Ligands as copper and nickel ionophores: Applications and implications on wastewater treatment

Retinoic acid mitigates the NSC319726-induced spermatogenesis dysfunction through cuproptosis-independent mechanisms

Copper ionophore NSC319726 has attracted researchers' attention in treating diseases, particularly cancers. However, its potential effects on male reproduction during medication are unclear. This study aimed to determine whether NSC319726 exposure affected the male reproductive system. The reproductive toxicity of NSC319726 was evaluated in male mice following a continuous exposure period of 5 weeks. The result showed that NSC319726 exposure caused testis index reduction, spermatogenesis dysfunction, and architectural damage in the testis and epididymis. The exposure interfered with spermatogonia proliferation, meiosis initiation, sperm count, and sperm morphology. The exposure also disturbed androgen synthesis and blood testis barrier integrity. NSC319726 treatment could elevate the copper ions in the testis to induce cuproptosis in the testis. Copper chelator rescued the elevated copper ions in the testis and partly restored the spermatogenesis dysfunction caused by NSC319726. NSC319726 treatment also decreased the level of retinol dehydrogenase 10 (RDH10), thereby inhibiting the conversion of retinol to retinoic acid, causing the inability to initiate meiosis. Retinoic acid treatment could rescue the meiotic initiation and spermatogenesis while not affecting the intracellular copper ion levels. The study provided an insight into the bio-safety of NSC319726. Retinoic acid could be a potential therapy for spermatogenesis impairment in patients undergoing treatment with NSC319726.

Reduced Chitosan as a Strategy for Removing Copper Ions from Water

Toxic heavy metals are priority pollutants in wastewater, commonly present in dangerous concentrations in many places across the globe. Although in trace quantities copper is a heavy metal essential to human life, in excess it causes various diseases, whereby its removal from wastewater is a necessity. Among several reported materials, chitosan is a highly abundant, non-toxic, low-cost, biodegradable polymer, comprising free hydroxyl and amino groups, that has been directly applied as an adsorbent or chemically modified to increase its performance. Taking this into account, reduced chitosan derivatives (RCDs 1-4) were synthesised by chitosan modification with salicylaldehyde, followed by imine reduction, characterised by RMN, FTIR-ATR, TGA and SEM, and used to adsorb Cu(II) from water. A reduced chitosan (RCD3), with a moderate modification percentage (43%) and a high imine reduction percentage (98%), proved to be more efficient than the remainder RCDs and even chitosan, especially at low concentrations under the best adsorption conditions (pH 4, R_S/L = 2.5 mg mL^-1). RCD3 adsorption data were better described by the Langmuir-Freundlich isotherm and the pseudo-second-order kinetic models. The interaction mechanism was assessed by molecular dynamics simulations, showing that RCDs favour Cu(II) capture from water compared to chitosan, due to a greater Cu(II) interaction with the oxygen of the glucosamine ring and the neighbouring hydroxyl groups.

A New Schiff Base Organically Modified Silica Aerogel-Like Material for Metal Ion Adsorption with Ni Selectivity

Nickel has several industrial uses and is a valuable metal, making its selective separation and recycling a priority goal. A novel adsorbent, a Schiff base organically modified silica (ORMOSIL) aerogel, was prepared, for selective nickel removal from wastewater with other metal ions, by including a salen ionophore in the silica-based network. The newly developed adsorbent takes advantage of the salen’s selectivity and of the high porosity of silica aerogels. The aerogel-like adsorbent was prepared via sol-gel chemistry, using a coprecursor approach and ambient pressure drying. The inclusion of the Schiff base in the silica network was accomplished by reacting an amine-containing silica precursor with an aldehyde and confirmed by nuclear magnetic resonance (NMR) analysis. The adsorbent shrunk only 10% after evaporative drying, which resulted in a highly porous material (85% porosity, 4 cm3 g−1 specific pore volume). The low surface area of 28 m2 g-1 was due to the predominantly macroporous structure of the material (mean pore diameter of 563 nm). Adsorption isotherms and kinetic curves with single and binary mixtures of cations at room temperature were used to assess the selectivity of the adsorbent. The adsorption follows a BET (Brunauer-Emmett-Teller) trend. Due to the proximity of the oxygen and nitrogen atoms in the salen and steric hindrance from their neighboring atoms, it is likely that only the smallest hydrated cations can act as a coordination center and interact with both donor atoms. Thus, nickel was fairly removed (50 mg g-1), while other cations barely interacted with the adsorbent (cadmium adsorption maximum of 5 mg g-1). The estimated selectivity coefficient for nickel ranges from 1.8, in relation to copper, to 9.4 relatively to cadmium, which can be relevant for the separation of nickel in several industrial contexts, for instance, from electroplating sludge.