  Traditional detection methods of C-reactive protein (CRP) inflammation
biomarker, in blood are expensive, time-consuming and labor-intensive. Such
existing point-of-care CRP detection devices remain invasive, since they need
blood sampling (finger-pricking or venous puncture). Here, we propose an
electrochemical impedance spectroscopy (EIS)-based sensor for the real-time,
fast, specific, sensitive, and label-free detection of C-reactive protein in
the interstitial fluid (ISF) that can be accessed with minimally invasive
microneedle arrays. The sensor has the potential to be integrated in a wearable
device similar with the continuous glucose monitoring, that will detect CRP in
interstitial fluid in a non-invasive, inexpensive and straightforward manner.
The affinity based assay was tested in both buffer and ISF-like solution. The
limit of detection achieved was 0.7 ug/mL of CRP in buffer, and 0.8 ug/mL of
CRP in ISF-like solution and the sensor shows excellent linearity up to 10
ug/mL. It is worth noting that the proposed sensor operates in low sample
volume (down to 5 uL), and has a response time of 100 seconds.
