Cationized human serum albumin as a non-viral vector system for gene delivery? Characterization of complex formation with plasmid DNA and transfection efficiency

Cationized human serum albumin (cHSA) could serve as a potential non-viral vector system for gene delivery. Native human serum albumin was cationized by covalent coupling of hexamethylenediamine to the carboxyl groups resulti ng in a shift of the isoelectric point from pH 4-5 to 7-9. The cationized a lbumin underwent spontaneous self-assembly with DNA as demonstrated by reta rdation of CMV-nlacZ plasmid in agarose gel electrophoresis. Photon correla tion spectroscopy showed a decrease of complex size with increasing cHSA/pl asmid ratios. Under optimized conditions complexes were formed with 230-260 mn mean diameter and a homogenous, narrow size distribution. At room tempe rature complexes were stable in 0.9% sodium chloride solution pH 7.4 for 1 h without aggregation. Process parameters such as albumin concentration, in cubation time, temperature, pH, order of reagent addition, the presence of bivalent ions and the ionic strength of the complexation medium all influen ced the complex size. Confocal laser scanning microscopy showed interaction s of a Texas Red labeled cationized albumin with cell membranes of ECV 304 cells and an enhanced endocytic uptake compared to native albumin. The pote ntial for introducing exogeneous DNA into cells was shown using NIH 3T3 fib roblasts. Successful, albeit low reporter gene expression could be achieved in the presence of chloroquine. Under in vitro conditions no toxic effect could be observed. In conclusion, cationized albumin may have promise as a non-toxic vector for gene delivery, especially for DNA vaccination. (C) 200 1 Elsevier Science B.V. All rights reserved.