Colloidal carriers

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. 

Nanoparticles have been studied extensively as carriers for drugs employed in a wide variety of routes of administration, including parenteral [14], ocular [15], and peroral [16] pathways. The term nanoparticle is a collective name for any colloidal carrier of submicrometer dimension and includes nanospheres, nanocapsules, and liposomes. They can all be defined as solid carriers, approximately spherical and ranging in size from 10 to 1000 nm. They are generally polymeric in nature (synthetic or natural) and can be biodegradable... 

The physicochemical characterization of a colloidal carrier is necessary because important characteristics, such as particle size, hydrophobicity, and surface charge, determine the biodistribution after administration [129-132]. Preparation conditions, such as the pH of the polymerization medium, monomer concentration, and surfactant concentration, can influence the physicochemical characteristics of the particles [60, 62, 64]. It is, therefore, essential to perform a comprehensive physicochemical characterization of nanoparticles, which has been reviewed by Magenheim and Benita [133]. 

Drug release can be defined as the fraction of drug released from the nanoparticulate system as a function of time after the system has been administered [203]. The release of drug from nanoparticles depends on the location and physical state of the drug loaded into the colloidal carrier [133]. The drug can be released by ... 

R. H. Muller, Colloidal Carriers for Controlled Drug Delivery and Targeting Modification, Characterisation and In Vivo Distribution. CRC Press, Stuttgart, 1991. 

Lambert G, Fattal E, Pinto-Alphandary H, Gulik A, Couvreur P. Polyisobutylcyanoacrylate nanocapsules containing an aqueous core as a novel colloidal carrier for the delivery of oligonucleotides. Pharm Res 2000 17 707-714. 

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. 

C., Nakache, E., Sanchez, C., Schmitt, C. (2002). Biopolymeric colloidal carriers for encapsulation or controlled release applications. International Journal of Pharmaceutics, 242, 163-166. 

It would lie far beyond the aim of this chapter to introduce the state-of-the art concepts that have been developed to quantify the influence of colloids on transport and reaction of chemicals in an aquifer. Instead, a few effects will be discussed on a purely qualitative level. In general, the presence of colloidal particles, like dissolved organic matter (DOM), enhances the transport of chemicals in groundwater. Figure 25.8 gives a conceptual view of the relevant interaction mechanisms of colloids in saturated porous media. A simple model consists of just three phases, the dissolved (aqueous) phase, the colloid (carrier) phase, and the solid matrix (stationary) phase. The distribution of a chemical between the phases can be, as first step, described by an equilibrium relation as introduced in Section 23.2 to discuss the effect of colloids on the fate of polychlorinated biphenyls (PCBs) in Lake Superior (see Table 23.5). 

Reactions catalyzed by solid bases were obvious candidates for testing hypotheses on the nature and the mode of action of enzymes. Bredig [40] used aminated cellulose (B2) as a model because an enzyme was thought to consist of "a specific active function and a colloidal carrier". Indeed, cyanohydrin 40 was formed with an enantiomeric excess of 22% Fig. 3 and Table 3 contain a summary of the reported results for base-catalyzed reactions. It is not clear whether the ZnO/ffuctose catalyst (Bl) described by Erlenmeyer [39] is really heterogeneous but it is the first report on using sugars as modifiers. Some reactions are probably just curiosities (39, 41), but two... 

Ilium, L., Davis, S. S., Muller, R. H., Mak, E., and V fest, P. (1987) The organ distribution and circulation time of intravenously injected colloidal carriers sterically stabilized with a block copolymer-polyoxamine 908,Life Sci., 40 367-374. 

De Campos, A.M., et al. 2003. The effect of a PEG versus a chitosan coating on the interaction of drug colloidal carriers with the ocular mucosa. Eur J Pharm Sci 20 73. 

Aspirin, paracetamol, and hydrocortisone are used to control febrile reactions of amphotericin. Patients with a history of adverse effects with amphotericin should be prophylactically treated with antipyretics and hydrocortisone. Antiemetics and pethidine also are used for the treatment of adverse effects of amphotericin. With sodium supplements and hydration therapy, damage to the kidney can be reduced. If conventional amphotericin is not well tolerated by the patient, colloidal carriers can be used as alternative options. Administration of amphotericin with a nephrotoxic drug, such as cyclosporin, may further increase toxicity. Diuretics and anticancer drugs should be avoided with amphotericin. 

This classification is sometimes rather arbitrary, as some soluble carriers are large enough to enter the colloidal size range. Another useful distinction is that with macromolecular carrier systems the drag is covalently attached to the carrier and has to be released through a chemical reaction. In contrast, with colloidal carriers, the drag is generally physically associated and does not need a chemical reaction to be... 

Much effort is also currently being expended on the development of novel drag delivery systems for pulmonary drag delivery. By employing a colloidal carrier in which drag is dispersed, it is possible to control ... 

Nanoparticles as colloidal carriers mainly depend on the particle size distribution, surface charge, and hydrophilicity. These physicochemical properties affect not only drug loading and release, but also the interaction of these particulate carriers with biological membranes. 

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