Investigation On Coix Seed Oil Liposomes

As a new technology for preparating nano-capsule, liposome technology had a unique advantage in improving the solubility of fat-soluble nutrients; as a targeted drug delivery system, liposomes could be able to delivery drugs to the target site. Coix seed oil(CSO) had the physiological activity functions of enhancing body's immunity, anti-tumor and many others. The content of unsaturated fatty acid was more than 80 percent in CSO, which was extremely susceptible to oxidation, thus reducing its nutritional and biological functions. This paper aimed at studying the preparation of CSO liposomes with ethanol injection-sonication method, evaluating the quality and stability of liposomes before and after homogenization, and preparing CSO proliposomes with the freeze-drying technology; while liposomes'property and release in vitro were investigated.Egg phosphatidylcholine(EPC) and soybean phosphatidylcholine (SPC) were chosen as leading wall material to prepare liposomes, comparative analysis were done with encapsulation efficiency, particle size and appearance before and after one day at room temperature as indexes. The results indicated that encapsulation efficiency, particle size and appearance of CSO liposomes with EPC as leading wall material were better than those of CSO liposomes with SPC. The preparation techniques and formulation were optimized with encapsulation efficiency as criteria by orthogonal array design. The optimum conditions of CSO liposomes were as follows:hydration temperature 45℃, ethanol volume 2.0 ml, hydration time 20 min, ultrasonic intensity 90%; the concentration of EPC was 20 mg/ml, EPC/CSO /cholesterol (3:2:1) with phosphate buffer solution (pH6.7,50 ml) as hydration media. Under optimum conditions, the encapsulation efficiency and mean particle size of CSO liposomes was 76.34% and 207.4 nm, respectively.CSO liposomes was homogenized with 35 Mpa, the liposomes before and after homogenization were assessed according to quality evaluation and stability, and stability was investigated with appearance, T500nm, pH value, malondialdehyde(MDA) content and retention rate as the indexes. The results indicated that encapsulation efficiency of CSO liposomes before and after homogenization were both 70～80%; the suspension was a uniform milky, while the suspension of blank liposomes as control was transparent and uniform; CSO liposomes before and after homogenization both were uniform and round, mean particle size was 207.4 nm and 198.9 nm, and Zeta potential was -36.43 mV and -27.25 mV, respectively. The stability of bilayer structure was closely related to storage temperature, the optimal storage condition was light-avoiding at 4℃, but the stability decreased after homogenization.Polyethlene glycol with the molecular weight of 4000(PEG4000) was selected as the optimal cryoprotectant to prepared CSO proliposomes.CSO proliposomes prepared with the mass ratio of PEG4000 to EPC of 4:1 looked full, compact, smooth and color uniform, the encapsulation efficiency reached 48.57% after rehydration with distilled water at 25℃, its retention rate was higher than 80.25%; mean particle size of liposomes before freeze-drying and after rehydration was 260.6 nm and 286.2 nm, respectively.The characteristics of CSO proliposomes were investigated, the proliposomes observed by scanning electron microscope (SEM) were uniform, round and relatively smooth with structural integrity; DSC analysis indicated that the main phase transition temperatures of CSO proliposomes with and without PEG4000 were 82.76℃and 77.02℃, the phase transition temperature of proliposomes with PEG4000 was decreased; X-ray analysis showed that the blank proliposomes, CSO proliposomes with and without PEG4000 had the same characteristic diffraction peaks, just differed a little in peak intensity; Fourier Transform Infrared Spectroscopy (FTIR) indicated that PEG and the polar head group of EPC interacted and hydrogen bonds created, which was consistent with water-replacement hypothesis.Release of CSO from samples, which included dissolved CSO, CSO liposomes PEG4000-coated CSO liposomes was investigated in vitro. Cumulative release curves of liposomes showed significant slow releasing, long-acting effects of PEG4000-coated CSO liposomes was more evident. The release rule of liposomes in vitro was subject to Higuchi equation, while the release rule of dissolved CSO in vitro was subject to the first order equation.