ELECTRONIC MATERIALS
C R E D I T: N ED HOYL E /JO H N O’ N E I LL ( MI C RO G RA PH ) ; OH IO STAT E UN I V E RS I T Y (BAN DAG E )
▸ Bandage zaps biofilm infections More than half of human infections are caused by bacteria that glom on to one another or to a surface to form a protective biofilm that can be difficult to treat with antibiotics. Researchers led by Chandan K. Sen at Ohio State University Wexner Medical Center have developed a textile-based This bandage’s electric bandage weak electric that fights infecfield disrupts tions physically inbiofilm formation stead of chemically, in wounds to help defeat infections. thwarting the bacteria’s ability to develop resistance. They now report the first test of the bandage’s effectiveness for treating biofilm infections in pigs (Ann. Surg. 2017, DOI: 10.1097/sla.0000000000002504). The dressing is patterned with silver and zinc polka dots that create a weak electric field when they come into contact with body fluids at the wound site, which disrupts the electrical signals that bacteria send to one another to form biofilms. In the test, the researchers studied pigs with burn wounds infected with human bacterial strains. They bandaged the wounds either within two hours of the injury or a week after the injury. Using scanning electron microscopy, the team found that the “electroceutical” dressing was able to prevent or disrupt biofilm formation and speed up wound healing compared with a placebo bandage.—TIEN
BIOLOGICAL CHEMISTRY
Circadian rhythm helps time wound healing Within each of our cells, an intrinsic biochemical “clock” orchestrates gene and protein expression over an approximately 24-hour cycle. To better understand how this circadian rhythm influences cell function, researchers led by John S. O’Neill of the MRC Laboratory of Molecular Biology turned to a type of connective tissue cell that has a well-studied cellular clock. These cells, called fibroblasts, migrate to wounds and promote healing. The scientists found that many of the rhythmically expressed proteins in fibroblasts regulated polymerization of actin, a structural protein important for migration. In experiments with cell cultures, tissue samples, and mice, fibroblasts migrated more quickly to a wound received during the active phase of the circadian cycle than to a wound received in the dormant phase (Sci. Transl. Med. 2017, DOI: 10.1126/ Fibroblasts grown in culture migrate scitranslmed.aal2774). The remore efficiently over 60 hours into searchers analyzed data from burn a scratch sustained during an active clinics around the U.K. and found part of the cells’ circadian cycle (left) a similar phenomenon in humans, than into a scratch sustained during a with burns sustained during daydormant phase (right). light hours healing about 60% faster than burns sustained at night. With further study, these findings could influence clinical decisions on treatment, the researchers note, or provide an avenue to use a drug to pharmacologically reset cellular clocks to aid in wound healing. “Theoretically this will allow us to trick the cells into ‘thinking’ it’s daytime during the night,” says lead author Nathaniel P. Hoyle. “It’s just a case of selecting the right compound.”—EMMA HIOLSKI
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NGUYEN
CATALYSIS
▸ Powerful pairing spurs Lewis acids into action Noncovalent catalysts that feature dual hydrogen bonds have been used in a variety of enantioselective reactions by directly activating substrate molecules. But they typically require highly reactive electrophilic substrates to work well. Harvard University chemists Eric N. Jacobsen, Steven M. Banik, Anna Levina, and Alan M. Hyde wondered if they could overcome this obstacle by
OSi(CH3)3 OCH3 + OCH3
O O
Chiral squaramide, triethylsilyl triflate
using a dual-hydrogen-bonding catalyst indirectly. They pair squaramides capable of forming two hydrogen bonds with triflate anions to create an enhanced Lewis acid (Science 2017, DOI: 10.1126/science.aao5894). This combination leads to the formation of oxocarbenium ion intermediates from acetals at low temperatures. The chemists use the noncovalent catalyst in enantioselective Mukaiyama aldol reactions as well as [4 + 3] cycloadditions (example shown). “The use of hydrogen-bond donors should no longer be restricted to conventional catalytic
O
O
N H
N H
CF3
O – O S O CF3 OSi(CH3)3 OCH3 + Oxyallyl cation intermediate
CF3 CH3O
O O
[4+3] Cycloadduct
methods reliant on the direct activation of substrates,” writes Anita E. Mattson, an expert on noncovalent catalysis at Worcester Polytechnic Institute, in a commentary that accompanies the paper. “Instead, the future of hydrogen-bond-donor catalysis should include exploitation of hydrogen bonding and anion recognition in the production of new catalytic species to enable reactivity patterns that are otherwise inaccessible.”—BETHANY HALFORD NOVEMBER 13, 2017 | CEN.ACS.ORG | C&EN
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