title: Gamma-irradiation of lyophilised wound healing wafers.
abstract: Lyophilised wafers are being developed as drug delivery systems that can be applied directly to the surface of suppurating wounds. They are produced by the freeze-drying of polymer solutions and gels. This study investigates the possibility of sterilising these glassy, solid dosage forms with gamma-irradiation and determining the rheological properties of rehydrated wafers post-irradiation. One series of wafers was formulated using sodium alginate (SA) modified with increasing amounts of methylcellulose (MC), the other being composed of xanthan gum (XG) and MC. Batches were divided into three lots, two of which were exposed to 25 and 40 kGrays (kGy) of Cobalt-60 gamma-irradiation, respectively, the third being retained as a non-irradiated control. Apparent viscosities of solutions/gels resulting from the volumetric addition of distilled water to individual wafers were determined using continuous shear, flow-rheometry. Flow behaviour on proprietary suppurating surfaces was also determined. Large reductions in viscosity were apparent for irradiated SA samples while those of XG appeared to be largely unaffected. In addition, an increase in the yield stress of xanthan formulations was observed. Xanthan wafers appeared to withstand large doses of irradiation with no detrimental effect on the rheology of reconstituted gels. This offers the possibility of manufacturing sterilisable delivery systems for wounds.
authors.affiliation: Department of Pharmaceutical Sciences, University of Strathclyde, Strathclyde Institute for Biomedical Sciences, 27 Taylor Street, Glasgow G4 ONR, UK. k.h.matthews@rgu.ac.uk
authors.forename: K H
authors.initials: KH
authors.lastname: Matthews
authors.forename: H N E
authors.initials: HN
authors.lastname: Stevens
authors.forename: A D
authors.initials: AD
authors.lastname: Auffret
authors.forename: M J
authors.initials: MJ
authors.lastname: Humphrey
authors.forename: G M
authors.initials: GM
authors.lastname: Eccleston
mesh_terms: D000464:Alginates / Q000737:chemistry / Q000528:radiation effects; D002626:Chemistry, Pharmaceutical; D005612:Freeze Drying; D005720:Gamma Rays; D005782:Gels; D020723:Glucuronic Acid / Q000737:chemistry / Q000528:radiation effects; D006603:Hexuronic Acids / Q000737:chemistry / Q000528:radiation effects; D008747:Methylcellulose / Q000737:chemistry / Q000528:radiation effects; D009779:Occlusive Dressings; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects*; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000528:radiation effects; D012212:Rheology; D013242:Sterilization; D013678:Technology, Pharmaceutical / Q000379:methods; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D000464:Alginates; D005782:Gels; D006603:Hexuronic Acids; D011108:Polymers; D011135:Polysaccharides, Bacterial; D014867:Water; D020723:Glucuronic Acid; D008747:Methylcellulose; C002563:xanthan gum