Abstract
Polymeric surfaces in contact with blood in vivo are foreign bodies and are quickly isolated from blood by the non-specific defense systems. Nanoparticles (NP) used as drug carriers are normally quickly taken up by phagocytes and sequestered in liver and spleen to which they can deliver drugs. Long-circulating and/or low complement activating core-shell NPs can be obtained from PEO/PEG amphiphilic copolymers forming brush or loops on the surface. Core-shell NPs can also be obtained from polysaccharidic graft or block amphiphilic copolymers. Complement activation by the NPs and protein adsorption both depend on the structure, nature and molecular weight of the polysaccharide chains composing the shell. NPs showing low complement activation can be obtained if the polysaccharide on the surface is long and in a brush configuration. Fragile molecules such as hemoglobin or siRNA can be loaded and protected by appropriate brush shells without modifying the low complement activation properties.
Highlights
When a material is introduced into a living organism and is exposed to circulating blood, its surface is quickly covered with proteins
NPs obtained from block copolymers polylactides-block-poly(ethylene oxide) methyl ether (PLA-PEO) were able to circulate in the bloodstream for several hours [9,10]
In order to understand the reasons of these apparent inconsistencies, we investigated the polymers obtained by reactions of polymerization of IBCA initiated by dextran or other polysaccharides in the presence or absence of Ce(IV) ions in acidic aqueous medium
Summary
When a material is introduced into a living organism and is exposed to circulating blood, its surface is quickly covered with proteins. Polymers 2012, 4 embolisation injected via a catheter are designed to intentionally block vessels These particles are covered by a clot which isolates the material from direct blood contact. Sub-micronic particles, i.e., nanoparticles (NP), which, as a result of their small size, may be able to circulate, are rapidly taken up by phagocytic cells. In contrast to macromolecules of natural origin which can induce an immunogenic response, synthetic polymeric materials are usually not recognized as antigenic per se Such materials are foreign bodies which have to be quickly removed from the blood by the action of non-specific defense systems. The activated phagocytes are able to adhere to the tagged surface and start to engulf the foreign body by phagocytosis. Complement activation and deposition of other proteins can be modulated by changing the nature and structure of the hydrogel covering the surface
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