Vikram Singh

DNA immobilization, delivery and cleavage on solid supports

Progress in bio-molecular chemistry, nanotechnology, and surface engineering resulted in the fabrication of nanoscale bio-systems with advanced functionalities. These systems and the related methodologies offer new perspectives for the development of novel bio-related diagnostic tools and gene and/or photodynamic therapy. A key issue in this context is the design and fabrication of “smart surfaces” able to immobilize functional biomolecules and DNA in particular, which can perform a certain function (e.g. hybridize with the target DNA strand) or be delivered or cleaved under the input of external stimuli (chemical, electrochemical, thermal, photochemical, etc.). This review addresses the above points dealing first with immobilization of DNA on various solid substrates using a bottom-up approach and describing later subsequent transport and/or cleavage of DNA using various routes.

Fe-terpyridyl complex based multiple switches for application in molecular logic gates and circuits

Molecular logic gates and circuits are constructed using the optical and electrochemical addressable-reversible-multiple switching event of the Fe(II)-4′-pyridyl terpyridyl complex (1) using multiple analytes. The process involves oxidation–reduction of Fe2+ as well as successive quaternization–dequaternization of the free pendant pyridyl group monitored optically. The whole switching process could also be visualized by the naked eye as colour changes upon switching are quite apparent and instant.

Covalent Assembled Monolayers of Homo- and Heteroleptic Fe(II)-Terpyridyl Complexes on SiOx and ITO-Coated Glass Substrates: An Experimental and Theoretical Study

Well-defined FeII -terpyridyl monolayers were fabricated on SiOx and conductive ITO-coated glass substrates through covalent-bond formation between the metallo-organic complexes and a preassembled coupling layer. Three different homo- and heteroleptic complexes with terminal pyridyl, amine, and phenyl groups were tested. All the films were found to be densely packed and homogeneous, and consist of molecules standing upright. They exhibited high thermal (up to ≈220 °C) and temporal (up to 5 h at 100 °C) stability. The UV/Vis spectra of the monolayers showed pronounced metal-to-ligand charge-transfer bands with a significant redshift compared with the solution spectra of the metallo-ligands with a pendant pyridyl group quaternized with the coupling layer, whereas the shift was significantly smaller when the coupling layer was bonded to the primary amine (-NH2 ) group of the complex. Cyclic voltammograms of the monolayers showed reversible, one-electron redox behavior and suggested strong electronic coupling between the confined molecules and the underlying substrate. Analysis of the electrochemistry data allowed us to estimate the charge-transfer rate constant between the metal center and the substrate. Additionally, detailed quantum-chemical calculations were performed to support and rationalize the experimentally observed photophysical properties of the FeII -terpyridyl complexes both in the solution state and when bound to a SiOx -based substrate.

Heteroleptic Cu(II)–polypyridyl complexes as photonucleases

A series of heteroleptic Cu(II)–polypyridyl complexes with terpyridine (3N)/imidazole (2N) backbones and appended with pyridyl, 2-naphthyl, 9-anthryl and 1-pyrenyl groups are synthesized and evaluated for their photonuclease activity. An array of techniques viz. UV-vis, fluorescence, circular dichroism and thermal denaturation established strong DNA binding affinity (Kb = ∼104–106 M−1) and the binding modes were correlated with molecular docking studies. Photonuclease efficiency exceeded 90% for all the complexes under identical conditions. Interestingly, DNA binding propensity and photonuclease efficiency followed the increasing size, planarity, aromaticity, π-Stacking ability and hydrophobicity of the peripheral moiety.

Emphasizing the pharmaceutical consideration behind the development of gastro-retentive dosage form

Recent technological and scientific research has been devoted to the development of rate controlled drug delivery systems to overcome physiological adversities such as short gastric residence times and unpredictable gastric emptying times. The floating or hydro-dynamically controlled drug delivery systems are useful in such application. The objective of our review is to compile the recent advancements and developments regarding the novel dosage form i.e. the floating drug delivery systems (FDDS) that can be retained in the stomach for a prolonged period of time and gives therapeutic action in a predetermined manner. In these review article,the various aspects of pharmaceutical floating drug delivery system(FDDS) were compiled together and the target ordinance are specifically the M. Pharm and B Pharm students so that their knowledge towards the subject concern can be enhanced and also at the same time can be motivated towards the publication.