Conspectus
The ability to perform multiplexed detection
of various biomarkers
within complex biological fluids in a robust, rapid, sensitive, and
cost-effective manner could transform clinical diagnostics and enable
personalized healthcare. Electrochemical (EC) sensor technology has
been explored as a way to address this challenge because it does not
require optical instrumentation and it is readily compatible with
both integrated circuit and microfluidic technologies; yet this approach
has had little impact as a viable commercial bioanalytical tool to
date. The most critical limitation hindering their clinical application
is the fact that EC sensors undergo rapid biofouling when exposed
to complex biological samples (e.g., blood, plasma, saliva, urine),
leading to the loss of sensitivity and selectivity. Thus, to break
through this barrier, we must solve this biofouling problem.
In response to this challenge, our group has developed a rapid,
robust, and low-cost nanocomposite-based antifouling coating for multiplexed
EC sensors that enables unprecedented performance in terms of biomarker
signal detection compared to reported literature. The bioinspired
antifouling coating that we developed is a nanoporous composite that
contains various conductive nanomaterials, including gold nanowires
(AuNWs), carbon nanotubes (CNTs), or reduced graphene oxide nanoflakes
(rGOx). Each study has progressively evolved this technology to provide
increasing performance while simplifying process flow, reducing time,
and decreasing cost. For example, after successfully developing a
semipermeable nanocomposite coating containing AuNWs cross-linked
to bovine serum albumin (BSA) using glutaraldehyde, we replaced the
nanomaterials with reduced graphene oxide, reducing the cost by 100-fold
while maintaining similar signal transduction and antifouling properties.
We, subsequently, developed a localized heat-induced coating method
that significantly improved the efficiency of the drop-casting coating
process and occurs within the unprecedented time of <1 min (at
least 3 orders of magnitude faster than state-of-the-art). Moreover,
the resulting coated electrodes can be stored at room temperature
for at least 5 months and still maintain full sensitivity and specificity.
Importantly, this improved coating showed excellent antifouling activity
against various biological fluids, including plasma, serum, whole
blood, urine, and saliva.
To enable affinity-based sensing of
multiple biomarkers simultaneously,
we have developed multiplexed EC sensors coated with the improved
nanocomposite coating and then employed a sandwich enzyme-linked immunosorbent
assay (ELISA) format for signal detection in which the substrate for
the enzyme bound to the secondary antibody precipitates locally at
the molecular binding site above the electrode surface. Using this
improved EC sensor platform, we demonstrated ultrasensitive detection
of a wide range of biomarkers from biological fluids, including clinical
biomarkers, in both single and multiplex formats (N = 4) wi...