Molecular Engineering of Acoustic Protein Nanostructures
Ultrasound is among the most widely used biomedical imaging modalities, but has limited ability to image specific molecular targets due to the lack of suitable nanoscale contrast agents. Gas vesicles—genetically encoded protein nanostructures isolated from buoyant photosynthetic microbes—have recently been identified as nanoscale reporters for ultrasound. Their unique physical properties give gas vesicles significant advantages over conventional microbubble contrast agents, including nanoscale dimensions and inherent physical stability. Furthermore, as a genetically encoded material, gas vesicles present the possibility that the nanoscale mechanical, acoustic, and targeting properties of an imaging agent can be engineered at the level of its constituent proteins. Here, we demonstrate that genetic engineering of gas vesicles results in nanostructures with new mechanical, acoustic, surface, and functional properties to enable harmonic, multiplexed, and multimodal ultrasound imaging as well as cell-specific molecular targeting. These results establish a biomolecular platform for the engineering of acoustic nanomaterials.
© 2016 American Chemical Society. Received: May 21, 2016; Accepted: June 28, 2016. Publication Date (Web): June 28, 2016. The authors thank Jordan Dykes and Nikita Reznik for assistance with experimental apparatus and Assaf Gilad for sharing the LRP gene. The authors also thank Alasdair McDowall for assistance with TEM. This research was supported by the NIH (EB018975) and DARPA (W911NF-14-1-0111). A.L. is supported by the NSF graduate research fellowship (award number 1144469). A.F. is supported by the NSERC graduate fellowship. D.M. is supported by the Human Frontiers Science Program Cross-Disciplinary Postdoctoral Fellowship. Research in the Shapiro laboratory is also supported by the Heritage Medical Research Institute and the Burroughs Wellcome Career Award at the Scientific Interface. Author Contributions: M.G.S. and A.L. conceived the study. A.L., A.F., and S.P.N. designed and planned experiments. A.L., A.F., S.P.N., A.L-G., and D.M. conducted the experiments and analyzed data. R.W.B., A.L., D.M., and M.G.S. wrote the MATLAB scripts for ultrasound imaging and data processing. A.L. and M.G.S. wrote the manuscript with input from all authors. The authors declare no competing financial interest.
Accepted Version - nihms978828.pdf
Supplemental Material - nn6b03364_si_001.pdf