Using 3D printed magnetic platform as support for screen printed electrode applied for p-toluenediamine detection in biological fluid and water samples.

The present work reports the development and application of a new electrochemical sensor for the determination of low concentration levels of p-toluenediamine (PTD) in biological fluids and surface water samples. The proposed sensor was developed using a 3D-printed magnetic device as platform for carbon screen printed electrode (CSPE) modified by magnetic nanoparticles functionalized with carboxylic groups and l-cysteine (MNP-CA-CYS). The results obtained from the morphological and electrochemical characterizations of the sensing platform enabled us to confirm the success of the sensor functionalization with l-cysteine and to have a better understanding of the electrochemical behavior and preconcentration of PTD on the electrode surface. PTD oxidation occurred at 0.24V on MNP-CA-CYS and the mechanism recorded an increase of 51.0% in anodic peak current. Under optimized conditions, the square wave voltammograms obtained for the electrode modified by 40.0 µL MNP-CA-CYS suspension at 1.0 mg mL-1, with accumulation time of 3 min, presented an analytical curve with linear range of 8.00 × 10-7 to 8.00 × 10-5 mol L-1, represented by the equation Iap = (0.383 ± 0.011)[PTD] - (8.112 ± 0.07) × 10-8 (R2 = 0.9994), and detection and quantification limits of 8.53 × 10-8 and 2.56 × 10-7 mol L-1, respectively. Finally, the proposed method was validated through comparison with high performance liquid chromatography coupled to diode array detector (HPLC-DAD) technique and was successfully applied for PTD determination in samples of surface water, tap water, fetal bovine serum and artificial urine.

Assessment of WO3 electrode modified with intact chloroplasts as a novel biohybrid platform for photocurrent improvement.

The present work describes an easy way to prepare a Chloroplast/PDA@WO3 biohybrid platform based on the deposition of chloroplasts on WO3 substrate previously modified with polydopamine (PDA) film as anchoring agent. The use of PDA as an immobilization matrix for chloroplasts, and also as an electron mediator under LED irradiation, resulted in enhanced photocurrents. The use of the chloroplasts amplified the photocurrent, when compared to the bare substrate (WO3). The best electrode performance was obtained using high intensity LED irradiation at 395 nm, for the electrode exposed for 10 min to 150 µg mL-1 of intact chloroplasts. Amperometric curves obtained by on/off cycles using an applied potential of +0.50 V, in PBS electrolyte (pH 7.0), showed that the presence of 0.2 × 10-3 mol L-1 of simazine caused an approximately 50% decrease of the photobiocurrent. Preliminary studies indicated that the synthesized platform based on intact chloroplasts is a good strategy for studying the behavior of photosynthetic entities, using an LED light-responsive WO3 semiconductor substrate. This work contributes to the understanding of photobiocatalysts that emerge as a new class of materials with sophisticated and intricate structures. These are promising materials with remarkably improved quantum efficiency with potential applications in photobioelectrocatalysis.