Date

2015

Author

Güner, Selen

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Liposomes are double-layered spherical vesicles made up of polar lipids and could be used in pharmaceutical, personal care, chemical and food industries to encapsulate both hydrophobic and hydrophilic compounds. Being biodegradable, biocompatible not having any toxic effects and having the ability to release the active agents when desired make these systems advantageous for many applications. The main natural sources used for liposome formation are egg and soy. In this study, egg and soy lecithin with higher purity (>70%) were used to determine the effect of different mechanical formation methods on the characterization of liposomes. Microfluidization and ultrasonic probe methods were used. Effects of microfluidization pressure, ultrasound time, and solvent type on particle size, and zeta potential were investigated. Trials were conducted between 400-1300 bars for microfluidization, 2-8 minutes for ultrasound in phosphate buffer (pH≈7.2), distilled water (pH≈6.5), and acetate buffer (pH≈3.8) solvents. Effect of solvent type on particle size was found significant (p<0.05) while phosphate buffer samples were inefficient to form liposome since presence of ions drastically decreased zeta potential of the particles. When microfluidization and ultrasonication methods were compared, microfluidization was better to decrease particle size. Increasing ultrasonication time did not significantly affect particle size after 5 minutes (p≥0.05). For the long term stability, the samples were stored at refrigerator (4°C) and room temperatures (25°C) and NMR T2 Relaxometry experiments were conducted during storage. Storing at room temperature adversely affected liposome stability which were detected by both particle size and T2 (spin spin relaxation time) values. Increase in T2 (spin spin relaxation time) values after some time during storage is validated to be a sign for liposome degradation with time. In addition to high correlation with particle size results, T2 values were promising for further characterization of liposome system, where chemical changes like lipid oxidation cannot be detected by particle size measurement.

Subject Keywords

Liposomes., Food, Food, Nuclear magnetic resonance.

URI

http://etd.lib.metu.edu.tr/upload/12619717/index.pdf
https://hdl.handle.net/11511/25404

Collections

Graduate School of Natural and Applied Sciences, Thesis