Using fluorochemical as oxygen carrier to enhance the growth of marine microalga Nannochloropsis oculata

Chitosan/PVA Hetero-Composite Hydrogel Containing Antimicrobials, Perfluorocarbon Nanoemulsions, and Growth Factor-Loaded Nanoparticles as a Multifunctional Dressing for Diabetic Wound Healing: Synthesis, Characterization, and In Vitro/In Vivo Evaluation

Diabetic foot ulcers remain one of the most difficult-to-treat complications of diabetes and may seriously threaten the life of patients since it frequently results in limb loss due to amputation, suggesting that an effective therapeutic strategy is still urgently needed. In this study, a chitosan-based heterogeneous composite hydrogel encapsulating perfluorocarbon emulsions, epidermal growth factor (EGF)-loaded chitosan nanoparticles, and polyhexamethylene biguanide (PHMB) named PEENPPCH was developed for diabetic wound healing. The PEENPPCH could sustainably release EGF and PHMB in an ion-rich environment to exert antibacterial effects and promote cell growth for wound repair. In addition, the PEENPPCH can provide anti-inflammatory effects functioned by its main constituent of chitosan. Moreover, the PEENPPCH can proactively offer oxygen delivery through the incorporation of perfluorocarbon and, therefore, is able to alleviate hypoxia conditions on diabetic wounds. These functionalities enabled a markedly enhanced wound healing efficacy on diabetic rats treated with the PEENPPCHs, including thorough re-epithelization, a reduced inflammatory response, faster collagen deposition, and advanced collagen maturation resulting in a 95% of wound closure degree after 15 days that was 12.6% (p < 0.05) higher than the value of the group treated with the commercial dressing HeraDerm. Given the aforementioned advantages, together with the known merits of hydrogels, the developed PEENPPCH is anticipated to be a feasible tool for clinical diabetic wound treatment.

Multifunctional fluorocarbon photobioreactor system: a novel integrated device for CO2 segregation, O2 collection, and enhancement of microalgae growth and bioproductions

An enhanced greenhouse effect due to high CO₂ emissions has become one of the most concerning issues worldwide. Although plant/algae-mediated approaches have been extensively used for CO₂ segregation in the last decades, these methods are generally aimed at environment protection. In contrast, less attention has been given to CO₂ manipulation that has regrettably caused a decrease in the commercial availability of the associated technologies. To generate a system for practical use, a synthetic fluorocarbon photobioreactor system (FCPBRS) consisting of a CO₂ isolation unit, a gas modulation unit, an O₂ collection unit, and a microalgal culture chamber was developed in this study. After injecting a 60%-N₂/40%-CO₂ gas mixture into the CO₂ isolation unit for 10 days, the results showed that the FCPBRS enabled a > 93% CO₂ separation efficiency using a fluorocarbon liquid FC-40 as the CO₂ adsorbent. In addition, the growth rate of Nannochloropsis oculata was significantly enhanced when cultured with 20 mL min^-1 of the FC-40 flow containing 2% CO₂ throughout the time course, resulting in 4.7-, 4.6-, and 4.5-fold (P < 0.05 for each) increases in biomass, total lipid, and eicosapentaenoic acid yields, respectively, compared to the aerated group without FC-40. Moreover, approximately 1600 mL of photosynthetic O₂ with a ~ 80% collection efficiency was obtained in the O₂ collection unit within 10 days of FCPBRS operation. These outcomes indicate that the FCPBRS may provide a feasible means to simultaneously achieve CO₂ isolation, O₂ collection, and enhanced microalgae bioproductions.

Influence of oxygen on the biosynthesis of polyunsaturated fatty acids in microalgae

As one of the most important environmental factors, oxygen is particularly important for synthesis of n-3 polyunsaturated fatty acids (n-3 PUFA) in microalgae. In general, a higher oxygen supply is beneficial for cell growth but obstructs PUFA synthesis. The generation of reactive oxygen species (ROS) under aerobic conditions, which leads to the peroxidation of lipids and especially PUFA, is an inevitable aspect of life, but is often ignored in fermentation processes. Irritability, microalgal cells are able to activate a number of anti-oxidative defenses, and the lipid profile of many species is reported to be altered under oxidative stress. In this review, the effects of oxygen on the PUFA synthesis, sources of oxidative damage, and anti-oxidative defense systems of microalgae were summarized and discussed. Moreover, this review summarizes the published reports on microalgal biotechnology involving direct/indirect oxygen regulation and new bioreactor designs that enable the improved production of PUFA.