title: Adsorption of insulin with varying self-association profiles to a solid Teflon surface--influence on protein structure, fibrillation tendency and thermal stability.
abstract: Interfaces are present in the preparation of pharmaceutical products and are well known for having an influence on the physical stability of proteins. The aim of this study was to examine the conformation (i.e. secondary and tertiary structures) and fibrillation tendency, overall aggregation tendency and thermal stability of adsorbed human insulin at a solid particulate Teflon surface. The effects of changes in the association degree of insulin on the structure and stability have been determined. Using SEC-HPLC, association profiles were determined for insulin aspart, zinc-free human insulin and human insulin with two Zn(2+) per hexamer in concentrations ranging from 0.1 mg/ml to 20 mg/ml. Insulin aspart was 100% monomeric, regardless of concentration. In contrast, human insulin went from 100% monomer to 80% hexamer, and 20% dimer/monomer and zinc-free human insulin from 100% monomer to 70% dimer and 30% monomer with increasing concentration. The secondary structure of the insulins changed upon adsorption, but only minor differences were observed among the insulins. Structural changes were observed when the insulin-surface ratio was varied, but at no point did the structure resemble that of fibrillated insulin in solution. The presence of particles resulted in increased fibrillation of human insulin. The lag-time of fibrillation decreased, when the amount of particles present was increased. In conclusion, the type and association degree of the three insulin variants has no major influence on the secondary structure observed after adsorption of insulin at the solid Teflon surface. However, the presence of particles increases the tendency of insulin to fibrillate.
authors.affiliation: Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen O, Denmark. lej@farma.ku.dk
authors.forename: Lene
authors.initials: L
authors.lastname: Jorgensen
authors.forename: Pernille
authors.initials: P
authors.lastname: Bennedsen
authors.forename: Søren Vrønning
authors.initials: SV
authors.lastname: Hoffmann
authors.forename: Rasmus Linnemann
authors.initials: RL
authors.lastname: Krogh
authors.forename: Charlotte
authors.initials: C
authors.lastname: Pinholt
authors.forename: Minna
authors.initials: M
authors.lastname: Groenning
authors.forename: Susanne
authors.initials: S
authors.lastname: Hostrup
authors.forename: Jens T
authors.initials: JT
authors.lastname: Bukrinsky
mesh_terms: D000327:Adsorption; D004355:Drug Stability; D057927:Hydrophobic and Hydrophilic Interactions; D007004:Hypoglycemic Agents / Q000737:chemistry*; D007328:Insulin / Q000737:chemistry*; D011138:Polytetrafluoroethylene / Q000737:chemistry*; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013499:Surface Properties; D013696:Temperature
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D011138:Polytetrafluoroethylene