Liposomal drug release

Fig. 3.1 Schematic illustration of a targeted drug-delivery principle that involves accumulation of polymer-covered liposomal drug carriers in porous diseased tissue where secretory sPLAj subsequently acts as a local trigger for liposomal drug release and drug transport across the target cell membrane.

Effect of Temperature on Liposomal Drug Release and Absorption by SPLA2... 

Liposomal Drug Release as a Function of SPLA2 Concentration... 

J. Davidsen, K. Jorgensen, T. L. Andresen, and O.G. Mouritsen. Secreted phospholipase A2 as a new enzymatic trigger mechanism for localised liposomal drug release and absorption in diseased tissue. Biochim. Biophys. Acta,... 

A challenge in designing liposome systems is the assessment of drug release from such systems in vitro. Use of agarose gel matrices has been reported as one approach to evaluate the release kinetics of liposome-encapsulated materials in the presence of biological components [68],... 

Fattale, E. Rojas, J. Roblot-Treupal, L. Andremont, A., Couveur, P. Ampicillin-loaded liposomes and nanoparticles Comparison of drug loading, drug release and in vitro antimicrobial activity. J. Microcapsulation 8 (I), p. 29-36, 1991... 

Horowitz AT, Barenholz Y, Gabizon AA. In vitro cytotoxicity of liposome-encapsulated doxorubicin dependence on liposome composition and drug release. Biochim Biophys Acta 1992 1109 203-209. 

Andresen TL, Jensen SS, Jorgensen K. Advanced strategies in liposomal cancer therapy problems and prospects of active and tumor specific drug release. Prog Lipid Res 2005 44 68-97. 

Lim HI, Masin D, Madden TD, Bally MB. Influence of drug release characteristics on the therapeutic activity of liposomal mitoxantrone. J Pharmacol Exp Ther 1997 281 566. 

Charrois GJ, Allen TM. Drug release rate influences the pharmacokinetics, biodistribution, therapeutic activity, and toxicity of pegylated liposomal doxorubicin formulations in murine breast cancer. Biochim Biophys Acta 2004 1663(1-2) 167. 

Less frequently used at present is electron spin resonance spectroscopy, which is based on the use of spin probes as model componnds or covalent spin labeling of drugs. Microviscosity and micropolarity of the molecnlar environment of the probe can be derived from electron spin resonance spectra. Moreover, the spectra allow us to differentiate isotropic and anisotropic movements, which result from the incorporation of the probe into liposomal structures. Quantitative distribution of the spin probes between the internal lipid layer, the snrfactant, and the external water phase is to be determined noninvasively. On the basis of the chemical degradation of drugs released from the lipid compartment, agents with reductive features (e.g., ascorbic acid) allow us to measure the exchange rate of the drugs between lipophilic compartments and the water phase [27,28]. 

It is well established that size, charge, and chemical composition of liposomes affect their fate in vivo [306], To manipulate their biodistribution and/or drug release, liposomes of different structures have been prepared, including those sensitive to changes in pH [307, 308] or temperature [309,310]. Compared to soluble polymers discussed in previous chapters, liposomes, when applied i.v., are captured by a substantially greater extent by the specialized cells (macrophages) of the reticuloendothelial system (RES) [311]. The removal of liposomes from the bloodstream takes place by nonspecific endocytosis (phagocytosis) [312],... 

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