Mariusz Pietrzak

Polyphenol-coated Fe ₃ O ₄ @Pt nanocomposites combine NIR-responsive photothermal activity with POD-like chemodynamic activity, promoting ˙OH generation and GSH oxidation to enhance oxidative stress.

Nanozymes, nanomaterials that mimic enzymatic activity, offer superior stability, tunability, and lower production costs compared to natural enzymes. To date, most nanozyme-based point-of-care (PoC) diagnostic systems have relied on oxidation reactions, such as oxidation of 3,3′,5,5′-tetramethylbenzidine, which often suffer from limited substrate stability and high background signal. This study investigates reduction reactions, particularly those involving tetrazolium salts, as an alternative route for signal generation in PoC devices. For this purpose, monometallic and bimetallic gold, palladium, and platinum nanoparticles were synthesized via chemical reduction using poly(vinyl alcohol) as a stabilizing agent. The resulting nanoparticles were uniform in size and morphology. Their catalytic performance was confirmed through the reduction of 4-nitrophenol. The tetrazole salts were selected as promising substrates for application in PoC settings and further explored by examining the nanozyme-based reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The nanozymes catalyzed the reduction of MTT in the presence of sodium borohydride, producing a distinct colorimetric signal under selected conditions. The effects of reducing agent concentration, buffer pH, and potential interferents were evaluated, with performance suitable for PoC devices achieved at basic pH and low borohydride concentration. Interference studies showed negligible MTT reduction in the presence of physiological levels of ascorbic acid, human serum albumin, and 10% concentration of human serum. Finally, a proof-of-concept lateral flow assay demonstrated successful signal generation through nanozyme-catalyzed MTT reduction. Results establish tetrazolium salts as suitable substrates for nanozyme-enhanced PoC diagnostics and highlight reduction-based chromogenic systems as a viable alternative to traditional oxidation-based assays.

We report a Fe₃O₄@Pt@poly-LDOPA nanozyme that displays enhanced peroxidase (POD)-like activity. Polymerisation of levodopa onto the surface of Fe₃O₄@Pt yields a carboxyl-rich poly-LDOPA shell that is available for bioconjugation with antibodies and other types of receptors. Physicochemical characterisation confirmed the integrity of the Fe₃O₄ core, successful Pt modification, and formation of the polymer coating under acidic and basic conditions. Steady-state kinetic analysis using the Michaelis–Menten model revealed robust catalytic performance toward both substrates: for H₂O₂, V_max = 4.0 × 10⁻⁸ M·s⁻¹ and K_m = 25.13 mM; for TMB, V_max = 6.07 × 10⁻⁸ M·s⁻¹ and K_m = 0.229 mM, indicative of high turnover and strong apparent affinity for the chromogenic substrate. A nanozyme-linked immunosorbent assay for the SARS-CoV-2 nucleocapsid was developed. The anti-nucleocapsid antibodies were immobilised onto Fe₃O₄@Pt@poly-LDOPA via EDC/NHS. In buffer, the calibration range (1.0–100 ng·mL⁻¹) afforded an LOD of 6.95 ng·mL⁻¹. In 10% human serum, reduced background and improved nanozyme dispersion yielded a linear low-concentration response (0.1–10 ng·mL⁻¹), with an LOD of 0.0036 ng·mL⁻¹. These results establish Fe₃O₄@Pt@poly-LDOPA as a promising inorganic–organic nanozyme platform that combines catalytic effectiveness, magnetic manipulability, and facile bioconjugation for immunosensing of various disease-related biomarkers.

In general, this manuscript describes relatively simple, however, important studies concerning the stability of silver nanoparticles. I have several comments and questions: * What was the role of citrate during the synthesis? Is it justified to tre...

Laser toners appear as attractive materials for barriers and easily laminated interphases for Lab-on-a-Foil microfluidics, due to the excellent adhesion to paper and various membranes or foils. This work shows for the first time a comprehensive study on the adsorption of antibodies on toner-covered poly(ethylene terephthalate) (PET@toner) substrates, together with assessment of such platforms in rapid prototyping of disposable microdevices and microarrays for immunodiagnostics. In the framework of presented research, the surface properties and antibody binding capacity of PET substrates with varying levels of toner coverage (0–100%) were characterized in detail. It was proven that polystyrene-acrylate copolymer-based toner offers higher antibody adsorption efficiency compared with unmodified polystyrene and PET as well as faster adsorption kinetics. Comparative studies of the influence of pH on the effectiveness of antibodies immobilization as well as measurements of surface ζ-potential of PET, toner, and polystyrene confirmed the dominant role of hydrophobic interactions in adsorption mechanism. The applicability of PET@toner substrates as removable masks for protection of foil against permanent hydrophilization was also shown. It opens up the possibility of precise tuning of wettability and antibody binding capacity. Therefore, PET@toner foils are presented as useful platforms in the construction of immunoarrays or components of microfluidic systems.