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Human insulin adsorption kinetics, conformational changes and amyloidal aggregate formation on hydrophobic surfaces

Paper ID Volume ID Publish Year Pages File Format Full-Text
830 67 2013 10 PDF Available
Title
Human insulin adsorption kinetics, conformational changes and amyloidal aggregate formation on hydrophobic surfaces
Abstract

The formation of insulin amyloidal aggregates on material surfaces is a well-known phenomenon with important pharmaceutical and medical implications. Using surface plasmon resonance imaging, we monitor insulin adsorption on model hydrophobic surfaces in real time. Insulin adsorbs in two phases: first, a very fast phase (less than 1 min), where a protein monolayer forms, followed by a slower one that can last for at least 1 h, where multilayered protein aggregates are present. The dissociation kinetics reveals the presence of two insulin populations that slowly interconvert: a rapidly dissociating pool and a pool of strongly bound insulin aggregates. After 1 h of contact between the protein solution and the surface, the adsorbed insulin has practically stopped dissociating from the surface. The conformation of adsorbed insulin is probed by attenuated total reflection–Fourier transform infrared spectroscopy. Characteristic shifts in the amide A and amide II′ bands are associated with insulin adsorption. The amide I band is also distinct from that of soluble or aggregated insulin, and it slowly evolves in time. A 1708 cm−1 peak is observed, which characterizes insulin adsorbed for times longer than 30 min. Finally, Thioflavin T, a marker of extended β-sheet structures present in amyloid fibers, binds to adsorbed insulin after 30–40 min. Altogether, these results reveal that the conformational change induced in insulin upon binding to hydrophobic surfaces allows further insulin binding from the solution. Adsorbed insulin is thus an intermediate along the α-to-β structural transition that results in the formation of amyloidal fibers on these material surfaces.

Keywords
Protein adsorption on material surfaces; Protein aggregation; Insulin; Surface plasmon resonance imaging (SPRi); Fourier transform infrared spectroscopy (FTIR)
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Human insulin adsorption kinetics, conformational changes and amyloidal aggregate formation on hydrophobic surfaces
Publisher
Database: Elsevier - ScienceDirect
Journal: Acta Biomaterialia - Volume 9, Issue 2, February 2013, Pages 5070–5079
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering