Development of a paper-based microfluidic analytical device by a more facile hydrophobic substrate generation strategy

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 (μPADs), a key challenge remains in developing a simple and efficient μPAD with customized imaging capabilities for antioxidant assays. In the present study, we report a facile approach for μPAD fabrication through the application of transparent nail paint leading to creation of hydrophobic barriers and well-defined channels. The resultant μPADs were then characterized through scanning electron microscopy and contact angle measurements. The resolution and functional features of the fabricated μPAD were amenable to the intended assay. The μPAD'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-CeO₂ 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-CeO₂ nanoparticle-based μPADs 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 μPAD-based platform holds great potential as a low-cost, convenient, portable and reliable method for pursuing various on-site antioxidant assays. Graphical Abstract.

Fabrication of paper-based microfluidic device by recycling foamed plastic and the application for multiplexed measurement of biomarkers

Microfluidic paper-based analytical devices (μPADs) are emerging as effective analytical platforms for point-of-care assays in resource-limited areas. Simple and cost-effective fabrication method still remains challenging on μPADs. A simple and cost-effective method for fabricating paper-based devices was presented in this work by using of dipping strategy with the recycled polystyrene in chloroform as the hydrophobic reagent. Adhesive tape was employed as mask to transfer the hydrophilic channel pattern to the paper substrate. With the single-sided adhesive tape stuck on the hydrophilic parts of the paper surface, the paper-based device was immersed in chloroform solution with dissolving recycling polystyrene for several seconds. Then the hydrophilic pattern can be achieved and all the other parts on the paper surface were hydrophobic. The adhesive tape was torn off from the hydrophilic parts. The highest contact angle value of 114° of the hydrophobic part was acquired with this simple fabrication method. By using of the sandwich-type immunoreactions and luminol-H₂O₂p-iodophenol (PIP) chemiluminescence(CL) system, three cancer biomarkers were simultaneously detected in human serum samples on μPADs with the linear range of 0.05-80.0 ng·mL^-1 for carcinoembryonic antigen (CEA), 5.0-80.0 ng·mL^-1 for alpha-fetal protein (AFP) and 1.0-50.0 ng·mL^-1 for prostate-specific antigen (PSA). The fabricating strategy with recycling polystyrene and adhesive tape provides a versatile platform for prototyping of μPADs in both developed and resource constrained region.