Detection of vasodilator drugs through microwave spectroscopy of Au NP colorimetric probes using a microwave metallic photonic crystal-inspired resonant probe

Abstract

Here, we report a low-cost, time-effective, easy-to-use, and novel analytical technique incorporating microwave spectroscopy of unmodified gold nanoparticles for the successful detection of two vasodilator drugs – amlodipine besylate and minoxidil. The sensor probe consists of a microwave metallic photonic crystal, which is loaded into the ground plane of a ∼λ/4 cylindrical line source. The sensing scheme is based on inducing aggregation in the gold nanoparticles upon addition of the analyte drug, and then performing microwave spectroscopy for different concentrations of the two drugs. The proposed method was validated in the concentration ranges of 100–0.05 μM and 20–0.625 mM for amlodipine besylate and minoxidil drugs, respectively, and a good linearity was obtained for the calibrated data. The scope of the reported user-friendly technique can be further enhanced by improvement of the limit of detection of specific drugs by favourable functionalization and/or surface modification of suitable nanoparticle probes.