title: Strategies for maintaining the particle size of peptide DNA condensates following freeze-drying.
abstract: The particle size of peptide DNA condensates were studied after freeze-drying and rehydration as a function of sugar excipient, concentration, pH, DNA concentration, and peptide condensing agent. In the absence of an excipient, freeze-dried 50 microg/ml AlkCWK(18) (iodoacetic acid alkylated Cys-Typ-Lys(18)) DNA condensates formed large fibrous flocculates on rehydration. Of the sugars tested as lyoprotectants, sucrose proved most effective at preserving particle size during rehydration. The addition of 5 wt/vol% sucrose preserved a mean particle diameter of less than 50 nm during rehydration of AlkCWK(18) DNA condensates prepared at DNA concentrations up to 200 microg/ml; however, higher DNA concentrations led to the formation of insoluble fibrous flocculates. Substitution of polyethylene glycol (PEG)-CWK(18) as a DNA condensing peptide eliminated the need for sucrose, resulting in peptide DNA condensates that retained particle size when rehydrated in water or normal saline at concentrations up to 5 mg/ml. The results suggest that sucrose functions primarily as a bulking agent during freeze-drying that only preserves the particle size of AlkCWK(18) DNA condensates up to a maximum concentration of 200 microg/ml. Alternatively, the steric layer created on the surface of PEG-CWK(18) DNA condensates provides far more efficient lyoprotection, preserving their particle size at a concentration of 5 mg/ml without a bulking agent.
authors.affiliation: Divisions of Pharmaceutics, College of Pharmacy, University of Michigan, Ann Arbor, MI 48109-1065, USA. krice@umich.edu
authors.forename: K Y
authors.initials: KY
authors.lastname: Kwok
authors.forename: R C
authors.initials: RC
authors.lastname: Adami
authors.forename: K C
authors.initials: KC
authors.lastname: Hester
authors.forename: Y
authors.initials: Y
authors.lastname: Park
authors.forename: S
authors.initials: S
authors.lastname: Thomas
authors.forename: K G
authors.initials: KG
authors.lastname: Rice
mesh_terms: D004247:DNA / Q000008:administration & dosage* / Q000737:chemistry; D016503:Drug Delivery Systems; D005612:Freeze Drying; D006863:Hydrogen-Ion Concentration; D010316:Particle Size; D010455:Peptides / Q000008:administration & dosage* / Q000737:chemistry; D013395:Sucrose / Q000494:pharmacology
chemical_list: D010455:Peptides; D013395:Sucrose; D004247:DNA