title: A single-step aerosol process for in-situ surface modification of nanoparticles: Preparation of stable aqueous nanoparticle suspensions.
abstract: OBJECTIVE
  Surface modification of nanoparticles during aerosol or gas-phase synthesis, followed by direct transfer into liquid media can be used to produce stable water-dispersed nanoparticle suspensions.
  
  
  METHODS
  This work investigates a single-step, aerosol process for in-situ surface-modification of nanoparticles. Previous studies have used a two-step sublimation-condensation mechanism following droplet drying, for surface modification, while the present process uses a liquid precursor containing two solutes, a matrix lipid and a surface modifying agent. A precursor solution in chloroform, of stearic acid lipid, with 4 %w/w of surface-active, physiological molecules [1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol)-sodium salt (DPPG) or 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol) 2000]-ammonium salt (DPPE-PEG)] was processed in an aerosol reactor at a low gas temperatures. The surface modified nanoparticles were characterized for morphology, surface composition and suspension properties.
  
  
  RESULTS
  Spherical, surface-modified lipid nanoparticles with median mobility diameters in the range of 105-150nm and unimodal size distributions were obtained. Fourier transform infra-red spectroscopy (FTIR) measurements confirmed the presence of surface-active molecules on external surfaces of modified lipid nanoparticles. Surface modified nanoparticles exhibited improved suspension stability, compared to that of pure lipid nanoparticles for a period of 30days. Lowest aggregation was observed in DPPE-PEG modified nanoparticles from combined electrostatic and steric effects. The study provides a single-step aerosol method for in-situ surface modification of nanoparticles, using minimal amounts of surface active agents, to make stable, aqueous nanoparticle suspensions.
authors.affiliation: Centre of Research in Nanotechnology and Science, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India.
authors.forename: Mahak
authors.initials: M
authors.lastname: Sapra
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India; Casali Center of Applied Chemistry, Institute of Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
authors.forename: Amol Ashok
authors.initials: AA
authors.lastname: Pawar
authors.affiliation: Centre of Research in Nanotechnology and Science, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India; Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India. Electronic address: chandra@iitb.ac.in.
authors.forename: Chandra
authors.initials: C
authors.lastname: Venkataraman
mesh_terms: D000336:Aerosols; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013535:Suspensions; D014867:Water / Q000737:chemistry
chemical_list: D000336:Aerosols; D013535:Suspensions; D014867:Water
keywords: Aerosol synthesis; Drug delivery; Submicron droplet drying; Surface modification of nanoparticles; Suspension stability; Water dispersible nanoparticles