title: Determination of the Porosity of PLGA Microparticles by Tracking Their Sedimentation Velocity Using a Flow Imaging Microscope (FlowCAM).
abstract: To investigate whether particle sedimentation velocity tracking using a flow imaging microscope (FlowCAM) can be used to determine microparticle porosity.
  
  
  
  Two different methods were explored. In the first method the sedimentation rate of microparticles was tracked in suspending media with different densities. The porosity was calculated from the average apparent density of the particles derived by inter- or extrapolation to the density of a suspending medium in which the sedimentation velocity was zero. In the second method, the microparticle size and sedimentation velocity in one suspending fluid were used to calculate the density and porosity of individual particles by using the Stokes' law of sedimentation.
  
  
  
  Polystyrene beads of different sizes were used for the development, optimization and validation of the methods. For both methods we found porosity values that were in excellent agreement with the expected values. Both methods were applied to determine the porosity of three PLGA microparticle batches with different porosities (between about 4 and 52%). With both methods we obtained microparticle porosity values similar to those obtained by mercury intrusion porosimetry.
  
  
  
  We developed two methods to determine average microparticle density and porosity by sedimentation velocity tracking, using only a few milligrams of powder.
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, Leiden, The Netherlands.
authors.forename: A S
authors.initials: AS
authors.lastname: Sediq
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, Leiden, The Netherlands.
authors.forename: S K D
authors.initials: SKD
authors.lastname: Waasdorp
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, Leiden, The Netherlands.
authors.forename: M R
authors.initials: MR
authors.lastname: Nejadnik
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, Leiden, The Netherlands.|Dr. Reddy's Laboratories Ltd., IPDO, Leiden, The Netherlands.
authors.forename: M M C
authors.initials: MMC
authors.lastname: van Beers
authors.affiliation: Dr. Reddy's Laboratories Ltd., IPDO, Leiden, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Meulenaar
authors.affiliation: Dr. Reddy's Laboratories Ltd., IPDO, Leiden, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Verrijk
authors.affiliation: Division of Drug Delivery Technology, Cluster BioTherapeutics, Leiden Academic Centre for Drug Research (LACDR), Leiden University, Leiden, The Netherlands. w.jiskoot@lacdr.leidenuniv.nl.
authors.forename: W
authors.initials: W
authors.lastname: Jiskoot
mesh_terms: D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry*; D008853:Microscopy / Q000379:methods; D008863:Microspheres; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D016062:Porosity; D011208:Powders / Q000737:chemistry
chemical_list: D011208:Powders; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid
keywords: FlowCAM; PLGA microparticles; flow imaging microscope; particle analysis; porosity