Colloidal carrier systems

L. Ilium and S. S. Davis, Passive and active targeting using colloidal carrier systems, in Drug Targeting (P. Buri and A. Gumma, eds.), Elsevier Science Publishers, Amsterdam, 1985, p. 65. 

Liposomes and micelles are lipid vesicles composed of self-assembled amphiphilic molecules. Amphiphiles with nonpolar tails (i.e., hydrophobic chains) self-assemble into lipid bilayers, and when appropriate conditions are present, a spherical bilayer is formed. The nonpolar interior of the bilayer is shielded by the surface polar heads and an aqueous environment is contained in the interior of the sphere (Figure 10.3A). Micelles are small vesicles composed of a shell of lipid the interior of the micelle is the hydrophobic tails of the lipid molecules (Figure 10.3B). Liposomes have been the primary form of lipid-based delivery system because they contain an aqueous interior phase that can be loaded with biomacromolecules. The ability to prepare liposomes and micelles from compounds analogous to pulmonary surfactant is frequently quoted as a major advantage of liposomes over other colloidal carrier systems. 

Muller, R.H. Mehnert, W. Lucks, J.-S. Schwarz, C. Muhlen, A. Weyhers, H. Ereitas, C. Ruhl, D. Solid lipid nanoparticles (SLN)—an alternative colloidal carrier system for controlled drug delivery. Eur. J. Pharm. Biopharm. 1995, 41 ( ), 62-69. 

Zimmermann, E., Liedtke, S., Muller, R.H. and Mader, K. (1999) H-NMR as amethod to characterize colloidal carrier systems. Proc. Int. Symp. Control. Rel. Bioact. Mater. 26, 595-596. 

Getie M, Wohlrab J, and Neubert RH. (2005). Dermal delivery of desmopressin acetate using colloidal carrier systems. Journal of Pharmacy and Pharmaceutical Science, 57, 423-427. 

A. Goebel, R.H.H. Neubert, Dermal peptide delivery using colloidal carrier systems. Skin Pharmacol. Physiol. 21, 3-9 (2008)... 

Both oral and parenteral uptake of colloidal carrier systems have been found to depend on the nature of the carrier as such. In the latter case, the RES uptake of colloidal drug carriers depends on a number of factors, notably the surface properties of the carrier (see above). This is related to the adsorption of certain serum proteins (opsonins) at the carrier surface, which initiates various biological responses. For example, it is known that macrophages, major components in the RES system, have Fc receptors at their surfaces, which means that carriers with adsorbed IgG are more likely to be captured by these cells (52). By reducing the adsorption of the opsonins at the carrier surface, e.g. by surface treatment using PEO derivatives, a very low serum protein adsorption can be reached, thereby prolonging the bloodstream circulation time and obtaining a more uniform tissue distribution (see above). 

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