title: Protein interactions with layers of TiO2nanotube and nanopore arrays: Morphology and surface charge influence.
abstract: In the present work we investigate the key factors involved in the interaction of small-sized charged proteins with TiO2nanostructures, i.e. albumin (negatively charged), histone (positively charged). We examine anodic nanotubes with specific morphology (simultaneous control over diameter and length, e.g. diameter - 15, 50 or 100nm, length - 250nm up to 10μm) and nanopores. The nanostructures surface area has a direct influence on the amount of bound protein, nonetheless the protein physical properties as electric charge and size (in relation to nanotopography and biomaterial's electric charge) are crucial too. The highest quantity of adsorbed protein is registered for histone, for 100nm diameter nanotubes (10μm length) while higher values are registered for 15nm diameter nanotubes when normalizing protein adsorption to nanostructures' surface unit area (evaluated from dye desorption measurements) - consistent with theoretical considerations. The proteins presence on the nanostructures is evaluated by XPS and ToF-SIMS; additionally, we qualitatively assess their presence along the nanostructures length by ToF-SIMS depth profiles, with decreasing concentration towards the bottom.
  
  
  
  Surface nanostructuring of titanium biomedical devices with TiO2nanotubes was shown to significantly influence the adhesion, proliferation and differentiation of mesenchymal stem cells (and other cells too). A high level of control over the nanoscale topography and over the surface area of such 1D nanostructures enables a direct influence on protein adhesion. Herein, we investigate and show how the nanostructure morphology (nanotube diameter and length) influences the interactions with small-sized charged proteins, using as model proteins bovine serum albumin (negatively charged) and histone (positively charged). We show that the protein charge strongly influences their adhesion to the TiO2nanostructures. Protein adhesion is quantified by ELISA measurements and determination of the nanostructures' total surface area. We use a quantitative surface charge model to describe charge interactions and obtain an increased magnitude of the surface charge density at the top edges of the nanotubes. In addition, we track the proteins presence on and inside the nanostructures. We believe that these aspects are crucial for applications where the incorporation of active molecules such as proteins, drugs, growth factors, etc., into nanotubes is desired.
authors: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia; Department of Materials Science and Engineering, WW4-LKO, University of Erlangen Nuremberg, Erlangen, Germany.
authors: Mukta
authors: M
authors: Kulkarni
authors: Department of Materials Science and Engineering, WW4-LKO, University of Erlangen Nuremberg, Erlangen, Germany.
authors: Anca
authors: A
authors: Mazare
authors: Division of Molecular Pediatrics, Department of Pediatrics, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Jung
authors: J
authors: Park
authors: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
authors: Ekaterina
authors: E
authors: Gongadze
authors: Department of Materials Science and Engineering, WW4-LKO, University of Erlangen Nuremberg, Erlangen, Germany.
authors: Manuela Sonja
authors: MS
authors: Killian
authors: Department for Materials Synthesis, Jožef Stefan Institute, Ljubljana, Slovenia.
authors: Slavko
authors: S
authors: Kralj
authors: Department of Experimental Medicine I, Nikolaus-Fiebiger Center of Molecular Medicine, University of Erlangen-Nuremberg, Erlangen, Germany.
authors: Klaus
authors: K
authors: von der Mark
authors: Laboratory of Biophysics, Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia.
authors: Aleš
authors: A
authors: Iglič
authors: Department of Materials Science and Engineering, WW4-LKO, University of Erlangen Nuremberg, Erlangen, Germany. Electronic address: schmuki@ww.uni-erlangen.de.
authors: Patrik
authors: P
authors: Schmuki
mesh_terms: D000268:Adhesiveness; D000327:Adsorption; D000818:Animals; D002417:Cattle; D004797:Enzyme-Linked Immunosorbent Assay; D006657:Histones / Q000378:metabolism*; D058608:Nanopores; D043942:Nanotubes / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D018629:Spectrometry, Mass, Secondary Ion; D055672:Static Electricity; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D006657:Histones; C009495:titanium dioxide; D012710:Serum Albumin, Bovine; D014025:Titanium
keywords: Albumin; Distribution of protein binding; ELISA; Histone; TiO(2) nanotube/nanopore