Preparation and characterization of hydrophobically-modified sodium alginate derivatives as carriers for fucoxanthin

• Published in: Food hydrocolloids 2024-12, Vol.157, p.110386, Article 110386
• Main Authors: Han, Lingyu, Zhai, Ruiyi, Hu, Bing, Williams, Peter A., Yang, Jixin, Zhang, Cunzhi, Dong, Nuo, Li, Tingting
• Format: Article
• Language: English
• Subjects: bioavailability; chemical bonding; encapsulation; esterification; fluorescence emission spectroscopy; Fucoxanthin; functional foods; hydrocolloids; Hydrophobic modification; hydrophobicity; ionic strength; Micellar-like aggregates; micelles; molecular weight; nuclear magnetic resonance spectroscopy; Sodium alginate; solubility; surface tension; Targeted delivery; thermogravimetry; X-ray diffraction
• ISSN: 0268-005X
• DOI: 10.1016/j.foodhyd.2024.110386

Micelles are nano-architectured structures capable of encapsulating hydrophobic substances in aqueous solutions, thereby improving their stability, solubility, and bioavailability to control the release of bioactive compounds. In this study, the sodium alginate backbone was modified via a hydrophobic modification scheme where octyl chains were covalently attached to the alginate chains via esterification reactions. Fourier-transformed infrared spectrometry (FTIR), 1H nuclear magnetic resonance (1H NMR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) were used to characterize the structure of the sodium alginate derivatives of varying molar mass (ALG-C8). Fluorescence spectroscopy, surface tension measurements, and dynamic light scattering (DLS) were employed to assess the self-assembly performance of ALG-C8. The three methods produced consistent results, indicating that self-assembly decreased with higher molar mass. The self-assembled ALG-C8 micelles were utilized to encapsulate fucoxanthin. The loading capacity (LC) and encapsulation efficiency (EE) were determined using UV–Vis spectrophotometry. The molar mass of ALG-C8 has a key influence on fucoxanthin loading and release behavior. The ALG-C8 molecules with the lowest molar mass produced micelles with the smallest hydration diameter, resulting in the highest LC and EE. Furthermore, the release of fucoxanthin is significantly influenced by the pH and ionic strength of the medium. ALG-C8 micellar-like aggregates exhibit resistance to low pH and high ionic strength environments, releasing encapsulated material at the target site under alkaline conditions. Therefore, synthesized ALG-C8 is a potential candidate for preparing pH-responsive self-assembled micellar-like aggregates, enabling targeted delivery and gradual release of hydrophobic functional food components. [Display omitted] •Hydrophobically-modified sodium alginate was prepared using octanoyl chloride.•The derivatives formed micellar-like aggregates in aqueous solution.•The aggregates formed were able to encapsulate fucoxanthin.•The fucoxanthin was released from the aggregates by changes in ionic strength and pH.