Opsonization process

When administered into the bloodstream, colloidal panicles normally become opsonized with various blood components. Through the nature and the amount of this opsonization process such systems will be recognized as foreign very rapidly and will be removed by the various eleineiits of the RES. 

PEG)-modified phospholipids provides a hydrophilic shell that surrounds the lipophilic core and creates a steric barrier. PEG derivatives were shown to prevent serum protein binding, to reduce phagocytotic cell-mediated recognition, and to result in increased circulation lifetimes (18). Polyglycerolated phospholipids are said to inhere a similar potential of reducing opsonization processes while showing reduced toxicity (19). 

Surface hydrophobicity. Serum components adsorb on the surface of colloidal particles via their hydrophobic sites. An increase in surface hydrophobicity increases opsonization. To reduce opsonization, a predomincmtly hydrophilic surface is required. This led to the conclusion that adsorption of poly(ethylene glycol (PEG) type block copolymers on the surface of the particles should reduce the opsonization process. This will be discussed in the next section. 

It has the ability to cross the placenta and therefore provides a major line of defence against infection for the newborn. This can be reinforced by transfer ofcolostral IgG across the gut mucosa of the neonate. It diffuses readily into the extravascular spaces where it can act in the neutralization of bacterial toxins and can bind to microorganisms enhancing the process of phagocytosis (opsonization). This is due to the presence on the phagocytic cell surface of a receptor for Fc. 

Opsonization The process by which an antigen is altered so as to become more readily and more efficiently engulfed by phagocytes. 

The exact mechanism responsible for the uptake of liposomes by KCs and SECs is not clear. Most studies confirm internalization of whole liposomes in an energy-dependent phagocytic process in which the liposomes are delivered to the lysosomes. The liposomal lipids are completely degraded and the encapsulated solutes released. Neutral liposomes consisting of lipids such as cholesterol and phosphatidylcholine are probably cleared by receptor-mediated mechanisms, due to the adsorption of opsonizing proteins onto the hpid bi-... 

Particles introduced into the bloodstream are covered rapidly by components of the circulation, such as plasma proteins, in a process called opsonization. Opsonization makes the particles recognizable to the body s major defense system, the reticuloendothelial system (RES). The RES comprises a diffuse system of phagocytic cells (which engulf inert material) that are primarily associated with the connective tissues in the liver, spleen, and lymph nodes. Macrophage (Kupffer) cells in the liver and macrophages of the spleen and circulation are important in removing particles identified by opsonization. A significant fraction of nanoparticles can be cleared from the circulation system in as little as 15 minutes [48, 49],... 

Adsorption the drug/particulate adsorbs to the phagocytic cell surface. This process may be facilitated by serum proteins knows as opsonins, which cover the particulate and promote adsorption and ingestion. The extent and pattern of opsonization depends highly on antigen surface characteristics such as charge and hydrophilicity. 

Complement proteins opsonize bacteria for phagocytosis via integrin family, a(3 het-erodimeric CRs on the macrophages. Unlike the FcR-mediated process, GR-mediated... 

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