The Impact of Oxygen and Antimicrobial Tea Tree Oil Carrying Biomaterial on Cell Viability Under Hypoxic Conditions

Traditional wound treatment involves protecting the wound with dressing and administering antibiotics to prevent tissue infection due to bacteria. However, these methods are inadequate due to the side effects of antibiotics on healthy cells and microbial resistance to antibiotics. Therefore, new strategies involving the application of natural resources such as essential oils as antimicrobial agents in combination with biomaterials as wound dressings have been tested in the treatment of wounds. Furthermore, oxygen (O₂)-releasing biomaterials have attracted great interest due to the important role of O₂ in wound healing processes. However, the co-application of O₂ and essential oil as antimicrobial and cell-promoting agents has not been studied. In this context, we report a novel biomaterial capable of co-delivering O₂ and natural antimicrobial tea tree oil (TTO) for 15 and 5 days, respectively. The biomaterial consists of an alginate scaffold (Alg-PMOF-O) containing O₂-carrying nanomaterial, laponite and TTO. In vitro bacterial experiments have shown that O₂ release from Alg-PMOF-O is an additional parameter acting as an antibacterial agent to inhibit bacterial growth but is not sufficient alone to inhibit bacteria. 5 µL of TTO in Alg-PMOF-O is necessary to suppress both E. coli and S. aureus over a 1-day incubation period. The effect of TTO and O₂ alone or in combination on cell viability is examined using WST-1 and PrestoBlue assays. According to the WST-1 and PrestoBlue tests, the combined application of TTO and O₂ does not show any toxic effect on fibroblast cells under normoxic conditions during the 5-day incubation period. Under hypoxic conditions, the WST-1 test shows no toxic effect after only 1 day of incubation, while the PrestoBlue test shows no toxicity under hypoxia during both 1 and 5 days of incubation. On the other hand, the combined application of TTO and O₂ indicates toxic effects on cancer Malme-3M cells during both normoxic and hypoxic conditions over 1 and 5 days of incubation. This effect is confirmed by both the WST-1 and PrestoBlue tests. The overall results demonstrate that Alg-PMOF-O exhibits antibacterial activity while having a lower toxic effect on fibroblasts under hypoxic conditions, and therefore has potential for use as wound dressing.