Weilin Liu

Improved in vitro digestion stability of (−)-epigallocatechin gallate through nanoliposome encapsulation

(-)-Epigallocatechin gallate (EGCG) is unstable and degraded in near-neutral or alkaline fluids. To overcome its limitation, EGCG nanoliposome (EN) was prepared by an ethanol injection method combined with dynamic high-pressure microfluidization. EN possessed good physicochemical characterizations (high entrapment efficiency=92.1%, small average particle size=71.7nm, low polydispersity index=0.286 and zeta potential=-10.81mv). EN exhibited a relative good sustained release property. Stability of EGCG in simulated intestinal fluid (SIF) was significantly improved by nanoliposome encapsulation. After 1.5h incubating in SIF without or with pancreatin, the residual EGCG of EN was 31.2% and 47.7% respectively, but the residual EGCG in EGCG solution was only 3.4% and 3.5% respectively. The degenerations of in vitro antioxidant activities of EGCG were effectively slowed by nanoliposome encapsulation. This study expects to provide theories and practice guides for further applications of EN.

Stability during in vitro digestion of lactoferrin-loaded liposomes prepared from milk fat globule membrane-derived phospholipids

Liposomes loaded with positively charged lactoferrin (LF) were prepared from milk fat globule membrane-derived phospholipids using a thin-layer dispersion method. The entrapment efficiency of LF in the liposomes and the stability during in vitro gastrointestinal digestion were characterized and examined using dynamic light scattering, transmission electron microscopy, and PAGE. The entrapment efficiency of LF encapsulated in the liposomes was about 46%. The entrapped LF remained unchanged as a function of time and pepsin concentration when the liposome samples were digested in a simulated gastric environment, suggesting that the liposomes prepared from milk fat globule membrane-derived phospholipids were stable and protected the entrapped LF from pepsin hydrolysis. In simulated intestinal fluid, the entrapped LF was more susceptible to hydrolysis by the protease in pancreatin, as shown by changes in the diameter and membrane structure of the liposomes. The release of free fatty acids from the liposomes during digestion in simulated intestinal fluid revealed that the phospholipids in the liposomes were partly hydrolyzed by pancreatic lipase. It was suggested that liposomes may prevent the gastric degradation of LF and reduce the rate of hydrolysis of LF in intestinal conditions.

Environmental stress stability of microencapsules based on liposomes decorated with chitosan and sodium alginate.

In this study, liposomes (LPs), chitosan (CH) coated LPs, sodium alginate (AL) and CH multilayered LPs (AL-CH-LPs) were developed based on the electrostatic interaction between charged polysaccharides at a certain pH. The increase of polymer layers on LPs led to a monotonic increase in size from ∼600 (LPs) to ∼1810 nm (AL-CH-LPs) and negative charge from -12.5 to -25.2 mV, regarded as a consequence of the formation of gradually expanded structures by cationic CH and anionic AL. The environmental stress including pH, storage and ionic strength (10-200 mM NaCl) had significant impact on the appearance and the particle size of the double-layered liposome (AL-CH-LPs). Furthermore, LPs showed the highest release rate of hydrophilic model ingredient (vitamin C) under gastrointestinal conditions, while the polymers had a capacity to reduce the vitamin C release in simulated intestinal fluid. This work provided useful information on the potential application of CH and AL based delivery systems.

Behaviour of liposomes loaded with bovine serum albumin during in vitro digestion.

This study examined the stability of liposomes loaded with negatively charged protein (bovine serum albumin, BSA) during in vitro digestion. Zeta-potential and morphology measurements confirmed that BSA-loaded liposomes were successfully prepared, with an encapsulation efficiency of around 34%. The encapsulated BSA and the integrity of the liposomes remained unchanged with time when the liposomes were digested in a simulated gastric environment, suggesting that the liposomal membrane protected the entrapped BSA from pepsin hydrolysis. BSA-loaded liposomes exhibited lower stability in simulated intestinal fluid, as shown by damaged membranes and the release of free fatty acids. Also, lipolysis kinetics revealed that bile salts and ionic strength could facilitate a high level of free fatty acid release. This work further supplemented our knowledge about the effects of gastrointestinal digestion conditions on liposomal properties and provided valuable information for the design of liposome formulations for the food and health care industries.

Hybrid liposomes composed of amphiphilic chitosan and phospholipid: Preparation, stability and bioavailability as a carrier for curcumin

Hybrid liposomes, composed of amphiphilic chitosan and phospholipid, were prepared and used to evaluate the effect of amphiphilic polymers on the properties of liposomes. Successful preparation of the hybrid liposomes was confirmed using physicochemical characteristics, including morphology, particle size and zeta potential. Physical stability studies (exposure to solutions of increasing ionic strength and heat treatment) indicated that the hybrid liposomes had better ionic stability than amphiphilic chitosan-based polymeric liposomes and higher thermal stability than traditional phospholipid liposomes. Curcumin was then encapsulated in the hybrid liposomes. Compared with phospholipid liposomes, the hybrid liposomes displayed better storage stability and more sustained curcumin release. Cellular uptake experiments showed that the hybrid liposomes significantly increased the bioavailability of curcumin. The study highlights the potential of well-designed stable hybrid liposomes that increase the stability and bioavailability of lipophilic bioactive, such as curcumin.

Progress in Applications of Liposomes in Food Systems

Because of their unique structures and properties, liposomes have been widely studied and successfully used as drug delivery systems in pharmaceutical and cosmetic applications. However, there have been limited developments in the application of liposomes in food and nutraceutical applications, due mainly to difficulties in finding safe, solvent-free, and low-cost ingredients, as well as low-cost production methods. In recent years, several nutraceutical products (vitamins, enzymes, herbal extracts) have been formulated using liposome technology, with the aim of improving absorption of the bioactive compound. However, the fate of these materials during digestion in the gastrointestinal tract is not fully understood. This chapter provides a brief overview of the formation, structures, and properties of liposomes. Recent progress on encapsulation of various bioactive compounds using these liposomes and the stability behavior of the liposomes as they pass through the gastrointestinal tract is reviewed and discussed.

Storage Stability and Antibacterial Activity of Eugenol Nanoliposomes Prepared by an Ethanol Injection-Dynamic High-Pressure Microfluidization Method

Eugenol is a major phenolic component with diverse biological activities. However, it is difficult to formulate into an aqueous solution due to poor water solubility, and this limits its application. In the present study, eugenol nanoliposomes (EN) were prepared by combining the ethanol injection method with the dynamic high-pressure microfluidization method. Good physicochemical characterizations of EN were obtained. The successful encapsulation of eugenol in nanoliposomes was confirmed by Fourier transform infrared spectroscopy. A good storage stability of EN was confirmed by its low variation of average particle diameter and encapsulation efficiency after 8 weeks of storage. No oil drops were found in EN after 8 weeks of storage at 4°C and at room temperature, which suggested that the poor water solubility of eugenol was overcome by nanoliposome encapsulation. Compared with that of eugenol solution, a relatively good sustained release property was observed in EN. The antibacterial activity of EN against four common foodborne pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes) was evaluated in both Luria broth and milk medium.

Kinetic stability and membrane structure of liposomes during in vitro infant intestinal digestion: Effect of cholesterol and lactoferrin

The effects of cholesterol and lactoferrin on the kinetic stability and membrane structural integrity of negatively charged liposomes under in vitro infant intestinal digestion conditions were elucidated using dynamic light scattering, pH-stat titration, Fourier transform infrared spectroscopy, and pyrene steady state fluorescence probes. The liposomes had a smaller particle diameter, a wider size distribution, and a greater negative charge after digestion. The incorporation of cholesterol into the phospholipid bilayers resulted in a more ordered conformation in the aliphatic tail region and reduced micropolarity, indicating that cholesterol can improve the structural stability of liposomal membranes against intestinal environmental stress. Lactoferrin coverage facilitated the release of free fatty acids and increased the microfluidity of the bilayers, reducing the structural integrity of the liposomes. This study provides useful information on the design of liposomes and other microcapsules with improved and controlled release properties during digestion for particular groups of people.

Comparative performances of lactoferrin-loaded liposomes under in vitro adult and infant digestion models

There remain gaps in our understanding of the fate of liposomes in the infant gastrointestinal tract, especially regarding essential proteins such as lactoferrin. Models in vitro that mirrored digestion in the stomach and intestine of infants and adults were used to explore the behaviour of lactoferrin-loaded liposomes. The liposomes behaved differently in these environments, with less hydrolysis of encapsulated lactoferrin under infant model conditions. Compared to the adult model (1000u202f±u202f66u202fμMu202fmL-1), fewer free fatty acids were released (500u202f±u202f43u202fμMu202fmL-1) from liposomal bilayers and there was less alteration in functional groups of phospholipids membranes, based on pH and FTIR after infant model digestion. Particle tracking analysis and TEM supported the reduced damage of particle structure under infant model conditions. This work provides information on the stability of functional protein-loaded liposomes during digestion, and shows the potential of liposomes to be nutrient carriers in infant foods.

Structural characterization and biological fate of lactoferrin-loaded liposomes during simulated infant digestion: In vitro infant digestion behavior of lactoferrin-loaded liposomes

BACKGROUNDnLimited information is concerned on the structure changes of liposomal delivery system under infant conditions. Positively charged lactoferrin (LF)-loaded liposomes, with the entrapment efficiency (EE) of 52.3xa0±xa06.3%, were prepared from soybean-derived phospholipids using a thin-layer dispersion method. The structure changes and digestibility of LF-loaded liposomes under infant conditions, including simulated gastric fluid (SGF) and simulated small intestinal fluid (SIF), were characterized in terms of the average particle size, zeta potential, turbidity, fourier transform infrared, transmission electron microscopy, lipolysis and protein hydrolysis.nnnRESULTSnThis study showed that the functional groups, favorable membrane structure and the EE of liposomes were slightly changed as a function of time when the liposome digested under SGF conditions. However, the intact bilayer structures were damaged and the EE of LF-loaded liposomes decreased to 28.5% after digestion in infant SIF.nnnCONCLUSIONnThese results suggested that liposomal membrane could prevent the gastric degradation and the structure of liposomes was not completely destroyed with a low concentration of pancreatin and bile salts under infant conditions. Present study provided information on the insight into the characteristics of liposomes during infant gastrointestinal digestion, which was useful for the development of microcapsule systems in infant diet.