Green synthesis of CeO2 nanoparticles supported over silica gel: Its catalytic activity in the synthesis of pyrazolo[3,4-b]pyridines and its performance for the treatment of retinal damage in diabetic rat

Abstract

The preparation of metal nanoparticles formulated by herbal extracts is one of the friendly procedures due to simple, economical, convenient, and environmentally without toxic reagents. So, in current days, several eco-friendly methods for the efficient formulation of cerium oxide nanoparticles are supported over silica gel (SiO₂/CeO₂ NPs) by green tea aqueous extract as a reducing/stabilizing agent. The features of the obtained SiO₂/CeO₂ NPs by employing such methods as X-ray Diffract meter (XRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscope (FE-SEM). The TEM images showed that the SiO₂/CeO₂ NPs were well-dispersed with average sizes ranging from 10 to 30 nm with spherical shapes over the surface of SiO₂. After characterization of SiO₂/CeO₂ NPs, its catalytic activity was investigated in the one pot preparation of pyrazolo[3,4-b]pyridines through multi component condensation of aldehydes, 5-methylpyrazol-3-amine and Meldrum's acid. The related products achieved with good yields and the desired catalyst recycled for 7 run. The impact of SiO₂/CeO₂ NPs on the anti-inflammatory and antioxidant properties of retinal injury in diabetic rats was evaluated through examination. Diabetes was induced in the rats by administering Streptozotocin (60 mg/kg), intraperitoneally. Blood glucose levels were assessed to verify the existence of diabetes in the rats. They were subsequently separated into five distinct groups (n = 10), which consisted of a control group, a group with diabetic retinopathy that received a saline solution, and a group that was administered SiO₂/CeO₂ NPs (10, 30, and 90 µg/kg) over 8 weeks. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH) were evaluated as retinal tissue oxidative stress parameters. Additionally, the concentration of cytokines (IL10 and TNFα) was also measured. Retinal tissue was obtained for fundus photography, and assessments were conducted for retinal vessel diameter, retinal vascular permeability, and leukocytosis. After the treatment protocol period, the blood samples of diabetic rats were analyzed for blood glucose levels and HbA1c%. The findings of the study revealed that SiO₂/CeO₂ NPs led to a significant reduction in body weight and blood glucose levels in diabetic rats. The SiO₂/CeO₂ NPs -treated group showed a significant enhancement in the levels of SOD, CAT, and GSH activity in comparison to the diabetic retinopathy group. Furthermore, SiO2/CeO2 nanoparticles successfully decreased the elevated levels of TNFα, IL10, and NF-κB in the diabetic rat retina caused by Streptozotocin. The treatment with SiO₂/CeO₂ NPs also led to a notable reduction in vascular permeability and retinal leukocytosis. Moreover, the utilization of SiO₂/CeO₂ NPs in fundus photography demonstrated the alleviation of both functional and structural abnormalities linked to diabetes.