Microfluidic design of bio-nanocapsules for algal oil delivery: Particle stability, oxidative stability, and bioaccessibility

Algal oil is a sustainable source of docosahexaenoic acid (DHA), but its high susceptibility to oxidation and hydrophobic nature limits its applications. To address these challenges, biopolymer nanocapsules (40.87–169.27 nm) were fabricated from shellac and phospholipids using microfluidic-mediated co-precipitation for algal oil delivery. Nanocapsule size increased from 78.51 nm to 152.96 nm with higher poor solvent ratios and decreased from 169.27 nm to 61.65 nm as total fluid velocity increased. Additionally, particle size was influenced by the phospholipid fraction, ranging from 40.87 nm to 61.65 nm, with the smallest size achieved at a shellac-to-phospholipid ratio of 2:3. Nanocapsule composition further affected particle stability, oxidative stability, and DHA bioaccessibility. A higher phospholipid fraction enhanced stability against pH fluctuations and thermal stress, while all nanocapsules exhibited stability during centrifugation and static storage, retaining over 93.01% DHA after 28 days at 25 °C. During accelerated storage (37 °C, 20 days), nanocapsules reduced hydroperoxide levels by 5.44- to 3.30-fold and secondary oxidation products by 2.62- to 1.79-fold compared to pure algal oil, with higher shellac content providing superior oxidative protection. Furthermore, the nanocapsules enhanced DHA bioaccessibility by a factor of 5.43–8.23 compared to pure algal oil, achieving a maximum DHA bioaccessibility of 54.31% at the highest phospholipid level. These findings provide valuable insights into designing advanced nano-colloids for enhancing the stability and bioavailability of bioactive lipids.