Amphoteric poly(amido amine)s with adjustable balance between transfection efficiency and cytotoxicity for gene delivery. 
In order to balance transfection efficiency and cytotoxicity as well as screen the optimal polymers for gene delivery, a series of amphoteric copolymers (poly(CBA-AGM/GABA)s) composed of different ratios between agmatine (AGM) and γ-aminobutyric acid (GABA) monomers were synthesized.  The AGM containing positively charged guanidinium groups was used to improve transfection efficiency, while the GABA containing negatively charged carboxyl groups was used to decrease cytotoxicity.  It is hypothesized that the amphoteric poly(CBA-AGM/GABA)s synthesized at the optimal ratio of both components would well balance transfection efficiency and cytotoxicity.  By comparing these polymers' essential features in gene delivery, the ideal ratio between AGM and GABA was optimized.  AGM80, which contained 80% AGM and 20% GABA, showed favorable properties for gene delivery, including moderate DNA condensation capacity, high cellular uptake, strong nuclear localization ability, high transfection efficiency, and low cytotoxicity, indicating that this polymer is very promising as a potent and nontoxic gene carrier.