title: Nano-thin walled micro-compartments from transmembrane protein-polymer conjugates.
abstract: The high interfacial activity of protein-polymer conjugates has inspired their use as stabilizers for Pickering emulsions, resulting in many interesting applications such as synthesis of templated micro-compartments and protocells or vehicles for drug and gene delivery. In this study we report, for the first time, the stabilization of Pickering emulsions with conjugates of a genetically modified transmembrane protein, ferric hydroxamate uptake protein component A (FhuA). The lysine residues of FhuA with open pore (FhuA ΔCVFtev) were modified to attach an initiator and consequently controlled radical polymerization (CRP) carried out via the grafting-from technique. The resulting conjugates of FhuA ΔCVFtevwith poly(N-isopropylacrylamide) (PNIPAAm) and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA), the so-called building blocks based on transmembrane proteins (BBTP), have been shown to engender larger structures. The properties such as pH-responsivity, temperature-responsivity and interfacial activity of the BBTP were analyzed using UV-Vis spectrophotometry and pendant drop tensiometry. The BBTP were then utilized for the synthesis of highly stable Pickering emulsions, which could remain non-coalesced for well over a month. A new UV-crosslinkable monomer was synthesized and copolymerized with NIPAAm from the protein. The emulsion droplets, upon crosslinking of polymer chains, yielded micro-compartments. Fluorescence microscopy proved that these compartments are of micrometer scale, while cryo-scanning electron microscopy and scanning force microscopy analysis yielded a thickness in the range of 11.1 ± 0.6 to 38.0 ± 18.2 nm for the stabilizing layer of the conjugates. Such micro-compartments would prove to be beneficial in drug delivery applications, owing to the possibility of using the channel of the transmembrane protein as a gate and the smart polymer chains as trigger switches to tune the behavior of the capsules.
authors.affiliation: Fraunhofer Institute for Applied Polymer Research IAP, Geiselbergstr. 69, 14476 Potsdam-Golm, Germany. alexander.boeker@iap.fraunhofer.de.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Charan
authors.forename: Ulrich
authors.initials: U
authors.lastname: Glebe
authors.forename: Deepak
authors.initials: D
authors.lastname: Anand
authors.forename: Julia
authors.initials: J
authors.lastname: Kinzel
authors.forename: Leilei
authors.initials: L
authors.lastname: Zhu
authors.forename: Marco
authors.initials: M
authors.lastname: Bocola
authors.forename: Tayebeh Mirzaei
authors.initials: TM
authors.lastname: Garakani
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schwaneberg
authors.forename: Alexander
authors.initials: A
authors.lastname: Böker
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008239:Lysine; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D000072417:Protein Domains; D013696:Temperature
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; C050900:FhuA protein, E coli; D011108:Polymers; D008239:Lysine