Selective DNA Recognition and Cytotoxicity of Water-Soluble Helical Metallosupramolecular Polymers

Water-soluble polycarbodiimides and their cytotoxic and antifungal properties

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.

Characterization and Inception of a Triterpenoid Astrakurkurol, as a Cytotoxic Molecule on Human Hepatocellular Carcinoma Cells, Hep3B

Mushrooms are customary influential sources of pharmaceutically active metabolites. Usually lanostane-type triterpenoids from mushrooms had prospective for cancer disease treatments. Recently, a triterpenoid, astrakurkurol obtained from the fresh basidiocarps of the edible mushroom Astraeus hygrometricus, drew attention as a new cytotoxic therapeutic. The structural stability of this triterpenoid had been established with the amalgamation of density functional theory (DFT) calculations and study of single-crystal X-ray diffraction. To successfully manifest astrakurkurol as a potent cytotoxic therapeutics, a wide apprehension on the molecular and cellular mechanisms underlying their action is prerequisite. On this account, our study was directed to scrutinize the influence of this triterpenoid on human hepatocellular cancer cell model Hep3B. Encapsulating all experimental facts revealed that astrakurkurol had significantly decreased cell viability in a concentration-dependent manner. This effect was unveiled to be apoptosis, documented by DNA fragmentation, chromatin condensation, nuclear shrinkage, membrane blebing, and imbalance of cell cycle distribution. Astrakurkurol persuaded the expression of death receptor associated proteins (Fas), which triggered caspase-8 activation following tBid cleavage. Moreover, tBid mediated ROS generation, which triggered mitochondrial dysfunction and activated the mitochondrial apoptotic events. Astrakurkurol cytotoxicity was based on caspase-8-mediated intrinsic apoptotic pathway and was associated with inhibition at Akt and NF-κB pathway. Astrakurkurol had also inhibited the migration of Hep3B cells, indicating its antimigratory potential. These findings led us to introduce astrakurkurol as a feasible and natural source for a safer cytotoxic drug against hepatocellular carcinoma.

Increase in the apparent intercalation ability of a platinum complex via multivalency by installation into the sidechain of a graft copolymer and observation of structural changes in the intercalated DNA

Metal complexes with planar structures have been utilized as DNA intercalators that can be inserted into the base pairs of DNA strands, and have potential applications in DNA-targeting drug therapies. When designing the intercalator metal complexes, controlling their interactions with DNA is important, and has been performed by modifying the chemical structure of the metal ligand. Herein, we designed a graft copolymer segment having Pt complexes with bipyridine and poly(ethylene glycol) (p(PEGMA-co-BPyMA-Pt)) as another strategy to control the interaction with DNA via a multivalent effect. The p(PEGMA-co-BPyMA-Pt) increased not only the binding constant as one macromolecule but also the apparent binding constant per intercalator unit compared to the Pt complex with bipyridine (BPy-Pt). Moreover, p(PEGMA-co-BPyMA-Pt) induced a larger change in DNA structure using lower amounts of Pt than BPy-Pt. These observed properties of p(PEGMA-co-BPyMA-Pt) suggest that grafting intercalators on polymer segments is a promising approach for designing novel types of intercalators.

Pt complexes increase their apparent binding constant by grafting on sidechains of polymer segments via multivalent effect.

Manipulating Metallogel Properties by Luminogens and Their Applications in Cell Imaging

Manipulating gelation properties of the isomeric zinc-terpyridine complexes C-1 (nongelator) and C-2 (gelator) using three different luminescent dyes, viz., acridine yellow (AY), ethidium bromide (EB), and azido-boron dipyrromethene, have been described. Hybrid gels created by the combination of C-1, C-2, and above-mentioned dyes have been termed complex-luminogen mixed gels (CLMGs). Ensuing CLMGs have been thoroughly characterized by spectral, morphological, and rheological studies. Cytotoxicity measurements and imaging against breast cancer cell line MDA-MB-231 unveiled that three out of the five CLMGs can be effectively used for cell imaging. Interestingly, direct use of the metal-containing hybrid gels for live cell imaging which is a distinctive approach, has been successfully achieved with significantly encouraging results.

Effect of metal–metal distance in Ni(ii)-based metallo-supramolecular polymers: DNA binding and cytotoxicity

Two metallo-supramolecular polymers (polyNiL1 and polyNiL2) with different metal–metal distances were synthesized via (1 : 1) complexation of the Ni salts with bis(1,10-phenanthroline)s and their DNA binding properties and cytotoxicity were revealed.