A simplified kinetic model for the quantitative analysis of a potentiometric, pH-based urea biosensor is presented. The device was an electrolyte–insulator–semiconductor capacitor (EISCAP) with a pH-sensitive Ta₂O₅ gate functionalized by a polyallylamine hydrochloride (PAH)/urease bilayer. Within the steady-state approximation, the kinetic equations yielded an implicit algebraic relation linking the bulk urea concentration to the local pH at the sensor surface. Numerical solution of this equation, combined with a fitting routine, provides the apparent Michaelis–Menten constant ($K_M$) and the normalized maximum reaction rate (${\overline{k}}_V$). Validation against the literature data confirmed the reliability of the approach. Experimental results were then analyzed in both phosphate buffer (PBS) and artificial urine (AU), covering urea concentrations of 0.1–50 mM. The fitted parameters showed comparable $K_M$ values of 10.9 mM (PBS) and 32.4 mM (AU), but strongly different ${\overline{k}}_V$ values: $2.2\times {10}^{-4}$ (PBS) versus $8.6\times {10}^{-7}$ (AU). The three-order reduction in AU was attributed to the inhibitory effects inherent to complex biological fluids. These findings highlight the importance of the model-based quantitative analysis of EISCAP biosensors, enabling the accurate characterization of immobilized enzyme layers and guiding optimization for applications in realistic sample matrices.

Agriculture faces numerous challenges: infectious diseases through phytopathogens and soil nutrient deficiencies hinder plant growth, reducing crop yields. Biopolymer nanocomposites offer promising solutions to these challenges. In this work, we synthesize and characterize novel bionanocomposites (ι-CG-Mn) of manganese (hydr)oxide nanoparticles (approx. 3 to 11 nm) embedded in the matrix of the natural polysaccharide ι-carrageenan (ι-CG). Using spectroscopic methods we verify the presence of the nanoparticles in the polymer matrix while leaving the polysaccharide structural characteristics unaffected. Elemental analysis determines the mass content of metal ions in the ι-CG-Mn to be approx. 1 wt%. Electron microscopy techniques show the supramolecular organization of the ι-CG-Mn and the homogeneous nanoparticle distribution in the polymer matrix, while thermal analysis reveals that the bionanocomposite maintains high thermal stability. Moreover, the co-incubation of the phytopathogen Clavibacter sepedonicus with ι-CG-Mn inhibits the pathogen growth by 67% compared to the control. Our bionanocomposites demonstrate (1) strong bactericidal activity and (2) potential as microfertilizers that stimulate agricultural plant growth through the dosage of metal ions. These properties arise from the bioactivity of the widely available, naturally sulfated polysaccharide biopolymer matrix, combined with the antimicrobial effects of manganese (hydr)oxide nanoparticles, which together enhance the efficacy of the biocomposite. The non-toxic, biocompatible, and biodegradable nature of this biopolymer satisfies the high environmental demands for future biotechnological and agricultural technologies.

Background: Stroke is the leading cause of mortality and disability worldwide. The goal of this study was to design stable, small-sized polyethylene glycol (PEG)/albumin nanoparticles (NPs) for delivering drugs targeting various phases of stroke recovery. Methods: RP-HPLC (Reversed-Phase High-Performance Liquid Chromatography) and spectrophotometry were used to assess the stability and effectiveness of the drug carriers. The dynamic light scattering (DLS) technique was employed to evaluate the size and zeta potential of the particles. The integrity of the blood–brain barrier (BBB) in laboratory rats was assessed by measuring Evans Blue (EB) leakage after intracranial injection of 3% H₂O₂. AutoDock Tools 1.5.7 was used to analyze the compatibility of the polymers with albumin. Results: The particles exhibited high drug-loading efficiency. In all groups, the most prevalent particle size averaged 211.09 ± 92.72 nm. The drug-loaded particles exhibited prolonged circulation and had a half-life (T₁/₂) ranging from 7.64 to 13 days. Furthermore, both albumin particles and PEGylated albumin carriers loaded with dexamethasone and allopurinol significantly preserved blood–brain barrier (BBB) integrity (2.92 ± 0.4 µg, p < 0.04), as indicated by reduced Evans Blue (EB) extravasation (6.73 ± 0.58 µg) compared to the control group (9.12 ± 1.2 µg, p < 0.04, t-test). Discussion: The protective effect of albumin carriers on the BBB may be attributed to an increase in blood oncotic pressure, which helps limit edema formation. PEG/albumin drug-loaded carriers demonstrated greater stability, as indicated by their zeta potential, and exhibited a more pronounced BBB-preserving effect due to the combined actions of albumin and the loaded drugs. Conclusion: In this study, stable, layered NPs carrying different drugs were synthesized that could be applied for the treatment of experimental stroke.

Corrigendum to: PEGylated Albumin-Based Drug Carriers for the Treatment of Experimental Stroke