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Sensing Ability and Formation Criterion of Fluid Supported Lipid Bilayer Coated Graphene Field-Effect Transistors
journal contribution
posted on 2019-02-28, 00:00 authored by Shu-Kai Hu, Fang-Yen Lo, Chih-Chen Hsieh, Ling ChaoSupported
lipid bilayers (SLBs) have been widely used to provide
native environments for membrane protein studies. In this study, we
utilized graphene field-effect transistors (GFETs) coated with a fluid
SLB to perform label-free detection of membrane-associated ligand–receptor
interactions in their native lipid bilayer environment. It is known
that the analyte-binding event needs to occur within the Debye length
for it to be significantly sensed by an FET sensor. However, the thickness
of a lipid bilayer is around 4–5-nm-thick, which is larger
than the Debye length of a solution with physiologically relevant
ionic strength. There is thus a question of whether an FET sensor
can detect the binding event above the bilayer. In this study, we
show how the existence of an SLB can influence the effective detection
distance and the formation criterion of a fluid and continuous SLB
on a graphene surface. We discovered that the water intercalation
between the graphene and the underlying silica substrate hinders the
SLB formation but is required for the stable electrical recording
by a GFET. To verify the existence of a fluid SLB on graphene, which
was previously complicated by the graphene fluorescence quenching
effect, we developed a modified fluorescence recovery after photobleaching
method. In addition, our results showed that SLB coated GFETs can
quantitatively detect ligand binding onto the receptors embedded in
the SLBs. The comparison of our experimental data with a theoretical
model shows that the contribution of the SLB acyl chain hydrophobic
region to the screening effect can be negligible and, therefore, that
the effective detection region can extend beyond the SLB.