Quantitatively investigating monomethoxypolyethylene glycol modification of protein by capillary electrophoresis

PEGylated chitosan-based polymer micelle as an intracellular delivery carrier for anti-tumor targeting therapy

Stearic acid-grafted chitosan oligosaccharide (CSO-SA) micelles presented a potential candidate for intracellular drug delivery carrier due to its special spatial structure. In this article, CSO-SA was further modified by polyethylene glycol (PEG). The physicochemical properties of PEGylated CSO-SA (PEG-CSO-SA) micelles were characterized. After PEGylation, the critical micelle concentration (CMC) of PEG-CSO-SA had no significant change; the micelle size increased; and the zeta potential decreased. The cellular uptake of CSO-SA micelles before and after PEGylation in macrophage RAW264.7, immortalized rat liver cells BRL-3A and human liver tumor cells HepG2 was studied. About 58.4+/-0.63% of CSO-SA micelles were uptaked by RAW264.7 in 24h, however, only 17.7+/-0.94% of PEG-CSO-SA micelles were internalized into RAW264.7 after the CSO-SA was modified with PEG in five molar times. Meanwhile, there were no changes in the uptake after PEGylation of CSO-SA in BRL-3A and HepG2. Using mitomycin C as a model drug, the in vitro anti-tumor activities of the drug loaded in the micelles were investigated. The 50% cellular growth inhibition (IC(50)) of the drug decreased from 1.97+/-0.2 to 0.13+/-0.02mug/mL after mitomycin C was loaded into CSO-SA micelles, and the IC(50) value of the drug had no obvious change when the CSO-SA was modified by PEG.

Native PAGE eliminates the problem of PEG–SDS interaction in SDS-PAGE and provides an alternative to HPLC in characterization of protein PEGylation

PEGylation of proteins has become an increasingly important technology in recent years. However, determination and characterization of the PEGylation products are problematic especially for the reaction mixture containing various modified proteins, unreacted PEG, and unmodified protein. A comparative study was carried out with two HPLC methods and two electrophoresis methods for characterization of the reaction mixture in PEGylation of HSA with PEG 5000, 10000, and 20000. RP-HPLC fails to give the correct information about the reaction of PEG 20000. Size-exclusion HPLC (SE-HPLC) produced very poor resolution on the PEG 5000 reaction. SDS-PAGE can run multiple samples of all PEGylation but the bands were smeared or broadened probably due to the interaction between PEG and SDS. On the other hand, native PAGE eliminates the problem of PEG-SDS interaction and provides better resolutions for all samples. Various PEGylated products and unmodified protein migrate differentially in native PAGE under nondenatured conditions. The results demonstrated that native PAGE could be a good alternative to HPLC and SDS-PAGE for the analysis of PEG-protein conjugates especially for characterization of the PEGylation mixture.

Capillary electrophoresis of proteins 2003-2005

This review article with 304 references describes recent developments in CE of proteins, and covers the two years since the previous review (Hutterer, K., Dolník, V., Electrophoresis 2003, 24, 3998-4012) through Spring 2005. It covers topics related to CE of proteins, including modeling of the electrophoretic migration of proteins, sample pretreatment, wall coatings, improving separation, various forms of detection, special electrophoretic techniques such as affinity CE, CIEF, and applications of CE to the analysis of proteins in real-world samples including human body fluids, food and agricultural samples, protein pharmaceuticals, and recombinant protein preparations.