Interactions between β-Lactoglobulin and 3,3'-Diindolylmethane in Model System

Sortase A Inhibitor Protein Nanoparticle Formulations Demonstrate Antibacterial Synergy When Combined with Antimicrobial Peptides

Sortase A (SrtA) is an enzyme which attaches proteins, including virulence factors, to bacterial cell walls. It is a potential target for developing anti-virulence agents against pathogenic and antimicrobial resistant bacteria. This study aimed to engineer 𝛽-lactoglobulin protein nanoparticles (PNPs) for encapsulating safe and inexpensive natural SrtA inhibitors (SrtAIs; trans-chalcone (TC), curcumin (CUR), quercetin (QC), and berberine (BR)) to improve their poor aqueous dispersibility, to screen for synergy with antimicrobial peptides (AMPs), and to reduce the cost, dose, and toxicity of AMPs. Minimum inhibitory concentration (MIC), checkerboard synergy, and cell viability assays were performed for SrtAI PNPs against Gram-positive (methicillin-sensitive and -resistant S. aureus) and Gram-negative (E. coli, P. aeruginosa) bacteria alone and combined with leading AMPs (pexiganan, indolicidin, and a mastoparan derivative). Each SrtAI PNP inhibited Gram-positive (MIC: 62.5-125 µg/mL) and Gram-negative (MIC: 31.3-500 µg/mL) bacterial growth. TC PNPs with pexiganan demonstrated synergy against each bacteria, while BR PNPs with pexiganan or indolicidin provided synergy towards S. aureus. Each SrtAI PNP inhibited SrtA (IC₅₀: 25.0-81.8 µg/mL), and did not affect HEK-293 cell viability at their MIC or optimal synergistic concentrations with AMPs. Overall, this study provides a safe nanoplatform for enhancing antimicrobial synergy to develop treatments for superbug infections.

Alginate and β-lactoglobulin matrix as wall materials for encapsulation of polyphenols to improve efficiency and stability

The present study aimed at developing novel encapsulate materials of calcium-alginate and β-lactoglobulin complex for polyphenols using the jet-flow nozzle vibration method. Encapsulated microbeads were characterized using SEM, FTIR, DSC, and MSI. The encapsulation efficiency of the microbeads varied depending upon the coating material in the range of 74.17–84.87%. Calcium-alginate-β-lactoglobulin microbeads (CABM) exhibited a smooth surface and uniform shape with an average particle size of 1053.73 nm. CABM also showed better thermal and storage stabilities as compared to calcium alginate microbeads. The CABM resulted in excellent target release of polyphenols (84%) in the intestine, which was more than 3-fold the bio-accessibility offered by free polyphenol powder. Further study on individual phenolic acids after simulated in-vitro digestion (SIVD), photo-oxidative and osmotic stress revealed that CABM significantly retained a higher amount of polyphenols and exhibited improved antioxidant capacity after SIVD environment, and may have high industrial application for nutraceutical production.

Development of chloramphenicol wound dressing protein-based microparticles in chitosan hydrogel system for improved effectiveness of dermal wound therapy

Skin wounds have been reported to increase the number of microbial colonies susceptible to infection. Treatments using oral antibiotics have been limited due to their toxicity and hydrophobic characteristics. In this study, we developed a formulation of chloramphenicol microparticles (CPL MPs), which was modified into chitosan hydrogel to increase treatment efficiency in targeting infections and creating an optimal environment to support the healing process. CPL MPs were prepared by a cross-linker stabilized method using whey protein (WPI) biopolymer, and the CPL MPs hydrogel was designed using chitosan biopolymer. Based on the result, CPL-loaded MPs showed desired physical and encapsulation characteristics. In the in vitro study, drug release of CPL MPs in simulated wound fluid represented approximately 99.40 ± 7.01 % of the system after 24 h. The antibacterial activity of CPL-loaded MPs formulation (MIC value 12.5 μg/mL, MBC 25 μg/mL) was effective as MIC concentration increased. Furthermore, the formulation of CPL MPs into hydrogel showed a better dermatokinetic profile compared to hydrogel with pure CPL. Interestingly, the antibacterial activity of the ex vivo infection model showed that Staphylococcus aureus activity decreased by up to 99.98 % after 24 h administration of CPL MPs hydrogel when compared to pure-CPL hydrogel and blank hydrogel. These studies have confirmed that incorporating CPL MPs into hydrogel can provide a promising approach to skin infection treatment.

Alleviating Aspirin-Induced Gastric Injury by Binding Aspirin to β-Lactoglobulin

Purpose

Gastric injury is a major issue for long-term administration of aspirin. In this work, we tried to explore the possibility of using BLG to alleviate aspirin-induced gastric injury, because of excellent abilities of BLG in loading drug molecules.

Methods

Various spectroscopic techniques and molecular docking methods were applied to investigate the interaction mechanism between BLG and aspirin. Animal experiments were performed to figure out the effects of taking aspirin-BLG on the stomach.

Results

Our results demonstrate that aspirin could bind with BLG to form stable aspirin-BLG complex (the binding constant K_b= 2.051 × 10³ M⁻¹). The formation process is endothermic (∆H>0) and the main acting force is hydrophobic force. Our data also show that the aspirin-BLG complex is formed with a higher affinity in simulated gastric fluid and could remain stable for several hours, which might arise from its special binding mode under acidic condition and the resistance of BLG to gastric digestion. Furthermore, animal models (rats with aspirin-induced gastric damage) were built. The results of animal experiments reveal that the oral administration of aspirin-BLG could cause less damage to gastric tissue, and it also hardly triggers obvious inflammatory responses.

Conclusion

This study would contribute to an in-depth understanding of the interaction mechanism between BLG and aspirin. It is reasonable to believe that using BLG to bind with aspirin would be a potential way to alleviate the aspirin-induced gastric injury.

Spectroscopic and Theoretical Investigation of β-Lactoglobulin Interactions with Hematoporphyrin and Protoporphyrin IX

Hematoporphyrin (HP) and protoporphyrin IX (PPIX) are useful porphyrin photosensitizers with significant application values in photodynamic therapy. Currently, many strategies have been developed to improve their clinical performance, such as incorporating them with nanoparticle (NP) carriers. In this work, we studied the possibility of using β-lactoglobulin (BLG) as a potential NP carrier due to their hydrophobic affinity, pH sensitivity, and low cost of extraction and preservation. The interaction mechanisms of BLG with HP and PPIX were investigated using spectroscopic techniques and molecular docking methods. The molecular docking results agree well with the experimental results, which demonstrate that the formations of HP-BLG and PPIX-BLG complexes are endothermic processes and the main acting force is hydrophobic force. Furthermore, the opening-closure states of EF loop have a great influence on the HP-BLG complex formation, where the central hydrophobic cavity of β-barrel is available for HP binding at pH 7.4 but not available at pH 6.2. However, the formation of the PPIX-BLG complex is less dependent on the states of the EF loop, and the binding sites of PPIX are both located on the external surface of BLG under both pH 7.4 and 6.2 conditions. All of our results would provide new insight into the mechanisms of noncovalent interactions between BLG and HP/PPIX. It is believed that this work indicated the potential application values of BLG in designing pH-sensitive carriers for the delivery of HP and PPIX, as well as other poorly soluble drugs.

Polymerized Whey Protein Concentrate-Based Glutathione Delivery System: Physicochemical Characterization, Bioavailability and Sub-Chronic Toxicity Evaluation

Glutathione (GSH) is a powerful antioxidant, but its application is limited due to poor storage stability and low bioavailability. A novel nutrient encapsulation and delivery system, consisting of polymerized whey protein concentrate and GSH, was prepared and in vivo bioavailability, antioxidant capacity and toxicity were evaluated. Polymerized whey protein concentrate encapsulated GSH (PWPC-GSH) showed a diameter of roughly 1115 ± 7.07 nm (D50) and zeta potential of 30.37 ± 0.75 mV. Differential scanning calorimetry (DSC) confirmed that GSH was successfully dispersed in PWPC particles. In vivo pharmacokinetics study suggested that PWPC-GSH displayed 2.5-times and 2.6-fold enhancement in maximum concentration (Cmax) and area under the concentration-time curve (AUC) as compared to free GSH. Additionally, compared with plasma of mice gavage with free GSH, significantly increased antioxidant capacity of plasma in mice with PWPC-GSH was observed (p < 0.05). Sub-chronic toxicity evaluation indicated that no adverse toxicological reactions related to oral administration of PWPC-GSH were observed on male and female rats with a diet containing PWPC-GSH up to 4% (w/w). Data indicated that PWPC may be an effective carrier for GSH to improve bioavailability and antioxidant capacity.

pH-Sensitive Dairy-Derived Hydrogels with a Prolonged Drug Release Profile for Cancer Treatment

A novel versatile biocompatible hydrogel of whey protein isolate (WPI) and two types of tannic acid (TAs) was prepared by crosslinking of WPI with TAs in a one-step method at high temperature for 30 min. WPI is one common protein-based preparation which is used for hydrogel formation. The obtained WPI-TA hydrogels were in disc form and retained their integrity after sterilization by autoclaving. Two TA preparations of differing molecular weight and chemical structure were compared, namely a polygalloyl glucose-rich extract-ALSOK 02-and a polygalloyl quinic acid-rich extract-ALSOK 04. Hydrogel formation was observed for WPI solutions containing both preparations. The swelling characteristics of hydrogels were investigated at room temperature at different pH values, namely 5, 7, and 9. The swelling ability of hydrogels was independent of the chemical structure of the added TAs. A trend of decrease of mass increase (MI) in hydrogels was observed with an increase in the TA/WPI ratio compared to the control WPI hydrogel without TA. This dependence (a MI decrease-TA/WPI ratio) was observed for hydrogels with different types of TA both in neutral and acidic conditions (pH 5.7). Under alkaline conditions (pH 9), negative values of swelling were observed for all hydrogels with a high content of TAs and were accompanied by a significant release of TAs from the hydrogel network. Our studies have shown that the release of TA from hydrogels containing ALSOK04 is higher than from hydrogels containing ALSOK 02. Moreover, the addition of TAs, which display a strong anti-cancer effect, increases the cytotoxicity of WPI-TAs hydrogels against the Hep-2 human laryngeal squamous carcinoma (Hep-2 cells) cell line. Thus, WPI-TA hydrogels with prolonged drug release properties and cytotoxicity effect can be used as anti-cancer scaffolds.

Preparation and Characterization of Soy Isoflavones Nanoparticles Using Polymerized Goat Milk Whey Protein as Wall Material

Soy isoflavones (SIF) are a group of polyphenolic compounds with health benefits. However, application of SIF in functional foods is limited due to its poor aqueous solubility. SIF nanoparticles with different concentrations were prepared using polymerized goat milk whey protein (PGWP) as wall material. The goat milk whey protein was prepared from raw milk by membrane processing technology. The encapsulation efficiencies of all the nanoparticles were found to be greater than 70%. The nanoparticles showed larger particle size and lower zeta potential compared with the PGWP. Fourier Transform Infrared Spectroscopy indicated that the secondary structure of goat milk whey protein was changed after interacting with SIF, with transformation of α-helix and β-sheet to disordered structures. Fluorescence data indicated that interactions between SIF and PGWP decreased the fluorescence intensity. All nanoparticles had spherical microstructure revealed by Transmission Electron Microscope. Data indicated that PGWP may be a good carrier material for the delivery of SIF to improve its applications in functional foods.

Formation and Characterization of β-Lactoglobulin and Gum Arabic Complexes: the Role of pH

Protein–polysaccharide complexes have received increasing attention as delivery systems to improve the stability and bioavailability of multiple bioactive compounds. However, deep and comprehensive understanding of the interactions between proteins and polysaccharides is still required for enhancing their loading efficiency and facilitating targeted delivery. In this study, we fabricated a type of protein–polysaccharide complexes using food-grade materials of β-lactoglobulin (β-Lg) and gum arabic (GA). The formation and characteristics of β-Lg–GA complexes were investigated by determining the influence of pH and other factors on their turbidity, zeta-potential, particle size and rheology. Results demonstrated that the β-Lg and GA suspension experienced four regimes including co-soluble polymers, soluble complexes, insoluble complexes and co-soluble polymers when the pH ranged from 1.2 to 7 and that β-Lg–GA complexes formed in large quantities at pH 4.2. An increased ratio of β-Lg in the mixtures was found to promote the formation of β-Lg and GA complexes, and the optimal β-Lg/GA ratio was found to be 2:1. The electrostatic interactions between the NH₃⁺ group in β-Lg and the COO⁻ group in GA were confirmed to be the main driving forces for the formation of β-Lg/GA complexes. The formed structure also resulted in enhanced thermal stability and viscosity. These findings provide critical implications for the application of β-lactoglobulin and gum arabic complexes in food research and industry.

Preparation and Characterization of Whey Protein Isolate-DIM Nanoparticles

3,3’-Diindolylmethane (DIM) is a bioactive compound found in Cruciferous vegetables that possesses health benefits such as antioxidant, anticancer, and anti-inflammatory effects. However, hydrophobicity and photolabile limit its pharmaceutical applications. This study aims to prepare and characterize DIM-encapsulated whey protein isolate (WPI) nanoparticles mixed at different ratios of WPI and DIM using the combined heating–ultrasound method. Results showed that all the samples showed adequate physicochemical characteristics: The mean particle size of the nanoparticles could be controlled down to 96–157 nm depending on the DIM to WPI ratio used in the preparation with a low polydispersity index (<0.5), higher negative values of zeta potential (>−40 mV) as well as with greater encapsulation efficiency (>82%). Flow behavior indices showed the shear-thinning Non-Newtonian or pseudoplastic (n < 1) behavior of the nanoparticles. The thermal properties were characterized by differential scanning calorimetry (DSC), which showed that DIM was successfully entrapped in WPI nanoparticles. The secondary structure of WPI was changed after DIM incorporation; electrostatic interaction and hydrogen bonding were major facilitating forces for nanoparticles formation, confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Transmission electron microscopy (TEM) micrographs showed that all the samples had a smooth surface and spherical structure. The wall material (WPI) and encapsulation method provide effective protection to DIM against UV light and a broad range of physiologically relevant pH’s (2.5, 3.5, 4.5, 5.5, and 7). In conclusion, whey protein isolate (WPI)-based nanoparticles are a promising approach to encapsulate DIM and overcome its physicochemical limitations with improved stability.