Passive target properties

Conventional liposomes are those that do not carry any sterically stabilizing or targeting moieties on their surface. Their biodistribution depends strongly on their physicochemical properties (size, potential, composition) and physiological and pathological conditions of the body [193], Thus, conventional liposomes comprise the passive targeting of drug molecules. 

Passive targeting is defined as a method whereby the physical and chemical properties of carrier systems increase the target/non-target ratio of a quantity of a delivered drug. Biodistribution and the pharmacokinetic behaviors of polymeric micelles are determined by the micelles size and surface properties (e.g., charge, hydrophilicity, or hydrophobicity). 

Polymeric nanoparticles of different physical characteristics such as size, size distribution, morphology and zeta potential (charge) can be synthesized by controlling the parameters specific to the synthesis method employed. There are several techniques potentially useful for the preparation of polymeric nanoparticles. The selected method determines the characteristics of spheres, including the size, because it is one of the most important properties strongly related to mode of administration as well as passive targeting. Another property influenced by the preparation process is the ability to interact with active principles contained in the drugs formulation. 

It is one thing to design micelles with targeted properties and behavior yet another to evidence their in vitro and in vivo applicability. To our benefit, there are numerous instances where the formulation of drugs as PM reduced their cytotoxity, increased the maximum tolerated dose (MTD) or permitted passive accumulation at target sites while accounting for improved therapeutic effects compared to control formulations. Some PM and PICM systems are summarized in Tables 4.3 and 4.4, respectively, and their performance discussed below. 

Conventional liposomes are typically composed of only phospholipids and/or cholesterol. This first generation of liposomes is generally used for passive targeting they tend to be phagocytosed by the cells of the mononuclear phagocyte system (MPS) and therefore accumulate in organs such as the liver and the spleen. Based on this property, a conventional liposome formulation of the antifungal dmg amphotericin B (initially marketed under the name... 

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