Promising application of probiotic microorganisms as Pickering emulsions stabilizers.

The purpose of this work was to study the ability of nineteen food-grade microorganisms as Pickering emulsion (PE) stabilizers. Medium-chain triacylglycerol (MCT) oil-in-water (50:50) PEs were fabricated by 10 wt% or 15 wt% of thermally-inactivated yeast, cocci, Bacillus spp. and lactobacilli cells. The characteristics of microorganisms related to "Pickering stabilization" including morphology, surface charge, interfacial tension, and "contact angle" were firstly studied. After that, the cells-stabilized PEs were characterized from both kinetic and thermodynamic viewpoints, microstructure and rheological properties. The interfacial tension and "contact angle" values of various microorganisms ranged from 16.33 to 38.31 mN/m, and from 15° to 106°, respectively. The mean droplet size of PEs ranged from 11.51 to 57.69 µm. Generally, the physical stability of cell-stabilized PEs followed this order: lactobacilli > Bacillus spp. > cocci > yeast. These variations were attributed to the morphology and cell wall composition. Increasing the microorganism concentration significantly increased the physical stability of PEs from a maximum of 12 days at 10 wt% to 35 days at 15 wt% as a result of better interface coverage. Shear-thinning and dominant elastic behaviors were observed in PEs. Physical stability was affected by the free energy of detachment. Therefore, food-grade microorganisms are suggested for stabilizing PEs.

Dual antioxidant-photosensitizing hydrogel system: Cross-linking of chitosan with tannic acid for enhanced photodynamic efficacy.

Herein, a new antioxidant-photosensitizing hydrogel based on chitosan has been developed to control photodynamic therapy (PDT) activity in cancer treatment. In PDT, photosensitizers generate reactive oxygen species (ROS) during photochemical reactions, leading oxidative damage to cancer cells. However, high ROS levels are lethal to non-target healthy cells and tissues such as endothelial cells and blood cells. To mediate these drawbacks, we improved PDT with a natural polyphenolic antioxidant, Tannic acid (TA), to control the ROS level and minimize side effects through singlet oxygen (1O2) scavenging. In this work, chitosan-based hydrogels were designed using tannic acid as an antioxidant cross-linker and loaded with water-soluble N, N'-di-(l-alanine)-3,4,9,10-perylene tetracarboxylic diimide (PDI-Ala) as a photosensitizer. Our results showed that the hydrogel formed a three-dimensional (3D) microstructure with good mechanical strength and significant singlet oxygen production and antioxidant activity. In addition, the behavior of human melanoma cell line A375 and dental pulp stem cells (as normal cells) was compared and studied during an in vitro photodynamic treatment. Normal cells had a higher viability than cancer cells, indicating that the PDT is more effective on cancer cells than on normal cells. The new hydrogels could be applied as an effective new drug to control PDT performance.

Physicochemical properties of fish oil in water multilayer emulsions prepared by a mixture of whey protein isolate and water-soluble fraction of Farsi gum.

Physicochemical properties and storage stability of fish oil (FO) in water multilayer emulsions, stabilized with different mixtures of whey protein isolate (WPI) and water-soluble fraction of Farsi gum (WSFG), were studied under the effects of total biopolymer concentration (TBC), WSFG:WPI mixing ratio (MR) and pH for 1 month. pH reduction decreased the surface potential of dispersed droplets; however, an increase in the WSFG:WPI MR (at constant pH values corresponding to electrostatic interactions) significantly increased the absolute values of surface potential and hence the physical stability of emulsions. An increase in TBC increased droplet size and emulsion viscosity. The emulsion viscosity was also positively correlated with WSFG:WPI MR. During storage, higher values of TBC and WSFG:WPI MRs led to lower absorbance values. An increase in the WSFG:WPI MR and TBC significantly retarded the oxidation of emulsified FO.

Gelatin-hydroxypropyl methylcellulose water-in-water emulsions as a new bio-based packaging material.

Gelatin and hydroxypropyl methylcellulose (HPMC) are two incompatible and immiscible biopolymers which cannot form homogeneous composite films using usual methods. In this study, to prevent phase separation, gelatin-HPMC water-in-water (W/W) emulsion was utilized to from transparent composite films by entrapment the HPMC dispersed droplets in gelatin continuous network. The physicochemical and mechanical properties of emulsion-based films containing different amounts (5-30%) of dispersed phase were determined and compared with those of individual polymer-based films. Incorporating HPMC into W/W emulsion-based films had no significant effect on the tensile strength. The flexibility of composite films decreased at HPMC concentrations below 20%. The depletion layer at the droplets interface reduced the diffusion of water vapor molecules because of its hydrophobic nature, so the water vapor permeability remained constant. Increasing the HPMC content in the emulsion films increased the swelling and decreased the transparency. The entrapment of HPMC in continuous gelatin phase decreased its solubility. Therefore, W/W emulsions are capable of holding two incompatible polymers alongside each other within a homogeneous film network without weakening the physical properties.