title: Self-assembly and photocatalytic activity of branched silicatein/silintaphin filaments decorated with silicatein-synthesized TiO2 nanoparticles.
abstract: The fundamental mechanisms of biomineralization and their translation into innovative synthetic approaches have yielded promising perspectives for the fabrication of biomimetic and bioinspired organic-inorganic hybrid materials. In siliceous sponges, the enzyme silicatein catalyzes the polycondensation of molecular precursors to nano-structured SiO2 that is deposited on self-assembled filaments consisting of the two silicatein isoforms (silicatein-α and -β) and the scaffold protein silintaphin-1. Due to its broad substrate specificity silicatein is also able to convert in vitro various other precursors to non-biogenic materials (e.g., hydrolysis of titanium bis(ammonium lactato)-dihydroxide [TiBALDH] and subsequent polycondensation to titania [TiO2]). In the present approach, silicatein was bioengineered to carry a protein tag (Arg-tag) that confers binding affinity to TiO2. Then, by combining Arg-tagged silicatein-α with silicatein-β and silintaphin-1, self-assembled branched hybrid protein microfilaments were fabricated. Upon subsequent incubation with TiBALDH the filaments were decorated with TiO2 and assayed for photocatalytic activity through photodegradation of the dye methylene blue. This is the first approach that considers concomitant application of two silicatein isoforms for the synthesis of bioinspired organic-inorganic hybrid materials. It is also the first time that the biocatalytic activity of the enzymes has been combined with both the structure-providing properties of silintaphin-1 and a TiO2 affinity protein tag to fabricate self-assembled branched protein filaments as template for a silicatein-synthesized TiO2 photocatalyst. The TiO2-decorated filaments might be explored as a practical alternative to approaches where biotemplates have to be laboriously isolated from their original biological source prior to TiO2 immobilization.
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
authors.forename: Johan
authors.initials: J
authors.lastname: Gardères
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.|Biomaterials Department, National Research Centre, Cairo, Egypt.
authors.forename: Tarek A
authors.initials: TA
authors.lastname: Elkhooly
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
authors.forename: Thorben
authors.initials: T
authors.lastname: Link
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
authors.forename: Julia S
authors.initials: JS
authors.lastname: Markl
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Renkel
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Korzhev
authors.affiliation: Institute for Physiological Chemistry, University Medical Center, Johannes Gutenberg-University, Duesbergweg 6, 55128, Mainz, Germany. wiens@uni-mainz.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wiens
mesh_terms: D000345:Affinity Labels; D002384:Catalysis; D002403:Cathepsins / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D053768:Metal Nanoparticles / Q000737:chemistry*; D055668:Photochemical Processes; D014025:Titanium / Q000737:chemistry*
chemical_list: D000345:Affinity Labels; C112571:silicatein alpha; C009495:titanium dioxide; D014025:Titanium; D002403:Cathepsins
keywords: Hybrid protein biotemplate; Photocatalysis; Self-assembled protein filaments; Silicatein; TiO2 protein affinity tag