title: Microstructural analysis of the fast gelling freeze-dried sodium hyaluronate.
abstract: Although sodium hyaluronate is a very unstable and heat sensitive molecule, it can remain relatively stable during the freeze-drying process. Aqueous sodium hyaluronate (NaHA) gels were prepared and the obtained samples were freeze-dried. The freeze-dried NaHA samples showed fast gelling ability meanwhile preserved their initial viscoelasticity even after reconstitution. The microstructure of gels obtained from raw substance and freeze-dried NaHA samples was characterized with positron annihilation lifetime spectroscopy and X-ray diffraction patterns while their functionality-related macrostructural properties were tested based on their rheological behavior. The presence of phosphate salts improved the formation of ordered supramolecular structure retaining water in the free volume holes of the polymer chains characterized with decreased ortho-positronium lifetime values. This property may be advantageous in the development of a freeze-dried NaHA injection dosage form.
authors.affiliation: Neustadt Apotheke, Kreyssig Str. 19, D-55118 Mainz, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Krüger-Szabó
authors.affiliation: Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Szeged, H-6720, Eötvös u. 6, Szeged, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Aigner
authors.affiliation: Department of Pharmaceutics, Semmelweis University, Hőgyes E. Street 7-9, H-1092 Budapest, Hungary.
authors.forename: Emese
authors.initials: E
authors.lastname: Balogh
authors.affiliation: University Pharmacy Department of Pharmacy Administration, Semmelweis University, Hőgyes E. Street 7-9, H-1092 Budapest, Hungary.
authors.forename: István
authors.initials: I
authors.lastname: Sebe
authors.affiliation: University Pharmacy Department of Pharmacy Administration, Semmelweis University, Hőgyes E. Street 7-9, H-1092 Budapest, Hungary.
authors.forename: Romána
authors.initials: R
authors.lastname: Zelkó
authors.affiliation: Department of Pharmaceutics, Semmelweis University, Hőgyes E. Street 7-9, H-1092 Budapest, Hungary. Electronic address: antal.istvan@pharma.semmelweis-univ.hu.
authors.forename: István
authors.initials: I
authors.lastname: Antal
mesh_terms: D005612:Freeze Drying; D005782:Gels / Q000737:chemistry; D006820:Hyaluronic Acid / Q000737:chemistry*; D015394:Molecular Structure; D012212:Rheology; D014783:Viscosity; D014961:X-Ray Diffraction
chemical_list: D005782:Gels; D006820:Hyaluronic Acid
keywords: Fast gelling; Freeze-drying; Positron annihilation lifetime spectroscopy; Sodium hyaluronate (NaHA); Viscoelasticity