4-Dialkylamino-2,5-dihydroimidazol-1-oxyls with Functional Groups at the Position 2 and at the Exocyclic Nitrogen: The pH-Sensitive Spin Labels

Local acidity and electrostatic interactions are associated both with catalytic properties and the adsorption activity of various materials, and with the vital functions of biomolecules. The observation of acid–base equilibria in stable free radicals using EPR spectroscopy represents a convenient method for monitoring pH changes and the investigation of surface electrostatics, the advantages of which are especially evident in opaque and turbid samples and in porous materials such as xerogels. Imidazoline nitroxides are the most commonly used pH-sensitive spin probes and labels due to the high sensitivity of the parameters of the EPR spectra to pH changes, their small size, and their well-developed chemistry. In this work, several new derivatives of 4-(N,N-dialkylamino)-2,5-dihydrioimidazol-1-oxyl, with functional groups suitable for specific binding, were synthesized. The dependence of the parameters of their EPR spectra on pH was studied. Several showed a pKa close to 7.4, following the pH changes in a normal physiological range, and some demonstrated a monotonous change of the hyperfine coupling constant by 0.14 mT upon pH variation by four units.

Effect of pH variation on cross-linking of water-soluble and acid-soluble chitosan with sodium tripolyphosphate and gallium-67

Background: Chitosan is a cationic biopolymer obtained from deacetylating chitin, a naturally compoundpresent in crustacean shell, fungi and exoskeleton of insects. Chitosan has various applications including drug and gene delivery systems, wound dressing and as scaffolds for tissue engineering, agriculture, textile, food and feed nanotechnology, waste water treatments. chitosan-TPP particle figure out as the most important and stable nanoparticle for chitosan application in various fields. Objective: At this study chitosan was chemically modified by sodium tripolyphosphate (TPP). Afterward, TPP-chitosan was radiolabeled with gallium-67 radionuclide. The effect of several factors on labeling yield such as chitosan solubility, acidity and concentration of TPP-chitosansolution, incubation time with gallium-67 were investigated. Methods: To prepare [67Ga] gallium-chitosan complex, chitosan (0.5 ml) was dissolved in 2.2 mCi of [67Ga] gallium chloride solution. The obtained solution was stirred for 5 min and then was kept for 30 min at room temperature. Radiochemical purity and radiolabeling yield was measured via radiochromatography that it was performed by using a radio thin-layer chromatography (TLC) scanner instrument. To investigate the effect of chitosan kind and concentration on the labeling yield, two kinds of chitosan (acid-soluble chitosan and water-soluble chitosan) with two different concentrations (1% and 0.5%) at different pH were used. In addition, labeling efficiency and stability of the 67Ga-TPP-chitosan complex (acidic/water soluble chitosan) at both concentrations (0.5 and 1%) at room temperature was assessed for 30, 45 and 60 min. Results: The incubation time has not significant effect on labeling yield. The acidic soluble chitosan, which has highest radiolabeling yield at pH=9.3-10.4, water soluble chitosan showed the highest radiolabeling yields at pH > 5. Also, the prepared complex was stable in the final solution at room temperature and can even be used 24 hours after preparation for further application. Conclusion: Taken together, the TPP modified water soluble chitosan at concentration 0.5 % depicted the highest radiochemical yield (>95 %) at the optimized condition (pH= 6.2–7.6). Therefore, TPP modified water soluble chitosan can be an effective carrier for therapeutic radionuclides for tumor treatment.

Stimuli Responsive Materials Supported by Orthogonal Hydrogen and Halogen Bonding or I···Alkene Interaction

Smart materials represent an elegant class of (macro)-molecules endowed with the ability to react to chemical/physical changes in the environment. Herein, we prepared new photo responsive azobenzenes possessing halogen bond donor groups. The X-ray structures of two molecules highlight supramolecular organizations governed by unusual noncovalent bonds. In azo dye I-azo-NO2, the nitro group is engaged in orthogonal H···O···I halogen and hydrogen bonding, linking the units in parallel undulating chains. As far as compound I-azo-NH-MMA is concerned, a non-centrosymmetric pattern is formed due to a very rare I···π interaction involving the alkene group supplemented by hydrogen bonds. The Cambridge Structural Database contains only four structures showing the same I···CH2=C contact. For all compounds, an 19F-NMR spectroscopic analysis confirms the formation of halogen bonds in solution through a recognition process with chloride anion, and the reversible photo-responsiveness is demonstrated upon exposing a solution to UV light irradiation. Finally, the intermediate I–azo–NH2 also shows a pronounced color change due to pH variation. These azobenzenes are thereby attractive building blocks to design future multi-stimuli responsive materials for highly functional devices.

Carbon nano-dot for cancer studies as dual nano-sensor for imaging intracellular temperature or pH variation

Cellular temperature and pH govern many cellular physiologies, especially of cancer cells. Besides, attaining higher cellular temperature plays key role in therapeutic efficacy of hyperthermia treatment of cancer. This requires bio-compatible, non-toxic and sensitive probe with dual sensing ability to detect temperature and pH variations. In this regard, fluorescence based nano-sensors for cancer studies play an important role. Therefore, a facile green synthesis of orange carbon nano-dots (CND) with high quantum yield of 90% was achieved and its application as dual nano-sensor for imaging intracellular temperature and pH was explored. CND was synthesized from readily available, bio-compatible citric acid and rhodamine 6G hydrazide using solvent-free and simple heating technique requiring purification by dialysis. Although the particle size of 19 nm (which is quite large for CND) was observed yet CND exhibits no surface defects leading to decrease in photoluminescence (PL). On the contrary, very high fluorescence was observed along with good photo-stability. Temperature and pH dependent fluorescence studies show linearity in fluorescence intensity which was replicated in breast cancer cells. In addition, molecular nature of PL of CND was established using pH dependent fluorescence study. Together, the current investigation showed synthesis of highly fluorescent orange CND, which acts as a sensitive bio-imaging probe: an optical nano-thermal or nano-pH sensor for cancer-related studies.

Synthesis of the platinum particle with the pH variation for the particle size control

Platinum is a precious metal widely used in the jewelry industry due to its property and intrinsic value. The different particle sizes of platinum can be applied in various applications, especially for jewelry production. In the present article, submicron, and nano-sized platinum particle sizes were synthesized through simple chemical reduction methods and the effect of pH variation was revealed. The scanning electron microscope (SEM) images showed that the pH variations give rise to significant changes of the obtained particle size. The size of platinum particle was decreased from submicron to nanoscale while the pH was increased. The UV-Vis spectra indicated the maximum absorption at 220 nm confirming the spherical shape of the platinum particle. The FT-IR spectroscopy was used to analyze the residuals from the synthesis. The result showed that there is no indication of residual in the synthesized particle. Additionally, this synthesis can provide stability in terms of size and shape, as well as high production yield.

Molecular dynamics simulation study of doxorubicin adsorption on functionalized carbon nanotubes with folic acid and tryptophan

In this work, molecular dynamics (MD) simulation is used to study the adsorption of the anticancer drug, doxorubicin (DOX), on the wall or surface of pristine and functionalized carbon nanotubes (FCNTs) in an aqueous solution. Initially, the CNTs were functionalized by tryptophan (Trp) and folic acid (FA), and then the DOX molecules were added to the system. The simulation results showed that the drug molecules can intensely interact with the FCNTs at physiological pH. Furthermore, it was found that as a result of functionalization, the solubility of FCNTs in an aqueous solution increases significantly. The effect of pH variation on drug release from both pristine and FCNTs was also investigated. The obtained results indicated that in acidic environments due to protonation of functional groups (Trp) and as a result of repulsive interaction between the DOX molecule and functional groups, the release of DOX molecules from FCNT’s surface is facilitated. The drug release is also strongly dependent on the pH and protonated state of DOX and FCNT.

Possible effect of alkalization therapy on SARS-CoV-2 virus lifecycle

This proposal tries to drive attention to the observation that pH variation plays a fundamental role in the functional mechanism of SARS-CoV-2 virus proteases. Depending on this role, testing the effect of alkalization therapy on the SARS-CoV-2 patients could be reasonable.

Carbon Nanotubes Hybrid Hydrogels for Environmental Remediation: Evaluation of Adsorption Efficiency under Electric Field

The performance of Carbon Nanotubes hybrid hydrogels for environmental remediation was investigated using Methylene Blue (MB), Rhodamine B (RD), and Bengal Rose (BR) as model contaminating dyes. An acrylate hydrogel network with incorporated CNT was synthesized by photo-polymerization without any preliminary derivatization of CNT surface. Thermodynamics, isothermal and kinetic studies showed favorable sorption processes with the application of an external 12 V electric field found to be able to influence the amount of adsorbed dyes: stronger interactions with cationic MB molecules ( and of 19.72 and 33.45 mg g−1, respectively) and reduced affinity for anionic RD ( and of 28.93 and 13.06 mg g−1, respectively) and neutral BR ( and of 36.75 and 15.85 mg g−1, respectively) molecules were recorded. The influence of pH variation on dyes adsorption was finally highlighted by reusability studies, with the negligible variation of adsorption capacity after five repeated sorption cycles claiming for the suitability of the proposed systems as effective sorbent for wastewater treatment.