PEGylation surfaces

Spatially confined self-assembly has been further confirmed by localizing ther-molysin on certain areas of a PEGylated surface. Upon immersion of this modified surface into a solution containing self-assembling precursors, nanostructures were formed in the vicinity of the enzyme, as observed through congo-red staining (Fig. 7c) [21]. Thus, enzyme-assisted self-assembly allows for construction of supramolecular polymers with spatiotemporal control, i.e. where and when they are required. 

The quality of the correlations demonstrated in Figure 6 provides strong evidence that the PLL-g-PEG technology is indeed suitable for producing PEGylated surfaces with a high degree of control over surface composition and with excellent reproducibility. 

Effects of Ionic Strength and Surface Charge on Protein Adsorption at PEGylated Surfaces... 

In summary, the findings of this study are in general agreement with the conclusions from many other published studies regarding the meehanisms behind the protein resistance of PEGylated surfaces. Electrostatic interactions are clearly... 

PEG-methacrylate was selected as the monomer to ensure biocompatibility, as PEGylated surfaces are known to inhibit protein binding. To demonstrate the accessibility of the surface azide groups, an azido-derivative of biotin was clicked to the polymer-brush-modified surface subsequently, surface plasmon resonance (SPR) was used to confirm the selective binding with streptavidin in preference to other proteins. 

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... 

Although the detailed mechanism of the longer circulation time of branched PEGylated protein is unclear, the architecture of PEG affects the release profile, the pharmacokinetics of the chug [29], and the behavior of the protein at the interface (e.g., protein absorption on hydrophobic surfaces [30]). 

The concept of de-PEGylation can be applied to the development of nanoparticle-based drug delivery systems. PEG is used for the modification of liposomes to increase their blood circulation time [38], However, it also prevents cellular uptake, resulting in a decrease in therapeutic efficiency thus, modifications of the liposome surface with PEG interfere with membrane fusion to the cell membrane and liposome decomposition [39]. One of the possible strategies to solve this problem is to cleave the PEG chains after the nanoparticle reaches the target site (Fig. 9). This system of de-PEGylation of liposomes is also useful in avoiding the immune... 

Fig. 9 Utility of de-PEGylation technology in liposomes, (a) PEG derivative possessing a lipid moiety. The covalent bond between PEG and the lipid moiety can be cleaved by stimuli such as those within the acid environment of cancer and inflammation, (b) After binding the target cell via specific recognition of the receptor by the ligand, PEG molecules on the surface of the liposome are cleaved. The release of PEG facilitates membrane fusion of the liposome and liposome decomposition, resulting in efficient drug delivery...

Fig. 10 PEGylation on the surface. A highly dense PEG layer composed of mixed-PEG prevents nonspecific protein interactions and inactivation of Fab ...

Pinholt C, Bukrinsky JT, Hostrup S, Frokjaer S, Norde W, Jorgensen L (2011) Influence of PEGylation with linear and branched PEG chains on the adsorption of glucagon to hydrophobic surfaces. Eur J Pharm Biopharm 77 139-147... 

Tamura M, Ichinohe S, Tamura A, Ikeda Y, Nagasaki Y (2011) In vivo and in vitro characteristics of core-shell-type nanogel particles optimization of core cross-linking density and surface PEG density in PEGylated nanogels. Acta Biomaterialia. doi 10.1016/j. actbio.2011.05.027... 

KNOB protein, however, was shown to improve gene expression markedly (130-fold in HeLa cells). Additionally, it was shown that PEG could be conjugated to the surface of the nanospheres to prevent aggregation during lyophilization without a loss of bioactivity following one month in storage. The PEGylated particles, however, were cleared from mice at a slower rate than unmodified controls and were found to accumulate in the kidney and liver at 15 min after intravenous administration. There was no difference after one hour, however. 

Sun XK, Rossin R, Turner JL, Becker ML, Joralemon MJ, Welch MJ, Wooley KL (2005) An assessment of the effects of shell cross-linked nanoparticle size, core composition, and surface PEGylation on in vivo biodistribution. Biomacromolecules 6 2541-2554... 

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