Passive physical targeting

Passive physical targeting, such as techniques that exploit the presence of leaky vasculature, are of particular interest from the standpoint of the current discussion (see the following chapter). The spontaneous... 

Artificial organs that perform the physical and biochemical functions of the heart, hver, pancreas, or lung are one class of organ replacements. A rather different target of opportunity is the development of biologieal materials that play a more passive role in the body for example,... 

Polymeric micelles are mostly small (10-100 nm) in size and dmgs can be incorporated by chemical conjugation or physical entrapment. For efficient delivery activity, they shonld maintain their integrity for a sufficient amount of time after injection into the body. Most of the experience with polymeric micelles has been obtained in the field of passive targeting of anticancer drugs to tumours [33]. Attachment of antibodies or sugars, or introduction of a polymer sensitive to variation in temperature or pH has also been stndied [32]. 

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. 

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