A new dielectric dispersion analysis using microwave bio-microsensor for minute droplet of liposome suspension with target biomolecules by S-parameter method

In this work, a microwave bio-microsensor of coplanar waveguide (CPW) interdigital capacitor (IDC) with droplet of about 0.3 μL of liposome suspension with target biomolecules is newly considered and applied for realizing the evaluation of the permittivity of small target droplet by S-parameter method, similar to Dielectric Dispersion Analysis (DDA) by an open-ended probe method. Finally, we have successfully detected by the IDC microsensor the interaction between the liposome and target protein of carbonic anhydrase from bovine (CAB), which is intrinsically the same as that observed by the conventional open-ended probe method. It is significantly important that the IDC method improves the sensitivity, defined as (Δε_r/ε_r)/(solution volume), by about 300 times from the conventional open-ended probe method.