Weilin Liu

Characterization and high-pressure microfluidization-induced activation of polyphenoloxidase from Chinese pear (Pyrus pyrifolia Nakai).

Polyphenoloxidase (PPO) from Chinese pear ( Pyrus pyrifolia Nakai) was characterized using catechol as a substrate. PPO had a V(max) of 289.2 units/min and a K(m) of 3.8 mmol/L, which indicates that P. pyrifolia Nakai PPO has a great affinity for catechol. The catalyzing reaction velocity was proportional to the PPO concentration. The optimum pH and temperature for PPO activity were 4.5 and 45 degrees C, respectively. In addition, an investigation was made on the effect of high-pressure microfluidization of treatment pressure, treatment pass, and enzyme solution temperature on P. pyrifolia Nakai PPO. As the treatment pressure increased, the PPO relative activity was elevated from 100% untreated to 182.57% treated at 180 MPa. PPO relative activity was enhanced as the treatment pass increased. PPO solution temperature (25, 35, and 45 degrees C) had a significant effect on PPO relative activity when treated at 120 and 140 MPa.

Storage stability and skin permeation of vitamin C liposomes improved by pectin coating

A transdermal drug delivery system was prepared by high methoxyl pectin (HMP) or low methoxyl pectin (LMP) coated vitamin C liposomes. HMP coated vitamin C liposomes (HMP-L) and LMP coated vitamin C liposomes (LMP-L) exhibited an increase in average diameter (from 66.9 nm to 117.3 nm and 129.6 nm, respectively), a decrease in zeta potential (from -2.3 mV to -23.9 mV and -35.5 mV, respectively), and a similar entrapment efficiency (48.3-50.1%). Morphology and FTIR analysis confirmed that pectin was successfully coated on the surface of vitamin C liposomes mainly through the hydrogen bonding interactions. Besides, HMP-L and LMP-L exhibited an obvious improvement in storage stability, with lower aggregation, oxidation of lipid and leakage ratio of vitamin C from liposomes, and LMP-L showed better physicochemical stability than HMP-L. Moreover, skin permeation of vitamin C was improved 1.7-fold for HMP-L and 2.1-fold for LMP-L after 24 h, respectively, compared with vitamin C nanoliposomes. Therefore, this study suggested that pectin coated liposomes, especially the LMP-L, could be a promising transdermal drug delivery system with better storage stability and skin permeation.

Improved Physical and in Vitro Digestion Stability of a Polyelectrolyte Delivery System Based on Layer-by-Layer Self-Assembly Alginate–Chitosan-Coated Nanoliposomes

To improve lipid membrane stability and prevent leakage of encapsulated food ingredients, a polyelectrolyte delivery system (PDS) based on sodium alginate (AL) and chitosan (CH) coated on the surface of nanoliposomes (NLs) has been prepared and optimized using a layer-by-layer self-assembly deposition technique. Morphology and FTIR observation confirmed PDS has been successfully coated by polymers. Physical stability studies (pH and heat treatment) indicated that the outer-layer polymers could protect the core (NLs) from damage, and PDS showed more intact structure than NLs. Further enzymic digestion stability studies (particle size, surface charge, free fatty acid, and model functional component release) demonstrated that PDS could better resist lipolytic degradation and facilitate a lower level of encapsulated component release in simulated gastrointestinal conditions. This work suggested that deposition of polyelectrolyte on the surface of NLs can stabilize liposomal structure, and PDS could be developed as a formulation for delivering functional food ingredients in the gastrointestinal tract.

Characterization and Bioavailability of Tea Polyphenol Nanoliposome Prepared by Combining an Ethanol Injection Method with Dynamic High-Pressure Microfluidization

Tea polyphenols are major polyphenolic substances found in green tea with various biological activities. To overcome their instability toward oxygen and alkaline environments, tea polyphenol nanoliposome (TPN) was prepared by combining an ethanol injection method with dynamic high-pressure microfluidization. Good physicochemical characterizations (entrapment efficiency = 78.5%, particle size = 66.8 nm, polydispersity index = 0.213, and zeta potential = -6.16 mv) of TPN were observed. Compared with tea polyphenol solution, TPN showed equivalent antioxidant activities, indicated by equal DPPH free radical scavenging and slightly lower ferric reducing activities and lower inhibitions against Staphylococcus aureus , Escerhichia coli , Salmonella typhimurium , and Listeria monocytogenes . In addition, a relatively good sustained release property was observed in TPN, with only 29.8% tea polyphenols released from nanoliposome after 24 h of incubation. Moreover, TPN improved the stability of tea polyphenol in alkaline solution. This study expects to provide theories and practice guides for further applications of TPN.

Characterization and Bioavailability of Vitamin C Nanoliposomes Prepared by Film Evaporation-Dynamic High Pressure Microfluidization

Vitamin C nanoliposomes were prepared by combining a conventional method (film evaporation) with dynamic high pressure microfluidization. Their physicochemical characterizations (antioxidant activity, particle size, entrapment efficiency, morphology, in vitro drug release, and storage stability) and skin permeation behavior were investigated. The results showed that vitamin C nanoliposomes, having equivalent DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging capacity of pure vitamin C solution without loss of their biological activity, exhibited better storage stability at 37°C for 24 hours and at 4°C for 60 days, a more excellent sustained drug release as well as higher skin penetration rate than vitamin C liposomes.

Medium-chain fatty acid nanoliposomes suppress body fat accumulation in mice

Medium-chain fatty acids (MCFA) are widely used in diets for patients with obesity. To develop a delivery system for suppressing dietary fat accumulation into adipose tissue, MCFA were encapsulated in nanoliposomes (NL), which can overcome the drawbacks of MCFA and keep their properties unchanged. In the present study, crude liposomes were first produced by the thin-layer dispersion method, and then dynamic high-pressure microfluidisation (DHPM) and DHPM combined with freeze-thawing methods were used to prepare MCFA NL (NL-1 and NL-2, respectively). NL-1 exhibited smaller average size (77.6 (SD 4.3) nm), higher zeta potential (- 40.8 (SD 1.7) mV) and entrapment efficiency (73.3 (SD 16.1) %) and better stability, while NL-2 showed narrower distribution (polydispersion index 0.193 (SD 0.016)). The body fat reduction property of NL-1 and NL-2 were evaluated by short-term (2 weeks) and long-term (6 weeks) experiments of mice. In contrast to the MCFA group, the NL groups had overcome the poor palatability of MCFA because the normal diet of mice was maintained. The body fat and total cholesterol (TCH) of NL-1 (1.54 (SD 0.30) g, P = 0.039 and 2.33 (SD 0.44) mmol/l, P = 0.021, respectively) and NL-2 (1.58 (SD 0.69) g, P = 0.041 and 2.29 (SD 0.38) mmol/l, P = 0.015, respectively) significantly decreased when compared with the control group (2.11 (SD 0.82) g and 2.99 (SD 0.48) mmol/l, respectively). The TAG concentration of the NL-1 group (0.55 (SD 0.14) mmol/l) was remarkably lower (P = 0.045) than the control group (0.94 (SD 0.37) mmol/l). No significant difference in weight and fat gain, TCH and TAG was detected between the MCFA NL and MCFA groups. Therefore, MCFA NL could be potential nutritional candidates for obesity to suppress body fat accumulation.

Preparation and Characterization of Nanoscale Complex Liposomes Containing Medium-Chain Fatty Acids and Vitamin C

Complex liposomes containing both a hydrophilic drug vitamin C and hydrophobic drug medium-chain fatty acids were prepared by double emulsion method and double emulsion-dynamic high pressure microfluidization, respectively. The results showed that the complex nanoliposomes (medium-chain fatty acids-vitamin C nanoliposomes) prepared by double emulsion-dynamic high pressure microfluidization exhibited higher entrapment efficiency of medium-chain fatty acids (48.66 ± 2.59)%, relatively higher entrapment efficiency of vitamin C (64.00 ± 5.27)%, lower average size diameter (92.8 ± 6.85) nm, and better storage stability at 4°C for 90 days than those prepared by double emulsion. In vitro drug release studies of medium-chain fatty acids-vitamin C nanoliposomes prepared by double emulsion-dynamic high pressure microfluidization were also investigated. Prolonged drug releases of medium-chain fatty acids-vitamin C nanoliposomes were observed compared with liposomes encapsulating one drug (medium-chain fatty acids or vitamin C) over a period of 24 h. It was indicated that double emulsion-dynamic high pressure microfluidization could be a potential approach in the preparation of nanoscale complex liposomes encapsulating both a hydrophilic drug and hydrophobic drug.

Preparation and characterization of medium-chain fatty acid liposomes by lyophilization

In this study, medium-chain fatty acid (MCFA) liposomes were prepared by the film ultrasonic dispersion, modified ethanol injection, and reverse-phase evaporate methods. The results indicated that the liposomes prepared by the thin-film ultrasonic dispersion method had a high entrapment efficiency of 82.7% and a good distribution in size diameters. The MCFA liposomes were freeze-dried and the optimal preparation conditions of freeze-drying were as follows: The cryoprotectants were mannitol and sucrose (1:1 w/w), the hydrated medium was distilled water, and the freeze-drying time was 48 hours. Under these conditions, the freeze-dried MCFA liposomes had a perfect appearance, a small particle size, and high encapsulation efficiency. The mean diameters were 251.1 and 265.3 nm, and the encapsulation efficiencies were 80.5 and 79.2% for freshly prepared and reconstituted liposomes, respectively.

Preparation and evaluation of easy energy supply property of medium-chain fatty acids liposomes

To develop an easy-energy-supply agent, medium-chain fatty acids (MCFAs) liposomes were prepared by thin-layer dispersion, freeze-thawing and dynamic high pressure microfluidization (DHPM)-freeze-thawing methods. Results showed that MCFAs nanoliposomes obtained by the novel method (DHPM-freeze-thawing) exhibited a smaller size (72.6 ± 4.9 nm), narrower size distribution (PDI = 0.175 ± 0.005), higher zeta potential (−41.27 ± 1.16 mV) and entrapment efficiency (45.9 ± 6.0%) compared to the other two methods. In the weight-loaded swimming test of the mice, the high-dose group of MCFAs nanoliposomes indicated a significantly longer swimming time (105 ± 31 min, p < 0.05), a lower serum urea nitrogen (839.5 ± 111.9 mg/L, p < 0.05) and blood lactic acid (5.7 ± 1.0 mmol/L, p ≤ 0.001), and a higher hepatic glycogen (15.0 ± 3.6 mg/g, p ≤ 0.001) than those of the control group (53 ± 13 min, 1153.6 ± 102.5 mg/L, 12.5 ± 1.9 mmol/L and 8.8 ± 3.3 mg/g, respectively). However, no significant difference was found between the high-dose group and MCFAs group. The results suggested that MCFAs nanoliposomes could be used as a potential easy-energy-supply agent.