Cellular evaluation of superoxide dismutase mimics as catalytic drugs: Challenges and opportunities

Multifunctional Double-Loaded Oral Nanoplatform for Computed Tomography Imaging-Guided and Integrated Treatment of Inflammatory Bowel Disease

Excessive reactive oxygen species, disruption of the epithelial barrier, immune dysregulation, and gut microbiota imbalance are key factors driving the onset of inflammatory bowel disease (IBD) and complicating its treatment. Prompt diagnosis of diseases and precise delivery of therapeutic agents to inflamed intestinal sites offer promising targeted strategies for effectively treating IBD. Here, a barium sulfate-based nanoplatform (BaSO4@PDA@CeO2/DSP, BPCD) for synergistic delivery of nanozymes and drugs was developed. With enhanced colonic retention after oral drug delivery, this nanoplatform enables precise and effective targeting of inflammatory sites and CT imaging guidance to address multiple factors contributing to IBD. A comprehensive therapeutic effect was achieved through the synergistic action of cerium oxide with the optimized Ce3+/Ce4+ ratio and sustained release of dexamethasone sodium phosphate. Benefiting from superior gastrointestinal stability, the nanoplatform is highly effective in treating IBD by alleviating oxidative stress, modulating macrophage polarization balance, gut flora composition, and repairing the epithelial barrier. BPCD inhibits the development of IBD through multiple mechanisms and has superior biocompatibility, emerging as a practical alternative to traditional IBD therapies.

The relative impact of ligand flexibility and redox potential on the activity of Cu superoxide dismutase mimics

Two copper(II) complexes, [Cu(salbn)] and [Cu(py2bn)(OAc)]ClO4, formed with the Schiff-base ligands 1,4-bis(salicylidenamino)butane (H2salbn) and 1,4-bis(pyridin-2-ylmethyleneamino)butane (py2bn), have been prepared and characterized in solid state and in solution, and their ability to catalyse the dismutation of O2˙- has been evaluated in homogeneous medium and immobilized in a mesoporous matrix. The crystal structures show that [Cu(salbn)] possesses a distorted square-planar geometry, while [Cu(py2bn)(OAc)]ClO4 adopts a cis-distorted octahedral geometry. The two complexes experience structural changes in solution, and different spectroscopies were used to examine them. Moreover, their redox potentials are strongly affected by the solvent. In water, the complexes exist as [Cu(salbn)(H2O)] and [Cu(py2bn)(H2O)]2+ with Cu(II)/Cu(I) reduction potential at -361 mV and -229 mV, respectively, well different from redox potentials measured in acetonitrile. Although with a more unfavourable redox potential, [Cu(salbn)(H2O)] reacts with O2˙- faster than [Cu(py2bn)(H2O)]2+, with catalytic rate constants of 3.3 × 107 and 2.9 × 107 M-1 s-1, respectively, at pH = 7.8. Both complexes exhibit higher superoxide dismutase activity than the analogues with a shorter central alkyl chain. The observed catalytic rates essentially correlate with the ligand flexibility, rather than with the redox potential, which is also supported by the slower O2˙- dismutation rate when the complexes are immobilized by encapsulation into the channels of well-ordered mesoporous SBA-15 silica where the pore modifies the complex structures and restraints the ligand rearrangement.

Antibacterial effect of the metal nanocomposite on Escherichia coli

Ag nanocomposites (NAs) have been found to induce irreversible harm to pathogenic bacteria, however, NAs tend to aggregate easily when used alone. These nanocomposites also show increased toxicity and their underlying antibacterial mechanism is still unknown. In short, practical applications of NA materials face the following obstacles: elucidating the mechanism of antibacterial action, reducing cytotoxicity to body cells, and enhancing antibacterial activity. This study synthesized a core-shell structured ZnFe2O4 @Cu-ZIF-8 @Ag (FUA) nanocomposite with high antibacterial activity and low cytotoxicity. The nanocomposites achieved a 99.99 % antibacterial rate against Escherichia coli (E. coli) and tetracycline-resistant E. coli (T - E. coli), in under 20 min at 100 μg/mL. The nanocomposites were able to inactivate E. coli due to the gradual release of Cu2+, Zn2+, and Ag+ ions, which synergistically form •OH from FUA in an aerobic environment. The presence of •OH has significant effects on the antibacterial activity. The released metal ions combine with •OH to cause damage to the bacterial cell wall, resulting in the leakage of electrolytes and ions. Moreover, in comparison to NA, the toxicity of FUA is considerably reduced. This study is expected to inspire the development of other silver-based nanocomposite materials for the inactivation of drug-resistant bacteria.