Molecular mechanism underlying the effects of temperature and pH on the size and surface charge of octenylsuccinated oat β-glucan aggregates

Thiolated dextrin nanoparticles for curcumin delivery: Stability, in vitro release, and binding mechanism

To achieve the effective loading and delivery of curcumin, novel disulfide-crosslinked nanoparticles based on modified dextrin were developed for the encapsulation of curcumin. Thiolated dextrin (Dt-SH) was obtained via sodium periodate oxidation and cysteamine grafting. The Dt-SH exhibited a rough, flake-like morphology, was classified as an amorphous material and demonstrated enhanced enzyme resistance. Subsequently, spherical nanoparticles with sizes ranging from 92.52 to 157.12 nm and zeta potentials between +23.59 and + 29.90 mV were self-assembled in an aqueous solution. Thiol modification promoted interconnection and aggregation of the nanoparticles. These nanoparticles exhibited pH-dependent size variations. Taking curcumin as a hydrophobic model, nanoparticles showed intestinal targeted release in vitro. Fluorescence spectroscopy and thermodynamic analysis indicated that curcumin bound to Dt-SH nanoparticles primarily through hydrogen bonding and van der Waals forces, with hydrophobic interactions contributing. These findings supported the potential of thiolated dextrin nanoparticles in the effective delivery of hydrophobic compounds.

Spatial exposure and oxidative accumulation of reactive hydroxyl groups in starch retrogradation through transglucosidase and hexose oxidase

To investigate the potential of inhibiting starch retrogradation by modifying the functional groups of starch, transglucosidase (TG) was used to facilitate active hydroxyl groups to be exposed through increasing branching degree. Subsequently, hexose oxidase (HOX) advantageously promoted the oxidation of starch chains and increased spatial repulsion of starch backbone. The Fukui Function revealed that the oxygen atoms at the C3 and C4 positions on glucose units had a higher oxidation tendency. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis confirmed that the reactive hydroxyl groups underwent an oxidation process with increasing HOX treatment time. From the crystal structure parameters, the c-axis of native corn starch modified by TG for 16 h and HOX for 48 h (or TGHOX-48) was shortened from 16.92 to 16.32 Å and in the long-term retrogradation, TGHOX-48 exhibited the lowest starch retrogradation rate (0.22).

Supramolecular assembly strategy of modified starch chains for achieving recyclable emulsion biocatalysis within a narrow pH range

Stimuli-responsive Pickering emulsions are promising in biocatalysis for their ease of product separation and emulsifier recovery. However, pH responsiveness, though simple and cost-effective, faces challenges in precise control and narrow transition ranges, limiting its use in enzymatic catalysis. Herein we introduced amorphous octenyl succinic anhydride-modified debranched starch chains (Am-OSA-St) to control emulsion properties within a pH range suitable for enzymatic catalysis. By adjusting the OSA group density and molecular weight, Am-OSA-St allowed emulsions to transition reversibly between pH 7.3 and 5.5 and enabled self-recycling through supramolecular self-assembly. Employing molecular dynamics simulations and physicochemical characterization, we elucidated the control mechanism of oil-water interfaces via the microstructure transformation of Am-OSA-St. The findings revealed that protonation of carboxylate groups disrupted the charge balance and polarity of starch chains, leading to strong electrostatic and van der Waals interactions that drove self-assembly. This entanglement caused starch chains in the aqueous phase to "drag" those at the oil-water interface, moving them into the aqueous phase and forming micelles. These micelles, with a hydrophobic interior and hydrophilic exterior, prevented re-adsorption. Testing with Candida antarctica Lipase B (CALB) and N-acetylneuraminic lyase showed that the pH-regulated emulsion system maintained excellent efficiency and cycling stability in mild conditions.

Novel self-assembled micelles of dual-modified dextrin with pH responsiveness via grafted octenyl succinic anhydride and cysteamine for curcumin delivery

In this study, a novel dextrin-based micelle (OSAD-SH), dual-modified with octenyl succinic anhydride (OSA) and cysteamine, was developed to address the acid instability issues of micelle modified only by OSA and designed for curcumin delivery. Three amphiphilic OSAD-SH polymers with different free sulfhydryl content were first synthesized. The study demonstrated that OSAD-SH micelles exhibited strong self-assembly properties, appearing as spheres with diameters ranging from 92.41 to 194.20 nm. Blank micelles showed good dilution resistance, as well as stability against acid, thermal, and ionic strength. The curcumin encapsulated by the micelles was in an amorphous state. In vitro release experiment demonstrated that curcumin released from OSAD-SH micelles exhibited pH responsiveness. The Ritger-Peppas model effectively predicted the release behavior of curcumin, which followed a super case-II transport. The OSAD-SH micelle will be a promising nanocarrier for improving the physicochemical properties of curcumin in food fields.

Oxidized paramylon self-assembled nanoparticles loaded with fucoxanthin attenuate insulin resistance in HpeG2 cells

Fucoxanthin (Fx) has garnered significant interest due to its exceptional biological properties. However, its efficacy in enhancing food quality and human health is contingent upon the solubility of the compound in water and its physicochemical stability. Therefore, nanocarriers must be developed to enhance the stability and biocompatibility of Fx. In this study, oxidized paramylon and Fx self-assembled nanoparticles (Fx-OEP) were prepared via the anti-solvent method, with a loading rate of 82.47 % for Fx. The Fx-OEP exhibited robust storage and photostability. In vitro simulated digestion assays demonstrated that Fx-OEP effectively protected Fx from premature gastric release, while achieving a release efficiency of 72.17 % in the intestinal phase. Fx-OEP has the capacity to scavenge a range of reactive oxygen species (ROS) induced by cellular oxidative stress. Treatment with Fx-OEP resulted in a significant reduction in ROS accumulation in insulin-resistant HepG2 cells, which was attributed to the activation of the nuclear factor E2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) pathway. This, in turn, activated insulin receptor substrate 1/glucose transporter type 4 (IRS1/GLUT4), promoting cellular glucose absorption and utilization. These findings indicate the potential of self-assembled nanoparticles based on oxidized paramylon as a new type of nanocarrier for delivering hydrophobic substances.

Effects of side-chain lengths on the structure and properties of anhydrides modified starch micelles: Experimental and DPD simulation studies

Anhydride-modified starch micelles have great potential in the delivery of hydrophobic guest molecules. This study aimed to experimentally explore the effects of side-chain lengths on the structure and properties of anhydride-modified starch micelles, and to visualize the self-assembly and loading process of these micelles through Dissipative particle dynamics (DPD) simulations. Starch micelles could only form when the carbon chain length exceeded four. The highly hydrophobic C18 starch micelle exhibited the minimum particle size (65 nm) and maximum loading capability (59.10 μg/mg). For each addition carbon atom in the anhydride side chains, the critical micelle concentration (CMC) of starch micelles decreased average of 1.79 %. Thermodynamic results showed that the micellization was an entropy-dominated driven process, and longer carbon chains enhanced the stability of starch micelles. DPD results showed that the starch chains formed the small clusters then spherical aggregates and finally core-shell structure spherical micelle. Curcumin was loaded into micelles by adjoint aggregation-micellization-adsorption mechanism. Overall, this study provides microscopic insight into the micellization and drug-loading mechanisms for anhydrides modified starch micelles.

Molecular mechanism underlying coencapsulating chrysophanol and hesperidin in octenylsuccinated β-glucan aggregates for improving their corelease and bioaccessibility

Chrysophanol and hesperidin are natural nutraceuticals that exhibit synergistic bioactivities, but their hydrophobicity limits their applications, and it is unclear whether coencapsulation can improve their solubility and release behaviors. The objective of this work was to coencapsulate chrysophanol and hesperidin by octenylsuccinated β-glucan aggregates (OSβG-Agg) and to reveal how coencapsulation improves their release and bioaccessibility. Mechanisms underlying the hypothesis of beneficial effects in coloading, corelease and bioaccessibility were revealed. The solubilization of OSβG-Agg was due to hydrogen-bonding among β-glucan moieties of OSβG and hydroxyl groups of chrysophanol and hesperidin and hydrophobic interactions among octenyl chains of OSβG and hydrophobic moieties of chrysophanol and hesperidin. Structural analyses confirmed the hypothesis that chrysophanol molecules were nearly embedded deeper into the interior of hydrophobic domains, and most of hesperidin molecules were incorporated into the exterior of the hydrophobic domains of OSβG-Agg due to the strength of these interactions, but they interacted in OSβG-Agg with a dense and compact structure rather than existing in isolation. The combined effects delayed their release and enhanced their bioaccessibility because of dynamic equilibrium between the favorable interactions and unfavorable structural erosion and relaxation of OSβG-Agg. Overall, OSβG-Agg is effective at codelivering hydrophobic phenolics for functional foods and pharmaceuticals.

Changes in chemical components and hepatoprotective effect of red Panax notoginseng processed by aspartic acid impregnation treatment

BACKGROUND

Red Panax notoginseng (RPN) is one of the major processed products of P. notoginseng (PN), with more effective biological activities. However, the traditional processing method of RPN has some disadvantages, such as low conversion rate of ginsenosides and long processing time.

RESULTS

In this work, we developed a green, safe, and efficient approach for RPN processing by aspartic acid impregnation pretreatment. Our results showed that the optimized temperature, steaming time, and concentration of aspartic acid were 120 °C, 1 h, and 3% respectively. The original ginsenosides in PN treated by aspartic acid (Asp-PN) were completely converted to rare saponins at 120 °C within just 1 h. The concentration of the rare ginsenosides in Asp-PN was two times higher than that in untreated RPN. In addition, we examined the protective effect of RPN and Asp-PN on acetaminophen-induced liver injury in a mouse model. The results showed that Asp-PN has significantly more potent hepatoprotective action than the RPN. The hepatoprotection of Asp-PN in acetaminophen-induced hepatotoxicity may be due to its anti-oxidative stress, anti-apoptotic, and anti-inflammatory activities.

CONCLUSION

These results indicated that aspartic acid impregnation pretreatment may provide an effective method to shorten the steaming time, improve the conversion rate of ginsenosides, and enhance hepatoprotective activity of RPN. © 2024 Society of Chemical Industry.

Wheat gliadin hydrolysates based nano-micelles for hydrophobic naringin: Structure characterization, interaction, and in vivo digestion

In this study, enzymatic hydrolysis was used to fabricate wheat gliadin hydrolysates (WGHs) for the encapsulation and protection of naringin. The exposure of hydrophilic amino acids decreased the critical micelle concentration (from 0.53 ± 0.02 mg/mL to 0.35 ± 0.03 mg/mL) and improved solubility, which provided amphiphilic conditions for the delivery of naringin. The hydrolysates with a degree of hydrolysis (DH) of 9 % had the strongest binding affinity with naringin, and exhibited the smallest particle size (113.7 ± 1.1 nm) and the highest encapsulation rate (83.2 ± 1.3 %). The storage, heat and photochemical stability of naringin were improved via the encapsulation of micelles. Furthermore, the micelles made up of hydrolysates with a DH of 12 % significantly enhanced the bioavailability of naringin (from 19.4 ± 4.3 % to 46.8 ± 1.4 %). Our experiment provides theoretical support for the utilization of delivery systems based on water-insoluble proteins.

Manipulation of Bowl-Shaped Nanoparticles Self-Assembled from a Bipyridine Pendant Containing Homopolymer

The morphological control and transformation of soft nanomaterials are critical for their physical and chemical properties, which can be achieved by dynamically regulating the hydrophilicity of amphiphilic polymers during self-assembly. Herein, an amphiphilic homopolymer poly(N-(2,2'-bipyridine)-4-acrylamide) (PBPyAA) with bipyridine pendants is synthesized, and the effect of various parameters including initial concentration, temperature, pH, and metal ion coordination on the self-assembly behavior and morphology of the assemblies is investigated. Upon changing the initial concentration of PBPyAA, bowl-shaped nanoparticles (BNPs) with precisely controlled diameter, opening size, and thickness are obtained. With the decrease of pH of the solution, the negatively charged surface of BNPs transforms to a positively charged state. Furthermore, the addition of divalent metal ions (Co2+, Mn2+, and Zn2+) induces the transformation of BNPs to vesicles and giant vesicles. The effect of the above factors on the morphology of the assemblies is essential to change the hydrophilicity of PBPyAA dynamically, leading to variation of the local viscosity during self-assembly. Overall, manipulation of the structural parameters of BNPs and transformation of BNPs to vesicles are achieved, providing fresh insights for the precise control of the morphologies of soft nanomaterials.

Photoacid-macroion assemblies: how photo-excitation switches the size of nano-objects

Electrostatic self-assembly of photoacids with oppositely charged macroions yields supramolecular nano-objects in aqueous solutions, whose size is controlled through light irradiation. Nano-assemblies are formed due to electrostatic attractions and mutual hydrogen bonding of the photoacids. Irradiation with UV light leads to the deprotonation of the photoacid and, consequently, a change in particle size. Overall, the hydrodynamic radii of the well-defined photoacid-macroion nano-objects lie between 130 and 370 nm. For a set of photoacids, we determine the acidity constants in the ground and excited state, discuss the sizes of photoacid-macroion nano-objects (by dynamic and static light scattering), their composition and the particle shapes (by small-angle neutron scattering), and relate their charge characteristics to size, structure and shape. We investigate the association thermodynamics and relate nanoscale structures to thermodynamics and, in turn, thermodynamics to molecular features, particularly the ionization energy of the photoacid hydroxyl group proton. Structure-directing effects completely differ from those for previously investigated systems, with hydrogen bonding and entropic effects playing a major role herein. This combined approach allows developing a comprehensive understanding of assembly formation and photo-response, anchored in molecular parameters (pKa, ionization energy, substituent group location), charge characteristics, and the association enthalpy and entropy. This fundamental understanding again paves the way for tailoring application solutions with novel photoresponsive materials.

Enhancing the thermostability and catalytic activity of Bacillus subtilis chitosanase by saturation mutagenesis of Lys242

Catalysis activity and thermostability are some of the fundamental characteristic of enzymes, which are of great significance to their industrial applications. Bacillus subtilis chitosanase BsCsn46A is a kind of enzyme with good catalytic activity and stability, which can hydrolyze chitosan to produce chitobiose and chitotriose. In order to further improve the catalytic activity and stability of BsCsn46A, saturation mutagenesis of the C-terminal K242 of BsCsn46A was performed. The results showed that the six mutants (K242A, K242D, K242E, K242F, K242P, and K242T) showed increased catalytic activity on chitosan. The catalytic activity of K242P increased from 12971 ± 597 U mg-1 of wild type to 17820 ± 344 U mg-1 , and the thermostability of K242P increased by 2.27%. In order to elucidate the reason for the change of enzymatic properties, hydrogen network, molecular docking, and molecular dynamics simulation were carried out. The hydrogen network results showed that all the mutants lose their interaction with Asp6 at 242 site, thereby increasing the flexibility of Glu19 at the junction sites of α1 and loop1. Molecular dynamics results showed that the RMSD of K242P was lower at both 313 and 323 K than that of other mutants, which supported that K242P had better thermostability. The catalytic activity of mutant K242P reached 17820.27 U mg-1 , the highest level reported so far, which could be a robust candidate for the industrial application of chitooligosaccharide (COS) production.

Mechanism underlying joint loading and controlled release of β-carotene and curcumin by octenylsuccinated Gastrodia elata starch aggregates

This study aimed to fabricate a novel codelivery system to simultaneously load β-carotene and curcumin in a controlled and synergistic manner. We hypothesized that the aggregates of octenylsuccinated Gastrodia elata starch (OSGES) could efficiently load and control the release of β-carotene and curcumin in combination. Mechanisms underlying the self-assembly of OSGES, coloading, and corelease of β-carotene and curcumin by relevant aggregates were studied. The OSGES could form aggregates with a size of 120.2 nm containing hydrophobic domains surrounded by hydrophilic domains. For coloading, the increased solubilities were attributed to favorable interactions between β-carotene and curcumin as well as interactions with octenyl and starch moieties via hydrophobic and hydrogen-bond interactions, respectively. The β-carotene and curcumin molecules occupied the interior and periphery of hydrophobic domains of OSGES aggregates, respectively, and they did not exist in isolation but interacted with each other. The β-carotene and curcumin combination-loaded OSGES aggregates with a size of 310.5 nm presented a more compact structure than β-carotene-only and curcumin-only loaded OSGES aggregates with sizes of 463.5 and 202.9 nm respectively, suggesting that a transition from a loose cluster to a compact cluster was accompanied by coloading. During in vitro digestion, the joint effect of β-carotene and curcumin prolonged their release and increased their bioaccessibility due to competition between favorable hydrophobic and hydrogen-bond interactions and the unfavorable structure erosion and relaxation of the loaded aggregates. Therefore, OSGES aggregates were designed for the codelivery of β-carotene and curcumin, indicating their potential to be applied in functional foods and dietary supplements.

Novel self-assembly nano OSA starch micelles controlled by protonation in aqueous media

A new micellization method was applied to produce the nano octenyl succinic anhydride (OSA) modified starch micelles with controllable size. The underlying mechanism was explored by using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), zeta-potential, surface tension, fluorescence spectra and transmission electron microscope (TEM). Due to the new starch modification method, the electrostatic repulsion between the deprotonation carboxyl groups prevented the aggregation of starch chains. With the progress of protonation, the weaken electrostatic repulsion and enhanced hydrophobic interaction driven the self-assembly of micelles. The size of micelles increased gradually with the increase of the protonation degree (PD) and concentration of OSA starch. However, a V-shaped trends were observed in the size as the increase of substitution of degree (DS). Curcuma loading test indicated that micelles had good encapsulated capability and the maximum value was 52.2 μg/mg. The understanding of the self-assembly behavior of OSA starch micelles can facilitate and improve the starch-based carrier designs used to synthesis complex and smart micelle delivery system with good biocompatibility.

High-temperature behavior of hyperthermostable Thermotoga maritima xylanase XYN10B after designed and evolved mutations

A hyperthermostable xylanase XYN10B from Thermotoga maritima (PDB code 1VBR, GenBank accession number KR078269) was subjected to site-directed and error-prone PCR mutagenesis. From the selected five mutants, the two site-directed mutants (F806H and F806V) showed a 3.3-3.5-fold improved enzyme half-life at 100 °C. The mutant XYNA generated by error-prone PCR showed slightly improved stability at 100 °C and a lower K_m. In XYNB and XYNC, the additional mutations over XYNA decreased the thermostability and temperature optimum, while elevating the K_m. In XYNC, two large side-chains were introduced into the protein's interior. Micro-differential scanning calorimetry (DSC) showed that the melting temperature (T_m) dropped in XYNB and XYNC from 104.9 °C to 93.7 °C and 78.6 °C, respectively. The detrimental mutations showed that extremely thermostable enzymes can tolerate quite radical mutations in the protein's interior and still retain high thermostability. The analysis of mutations (F806H and F806V) in a hydrophobic area lining the substrate-binding region indicated that active site hydrophobicity is important for high activity at extreme temperatures. Although polar His at 806 provided higher stability, the hydrophobic Phe at 806 provided higher activity than His. This study generates an understanding of how extreme thermostability and high activity are formed in GH10 xylanases. KEY POINTS: • Characterization and molecular dynamics simulations of TmXYN10B and its mutants • Explanation of structural stability of GH10 xylanase.

Homopolymer nanobowls with controlled size and denting degree

Homopolymer nanobowls hold promising potential applications in many fields because of their designability, large specific surface area and high packing density. However, it is still challenging to prepare nanobowls with...

Effect of temperature and pH on the encapsulation and release of β-carotene from octenylsuccinated oat β-glucan micelles

Effect and working mechanism of temperature and pH on encapsulation and release of β-carotene from octenylsuccinated-oat-β-glucan-micelles (OSβG-Ms) were investigated. The stability and solubility of β-carotene, and changes in surface hydrophilicity, core hydrophobicity, and size of β-carotene-loaded-OSβG-Ms were determined. When exposed to temperature (25-45 °C) and pH (4.5-8.5), β-carotene solubilization changed in parabolic manners. Size and absolute zeta-potential of β-carotene-loaded-OSβG-Ms decreased with temperature, while they gave parabolic changing patterns with pH. Those results were ascribed to their hydrophilicity, hydrophobicity, and core/shell compactness via regulating molecule mobility, orientation, and interactions by temperature/pH. The higher temperature concluded with higher β-carotene release, while a U-shaped release profile was observed with pH. Besides its diffusion, erosion-induced shrinking and collapsing of OSβG-Ms favored β-carotene release at pH 1.2-4.5, which was replaced by swelling-induced structural-relaxation at pH 6.8-8.5. The results were favourable in controlling the behavior of β-carotene-loaded-OSβG-Ms by selectively applying environmental parameters.