Characterization of non-viral vectors for gene transfer : evaluation of size investigations through dynamic light scattering (DLS) to characterize

Within this work, from a large amount of non-viral vectors available for gene transfer, some representative ones were chosen to be associated to the widely used reporter gene pCMVβGal. Polycationic bPEI, single positively charged poloxamine 304 and the non-ionic poloxamer PE6400 were applied as polymeric DNA carrier systems. Further non-polymeric formulations contained non-charged cholesterol or monocationic DC-cholesterol, both solubilized by randomly methylated β-cyclodextrins (rM-β-CD). As dispersants, water, NaCl 0.45% and Tyrode’s solution were used. Size investigations of the resulting structures were performed through dynamic light scattering (DLS) to evaluate the utilizability of the technique in such concerns. It appears that the interaction behavior strongly depends on the physicochemical properties of the applied vector: for bPEI and poloxamine 304, both exhibiting strong electrostatic interactions with DNA, the method accurately describes the samples in various media and concentrations. The interaction potential between the plasmid and its complexation partner is clearly evidenced from the size distribution profiles that are different for DNA alone, the vector alone and the associates of both components. The hydrodynamic diameters of the PE6400, cholesterol or DC-cholesterol containing formulations strongly resemble the ones obtained for DNA alone. Since an overlay between the peaks of pCMVβGal and the vector may exist, the application of DLS as sole technique cannot clearly affirm the existence of interactions for theses dynamic structures. To round off the investigations, morphological cryo-TEM analysis and ζ-potential measurements were performed in addition.