Physicochemical mechanisms of different biopolymers' (lysozyme, gum arabic, whey protein, chitosan) adsorption on green tea extract loaded liposomes.

Having various domains of applicability, liposomes have been the issue of many studies since 1960s. Kinetically stable nature of liposomes required incorporation of other substituents to gain storage stability and interaction of liposomes with polymers, electrolytes, proteins or lipids still requires further investigation to explain the underlying mechanism. In this study, polyphenol-rich green tea extract was encapsulated into liposomes by means of microfluidization in two different aqueous media (pH = 3.8 acetate buffer and pH = 6.5 distilled water). Antioxidant loaded vesicles were further mixed with anionic biopolymers (gum arabic, whey protein) and cationic biopolymers (lysozyme, chitosan) separately. The physical and chemical interactions between liposomes and biopolymers were rationalized by particle size, zeta potential, transmission electron microscopy, total phenolic content and antioxidant activity measurements during 28-days storage at 4 °C. Experimental results indicated that the biopolymer incorporated liposomes showed better stability compared to control liposomes during storage, developing resistance against changes in particle size and zeta potential. On the other hand, biopolymer interaction mechanisms were shown to be different for different biopolymers. As was also proved by transmission electron microscopy, lysozyme was absorbed into the liposomes while gum arabic, whey protein and chitosan were adsorbed on the vesicle surface to shield green tea extract loaded liposomes.

Exploring the crystallinity of different powder sugars through solid echo and magic sandwich echo sequences.

Time-domain nuclear magnetic resonance techniques are frequently used in polymer, pharmaceutical, and food industries as they offer rapid experimentation and generally do not require any considerable preliminary sample preparation. Detection of solid and liquid fractions in a sample is possible with the free induction decay (FID). However, for the classical FID sequence that consists of a single pulse followed by relaxation decay acquisition, the dead time of the probe (ring out of resonance circuitry) occurs and varies between 5 and 15 µs for standard 10-mm tubes. In such a case, there arises a risk that the signal from the solid fraction cannot be detected correctly. To obtain quantitative measurement on crystalline and more mobile amorphous fractions, alternative sequences to the classical FID in the solid-state nuclear magnetic resonance were developed. Solid echo and magic sandwich echo sequences perform the relaxation decay refocusing somehow excluding the dead time problem and allow detection of the signal from the solid fraction. In this study, knowledge of amorphous/crystal fraction, which is obtained through solid echo and magic sandwich echo, has been explored on powder sugar samples for the purpose of developing a groundwork for a reliable quality control method. Different sugars were examined for the utilization of the sequences. What is important to add and make this study unique is that the method proposed did not involve multiparameter fitting of the "bead" pattern FID signal that normally suffers from ambiguity; just the integration of the fast Fourier transform of the solid echo was needed to calculate the second moment, (M2 ).

Dynamics of unloaded and green tea extract loaded lecithin based liposomal dispersions investigated by nuclear magnetic resonance T2 relaxation.

Liposomes are lipid bilayer vesicles that can be used as encapsulation systems for bioactive agents to provide increased protection against environmental stresses (such as pH or temperature extremes). Time Domain Nuclear Magnetic Resonance (TD-NMR) that is based on differentiation of specimen contents with respect to magnetic relaxation rates provides detailed information on amount, state and distribution of water and oil and provide reproducible results on the samples. These make TD-NMR particularly suitable for time-dependent monitoring of emulsion system dynamics. In this study, spin-spin (T2) relaxation times and relaxation spectra were used for characterizing green tea extract loaded and unloaded liposomes prepared with soy (S75) and egg lecithins (E80) by different preparation methods (such as homogenization type, pressure and solvent type). Mean particle sizes of liposomes were found to be the most influential factor in shaping mono-exponential T2 relaxation times. The differences in particle sizes of E80 and S75 samples along with samples with different homogenization pressures could be monitored with T2 relaxation times. Additionally, T2 relaxation times were found to be correlated with particle shape irregularity, and chemical instability of samples due to lipid oxidation. With relaxation spectrum analysis, particular components in the sample could be distinguished (internal/external water and lipid bilayers), which gave more elaborate results on mechanisms of instability.

Nacre-mimetic bulk lamellar composites reinforced with high aspect ratio glass flakes.

Nacre-mimetic epoxy matrix composites reinforced with readily available micron-sized high aspect ratio C-glass flakes were fabricated by a relatively simple, single-step, scalable, time, cost and man-power effective processing strategy: hot-press assisted slip casting (HASC). HASC enables the fabrication of preferentially oriented two-dimensional inorganic reinforcement-polymer matrix bulk lamellar composites with a micro-scale structure resembling the brick-and-mortar architecture of nacre. By applying the micro-scale design guideline found in nacre and optimizing the relative volume fractions of the reinforcement and the matrix as well as by anchoring the brick-and-mortar architecture, and tailoring the interface between reinforcements and the matrix via silane coupling agents, strong, stiff and tough bio-inspired nacre-mimetic bulk composites were fabricated. As a result of high shear stress transfer lengths and effective stress transfer at the interface achieved through surface functionalization of the reinforcements, fabricated bulk composites exhibited enhanced mechanical performance as compared to neat epoxy. Furthermore, governed flake pull-out mode along with a highly torturous crack path, which resulted from extensive deflection and meandering of the advancing crack around well-aligned high aspect ratio C-glass flakes, have led to high work-of-fracture values similar to nacre.