Designing Unconventional Molecular Ternary INHIBIT Logic Gate and Crafting Multifunctional Molecular Logic Systems.

The paper describes an improved method for building flexible interswitchable logic gates such as rare-type molecular ternary INHIBIT and combinational logic circuits using a specially designed pyridine-end oligo-p-phenylenevinylene compound featuring alkyl substituents (-C16H33) in a THF medium. The probe molecule showed distinct opto-chemical signals upon interaction with Cu(II) and Hg(II) in THF medium. It is interesting to note that the presence of certain anions (S2-, I-, and CN-) could specifically mask the interaction of either of these metal ions or both. The most exciting thing is that we used a completely new gate design technique to construct a rare-type ternary INHIBIT logic gate using Cu(II), Hg(II), and CN- ions as three chemical inputs. With the identical set of chemical inputs, two more ternary combinational logic circuits were created out of these case-specific, independent reversible and irreversible spectroscopic studies. Finally, we were able to design adaptive molecular logic systems composed of several logic gates, including NOR, AND, IMPLICATION, INHIBIT, TRANSFER, and COMPLEMENT, that in this specific situation change the sort of logic sense by effortless optical toggling.

Dye-surfactant co-assembly as the chromogenic indicator for nanomolar level detection of Cu(I) ions via a color-changing response.

Polyaromatic amphiphilic probes have been developed, that can be involved in chromogenic detection of Cu+ ions in anionic micelles. A rapid change in solution color from yellow to orange was observed in the presence of Cu+ ions. The detection limit was found at the nanomolar range. To the best of our knowledge, this is the first report of the visible detection of Cu+ ions in aqueous medium using anionic micelles as a stabilizing agent. Interestingly, the compound can also detect Cu+ ions, generated in situ from physiological redox processes. The mechanistic investigation suggests that the probe molecule forms a diamagnetic tetrahedral complex with the Cu+ ion, coordinating through a pyridyl ketone unit. In addition, we have also followed the interaction with Cu+ on a bilayer surface made of anionic phospholipids. Further, a Cu2+-probe ensemble is used to assay the reducing ability of different biogenic thiols depending upon the pKa of their sulfhydryl (-SH) group. This allows us to determine the amount of reducing thiols present in human urine samples. Considering the high sensitivity of the present system, we screened water samples collected from different natural sources for Cu+ ions. Nearly 100% recovery values with considerably small relative standard deviations (<5%) indicate that the present system is indeed suitable for real-life sample analysis. Finally, low-cost, reusable, chemically-modified paper strips have been developed for rapid, on-location detection of Cu+ ions.

Differential response for multiple ions: a smart probe to construct optically tunable molecular logic systems.

A rhodamine-based optical probe has been designed through a one-pot synthetic protocol involving phenanthroline as a binding motif. The compound showed a bright pink coloration specifically upon the addition of Cu2+ and Hg2+ ions. However, the appearance of bright red fluorescence was observed only in the presence of Hg2+. Considering both, we can detect and discriminate these two ions even at ppb level concentration. Furthermore, these in situ generated metal complexes were utilized for the selective recognition of CN- and I- ions. Pre-coated TLC plates were developed for rapid on-site detection of these toxic ions even in remote places. Finally, on a single molecular probe based on differential opto-chemical interactions with different ions (Cu2+, Hg2+, CN- and I-), we were able to design numerous trivial (OR, NOR) and non-trivial (INHIBIT, IMPLICATION, COMPLEMENT, TRANSFER, NOT-TRANSFER) logic gates. Most fascinatingly, we can switch the logic response from one type to another by simply tuning only the optical output channel.

Controlled tuning of radiative-nonradiative transition via solvent perturbation: Franck-Condon emission vs. aggregation caused quenching.

Organic molecules with tunable fluorescence quantum yield are attractive for opto-electronic applications. A fluorophore with tunable fluorescence quantum yield should be a better choice for a variety of applications that demand fluorophores with different quantum yields. Here organic emitters with a continuous bell-shaped fluorescence yield profile would be promising in view of sustainability and reusability; however, fluorophores with these properties are rarely reported. A bis-indole derivative, 3,3'-bisindolyl(phenyl)methane (BIPM), was synthesised and found to undergo a unique 'rise-and-fall' profile in fluorescence yield with a compositional change of the 1,4-dioxane (DiOx)-H2O solvent system. A predominant interplay of two contrasting factors, (a) polarity and proticity induced emission enhancement and (b) aggregation caused fluorescence quenching, on either side of a crossover solvent composition (∼50% fW), resulted in a continuous bell-patterned fluorescence yield profile. Interestingly, these two factors could be observed individually or simultaneously by adjusting the H2O fraction. Detailed spectroscopic, electron microscopic and computational studies have been performed to substantiate the photophysics behind the solvent regulated modulation of fluorescence quantum yield.

Excitation wavelength as logic operator.

Multiple molecular logic gates were harvested on a single synthesized material, (E)-2-(2-hydroxy-3-methoxybenzylideneamino)phenol (MBAP), by combining excitation wavelength dependent multi-channel fluorescence outputs and the same chemical inputs. Interestingly, the effortless switching of logic behavior was achieved by simply tweaking the excitation wavelength and sometimes the emission wavelengths with no alteration of chemical inputs and the main device molecule, MBAP. Additionally, new generation purely optically driven memory units were designed on the same system supporting an almost infinite number of write-erase cycles since inter-conversion of memory states was completely free from chemical interferences and impurity issues. Two-way memory functions ("erase-read-write-read" and "write-read-erase-read") worked simultaneously on the same system and could be accessed by simple optical switching between two excitation and emission wavelengths. Our optically switchable device might outperform traditional multifunctional logic gates and memory devices that generally employ chemical triggers to switch functionality and memory states. These optically switchable multifunctional molecular logic gates and memory systems might drive smart devices in the near future with high energy efficiency, extended life span, structural and functional simplicity, exclusive reversibility and enhanced data storage density.

Circumstantial Overdose Management of an Efficient Cancer Cell Photosensitizer with Preclinical Evidence: A Biophysical Study.

In this article, pharmacological management of circumstantial overdose of an anticancer drug, Harmine (HM), under in vitro and in vivo conditions is described and further validated by employing in silico methods. HM, an efficient cancer cell photosensitizer, interacts extensively with nontoxic ß-cyclodextrin (ß-CD). Steady-state fluorescence studies and molecular docking analysis established differential nature of molecular inclusion depending on the relative concentrations of ß-CD. Presently, ß-CD is commonly used as a standard drug-delivery vehicle but its application for controlled drug withdrawal is rarely explored. Flow cytometric results and in vivo investigations on a zebrafish model showed that conditional overdose of preadministered drug molecules can be efficiently removed by encapsulating successfully within nontoxic ß-CDs, albeit by controlled application of the same. This is an approach to manage the cytotoxicity of a drug in a safe way that is already administered. We believe that this ß-CD-mediated withdrawal of drugs may find possible applications in controlled capturing of excess or unused drug inside living systems and reducing the unwanted toxicity associated with chemotherapeutics.

A newly developed highly selective Zn2+-AcO- ion-pair sensor through partner preference: equal efficiency under solitary and colonial situation.

Unusual self-sorting of an ion-pair under highly crowded conditions driven by a synthesized intelligent molecule 2-((E)-(3-((E)-2-hydroxy-3-methoxybenzylideneamino)-2-hydroxypropyl imino)methyl)-6-methoxyphenol, hereafter HBP, is described. When a mixture of various metal salts was allowed to react with HBP, only a specific ion-pair ZnII/AcO- in the solution simultaneously reacted, resulting in high-fidelity ion-pair recognition of HBP. This phenomenon was evidenced by significant changes in the absorption spectra and huge enhancement in emission intensity of HBP. The property that one molecule preferring one particular cation-anion pair over others is a rare but interesting phenomenon. Thus, the potential to interact selectively with the targeted ion-pair resulting in the formation of a specific complex recognized HBP as a new class of molecule that might find future applications in real time and on-site monitoring and separation of new molecules.

Shipment of a photodynamic therapy agent into model membrane and its controlled release: A photophysical approach.

Harmine, an efficient cancer cell photosensitizer (PS), emits intense violet color when it is incorporated in well established self assembly based drug carrier formed by cationic surfactants of identical positive charge of head group but varying chain length, namely, dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB). Micelle entrapped drug emits in the UV region when it interacts with non-toxic ß-cyclodextrin (ß-CD). Inspired by these unique fluorescence/structural switching properties of the anticancer drug, in the present work we have monitored the interplay of the drug between micelles and non-toxic ß-CDs. We have observed that the model membranes formed by micelles differing in their hydrophobic chain length interact with the drug differently. Variation in the surfactant chain length plays an important role for structural switching i.e. in choosing a particular structural form of the drug that will be finally presented to their targets. The present study shows that in case of necessity, the bound drug molecule can be removed from its binding site in a controlled manner by the use of non-toxic ß-CD and it is exploited to serve a significant purpose for the removal of excess/unused adsorbed drugs from the model cell membranes. We believe this kind of ß-CD driven translocation of drugs monitored by fluorescence switching may find possible applications in controlled release of the drug inside cells.