Reda F.M. Elshaarawy

Pharmacological performance of novel poly-(ionic liquid)-grafted chitosan-N-salicylidene Schiff bases and their complexes.

In our endeavor to develop a new class of pharmacological candidates with antimicrobial and anticancer efficacy, a series of biopolymeric chitosan Schiff bases bearing salicylidene ionic liquid (IL-Sal) brushes (ILCSB1-3, poly-(GlcNHAc-GlcNH2-(GlcN-Sal-IL)) was successfully synthesized by adopting efficient synthetic routes. Unfortunately, metalation trials of these biopolymeric Schiff bases afford the corresponding Ag(I)/M(II) complexes (where M=Co, Pd). These designed architectures were structurally characterized and pharmacologically evaluated for their in vitro antimicrobial, against common bacterial and fungal pathogens, and anticancer activities against human colon carcinoma (HCT-116) cell line. In conclusion functionalization of chitosan with IL-Sal brushes coupled with metalation of formed ILCSBs were synergistically enhanced its antimicrobial and antitumor properties to a great extent. Noteworthy, Ag-ILCSB2 (IC50=9.13μg/mL) was ca. 5-fold more cytotoxic against HCT-116 cell line than ILCSB2 (IC50=43.30μg/mL).

Ionic Sal-SG Schiff bases as new synergetic chemotherapeutic candidates: synthesis, metalation with Pd(II) and in vitro pharmacological evaluation

A series of novel N-(salicylidene)-sulfaguanidines (Sal-SG) bearing ionic liquid (IL) terminals (ILSSGH, 4a–f) have been synthesized by Schiff base condensation of IL-functionalized salicylaldehydes (ILSal, 3a–g) and sulfaguanidine (SG). Metalation trials of these ionic Schiff bases with palladium(II) chloride affords the corresponding Pd(II) complexes, [Pd(II)(ILSSG)Cl(H2O)] (5a–g). Further, the antimicrobial profiles of the new compounds against a set of common pathogens have been described. Zone of inhibition (ZOI) and minimal inhibitory concentration (MIC) values revealed that most of the new compounds exhibited significant antibacterial and potential inhibitory activity against Staphylococcus aureus (S. aureus), and this activity is modulated by substituents attached to the ionic liquid core as well as the counter-ion.

Surface functionalization of chitosan isolated from shrimp shells, using salicylaldehyde ionic liquids in exploration for novel economic and ecofriendly antibiofoulants

Since the use of organotin as antifouling additives was prohibited in 2003, many researchers have endeavored to design and develop novel economic environment-friendly marine antifouling additives. This work reports the successful functionalization of biopolymeric chitosan, isolated from shrimp shells, with salicylidene ionic liquid (IL-Sal) brushes, (ILCSB1–6). These designed architectures were structurally and morphologically characterized. Marine biofouling-inducing bacterial strains (S. aureus, E. coli, A. hydrophila and Vibrio) were selected as microfoulants for a laboratory antibacterial and biofilm susceptibility assay investigation. Our outcomes unveiled a novel promising ecofriendly biocidal agent with excellent and broad antibacterial efficacy compared to parent chitosan and the standard antifoulant, Diuron®. The fabricated poly-IL-brushes chitosan architectures were subjected to a rigorous test in a field trial in Red Sea water. Our findings provide new insights into eco-friendly antifouling additives as an alternative to traditional antifouling agents. Novel IL-functionalized chitosan-based coatings exhibited long-term durability, surface inertness and promising antifouling performance.

Turn-on pH nano-fluorosensor based on imidazolium salicylaldehyde ionic liquid-labeled silica nanoparticles

A new simple pH-sensitive fluorescent probe, methylimidazolium salicylaldehyde ionic liquid (MeIm-Sal-IL), was designed and successfully synthesized from commercially available salicylaldehyde (Sal) via an extremely simple efficient two-step synthetic protocol. This new pH sensor has prominent advantages over traditional fluorescent pH probes, such as a large Stokes shift (∼125 nm) and extreme aqueous solubility along with simultaneous color and fluorescence profile changes as a result of pH alteration. The fluorescence behavior of this new probe provides a new state-of-the-art pH sensing method. Fluorescence turn-on is observed with increasing pH (≈5 to 11), accompanied by a bathochromic shift of 70 nm from (λmax emission 435 to 505 nm; λmax absorption 323 to 378 nm). This bathochromic shift may be ascribed to the tautomeric equilibrium involving excited-state intramolecular proton transfer (ESIPT). Meanwhile, the fluorescence intensity enhancement at higher pH is attributable to the internal charge transfer (ICT) process. Also, the new probe was labeled with silica nanoparticles (SiNPs) in order to produce a novel nano-fluorosensor for pH measurements. The nanosensor was fabricated by covalent labeling of chloro-modified SiNPs with the new probe. The emission spectra of the new nanosensors are bathochromically shifted by about 65 nm (λmax emission 435 to 500 nm) at low pH (3 to 5). Moreover, the fluorescence intensity of the nanosensor is increased by ≈60 fold in the pH range from 5 to 9. The sensitivity of the new nanosensor is highly applicable within the pH range of 5 to 9, which suggests a broad variety of applications in the physiological pH range.

A ratiometric and selective fluorescent chemosensor for Ca(II) ions based on a novel water-soluble ionic Schiff-base

A new, simple and water-soluble chemosensor, based on the ionic Schiff-base (ISB), 1-(4-hydroxy-3-((2-mercaptophenylimino)methyl)-5-methoxybenzyl)-4-methoxypyridiniumchloride (3), was synthesized and applied to fluorescently sense Ca(II) ions. This fluorescent chemosensor demonstrates a high selectivity and sensitivity for Ca(II) ions over other physiological relevant alkali, alkaline-earth and transition metal ions. The mechanism of selectivity and sensitivity of ISB (3) to Ca(II) was suggested to be on the basis of internal charge transfer (ICT). Interestingly, chelation of Ca(II) to deprotonated ISB to form a complex with a 1 : 1 metal–ligand ratio can induce a decrease in the fluorescence emission peak centered at 545 nm and simultaneously enhance a new emission peak centered at 483 nm, thus affecting the ICT efficiency of the sensing system and providing ratiometric measurements. Furthermore, the same hypsochromic shift in the emission spectra was observed in both excitation states and absorption spectra. This newly developed sensor enables an ultrasensitive limit of detection (LOD) = 0.3 μM and the rapid detection of Ca(II) in the physiological pH range (pH 7.2) and thus may offer a new promising strategy for detecting Ca(II) in environmental and biological systems.

Microwave-assisted Hydrothermal Fabrication of Magnetic Amino-grafted Graphene Oxide Nanocomposite as a Heterogeneous Knoevenagel Catalyst

A rapid and facile one-step microwave-assisted hydrothermal approach was developed for the synthesis of diethylenetriamine (DETA)-functionalized graphene oxide decorated with Fe3O4 nanoparticles. This DETA-modulated magnetic graphene oxide (Fe3O4@DETA@GO) was used as a heterogeneous base catalyst for the Knoevenagel condensation. The composite demonstrated outstanding catalytic performance with easy recovery and reusability.Graphical Abstract

Mining marine shell wastes for polyelectrolyte chitosan anti-biofoulants: Fabrication of high-performance economic and ecofriendly anti-biofouling coatings

Banning organotins as antifouling biocides in 2003 was the starting point for many researchers to search for novel economic and environmentally-friendly anti-fouling biocides. In our present contribution, we have successfully functionalized a natural biopolymer, chitosan (CS), isolated from marine wastes with polyelectrolyte brushes akin to ionic liquids. These antifouling biopolymers anchoring polyelectrolyte brushes were in vitro assessed for their ability to eradicate or inhibit the Staphylococcal/Escherichia biofilms. Moreover, these anti-fouling candidates were incorporated into the matrix of commercial paint to formulate antifouling coatings which were subjected to a field static immersion test in the Mediterranean Sea in comparison to a standard antifoulant, Diuron®. The obtained results revealed the prevention of biofilms along with a promising anti-fouling performance. So the new polyelectrolyte chitosan architectures may offer promising anti-foulants additives for biofouling coating applications.

Ultrahigh performance of novel energy-efficient capacitive deionization electrodes based on 3D nanotubular composites

Capacitive deionization (CDI) is being progressed as an auspicious ion removal technique from brackish and seawater. Herein, we introduce a novel one-step facile chemical approach to fabricate tubular architectured composite electrodes made of both Titania and Multiwalled carbon nanotubes (TNTs/MWCNTs). The composites have been exploited, for the first time, as electrode materials for capacitive deionization. The composite electrodes were fully characterized via Field Emission Scanning Electron Microscopy (FESEM), Raman spectroscopy, X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) techniques, and Nitrogen Sorption. The electrochemical response was investigated by using Cyclic Voltammetry (CV), Galvanostatic Charge and Discharge (GCD), and Potentio-Electrochemical Impedance Spectroscopy (PEIS) measurements. The fabricated composite electrodes containing 5 wt% TiO2 nanotubes showed remarkable specific capacitance, conductivity, reversibility, and durability compared to pristine MWCNTs and other MWCNT-based composite electrodes reported in the literature. The desalination capability of the composite electrode was investigated using batch mode operation. The electrosorption capacity of the composite electrode containing 5 wt% TiO2 nanotubes (13.2 mg g−1) is approximately two fold larger than that of pristine MWCNTs (7.7 mg g−1), indicating an improved desalination efficiency. Therefore, the fabricated TNT/MWCNT composite electrode is a promising candidate for CDI technology.