Stabilization of liposomes

Crommelin, D. J. A. (1984). Influence of lipid composition and ionic strength on the physical stability of liposomes, J. Pharm. Sci.. 73, 1559-1563. 

Stability of liposomes on storage, in Targeting of Drugs with Synthetic Systems (G. Gregoriadis, J. Senior, and G. 

Influence of freezing and freeze drying on the stability of liposomes dispersed in aqueous media. Acta Pharmaceut. Technol.. 34. 129-139. 

The fate of injected liposomes is drastically altered by administration route, dose and size, lipid composition, surface modification, and encapsulated drugs. Liposomes encapsulating drugs are often administered iv, therefore, the stability of liposomes in plasma is important. When liposomes composed of PC with unsaturated fatty acyl chains are incubated in the presence of serum, an efflux of internal solute from the liposomes is observed. This increase in permeability is caused by the transfer of phospholipids to high density lipoprotein (HDL) in serum (55). To reduce the efflux of liposomal contents, cholesterol is added as a liposomal component... 

Hara, M., H. Yuan, Q. Yang, T. Hoshino, A. Yokoyama, and J. Miyake. 1999. Stabilization of liposomal membranes by thermozeaxanthins Carotenoid-glucoside esters. Biochim. Biophys. Acta 1461 147-154. 

Barenholz Y, Amselem S, Goren D, et al. Stability of liposomal-doxorubicin formulation problems and prospects. Med Res Rev 1993 13 449-491. 

Grit M, Crommelin DJ. Chemical stability of liposomes implications for their physical stability. Chem Phys Lipids 1993 64 3. 

Sherwood RL, McCormick DL, Zheng S, et al. Influence of steric stabilization of liposome-encapsulated hemoglobin on Listeria monocytogenes host defense. Artif Cells Blood Substit Immobil Biotechnol 1995 23 665. 

Figure 7 The stability of liposomal VCR in liposomes prepared using different triethylammonium ion gradients. VCR can be deformylated under acidic conditions, similar to those found in the intraliposomal lumen of remote-loaded liposomes. (A) The deformylated product is inactive compared to the parent drug. (B) HPLC chromatograms show peaks for both VCR (rt = 9.5 minutes) and deformylated VCR (rt= 11.1 minutes) for liposomes prepared with either sulfate or citrate as the intraliposomal trapping agent and stored for three months at 4°C to 6°C. Abbreviation VCR, vincristine.

Hernandez-Caselles, T., Villalain, J., and Gomez-Fernadez, J. C. (1990). Stability of liposomes on long term storageJ. Pharm. Pharmacol., 42, 397-400. 

Most recently, Zhan and Bard used submicrometer-sized conical carbon fiber tips to approach, image, and puncture individual giant liposomes containing [Ru(bpy)3]2+ [36]. The leakage of [Ru(bpy)3]2+ through the lipid membrane was observed. A higher stability of liposomes as compared to lipid bilayers... 

Surface Charge of Liposomes The electrical properties of liposomal surfaces can influence the physical stability of liposomal dispersions during storage as well as the behavior of liposomes in the biological milieu and their interaction with cells [47,81],... 

Cholesterol and a-tocopherol are used quite often to increase the rigidity and stability of liposomal membranes [88,106-108]. In most cases cholesterol appears to improve the encapsulation of both hydrophilic and hydrophobic compounds. However, if the drug is lipophilic and partitions in the liposome membrane, there is a good chance that it might be displaced by adding increasing amounts of cholesterol in the bilayer (as observed in the case of dexamethasone encapsulating liposomes in our laboratory). 

Stability of Liposomes A shelf life of at least two years is requested for pharmaceutical products. Therefore, chemical stability and physical stability are important parameters for the overall performance of liposomal formulations. Additionaly, another very important factor is the retention of encapsulated drug. 

The physical stability of liposome dispersions is mainly related with possible aggregation and leakage of the liposomal membrane. The size and surface charge play a significant role for the stability of liposomal dispersions, as has been discussed in the previous paragraph. 

As mentioned above, the ability to adsorb to the cornea and an optimal drug release rate have been defined as the two liposomal attributes most responsible for increasing bioavailability after topical ocular administration. A number of factors, including drug encapsulation efficiency, liposome size and charge, distribution of the drug within liposomes, stability of liposomes in the conjunctival sac and ocular tissues, their retention in the conjunctival sac, and most importantly their affinity toward the corneal surface and the rate of release of the encapsulated drug, have... 

Arien, A., Coigoux, C., Baquey, C., and Dupuy, B. (1993), Study of in vitro and in vivo stability of liposomes loading with calcitonin or indium in GIT, Life Sci., 53, 1279-1290. 

Grit, M., and Crommelin, D. J. A. (1993), Chemical stability of liposomes Implications for their stability, Chem. Phys. Lipids, 64, 3-18. 

Taira, M. C., Chiaramoni, N. S., Pecuch, K. M., and Alonso-Romanowski, S. (2004), Stability of liposomal formulations in physiological conditions for oral drug delivery, Drug Deliv., 11,123-128. 

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