The
interactions of proteins and other molecules and their adsorption
onto substrates is a fascinating topic that has been applied to surface
technologies, biosensors, corrosion studies, biotechnologies, and
other fields. The success of these applications requires a previous
characterization using some analytical techniques that, ordinarily,
are not electrochemical. This work proposes analyzing the variation
of the double-layer capacitance obtained through impedance electrochemical
spectroscopy as an alternative strategy to show evidence of the interactions
between proteins and triblock copolymers. The proposal is supported
through the study of the interaction and adsorption of bovine serum
albumin (BSA) and a commercial triblock copolymer (P103) in phosphate
buffer on a gold electrode. The double-layer capacitance and the apparent
interface thickness vs polarization potential curves as well as the
potential of zero charge for pure P103 (0.6 wt %, corresponding to
6 g L
–1
), pure BSA (3 mg mL
–1
),
and P103-BSA solutions (0.6 wt % and 3 mg mL
–1
,
respectively) are sensitive enough to show not only the interaction
and the adsorption of the species but also the polarization potential
where these interactions are taking place. A qualitative and quantitative
analysis concerning the double-layer capacitance behavior is given.
The significance and impact of this work is also presented.