Hydrophobic Aggregation Research Articles

Flexible and Zwitterionic Fluorinated Hydrogel Scaffold with High Fluorine Content for Noninvasive 19 F Magnetic Resonance Imaging under Ultrahigh Scanning Resolution.

The imaging of hydrogel scaffolds by 19 F magnetic resonance imaging (MRI) represents an attractive tool for straightforward and noninvasive monitoring of their morphology and in vivo fate. However, their further applications are significantly limited by a dilemma of insufficient signal resolution with low 19 F content, and/or hydrophobic aggregation of fluorine moieties-induced signal attenuation with high 19 F content. Herein, a novel label-free fluorinated hydrogel (PFCB) is fabricated with high fluorine content to realize noninvasive monitoring through 19 F MRI under ultrahigh scanning resolution (1 mm of scanning thickness). The integration of a zwitterionic unit into each fluorine moiety completely overcame the hydrophobic aggregation-induced signal attenuation, manifesting as high 19 F content and imaging performance. Importantly, 3D reconstruction of the PFCB hydrogel in vivo can be facilely and accurately performed with background free signals, providing detailed biological information of the implanted hydrogel. Additionally, PFCB hydrogel showed adjustable and high mechanical performance, and exhibited minimum foreign body reaction after implantation. As a proof of concept, PFCB hydrogel could be further applied as gel electrodes and wireless flexible sensors for healthcare monitoring. Overall, such label-free fluorinated PFCB hydrogel is an ideal flexible scaffold for eventual clinical applications integrating 19 F MRI-guided unequivocally 3D reconstruction and healthcare monitoring.

Multiple Pickering emulsions fabricated by a single block copolymer amphiphile in one-step

The mixture of emulsifiers with opposite amphiphilicity was often necessary in generating multiple emulsions, whereas multiple emulsions might be generated by a single-component copolymer amphiphile. In this work, the emulsification of amphiphilic block copolymers poly (lauryl methacrylate)-b-poly (N-(2-methacryloylxyethyl) pyrrolidone) (PLMAm-b-PNMPn) in the water/dodecane systems was systematically studied by the confocal laser scanning microscopy and dynamic light scattering techniques. Interestingly, multiple emulsions instead of single emulsions were generated by employing single-component block copolymer amphiphiles PLMAm-b-PNMPn as emulsifiers under certain conditions. In specifically, the formation of multiple emulsions was highly depended on the molar ratio (rPNMP/PLMA = n/m) between the PNMP and PLMA segments regardless of the molecular weight of block copolymers. Through introducing an aggregation-induced emission amphiphile poly (N-(2-methacryloyloxyethyl) pyrrolidone)-b-poly (lauryl methacrylate-co-1-ethenyl-4-(1,2,2-triphenylethenyl) benzene) (PNMP35-b-P(LMA42-co-TPE16) into emulsifiers, the interfacial characters of multiple emulsions were also clarified. The complex emulsification of PLMAm-b-PNMPn was explained by a concordant manner based on the in-situ formed emulsifier mixture composed of PLMAm-b-PNMPn molecules and micelles, which were confirmed by the quantitative fluorescent analysis. It was found out that the preferred continuous phase of emulsions was mainly determined by the hydrophilicity of PLMAm-b-PNMPn molecules. However, the agglomeration of hydrophobic aggregates on the interfacial layer might inverse the amphiphilicity of mixed emulsifiers, and thereby resulting in the formation of multiple emulsions.

Super strong gelatin/cellulose nanofiber hybrid hydrogels without covalent cross-linking for strain sensor and supercapacitor

Natural polymer hydrogels are considered to be excellent candidates for eco-friendly flexible devices. However, the defects of low strength and poor toughness result in their being easily damaged. Here, strong gelatin-based hydrogels enhanced by hydrophobic aggregation were prepared using salting-out treatment. Moreover, the cellulose nanofiber (CNF) with large aspect ratio further improved the mechanical strength relying on the intertwining effect. The optimized strong hybrid gelatin/CNF hydrogel achieved 0.73 MPa of breaking strength and 250% of elongation at break, 405 and 8.3 times that of the original hydrogel, respectively. Notably, the gelatin/CNF hydrogel exhibited satisfactory conductivity and excellent linear sensing behavior, allowing it to monitor human motions accurately. Besides, this robust gelatin-based hydrogel could be used as supercapacitor electrolyte and showed desirable rate capability and good cycling stability. This work implies a bright future for the application of gelatin-based hydrogel in the field of environmentally friendly energy storage devices and sensors.

Polyelectrolyte-Surfactant Complexes As a Formulation Tool for Drug Delivery.

Aqueous polyelectrolyte-surfactant complexes (PESCs) are very rich with respect to their properties and the structures formed by them. By design they normally contain hydrophobic micellar surfactant aggregates complexed by long polyelectrolyte chains, thereby combining the formation of small hydrophobic domains given by the surfactant with large-scale structuring due to the presence of the polyelectrolyte chain. In addition, they contain highly polar regions of surfactant head groups in contact with polyelectrolyte, forming a shell around the micellar aggregates, which often also possesses a certain hydrophobic character. Accordingly, the ability for solubilization of water-insoluble compounds of different sorts is particularly versatile in PESCs. Their solubilization sites with very different polarities and hydrophobic characters make them very flexible in adapting to the requirements of a given drug molecule. This renders them attractive for potential applications in drug delivery. In addition, modification of the rheological properties via self-assembly and network formation can be very important in PESC applications. In the following, we discuss the structures of PESCs and their properties, with a focus on the solubilization properties. Subsequently, examples are described where PESCs have been employed in the context of drug solubilization and delivery. These comprise examples with individual aggregates, cross-linked hydrogels, and ones taking advantage of the high solubilization capacity of microemulsions.

Eco-friendly utilization of waste oil for preparing coal water slurry: Additive suitability and dispersion mechanism

Industrial waste oil is a type of hazardous waste with a high calorific value. Mixing it with coal for combustion or gasification is an environmentally friendly and efficient way of recycling. Here, the suitability of additives for waste oil-coal slurry and waste oil-coal-water slurry was investigated experimentally, and their dispersion and stabilization mechanisms were also explored. The results show that water-soluble additives such as Tween 80, MF and xanthan gum form reverse micelles in the oil phase of the waste oil-coal slurry, which results in agglomeration and failure to function as intended. Of the different additives, the viscosity reduction effect of Tween 80 in the waste oil-coal-water slurry was best. Further, the comprehensive performance of the waste oil-coal-water slurry, including slurry ability, stability and fluidity, was found to be best at a water content of 10% and a Tween 80 content of 5%. Under these conditions, a solid concentration of 45.75% results in a continuously flowing slurry with good dispersion and stability. The interface properties of coal particles, oil, and water were studied by means of Fourier transform infrared spectroscopy (FTIR) and contact angle measurements, and a dispersion and stabilization mechanism for the waste oil-coal-water slurry was proposed. In this mechanism, some of the coal particles enter the reverse micelle, causing the water core to become a hydration film on the surface of the particles, which blocks hydrophobic particle aggregation. In addition, the surfaces of some coal particles are rapidly coated with an oily film, which also inhibits particle aggregation.

Enhancing flotation separation of fine copper oxide from silica by microbubble assisted hydrophobic aggregation

One of the main challenges facing the flotation of base metal oxide minerals is their fine sizes of particles as a result of fine grinding to achieve a desired degree of liberation for low-grade and finely disseminated complex ores. This study aims at studying hydrophobic aggregation and in situ gas nucleation of fine copper oxides with sodium dodecyl sulfate (SDS) as a selective collector to enhance CuO recovery. Experimental results by in situ and real time particle size measurement using focused beam reflectance measurement (FBRM) coupled with particle vision measurement (PVM) showed an enhanced aggregation of fine CuO by SDS adsorption. Particle aggregation assisted by gas nuclei which were generated in situ on CuO by high intensity agitation (HIA) was visualized by total internal reflection fluorescence microscopy (TIRFM). It is the enhanced aggregation with nanobubbles as bridges that improved its recovery from fine silica. Coupled with the calculation using the extended DLVO theory, contact angle and zeta potential of fine particles were measured to understand the critical role of hydrophobic forces in aggregation of fine CuO particles. The copper ions dissolved from the fine copper oxide were found to inadvertently activate fine silica flotation which could be effectively depressed by ethylene diamine tetraacetic acid (EDTA). A combination of SDS with EDTA was proposed and demonstrated to achieve selective recovery of fine copper oxide from fine silica gangue. The results from this study provide directions for enhancing copper recovery from low grade and finely disseminated copper oxidize ores, in particular from tenorite ores.

Molecular Mechanism of Hydrotropic Properties of GTP and ATP.

Hydrotropes are small amphiphilic compounds that increase the aqueous solubility of hydrophobic molecules. Recent evidence suggests that adenosine triphosphate (ATP), which is the primary energy carrier in cells, also assumes hydrotropic properties to prevent the aggregation of hydrophobic proteins, but the mechanism of hydrotropy is unknown. Here, we compare the hydrotropic behavior of all four biological nucleoside triphosphates (NTPs) using molecular dynamics (MD) simulations. We launch all atom MD simulations of aqueous solutions of NTPs [ATP, guanosine triphosphate (GTP), cytidine triphosphate (CTP), and uridine triphosphate (UTP)] with pyrene, which acts both as a model hydrophobic compound and as a spectroscopic reporter for aggregation. GTP prevents pyrene aggregation effectively. Dissolution is not achieved in the presence of CTP and UTP. The higher stability of the base stacking in guanine is responsible for the higher hydrotropic efficiency of GTP. Consistent with the simulations, spectroscopic measurements also suggest that the hydrotropic activity of GTP is higher than ATP. Stacking of aromatic pyrene with the aromatic base of NTPs is a characteristic feature of this hydrotropic property. Both ATP and GTP also dissolve clusters of di- and tripeptides containing tryptophan but with equal potency. Importantly, the presence of aromatic amino acids is a necessary condition for the hydrotropic potency of ATP and GTP. Our results can have broad implications for hydrotrope design in the pharmaceutical industry, as well as the possibility of cells employing GTP as a hydrotrope to regulate the hydrophobic protein aggregation in membrane-less biological condensates.

OSA-linear dextrin enhances the compactness of pea protein isolate nanoparticles: Increase of high internal phase emulsions stability

The pea protein isolate nanoparticles/octenyl succinic anhydride linear dextrin (PPINs/OSA-LD) composite particles were fabricated by heating at acidic condition. Heating treatment not only made OSA-LD dissolve, but also promoted the hydrophobic interactions between PPINs and OSA-LD. With the increase of OSA-LD content, the average diameter of composite particles decreased due to the avoidance of hydrophobic aggregation between PPINs during heating, and the composite particles became more compact and regular. The high internal phase emulsions (HIPEs) stabilized by composite particles exhibited smaller droplet size, higher viscosity and modulus attributing to the formation of denser interfacial layer. The results of low field nuclear magnetic resonance proved that the HIPEs stabilized by composite particles showed more uniform distribution of water and oil. This work provided a facile method to fabricate composite particles, which had excellent capacity to stabilize the HIPEs.

High strength, anti‐freezing, and conductive poly(vinyl alcohol)/urea ionic hydrogels as soft sensor

AbstractHydrogel‐based sensors with excellent flexibility and stretchability have received extensive attention. However, fabricating anti‐freezing, high‐strength, and conductive hydrogel‐based sensors remains a significant challenge. A stretchable sensor with high strength and anti‐freezing herein is constructed using poly(vinyl alcohol)/urea (PVA/urea) ionic hydrogels. The PVA/urea ionic hydrogels were prepared by a simple strategy of soaking the freeze–thawed PVA hydrogels in sodium citrate (Na3Cit) water/urea aqueous solutions. The presence of Na3Cit in the hydrogel produces hydrophobic aggregation, endowing the PVA/urea ionic hydrogel with high mechanical properties (~1.51 MPa) and makes the hydrogel have high strain gauge factors (GF = 1.94). The synergistic effect of Na3Cit and urea endows the PVA/urea ionic hydrogel with anti‐freezing properties (~−20°C). The obtained sensors have excellent stability (100 cycles at ε = 85%) and could detect various human activities even at −20°C. More importantly, joint motion can be monitored wirelessly via Bluetooth at −20°C. This work provides a feasible method to construct anti‐freezing, high‐strength, and conductive hydrogel. It paves the way for versatile applications in human‐motion detection, intelligence device, and biomimetic skin.

Dual improvement in curcumin encapsulation efficiency and lyophilized complex dispersibility through ultrasound regulation of curcumin–protein assembly

Ultrasound has a recognized ability to modulate the structure and function of proteins. Discovering the influential mechanism of ultrasound on the intramolecular interactions of egg-white protein isolate–curcumin (EPI–Cur) nanoparticles and their intermolecular interaction during freeze drying and redispersion is meaningful. In this study, under the extension of pre-sonication time, the protein solubility, surface hydrophobicity, and curcumin encapsulation rate showed an increasing trend, reaching the highest value at 12 min of treatment. However, the values decreased under the followed extension of ultrasound time. After freeze drying and redispersion were applied, the EPI–Cur sample under 12 min of ultrasound treatment exhibited minimal aggregation degree and loss of curcumin. The retention and loading rates of curcumin in the lyophilized powder reached 96 % and 33.60 mg/g EPI, respectively. However, under excessive ultrasound of >12 min, scanning electron microscopy showed distinct blocky aggregates. Overexposure of the hydrophobic region of the protein triggered protein-mediated hydrophobic aggregation after freeze drying. X-ray diffraction patterns showed the highest crystallinity, indicating that the free curcumin-mediated hydrophobic aggregation during freeze drying was enhanced by the concentration effect and intensified the formation of larger aggregates. This work has practical significance for developing the delivery of hydrophobic active substances. It provides theoretical value for the dynamic dispersity change in protein-hydrophobic active substances during freeze drying and redissolving.

Physicochemical properties and digestibility of thermally induced ovalbumin–oil emulsion gels: Effect of interfacial film type and oil droplets size

To investigate the effect of oil droplets surface film type and droplets size on the physicochemical properties and digestibility of thermally induced ovalbumin–oil emulsion gels, Tween 80 and ovalbumin were selected as individual emulsifiers for the emulsification of sunflower oil at different homogenization speeds (6000, 8000, and 10000 rpm), and the formed emulsions were mixed with ovalbumin matrix solution and then heated to form heat-induced ovalbumin emulsion gels (OEG). The OEG with ovalbumin as emulsifier had higher hardness, water holding capacity (WHC), and surface hydrophobicity, and lower digestibility, spin−spin relaxation time ( T 2 ) and free sulfhydryl content than those of the OEG with Tween 80 as the emulsifier ( p < 0.05). As the oil droplets size decreased, the hardness increased, WHC increased, the amide A band shifted to lower wavenumbers, digestibility decreased, T 2 decreased, free sulfhydryl content decreased, and surface hydrophobicity increased for both OEG ( p < 0.05). These results collectively indicated that the physicochemical properties of the OEG are influenced by the property of the oil interfacial film and the size of the oil droplets. The oil droplets surrounded by the interfacial protein film improved the performance of the OEG greatly, and the proteins within its OEG formed a dense gel network structure through hydrophobic aggregation, disulfide bond crosslinking, and hydrogen bonding. The oil droplets with smaller sizes favored the enhancement in the physicochemical properties of the OEG. Changes in the size of oil droplets and the type of film wrapped around them regulated the digestibility of the OEG. • The OEG-O with the small size of oil droplets had the highest hardness. • Small oil droplets filled better in the gel network to improve the hardness of OEG. • IPF-encapsulated oil droplets as active filler to increase the hardness of OEG. • Effect of filler on hardness depends on the heat stability of its interfacial layer. • Changes in oil droplet size and interfacial layer type regulated OEG digestibility.

Characterization of the Conformations of Amyloid Beta 42 in Solution That May Mediate Its Initial Hydrophobic Aggregation.

Intrinsically disordered peptides, such as amyloid β42 (Aβ42), lack a well-defined structure in solution. Aβ42 can undergo abnormal aggregation and amyloidogenesis in the brain, forming fibrillar plaques, a hallmark of Alzheimer's disease. The insoluble fibrillar forms of Aβ42 exhibit well-defined, cross β-sheet structures at the molecular level and are less toxic than the soluble, intermediate disordered oligomeric forms. However, the mechanism of initial interaction of monomers and subsequent oligomerization is not well understood. The structural disorder of Aβ42 adds to the challenges of determining the structural properties of its monomers, making it difficult to understand the underlying molecular mechanism of pathogenic aggregation. Certain regions of Aβ42 are known to exhibit helical propensity in different physiological conditions. NMR spectroscopy has shown that the Aβ42 monomer at lower pH can adopt an α-helical conformation and as the pH is increased, the peptide switches to β-sheet conformation and aggregation occurs. CD spectroscopy studies of aggregation have shown the presence of an initial spike in the amount of α-helical content at the start of aggregation. Such an increase in α-helical content suggests a mechanism wherein the peptide can expose critical non-polar residues for interaction, leading to hydrophobic aggregation with other interacting peptides. We have used molecular dynamics simulations to characterize in detail the conformational landscape of monomeric Aβ42 in solution to identify molecular properties that may mediate the early stages of oligomerization. We hypothesized that conformations with α-helical structure have a higher probability of initiating aggregation because they increase the hydrophobicity of the peptide. Although random coil conformations were found to be the most dominant, as expected, α-helical conformations are thermodynamically accessible, more so than β-sheet conformations. Importantly, for the first time α-helical conformations are observed to increase the exposure of aromatic and hydrophobic residues to the aqueous solvent, favoring their hydrophobically driven interaction with other monomers to initiate aggregation. These findings constitute a first step toward characterizing the mechanism of formation of disordered, low-order oligomers of Aβ42.

Coacervate-Derived Hydrogel with Effective Water Repulsion and Robust Underwater Bioadhesion Promotes Wound Healing.

Achieving robust underwater adhesion by bioadhesives remains a challenge due to interfacial water. Herein a coacervate-to-hydrogel strategy to enhance interfacial water repulsion and bulk adhesion of bioadhesives is reported. The polyethyleneimine/thioctic acid (PEI/TA) coacervate is deposited onto underwater substrates, which can effectively repel interfacial water and completely spread into substrate surface irregularities due to its liquid and water-immiscible nature. The physical interactions between coacervate and substrate can further enhance interfacial adhesion. Furthermore, driven by the spontaneous hydrophobic aggregation of TA molecules and strong electrostatic interaction between PEI and TA, the coacervate can turn into a hydrogel in situ within minutes without additional stimuli to develop enhanced matrix cohesion and robust bulk adhesion on diverse underwater substrates. Molecular dynamics simulations further reveal atomistic details of the formation and wet adhesion of the PEI/TA coacervate via multimode physical interactions. Lastly, it is demonstrated that the PEI/TA coacervate-derived hydrogel can effectively repel blood and therefore efficiently deliver the carried growth factors at wound sites, thereby enhancing wound healing in an animal model. The advantages of the PEI/TA coacervate-derived hydrogel including body fluid-immiscibility, strong underwater adhesion, adaptability to fit irregular target sites, and excellent biocompatibility make it a promising bioadhesive for diverse biomedical applications.

Strengthening poly(2-hydroxyethyl methacrylate) hydrogels using biochars and hydrophobic aggregations

ABSTRACT As the first version of synthetic hydrogel, poly(2-hydroxyethyl methacrylate) hydrogels have found broad applications. However, their poor mechanical performances have been long-standing hurdles for practical deployments. Herein, we report on strengthening the poly(2-hydroxyethyl methacrylate) hydrogels with biochar nanoparticles and hydrophobic aggregations, which are induced by solvent exchange and reinforced by freeze-thaw. Both the vast anchoring points on the multifunctional surfaces of the biochar nanoparticles and the aggregates formed between poly(2-hydroxyethyl methacrylate) chains engender strong and dissipative physical crosslinks. The resulting hydrogels exhibit marked mechanical properties, encompassing high stretchability ~7, high fracture toughness ~1360 J m−2, high elastic modulus ~180 kPa, low friction coefficient ~0.2, self-recovery, and non-swellability. Furthermore, we demonstrate the versatility of the proposed strategy by using water/ionic liquid binary solvent as the solvent system, Laponite as the nano-reinforcement, and dry-anneal as the hydrophobic aggregation enhancer to synthesize mechanically robust hydrogels. Poly(2-hydroxyethyl methacrylate) hydrogels of superior mechanical properties are expected to enable previously inaccessible applications in biomedicine and engineering.

Water-driven noninvasively detachable wet tissue adhesives for wound closure

Tissue adhesive with on-demand detachment feature is critically important since it can minimize hurt to patient when it is stripped away. Herein, a water-driven noninvasively detachable wet tissue adhesive hydrogel (w-TAgel) was produced by UV-initiated radical copolymerization of N-isopropylacrylamide (NIPAM), acrylamide (AAm), gelatin methacrylate (GelMA), and urushiol. As a w-TAgel, its robust and tough mechanical property makes it suitable for dynamic wound tissue. The polyurushiol segments of it are crucial to the formation of tough adhesion interface with various wet tissues, while polyNIPAM units play an indispensable role in on-demand detachment via thermo-responsive swelling behavior because the hydrophobic aggregation among isopropyl groups is destroyed upon water treatment with temperature of 25 ​°C or less. Additionally, it exhibits multiple merits including good hemocompatibility, cytocompatibility as well as pro-coagulant activity and hemostasis. Therefore, our w-TAgel with strong adhesion and facile detachment is an advanced prospective dressing for wound closure and rapid hemostasis. The wet tissue adhesion and water-driven detachable mechanism may shed new light on the development of on-demand noninvasively detachable wet tissue adhesives.

Biomimetic Gradient Hydrogel Actuators with Ultrafast Thermo-Responsiveness and High Strength.

Most current hydrogel actuators suffer from either poor mechanical properties or limited responsiveness. Also, the widely used thermo-responsive poly-(N-isopropylacrylamide) (PNIPAM) homopolymer hydrogels have a slow response rate. Thus, it remains a challenge to fabricate thermo-responsive hydrogel actuators with both excellent mechanical and responsive properties. Herein, ultrafast thermo-responsive VSNPs-P(NIPAM-co-AA) hydrogels containing multivalent vinyl functionalized silica nanoparticles (VSNPs) are fabricated. The ultrafast thermo-responsiveness is due to the mobile polymer chains grafted from the surfaces of the VSNPs, which can facilitate hydrophobic aggregation, inducing the phase transition and generating water transport channels for quick water expulsion. In addition, the copolymerization of NIPAM with acrylic acid (AA) decreases the transition temperature of the thermo-responsive PNIPAM-based hydrogels, contributing to ultrafast thermo-responsive shrinking behavior with a large volume change of as high as 72.5%. Moreover, inspired by nature, intelligent hydrogel actuators with gradient structure can be facilely prepared through self-healing between the ultrafast thermo-responsive VSNPs-P(NIPAM-co-AA) hydrogel layers and high-strength VSNPs-PAA-Fe3+ multibond network (MBN) hydrogel layers. The obtained well-integrated gradient hydrogel actuators show ultrafast thermo-responsive performance within only 9 s in 60 °C water, as well as high strength, and can be used for more practical applications as intelligent soft actuators or artificial robots.

Shear hydrophobic aggregation of fine quartz particles in the presence of dodecylamine

Shear hydrophobic aggregation of fine quartz particles in the presence of dodecylamine

Investigation of an Uncommon Artifact during Reducing Capillary Electrophoresis-Sodium Dodecyl Sulfate Analysis of a Monoclonal Antibody with Dynamic Light Scattering and Reversed Phase High-Performance Liquid Chromatography.

In reducing capillary electrophoresis sodium dodecyl sulfate (CE-SDS) analysis of a monoclonal antibody (mAb-1), the peak area ratio of heavy chain (HC) to light chain (LC) was out of balance, while multiple artifact peaks were observed following the migration of HC. The main purposes of this study were to describe the techniques utilized to eliminate this artifact and clarify the root cause for this interesting phenomenon. We optimized the CE-SDS analysis of mAb-1 by a vairety of techniques including changing the concentration of protein or replacing SDS with a more hydrophobic surfactant (i.e., sodium hexadecyl sulfate (SHS) or sodium tetradecyl sulfate (STS) instead of SDS) in sample and/or the sieving gel buffer. Dynamic light scattering (DLS) and reversed phase high-performance liquid chromatography (RP-HPLC) were used to study the protein-surfactant complex. The artifact could be partially mitigated by reducing the protein concentration and replacing SDS with SHS or STS in the sample and/or the sieving gel buffer solutions. Due to replacing a more hydrophobic surfactant, the HC-surfactant complex formed was more resistant to dissociation, preventing additional hydrophobic HC-HC interaction and aggregation, thus eliminating the artifact problem. DLS and RP-HPLC are powerful supplementary techniques in characterizing the protein-surfactant complex, and hydrophobic surfactants such as SHS and STS could afford more normal electropherograms during the analysis of mAbs.

Ultrasound-induced changes in rheological behavior and hydrophobic microdomains of Lignosus rhinocerotis polysaccharide

Ultrasound is increasingly applied to modify the structures and physicochemical properties of polysaccharides. Hence, this work investigated the ultrasound-induced changes in the rheological behavior and hydrophobic microdomains of Lignosus rhinocerotis polysaccharide (LRP). With an increase in ultrasonic time, the apparent viscosity, storage modulus, loss modulus, and the final percentage recovery of LRP/water system increased to reach the maximum after 10 min treatment and then decreased. These results indicated that short-term (10 min) ultrasound could increase the strength of the network structure of LRP/water system, while longer-term ultrasound (30 and 60 min) weakened the network structure. The self-healing properties of LRP/water system was not affected by ultrasound treatment according to repeated strain and time sweep data. The critical aggregation concentration of the LRP/water system decreased from 2.5 to 1.8 mg/mL after 10 min ultrasound and the number of hydrophobic microdomains increased, suggesting that ultrasound promoted the hydrophobic aggregation of LRP.

Effects of Peroxyl Radicals on the Structural Characteristics and Fatty Acid Composition of High-Density Lipoprotein from Duck Egg Yolk

In this study, high-density lipoprotein (HDL) from duck egg yolk was subjected to oxidation with a system based on 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-derived peroxyl radicals. The effects of peroxyl radicals on the protein carbonyl, free sulfhydryl, secondary/tertiary structure, surface hydrophobicity, solubility, particle size distribution, zeta potential and fatty acid composition of HDL were investigated by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Fourier-transform infrared spectroscopy (FTIR), circular dichroism (CD), fluorescence spectroscopy, dynamic light scattering and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The results indicated that the content of protein carbonyl was significantly increased, that of free sulfhydryl was obviously reduced, and the ordered secondary structure was also decreased with increasing AAPH concentration. In addition, the surface hydrophobicity and solubility of HDL showed apparent increases due to the exposure of hydrophobic groups and aggregation of protein caused by oxidation. The fatty acid composition of HDL exhibited pronounced changes due to the disrupted protein–lipid interaction and lipid oxidation by AAPH-derived peroxyl radicals. These results may help to elucidate the molecular mechanism for the effect of lipid oxidation products on the oxidation of duck yolk proteins.