Stealth surfaces

Apart from wettability and the related spreading of hquids, chemically heterogeneous surface composition has a profound impact on adhesion and its respective failure mechanisms and defects [24]. Further relevant areas comprise release surfaces, corrosion, lubrication, as well as chemical surface functionalization in coatings, sensors and biomedical apphcations (stealth surfaces) [18]. These important phenomena together with related appUca-tions in miniaturized devices, where the tolerances for defects and lateral heterogeneities are rapidly decreasing, are in the focus of the microscopic techniques reviewed in this article. 

Several of these problems can be solved by polyplex modification with polyethylene glycol (PEG). PEGylation has been broadly explored for surface shielding ( stealthing ) of many liposomal and nanoparticulate carriers. In the case of cationic polymers, Plank et al. [62] demonstrated that complement activation can be reduced when the polymers are PEGylated. Such a modification can be... 

Lipid moieties coupled to polyethylene glycol (PEG) have been used to increase the blood circulation time of lipoplexes (Fig. 32). The PEG-lipid conjugates such as DOPE-PEG, Chol-PEG, ceramides-PEG and their derivatives are then coformulated with the cationic lipid, helper lipid, and DNA. This results in coating the surface of the lipoplexes with PEG and preventing undesired association with plasma proteins or circulating cells (stealth liposomes). Recently, a-tocopheryl PEG-succinate (TPGS) was also used in gene delivery formulations because of its ability to confer not only a stealth property but also antioxidant and absorption enhancer properties [129]. 

PLGA microspheres can be prepared in rather narrow size ranges from 0.2 /mi up to > 100 /mi. The preparation, properties and degradation of these polymers have been discussed extensively in Chapter 4 (see Section 4.5.1). PLGA microspheres can now be prepared with surface oriented PEG-chains which improves in vivo circulation time ( stealth-effects ). 

Moghimi SM (2002) Chemical camouflage of nanospheres with a poorly reactive surface Towards development of stealth and target-specific nanocarriers. Biochim Biophys Acta 1590 131-139... 

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