Interactions between bovine serum albumin and alginate: an evaluation of alginate as protein carrier

Effect of ultrasound on the characterization and peptidomics of foxtail millet bran protein hydrolysates

Protein hydrolysates have attracted much attention for their high biological activity and are a crucial product form for the utilization of foxtail millet bran by-products. In this study, changes in the structure, functionality, activity and peptide profile of foxtail millet bran protein hydrolysates (FMBPHs) at different ultrasound powers (0 - 600 W) were investigated. The results showed that ultrasound promoted the transformation of α-helix and β-sheet to random coils and β-turn, and the exposure of hydrophobic groups and sulfhydryl groups in FMBPHs. The average particle size of the samples decreased, and the absolute value of the ζ-potential increased significantly. Simultaneously, smaller porous particles and loose fragments appeared on the surface of FMBPHs when the ultrasonic power was increased to 450 W. Additionally, 450 W ultrasound treatment improved solubility, foaming properties, emulsifying properties, thermal stability of FMBPHs. The DPPH, ABTS and hydroxyl radical scavenging ability (IC50, 2.65, 1.06 and 3.02 mg/mL), Fe2+ chelating activity (IC50, 2.62 mg/mL), and reducing power of the samples were also enhanced. The peptidomics results demonstrated that ultrasonication increased the number of active peptides in the hydrolysate, and the relative abundance of 17 active peptides was obviously elevated at 450 W. Peptide map analysis showed that ultrasound-induced structural modifications affected the peptide profiles of Ubiquitin-like domain-containing protein, Cupin type-1 domain-containing protein, 40S ribosomal protein S19, and Oleosin 1, showing changes in the abundance of certain peptides, which may be related to changes in the characterization of FMBPHs.

Alginate binding enhances the structural stability and potentiates the lytic activity of bacteriophage endolysin's partially folded conformation

Polysaccharide polymers are increasingly being used as chaperon-like macromolecules in assisting protein folding of unfolded protein molecules. They interact with unfolded or partially folded proteins in a charge and conformation specific manner that results in the formation of stable protein-polysaccharide complexes. In most of the cases, the complex formation of protein-polysaccharide is driven via non-covalent interactions that have found to endorse the activity of proteins. T4L (18.7 kDa) and T7L (17 kDa) endolysins belong to the hydrolase and amidase class of peptidoglycan degrading enzymes. Both T4L and T7L exist in partially folded forms and are devoid of lytic activity at low pH conditions. In the current study, we assessed the binding of alginate with T4L and T7L at pH 7 and 3 using variety of biophysical and biochemical techniques. Spectroscopic studies revealed differential structural modulations of partially folded T4L and T7L upon their interaction with alginate. Further, the complex formation of alginate with partially folded T4L/T7L was confirmed by ITC and STEM. Additionally, the formed complexes of alginate with both T4L/T7L PF endolysins were found to be chemically and enzymatically stable. Moreover, such complexes were also marked with differential enhancement in their lytic activities at acidic pH conditions. This implied the potency of alginate as an excellent choice of matrix to preserve the structural and functional integrity of partially folded forms of T4L and T7L at highly acidic conditions.

Preparation of alginate/vermiculite composite functionalized with silanol group for controlled drug delivery: Effect of CaCl2 concentration, release kinetics, cytotoxicity, and antimicrobial activities

In this study, alginate/vermiculite (Alg/VMT) hydrogel with 3-aminopropyl triethoxysilane (Alg/VSN) and tetraethoxysilane (Alg/VS) synthesized with various concentrations of CaCl2 (10 %-15 %-20 % M) to extend the release of 6-Aminopenicillanic acid (AP). Composites characterized by XRD, FTIR and BET. The result of Alg/VS composite shows an excellent loading of 243.90 mg/g through AP intercalated in the VMT layer. The equilibrium and Kinetic studies indicated that AP adsorption on Alg/VS and Alg/VSN was heterogeneous with chemical interaction. The in-vitro release Alg/VS showed a rapid burst release of 14 % in the first half an hour and only 75 % of the drug remained in the composite. Whereas, the in-vitro release Alg/VSN showed substantially less burst release with the cumulative release of 9 % (in the first 0.5 h). In-vitro release kinetics in the presence of CaCl2 concentrations showed that maximum 19 % of AP released within 12 h. The kinetic release was followed by a controlled release pattern (Korsmeyer-Peppas model) with Fick's law mechanism. The composites behaved as barriers against cell growth and had better biocompatibility against standard strains of Pseudomonas aeruginosa and Methicillin-Resistant Staphylococcus. MTT assay results from per cent cell viability composites modified by silanol groups were 96 % the means samples were nontoxic. The types of newly synthesized composites were able to finely decrease cell toxicity and improve AP release in vitro.

Improvement of processable properties of plant-based high internal phase emulsions by mung bean protein isolate based on pH shift treatment

BACKGROUND

High internal phase emulsions (HIPEs) are unique emulsion systems that transform liquid oil into solid-like fats, thus avoiding the use of saturated fat and leading to a healthier and more sustainable food system for consumers. HIPEs with oil volume fraction (ϕ) of 75-85% were fabricated with mung bean protein isolate (MPI) under different pH shift treatments at 1.0% concentration through the one-step method. In the present study, we investigated the physical properties, microstructures, processing properties, storage stability and rheological properties of HIPEs.

RESULTS

The results suggested that the properties of MPI under different pH shift treatments were improved to different degrees, stabilizing HIPEs (ϕ = 75-85%) with various processability to meet food processing needs. Under alkali shift treatment conditions, the particle size of MPI was significantly reduced with better solubility. Moreover, the exposure of hydrophobic groups increased the surface hydrophobicity of MPI, awarding MPI better emulsifying properties, which could stabilize the HIPEs with higher oil phase fraction. In addition, the MPI under pH 12 shift treatment (MPI-12) had the best oil-carrying ability to form the stable HIPEs with oil volume fraction (ϕ) up to 85%, which was the highest oil phase in preparing the HIPEs using plant protein solely at a low concentration under neutral conditions.

CONCLUSION

A series of stable HIPEs with different processing properties was simply and feasibly fabricated and these are of great potential in applying edible HIPEs. © 2024 Society of Chemical Industry.

Correlative Effects on Nanoplastic Aggregation in Model Extracellular Biofilm Substances Investigated with Fluorescence Correlation Spectroscopy

Recent studies show that biofilm substances in contact with nanoplastics play an important role in the aggregation and sedimentation of nanoplastics. Consequences of these processes are changes in biofilm formation and stability and changes in the transport and fate of pollutants in the environment. Having a deeper understanding of the nanoplastics-biofilm interaction would help to evaluate the risks posed by uncontrolled nanoplastic pollution. These interactions are impacted by environmental changes due to climate change, such as, e.g., the acidification of surface waters. We apply fluorescence correlation spectroscopy (FCS) to investigate the pH-dependent aggregation tendency of non-functionalized polystyrene (PS) nanoparticles (NPs) due to intermolecular forces with model extracellular biofilm substances. Our biofilm model consists of bovine serum albumin (BSA), which serves as a representative for globular proteins, and the polysaccharide alginate, which is a main component in many biofilms, in solutions containing Na+ with an ionic strength being realistic for fresh-water conditions. Biomolecule concentrations ranging from 0.5 g/L up to at maximum 21 g/L are considered. We use non-functionalized PS NPs as representative for mostly negatively charged nanoplastics. BSA promotes NP aggregation through adsorption onto the NPs and BSA-mediated bridging. In BSA-alginate mixtures, the alginate hampers this interaction, most likely due to alginate-BSA complex formation. In most BSA-alginate mixtures as in alginate alone, NP aggregation is predominantly driven by weaker, pH-independent depletion forces. The stabilizing effect of alginate is only weakened at high BSA contents, when the electrostatic BSA-BSA attraction is not sufficiently screened by the alginate. This study clearly shows that it is crucial to consider correlative effects between multiple biofilm components to better understand the NP aggregation in the presence of complex biofilm substances. Single-component biofilm model systems based on comparing the total organic carbon (TOC) content of the extracellular biofilm substances, as usually considered, would have led to a misjudgment of the stability towards aggregation.

Bovine serum albumin-modified 3D printed alginate dialdehyde-gelatin scaffolds incorporating polydopamine/SiO2-CaO nanoparticles for bone regeneration

Three-dimensional (3D) printing allows precise manufacturing of bone scaffolds for patient-specific applications and is one of the most recently developed and implemented technologies. In this study, bilayer and multimaterial alginate dialdehyde-gelatin (ADA-GEL) scaffolds incorporating polydopamine (PDA)/SiO2-CaO nanoparticle complexes were 3D printed using a pneumatic extrusion-based 3D printing technology and further modified on the surface with bovine serum albumin (BSA) for application in bone regeneration. The morphology, chemistry, and in vitro bioactivity of PDA/SiO2-CaO nanoparticle complexes were characterized (n = 3) and compared with those of mesoporous SiO2-CaO nanoparticles. Successful deposition of the PDA layer on the surface of the SiO2-CaO nanoparticles allowed better dispersion in a liquid medium and showed enhanced bioactivity. Rheological studies (n = 3) of ADA-GEL inks consisting of PDA/SiO2-CaO nanoparticle complexes showed results that may indicate better injectability and printability behavior compared to ADA-GEL inks incorporating unmodified nanoparticles. Microscopic observations of 3D printed scaffolds revealed that PDA/SiO2-CaO nanoparticle complexes introduced additional topography onto the surface of 3D printed scaffolds. Additionally, the modified scaffolds were mechanically stable and elastic, closely mimicking the properties of natural bone. Furthermore, protein-coated bilayer scaffolds displayed controllable absorption and biodegradation, enhanced bioactivity, MC3T3-E1 cell adhesion, proliferation, and higher alkaline phosphatase (ALP) activity (n = 3) compared to unmodified scaffolds. Consequently, the present results confirm that ADA-GEL scaffolds incorporating PDA/SiO2-CaO nanoparticle complexes modified with BSA offer a promising approach for bone regeneration applications.

Comparison of the Adsorption and Desorption Dynamics of Biological Molecules on Alginate Hydrogel Microcapsules-The Case of Sugars, Polyphenols, and Proteins

The aim of this work was to analyze and compare the adsorption and desorption processes of carbohydrates (glucose as a model molecule), polyphenols (gallic acid as a model molecule), and proteins (bovine serum albumin, BSA as a model molecule) on alginate microcapsules. The adsorption and desorption processes were described by mathematical models (pseudo-first-order, pseudo-second-order, and Weber-Morris intraparticle diffusion model for adsorption, and first-order, Korsmeyer-Peppas, and the Higuchi model for desorption) in order to determine the dominant mechanisms responsible for both processes. By comparing the values of adsorption rate (k2) and initial adsorption rate (h0) based on the pseudo-first-order model, the lowest values were recorded for BSA (k1 = 0.124 ± 0.030 min-1), followed by glucose (k1 = 0.203 ± 0.041 min-1), while the model-obtained values for gallic acid were not considered significant at p < 0.05. For glucose and gallic acid, the limiting step of the adsorption process is the chemical sorption of substances, and the rate of adsorption does not depend on the adsorbate concentration, but depends on the capacity of the hydrogel adsorbent. Based on the desorption rates determined by the Korsmeyer-Peppas model (k), the highest values were recorded for gallic acid (k = 3.66236 ± 0.20776 g beads/mg gallic acid per min), followed by glucose (k = 2.55760 ± 0.16960 g beads/mg glucose per min) and BSA (k = 0.78881 ± 0.11872 g beads/mg BSA per min). The desorption process from alginate hydrogel microcapsules is characterized by the pseudo Fickian diffusion mechanism.

Effect of Molecules' Physicochemical Properties on Whey Protein/Alginate Hydrogel Rheology, Microstructure and Release Profile

The encapsulation of molecules with different physicochemical properties (theophylline, blue dextran, salicylic acid and insulin) in whey protein (WP) and alginate (ALG) microparticles (MP) for oral administration was studied. MP based on WP/ALG were prepared by a cold gelation technique and coated with WP solution after reticulation. Molecules influenced polymer solution viscosity and elasticity, resulting in differences regarding encapsulation efficiency (from 23 to 100%), MP structure and swelling (>10%) and in terms of pH tested. Molecule release was due to diffusion and/or erosion of MP and was very dependent on the substance encapsulated. All the loaded MP were successfully coated, but variation in coating thickness (from 68 to 146 µm) and function of the molecules encapsulated resulted in differences in molecule release (5 to 80% in 1 h). Gel rheology modification, due to interactions between WP, ALG, calcium and other substances, was responsible for the highlighted differences. Measuring rheologic parameters before extrusion and reticulation appeared to be one of the most important aspects to study in order to successfully develop a vector with optimal biopharmaceutical properties. Our vector seems to be more appropriate for anionic high-molecular-weight substances, leading to high viscosity and elasticity and to MP enabling gastroresistance and controlled release of molecules at intestinal pH.

Enhancing Physicochemical Properties and Biocompatibility of Hollow Porous Iron Oxide Nanoparticles through Polymer-Based Surface Modifications

In this study, we synthesized hollow porous iron oxide nanoparticles (HPIONPs) with surface modifications using polymers, specifically chitosan (Chi), polyethylene glycol (PEG), and alginate (Alg), to improve colloidal stability and biocompatibility. For colloidal stability, Alg-coated HPIONPs maintained size stability up to 24 h, with only an 18% increase, while Chi, PEG, and uncoated HPIONPs showed larger size increases ranging from 64 to 140%. The biocompatibility of polymer-coated HPIONPs was evaluated by assessing their cell viability, genotoxicity, and hemocompatibility. Across tested concentrations from 6.25 to 100 μg/mL, both uncoated and polymer-coated HPIONPs showed minimal cytotoxicity against three normal cell lines: RAW264.7, 3T3-L1, and MCF10A, with cell viability exceeding 80% at the highest concentration. Notably, polymer-coated HPIONPs exhibited nongenotoxicity based on the micronucleus assay and showed hemocompatibility, with only 2-3% hemolysis in mouse blood, in contrast to uncoated HPIONPs which exhibited 4-5%. Furthermore, we evaluated the cytotoxicity of HPIONPs on MDA-MB-231 breast cancer cells after a 2 h exposure to a stationary magnetic field, and the results showed the highest cell death of 38 and 29% when treated with uncoated and polymer-coated HPIONPs at 100 μg/mL, respectively. This phenomenon is attributed to iron catalyzing the Fenton and Haber-Weiss reactions, leading to reactive oxygen species (ROS)-dependent cell death (r ≥ 0.98). In conclusion, the hydrothermal synthesis and subsequent surface modification of HPIONPs with polymers showed improved colloidal stability, nongenotoxicity, and hemocompatibility compared to uncoated HPIONPs while maintaining closely similar levels of cytotoxicity against both normal and cancer cells. This research has paved the way for further exploration of polymer coatings to enhance the overall performance and safety profile of magnetic nanoparticles in delivering anticancer drugs.

In Vitro Tumor Mimetic Spheroid Model: Void Space within a Self-Detachable Cross-Linked Hydrogel

The three-dimensional (3D) spheroid cell culture model is crucial in screening anticancer drugs in vitro and understanding tumor cell behavior. However, the current in vitro models require highly skilled techniques. Here, we present an in vitro, tumor-mimetic, self-detachable, cancer cell spheroid model that provides the confined space of a tumor microenvironment, convenient spheroid retrieval, immunostaining, treatment, and imaging. We formed a void space within alginate macrobeads by ionic disintegration at a specific region inside. The macrobeads were further destabilized with bovine serum albumin to retrieve the spheroid cultured within the void space. Quantitative analysis of the immunofluorescence images of the cultured spheroids showed enhanced expressions of the hypoxia-inducible factor-1α (HIF-1α) and carbonic anhydrase-9 (CA-9), like monolayer cultures of cancer cells under hypoxic conditions (0.2% oxygen). Furthermore, adding CoCl2 to the cell culture media induces even higher amounts of HIF-1α and CA-9 in the cultured spheroids. In conclusion, the present work highlighted the in vitro spheroid model, which is closer to the tumor microenvironment and has user-friendly cell seeding, spheroid retrieval, and immunostaining steps.

Protein Folding Stability and Kinetics in Alginate Hydrogels

Proteins are commonly encapsulated in alginate gels for drug delivery and tissue-engineering applications. However, there is limited knowledge of how encapsulation impacts intrinsic protein properties such as folding stability or unfolding kinetics. Here, we use fast relaxation imaging (FReI) to image protein unfolding in situ in alginate hydrogels after applying a temperature jump. Based on changes in the Förster resonance energy transfer (FRET) response of FRET-labeled phosphoglycerate kinase (PGK), we report the quantitative impact of multiple alginate hydrogel concentrations on protein stability and folding dynamics. The gels stabilize PGK by increasing its melting temperature up to 18.4 °C, and the stabilization follows a nonmonotonic dependence on the alginate density. In situ kinetic measurements also reveal that PGK deviates more from two-state folding behavior in denser gels and that the gel decreases the unfolding rate and accelerates the folding rate of PGK, compared to buffer. Phi-value analysis suggests that the folding transition state of an encapsulated protein is structurally similar to that of folded protein. This work reveals both beneficial and negative impacts of gel encapsulation on protein folding, as well as potential mechanisms contributing to altered stability.

Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media

The inflammatory-associated corrosion of metallic dental and orthopedic implants causes significant complications, which may result in the implant's failure. The corrosion resistance can be improved with coatings and surface treatments, but at the same time, it might affect the ability of metallic implants to undergo proper osteointegration. In this work, alginate hydrogels with and without octacalcium phosphate (OCP) were made on 3D-printed (patterned) titanium alloys (Ti Group 2 and Ti-Al-V Group 23) to enhance their anticorrosion properties in simulated normal, inflammatory, and severe inflammatory conditions in vitro. Alginate (Alg) and OCP-laden alginate (Alg/OCP) hydrogels were manufactured on the surface of 3D-printed Ti substrates and were characterized with wettability analysis, XRD, and FTIR. The electrochemical characterization of the samples was carried out with open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was observed that the hydrophilicity of Alg/OCP coatings was higher than that of pure Alg and that OCP phase crystallinity was increased when samples were subjected to simulated biological media. The corrosion resistance of uncoated and coated samples was lower in inflammatory and severe inflammatory environments vs. normal media, but the hydrogel coatings on 3D-printed Ti layers moved the corrosion potential towards more nobler values, reducing the corrosion current density in all simulated solutions. These measurements revealed that OCP particles in the Alg hydrogel matrix noticeably increased the electrical charge transfer resistance at the substrate and coating interface more than with Alg hydrogel alone.

Flexible processing technology of coix seed prolamins by combined heat-ultrasound: Effects on their enzymatic hydrolysis characteristics and the hypoglycemic activities of derived peptides

The self-assembled structures of coix seeds affected the enzymatic efficiency and doesn't facilitate the release of more active peptides. The influence of heating combined with ultrasound pretreatment (HT + US) on the structure, enzymatic properties and hydrolysates (CHPs) of coix seed prolamin was investigated. Results showed that the structural of coix seed prolamins has changed after HT + US, including increased surface hydrophobicity, reduced α-helix and random coil content, and a decrease in particle size. So that, leads to changes in thermodynamic parameters such as an increase in the reaction rate constant and a decrease in activation energy, enthalpy and enthalpy. The fractions of <1000 Da, degree of hydrolysis and α-glucosidase inhibitory were increased in the HT + US group compared to single pretreatment by 0.68%-17.34%, 12.69%-34.43% and 30.00%-53.46%. The peptide content and α-glucosidase inhibitory activity of CHPs could be maintained at 72.21 % and 57.97 % of the initial raw materials after in vitro digestion. Thus, the findings indicate that HT + US provides a feasible and efficient approach to can effectively enhance the enzymatic hydrolysis efficiency and hypoglycaemic efficacy of CHPs.

A Plant-Based Animal Fat Analog Produced by an Emulsion Gel of Alginate and Pea Protein

As the market for plant-based meat analogs grows, the development of plant-based animal fat analogs has become increasingly important. In this study, we propose an approach by developing a gelled emulsion based on sodium alginate, soybean oil (SO), and pea protein isolate. Formulations containing 15% to 70% (w/w) SO were successfully produced without phase inversion. The addition of more SO resulted in pre-gelled emulsions with a more elastic behavior. After the emulsion was gelled in the presence of calcium, the color of the gelled emulsion changed to light yellow, and the formulation containing 70% SO exhibited a color most similar to actual beef fat trimming. The lightness and yellowness values were greatly influenced by the concentrations of both SO and pea protein. Microscopic images revealed that pea protein formed an interfacial film around the oil droplets, and the oil was more tightly packed at higher oil concentrations. Differential scanning calorimetry showed that lipid crystallization of the gelled SO was influenced by the confinement of the alginate gelation, but the melting behavior was like that of free SO. FTIR spectrum analysis indicated a potential interaction between alginate and pea protein, but the functional groups of SO were unchanged. Under mild heating conditions, gelled SO exhibited an oil loss similar to that observed in actual beef trims. The developed product has the potential to mimic the appearance and slow-rendering melting attribute of real animal fat.

Understanding the membrane fouling control process at molecular level in the heated persulfate activation- membrane distillation hybrid system

Sulfate radical (SO₄^●-) based advanced oxidation is considered as a promising pretreatment strategy to degrade organic pollutants and thereby mitigate the membrane fouling in the membrane process. In this study, heat-activated persulfate (PS) activation was integrated with the membrane distillation (MD) process for the alleviation of membrane fouling in treatment of wastewater treatment plant (WWTP) secondary effluent and surface water. In-depth understanding of the molecular fate during membrane fouling control process was performed by using a non-targeted screening method of two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF-MS) coupling with multiple characterizations. It was found that the heat-activated PS activation pretreatment could effectively degrade the dissolved organic matter (DOM) and change its molecular conformation, wherein the relative abundance of oxygen-containing substances was remarkably increased through oxygenation reactions. Moreover, the refractory organics with higher molecular weight (MW) and unsaturation degree were more inclined to be destroyed, following by partial mineralization during pretreatment process. It was also identified that oxygen-deficient compounds and the molecular formulas featuring higher double bond equivalent (DBE) values and lower MW tended to be deposited on the membrane surface to cause the membrane fouling. In particular, the aliphatic substances were the predominant components irrespective of membrane foulant samples from secondary effluent or surface water. Meanwhile, the complexation between organic compounds and high valence cations as well as the precipitation of inorganics were restrained owing to the reduction of DOM concentration and the transformation of molecular structure, consequently leading to reduced membrane fouling. This study is believed to further provide new insight into the membrane fouling control mechanism at molecular level.

Molecular structural modification of β-conglycinin using pH-shifting with ultrasound to improve emulsifying properties and stability

This present work underlines the effect of pH-shifting at pH 2 and pH 12 individually or combined with ultrasound treatment to modify the molecular structure of β-conglycinin (7S) on its emulsifying properties and stability. Fourier transform infrared (FTIR) spectroscopy and intrinsic fluorescence spectroscopy showed that pH-shifting improves the molecular structure of 7S, while ultrasound further promotes structural changes. In particular, the pH-shifting at pH 12 combined with ultrasound treatment (U-7S-12) resulted in more significant changes than the pH-shifting at pH 2 combined with ultrasound (U-7S-2). U-7S-12 showed a significant reduction in protein particle size from 152 to 34.77 nm and a relatively smooth protein surface compared to 7S. The protein had the highest surface hydrophobicity and flexibility at 81,560.0 and 0.45, respectively, and the free sulfhydryl content from 1.57 to 2.02 μmol/g. In addition, we characterized the emulsions prepared after 7S treatment. The single or combined treatment increased the interfacial protein adsorption of the samples, which showed lower viscosity and shear stress compared to 7S. The U-7S-12 emulsion exhibited the highest emulsifying properties and was more stable than other emulsions under creaming, heating, and freeze-thaw conditions. In summary, the concerted action of pH-shifting and ultrasound can modify the structure, and combined alkaline pH-shifting and ultrasound treatment can further improve the emulsifying properties and stability of 7S.

Protein Stabilization by Alginate Binding and Suppression of Thermal Aggregation

Polymers designed to stabilize proteins exploit direct interactions or crowding, but mechanisms underlying increased stability or reduced aggregation are rarely established. Alginate is widely used to encapsulate proteins for drug delivery and tissue regeneration despite limited knowledge of its impact on protein stability. Here, we present evidence that alginate can both increase protein folding stability and suppress the aggregation of unfolded protein through direct interactions without crowding. We used a fluorescence-based conformational reporter of two proteins, the metabolic protein phosphoglycerate kinase (PGK) and the hPin1 WW domain to monitor protein stability and aggregation as a function of temperature and the weight percent of alginate in solution. Alginate stabilizes PGK by up to 14.5 °C, but stabilization is highly protein-dependent, and the much smaller WW domain is stabilized by only 3.5 °C against thermal denaturation. Stabilization is greatest at low alginate weight percent and decreases at higher alginate concentrations. This trend cannot be explained by crowding, and ionic screening suggests that alginate stabilizes proteins through direct interactions with a significant electrostatic component. Alginate also strongly suppresses aggregation at high temperature by irreversibly associating with unfolded proteins and preventing refolding. Both the beneficial and negative impacts of alginate on protein stability and aggregation have important implications for practical applications.

Modifying the physicochemical properties, solubility and foaming capacity of milk proteins by ultrasound-assisted alkaline pH-shifting treatment

This study investigated the effects of different treatment of alkaline pH-shifting on milk protein concentrate (MPC), micellar casein concentrate (MCC) and whey protein isolate (WPI) assisted by the same ultrasound conditions, including changes in the physicochemical properties, solubility and foaming capacity. The solubility of milk proteins had a significant increase with gradual enhancement of ultrasound-assisted alkaline pH-shifting (p < 0.05), especially for MCC up to 99.50 %. Also, treatment made a significant decline in the particle size of MPC and MCC, as well as the turbidity of the proteins (p < 0.05). The foaming capacity of MPC, MCC, and WPI was all improved, especially at pH 11, and at this pH, the milk protein also showed the highest surface hydrophobicity. The best foaming capacity at pH 11 was the result of the combined effect of particle size, potential, protein conformation, solubility, and surface hydrophobicity. In conclusion, ultrasound-assisted pH-shifting treatment was found to be effective in improving the physicochemical properties and solubility and foaming capacity of milk proteins, especially MCC, with promising application prospect in food industry.

Impact of polysaccharide and protein interactions on membrane fouling: Particle deposition and layer formation

Membrane fouling, which limits the application of membrane bioreactors, has received considerable research attention in recent years. In this work, filtration modeling was performed in combination with surface plasmon resonance (SPR) analysis to investigate the membrane fouling mechanism. Sodium alginate (SA) and bovine serum albumin (BSA) were used to perform dead-end filtration on hydrophilic and hydrophobic poly (vinylidene fluoride) (PVDF) membranes. The initial foulant deposition and layer formation on membranes as well as the interaction between the BSA and SA were comprehensively analyzed. Results indicated that during SA filtration, initial fouling on hydrophilic membranes were primarily attributed to the particle-membrane interactions, while the fouling on the hydrophobic membrane were dominantly caused by the interactions among SA particles. The interaction between BSA and SA led to more severe membrane fouling and hydrophobic membrane was more sensitive to it, especially in the initial filtration process. The SPR results helped clarify the in-situ deposition behavior of BSA and SA particles on the PVDF surface. Compared to SA, BSA adsorbed faster on the PVDF membrane, and specific interactions played an essential role in BSA adsorption, whereas the deposition of SA on PVDF could be easily removed by shear force. Interactions between BSA and SA could alleviate the bonding between BSA and the PVDF membrane.

Influence of ultrasound treatment on the physicochemical and antioxidant properties of mung bean protein hydrolysate

This study aimed to investigate influence of ultrasonic treatment on physicochemical and antioxidant properties of mung bean protein hydrolysate (MPH). Physicochemical properties of MPH were evaluated by Tricine-SDS-PAGE, particle size distribution, fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy, among others. Radicals scavenging activities of ABTS, hydroxyl, superoxide anion, Fe²⁺ chelating ability and reducing power characterized antioxidant activities of MPH. MPH contained four bands of 25.6, 12.8, 10.6 and 4.9 kDa, in which 4.9 kDa was the most abundant. Ultrasonic treatment increased the contents of aromatic and hydrophobic amino acids in MPH. Ultrasonic treatment decreased the content of α-helix of MPH and increased β-sheet and β-turn compared to MPH. MPH-546 W (ultrasonic treatment 546 W, 20 min) had the lowest average particle size (290.13 nm), zeta potential (-36.37 mV) and surface hydrophobicity (367.95 A.U.). Antioxidant activities of ultrasonicated-MPH increased with the ultrasonic power, achieving the lowest IC₅₀ (mg/mL) of 0.1087 (ABTS), 1.796 (hydroxyl), 1.003 (superoxide anion) and 0.185 (Fe²⁺ chelating ability) in 546 W power. These results indicated ultrasonic treatment would be a promising method to improve the antioxidant properties of MPH, which would broaden the application scope of MPH as bioactive components in the food industry.

Complexation of CXCL12, FGF-2 and VEGF with Heparin Modulates the Protein Release from Alginate Microbeads

Long-term delivery of growth factors and immunomodulatory agents is highly required to support the integrity of tissue in engineering constructs, e.g., formation of vasculature, and to minimize immune response in a recipient. However, for proteins with a net positive charge at the physiological pH, controlled delivery from negatively charged alginate (Alg) platforms is challenging due to electrostatic interactions that can hamper the protein release. In order to regulate such interactions between proteins and the Alg matrix, we propose to complex proteins of interest in this study - CXCL12, FGF-2, VEGF - with polyanionic heparin prior to their encapsulation into Alg microbeads of high content of α-L-guluronic acid units (high-G). This strategy effectively reduced protein interactions with Alg (as shown by model ITC and SPR experiments) and, depending on the protein type, afforded control over the protein release for at least one month. The released proteins retained their in vitro bioactivity: CXCL12 stimulated the migration of Jurkat cells, and FGF-2 and VEGF induced proliferation and maturation of HUVECs. The presence of heparin also intensified protein biological efficiency. The proposed approach for encapsulation of proteins with a positive net charge into high-G Alg hydrogels is promising for controlled long-term protein delivery under in vivo conditions.

Interaction mechanism of collagen peptides with four phenolic compounds in the ethanol-water solution

This study demonstrated the interaction mechanism of collagen peptides (CPs) with 4-ethylphenol (4-EP), phenol, guaiacol, and 4-ethylguaiacol (4-EG) in the ethanol-water solution. The ultraviolet visible spectroscopy, zeta potential tests and hydrogen nuclear magnetic spectroscopy manifested that CPs interacted with the phenolic compounds. Meanwhile, Isothermal titration calorimetry determination indicated that the CPs was hydrogen bonded with 4-EP in 52 %(v/v) ethanol-water solution, while the hydrophobic forces played a major role in the interaction of CPs with guaiacol and 4-EG, respectively. Moreover, hydrogen and hydrophobic bonds were involved in the interaction between CPs and phenol. Finally, Head Space-solid Phase Microextraction Gas Chromatography Mass Spectrometry analysis indicated that the content of phenolic compounds in model solution efficiently decreased with the presence of CPs. In the real liquor, it was found that the content of volatile compounds (including phenolic compounds) was obviously decreased after CPs added.

Study of biological activities and physicochemical properties of Yamú (Brycon siebenthalae) viscera hydrolysates in sodium alginate-based edible coating solutions

The fishing industry produces waste such as viscera, which is an environmental problem for many countries. Obtaining protein from these wastes are useful for the food industry. In this study, the chemical composition, amino acid profile, solubility, digestibility and thermal properties of Yamú protein isolate (PI) and its hydrolysates obtained by enzymatic hydrolysis were characterized. The hydrolysates (0.05, 0.1, 0.5, 1 and 2% w/v) were mixed with a sodium alginate-based solution to form an edible coating solution (ECS). Antioxidant capacity antimicrobial activity, Zeta potential (ζ) and adsorption kinetics properties were determined. PI contains 88% (w/w) protein showing better solubility, digestibility and thermal stability properties. The hydrolysate concentrations with DPPH inhibitory ECS were 0.1 and 0.5% (w/v). The kinetic properties of ECS showed good stability and excellent adsorption. These results suggest that this Yamú protein has high nutritional potential as an ingredient for the production of functional foods.

3D-Printed Hydrogel-Filled Microneedle Arrays

Microneedle arrays (MNAs) have been used for decades to deliver drugs transdermally and avoid the obstacles of other delivery routes. Hydrogels are another popular method for delivering therapeutics because they provide tunable, controlled release of their encapsulated payload. However, hydrogels are not strong or stiff, and cannot be formed into constructs that penetrate the skin. Accordingly, it has so far been impossible to combine the transdermal delivery route provided by MNAs with the therapeutic encapsulation potential of hydrogels. To address this challenge, a low cost and simple, but robust, strategy employing MNAs is developed. These MNAs are formed from a rigid outer layer, 3D printed onto a conformal backing, and filled with drug-eluting hydrogels. Microneedles of different lengths are fabricated on a single patch, facilitating the delivery of various agents to different tissue depths. In addition to spatial distribution, temporal release kinetics can be controlled by changing the hydrogel composition or the needles' geometry. As a proof-of-concept, MNAs are used for the delivery of vascular endothelial growth factor (VEGF). Application of the rigid, resin-based outer layer allows the use of hydrogels regardless of their mechanical properties and makes these multicomponent MNAs suitable for a range of drug delivery applications.

Organic Fouling Impact in a Direct Contact Membrane Distillation System Treating Wastewater: Experimental Observations and Modeling Approach

This study aims to investigate the effect of operational conditions on organic fouling occurring in a direct contact membrane distillation (DCMD) system used to treat wastewater. A mixed solution of sodium alginate (SA) and bovine serum albumin (BSA) was used as a feed solution to simulate polysaccharides and proteins, respectively, assumed as the main organic foulants. The permeate flux was observed at two feed temperatures 35 and 50 °C, as well as three feed solution pH 4, 6, and 8. Higher permeate flux was observed for higher feed temperature, which allows higher vapor pressure. At higher pH, a smaller particle size was detected with lower permeate flux. A mathematical model based on mass balance was developed to simulate permeate flux with time by assuming (i) the cake formation controlled by attachment and detachment of foulant materials and (ii) the increase in specific cake resistance, the function of the cake porosity, as the main mechanisms controlling membrane fouling to investigate the fouling mechanism responsible of permeate flux decline. The model fitted well with the experimental data with R² superior to 0.9. High specific cake resistance fostered by small particle size would be responsible for the low permeate flux observed at pH 8.

Seaweed Polysaccharide Based Products and Materials: An Assessment on Their Production from a Sustainability Point of View

Among the various natural polymers, polysaccharides are one of the oldest biopolymers present on the Earth. They play a very crucial role in the survival of both animals and plants. Due to the presence of hydroxyl functional groups in most of the polysaccharides, it is easy to prepare their chemical derivatives. Several polysaccharide derivatives are widely used in a number of industrial applications. The polysaccharides such as cellulose, starch, chitosan, etc., have several applications but due to some distinguished characteristic properties, seaweed polysaccharides are preferred in a number of applications. This review covers published literature on the seaweed polysaccharides, their origin, and extraction from seaweeds, application, and chemical modification. Derivatization of the polysaccharides to impart new functionalities by chemical modification such as esterification, amidation, amination, C-N bond formation, sulphation, acetylation, phosphorylation, and graft copolymerization is discussed. The suitability of extraction of seaweed polysaccharides such as agar, carrageenan, and alginate using ionic solvent systems from a sustainability point of view and future prospects for efficient extraction and functionalization of seaweed polysaccharides is also included in this review article.

Effects of Molecular Weight and Degree of Esterification of Soluble Soybean Polysaccharide on the Stability of Casein under Acidic Conditions

The effects of molecular weight (MW) and degree of esterification (DE) of soluble soybean polysaccharide (SSPS) on the stability of casein under acidic conditions were investigated. The ability of SSPS to stabilize casein was characterized by the content of SSPS–casein complex, the LUMiSizer instability index, average particle size, zeta potential, and storage experiments. The long-term storage stability of the mixtures was related to their ability to combine casein and the stability of the complexes. At the same DE, SSPSs with medium MW formed more complexes with casein than SSPSs with high or low MW; and at the same MW, SSPSs with medium or low DE formed more complexes than SPSSs with high DE. In addition, SSPSs with higher MW had a better stabilizing behavior due to the large steric repulsion between complexes. SSPSs with high MW and low DE showed the best ability to stabilize casein under acid conditions.

Coagulopathy-independent, bioinspired hemostatic materials: A full research story from preclinical models to a human clinical trial

Since the first report of underwater adhesive proteins of marine mussels in 1981, numerous studies have reported mussel-inspired synthetic adhesive polymers. However, none of them have developed up to human-level translational studies. Here, we report a sticky polysaccharide that effectively promotes hemostasis from animal bleeding models to first-in-human hepatectomy. We found that the hemostatic material instantly generates a barrier layer that seals hemorrhaging sites. The barrier is created within a few seconds by in situ interactions with abundant plasma proteins. Therefore, as long as patient blood contains proper levels of plasma proteins, hemostasis should always occur even in coagulopathic conditions. To date, insufficient tools have been developed to arrest coagulopathic bleedings originated from genetic disorders, chronic diseases, or surgical settings such as organ transplantations. Mussel-inspired adhesion chemistry described here provides a useful alternative to the use of fibrin glues up to a human-level biomedical application.

Impact of Alginate Mannuronic-Guluronic Acid Contents and pH on Protein Binding Capacity and Complex Size

Alginates, serving as hydrocolloids in the food and pharma industries, form particles at pH < 4.5 with positively charged proteins, such as β-lactoglobulin (β-Lg). Alginates are linear anionic polysaccharides composed of 1,4-linked β-d-mannuronate (M) and α-l-guluronate (G) residues. The impact of M and G contents and pH is investigated to correlate with the formation and size of β-Lg alginate complexes under relevant ionic strength. It is concluded, using three alginates of M/G ratios 0.6, 1.1, and 1.8 and similar molecular mass, that β-Lg binding capacity is higher at pH 4.0 than at pH 2.65 and for high M content. By contrast, the largest particles are obtained at pH 2.65 and with high G content. At pH 4.0 and 2.65, the stoichiometry was 28-48 and 3-10 β-Lg molecules bound per alginate, respectively, increasing with higher M content. The findings will contribute to the design of formation of the desired alginate-protein particles in the acidic pH range.

Complex coacervates between bovine serum albumin and anionic polysaccharides: formation and characterization

Abstract The comparative study regarding complexes coacervated between Bovine Serum Albumin (BSA) and different polysaccharides, Pectin (PEC) and Gum Acacia (GA), was carried out by evaluating the influence of different ratios (protein:polysaccharide) and sodium chloride (NaCl) concentrations on turbidity and zeta potential. The BSA:PEC complexes were formed in a 10:1 ratio whereas BSA:GA at 3:1. The complexation pH showed different behavior, BSA: PEC complexes exhibited maximum turbidity in a wide pH range (4.9 to 1.5), while BSA: GA had maximum turbidity at pH 3.5. The increase in the concentration of NaCl negatively influenced the complexation. The NaCl concentration of 0.40 mol L-1 suppressed the interaction in BSA:PEC (10:1) and reduced the range formation of BSA:GA (3:1). The Fourier Transform Infrared (FTIR) demonstrated the participation not only of electrostatic interactions, but also of hydrogen bonds in the complexation. This initial study elucidated fundamental aspects about the formation of coacervate complexes between BSA:GA/PEC that assist in directing its application in food products especially, in acidic matrices (pH~4.0) as well as with low concentration of salts, in view of the effect of pH on maximum formation and sensitivity to NaCl. These complexes can be added directly to products in order to add nutritional value or even be used as a new matrix for the encapsulation of bioactive compounds.

Modification of rapeseed protein by ultrasound-assisted pH shift treatment: Ultrasonic mode and frequency screening, changes in protein solubility and structural characteristics

We investigated the effect of ultrasound-assisted pH shift treatment on the micro-particle, molecular, and spatial structure of rapeseed protein isolates (RPI). Various ultrasonic frequency modes (fixed, and sweep) was used. Protein characterization by the indexes: particle size, zeta potential, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), scanning electron microscopy (SEM), free sulfhydryl (SH), surface hydrophobicity (Ho), Fourier transform infrared Spectrum (FTIR) and fluorescence intensity was studied to elucidate the changes in solubility and structural attributes of RPI. The results showed that ultrasonic frequency and working modes substantially altered the structure, and modified the solubility of RPI. Ultra + pH mode at fixed frequency of 20 kHz had the best effect on the solubility of RPI. Under the condition of ultra + pH mode, 20 kHz at pH 12.5, solubility, compared to control, increased from 8.90% to 66.84%; and the change in molecular structure of RPI was characterized by smaller particles (from 330.90 to 115.77 nm), high zeta potential (from -17.95 to -14.43 mV, p < 0.05), and increased free sulfhydryl (from 11.63 to 24.50 µmol/g) compared to control. Likewise, surface hydrophobicity increased (from 2053.9 to 2649.4, p < 0.05), whilst ɑ-helix and random coil decreased (p < 0.05), compared to control. The fluorescence spectroscopy and FTIR spectroscopy showed that the secondary and tertiary structure of the RPI were altered. These observations revealed that changes in RPI structure was the direct factor affecting solubility. In conclusion, ultrasound assisted pH shift treatment was proven to be an effective method for the modification of protein, with promising application in food industry.

Development of a fluorometric measurement system used in biological samples upon the determination of iron (II) metal ion

2-thioxanthone thioacetic acid (TXSCH₂COOH, T), which has a fluorometric character, was used for new fluorometric system upon Fe(II) analysis in biological samples as the main target. T-BSA binary complex was firstly consisted with non-covalent interactions between T and BSA at the equilibrium concentration as 1.77 × 10^-4.M. T-BSA binary complex emission was increased at the ratio of 24.40% due to stabilization property of BSA (pH:7), compared with T emission intensity. Fluorescence emission spectroscopy was used for the all measurements because of an economic, a sensitive and a practical method compared with other spectroscopic analysis. T-BSA-Fe(II) triple complex was also obtained by adding Fe(II) ion to T-BSA binary complex solution. Its characterization was performed to be investigated with optimum excitation wavelength, buffer concentration, pH and temperature as 297 nm, 10^-3 M Tris HCl (10^-2M NaCI), pH:7.2 at 25 °C, respectively. The results of Fe(II) analysis in serum showed a certain response in fluorometric T-BSA-Fe(II) triple complex measurement system as 50.42 ± 5.8 µg/dL. The analyses of our fluorometric triple complex system were compared with the reference electrochemiluminescence method and similar results were obtained. Fluorometric measurements of T-BSA-Fe(II) triple complex, its characterization and Fe(II) analysis in this system have not been investigated in literature gives originality to our study.

Addition of Anionic Polysaccharide Stabilizers Modulates In Vitro Digestive Proteolysis of a Chocolate Milk Drink in Adults and Children

There is a need to better understand the possible anti-nutritional effect of food stabilizers on the digestibility of important macronutrients, like proteins. This study hypothesized that the anionic nature of κ-, ι-, λ-, Carrageenan (CGN) and xanthan gum directs their interactions with food proteins leading to their subsequent attenuated digestive proteolysis. Model chocolate milk drinks were tested for their colloidal properties, viscosity and proteolytic breakdown in adults and children using in vitro digestion models coupled with proteomic analyses. SDS-PAGE analyses of gastro-intestinal effluents highlight stabilizers hinder protein breakdown in adults and children. Zeta potential and colloidal particle size were the strongest determinants of stabilizers’ ability to hinder proteolysis. LC-MS proteomic analyses revealed stabilizer addition significantly reduced bioaccessibility of milk-derived bioactive peptides with differences in liberated peptide sequences arising mainly from their location on the outer rim of the protein structures. Further, liberation of bioactive peptides emptying from a child stomach into the intestine were most affected by the presence of ι-CGN. Overall, this study raises the notion that stabilizer charge and other properties of edible proteins are detrimental to the ability of humans to utilize the nutritional potential of such formulations. This could help food professionals and regulatory agencies carefully consider the use of anionic stabilizers in products aiming to serve as protein sources for children and other liable populations.