We have successfully synthesized water-soluble neutral and
polyelectrolyte helical polycarbodiimides and studied their biological properties. These
polymers were prepared by decorating
carbodiimide backbones with nonionic, hydrophilic functional groups such as
dimethylamine,
piperazine, and
morpholine. Additionally, the 3°
amines present in these functional groups were quaternized using
methyl iodide as the
alkylating agent to produce their ionic analogs. Polycarbodiimides were chosen as the base
polymer used because of their facile chemical modification, pH tolerance in terms of both their helical conformations and degradation behaviors, and tunable helical inversion barriers. Hydrophilic side groups, such as
morpholine,
dimethylamine, and
piperazine, can be used to balance the amphiphilic architecture of the polycarbodiimides along with lipophilic groups, such as alkyl side chains. A chiral R or
S BINOL Ti(IV) isopropoxide catalyst was used to control the handedness of the polycarbodiimide helices in these studies. These ionic and neutral polycarbodiimides were subsequently studied for potential antimicrobial and cytotoxic properties. Poly[N-methyl-N'-2-morpholinoethylcarbodiimide], as an example, exhibited significant antifungal properties against Candida albicans. Also, Poly[N-methyl-N'-2-morpholinoethylcarbodiimide] showed significant inhibition of biofilm formation. This suggests that the
polymer is a promising candidate for antifungal biomedical applications. Measuring cytotoxicity against
urinary bladder cancer cells, poly[N-[3-(dimethylamino)propyl)]-N'-[3-(
morpholino)propyl]
carbodiimide] (S-cat) and poly[N-[3-(dimethylamino)propyl)]-N'-[3-(
morpholino)propyl]
carbodiimide]-MeI (S-cat) showed significantly low IC50 values. The IC50 values of poly[N-[3-(dimethylamino)propyl)]-N'-[3-(
morpholino)propyl]
carbodiimide] (S-cat) and Poly[N-[3-(dimethylamino)propyl)]-N'-[3-(
morpholino)propyl]
carbodiimide]-MeI (S-cat) are 3.50 μM and 1.27 μM, respectively. The significantly low
cancer cell growth inhibition concentration implies the highest cytotoxicity of the
polymers, suggesting potential applications as
cancer therapeutics. These results also showed that the functionalization and chirality of polycarbodiimides modulate their anticancer and antifungal activity.