Reticuloendothelial-avoiding systems

Palmitic acid is conjugated to glucuronic acid to form a reticuloendothelial system-avoiding liposome delivery system (79). Phospholipids such as phosphatidyl choline or phosphatidyl ethanolamine are used as constituents of lipid complexes or... 

In plasma, the drug-carrier complex is exposed to normal clearance mechanisms by the liver, the kidney, and the reticuloendothelial system. The success of avoiding these nonspecific clearance mechanisms depends on the affinity of carriers for their target receptors and on their plasma concentrations. An excess of conjugate in plasma caused by saturation of its cellular uptake by means of the target receptors renders the conjugate present in plasma more susceptible to nonspecific removal. 

Their large size and their inherently active surfaces allow them to be loaded with substantial amounts of agent through non-covalent processes. Also owing to their size and relative structural stability, they may be "cloaked to avoid being quickly filtered by the reticuloendothelial system or otherwise degraded by environmental processes. 

The successful utilization of polymeric materials within the living body is highly dependent on the structural architecture and monomer unit distribution in the polymer. Nanoparticles with a hydrophobic surface (e.g., PLA and PLGA) are rapidly taken up by the cells of the reticuloendothelial systems (RES) [147]. Polymeric particles with a hydrophilic surface can avoid this uptake to a greater extent, thereby prolonging the lifetime in the circulation, which may help in efficient... 

Gadolinium ions are highly toxic in their hydrated form [Gd(H20)g] +. In vivo, Gd + ions compete with calcium ions and block the reticuloendothelial system. To avoid this toxicity, gadolinium is complexed with an organic thermodynamically stable matrix, (see Lanthanide Complexes with Multidentate Ligands, Organometallic Chemistry Fundamental Properties, Lanthanides Coordination Chemistry) In addition, ligands that allow coordination sites for one (or more) water molecule(s) ate preferred since they increase... 

The main problem to be overcome is their removal by phagocytic cells (macrophages) of the reticuloendothelial system (RES) and in particular the Kupffer cells of the liver. The main target of any research on nano-partides is to modify the surface of the particles in such a way to avoid RES recognition. 

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