Structural Rationale towards Designing Coordination Polymer Based Metallogels Displaying Anti‐Cancer and Anti‐Bacterial Properties

Organic and Coordination Polymer-Based Gelators-Directed Mechanically Self-Repairing Flexible Metallosupramolecular Soft Scaffolds

Ni(II)-source and terephthalic acid (TA)-based solvent-directed supramolecular metallogels (i.e., Ni-TA-DMF and Ni-TA-DMSO) are achieved in diverse polar-aprotic solvent media involving DMF and DMSO. The Zn(II) coordination polymer-based gel composite (CPG-composite) of Ni(II) is also originated by utilizing a terephthalic acid-directed chemically functionalized Zn(II)-based two-dimensional coordination polymeric network. The mechanical flexibility of metallogels is well-characterized through rheology. Ni-TA-DMF and Ni-TA-DMSO offer extensive self-repairing and load-tolerating proficiency. FESEM microstructural analyses unveil the solvent-directed variable morphological architecture of Ni-TA-DMF and Ni-TA-DMSO and the distinctive microstructural pattern of the CPG-composite. NMR analysis also supports the association between terephthalic acid and the Zn(II)-based two-dimensional coordination polymeric network (Zn(II) CP-TA), which ultimately directs the formation of the CPG-composite. The mechanistic strategy of forming metallogels and the CPG-composite has been scrutinized by using FT-IR and ESI-Mass studies. The semiconducting features of individual Ni-TA-DMF and Ni-TA-DMSO supramolecular metallogels along with the CPG-composite are investigated by fabricating distinct metal-semiconductor junction devices. Current-voltage parameters show the non-Ohmic conductive property in the fabricated devices. The nonlinearity and rectifying nature signify the Schottky barrier diode property of the fabricated devices. Significant diode features like conductivity, charge transport mechanism, ideality factor, and rectification ratio are also explored.

Nitrile-Containing Terpyridyl Zn(II)-Coordination Polymer-Based Metallogelators Displaying Helical Structures: Synthesis, Structures, and "Druglike" Action against B16-F10 Melanoma Cells

An attempt has been made to develop a self-drug-delivery system against melanoma from a series of metallogelators derived from coordination polymers. Thus, a series of coordination polymers (CP1-CP6) derived from a nitrile-containing terpyridyl ligand (L) and transition metal salts (Cu(I)/Zn(II)) have been synthesized and thoroughly characterized by a number of physicochemical techniques including single crystal X-ray diffraction. Reactions of the ingredients of the coordination polymers guided by their single crystal structures produced four metallogels (CPG2-CPG5) which were characterized by dynamic rheology and TEM. The metallogelator CPG3 turned out to be the best suited for further studies as revealed from MTT assay against melanoma (B16-F10) and macrophage (RAW 264.7) cells. Various experiments (scratch, cell cycle, nuclear condensation, annexin V-FITC/PI, mitochondrial membrane potential, Ho-efflux assays) not only supported the "druglike" action against melanoma B16-F10 cells but also suggested that the mechanism of cancer cell death was via mitochondrial membrane potential depolarization-driven apoptosis. Because melanoma B16-F10 is a model cell line for human skin cancer, the metallogel CPG3 may, therefore, be further developed for such treatment.

A self-healable metallohydrogel for drug encapsulations and drug release

A self-healable metallohydrogel (MOG) of Mn(ii) has been prepared using a low molecular weight gelator, Na₂HL {H₃L = l-(3,5-di-tert-butyl-2-hydroxy-benzyl)amino aspartic acid}. The MOG has been characterized by MALDI TOF mass spectrometry, rheological studies, IR spectroscopy, and microscopic techniques. Non-steroidal anti-inflammatory drug (NSAID), indomethacin (IND) and anti-cancer drug gemcitabine (GEM) were encapsulated into the metallohydrogel. The GEM-loaded metallogel (MOG_GEM) shows better delivery and more adverse cytotoxicity than the drug against breast cancer cell lines MDA-MB-468 and 4T1. The anti-cancer property was evaluated with in vitro MTT cytotoxic assay, live-dead assay and cell migration assay. In vitro cytotoxicity assay against RAW 264.7 cell line with the treatment of MOG_IND shows the improved anti-inflammatory response in the case of MOG_IND compared to the drug alone.