Biomedical Engineering Reference
In-Depth Information
CHAPTER 10
Zwitterionic Polymers for
Targeted Drug Delivery
d n 4 y 3 n g | 7
WEIFENG LIN, ZHEN WANG AND SHENGFU CHEN*
State Key Laboratory of Chemical Engineering, Department of Chemical and
Biological Engineering, Zhejiang University, Hangzhou 310027, P. R. China
* E-mail: schen@zju.edu.cn
10.1 Introduction
In the past decades, hydrophilic polymer coatings on drug-delivery vehicles have
been commonly used both to enhance the water solubility of the hydrophobic
drug and to evade recognition by the reticuloendothelial system (RES). 1,2 A
poly(ethylene glycol) (PEG) coating is the most frequently used one to prevent
nonspecific protein adsorption, lower phagocytosis into macrophage cells,
increase circulation time, and thus enhance both passive and active targeting. 3-5
In the authors' view, the resistance to nonspecific protein adsorption of PEG is
the key reason for the consequent performance in vitro and in vivo, while the
well-established functionalization methods facilitate the application of PEG.
However, it is now recognized that PEG decomposes in the presence of oxygen
and transition metal ions found in most biochemically relevant solutions. 6
Moreover, a possible immune reaction to PEGylated protein drug has also been
observed. 7 The complex formation between albumin and PEG further suggests a
possible unknown mechanism of PEG protection might be involved. 8 Another
problem is the accelerated blood clearance (ABC) phenomenon induced upon
repeated injections of PEG-coated colloidal carriers. 9,10 All these negative effects
Search WWH ::




Custom Search