title: Lyophilization of protein-loaded polyelectrolyte microcapsules.
abstract: OBJECTIVE
  To evaluate if lyophilization can be used to obtain a dry formulation of polyelectrolyte microcapsules, which have emerged as a new class of microparticles for the encapsulation and delivery of biomacromolecules.
  
  
  METHODS
  Microcapsules composed of dextran sulfate and poly-L-arginine were obtained by coating CaCO(3) microparticles by means of the layer-by-layer technique. Microcapsules were lyophilized using different stabilizers; intactness was checked by CLSM and SEM. Horseradish peroxidase was encapsulated as model enzyme and retained activity after freeze-drying was determined using a fluorescence assay. Ovalbumin was encapsulated as model antigen; immunogenicity after lyophilization was evaluated in vitro by a T-cell proliferation assay and in vivo by measuring the antibody titer in mice.
  
  
  RESULTS
  The results clearly demonstrate the necessity of using polyols in the formulation to prevent rupture of the microcapsules and to preserve the activity of encapsulated enzymes. Lyophilized microcapsules appeared as a promising adjuvant for antigen delivery, as both in vitro as in vivo assays showed higher immune activation compared to free antigen.
  
  
  CONCLUSIONS
  Lyophilization is a promising strategy towards improved stability of protein-loaded microcapsules.
authors.affiliation: Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, Belgium.
authors.forename: Marie-Luce
authors.initials: ML
authors.lastname: De Temmerman
authors.forename: Joanna
authors.initials: J
authors.lastname: Rejman
authors.forename: Johan
authors.initials: J
authors.lastname: Grooten
authors.forename: Thomas
authors.initials: T
authors.lastname: De Beer
authors.forename: Chris
authors.initials: C
authors.lastname: Vervaet
authors.forename: Jo
authors.initials: J
authors.lastname: Demeester
authors.forename: Stefaan C
authors.initials: SC
authors.lastname: De Smedt
mesh_terms: D000818:Animals; D002214:Capsules / Q000737:chemistry*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005612:Freeze Drying; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D008954:Models, Biological; D010047:Ovalbumin / Q000737:chemistry*; D011073:Polyamines / Q000737:chemistry*; D000071228:Polyelectrolytes
chemical_list: D002214:Capsules; D010047:Ovalbumin; D011073:Polyamines; D000071228:Polyelectrolytes