Advances in preparation, interaction and stimulus responsiveness of protein-based nanodelivery systems.

The improved understanding of the connection between diet and health has led to growing interest in the development of functional foods designed to improve health and wellbeing. Many of the potentially health-promoting bioactive ingredients that food manufacturers would like to incorporate into these products are difficult to utilize because of their chemical instability, poor solubility, or low bioavailability. For this reason, nano-based delivery systems are being developed to overcome these problems. Food proteins possess many functional attributes that make them suitable for formulating various kinds of nanocarriers, including their surface activity, water binding, structuring, emulsification, gelation, and foaming, as well as their nutritional aspects. Proteins-based nanocarriers are therefore useful for introducing bioactive ingredients into functional foods, especially for their targeted delivery in specific applications.This review focusses on the preparation, properties, and applications of protein-based nanocarriers, such as nanoparticles, micelles, nanocages, nanoemulsions, and nanogels. In particular, we focus on the development and application of stimulus-responsive protein-based nanocarriers, which can be used to release bioactive ingredients in response to specific environmental triggers. Finally, we discuss the potential and future challenges in the design and application of these protein-based nanocarriers in the food industry.

In Situ Self-Assembly of Nanoparticles into Waxberry-Like Starch Microspheres Enhanced the Mechanical Strength, Fatigue Resistance, and Adhesiveness of Hydrogels.

Owing to the diminishing resources and growing awareness of environmental issues, significant scientific attention has been paid to the development of physical gel materials using renewable and low-cost natural resources. Inspired by the strengthened mechanism of double-network and nanocomposite (NC) gels, we report a facile and green method to realize a mechanically stiff, fatigue-resistant, and adhesive-debranched waxy corn starch/poly(vinyl alcohol) double-crosslinked NC gel (W-Gel) skeleton material with dynamic noncovalent bonds. The in situ formation of debranched starch nanoparticles leads to self-assembly into three-dimensional waxberry-like microspheres, which act as physical cross-linkers by embedding themselves within network skeleton structures. The resulting hydrogel exhibited an excellent mechanical behavior, including a good stretchability over 1200% strain, a maximum compressive strength of up to 780.7 ± 27.8 kPa, and the ability to sustain as much weight as 4.6 kg (about 2000 times its own weight). Notably, the recovery efficiency exceeded 93% after the 60th compressive successive loading-unloading cycle at 50% strain. The hydrogel successfully adhered onto soft and hard substrates, such as skins, plastics, gauzes, glasses, and metals, manifesting in long-term, stable, sustained release of epigallocatechin gallate (EGCG). The EGCG-loaded W-Gels exhibited predominant antibacterial activity against both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Salmonella typhus).

Coordination of Covalent Cross-Linked Gelatin Hydrogels via Oxidized Tannic Acid and Ferric Ions with Strong Mechanical Properties.

The design of gelatin-based hydrogels with high mechanical strength, high gelation temperature, and a rapid self-healing property still presents a challenge to researchers. In the present study, single cross-linked gelatin-oxidized tannic acid (SC-GT/OTA) hydrogels were fabricated through covalent cross-linking between gelatin and tannic acid (TA) oxidized by using sodium periodate (NaIO4). Double cross-linked gelatin-OTA-FeCl3·6H2O (DC-GT/OTA/FeIII) hydrogels were also created using metal coordination bonds formed between the catechol groups present in OTA and FeIII in ferric chloride. As a result, the maximum gelling temperature of the SC-GT/OTA hydrogel (37 °C) was considerably higher than that of the pure gelatin hydrogel (15.4 °C). Moreover, the maximum values of compressive stress of SC-GT/OTA hydrogels increased significantly by almost seven times the original value as the molar ratio of NaIO4 to TA increased from 3:1 to 5:1. When the molar ratio of NaIO4 to TA was maintained at the constant of 4:1, the storage modulus values of DC-GT/OTA/FeIII hydrogels with the FeIII-to-TA molar ratio of 1.5:1 were three to 4 orders of magnitude higher than those of SC-GT/OTA hydrogels in the whole angular frequency range. The double cross-linked gelatin hydrogels developed in this research can be used widely in agriculture and material science fields.

Effect of annealing on the structural and physicochemical properties of waxy rice starch nanoparticles: Effect of annealing on the properties of starch nanoparticles.

Annealing offers a facile and green approach to the modification of starch. This study was the first to investigate the effect of annealing on the properties of waxy rice starch nanoparticles (SNPs). The spherical morphology of SNPs hardly changed after annealing, and the nanoscale size of the SNPs was maintained in the range of 50-120 nm. The relative crystallinity of modified SNPs increased from 53.71% to 63.46% after annealing at 55 °C for 48 h. The annealing treatment increased the melting temperature from 78.3 °C to 95.7 °C, but decreased the melting range from 30.8 °C to 25.3 °C. The increased 1047 cm-1:1022 cm-1 ratio suggested that annealing resulted in an efficient packing of double helices. This work suggests that annealing, a safe and green method, produces modifications which can improve the properties of SNPs and therefore expand their applications in the fields of food, nutraceuticals, and other materials.

Preparation of a Strong Gelatin-Short Linear Glucan Nanocomposite Hydrogel by an in Situ Self-Assembly Process.

Gelatin hydrogels exhibit excellent biocompatibility, nonimmunogenicity, and biodegradability, but they have limited applications in the food and medical industries because of their poor mechanical properties. Herein, we first developed an in situ self-assembly process for the preparation of gelatin-short linear glucan (SLG) nanocomposite hydrogels with enhanced mechanical strength. The microstructure, dynamic viscoelasticity, compression behavior, and thermal characteristics of the gelatin-SLG nanocomposite hydrogels were determined using scanning electron microscopy (SEM), dynamic rheological experiments, compression tests, and texture profile analysis tests. The SEM images revealed that nanoparticles were formed by the in situ self-assembly of SLG in the gelatin matrix and that the size of these nanoparticles ranged between 200 and 600 nm. The pores of the nanocomposite hydrogels were smaller than those of the pure gelatin hydrogels. Transmission electron microscopy images and X-ray diffraction further confirmed the presence of SLG nanoparticles with spherical shapes and B-type structures. Compared with pure gelatin hydrogels, the nanocomposite hydrogels exhibited improved mechanical behavior. Notably, the hardness and maximum values of the compressive stress of gelatin-SLG nanocomposites containing 5% SLG increased by about 2-fold and 3-fold, respectively, compared to the corresponding values of pure gelatin hydrogels.

Synergistic effect of glycerol and ionic strength on the rheological behavior of cellulose nanocrystals suspension system.

To broaden the application of cellulose nanocrystals (CNCs) in the field of biopolymer nanocomposites, a systematic assessment of the viscoelastic properties of CNC suspensions in the presence of glycerol (Gly) and/or sodium chloride (NaCl) was conducted. The viscosity, storage modulus (G'), and loss modulus (G'') increased with increasing concentrations of CNCs and Gly, respectively. Dramatically, the G' and G'' values were raised and tanδ (<1) decreased with the increasing addition of NaCl, indicating that the elastic properties of CNCs in NaCl solutions continuously strengthened, thereby the gel-like response of the network was enhanced. Moreover, the addition of 40% Gly significantly increased the values of G' and G'' for CNCs in NaCl solutions. This work demonstrates new findings related to the rheological properties of CNC gels with Gly/NaCl, and accounts for the interaction mechanisms between CNCs and CNCs/Gly/NaCl, with electrostatic interactions, hydrogen bonds, van der Waals forces, and Na+ bridging. We wish our study could better serve for future works based on design of CNCs in biomedical and packaging materials industries.

Characterizations of Pickering emulsions stabilized by starch nanoparticles: Influence of starch variety and particle size.

Pickering emulsions were first successfully fabricated by different types and sizes of corn, tapioca, sweet potato, and waxy corn starch nanoparticles as stabilizers. Photography, optical microscopy, confocal laser scanning microscopy, and rheology measurements were used to characterize Pickering emulsions stabilized by various starch nanoparticles. The results showed that tapioca, sweet potato, and corn starch nanoparticles were appropriate for Pickering emulsion stabilization because the three nanoparticles have nearly neutral wettability (θow ∼90°). Confocal microscopy revealed that intact and thick nanoparticle shells coated the surface of oil droplets. The Pickering emulsions stabilized by sweet potato and corn starch nanoparticles with a diameter that ranged from 100 to 220nm had better stability than those with a diameter either less than 100nm or more than 220nm. These results suggested that starch nanoparticles could be used as promising particulate emulsifiers to fulfill the demands of Pickering emulsions with stable characteristics.

Synthesis and study the properties of StNPs/gum nanoparticles for salvianolic acid B-oral delivery system.

To fabricate stable sized and shaped controlled release delivery systems for salvianolic acid B (Sal B), different food gums were individually added to short-chain glucan solution to prepare starch nanoparticles (StNPs)/gum nanocomposites by self-assembly, and Sal B was embedded in situ. The results showed that size of StNPs was reduced to ca. 45nm with the addition of chitosan and rosin, which decreased by over 50% than that of StNPs without the gum. The StNPs/guar gum nanocomposites had the largest size (109.2nm) among samples of StNPs with gums. The StNPs with chitosan and gum arabic exhibited an obvious core-shell structure. The loading capacities of Sal B in StNPs, StNPs/chitosan, and StNPs/gum arabic nanocomposites were 5.2, 8.26 and 8.08%, respectively. The in vitro release of Sal B from StNPs/gum nanocomposites were sustained and prolonged for over 12h, indicating that StNPs/gum nanocomposites are good candidates to control Sal B release.

Preparation and characterization of essential oil-loaded starch nanoparticles formed by short glucan chains.

Essential oils (EOs), including menthone, oregano, cinnamon, lavender, and citral, are natural products that have antimicrobial and antioxidant activities. However, extremely low water solubility, and easy degradation by heat, restrict their application. The aim of this work was to evaluate the enhancement in antioxidative and antimicrobial activities of EOs encapsulated in starch nanoparticles (SNPs) prepared by short glucan chains. For the first time, we have successfully fabricated menthone-loaded SNPs (SNPs-M) at different complexation temperatures (30, 60, and 90°C) by an in situ nanoprecipitation method. The SNPs-M displayed spherical shapes, and the particle sizes ranged from 93 to 113nm. The encapsulation efficiency (EE) of SNPs-M increased significantly with an increase in complexation temperature, and the maximum EE was 86.6%. The SNPs-M formed at 90°C had high crystallization and thermal stability. The durations of the antioxidant and antimicrobial activities of EOs was extended by their encapsulation in the SNPs.

The inhibition effect of starch nanoparticles on tyrosinase activity and its mechanism.

The objective of the current research was to investigate the effects of starch nanoparticles (SNPs) prepared from waxy maize, potato, normal corn, and tapioca starches on the activity of tyrosinase. As a main polyphenol oxidase, tyrosinase not only induces fruit and vegetable browning but also causes skin diseases by overproducing melanin. Herein, for the first time, we evaluated the inhibitory kinetics of SNPs on tyrosinase. It turned out that SNPs inhibited tyrosinase activity reversibly. The IC50 values of hollow nanoparticles, amylopectin nanoparticles, corn starch nanoparticles, and tapioca starch nanoparticles were 0.308, 0.669, 1.490, and 4.774 µM, respectively. Assay of fluorescence spectra demonstrated that SNPs quenched the tyrosinase intrinsic fluorescence. Moreover, binding constant and binding sites found that SNPs were bound to tyrosinase through van der Waals forces, hydrogen bonds, as well as electrostatic interactions. Analysis of circular dichroism indicated that the incorporation of SNPs into tyrosinase prompted conformational alteration of the enzyme. Furthermore, inhibition of browning by SNPs loading with l-dopa compound indicated that not only the tyrosinase activity was inhibited, but also SNPs decreased free dopa content by adsorption. This research on SNPs as potential inhibitors could give rise to advancement in the realm of anti-tyrosinase and have versatile applications in medicine, food, cosmetics, materials and drugs.