Preparation And Characterization Of Medium-Chain Fatty Acids Nanoliposome By Dynamic High Pressure Microfluidization Technology

Medium-chain fatty acids (MCFAs) possess the advantages of fast absorption, easy-energy supply and suppression of body fat accumulation. However, an excess intake of MCFAs can lead to nausea, stimulation to the secretion of cholecystokinin and gastrointestinal discomfort. As a promising biodegraded delivery system, liposomes can improve the bioavailability of drugs.MCFAs were used as modeling materials in this study and incorporated into nanoliposomes. As the main technology, dynamic high pressure microfluidization (DHPM) was combined with thin-layer dispersion and freeze-thawing methods to prepared MCFAs nanoliposomes. In addition, the physical-chemical (size, polydisperse index, zeta potential, entrapment efficiency, drug loading, morphology, DSC, leakage rate, surface tension, long-time storage stability) and biological (easy-energy supply and suppression body fat accumulation) properties were investigated.The analysis method of MCFAs in vitro was established, with the content of MCFAs 95.94% and the mass ratio between octoic acid and decoic acid 5/4. Besides, the percentage of MCFAs incorporated into liposomes was measured by gas chromatography after free drugs had been separated from liposomes by centrifugation, alkaline process methyl esterification of MCFAs and N-hexane extraction.Thin-layer dispersion-DHPM and DHPM-freeze-thawing methods were developed to prepare MCFAs nanoliposomesⅠandⅡ, respectively. Each factor was analyzed and the orthogonal test was taken to optimize the formula. The optimized formula of MCFAs nanoliposomesⅠas follows:the concentration of lipids and MCFAs were 8% and 15 mg/mL, respectively; the mass ratio between phospholipid and cholesterol was 6/1;the concentration of tween-80 was 30%; the concentration and pH of PBS were 0.05 mol/L and 7.4, respectively; the preparation temperature was 40℃; the treatment pressure and passes were 140 MPa and 4, respectively. The optimized formula of MCFAs nanoliposomesⅡas following: cryoprotectant was maltose; the dosage of cryoprotectant was 3%; the freeze-thawing cycles were 3; the freezing time was 0.5 h and thawing temperature was 40℃. Both of the precision of the two methods were good.The characteristics and qualities of both MCFAs nanoliposomesⅠandⅡwere evaluated. Compared with MCFAs nanoliposomesⅡ, MCFAs nanoliposomesⅠexhibited great advantages in their characteristics with regular spherical or elliptical in shape, a small average diameter (76.2±1.2 nm), narrow size distribution (PDI=0.207±0.003), high zeta potential (-50.51±0.4 mV), large entrapment efficiency (70.5±6.5%) and drug loading (9.4±0.4%), low surface tension (33.86±0.36 dyne/cm), high Tm (138℃), low leakage rate and good long-time storage stability.The easy-energy-supply property of these two kinds of MCFAs nanoliposomes were estimated by the relive-fatigue experiments to the mice. The high-dose groups ofⅠandⅡ(680 mg/kg) suggested a significantly longer weight-loaded swimming time (104±29 min and 105±31min, respectively) and a higher hepatic glycogen (HG) (16.40±1.45 mg/g and 14.98±3.56 mg/g, respectively) than the control group. Moreover, the serum urea nitrogen (SUN) (891.5±113.4mg/L and 839.5±111.9mg/L, respectively) and blood lactic acid (LD) (6.05±1.40mmol/L and 5.70±1.02mmol/L, respectively) of high-dose groups were also significantly lower than those of the control group. However, the MCFAs group and the two MCFAs nanoliposomes groups showed no significant difference.The suppression accumulation of body fat property of MCFAs nanoliposomesⅠandⅡwas investigated by short-term (two weeks) and long-term (five weeks) oral administration to the mice. Compared to the control group, the body weight of the mice, food intake, the adipose tissue and liver weights of the two MCFAs nanoliposomes were no significant difference. Nevertheless, the triglyceride (0.550±0.140 mmol/L and 0.384±0.150 mmol/L, respectively) and total cholesterol (0.621±0.097 and 0.540±0.247, respectively) were significantly lower than the control group. The MCFAs group and the tow MCFAs nanoliposomes groups showed no significant difference.All the results indicated that MCFAs nanoliposomes prepared by thin-layer dispersion-DHPM and freeze-thawing-DHPM methods have overcome the drawbacks of MCFAs and exhibited good physicochemical properties. The easy-energy-supply and suppression of body fat accumulation characteristics revealed the MCFAs nanoliposomes can be a potential easy-energy-supply drug candidate.