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.

Molecular docking, QSAR properties and DNA/BSA binding, anti-proliferative studies of 6-methoxy benzothiozole imine base and its metal complexes

The molecular and QSAR (Quantitative Structure-Activity Relationship) properties of title compound 2-((6-Methoxybenzo[d]thiazol-2-ylimino)methyl)-6-ethoxyphenol (HL) were evaluated employing HyperChem 7.5 tools. The interaction of the 1a-1e complexes of HL with calf thymus DNA (CT-DNA) was investigated by absorption titrations, Fluorescence quenching and viscosity measurements. The experimental data suggest that these complexes bind to CT-DNA through an intercalative mode, wherein DNA-binding affinity of 1e is found to be greater compared to other complexes. The tryptophan emission-quenching with bovine serum albumin (BSA) experiment revealed stronger binding of 1e than other complexes in the hydrophobic region of protein. The photocleavage of plasmid pBR322 DNA investigated in the presence of the title complexes inferred conversion of supercoiled form of DNA plasmid to circular nicked form. Free-radical scavenging activity studies of HL and its metal complexes determined by their interaction with the stable free-radical DPPH have shown promising antioxidant property. Further cytotoxicity studies with HeLa and MCF-7 cell lines indicated that the compounds can efficiently inhibit the cell proliferation in a dose dependent manner. The DAPI staining assay studies revealed the higher potency of 1e to induce apoptosis. AbbreviationsBSABovine serum albumin proteinCT-DNACalf thymus DNADMSODimethyl sulfoxideDAPI4',-6-Diamidino-2-phenylindole dihydrochlorideESI-MSElectrospray ionization mass spectrometryIC₅₀Half-maximal inhibitory concentrationMBTYE2-((6-methoxybenzo[d]thiazol-2-ylimino) methyl)-6-ethoxyphenolMTT3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromidePBSPhosphate-buffered salineTrisTris(hydroxymethyl)aminomethaneCommunicated by Ramaswamy H. Sarma.

Design, synthesis, in vitro anticancer, antioxidant and antibacterial activity; DNA/BSA binding, photoleavage and docking studies of Cu(II) ternary metal complexes

Three mononuclear, mixed ligand ternary Cu(II) complexes of 3-((Z)-1-(2-hydroxyphenylimino)ethyl)-4-hydroxy-6-methyl-2H-pyran-2-one (HEHMP) viz; [Cu-(Phen) (HEHMP)] (1a), [Cu-(Bpy)(HEHMP)] (1 b) and [Cu-Bpy(NCS)(HEHMP)] (1c) were synthesized and characterized by data obtained from various spectral techniques. The binding affinities of these complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) protein were explored by absorption and fluorescence quenching titrations. The results indicated strong affinity of the title compounds to bind with both CT-DNA and BSA. The antioxidant properties of the synthesized compounds evaluated by free-radical scavenging method using spectrophotometric technique indicated their affirmative potential activity. Gel electrophoresis experiments revealed the efficacy of metal complexes in resulting the cleavage of pBR322 supercoiled DNA. In vitro cytotoxicity studies of these complexes evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against HeLa and MCF-7 cancer cell lines indicated relatively high effectiveness of the complex 1c. Confocal microscopy signified the potential of the complexes to induce apoptosis in HeLa cell lines. In addition, the antibacterial activity of the compounds carried out by disc diffusion method revealed significantly enhanced antibacterial activity in Cu (II) ternary complexes compared to the activity of ligands in unbound form signifying the implicit role of metal ion in inducing lipophilic character.

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.

Metal-containing and related polymers for biomedical applications

A survey of the most recent progress in the biomedical applications of metal-containing polymers is given. Due to the unique optical, electrochemical, and magnetic properties, at least 30 different metal elements, most of them transition metals, are introduced into polymeric frameworks for interactions with biology-relevant substrates via various means. Inspired by the advance of metal-containing small molecular drugs and promoted by the great progress in polymer chemistry, metal-containing polymers have gained momentum during recent decades. According to their different applications, this review summarizes the following biomedical applications: (1) metal-containing polymers as drug delivery vehicles; (2) metal-containing polymeric drugs and biocides, including antimicrobial and antiviral agents, anticancer drugs, photodynamic therapy agents, radiotherapy agents and biocides; (3) metal-containing polymers as biosensors, and (4) metal-containing polymers in bioimaging.

Platinum(II)-Based Metallo-Supramolecular Polymer with Controlled Unidirectional Dipoles for Tunable Rectification

A platinum(II)-based, luminescent, metallo-supramolecular polymer (PolyPtL1) having an inherent dipole moment was synthesized via complexation of Pt(II) ions with an asymmetric ligand L1, containing terpyridyl and pyridyl moieties. The synthesized ligand and polymer were well characterized by various NMR techniques, optical spectroscopy, and cyclic voltammetry studies. The morphological study by atomic force microscopy revealed the individual and assembled polymer chains of 1-4 nm height. The polymer was specifically attached on Au-electrodes to produce two types of film (films 1 and 2) in which the polymer chains were aligned with their dipoles in opposite directions. The Au-surface bounded films were characterized by UV-vis, Raman spectroscopy, cyclic voltammetry, and atomic force microscopy study. The quantum mechanical calculation determined the average dipole moment for each monomer unit in PolyPtL1 to be about 5.8 D. The precise surface derivatization permitted effective tuning of the direction dipole moment, as well as the direction of rectification of the resulting polymer-attached molecular diodes. Film 1 was more conductive in positive bias region with an average rectification ratio (RR = I(+4 V)/I(-4 V)) ≈ 20, whereas film 2 was more conducting in negative bias with an average rectification ratio (RR = I(-4 V)/I(+4 V)) ≈ 18.

A vapoluminescent Eu-based metallo-supramolecular polymer

An Eu-based metallo-supramolecular polymer (polyEu) was prepared by self-assembly coordination polymerization. Unique vapoluminescence property of polyEu triggered by acid-base vapor was found and a photoluminescence display in switchable imaging by acid-base vapor was fabricated.