Mechanistic characterization and inhibition of sphingomyelinase C over substituted Iron Schiff bases of chitosan adsorbed on glassy carbon electrode

New synthetic chitosan Schiff bases bearing pyranoquinolinone or benzonaphthyridine and their silver nanoparticles derivatives with potential activity as antioxidant and molecular docking study for EGFR inhibitors

In this study, two new carboxaldehydes 3, and 4 were synthesized by Vilsmeier-Haack formylation of 6-butyl-benzo[h][1,6]naphthyridine-2,5-dione 2 and 6-butyl-pyrano[3,2-c]quinolinone 1, respectively. Structures of newly synthesized compounds were achieved by IR, 1H NMR, 13C NMR, mass techniques, and elemental analyses. The two synthesized carboxaldehydes 3 and 4 were used as precursors for the synthesis of two new chitosan-based Schiff bases, CS1 and CS2. The new chitosan Schiff bases were grafted on silver nanoparticles, providing CS1/Ag and CS2/Ag structures. However, CS1 and CS2 and their silver nanoparticles were characterized by FT-IR, XRD, SEM-EDX, XRF, TEM, TGA, and DSC. The target compounds CS1, CS2, CS1/Ag, and CS2/Ag were assessed as radical scavengers against 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH%). The results showed that CS1 and CS2 had a better ability to scavenge DPPH radical than its unmodified chitosan. CS1/Ag and CS2/Ag, combining the unique properties of silver and Schiff bases, displayed excellent antioxidant activity (IC50, 59.13, and 32.54 μg mL-1, respectively). In addition, the previous compounds were tested in vitro for inhibition of epidermal growth factor receptor (EGFR) tyrosine kinase using the EGFR kinase assay kit (Cat. #40321). In particular, compound CS1/Ag displayed potent inhibitory activity towards EGFR with IC50 20.45 μg mL-1 compared to reference drug sorafenib (IC50 = 0.76 μg mL-1). The bioactivity of new chitosan Schiff bases was studied by molecular docking to see how they bind with the EGFR receptor. The results implied that CS1 has a higher binding energy than CS2 and CS regarding EGFR kinase, which agreed with the results obtained from the experimental EGFR inhibition assay.

A review on applications of chitosan-based Schiff bases

Biopolymers have become very attractive as they are degradable, biocompatible, non-toxic and renewable. Due to the intrinsic reactive amino groups, chitosan is vibrant in the midst of other biopolymers. Using the versatility of these amino groups, various structural modifications have been accomplished on chitosan through certain chemical reactions. Chemical modification of chitosan via imine functionalization (RR'CNR″; R: alkyl/aryl, R': H/alkyl/aryl and R″: chitosan ring) is significant as it recommends the resultant chitosan-based Schiff bases (CSBs) for the important applications in the fields like biology, catalysis, sensors, water treatment, etc. CSBs are usually synthesized by the Schiff condensation reaction between chitosan's amino groups and carbonyl compounds with the removal of water molecules. In this review, we first introduce the available synthetic approaches for the preparation of CSBs. Then, we discuss the biological applications of CSBs including antimicrobial activity, anticancer activity, drug carrier ability, antioxidant activity and tissue engineering capacity. Successively, the applications of CSBs in other fields such as catalysis, adsorption and sensors are demonstrated.

Effect of metal in Schiff bases of chitosan adsorbed on glassy carbon electrode in the inhibition of sphingomyelinase C toxin

This study was conducted to assess the catalytic electrode surface adsorption and capture properties of different metal chitosan derivatives in aqueous phosphate buffer solution (pH = 7.3). Early, recent work showed that the response of Iron chitosan complex with R = -CH₃ on the periphery, over blood red cells in presence of sphingomyelinase C was protected. The effect of others substituent (R = -Br, -Cl, -F, NO₂, -OCH₃, -H) on the periphery of the Schiff base ligand did not show correlation with the oxidation of sphingomyelinase C and its biological response. For this reason, various adsorbed metal (M = Fe of recent work, Cu, Ni and Co) complexes of chitosan and Schiff bases on glassy carbon electrode for the oxidation of sphingomyelinase C were investigated and compared, each one with -CH₃ group on the periphery of the Schiff base. UV-Vis and IR-TF spectroscopies, electrochemistry and microscopy assay were performed; then, the metal effect underlying. For the Schiff base, cobalt and copper complexes did not proved to be a remarkable cellular protector in presence of the enzyme, but the nickel complex showed to be a cellular protector at short time, this conclusion help to proposal a reaction mechanism for the electrochemical and biological studies.

Injectable Hydrogels for Localized Chemotherapy and Radiotherapy in Brain Tumors

Overall survival of patients with newly diagnosed glioblastoma (GBM) remains dismal at 16 months with state-of-the-art treatment that includes surgical resection, radiation, and chemotherapy. GBM tumors are highly heterogeneous, and mechanisms for overcoming tumor resistance have not yet fully been elucidated. An injectable chitosan hydrogel capable of releasing chemotherapy (temozolomide [TMZ]) while retaining radioactive isotopes agents (iodine, [¹³¹I]) was used as a vehicle for localized radiation and chemotherapy, within the surgical cavity. Release from hydrogels loaded with TMZ or ¹³¹I was characterized in vitro and in vivo and their efficacy on tumor progression and survival on GBM tumors was also measured. The in vitro release of ¹³¹I was negligible over 42 days, whereas the TMZ was completely released over the first 48 h. ¹³¹I was completely retained in the tumor bed with negligible distribution in other tissues and that when delivered locally, the chemotherapy accumulated in the tumor at 10-fold higher concentrations than when delivered systemically. We found that the tumors were significantly decreased, and survival was improved in both treatment groups compared to the control group. Novel injectable chemo-radio-hydrogel implants may potentially improve the local control and overall outcome of aggressive, poor prognosis brain tumors.