The evolution of the global COVID-19 epidemic in Morocco and understanding the different therapeutic approaches of chitosan in the control of the pandemic.

In 2020, Coronavirus disease (COVID-19), a new viral respiratory disease caused by a virus that belongs to Coronaviridae family, has been identified. It is a very severe flu that negatively affects the functions of the lung and other respiratory organs. COVID-19 virus can be transmitted between people either by touching an infected person or by direct contact with their respiratory droplets. Therefore, the COVID-19 virus has become a global concern due to its rapid spread and severity. Based on the World Health Organization report from 2 March 2020 to 24 October 2022, the total infected cases and deaths in Morocco are around 1,265,389 (3.46%) and 16,280 (0.04%), respectively. Recently, some scientists have found that chitosan, a polymer existed in nature, can inhibit COVID-19 infection and repair damaged tissue. Therefore, understanding chitosan mechanisms in controlling COVID-19, might lead to innovative strategies in the medical field, such as developing drugs against SARS-CoV-2, and replacing vaccines, which have negative side effects. This review aims to show the evolution of the COVID-19 pandemic worldwide, specifically in Morocco, its pathophysiology, and its ability to silence the immune system. This review also provides an overview of the treatments and measures applied to protect human beings and how chitosan acts and controls COVID-19.

Structural Characterization and Rheological and Antioxidant Properties of Novel Polysaccharide from Calcareous Red Seaweed.

A novel sulfated xylogalactan (JASX) was extracted and purified from the rhodophyceae Jania adhaerens. JASX was characterized by chromatography (GC/MS-EI and SEC/MALLS) and spectroscopy (ATR-FTIR and 1H/13C NMR) techniques. Results showed that JASX was constituted by repeating units of (→3)-ß-d-Galp-(1,4)-3,6-α-l-AnGalp-(1→)n and (→3)-ß-d-Galp-(1,4)-α-l-Galp-(1→)n substituted on O-2 and O-3 of the α-(1,4)-l-Galp units by methoxy and/or sulfate groups but also on O-6 of the ß-(1,3)-d-Galp mainly by ß-xylosyl side chains and less by methoxy and/or sulfate groups. The Mw, Mn, D, [η] and C* of JASX were respectively 600 and 160 kDa, 3.7, 102 mL.g-1 and 7.0 g.L-1. JASX exhibited pseudoplastic behavior influenced by temperature and monovalent salts and highly correlated to the power-law model and the Arrhenius relationship. JASX presented thixotropic characteristics, a gel-like viscoelastic behavior and a great viscoelasticity character. JASX showed important antioxidant activities, outlining its potential as a natural additive to produce functional foods.

Immobilization and Release Studies of Triazole Derivatives from Grafted Copolymer Based on Gellan-Carrying Betaine Units.

New polymer-bioactive compound systems were obtained by immobilization of triazole derivatives onto grafted copolymers and grafted copolymers carrying betaine units based on gellan and N-vinylimidazole. For preparation of bioactive compound, two new types of heterocyclic thio-derivatives with different substituents were combined in a single molecule to increase the selectivity of the biological action. The 5-aryl-amino-1,3,4 thiadiazole and 5-mercapto-1,2,4-triazole derivatives, each containing 2-mercapto-benzoxazole nucleus, were prepared by an intramolecular cyclization of thiosemicarbazides-1,4 disubstituted in acidic and basic medium. The structures of the new bioactive compounds were confirmed by elemental and spectral analysis (FT-IR and 1H-NMR). The antimicrobial activity of 1,3,4 thiadiazoles and 1,2,4 triazoles was tested on gram-positive and gram-negative bacteria. The triazole compound was chosen to be immobilized onto polymeric particles by adsorption. The Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherm were used to describe the adsorption equilibrium. Also, the pseudo-first and pseudo-second models were used to elucidate the adsorption mechanism of triazole onto grafted copolymer based on N-vinylimidazole and gellan (PG copolymer) and grafted copolymers carrying betaine units (PGB1 copolymer). In vitro release studies have shown that the release mechanism of triazole from PG and PGB1 copolymers is characteristic of an anomalous transport mechanism.

The Benefits of Smart Nanoparticles in Dental Applications.

Dentistry, as a branch of medicine, has undergone continuous evolution over time. The scientific world has focused its attention on the development of new methods and materials with improved properties that meet the needs of patients. For this purpose, the replacement of so-called "passive" dental materials that do not interact with the oral environment with "smart/intelligent" materials that have the capability to change their shape, color, or size in response to an externally stimulus, such as the temperature, pH, light, moisture, stress, electric or magnetic fields, and chemical compounds, has received much attention in recent years. A strong trend in dental applications is to apply nanotechnology and smart nanomaterials such as nanoclays, nanofibers, nanocomposites, nanobubbles, nanocapsules, solid-lipid nanoparticles, nanospheres, metallic nanoparticles, nanotubes, and nanocrystals. Among the nanomaterials, the smart nanoparticles present several advantages compared to other materials, creating the possibility to use them in various dental applications, including preventive dentistry, endodontics, restoration, and periodontal diseases. This review is focused on the recent developments and dental applications (drug delivery systems and restoration materials) of smart nanoparticles.

New Grafted Copolymers Carrying Betaine Units Based on Gellan and N-Vinylimidazole as Precursors for Design of Drug Delivery Systems.

New grafted copolymers possessing structural units of 1-vinyl-3-(1-carboxymethyl) imidazolium betaine were obtained by graft copolymerization of N-vinylimidazole onto gellan gum followed by the polymer-analogous reactions on grafted polymer with the highest grafting percentage using sodium chloroacetate as the betainization agent. The grafted copolymers were prepared using ammonium persulfate/N,N,N',N' tetramethylethylenediamine in a nitrogen atmosphere. The grafting reaction conditions were optimized by changing one of the following reaction parameters: initiator concentration, monomer concentration, polymer concentration, reaction time or temperature, while the other parameters remained constant. The highest grafting yield was obtained under the following reaction conditions: ci = 0.08 mol/L, cm = 0.8 mol/L, cp = 8 g/L, tr = 4 h and T = 50 °C. The kinetics of the graft copolymerization of N-vinylimidazole onto gellan was discussed and a suitable reaction mechanism was proposed. The evidence of the grafting reaction was confirmed through FTIR spectroscopy, X-ray diffraction, 1H-NMR spectroscopy and scanning electron microscopy. The grafted copolymer with betaine structure was obtained by a nucleophilic substitution reaction where the betainization agent was sodium chloroacetate. Preliminary results prove the ability of the grafted copolymers to bind amphoteric drugs (cefotaxime) and, therefore, the possibility of developing the new sustained drug release systems.

Structural features and rheological behavior of a water-soluble polysaccharide extracted from the seeds of Plantago ciliata Desf.

A water-soluble polysaccharide (PSPC) was extracted from the seeds of Plantago ciliata Desf., a spontaneous Algerian Saharan plant by a hot aqueous extraction then purified by successive ethanolic precipitations. The final extraction yield for PSPC was close to 18.6% (w/v). PSPC was then investigated regarding its global composition, structural features and rheological properties. PSPC is a neutral arabinoxylan, composed of a ß-(1,3)/ß-(1,4)-d-xylan backbone with side chains of Xylp, and Araf residues attached in O-2 and O-3 positions. The macromolecular characteristics of PSPC in water was determined by SEC/MALLS, with a high molecular weight (Mw) of 700 kDa, a low polydispersity index (PDI) of 1.47 and an intrinsic viscosity [η] close to 157 mL/g. PSPC showed a pseudoplastic behavior in semi-dilute media and the critical overlay concentration (C*) was estimated around 0.32-0.37% (w/v). This current research has supplied original structural information on a new arabinoxylan which could be particularly useful as a novel source of soluble fiber belonging to psyllium.

New highly-percolating alginate-PEI membranes for efficient recovery of chromium from aqueous solutions.

Highly percolating membranes are prepared by the interaction of polyethylenimine and alginate (with glutaraldehyde crosslinking). SEM illustrates the macroporous structure of the material. The material is characterized by FTIR before and after chromate anions sorption. Batch-simulated continuous sorption experiments revealed that the maximum sorption occurred at pH 2 and the flow rate has limited effect on sorption efficiency. Uptake kinetics and sorption isotherms are well fitted by the pseudo-second-order rate and Sips equations, respectively. Maximum sorption is found close to 314 mg g-1. Competition effects from Ca(II), Cu(II), Cl-, NO3-, and SO42- are investigated to evaluate sorbent selectivity. The membranes are applied to remediate a simulate of Cr(VI) contaminated electroplating wastewater. Successive cycles of sorption and desorption show that the membranes maintain sorption capacity higher than 200 mg Cr g-1 for both Cr(VI) and total chromium for the first two cycles. These new highly percolating membranes have promising performances for Cr(VI) removal.

Alkyl-Chitosan-Based Adhesive: Water Resistance Improvement.

A chemical modification by grafting alkyl chains using an octanal (C8) on chitosan was conducted with the aim to improve its water resistance for bonding applications. The chemical structure of the modified polymers was determined by NMR analyses revealing two alkylation degrees (10 and 15%). In this study, the flow properties of alkyl-chitosans were also evaluated. An increase in the viscosity was observed in alkyl-chitosan solutions compared with solutions of the same concentration based on native chitosan. Moreover, the evaluation of the adhesive strength (bond strength and shear stress) of both native and alkyl-chitosans was performed on two different double-lap adherends (aluminum and wood). Alkyl-chitosans (10 and 15%) maintain sufficient adhesive properties on wood and exhibit better water resistance compared to native chitosan.

Structural characterization and antioxidant activity of water-soluble polysaccharides from the Tunisian brown seaweed Cystoseira compressa.

A fucoidan (CCF) and a sodium alginate (CCSA) were extracted and purified from the Tunisian brown seaweed Cystoseira compressa. CCF was a highly sulfated heterogalactofucan composed of α-(1→3), α-(1→4)-linked l-Fucp as main backbone which could be highly branched (31.84%) at O-3 and O-4 positions of α-(1→4)-l-Fucp and α-(1→3)-l-Fucp by terminal monosaccharides and side chains such as terminal α-l-Fucp, terminal ß-d-Galp, ß-d-Galp-(1→3)-α-l-Fucp and ß-d-Galp-(1→4)-α-l-Fucp. The ratio of α-(1→3)/α-(1→4) linkages was estimated at 3.86:1. CCSA was characterized by HPAEC-PAD, GC/MS-EI, ATR-FTIR, and 1H-NMR. The M/G ratio was M/G = 0.77, indicating that CCSA respectively contained 44% and 56% of mannuronic and guluronic acids. The values of FGG, FMM, FGM (or FMG) blocks as well as the parameter η were estimated. The two polysaccharides exhibited effective antioxidant activities by ferrous ion chelation, ferric ion reduction and DPPH radical-scavenging, outlining their potentials as natural additives.

Extraction and characterization of an alginate from the Iranian brown seaweed Nizimuddinia zanardini.

Sodium alginate from Nizimuddinia zanardini (an Iranian brown algae) was extracted with acid and alkaline solutions, partially and totally hydrolyzed and analyzed for its biochemical composition. 1H NMR spectroscopy, SEC-MALLS, HPAEC and FT-IR were performed to determine its structure and its physico-chemical properties. This alginate has a M/G ratio of 1.1, a molecular weight of 103 kDa, a polydispersity index of 1.22, and an intrinsic viscosity of 342 mL/g. Its antioxidant activity was tested by DPPH radical scavenging showing its potential for food preservation. Rheological properties of solutions of this alginate with concentrations between 1 and 5% (w/v) in water and 0.5 M NaCl were investigated indicating a Newtonian fluid type behaviour in water and a shear thinning fluid type behaviour in NaCl solutions.

Improvement of chitosan solubility and bactericidity by synthesis of N-benzimidazole-O-acetyl-chitosan and its electrodeposition.

Chitosan solubility and its antibacterial activity have been improved first of all with a chemical synthesis of N-benzimidazole-O-acetyl-chitosan in acetic medium and foremost through a potentiodynamic electrodeposition of this derivative. An association of one benzimidazole and three acetyl moieties per two units of the biopolymer chain was evidenced by FTIR and 1H NMR, pH-metric titration and TG analysis. Cyclic voltammetry study of the modified polymer in acetonitrile solution reveals its anodic oxidation at a platinum disk and a progressive growing of a thin film, through the cycling of potential. An enhancement of the solubility of the biopolymer as well as its antibacterial activity against Salmonella typhimurium, Escherichia coli, Staphylococcus aureus and Pseudomoenas aeruginosa bacteria have been observed with these chemical and after electrochemical modifications.

Structural characterization and thermal behavior of a gum extracted from Ferula assa foetida L.

The gum asafoetida, an oleo-gum-resin from root of Ferula assa foetida, was extracted through alcoholic procedure followed by water extraction and then biochemically characterized using colorimetric assays, Fourier infrared spectroscopy, gas chromatography coupled to mass spectrometry, and 1D and 2D nuclear magnetic resonance. The gum was mainly composed of carbohydrates (67.39% w/w) with a monosaccharide distribution of 11.5: 5.9: 2.3: 1 between Gal, Ara, Rha and GlcA (molar ratio) and proteins (arabinogalactan protein). The polysaccharide consisted of a (1→3)-ß-d-galactan backbone ramified predominantly from O-6 but also from O-4 and O-4,6. Side chains included terminal-α-l-Araf, terminal-α-l-Rhap, (1→3)-α-l-Araf, (1→5)-α-l-Araf, terminal-ß-d-Galp, ß-d-GlcA and traces of (1→4)-ß-d-GlcA. X-ray diffraction pattern showed a semi crystalline microstructure. Thermal behavior of the gum was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed temperatures below and upper 200°C as dominant regions of weight loss.

Dilational rheology of oil/water interfaces covered by amphiphilic polysaccharides derived from dextran.

This work studied the adsorption at dodecane/water interface of amphiphilic polysaccharides derived from dextran (a nonionic bacterial polysaccharide) by random attachment of phenoxy groups along the chains (between 10 and 20 attached phenoxy groups per 100 glucose repeat units). The long-time kinetics of interfacial tension decrease was satisfactorily described assuming diffusion-limited adsorption of hydrophobic units (over 4h). Dilational rheology of dodecane/water interface was studied for the first time with that kind of amphiphilic polysaccharides and evidenced a significant elastic component. For all dextran derivatives, experimental results were conveniently described using Lucassen-van den Tempel model which assumed diffusion-limited of surface active species. The characteristic frequency increased with the number of attached phenoxy groups and its order of magnitude (10-3-10-2rad.s-1) was consistent with estimations based on the previous model. Experimental results were compared to those obtained with commercial stabilizers like Pluronics (L64, P105, F68 and F127) and Tween 80.

The extracellular matrix of the oleolytic biofilms of Marinobacter hydrocarbonoclasticus comprises cytoplasmic proteins and T2SS effectors that promote growth on hydrocarbons and lipids.

The assimilation of the nearly water insoluble substrates hydrocarbons and lipids by bacteria entails specific adaptations such as the formation of oleolytic biofilms. The present article reports that the extracellular matrix of an oleolytic biofilm formed by Marinobacter hydrocarbonoclasticus at n-hexadecane-water interfaces is largely composed of proteins typically cytoplasmic such as translation factors and chaperones, and a lesser amount of proteins of unknown function that are predicted extra-cytoplasmic. Matrix proteins appear to form a structured film on hydrophobic interfaces and were found mandatory for the development of biofilms on lipids, alkanes and polystyrene. Exo-proteins secreted through the type-2 secretion system (T2SS) were shown to be essential for the formation of oleolytic biofilms on both alkanes and triglycerides. The T2SS effector involved in biofilm formation on triglycerides was identified as a lipase. In the case of biofilm formation on n-hexadecane, the T2SS effector is likely involved in the mass transfer, capture or transport of alkanes. We propose that M. hydrocarbonoclasticus uses cytoplasmic proteins released by cell lysis to form a proteinaceous matrix and dedicated proteins secreted through the T2SS to act specifically in the assimilation pathways of hydrophobic substrates.

Interactions between quaternized chitosan and surfactant studied by diffusion NMR and conductivity.

Surfactant-polysaccharide complexes (SPEC) based on oppositely charged sodium 1-decanesulfonate and quaternized chitosan were studied using two techniques. The first one, the conductivity, is a very often used even when diffusion NMR (DOSY) technique was considered for the first time for such systems involving surfactant and chitosan derivatives and more generally polysaccharides. The physico-chemical characteristics of pure surfactant solutions as well as SPECs were determined and compared according to the considered experimental technique. Close results were obtained and the great advantage of DOSY technique is the capacity to study simultaneously the two components of the systems, allowing more information on the nature of interactions between the surfactant and the polysaccharide as well as the mechanism involved during these interactions. This may be of great interest to understand how these complexes can alter the properties of formulations in which these components are involved, which is one of the big challenges of the industrial research.

New hybrid magnetic nanoparticles based on chitosan-maltose derivative for antitumor drug delivery.

The aim of the present study is to obtain, for the first time, polymer magnetic nanoparticles based on the chitosan-maltose derivative and magnetite. By chemically modifying the chitosan, its solubility in aqueous media was improved, which in turn facilitates the nanoparticles' preparation. Resulting polymers exhibit enhanced hydrophilia, which is an important factor in increasing the retention time of nanoparticles in the blood flow. The preparation of nanoparticles relied on the double crosslinking technique (ionic and covalent) in reverse emulsion which ensures the mechanical stability of the polymer carrier. The characterization of both the chitosan derivative and nanoparticles was accomplished by Fourier Transform Infrared Spectroscopy, Nuclear Magnetic Resonance Spectroscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Atomic Force Microscopy, Vibrating Sample Magnetometry, and Thermogravimetric Analysis. The evaluation of morphological, dimensional, structural, and magnetical properties, as well as thermal stability and swelling behavior of nanoparticles was made from the point of view of the polymer/magnetite ratio. The study of 5-Fluorouracil loading and release kinetics as well as evaluating the cytotoxicity and hemocompatibility of nanoparticles justify their adequate behavior in their potential use as devices for targeted transport of antitumor drugs.

Formulation and evaluation of cefuroxim loaded submicron particles for ophthalmic delivery.

Chitosan gelatin particles could be the ideal candidate for intraocular drug delivery due to their desirable properties. Double crosslinking in double emulsion has been used as an original and reliable method for particles preparation and their morphology has been optimized considering the main synthesis parameters such as polymers ratio, crosslinker amount, stirring speed, tensioactive amount and ionic crosslinking time, respectively. The particles have been analyzed for their physical-chemical properties (swelling degree, drug loading and release capacity, surface characteristics, etc.), the enzymatic degradation properties along with in vivo ocular investigations (ocular biodistribution, in vivo drug release). In the present study cefuroxim was used as a model drug, which is generally used in the prophylaxis of postoperative endophthalmitis following cataract surgery after intraocular administration. The present study proved that the dimensions and the physical-chemical properties of the particles can be modulated (by varying the preparation parameters) to facilitate the administration, the biodistribution and the drug release in the specific segment of the eye. This experimental study demonstrated also the ability of fluorescent nanoparticles to penetrate ocular tissues close to the administration site (intravitreal injection) and especially their tendency to migrate deep in the retina at time intervals of 72 h.

Surface characterization and drug release from porous microparticles based on methacrylic monomers and xanthan.

Porous crosslinked microparticles based on glycidyl methacrylate and xanthan were prepared by suspension polymerization and used for loading theophylline, a bronhodilatator drug, in order to obtain new drug delivery systems. The surface morphologies observed by means of SEM and AFM analysis demonstrated that microparticles show a spherical shape and are characterized by a porous structure. The presence of xanthan in the structure of microparticles leads to a decrease of surface roughness and pore diameters as well as to an increase of hydrophilicity degree compared to the micropaticles based only on glycidyl methacrylate. To analyze the in vitro release data various mathematical models were used, such as, first order, Higuchi model, Korsmeyer-Peppas model and Baker-Lonsdale model. Based on the highest values of the correlation coefficient, the analysis of the kinetic data indicate that drug release from G1 and X1 porous microparticles fits similarly well to the first order and Higuchi models and diffusion was the dominant mechanism of drug release.

Modulated release from liposomes entrapped in chitosan/gelatin hydrogels.

The paper describes the preparation of chitosan/gelatin hydrogels, obtained by double crosslinking with glutaraldehyde and sodium sulphate/sodium tripolyphosphate that may be used as matrices for the inclusion of drug loaded liposomes composed of phosphatidylcholine. The main objective was to create a protective layer to stabilize the liposomal surface and to prolong/control the release of drugs from such systems. Therefore, complex systems capable of prolonged drug release and controlled release kinetics were obtained. Samples consisting of different chitosan/gelatin ratios and type/amount of ionic crosslinker have been prepared and characterized. The present study shows that calcein (used as a model hydrophilic drug) release from polymeric hydrogels has been retarded from several days to weeks after calcein inclusion in small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs) entrapped subsequently in hydrogels with variable composition. The calcein release kinetics of complex systems were compared to simple systems (control hydrogels) and important changes were observed thus proving that the mechanism of the process increases in complexity. Also, it is demonstrated that liposomes' stability can be greatly improved by inclusion in polymeric matrices. Multilamellar liposomes showed a better release behaviour, which indicates that these calcein loaded vesicles remained intact to some extent after release from the matrix, due to their improved stability provided by the multiple layers. When small unilamellar liposomes were tested, calcein have been released from hydrogels predominantly in a free form (due to their unilamellarity related instability even inside the hydrogel) but in a sustained and controllable manner. The main applications of the systems obtained are in the area of drug release for tissue engineering/tissue repair (topical administration of drugs for wound therapy - burns, for example). Hydrogels capable of delivering drugs over prolonged periods of time represent a step forward in wound management and many diseases that request long term and sustained delivery of drugs. These hydrogels could be used as tissue replacement or injectable depot systems in many high risk diseases including cancer.

Property peculiarities of the atelocollagen-hyaluronan conjugates crosslinked with a short chain di-oxirane compound.

Minimal amounts of a short-chain bifunctional crosslinker of about 1.3 nm length, the 1,4-butanediol-diglycidyl ether (BDDGE), were used to generate atelocollagen-hyaluronan conjugates in hydrogel state. Two a priori constraints were considered in recipe/procedure developing: (i) working in nondenaturing conditions, and (ii) ensuring a low cytotoxicity of the final product. Both atelocollagen (aK) and hyaluronan (NaHyal) were accurately purified to reduce their molecular-weight dispersity, in order to ensure the reproducibility of hydrogels characteristics. 1:5 aK:NaHyal weight ratios and 1:2.5 to 1:5 α-NH2:BDDGE molar ratios were found to be the most favorable recipe prescriptions that allow the obtaining of rheo-mechanically stable hydrogels, able to be manipulated during cell culturing protocols. Experiments revealed two unexpected effects due to the crosslinking reactions mediated by a short-chain molecule: (i) the occurrence of two thresholds in the rheological behavior of the hydrogels, related with the amount of added crosslinker, and (ii) a quasi-denaturation side-effect induced over the protein component by large or in excess amounts of crosslinker.