title: Stochastic transport through carbon nanotubes in lipid bilayers and live cell membranes.
abstract: There is much interest in developing synthetic analogues of biological membrane channels with high efficiency and exquisite selectivity for transporting ions and molecules. Bottom-up and top-down methods can produce nanopores of a size comparable to that of endogenous protein channels, but replicating their affinity and transport properties remains challenging. In principle, carbon nanotubes (CNTs) should be an ideal membrane channel platform: they exhibit excellent transport properties and their narrow hydrophobic inner pores mimic structural motifs typical of biological channels. Moreover, simulations predict that CNTs with a length comparable to the thickness of a lipid bilayer membrane can self-insert into the membrane. Functionalized CNTs have indeed been found to penetrate lipid membranes and cell walls, and short tubes have been forced into membranes to create sensors, yet membrane transport applications of short CNTs remain underexplored. Here we show that short CNTs spontaneously insert into lipid bilayers and live cell membranes to form channels that exhibit a unitary conductance of 70-100 picosiemens under physiological conditions. Despite their structural simplicity, these 'CNT porins' transport water, protons, small ions and DNA, stochastically switch between metastable conductance substates, and display characteristic macromolecule-induced ionic current blockades. We also show that local channel and membrane charges can control the conductance and ion selectivity of the CNT porins, thereby establishing these nanopores as a promising biomimetic platform for developing cell interfaces, studying transport in biological channels, and creating stochastic sensors.
authors.affiliation: 1] Biology and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA [2] School of Natural Sciences, University of California, Merced, California 95340, USA [3] The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Jia
authors.initials: J
authors.lastname: Geng
authors.affiliation: 1] Biology and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA [2] The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [3] Mechanical Engineering Department, University of California, Berkeley, California 94720, USA.
authors.forename: Kyunghoon
authors.initials: K
authors.lastname: Kim
authors.affiliation: School of Natural Sciences, University of California, Merced, California 95340, USA.
authors.forename: Jianfei
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, 48940 Leioa, Spain.
authors.forename: Artur
authors.initials: A
authors.lastname: Escalada
authors.affiliation: 1] Biology and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA [2] The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Ramya
authors.initials: R
authors.lastname: Tunuguntla
authors.affiliation: Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Luis R
authors.initials: LR
authors.lastname: Comolli
authors.affiliation: 1] Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA [2] Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [3] National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Frances I
authors.initials: FI
authors.lastname: Allen
authors.affiliation: Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, 48940 Leioa, Spain.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Shnyrova
authors.affiliation: Biology and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Kang Rae
authors.initials: KR
authors.lastname: Cho
authors.affiliation: Biology and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Dayannara
authors.initials: D
authors.lastname: Munoz
authors.affiliation: Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Y Morris
authors.initials: YM
authors.lastname: Wang
authors.affiliation: Mechanical Engineering Department, University of California, Berkeley, California 94720, USA.
authors.forename: Costas P
authors.initials: CP
authors.lastname: Grigoropoulos
authors.affiliation: 1] The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [3] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Ajo-Franklin
authors.affiliation: 1] Biophysics Unit (CSIC, UPV/EHU) and Department of Biochemistry and Molecular Biology, University of the Basque Country, 48940 Leioa, Spain [2] Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain.
authors.forename: Vadim A
authors.initials: VA
authors.lastname: Frolov
authors.affiliation: 1] Biology and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, USA [2] School of Natural Sciences, University of California, Merced, California 95340, USA [3] The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Noy
mesh_terms: D000818:Animals; D001692:Biological Transport; D016466:CHO Cells; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism*; D002470:Cell Survival; D003412:Cricetulus; D004247:DNA / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism*; D008081:Liposomes; D037742:Nanotubes, Carbon / Q000648:ultrastructure; D018272:Porins / Q000737:chemistry / Q000378:metabolism*; D013269:Stochastic Processes
chemical_list: D007473:Ion Channels; D008051:Lipid Bilayers; D008081:Liposomes; D037742:Nanotubes, Carbon; D018272:Porins; D004247:DNA