Comparison of toxicity and transfection efficiency of amphiphilic block copolymers and polycationic polymers in...

Gene delivery using synthetic vectors is frequently based on cationic compounds such as polyethyleneimine (PEI). However, few data have been published on the ability of PEI to mediate transgene expression in muscle tissue. Besides cationic vectors, there is increasing interest focusing on amphiphilic copolymers as gene carriers into striated muscles, although their mechanism of action is unknown.

Plasmid DNA was associated with three different polymers: the cationic polyethyleneimine and two amphiphilic copolymers displaying few (tetronic 304) or no charges (pluronic L64). The resulting formulations were investigated by dynamic light scattering, laser doppler velocimetry, gel retardation assay and transmission electron microscopy. The toxicity and efficiency of the carriers were assessed in both skeletal and cardiac muscles.

PEI efficiently condenses plasmids into small complexes displaying a positive electrophoretic mobility. However, these PEI/DNA complexes lead to severe side-effects in vivo. The association between amphiphilic copolymers and DNA leads to no or only partial condensation of plasmids. Moreover, amphiphilic polymers do not interact strongly with DNA and tetronic-based systems are destabilized with a decreasing pH. Those vectors also display a negative electrophoretic mobility. Thus, characteristics of amphiphilic polymer/DNA systems might be considered unfavourable for transfection. However, safe and rather efficient gene expression was obtained in skeletal muscles, even at low DNA doses, but not in the myocardium.

The present study highlights the interest in amphiphilic carriers for promoting DNA transfection in vivo. Gaining new insights into the properties of these vectors should allow their optimization.