Nanostructure development during peroxidase catalysed cross-linking of α-lactalbumin

Preparation of enzymatically cross-linked α-lactalbumin nanoparticles and their application for encapsulating lycopene

High internal phase Pickering emulsions (HIPPEs) stabilized by protein nanoparticles have been widely reported, but the use of enzymatic methods for preparing these nanoparticles remains underexplored. Our hypothesis is that enzymatically crosslinked α-lactalbumin (ALA) nanoparticles (ALATGs) prepared using transglutaminase will demonstrate improved properties as stabilizers for HIPPEs. In this study, we investigated the physicochemical properties and microstructures of ALATGs, finding that enzymatic crosslinking could be enhanced by removing Ca2+ ions from ALA and preheating the proteins (85 °C, 15 min). The electrical charge, secondary structure, and surface hydrophobicity of ALATGs were found to depend on crosslinking conditions. HIPPEs formed with an ALA concentration of 10 mg/mL and an enzyme activity of 120 U/g exhibited the highest apparent viscosity and mechanical strength, as well as significantly improved loading capacity and photostability for the encapsulated lycopene. Overall, our results support the hypothesis that ALATG-nanoparticles show superior performance as emulsifiers compared to ALA-nanoparticles.

Ultrasound-assisted immersion freezing reduces the structure and gel property deterioration of myofibrillar protein from chicken breast

The effects of air freezing (AF), immersion freezing (IF) and ultrasound-assisted immersion freezing (UF) at different power levels (125, 165, 205 and 245 W) on the structure and gel properties of the myofibrillar protein (MP) of chicken breast were investigated. UF at 165 W (UF-165) had no obvious negative impact on the primary structure of the MP and effectively reduced the change in the secondary and tertiary structure. In addition, UF-165 significantly reduced the losses in the elastic modulus (G'), gel strength, and gel water holding capacity (P < 0.05). According to low field nuclear magnetic resonance analysis, the T₂₁ and T₂₂ of the UF-165 MP gels were shorter than those of the AF and IF samples, which meant that the UF-165 reduced the mobility of the immobilized water and free water in MP gel. A scanning electron microscopy analysis showed that the appropriate ultrasonic power promoted the formation of a compact and homogeneous protein gel network. These results suggested that the appropriate ultrasonic power maintained the MP structure and reduced the loss of gel quality.

Potential of nano-phytochemicals in cervical cancer therapy

Cervical cancer is common among women with a recurrence rate of 35% despite surgery, radiation, and chemotherapy. Patients receiving chemotherapy or radiotherapy routinely experience several side effects including toxicity, non-targeted damage of tissues, hair loss, neurotoxicity, multidrug resistance (MDR), nausea, anemia and neutropenia. Phytochemicals can interfere with almost every stage of carcinogenesis to prevent cancer development. Many natural compounds are known to activate/deactivate multiple redox-sensitive transcription factors that modulate tumor signaling pathways. Polyphenols have been found to be promising agents against cervical cancer. However, applications of phytochemicals as a therapeutic drug are limited due to low oral bioavailability, poor aqueous solubility and requirement of high doses. Nano-sized phytochemicals (NPCs) are promising anti-cancer agents as they are required in minute quantities which lowers overall treatment costs. Several phytochemicals, including quercetin, lycopene, leutin, curcumin, green tea polyphenols and others have been packaged as nanoparticles and proven to be useful in nano-chemoprevention and nano-chemotherapy. Nanoparticles have high biocompatibility, biodegradability and stability in biological environment. Nano-scale drug delivery systems are excellent source for enhanced drug specificity, improved absorption rates, reduced drug degradation and systemic toxicity. The present review discusses current knowledge in the involvement of phytochemical nanoparticles in cervical cancer therapy over conventional chemotherapy.

Protein-Based Nanostructures for Food Applications

Proteins are receiving significant attention for the production of structures for the encapsulation of active compounds, aimed at their use in food products. Proteins are one of the most used biomaterials in the food industry due to their nutritional value, non-toxicity, biodegradability, and ability to create new textures, in particular, their ability to form gel particles that can go from macro- to nanoscale. This review points out the different techniques to obtain protein-based nanostructures and their use to encapsulate and release bioactive compounds, while also presenting some examples of food grade proteins, the mechanism of formation of the nanostructures, and the behavior under different conditions, such as in the gastrointestinal tract.

Ethylcellulose Colloids Incubated in Dilute Solution

This study revealed, for the first time, that dilute solutions made of a representative series of commercial ethylcellulose (EC; molecular weights 77-305 kDa, provided by the manufacturer) and four distinct organic solvents (α-terpineol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TPIB), tetrahydrofuran (THF), and benzene) can be used to foster stabilized, nearly monodisperse, nanoscale (pure) polymer colloid, with no isolated chains present. Using combined light-scattering (dynamic light scattering, static form factor, and Zimm/Berry plots) and intrinsic viscosity (Tanglertpaibul-Rao, Huggins, and Kraemer plots) analyses, the structural features of colloidal EC aggregates, ρ = ⟨R_g⟩/⟨R_h⟩ = 0.67-0.83, were first shown to be described rather well by the theory on colloidal spheres (⟨R_g⟩ and ⟨R_h⟩ being the mean radius of gyration and the hydrodynamic radius, respectively). An empirical scaling law relating the intrinsic viscosity to the mean colloid size can thus be established: [η]_H = (1.7 ± 0.2) ×10^-3 ⟨R_h⟩^(2.1±0.3) ([η]_H and ⟨R_h⟩ in units of mL/g and nm, respectively), which may be contrasted with the Zimm model for isolated Gaussian coils, [η]_H ∼ ⟨R_h⟩¹, and the Einstein equation for isolated solid spheres, [η]_H ∼ ⟨R_h⟩⁰. Optical microscopy images of thin films cast from different EC solutions clearly revealed the abundance of micron EC agglomerates, contrary to the uniform thin-film morphology produced from a dilute polystyrene solution, which serves as a reference solution composed of isolated chains. These observations point to new features and applications of EC dispersions.

Changes in protein conformation and surface hydrophobicity upon peroxidase-catalyzed cross-linking of apo-α-lactalbumin

In this study, we explore the effect of peroxidase-catalyzed cross-linking on the molecular conformation of apo-α-lactalbumin (apo-α-LA) and the resulting changes in protein surface hydrophobicity. In studying conformational changes, we distinguish between early stages of the reaction ("partial cross-linking"), in which only protein oligomers (10(6) Da > Mw ≥ 10(4) Da) are formed, and a later stage ("full cross-linking"), in which larger protein particles (Mw ≥ 10(6) Da) are formed. Partial cross-linking induces a moderate loss of α-helical content. Surprisingly, further cross-linking leads to a partial return of α-helices that are lost upon early cross-linking. At the same time, for partially and fully cross-linked apo-α-LA, almost all tertiary structure is lost. The protein surface hydrophobicity first increases for partial cross-linking, but then decreases again at full cross-linking. Our results highlight the subtle changes in protein conformation and surface hydrophobicity of apo-α-LA upon peroxidase-catalyzed cross-linking.