Wright-Patterson Air Force Base 3 articles published in JoVE Biology Preparation of Multifunctional Silk-Based Microcapsules Loaded with DNA Plasmids Encoding RNA Aptamers and Riboswitches Irina Drachuk1,2, Svetlana Harbaugh2, Nancy Kelley-Loughnane3, Jorge L. Chávez2 1UES Inc., 2711th Human Performance Wing, Airman Systems Directorate, Air Force Research Laboratory, Wright-Patterson AFB, 3Materials and Manufacturing Directorate, Wright-Patterson AFB The protocol describes the formation of robust and biocompatible DNA-laden microcapsules as multiplexed in vitro biosensors capable of tracking several ligands. Biology Design and Development of Aptamer–Gold Nanoparticle Based Colorimetric Assays for In-the-field Applications Joshua E. Smith1, Jorge L. Chávez2,3, Joshua A. Hagen2, Nancy Kelley-Loughnane2 1Department of Science and Mathematics, Alvernia University, 2711th Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, 3UES, Inc. The design and development of an aptamer–gold nanoparticle colorimetric assay for the detection of small molecules for in-the-field applications was examined. Additionally, a smart-device colorimetric application (app) was validated and long-term storage of the assay was established for use in the field. Biology A Method for Selecting Structure-switching Aptamers Applied to a Colorimetric Gold Nanoparticle Assay Jennifer A. Martin1,2, Joshua E. Smith1,2, Mercedes Warren1, Jorge L. Chávez1,3, Joshua A. Hagen1, Nancy Kelley-Loughnane1 1711th Human Performance Wing, Human Effectiveness Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, 2The Henry M. Jackson Foundation, 3UES, Inc. A protocol is provided to select structure-switching aptamers for small molecule targets based on a tunable stringency magnetic bead selection method. Aptamers selected with structure-switching properties are beneficial for assays that require a conformational change to signal the presence of a target, such as the described gold nanoparticle assay.