Seminar Prof. Sandra R. SIGNORELLA

Seminar team « Alzheimer’s, Amyloids and Bioinorganic Chemistry (Team F) »

Prof. Sandra R. SIGNORELLA

Instituto de Química Rosario (IQUIR, CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas (UNR), Rosario, Argentina

signorella@iquir-conicet.gov.ar

Effect of the Metal Environment and Immobilization on the Catalytic Activity of SOD Mimics

Numerous transition-metal-containing enzymes harness the rich redox chemistry of oxygen and its reduced forms. These metalloenzymes react with small oxygenated molecules at highly evolved metal sites, which feature environments optimized to facilitate various redox reactions. Such systems inspire the development of biomimetic catalysts capable of performing similar chemistry through the rational design of ligands that replicate the structural and electronic characteristics of the biological active site. Among these, superoxide dismutases (SODs) constitute a fundamental biological defense against the superoxide anion (O₂^•−). However, under various pathological conditions, O₂^•− production exceeds endogenous enzymatic capacity, leading to cellular damage. Given the limitations associated with using the exogenous enzyme as a therapeutic agent, low-molecular-weight bioinspired compounds capable of acting as catalytic antioxidants have emerged as an alternative. By employing suitable ligands, it is possible to tune the Mⁿ⁺/M^(n-1)+ redox potential and the metal site geometry to mimic enzymatic function; consequently, numerous mononuclear Mn and Cu complexes, as well as dinuclear CuZn complexes, have been synthesized and evaluated as SOD mimics [1–2]. Although several of these mimetic compounds have proven to be efficient antioxidants, the catalysts often undergo metal dissociation or oligomerization in solution. These issues can be overcome by covalently anchoring the catalyst to a solid support or incorporating it into a porous matrix [2–4]. Such confinement and isolation of the metal center prevent unwanted interactions and enhance complex stability, while preserving the properties of the homogeneous system. Among the various catalytic supports, mesoporous silicas stand out as ideal candidates for biomedical applications, as they offer tunable pore sizes, ordered arrangements, and biocompatibility.

In this presentation, I will describe some results regarding the antioxidant activity of various Mn-SOD and CuZn-SOD mimetics, as well as the key factors controlling redox processes when the catalysts are free or immobilized on a solid support.

References

[1] S.R. Signorella, C. Palopoli, G. Ledesma, Coord. Chem. Rev. 2018, 365, 75.

[2] M. Richezzi, Sh. Signorella, C. Palopoli, N. Pellegri, C. Hureau, S.R. Signorella, Inorganics 2023, 11, 359.

[3] Sh. Signorella, M. Bruno, G. Frattini, C. Palopoli, D. Moreno, N. Pellegri, V. Daier, S.R. Signorella, Dalton Trans. 2025, 54,4187.

[4] A. Aguirre, Sh. Signorella, M. Álvarez, M. Bruno, N. Pellegri, C. Palopoli, V. Daier, S.R. Signorella, C.R. Chim. 2026, doi: 10.5802/crchim.472.