Phenothiazine-chitosan based eco-adsorbents: A special design for mercury removal and fast naked eye detection

Smart fluorescent polysaccharides: Recent developments and applications

Polysaccharides are ubiquitous, generally benign in nature, and compatible with many tissues in biomedical situations, making them appealing candidates for new materials such as therapeutic agents and sensors. Fluorescent labeling can create the ability to sensitively monitor distribution and transport of polysaccharide-based materials, which can for example further illuminate drug-delivery mechanisms and therefore improve design of delivery systems. Herein, we review fluorophore selection and ways of appending polysaccharides, utility of the product fluorescent polysaccharides as new smart materials, and their stimulus-responsive nature, with focus on their biomedical applications as environment-sensitive biosensors, imaging, and as molecular rulers. Further, we discuss the advantages and disadvantages of these methods, and future prospects for creation and use of these self-reporting materials.

Citryl-Imino-Chitosan Xerogels as Promising Materials for Mercury Recovery from Waste Waters

The present study reported the obtention of xerogels based on chitosan and citral and their use as materials for mercury ion recovery from aqueous solutions, this being a serious problem related to the environment. The systems were prepared by the acid condensation of chitosan with citral, followed by the lyophilization of the resulting hydrogels, in order to obtain highly porous solid materials. The structural, morphological and supramolecular characterization of the systems was performed using 1H-NMR and FTIR spectroscopy, scanning electron microscopy and wide-angle X-ray diffraction. The ability of the obtained materials to be used for the recovery of mercury from aqueous solutions revealed the high potential of the xerogels to be used in this sense, the analysis of the materials post mercury absorption experiments revealing that this ability is predominantly conferred by the imine linkages which act as coordinating moieties for mercury ions.

Theoretical and Experimental Aspects of Sodium Diclofenac Salt Release from Chitosan-Based Hydrogels and Possible Applications

Two formulations based on diclofenac sodium salt encapsulated into a chitosan hydrogel were designed and prepared, and their drug release was investigated by combining in vitro results with mathematical modeling. To understand how the pattern of drug encapsulation impacted its release, the formulations were supramolecularly and morphologically characterized by scanning electron microscopy and polarized light microscopy, respectively. The mechanism of diclofenac release was assessed by using a mathematical model based on the multifractal theory of motion. Various drug-delivery mechanisms, such as Fickian- and non-Fickian-type diffusion, were shown to be fundamental mechanisms. More precisely, in a case of multifractal one-dimensional drug diffusion in a controlled-release polymer-drug system (i.e., in the form of a plane with a certain thickness), a solution that allowed the model's validation through the obtained experimental data was established. The present research reveals possible new perspectives, for example in the prevention of intrauterine adhesions occurring through endometrial inflammation and other pathologies with an inflammatory mechanism background, such as periodontal diseases, and also therapeutic potential beyond the anti-inflammatory action of diclofenac as an anticancer agent, with a role in cell cycle regulation and apoptosis, using this type of drug-delivery system.

Outstanding Sorption of Copper (II) Ions on Porous Phenothiazine-Imine-Chitosan Materials

The aim of this work was to investigate the ability of a solid-state material, prepared by crosslinking chitosan with a phenothiazine-based aldehyde, to remove copper (II) ions from aqueous solutions, in a fast and selective manner. The metal uptake experiments, including the retention, sensibility, and selectivity against eight different metal ions, were realized via batch adsorption studies. The capacity of the material to retain copper (II) ions was investigated by spectrophotometric measurements, using poly(ethyleneimine) complexation agent, which allowed detection in a concentration range of 5-500 µM. The forces driving the copper sorption were monitored using various methods, such as FTIR spectroscopy, X-ray diffraction, SEM-EDAX technique, and optical polarized microscopy, and the adsorption kinetics were assessed by fitting the in vitro sorption data on different mathematical models. The phenothiazine-imine-chitosan material proved high ability to recover copper from aqueous media, reaching a maximum retention capacity of 4.394 g Cu (II)/g adsorbent when using a 0.5 M copper solution, which is an outstanding value compared to other chitosan-based materials reported in the literature to this date. It was concluded that the high ability of the studied xerogel to retain Cu (II) ions was the result of both physio- and chemo-sorption processes. This particular behavior was favored on one hand by the porous nature of the material and on the other hand by the presence of amine, hydroxyl, imine, and amide groups with the role of copper ligands.

TEGylated Phenothiazine-Imine-Chitosan Materials as a Promising Framework for Mercury Recovery

This paper reports new solid materials based on TEGylated phenothiazine and chitosan, with a high capacity to recover mercury ions from aqueous solutions. They were prepared by hydrogelation of chitosan with a formyl derivative of TEGylated phenothiazine, followed by lyophilization. Their structural and supramolecular characterization was carried out by 1H-NMR and FTIR spectroscopy, as well as X-ray diffraction and polarized light microscopy. Their morphology was investigated by scanning electron microscopy and their photophysical behaviour was examined by UV/Vis and emission spectroscopy. Swelling evaluation in different aqueous media indicated the key role played by the supramolecular organization for their hydrolytic stability. Mercury recovery experiments and the analysis of the resulting materials by X-ray diffraction and FTIR spectroscopy showed a high ability of the studied materials to bind mercury ions by coordination with the sulfur atom of phenothiazine, imine linkage, and amine units of chitosan.

Facile method to synthesize fluorescent chitosan hydrogels for selective detection and adsorption of Hg2+/Hg. Carbohydr Polym 2022;288:119417. [PMID: 35450660 DOI: 10.1016/j.carbpol.2022.119417]

Fluorescent chitosan-based hydrogel for the selective detection and adsorption of Hg²⁺/Hg⁺ in aqueous environment was prepared through three-step synthesis strategy. NO₂-Boron-dipyrrolemethene (BODIPY) was prepared firstly, and then the -NO₂ group was reduced to -NH₂ group. Finally, the NH₂-BODIPY was introduced to chitosan by Schiff base formation reaction through bi-aldehyde. Eventually, fluorescent chitosan hydrogel was obtained. The as-prepared fluorescent hydrogel probe could detect Hg²⁺/Hg⁺ through PET mechanism with the detection limit of 0.3 μM. The recognition site which combines Hg²⁺/Hg⁺ is CN, it is just formed in the reaction with chitosan and the amino group on BODIPY. Adsorption capacity of the fluorescent hydrogel is 121 mg·g^-1, which is almost seven times of the original chitosan. The isotherm and kinetics of Hg²⁺/Hg⁺ removal follows Langmuir isotherm and pseudo-second order kinetics, respectively. Besides, a series of fluorescent hydrogels were prepared to compare the elasticity, hydropHilicity, fluorescence intensity and adsorption capacity.

Self-Healing Chitosan Hydrogels: Preparation and Rheological Characterization

The paper aims at the preparation of chitosan self-healing hydrogels, designed as carriers for local drug delivery by parenteral administration. To this aim, 30 hydrogels were prepared using chitosan and pyridoxal 5-phosphate (P5P), the active form of vitamin B6 as precursors, by varying the ratio of glucosamine units and aldehyde on the one hand and the water content on the other hand. The driving forces of hydrogelation were investigated by nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, and polarized light microscopy (POM) measurements. NMR technique was also used to investigate the stability of hydrogels over time, and their morphological particularities were assessed by scanning electron microscopy (SEM). Degradability of the hydrogels was studied in media of four different pH, and preliminary self-healing ability was visually established by injection through a syringe needle. In-depth rheological investigation was conducted in order to monitor the storage and loss moduli, linear viscoelastic regime, and structural recovery capacity. It was concluded that chitosan crosslinking with pyridoxal 5-phosphate is a suitable route to reach self-healing hydrogels with a good balance of mechanical properties/structural recovery, good stability over time, and degradability controlled by pH.

Chitosan crosslinking with a vanillin isomer toward self-healing hydrogels with antifungal activity

The purpose of the study was to develop new antimicrobial hydrogels from natural resources that may promote wound healing and prevent bacterial skin infection. The new hydrogels were synthesized by crosslinking chitosan with a vanillin isomer, 5-methoxysalicylaldehyde, by a friendly and easy method. To characterize these hydrogels, their structural and morphological properties were explored by FTIR, ¹H NMR, SEM, POM, and TGA. In view of the targeted application, swelling behavior, biodegradability, antimicrobial activity and biocompatibility were investigated in vitro. Structural and morphological studies confirmed the formation of new hydrogels via the imination reaction concomitant with the supramolecular organization. The hydrogels were highly porous with the average pore diameter around 80 μm, and a swelling rate controlled by the crosslinking density and medium pH. The hydrogels showed a progressive weight loss in the presence of lysozyme up to 35%, during 21 days of testing. They proved non-cytotoxic effect on Normal Human Dermal Fibroblasts using MTS test and powerful antifungal activity against Candida Albicans, as determined by disk diffusion assay. All these properties indicate the new hydrogels as a promising option for the treatment of various skin lesions.

Amphiphilic chitosan-g-poly(trimethylene carbonate) - A new approach for biomaterials design

The paper presents the synthesis and characterization of poly(trimethylene carbonate) grafted chitosan as a new water soluble biopolymer suitable for in vivo applications. The synthesis was performed via ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) (TMC) monomer, initiated by the functional groups of chitosan in the presence of toluene as solvent/swelling agent. By varying the molar ratio between the glucosamine units of chitosan and TMC, a series of chitosan derivatives with different content of poly(trimethylene carbonate) chains was synthetized. The structural characterization of the polymers was realized by FTIR and ¹H NMR spectroscopy and their solubility was assessed in water and in organic solvents as well. The biocompatibility was investigated by MTS assay on Normal Human Dermal Fibroblasts, and the biodegradability was evaluated in lysozyme buffer solution. Further, the surface properties of the polymer films were analyzed by polarized optical microscopy, atomic force microscopy and water-to-air contact angle measurements. It was established that, by 5% substitution of chitosan with poly(trimethylene carbonate) chains having an average polymerization degree of 7, a water soluble polymer can be attained. Compared to the pristine chitosan, it has improved biocompatibility in solution and moderate wettability and higher biodegradability rate in solid state, pointing its suitability for in vivo applications.

Chitosan crosslinking with pyridoxal 5-phosphate vitamer toward biocompatible hydrogels for in vivo applications

Vitamin B6 is an essential micronutrient in the mammalian diet, with role of coenzyme and synergistic effect with some antibiotics and antitumor drugs. Based on these, we hypothesized that its use for the preparation of hydrogels can yield multifunctional biomaterials suitable for in vivo applications. To this aim, chitosan was reacted with the active form of vitamin B6, pyridoxal 5-phosphate, via acid condensation, when clear hydrogels were obtained. Their investigation by structural characterization methods proved that the hydrogelation was a consequence of both covalent imine formation and physical interactions. The novel hydrogels had microporous morphology and showed shrinking effect in phosphate buffer, indicating good shape preservation and slow dissolution in in vivo environment. Their enzymatic biodegradation could be controlled by the imination degree, varying from 40 to 61% in 21 days. They demonstrated very good in vitro cytocompatibility on normal human dermal fibroblasts cells and no harmful effect on experimental mice, confirming their safely use for in vivo application.

Electrospinning of chitosan-based nanofibers: from design to prospective applications

Chitosan is a biopolymer originating from renewable resources, with great properties which make it an attractive candidate for plenty of applications of contemporary interest. By manufacturing chitosan into nanofibers using the electrospinning method, its potential is amplified due to the enhancement of the active surface and the low preparation cost. Many attempts were made with the aim of preparing chitosan-based nanofibers with controlled morphology targeting their use for tissue engineering, wound healing, food packaging, drug delivery, air and water purification filters. This was a challenging task, which resulted in a high amount of data, sometimes with apparent contradictory results. In this light, the goal of the paper is to present the main routes reported in the literature for chitosan electrospinning, stressing the advantages and disadvantages of each of them. Special emphasis is placed on the influence of various electrospinning parameters on the morphological characteristics of the fibers and their suitability for distinct applications.

Pegylation of phenothiazine – A synthetic route towards potent anticancer drugs

•

Antitumor activity of two PEGylated phenotiazines was investigated

•

The compounds showed cytotoxic activity against six tumor lines

•

They inhibited the tumor growth in experimental mice

•

The PEGylation improved the phenothiazine biocompatibility

•

A synergistic effect of PEG and phenothiazine toward properties improvement was proved

Introduction

Cancer is a big challenge of the 21 century, whose defeat requires efficient antitumor drugs.

Objectives

The paper aims to investigate the synergistic effect of two structural building blocks, phenothiazine and poly(ethylene glycol), towards efficient antitumor drugs.

Methods

Two PEGylated phenothiazine derivatives were synthetized by attaching poly(ethylene glycol) of 550 Da to the nitrogen atom of phenothiazine by ether or ester linkage. Their antitumor activity has been investigated on five human tumour lines and a mouse tumor line as well, by determination of IC50. The in vivo toxicity was determined by measuring the LD50 in BALB/c mice by the sequential method and the in vivo antitumor potential was measured by the tumours growth test. The antitumor mechanism was investigated by complexation studies of zinc and magnesium ions characteristic to the farnesyltransferase enzyme, by studies of self-aggregation in the cells proximity and by investigation of the antitumor properties of the acid species resulted by enzymatic cleavage of the PEGylated derivatives.

Results

The two compounds showed antitumor activity, with IC50 against mouse colon carcinoma cell line comparable with that of the traditional antitumor drugs 5-Fluorouracil and doxorubicin. The phenothiazine PEGylation resulted in a significant toxicity diminishing, the LD50 in BALB/c mice increasing from 952.38 up to 1450 mg/kg, in phenothiazine equivalents. Both compounds inflicted a 92% inhibition of the tumour growth for doses much smaller than LD50. The investigation of the possible tumour inhibition mechanism suggested the nanoaggregate formation and the cleavage of ester bonds as key factors for the inhibition of cancer cell proliferation and biocompatibility improvement.

Conclusion

Phenothiazine and PEG building blocks have a synergetic effect working for both tumour growth inhibition and biocompatibility improvement. All these findings recommend the PEGylated phenothiazine derivatives as a valuable workbench for a next generation of antitumor drugs.

A Theoretical Model for Release Dynamics of an Antifungal Agent Covalently Bonded to the Chitosan

The aim of the study was to create a mathematical model useful for monitoring the release of bioactive aldehydes covalently bonded to the chitosan by reversible imine linkage, considered as a polymer-drug system. For this purpose, two hydrogels were prepared by the acid condensation reaction of chitosan with the antifungal 2-formyl-phenyl-boronic acid and their particularities; influencing the release of the antifungal aldehyde by shifting the imination equilibrium to the reagents was considered, i.e., the supramolecular nature of the hydrogels was highlighted by polarized light microscopy, while scanning electron microscopy showed their microporous morphology. Furthermore, the in vitro fungicidal activity was investigated on two fungal strains and the in vitro release curves of the antifungal aldehyde triggered by the pH stimulus were drawn. The theoretical model was developed starting from the hypothesis that the imine-chitosan system, both structurally and functionally, can be assimilated, from a mathematical point of view, with a multifractal object, and its dynamics were analyzed in the framework of the Scale Relativity Theory. Thus, through Riccati-type gauges, two synchronous dynamics, one in the scale space, associated with the fungicidal activity, and the other in the usual space, associated with the antifungal aldehyde release, become operational. Their synchronicity, reducible to the isomorphism of two SL(2R)-type groups, implies, by means of its joint invariant functions, bioactive aldehyde compound release dynamics in the form of "kink-antikink pairs" dynamics of a multifractal type. Finally, the theoretical model was validated through the experimental data.