Drug re-engineering and repurposing: A significant and rapid approach to tuberculosis drug discovery.

The prevalence of tuberculosis (TB) remains the leading cause of death from a single infectious agent, ranking it above all other contagious diseases. The problem to tackle this disease seems to become even worse due to the outbreak of SARS-CoV-2. Further, the complications related to drug-resistant TB, prolonged treatment regimens, and synergy between TB and HIV are significant drawbacks. There are several drugs to treat TB, but there is still no rapid and accurate treatment available. Intensive research is, therefore, necessary to discover newer molecular analogs that can probably eliminate this disease within a short span. An increase in efficacy can be achieved through re-engineering old TB-drug families and repurposing known drugs. These two approaches have led to the production of newer classes of compounds with novel mechanisms to treat multidrug-resistant strains. With respect to this context, we discuss structural aspects of developing new anti-TB drugs as well as examine advances in TB drug discovery. It was found that the fluoroquinolone, oxazolidinone, and nitroimidazole classes of compounds have greater potential to be further explored for TB drug development. Most of the TB drug candidates in the clinical phase are modified versions of these classes of compounds. Therefore, here we anticipate that modification or repurposing of these classes of compounds has a higher probability to reach the clinical phase of drug development. The information provided will pave the way for researchers to design and identify newer molecular analogs for TB drug development and also broaden the scope of exploring future-generation potent, yet safer anti-TB drugs.

Ti-pillared montmorillonite clay for adsorptive removal of amoxicillin, imipramine, diclofenac-sodium, and paracetamol from water.

The adsorptive removal of natural montmorillonite (MMT) clay pillared with titanium oxide (Ti-PILC) was examined in this study to see the adsorptive remove of pharmaceutical compounds (PCs): amoxicillin (AMOX), imipramine (IMP), Diclofenac-Sodium (DIF-S), and paracetamol (PCM) from water under a batch-scale study. The post-intercalation changes in clay were investigated with various surface and structural analysis techniques. The results confirm an increase in the surface area, microporosity, and acidic sites (lewis acid) which improved and regulates Ti-PILC interactions with electron-rich PPCPs molecules. The FTIR bands for Si-OH and Al-OH show a shift in MMT, after pillaring, indicates the intercalation of Ti pillared in its interlayer space. The isotherms studies suggested the best fitting of Redlich Peterson models for all pharmaceutical adsorption data. The Langmuir adsorption (maximum) was recorded for Ti-PILC in the order: 82.68 (IMP) > 23.05 (DIF-S) > 20.83 (PCM) > 4.26 (AMOX) mg.g-1 at a fixed adsorbent dose i.e. 0.1 g·L-1. The PCs adsorption kinetics was also evaluated by Pseudo-first-, and second-order model and results showed the best curve fitting for all PCs. Results of regeneration studies showed that modified Ti-PILC could be a low-cost cleaner material for adsorption of pharmaceuticals from water.

Development of metal organic fromwork-199 immobilized zeolite foam for adsorption of common indoor VOCs.

Reticulated foam shaped adsorbents are more efficient for the removal of volatile organic compounds (VOCs), particularly from low VOC-concentration indoor air streams. In this study composite structure of zeolite and metal organic frameworks (MOFs), referred as ZMF, has been fabricated by immobilization of fine MOF-199 powder on foam shaped Zeolite Socony Mobil-5 (ZSM-5) Zeolitic structure, referred as ZF. The ZMF possess a uniform and well-dispersed coating of MOF-199 on the porous framework of ZF. It shows higher surface area, pore volume, and VOCs adsorption capacity, as compared to ZF-structure. Post-fabrication changes in selective adsorption properties of ZMF were studied with three common indoor VOCs (benzene, n-hexane, and cyclohexane), using gravimetric adsorption technique. The adsorption capacity of ZMF with different VOCs follow the order of benzene>n-hexane>cyclohexane. In comparison with MOF-199 and ZF, the composite structure ZMF shows improvement in selectivity for benzene from other two VOCs. Further, improvement in efficiency and stability of prepared ZMF was found to be associated with its high MOF loading capacity and unique morphological and structural properties. The developed composite structure with improved VOCs removal and recyclability could be a promising material for small to limited scale air pollution treatment units.

Ethane selective IRMOF-8 and its significance in ethane-ethylene separation by adsorption.

The separation of ethylene from ethane is one of the most energy-intensive single distillations practiced. This separation could be alternatively made by an adsorption process if the adsorbent would preferentially adsorb ethane over ethylene. Materials that exhibit this feature are scarce. Here, we report the case of a metal-organic framework, the IRMOF-8, for which the adsorption isotherms of ethane and ethylene were measured at 298 and 318 K up to pressures of 1000 kPa. Separation of ethane/ethylene mixtures was achieved in flow experiments using a IRMOF-8 filled column. The interaction of gas molecules with the surface of IRMOF-8 was explored using density functional theory (DFT) methods. We show both experimentally and computationally that, as a result of the difference in the interaction energies of ethane and ethylene in IRMOF-8, this material presents the preferential adsorption of ethane over ethylene. The results obtained in this study suggest that MOFs with ligands exhibiting high aromaticity character are prone to adsorb ethane preferably over ethylene.

Polyelectrolyte-assisted noncovalent functionalization of carbon nanotubes with ordered self-assemblies of a water-soluble porphyrin.

The self-assembly and induced supramolecular chirality of meso-tetrakis(4-sulfonatophenyl)porphyrin (TSPP) on both single-wall (SWCNT) and multiwall carbon nanotubes (MWCNT) are investigated. Under mild pH conditions (pH 3), TSPP forms aggregates when CNTs are dispersed in an aqueous solution containing positively charged polyelectrolytes such as poly-L-lysine (PLL) or poly(allylamine hydrochloride) (PAH). Evidence for the geometry of the porphyrin aggregates is obtained from absorption spectra, whereby the fingerprints of J- and H-aggregates are clearly seen only in the presence of smaller-diameter nanotubes. J-aggregates are better stabilized with PLL, whereas in the presence of PAH mainly H-aggregates prevail. Excited-state interactions within these nanohybrids are studied by steady-state and time-resolved fluorescence. The porphyrin emission intensity in the nanohybrid solution is significantly quenched compared to that of TSPP alone, and this implies strong electronic interaction between CNTs and porphyrin molecules. Fluorescence lifetime imaging microscopy (FLIM) further supports that porphyrin arrays are associated with the MWCNT sidewalls wrapped in PLL. In the case of the SWCNT hybrid, spherical structures associated with longer fluorescence lifetime appeared after one week, indicative of H-aggregates of TSPP. The latter are the result of π-π stacking of porphyrin units on neighboring nanotubes facilitated by the strong tendency of these nanotubes to interact with each other. These results highlight the importance of optimum dimensions and surface-area architectures of CNTs in the control/stability of the porphyrin aggregates with promising properties for light harvesting.

Studies on selective adsorption of biogas components on pillared clays: approach for biogas improvement.

Comparative adsorptions of four gases (natural gas and landfill gas components), viz., CO2, CH4, C2H6, and N2, were studied on four different pillared clays (PILCs) to develop a selective material. Such material could be useful forthe separation/purification process of waste gases. These materials (PILCs) were prepared from two different natural montmorillonite clays, by pillaring with Al2O3 and ZrO2, separately and were characterized by means of nitrogen adsorption and XRD. The adsorption isotherms for pure component gases were determined for each PILC, up to 10(3) kPa. The isotherms data were explored to calculate the selectivity of PILCs for either gas in any binary mixture. It was observed that the surface area of the clays pillared with Al2O3 was higher than that of the clays pillared with ZrO2. At the highest studied equilibrium pressure, the order of maximum adsorption was found to be CO2 > C2H6 > CH4 > N2 for each material. With the help of adsorption modeling, the selective adsorption from binary mixtures was predicted at different equilibrium pressures and compositions. Among the four PILCs, a ZrO2 PILC was found to be the most suitable material, in terms of separation possibility. To further assess the efficiency of these materials in commercial processes, the adsorption capacity in terms of working capacity was also calculated at two different regeneration pressures, i.e., at 1.0 atm and 1.0 Torr.

Adsorption studies on the removal of Vertigo Blue 49 and Orange DNA13 from aqueous solutions using carbon slurry developed from a waste material.

Waste material (carbon slurry), from fuel oil-based generators, was used as adsorbent for the removal of two reactive dyes from synthetic textile wastewater. The study describes the results of batch experiments on removal of Vertigo Blue 49 and Orange DNA13 from synthetic textile wastewater onto activated carbon slurry. The utility of waste material in adsorbing reactive dyes from aqueous solutions has been studied as a function of contact time, temperature, pH, and initial dye concentrations by batch experiments. pH 7.0 was found suitable for maximum removal of Vertigo Blue 49 and Orange DNA13. Dye adsorption capacities of carbon slurry for the Vertigo Blue 49 and the Orange DNA13 were 11.57 and 4.54 mg g(-1) adsorbent, respectively. The adsorption isotherms for both dyes were better described by the Langmuir isotherm. Thermodynamic treatment of adsorption data showed an exothermic nature of adsorption with both dyes. The dye uptake process was found to follow second-order kinetics.

Adsorption of 2,4-D and carbofuran pesticides using fertilizer and steel industry wastes.

The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and carbofuran from aqueous solution was studied by using fertilizer industry waste (carbon slurry) and steel industry wastes (blast furnace slag, dust, and sludge) as adsorbents in batch. Adsorption was found to be in decreasing order: carbon slurry, blast furnace sludge, dust, and slag, respectively. Carbonaceous adsorbent prepared from carbon slurry exhibited the uptake capacity of 212 and 208 mg g(-1) for 2,4-D and carbofuran, respectively at 25 degrees C and pH 7.5. Adsorption equilibrium, kinetics, and thermodynamics were investigated as a function of initial pH, temperature, and pesticide concentrations. Equilibrium data fitted well to the Langmuir equilibrium model in the studied concentration range of 2,4-D and carbofuran at all the temperatures studied. Two simplified models, including pseudo-first-order and pseudo-second-order kinetic models, were used to test the adsorption kinetics. Adsorption of 2,4-D and carbofuran on carbon slurry at 25, 35, and 45 degrees C could be best fitted in the pseudo-second-order kinetic model. Pore diffusion was confirmed as the essential rate-controlling step with the help of Bangham's equation.

Studies on the interaction of some azo dyes (naphthol red-J and direct orange) with nontronite mineral.

The adsorption of two azo dyes, namely naphthol red-J and direct orange, on nontronite mineral was studied as a function of pH and temperature. All the sorption studies were conducted in batch mode. The Langmuir and Freundlich isotherm models were applied. The isotherms are Langmuirian in nature, while the Freundlich equation is only valid over the low concentration range. The adsorption of the two dyes increases with increased temperature and decreases with increased pH. The data have been explained in terms of the area of contact of the dye molecule on the clay platelet vis-à-vis the area per anion exchange site. Estimated area per anion exchange site of the mineral and area associated per anionic dye molecule at nontronite surface was 642 and 454 A2 for naphthol red-J and 642 and 440 A2 for direct orange respectively. This has been further supported by X-ray measurements. Thermodynamic parameters of the process were evaluated.