Antioxidant activity of bottlebrush copolymers and its self-assembly in mixed monolayers with cholesterol in the presence of cerium nitrate

The non-toxic amphiphilic bottlebrush polymers capable of self-organization on various interfaces and including cerium ions in structural assemblies without changing their biological properties have great importance for medicine and pharmacy. In the work, we studied the self-assembly in mixed monolayers of two copolymers – methoxy[oligo(propylene glycol)] methacrylate and methoxy[oligo(ethylene glycol)] methacrylate (PK) and its analogue with N-[3-(dimethylamino)propyl]methacrylamide) units quaternized with methyl iodide (PK_q), and cholesterol on the aqueous subphase-air interface in the present of cerium compounds. The effect of the polymer-cerium composition on the oxidoruductase activity was investigated as well. The cationic polymer PK_q was shown to exhibit higher specific activity of antioxidant enzymes than the non-ionic PK copolymer, increasing the activity of SOD by 20%, catalase – by 15%, GR – by 24%, G6PD – by 88%, and AlDH – by 10%. In the presence of cerium compounds (Ce(NO₃)₃, NH₄[Ce(NO₃)₃], CeO₂ nanoparticles) these effects increased significantly. Cholesterol in a monolayer of polymers contributed to an increase of compressibility modulus C_s⁻¹ under the influence of cerium ions in mixed monolayers by approximately two times compared to mixed Chol+polymers monolayers on water, and C_s⁻¹ became 640 mN/m for Chol+PK monolayers and 700 mN/m for Chol+PK_q monolayers. AFM and wettability study suggest elastic structure of transferred mixed monolayers that is suitable for designing a drug delivery system.