Synthesis of citric acid-coated nanomaterials releasing oxygen and antioxidant vitamin E and investigation of their effects on healthy and cancer cells under hypoxic and normoxic conditions

Hypoxia and inflammation are in a reciprocal interaction. Oxygen deficiency not only results in prolonged inflammation but also contributes to its continuation by sustaining immune responses. Although various nanocarriers have been designed for oxygen transport or antioxidant drug delivery, this study uniquely combines both functions in a single nanomaterial platform. Here, we report the synthesis of an oxygen-carrying nanomaterial (CPE) functionalized with antioxidant citric acid and loaded with vitamin E. CPE particles exhibit an initial burst release within the first 24 hours, followed by a pH-dependent sustained release phase. In an acidic environment (pH 6.0), cumulative release reaches a maximum of ~69% by the end of day 7. Additionally, CPE particles exhibit a continuous O2 release profile over 7-days, reaching a peak of ~11.8% at 96 hours and maintaining an O₂ level close to physiological oxygen levels (>6%) in a hypoxic environment by the end of day 7. In vitro experiments are consistent with each other in terms of cell viability, ROS, and NO production. In general, CPE increases the viability of healthy cells by 25% while decreasing ROS, NO and lipid peroxidation, and increases ROS, NO and lipid peroxidation in cancer cells while decreasing cell viability by 11% in hypoxic environments. The observed results are interpreted as follows: Cancer cells typically exhibit high basal ROS levels and limited antioxidant buffering capacity. Therefore, an increase in oxygen availability, combined with citric acid and vitamin E, can cause acute oxidative imbalance. Under these conditions, moderate ROS accumulation can increase oxidative stress and lipid peroxidation, ultimately inhibiting cancer cell proliferation. In contrast, healthy cells possess more efficient antioxidant defense systems. The presence of oxygen, citric acid, and vitamin E together can support normal oxygen-dependent metabolism while protecting cell membranes from lipid peroxidation, thanks to citric acid's metal chelation properties and vitamin E's antioxidant activity.