PMAA-CeO2 nanoparticle-based paper microfluidic device with customized image processing software for antioxidant assay

Despite recent advancements in the field of microfluidic paper-based analytical devices (mu PADs), a key challenge remains in developing a simple and efficient mu PAD with customized imaging capabilities for antioxidant assays. In the present study, we report a facile approach for mu PAD fabrication through the application of transparent nail paint leading to creation of hydrophobic barriers and well-defined channels. The resultant mu PADs were then characterized through scanning electron microscopy and contact angle measurements. The resolution and functional features of the fabricated mu PAD were amenable to the intended assay. The mu PAD's impregnated poly(methacrylic acid) (PMAA)-coated cerium oxide (CeO2) nanoparticles oxidized the 3,3 ',5,5 '-tetramethylbenzidine (TMB) leading to the formation of a blue-colored charge-transfer complex. The addition of different antioxidant standard solutions resulted in a reduction in the blue color in a dose-dependent manner which could be observed visually. The color intensity of the PMAA-CeO(2)nanoparticle@TMB oxidation product was inversely proportional to the antioxidant concentration and was measured using customized in-house MATLAB-based image processing software. Importantly, PMAA-CeO(2)nanoparticle-based mu PADs demonstrated good analytical characteristics and were able to be stored for long periods without any loss of activity. Moreover, potential interferents did not pose any threat to the colorimetric signal read-out for determination of antioxidant activity. The developed method was further applied for the assessment of antioxidant activity in a variety of tea samples and performed satisfactorily in comparison with a commonly used antioxidant detection method. Collectively, the developed mu PAD-based platform holds great potential as a low-cost, convenient, portable and reliable method for pursuing various on-site antioxidant assays.