A novel tyrosinase-based biosensor was developed for the detection of dopamine (DA). For increased selectivity, gold electrodes were previously modified with cobalt (II)-porphyrin (CoP) film with electrocatalytic activity, to act both as an electrochemical mediator and an enzyme support, upon which the enzyme tyrosinase (Tyr) was cross-linked. Differential pulse voltammetry was used for electrochemical detection and the reduction current of dopamine-quinone was measured as a function of dopamine concentration. Our experiments demonstrated that the presence of CoP improves the selectivity of the electrode towards dopamine in the presence of ascorbic acid (AA), with a linear trend of concentration dependence in the range of 2–30 µM. By optimizing the conditioning parameters, a separation of 130 mV between the peak potentials for ascorbic acid AA and DA was obtained, allowing the selective detection of DA. The biosensor had a sensitivity of 1.22 ± 0.02 µA·cm⁻²·µM⁻¹ and a detection limit of 0.43 µM. Biosensor performances were tested in the presence of dopamine medication, with satisfactory results in terms of recovery (96%), and relative standard deviation values below 5%. These results confirmed the applicability of the biosensors in real samples such as human urine and blood serum.

Bovine serum albumin (BSA) acts as a carrier for many endogenous and exogenous compounds, such as thyroid hormones or corresponding drugs. Binding of the hydrophilic levothyroxine drug (LT4) to BSA is of significant pharmacological importance. In this work, UV-vis measurements were used to determine the pH value at which LT4 interacts optimally with proteins. The binding mechanism and affinity of the interaction between LT4 and BSA were investigated using Fourier-transform infrared spectroscopy (FT-IR), fluorescence, fluorescence resonance energy transfer (FRET), Surface Plasmon Resonance (SPR), supplemented by molecular docking analysis. Fluorescence measurements revealed the quenching effect of LT4 on the BSA intrinsic fluorescence and LT4 binding with BSA is driven by a ground-state complex formation that may be accompanied by a nonradiative energy transfer process. The thermodynamic parameters correspond to an enthalpic process, driven mainly by hydrogen bonds and van der Waals forces. Using SPR, the adsorbed amount of biomolecules was calculated and the binding affinity of LT4 with confined-BSA was characterized, indicating that the BSA immobilization plays an important role in LT4 binding. Docking studies confirmed the formation of the LT4-BSA complex with LT4 bound to site I on the BSA structure mainly with amino acid residues Trp 213, Tyr 137, Tyr 147. The calculation of the apparent association constant confirms the result obtained in SPR. Communicated by Ramaswamy H. Sarma

Herein we review the recent advances in biosensors for antioxidants detection underlying principles particularly emphasizing advantages along with limitations regarding the ability to discriminate between the specific antioxidant or total content. Recent advances in both direct detection of antioxidants, but also on indirect detection, measuring the induced damage on DNA-based biosensors are critically analysed. Additionally, latest developments on (bio)electronic tongues are also presented.

One of the most important aspects of the detection of antioxidant compounds is developing a fast screening method. The screening of the overall relative antioxidant capacity (RAC) of several Romanian hydrosoluble plant extracts is the focus of this work. This is important because of the presence of increasing levels of reactive oxygen species (such as H₂O₂) generates oxidative stress in the human body. The consequences are a large number of medical conditions that can be helped by a larger consumption of plant extracts as food supplements, which do not necessarily contain the specified antioxidant contents. By exploiting the catalytic properties of gold nanoparticles, a specific and sensitive nanoparticle-based label-free electrochemical sensor was developed, where the working parameters were optimized for RAC screening of hydrosoluble plant extracts. First, electrochemical measurements (cyclic voltammetry and amperometry) were used to characterize different nanoparticle-based sensors, revealing the best performance of gold nanoparticle-based sensors, obtaining a RAC of 98% for lavender extracts. The sensing principle is based on the quenching effect of antioxidants for H₂O₂ amperometric detection, where the decrease in electrical signal suggests an increasing antioxidant capacity. The obtained results were expressed in terms of ascorbic acid and Trolox equivalents in order to be able to correlate our results with classical methods like chemiluminescence and UV-Vis spectrophotometry, where a correlation coefficient of 0.907 was achieved, suggesting a good correlation between electrochemistry and spectrophotometry. Considering these results, the optimized gold nanoparticle-based label-free sensor can be used as a simple, rapid alternative towards classical methods for relative antioxidant capacity detection of hydrosoluble plant extracts.

The bioavailability of the administered drugs that reach the systemic circulation is the first point in resolving the pathology of patients. Albumin-based nanoparticles represent an increasingly used strategy to deliver cancer drugs into cells that otherwise cannot overcome biological barriers. In this work, rutin (Ru), a flavonoid with anticancer and antioxidant potential, was incorporated into bovine serum albumin nanoparticles (BSA-Ru NPs), developed using the desolvation method, and the entire system was characterized and evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–Vis absorption spectroscopy. The results showed that BSA and BSA–Ru NPs are uniformly distributed, have relatively large sizes, and have a time stability of more than 60%. Furthermore, the effect of these nanohybrids on the thermal stability of liposomal membranes was evaluated by surface plasmon resonance (SPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The viability evaluation was assessed by the tetrazolium salt (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) protocol in the fibroblast L929 line and a high level of biocompatibility, confirmed by SEM results, was found.