Inside Front Cover: Designed for local application to exposed tissues, a synthetic lysine‐leucine biopolymer, K100L40, provides a combination of direct microbicidal activity and barrier properties. These amino acid block copolymers are active against Gram‐positive and Gram‐negative bacteria, as well as yeast. Driven by association of water insoluble leucine segments, they form viscous solutions and hydrogels that are effective barriers against microbial contamination of tissues. These materials represent a new approach to the prevention of life‐threatening infections that can complicate surgery and trauma. This is reported by Michael P. Bevilacqua, Daniel J. Huang, Brian D. Wall, Shalyn J. Lane, Carl K. Edwards, III, Jarrod A. Hanson, Diego Benitez, Joseph S. Solomkin, and Timothy J. Deming, article number 1600492.