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Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling
Poster Abstracts
12-POS
Board 12
Fast Insulin Amyloid Aggregation at the Air-Liquid-Solid Triple Interface
Thibaut Frachon
2,1
, Marianne Weidenhaupt
1
, Quentin Le masne
2
, Franz Bruckert
1
.
1
LMGP, Grenoble, France,
2
Eveon, Grenoble, France.
With the growing use of therapeutical proteins and the development of medical delivery devices,
protein stability becomes a major concern in pharmaceutical industrial processes. Proteins can
lose their native conformation by unfolding and reach a new free energy minimum by forming
insoluble aggregates. Insulin is one example of such an aggregation-prone protein, which easily
forms amyloid fibrils on hydrophobic surfaces under agitation. Within a device containing a
protein solution, hydrophobic interfaces are found at the border between hydrophobic materials
and liquid and between air and liquid. These different interfaces come into close proximity in
protocols, frequently used in industry, involving intermittent wetting.
We designed a model experiment, where we observe by optical microscopy the formation of
insulin amyloid fibers as a protein solution moves repetitively back and forth in a microfluidic
channel. Thioflavin T fluorescence was used to monitor the formation of amyloid deposits and
reflection interference contrast microscopy was used to monitor the morphology of the liquid
film after receding. The growth of protein aggregates on the surface was characterized. We
demonstrate that insulin fibers mainly form in regions of intermittent wetting, but not in regions
exposed to hydrodynamic shear stress alone, remaining always wet. This clarifies the role of
interfaces in insulin aggregation, showing that wall shear stress alone is insufficient to rapidly
trigger amyloid fiber formation. We study the influence of temperature, channel size, fluid
velocity, duration of the recession phases and nature of the materials surfaces. Our experiments
illustrate how the formation of a triple solid/liquid/air interface in industrial processes may lead
to protein instability. The careful design of fluid movement in devices handling protein solutions
can therefore improve their stability.