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Published March 31, 2015 | Published + Supplemental Material
Journal Article Open

Plant nanobionic materials with a giant temperature response mediated by pectin-Ca⁺²


Conventional approaches to create biomaterials rely on reverse engineering of biological structures, on biomimicking, and on bioinspiration. Plant nanobionics is a recent approach to engineer new materials combining plant organelles with synthetic nanoparticles to enhance, for example, photosynthesis. Biological structures often outperform man-made materials. For example, higher plants sense temperature changes with high responsivity. However, these properties do not persist after cell death. Here, we permanently stabilize the temperature response of isolated plant cells adding carbon nanotubes (CNTs). Interconnecting cells, we create materials with an effective temperature coefficient of electrical resistance (TCR) of −1,730% K⁻¹, ∼2 orders of magnitude higher than the best available sensors. This extreme temperature response is due to metal ions contained in the egg-box structure of the pectin backbone, lodged between cellulose microfibrils. The presence of a network of CNTs stabilizes the response of cells at high temperatures without decreasing the activation energy of the material. CNTs also increase the background conductivity, making these materials suitable elements for thermal and distance sensors.

Additional Information

Copyright © 2015 National Academy of Sciences. Edited by Michael S. Strano, Massachusetts Institute of Technology, Cambridge, MA, and accepted by the Editorial Board February 18, 2015 (received for review November 3, 2014). The authors thank Karsten Kunze from the Scientific Center for Optical and Electron Microscopy (ScopeM) of the Eidgenössiche Technische Hochschule Zürich, and R. Thevamaran for support with SEM imaging. This work was supported by Swiss National Science Foundation Grant SNF 157162. Author contributions: R.D.G., C.D., and B.M. designed research; R.D.G. performed research; R.D.G., C.D., and B.M. analyzed data; and R.D.G., C.D., and B.M. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. M.S.S. is a guest editor invited by the Editorial Board. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1421020112/-/DCSupplemental.

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