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The article describes a study which investigated the development of a cationic liposome complexed with polyethylenimine and polyethylene glycol polymers (LPPC) which can acquire a variety of proteins without covalent conjugation. The maximal-binding capacity of bovine serum albumin is revealed through the characterizations of prepared LPPC. It also explains the importance of polyethylenimine as a complex component to bind the proteins.

Polymer-stabilized iron oxide nanoparticles could be used as contrast agents in magnetic resonance imaging (MRI) due to their unique superparamagnetism. Here we demonstrate a quaternized chitosan, i.e. N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC), encapsulating superparamagnetic iron oxide (SPIO), with very low toxicity and less effect on cell growth. HTCC has quaternary amino groups introduced into the chitosan chain, and such modification of chitosan should render it soluble in water. Most importantly, the HTCC-SPIO thus prepared has the ability to accelerate the MRI relaxation processes of surrounding water protons, resulting in enhanced MRI contrast (R2: y = 0.1076 x − 0.0092; R1: y = 0.008 x − 0.0005). The iron content quantified by Prussian blue staining and MRI revealed a positive correlation between Prussian blue positive cells and the change of MRI signal intensity. Also, transmission electron microscopy and element mapping confirmed intracellular metal-like spots as internalized iron oxide. Such findings support the use of these quaternized chitosan-stabilized iron oxide nanoparticles as a potential MRI contrast agent for cell tracking. Copyright © 2011 Society of Chemical Industry Cells loaded with quaternized chitosan encapsulating superparamagnetic iron oxide (SPIO) could be tracked and semi-quantified by magnetic resonance imaging. [ABSTRACT FROM AUTHOR]