**10. Poly (Trolox Ester) Polymers**

Poly Trolox ester polymers are useful antioxidants in human cells based on their ability to relieve oxidative stress in injured cells and resolve iron particle toxicity at the nanoscale [107,108]. Even though there is a broad class of compounds that exhibits antioxidant behavior (including α-lipoic acid, N-acetyl cysteine, melatonin, gallic acid, captopril,

taurine, catechin, and quercetin), the biological function of most is impaired by oxidative stress-linked biological incompatibility at the nanoscale [108]. Wattamwar et al. claimed that poly Trolox ester polymers were able to overcome these barriers by inhibiting the response of free radicals while retaining higher compatibility with medical devices. In contrast to quercetin, lignin, and polydopamine, poly Trolox ester polymers are a class of synthetic analogs of vitamin E (with superior hydrophilic, tunable particle sizes, antioxidant properties) [108]. The materials can be synthesized via a facile single emulsion technique; the nanoparticle concentration is varied over time to achieve the desired nanoparticle sizes.

Resolving iron particle toxicity is a priority in biomedical applications, given that the risk is elevated by the frequency of medical diagnosis and treatment (iron supplements for anemia and MRI contrast agents). Iron particle toxicity was mitigated through targeted delivery of functionalized poly Trolox ester polymers to the platelet endothelial cell adhesion molecules (PECAM-1) [101]. In theory, the modification of the pro-oxidant and antioxidant activity of poly Trolox ester polymers could be applied in virtually all high-oxidative-stress environments within the cells. However, in reality, this might not be feasible considering that poly (Trolox ester) nanoparticles' ability to induce/inhibit cellular oxidative stress depends on advanced programming of the molecules, based on knowledge of the molecular compounds being oxidized and the cumulative oxidative status of the cells [6]. If the listed variables are not known, the cellular function of poly (Trolox ester) nanoparticles might be impaired. Such complexities limit the clinical application of Trolox esters.
