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Abstract Protein immobilization studies with high protein binding sensitivity are of primary concern for any bio-sensing applications. In the present study, glutaraldehyde (GA) was utilized to chemically cross-link with the cellulose compound in mixed cellulose (MC) membrane and the protein molecules. Optimal cross-linking process on membrane was determined statistically and corresponded responses of protein immobilization were described through a quadratic empirical model. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) micrographs and thermogravimetric analysis (TGA) have demonstrated the successful deposition of GA on membranes. The optimum GA integration process condition was found at 3 wt% of GA on a single layer and 30 min of integration time, with protein binding predicted at 896.6 μg/cm3. The experimental validation was conducted at this optimum condition, and the result was found at 911.9 μg/cm3, with standard deviation of 1.6%. This small error confirms the adequacy of the empirical model and its ability to predict the GA-protein immobilization performances.

This study explored the preparation of conductive polyaniline-iron oxide (PANI-Fe2O3) that served as the electrical signal transducer, to convert the electrochemical interactions between the biotinylated-goat-anti-mouse IgG (b-IgG) and bovine serum albumin (BSA) into a measurable resistance signal. In this study, PANI was synthesized through the oxidative polymerization of aniline monomer (AM) in the presence of ammonium persulfate (APS) as the oxidizing agent. Concentration effects of AM and volume ratios of AM:APS were evaluated so as to obtain higher conductivity performance in an electrochemical sensing application. The synthesized PANI composites were analyzed through conductivity measurement. The conductive PANI-Fe2O3-GA-b-IgG bio-conjugates was then interacted with BSA, relays the antigen-antibody binding as a measured electrical detection in an assembled pulse-mode electrochemical biosensor. In present work, 0.2 m of AM with 1:3 volume ratio of AM:APS has contributed to the optimal ionic conductivity property of PANI, with excellent electrochemical sensing performance recorded at 3.538±0.067 mΩ.

The present study elucidates the morphology characteristic of nylon‐6 as protein immobilization film and their influences in biological recognition interface for a single‐use electrochemical immunosensor. A basic requirement of this polymer platform is to allow the testing analyte [conductive polyaniline‐Fe2O3‐glutaraldehyde‐conjugated‐N‐hydroxysuccinimidobiotin (PANI‐Fe2O3‐GA‐b‐NHS)] to access to the immobilized capture reagent [bovine serum albumin (BSA)] on a surface of the nylon‐6 film. As an immunoassay, the biochemical reaction between PANI‐Fe2O3‐GA‐b‐NHS and BSA takes place on a surface of the nylon‐6 support film, which then translated into measurable resistance signal through pulse‐mode measurement. The in‐house developed nylon‐6 film, N‐16B, with 16 wt % nylon polymer and methanol as nonsolvent had demonstrated the fastest lateral wicking speed (1.07 mm s−1) and excellent protein immobilization capacity (1650 ± 85.84 μg cm−3), leading to the higher electrical current signal with a minimal resistance of electrochemical responses (0.57 ± 0.04 MΩ). This work reflects the importance of the physical characteristics of the nylon‐6 film that determines the sensitivity and effectiveness of an immunosensor. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46741.

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