acid solution. The process yielded crystalline, hollow platinum shells— nanocages—just three or four atomic layers thick. The nanocages’ crystallinity was controlled by the palladium template particles. Cubic palladium cores led to shells with one type of crystal geometry and octahedral cores, a different geometry. The group evaluated the nanocages’ catalytic properties by using them to mediate the oxygen reduction reaction, a classic fuel-cell process that converts oxygen to water. They found that octahedral platinum nanocages were roughly twice as active as cubic ones, and both types of particles were more active than solid, commercial platinum catalysts. They also found the new nanocages to be durable, losing just one-third of their activity after 10,000 catalytic cycles. “This novel approach could promote the next breakthrough, not only in fuel-cell catalysis but also in water splitting and other catalytic systems,” remarks materials chemist Jiye (James) Fang of Binghamton University, SUNY. He adds that the catalytic activity of this unoptimized system may be enhanced by alloying platinum with other metals.—MITCH JACOBY
peals court ruling, says intellectual property attorney Gary H. Levin of the BakerHostetler law firm, is that biosimilar makers are not strictly required to identify and resolve patent issues with the reference drug sponsor before seeking FDA approval of their product. For now, it could mean that biosimilar drug makers can get their drugs to market sooner, he says. Four more biosimilar drugs are known to be awaiting FDA approval. The underlying law, Levin explains, spells out an orderly but complex process in which applicants and sponsors can try to identify and resolve patent issues in advance of biosimilar drug approval and marketing. Under one of the provisions of this so-called patent dance pathway, the parties exchange technical and patent information to develop an “agreed” list of the sponsor’s patents that might be relevant to the applicant’s proposed product. Assuming agreement is reached, the sponsor has 30 days in which to sue for patent infringement. The new ruling, he says, means engaging in this patent dance is purely optional. In last week’s decision, the appeals court also dismissed Sandoz’s counterclaims that it suffered financial harms from delays in its ability to market Zarxio as a result of the Amgen litigation.—WILLIAM SCHULZ
JULY 27, 2015
