title: Significance of particle size and charge capacity in TiO2 nanoparticle-lipid interactions.
abstract: OBJECTIVE
  The activity of submicron sized titanium oxide (TiO2) particles towards biomembrane models is coupled to their charge carrying capacity and their primary particle size.
  
  
  METHODS
  Electrochemical methods using a phospholipid layer on mercury (Hg) membrane model have been used to determine the phospholipid monolayer activity of TiO2 as an indicator of biomembrane activity. The particles were characterised for size, by dynamic light scattering (DLS) and scanning electron microscopy (SEM), and for charge, by acid-base titration.
  
  
  RESULTS
  TiO2 nanoparticles aggregate in 0.1moldm(-3) solutions of KCl. The charge capacity of TiO2 nanoparticles depends on their primary particle size and is unaffected by aggregation. TiO2 particles of ∼40nm primary particle size interact significantly with phospholipid layers. Aggregation of these particles initially has a small effect on this interaction but long term aggregation influences the interaction whereby the aggregates penetrate the lipid layer rather than adsorbing on the surface. Fulvic acid does not inhibit the ∼40nm particle/phospholipid interaction. P25 TiO2 particles of larger particle size interact less strongly with phospholipid layers and the interaction is alleviated following particle aggregation. The semiconductor properties of TiO2 are evident in voltammograms showing electron transfer to TiO2 adsorbed on uncoated Hg.
authors.affiliation: School of Chemistry, University of Leeds, Leeds LS2 9JT, UK. Electronic address: A.V.Vakourov@leeds.ac.uk.
authors.forename: Alex
authors.initials: A
authors.lastname: Vakurov
authors.affiliation: School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK. Electronic address: R.M.Drummond-Brydson@leeds.ac.uk.
authors.forename: Rik
authors.initials: R
authors.lastname: Drummond-Brydson
authors.affiliation: School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK. Electronic address: fy12uko@leeds.ac.uk.
authors.forename: Oji
authors.initials: O
authors.lastname: Ugwumsinachi
authors.affiliation: School of Chemistry, University of Leeds, Leeds LS2 9JT, UK. Electronic address: a.l.nelson@leeds.ac.uk.
authors.forename: Andrew
authors.initials: A
authors.lastname: Nelson
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry / Q000378:metabolism; D055664:Electrochemical Techniques; D008567:Membranes, Artificial; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D010316:Particle Size; D010743:Phospholipids / Q000378:metabolism*; D055672:Static Electricity; D013473:Sunscreening Agents / Q000737:chemistry / Q000378:metabolism*; D014025:Titanium / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001672:Biocompatible Materials; D008567:Membranes, Artificial; D010743:Phospholipids; D013473:Sunscreening Agents; C009495:titanium dioxide; D014025:Titanium
keywords: Particle aggregation; Particle size; Phospholipid monolayers; Rapid cyclic voltammetry; Semiconductor properties; Titanium dioxide nanoparticles