title: PEGylation does not impair insulin efficacy in three-dimensional cartilage culture: an investigation toward biomimetic polymers.
abstract: A major goal in tissue engineering is the controlled application of growth factors. As a novel application system, we are currently developing biomimetic polymers that are processed into three-dimensional scaffolds. Bioactive proteins will be covalently bound to the polymers via a poly(ethylene glycol) (PEG) linker. Of paramount importance is the maintenance of the biological activity of the protein after PEGylation and covalent binding to the polymer. Therefore, within this study, insulin used as a model protein was PEGylated with an active succinimidyl ester of poly(ethylene glycol) (SS-NH-PEG) (MW ~2000) and biological effects of the protein-PEG conjugate were monitored in comparison with unmodified insulin. No significant differences in chondrocyte proliferation were observed in a conventional proliferation assay after treatment with insulin or PEGylated insulin. In a complex three-dimensional cartilage-engineering model the effects of insulin and PEGylated insulin were investigated over a wide concentration range (0.025-25 microg/mL). Insulin and PEGylated insulin at equivalent concentrations resulted in cartilaginous tissue constructs exhibiting identical wet weight, cell number, biochemical composition of the extracellular matrix, and histological appearance, both compounds significantly improving tissue quality as compared with control constructs. In conclusion, the presented study demonstrates that PEGylation of insulin using SS-NH-PEG did not change the activity of the protein in a complex biological environment and is regarded as a step toward the development of biomimetic polymers.
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Kellner
authors.forename: Jörg
authors.initials: J
authors.lastname: Tessmar
authors.forename: Stefan
authors.initials: S
authors.lastname: Milz
authors.forename: Peter
authors.initials: P
authors.lastname: Angele
authors.forename: Michael
authors.initials: M
authors.lastname: Nerlich
authors.forename: Michaela B
authors.initials: MB
authors.lastname: Schulz
authors.forename: Torsten
authors.initials: T
authors.lastname: Blunk
authors.forename: Achim
authors.initials: A
authors.lastname: Göpferich
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry / Q000378:metabolism*; D002356:Cartilage / Q000378:metabolism*; D002417:Cattle; D018929:Cell Culture Techniques; D019902:Chondrocytes / Q000502:physiology; D006801:Humans; D007328:Insulin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007328:Insulin; D011092:Polyethylene Glycols