Cell—target system interaction

Special emphasis is placed on the carbohydrate-mediated cell - target system interaction by describing hints and pitfalls of assays for cytoadhesion, specificity, cytoinvasion, and cytoevasion. In addition, basic considerations are presented to discriminate between active and passive uptake as well as to detect lysosomal accumulation. Finally, the pros and cons of two useful analytical techniques, namely, flow cytometry and confocal laser scanning microscopy, are described in detail. 

Reliable statistical calculation of the data is performed by the cytometer s software, resulting in a simple evaluation of the association assays performed to characterize the interaction between targeted systems and the cells. The individual cell populations are usually described by the relative mean, either arithmetic or geometric, and the coefficient of variation of a particular parameter, as well as the number of cells within the respective population. 

Integrins are widely expressed cell surface receptors involved in cell-cell adhesion and interactions of cells with the extracellular matrix. Integrins enable the cellular uptake of structures as large as bacteria and as small as viruses. Thus, they constitute good targets for developing selective gene delivery systems. 

However, if a delivery system is to be targeted to other cell types, its interaction with the MPS must be minimized. The standard approach is to coat the surface of the system with hydrophilic materials to reduce opsonin adsorption. A number of biological31 and synthetic materials32... 

In applying this system, a biotinylated binding molecule (e.g., antigen, primary or secondary antibody) is allowed to interact with a target system (cells, microtiter plates, and so on). By uang an appropriate avidin-conju-gated probe (e.g., fluorescent or electron-dense marker, solid support, enzyme), the system can be used for a variety of different applications. 

Fig. 27.5. Mesoporous silica nanoparticles as novel drug delivery systems, (a) Cocondensation method to form functionalized mesoporous silica structures in a surfactant template synthesis, (b) TEM image of mesoporous silica nanoparticles and sketch of a novel drug delivery particle which contains functionalized pores, closed by a gate, and is decorated with ligands for cell targeting, (c) Cell targeting by ligand-receptor interaction at the cell membrane, endosomal uptake and controlled release after pH change from early to late endosome...

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