Formation and Characterization of Self-Assembled Rice Protein Hydrolysate Nanoparticles as Soy Isoflavone Delivery Systems

Self-assembled nanostructures from rice protein and its fractions: Molecular approaches, physicochemical principles, and functional applications

This review investigates the structural composition and physicochemical properties of rice protein (RP) and their functional applications, unraveling the molecular self-assembly approaches of rice protein isolates (RPI), rice protein hydrolysates (RPH), and their different fractions. RPI complexes with polysaccharides through both non-covalent (electrostatic, hydrogen bonding, hydrophobic and π-interactions) and covalent interactions (Schiff base and enzymatic reactions), whereas with polyphenols, it forms colloidal structures mainly through non-covalent forces. After enzymatic hydrolysis and chain segment reorganization, RPH exhibits enhanced interfacial activity and self-assembles into stable nanostructures, with applications in encapsulation and delivery of bioactive compounds. Owing to variations in conformation and amino acid composition, different fractions of RP can assemble into multilevel structures, including nanofibrils, branching clusters, and spherical nanoparticles, under specific environmental conditions. An in-depth exploration of these self-assembly principles can greatly enhance the physicochemical and structural properties of RP, thereby paving the way for a wide range of functional applications.

Development of barley proteins into peptides nanomicelles for encapsulation of hydrophobic bioactive ingredient

BACKGROUND

As natural polymer materials, barley proteins have been utilized to fabricate nanocarriers to encapsulate and delivery hydrophobic bioactive ingredients. However, as a result of the high proportion of hydrophobic amino acids and structural rigidity, barley protein-based nanocarriers tend to aggregate easily and have a low loading capacity, which greatly limits their application. In the present study, barley proteins were enzymolyzed to fabricate nanomicelles and then applied to encapsulate hydrophobic bioactive ingredient.

RESULTS

Self-assembled barley peptides could be obtained by controllable enzymolysis of barley proteins. The obtained barley peptides could self-assemble into nanomicelles (BPNMs) with a diameter of approximately 90 nm when the concentration was > 2.1 μg mL-1. Hydrophobic interaction, disulfide bonds and hydrogen bonds were involved in maintaining the structure of BPNMs. Six self-assembled peptides (QQPFPQ, QTPLPQ, QLPQIPE, QPFPQQPQLPH, QPFPQQPPFGL and QPFPQQPPFWQQQ) were identified and they were characterized by alternating arrangement of hydrophobic amino acids and hydrophilic amino acids. Moreover, BPNMs were utilized to encapsulate hydrophobic bioactive ingredient quercetin. When quercetin was encapsulated by BPNMs, its water solubility was significantly increased, being approximately 30-fold higher than free quercetin. Meanwhile, encapsulation of BPNMs could greatly increase quercetin stability. The interaction between BPNMs and quercetin occurred spontaneously, mainly driven by van der Waals forces and hydrogen bonds.

CONCLUSION

In the present study, BPNMs were successfully developed and could be used as a promising delivery system to improve the water solubility and stability of hydrophobic bioactive ingredients. © 2024 Society of Chemical Industry.

Caffeic Acid Phenethyl Ester Encapsulated in Self-Assemble Rice Peptides Nanoparticles: Storage Stability, In Vitro Release, and Their Interaction Mechanisms

Caffeic acid phenethyl ester (CAPE) is an important active component of propolis with many bioactivities. However, its efficiency and practical application are restricted due to its poor aqueous solubility and storage stability. In this study, a nanocarrier was fabricated to encapsulate CAPE using self-assembled rice peptides obtained by controllable enzymolysis. The physicochemical properties, encapsulation efficiency, and loading capacity of rice peptides nanoparticles (RPNs) were characterized. The storage stability, in vitro release, and interaction mechanisms between CAPE and RPNs were investigated. The results showed that RPNs, mainly assembled by disulfide bonds and hydrogen bonds, possessed an effective diameter of around 210 nm and a high encapsulation efficiency (77.77%) and loading capacity (3.89%). Importantly, the water solubility of CAPE was increased by 45 times after RPNs encapsulation. Moreover, RPNs encapsulation also significantly increased CAPE stability, about 1.4-fold higher than that of unencapsulated CAPE after 18-day storage. An in vitro release study demonstrated that RPNs could delay the release of CAPE, implying a better CAPE protection against extreme environments during digestion. Hydrogen bond and van der Waals force are the predominant interaction forces between RPNs and CAPE. Therefore, the newly developed nanoparticle is a potential delivery system that could effectively improve the aqueous solubility and stability of CAPE.