S-scheme heterojunctions based on novel Sm2CeMnO6 double perovskite oxide and g-C3N4 with excellent photocatalytic dye degradation performances.

It has become of utmost importance to preserve marine life and human health by protecting aquatic environments from contaminants. Therefore, using photocatalytic materials in treatment of contaminated water is a promising and innovative technique. Novel double perovskite Sm2CeMnO6 was synthesized through a modified Pechini sol-gel method. Also, urea and melamine were utilized to synthesize graphitic carbon nitride (g-C3N4). Combination of Sm2CeMnO6 and g-C3N4 produced several S-scheme heterojunction materials in diverse components ratios. Average crystallite sizes of Sm2CeMnO6 and Sm2CeMnO6/g-C3N4 (20:80) samples were calculated by Debye-Scherrer and Williamson-Hall methods to be 19.77, 22.72 nm and 42.01, 43.73 nm, respectively. The coexistence of g-C3N4 (002) with a d-spacing of 0.325 nm and Sm2CeMnO6 planes of (222), (111), and (400) with spacing values of 0.314, 0.302, and 0.294 nm, respectively, was depicted in the HR-TEM image of the Sm2CeMnO6/g-C3N4 (20:80). The estimated bandgaps for the g-C3N4, Sm2CeMnO6, and Sm2CeMnO6/g-C3N4 (20:80) were 2.70, 2.60, and 2.65 eV, respectively. Their application was investigated in photocatalytic degradation of methylene blue (MB) dye as typical pollutant. The estimated degradation pathway of MB was also provided through LC-MS analysis. Under the identical conditions, the best photocatalytic performance was found for Sm2CeMnO6/g-C3N4 (20:80) composite. Using response surface methodology (RSM), operational parameters of the photocatalytic degradation were modeled and optimized by the best composite through central composite design approach. Applying optimized parameters led to 96% degradation of MB (8 mg/L) at pH 10 under 120 min visible light irradiation (λ > 365 nm) using 0.15 g of Sm2CeMnO6/g-C3N4 (20:80) composite in 100 mL aqueous solution. Due to low intrinsic charge transfer resistance, modified Eg, and good performance in e‒/h+ pairs production, Sm2CeMnO6/g-C3N4 (20:80) nanocomposite was introduced as a promising S-scheme photocatalyst.

Graphene quantum dots (GQD) and edge-functionalized GQDs as hole transport materials in perovskite solar cells for producing renewable energy: a DFT and TD-DFT study.

This study investigated the potential suitability of graphene quantum dots (GQD) and certain edge-functionalized GQDs (GQD-3Xs) as hole transport materials (HTMs) in perovskite solar cells (PSCs). The criteria for appropriate HTMs were evaluated, including solubility, hole mobility, light harvesting efficiency (LHE), exciton binding energy (Eb), hole reorganization energy (λh), hole mobility, and HTM performance. It was found that several of the compounds had higher hole mobility than Spiro-OMeTAD, a commonly used HTM in PSCs. The open circuit voltage and fill factor of the suitable GQD and GQD-3Xs were found to be within appropriate ranges for HTM performance in MAPbI3 PSCs. GQD-COOH and GQD-COOCH3 were identified as the most suitable HTMs due to their high solubility, small λh, and appropriate performance.

Improved cotton fabrics properties using zinc oxide-based nanomaterials: A review.

Zinc oxide nanoparticles (ZnO NPs) have gained significant attention in the textile industry for their ability to enhance the physicochemical properties of fabrics. In recent years, there has been a growing focus on the development of ZnO-based nanomaterials and their applications for cotton and other fabrics. This review paper provides an overview of the synthesis and diverse applications of ZnO-based nanomaterials for textile fabrics, including protection against UV irradiation, bacteria, fungi, microwave, electromagnetic radiation, water, and fire. Furthermore, the study offers the potential of these materials in energy harvesting applications, such as wearable pressure sensors, piezoelectric nanogenerators, supercapacitors, and human energy harvesting. Additionally, we discuss the potential of ZnO-based nanomaterials for environmental cleaning, including water, oil, and solid cleaning. The current research in this area has focused on various materials used to prepare ZnO-based nanocomposites, such as metals/nonmetals, semiconductors, metal oxides, carbon materials, polymers, MXene, metal-organic frameworks, and layered double hydroxides. The findings of this review highlight the potential of ZnO-based nanomaterials to improve the performance of textile fabrics in a range of applications, and the importance of continued research in this field to further advance the development and use of ZnO-based nanomaterials in the textile industry.

Novel photo and bio-active greyish-black cotton fabric through air- and nitrogen- carbonized zinc-based MOF for developing durable functional textiles.

This study explores the potential of using the carbonization of Zn-based metal-organic frameworks (Zn-MOF-5) under N2 and air to modify zinc oxide (ZnO) nanoparticle for the production of various photo and bio-active greyish-black cotton fabrics. The MOF-derived ZnO under N2 demonstrated a significantly higher specific surface area (259 m2g-1) compared to ZnO (12 m2g-1) and MOF-derived ZnO under air (41.6 m2 g-1). The products were characterized using various techniques, including FTIR, XRD, XPS, FE-SEM, TEM, HRTEM, TGA, DLS, and EDS. The tensile strength and dye degradation properties of the treated fabrics were also investigated. The results indicate that the high dye degradation capability of MOF-derived ZnO under N2 is likely due to the lower ZnO band gap energy and improvement in electron-hole pair stability. Additionally, the antibacterial activities of the treated fabrics against Staphylococcus and Pseudomonas aeruginosa were investigated. The cytotoxicity of the fabrics was studied on human fibroblast cell lines using an MTT assay. The study findings demonstrate that the cotton fabric covered with carbonized Zn-MOF under N2 is human-cell compatible while showing high antibacterial activities and stability against washing, highlighting its potential for use in developing functional textiles with enhanced properties.

Delafossite CuCoO2/ZnO derived from ZIF-8 heterojunctions as efficient photoelectrodes for dye-sensitized solar cells.

To achieve high-performance dye-sensitized solar cells (DSSCs), it is essential to establish new and effective photoelectrode materials. Herein, we report the successful synthesis of heterojunctions including Cu-based delafossite oxide CuCoO2 and ZnO derived from zeolitic imidazolate framework-8 (ZIF-8). The layered polyhedral nanocrystals of CuCoO2 produced through a feasible low temperature hydrothermal process and the faceted nanocrystals of ZnO were achieved by heat treatment of ZIF-8. The composite heterostructures were applied as photoelectrodes in DSSCs assembled using dye N719 and a Pt counter electrode. The physicochemical characteristics (XRD, FESEM, EDAX, mapping, BET, DRS), dye loading, and photovoltaic properties (J-V, EIS, IPCE) of the fabricated materials were studied and fully discussed. Results revealed that addition of CuCoO2 to ZnO significantly improved the Voc, Jsc, PCE, FF, and IPCE. Among all cells, CuCoO2/ZnO (0.1 : 1) showed the best performance (PCE = 6.27%, Jsc = 14.56 mA cm-2, Voc = 687.84 mV, FF = 62.67%, IPCE = 45.22%) and acted as a promising photoanode in DSSCs.

Rational modification of TiO2 photoelectrodes with spinel ZnFe2O4 and Ag-doped ZnFe2O4 nanostructures highly enhanced the efficiencies of dye sensitized solar cells.

To develop effective photoelectrode nanomaterials for dye-sensitized solar cells (DSSCs), spinel ZnFe2O4 (2.5, 5, 7.5, 10 wt%) and Ag-doped ZnFe2O4 (AgxZn1-x/2Fe2O4, x = 0.1, 0.2, 0.3, 0.4 mmol) nanomaterials were added into the TiO2 photoanodes. It was found that the DSSC fabricated with TiO2 + 5 wt% ZnFe2O4 exhibited the most improved efficiency of 3.89 % among the ZnFe2O4 containing devices. Furthermore, the power conversion efficiency (PCE) values were boosted when the Ag+ cations were doped into the ZnFe2O4 crystalline lattice. The greatest PCE = 5.75 % was achieved for the solar cell assembled using TiO2 + 5 wt% Ag0.2Zn0.90Fe2O4 photoanode indicating 47.81 % improved performance relative to that of the reference DSSC containing TiO2 + 5 wt% ZnFe2O4 photoelectrode. The electrochemical impedance spectra (EIS) approved that the DSSC with the TiO2 + 5 wt% Ag0.2Zn0.90Fe2O4 photoelectrode nanomaterial had the lowest charge transfer resistance but the greatest e-h recombination resistance at the interfaces of photoanode/dye/electrolyte. Hence, it had the quickest electron transport rate, and the greatest electron collecting efficiency in addition to the highest dye loading capacity and least photoluminescence (PL) intensity (charge recombination) which were all prominently beneficial for improvement of the DSSC performance.

Efficient hole transport materials based on naphthyridine core designed for application in perovskite solar photovoltaics.

Naphthyridine-based compounds with a donor-acceptor-donor (D-A-D) skeleton were considered as hole transport materials (HTMs) for perovskite solar cells (PSCs). The optical characteristics, stability, solubility, Hirshfeld surface analysis, crystal structure, and hole transport properties of the HTMs were studied systematically. The HOMO energies of all HTMs were higher than valence band of CH3NH3PbI3 (MAPbI3) perovskite signifying naphthyridine-based HTMs had appropriate energy alignments for usage in PSCs. The LUMO level of designed HTMs were higher than MAPbI3 conduction band ensuring prevention of backward electronic movement from MAPbI3 to the cathode. The λabsmax amounts of all HTMs were close 400 nm, which showed their competition with perovskite was impossible. The 18NP and 26NP HTMs had higher hole mobilities compared to that of the Spiro-OMeTAD. Considering aligned HOMO energies, suitable hole mobilities, satisfactory stability and solubility, 18NP (1,8-Naphthyridine) and 26NP (2,6-Naphthyridine) were introduced as the best HTM materials for PSCs which could replace Spiro-OMeTAD.

Molecular engineering of several butterfly-shaped hole transport materials containing dibenzo[b,d]thiophene core for perovskite photovoltaics.

Several butterfly-shaped materials composed of dibenzo[b,d]thiophene (DBT) and dibenzo-dithiophene (DBT5) cores were designed as hole transporting materials (HTMs) and their properties were studied by density functional theory (DFT) computations for usage in mesoscopic n-i-p perovskite solar cells (PSCs). To choose suitable HTMs, it was displayed that both of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energies of molecules were located higher than those of CH3NH3PbI3 (MAPbI3) perovskite as they were able to transfer holes from the MAPbI3 toward Ag cathode. Negative solvation energy (ΔEsolvation) values for all HTMs (within the range of - 5.185 to - 18.140 kcal/mol) revealed their high solubility and stability within CH2Cl2 solvent. The DBT5-COMe demonstrated the lowest values of band gap (Eg = 3.544) and hardness (η = 1.772 eV) (the greatest chemical activity) and DBT5-CF3 displayed the biggest η = 1.953 eV (maximum stability) that were predominantly valuable for effective HTMs. All HTMs presented appropriately high LHEs from 0.8793 to 0.9406. In addition, the DBT5 and DBT5-SH depicted the lowest exciton binding energy (Eb) values of 0.881 and 0.880 eV which confirmed they could produce satisfactory results for the PSCs assembled using these materials. The DBT5-SH and DBT5-H had maximum hole mobility (µh) values of 6.031 × 10-2 and 1.140 × 10-2 which were greater than those measured for the reference DBT5 molecule (µh = 3.984 × 10-4 cm2/V/s) and about 10 and 100 times superior to the calculated and experimental µh values for well-known Spiro-OMeTAD. The DBT5-COOH illustrated the biggest open circuit voltage (VOC), fill factor (FF) and power conversion efficiency (PCE) values of 1.166 eV, 0.896 and 23.707%, respectively, establishing it could be as the best HTM candidate for high performance PSCs.

Applications of zeolitic imidazolate framework-8 (ZIF-8) in bone tissue engineering: A review.

Bone tissue is a highly vascularized and dynamic tissue that continues to remodel throughout the life cycle of a person. Only a few researches are done on usage of zeolitic imidazolate framework-8 (ZIF-8) in the bone tissue engineering area. Hence, this review is focused on the application of the ZIF-8 in bone tissue engineering. This work includes an explanation of metal-organic frameworks (MOFs) and ZIF-8 including synthesis methods as well as biocompatibility and biomedical applications of ZIF-8. In fact, a literature review is provided on previous applications of ZIF-8 in bone tissue engineering. Also, the investigations related to employing ZIF-8 in bone scaffolds and drug delivery systems for the bone tissues are discussed, and future perspectives are also emphasized.

A review on surface modification methods of poly(arylsulfone) membranes for biomedical applications.

Considerable methods have so far been used for the surface modification of biomedical membranes. Several reviews and articles have been published on the improvements achieved in the field of poly(arylsulfone) membranes subjected to various surface modification methods and used in biomedical applications. This review concentrates on the surface modification, biological applications and future perspective of the poly(arylsulfone) biomedical membranes. Different surface modification procedures employed for the poly(arylsulfone) membranes have been classified, studied and compared. Diverse surface modification techniques include surface coating, chemical modification and immobilization/cross-linking, grafting, surface zwitterionicalization, mussel-inspired coating and layer-by-layer assembly. Furthermore, we review the recent research studies performed on the surface modification of the poly(arylsulfone) biomedical membranes. Meanwhile, the properties of biomedical membranes are also discussed in each section. At last, the future perspective and challenges of the strategies utilized for the surface modification of poly(arylsulfone) biomedical membranes are presented.

Fabrication of chitosan-polyethylene glycol nanocomposite films containing ZIF-8 nanoparticles for application as wound dressing materials.

Biocompatible nanocomposite films based on chitosan (CS) and polyethylene glycol (PEG) polymers containing cephalexin (CFX) antibiotic drug and zeolitic imidazolate framework-8 (ZIF-8) nanoparticles (NPs) were designed and fabricated to develop wound dressing materials capable of controlled drug release. Swelling experiment was performed in three acidic, neutral, and alkaline solutions. The tensile strength test reflected that upon increasing the NPs loading within the films, the tensile strength was enhanced but the elongation at break was diminished. The release of the CFX was intensively increased within approximately 3, 8, and 10 h (burst release) in acidic, neutral, and alkaline media, respectively while after that the CFX was smoothly released over time (sustained release). The antibacterial activities of all films were examined against Gram-positive (S. aureus, B. cereus) and Gram-negative (E. coli, P. aeruginosa, and Acinetobacter) bacteria frequently found in the infected wounds. Moreover, the MTT assay revealed that all films had high cell viabilities towards the L929 fibroblast cells confirming these nanocomposites could be used as favorable wound dressing materials. Finally, the film containing 4% ZIF-8 NPs (film 5) was chosen as the best sample due to it revealed appropriate mechanical properties, swelling, drug release and cell viability among all samples examined.

Synthesis and photocatalytic degradation activities of phosphorus containing ZnO microparticles under visible light irradiation for water treatment applications.

A series of phosphorus containing ZnO (P-ZnO) photocatalysts with various percentages of phosphorus were successfully synthesized using the hydrothermal method. The structural, physical and optical properties of the obtained microparticles were investigated using diverse techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible diffusion reflectance spectroscopy (UV-Vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and N2 adsorption-desorption analysis. The photocatalytic activities of the pure and P-ZnO samples were evaluated for the degradation of Rhodamine B (RhB) under visible light irradiation. The parameters such as pH, catalyst dosage, contaminant concentration and effect of persulfate as an oxidant were studied. It was found that the P-ZnO1.8% photocatalyst could destroy 99% of RhB (5 ppm) in 180 min at pH = 7; furthermore, it degraded ∼100% of 5 and 10 ppm of the RhB pollutant in 120 and 180 min, respectively, only by adding 0.01 g of persulfate into the reaction solution. To determine the photocatalytic mechanism, 2-propanol, benzoquinone and EDTA were used and it was indicated that hydroxyl radicals, superoxide ions and holes, all had major roles in the photocatalytic degradation but the hydroxyl radical effect was the most significant. The phenol degradation was also investigated using the P-ZnO1.8% optimum photocatalyst which could destroy 53% of the phenol (5 ppm) in 180 min. According to the reusability test, it was proved that after 5 cycles, the catalyst activity was not highly changed and it was potentially capable of pollutant degradation.

Nitrogen and phosphorous doped graphene quantum dots: Excellent flame retardants and smoke suppressants for polyacrylonitrile nanocomposites.

Nitrogen (N-GQD) as well as nitrogen and phosphorous co-doped (NP-GQD) graphene quantum dots were demonstrated as novel, low cost, green and highly effective flame retardants and smoke suppressants for polyacrylonitrile (PAN) nanocomposites. The N-GQD and NP-GQD samples were synthesized by hydrothermal method with citric acid as the main reactant. For the first time, the flame retardant and smoke suppressant properties of the NP-GQD were studied. The GQDs were introduced into PAN by solvent blending route. Subsequently, thermal stability, flame retardancy, fire behavior, fire hazard and structure of the residual char were investigated by thermogravimetric analysis (TGA), UL-94 vertical burning test, cone calorimetry, FE-SEM, and Raman spectroscopy. Results showed that both PAN/N-GQD and PAN/NP-GQD nanocomposites had higher flame retardancy and smoke suppressant behavior in addition to lower fire hazard properties than neat PAN. Furthermore, the residual chars for the nanocomposite samples were increased in comparison to the neat PAN. The improvements were even more significant in case of the PAN/NP-GQD due to the synergistic effect of nitrogen and phosphorous. The improvements were mainly ascribed to the ability of the N-GQD and NP-GQD to provide stronger and larger protective char barrier layers, which was even more pronounced in case of the NP-GQD.

Revealing the role of different nitrogen functionalities in the drug delivery performance of graphene quantum dots: a combined density functional theory and molecular dynamics approach.

The amount and type of nitrogen (N) functionalities in graphene quantum dots can be controlled by tuning the synthesis conditions, which gives rise to their diverse applications. Nitrogen-doped graphene quantum dots (N-GQDs) are highly biocompatible and their properties can be easily tuned. In this work, the role of different N-functionalities in the drug delivery performance of N-GQDs was investigated via molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The results indicated that the magnitude of binding energy between the gemcitabine (GC) drug and the central N-GQDs, i.e., graphitic, pyridinic and amido, was greater than that of pristine GQDs and edge N-GQDs. The quantum molecular descriptors revealed that adsorption of GC drug on the nanocarriers enhanced the chemical reactivity. The adsorption of the GC drug on the nanocarriers was spontaneously proceeded. However, the Gibbs free energy values for adsorption of the GC drug on the center N-GQDs were greater than those of pristine GQDs and edge N-GQDs. Also, the nature of the intermolecular interactions between the GC drug and nanocarriers was further investigated through quantum theory of atoms in molecules (QTAIM) and noncovalent interaction index (NCI). The simulation results demonstrated that the GC drug was loaded on the surface of all nanocarriers, while favorable drug release could occur only from the center N-GQDs in acidic environments of cancer tissues. Finally, the mechanism for the penetration of the drug-loaded nanocarriers across the cell membrane was studied and discussed via steered molecular dynamics (SMD). The results indicated that the force required to pull the drug-loaded nanocarriers was the smallest when the nanocarriers were penetrated perpendicularly rather than parallelly or obliquely into the membrane plane. Overall, the results suggested that the center N-GQDs had better performance in drug delivery than pristine GQDs and edge N-GQDs. Our findings offer insightful information on efficient utilization of N-GQDs as drug delivery systems.

Hybrid silica aerogel nanocomposite adsorbents designed for Cd(II) removal from aqueous solution.

Hybrid silica aerogel (HSA) nanoparticles were synthesized by sol-gel method and drying at ambient pressure. Also, two magnetic nanocomposites of HSA with Fe3 O4 nanoparticles and chitosan (CS) were prepared including HSA-Fe3 O4 and HSA-Fe3 O4 -CS. The morphology, structure, and magnetic properties of the HSA as well as its nanocomposites were analyzed by SEM, XRD, TGA, VSM, and ATR-FTIR techniques. The saturation magnetization (Ms ) values for the Fe3 O4 NPs, HSA-Fe3 O4, and HSA-Fe3 O4 -CS nanocomposite film were 69.93, 19.04, and 5.77 emu/g, respectively. Furthermore, the abilities of the HSA, HSA-Fe3 O4 , CS, and HSA-Fe3 O4 -CS adsorbents were assessed for removal of cadmium(II) heavy metal ions (100 ppm) from aqueous solution. All adsorbents removed/adsorbed the maximum Cd(II) ions in 120 min when adsorbent dosage = 20 mg and pH = 8. Moreover, the highest adsorption capacities were 58.5, 69.4, 65.8, and 71.9 mg/g for the HSA, CS, HSA-Fe3 O4, and HSA-Fe3 O4 -CS, respectively. Kinetic studies using all adsorbents verified that Cd(II) adsorption obeyed the second-order model illustrating the analyte chemisorption was happened on the adsorbent surfaces. All adsorption data were well consistent with the Langmuir isotherms. The reusability experiment confirmed that all of adsorbents could preserve >95% of their initial adsorption capacities even after five series of adsorption/desorption tests. PRACTITIONER POINTS: Hybrid silica aerogel (HSA), HSA-Fe3 O4, and HSA-Fe3 O4 -CS adsorbents were produced. Nanocomposites were characterized by XRD, TGA, SEM, VSM, and ATR-FTIR analysis. Adsorption of cadmium(II) ions by adsorbents was examined in aqueous solution. The highest adsorption capacity was obtained for the HSA-Fe3 O4 -CS (71.9 mg/g). Cd(II) adsorption followed second-order kinetics and Langmuir isotherm model.

Hexagonal boron nitride nanosheet as novel drug delivery system for anticancer drugs: Insights from DFT calculations and molecular dynamics simulations.

Density functional theory (DFT) calculations and molecular dynamic (MD) simulations were accomplished to comprehend the nature of the interactions between 5-fluorouracil (FU)/6-mercaptopurine (MP)/6-thioguanine (TG) anticancer drugs and hexagonal boron nitride (BN) nanosheet as a drug delivery system. It is found from the calculations that the adsorption process of drug molecules on the BN nanosheet is exothermic and occurs spontaneously. The polarity for the drug loaded complexes, offers the possibility of improving the condition of solubility, which is favorable for drug delivery in biological media. Orbital energy and density of state (DOS) calculations show that HOMO-LUMO energy gap of BN nanosheet decreases upon the adsorption of drug molecules. The quantum molecular descriptors show that the absorption of drugs on BN nanosheet increases the chemical reactivity. The results of the energy decomposition analysis (EDA) indicated that the dispersion interaction plays a predominant role in the stabilization of the drug-BN complexes. The intermolecular interactions were also investigated by the noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. The MD results showed that the average of the interaction energy values in acidic conditions are lower (absolute values) than corresponding values obtained at neutral pH, which indicated the drug could be released within the target cancer cells. These findings contribute to the development of drug delivery systems based on BN nanosheet for delivery of anticancer drugs.

Pharmaceutical applications of chitosan.

Chitosan (CS) is a linear polysaccharide which is achieved by deacetylation of chitin, which is the second most plentiful compound in nature, after cellulose. It is a linear copolymer of ß-(1 → 4)-linked 2-acetamido-2-deoxy-ß-d-glucopyranose and 2-amino-2-deoxy-ß-d-glucopyranose. It has appreciated properties such as biocompatibility, biodegradability, hydrophilicity, nontoxicity, high bioavailability, simplicity of modification, favorable permselectivity of water, outstanding chemical resistance, capability to form films, gels, nanoparticles, microparticles and beads as well as affinity to metals, proteins and dyes. Also, the biodegradable CS is broken down in the human body to safe compounds (amino sugars) which are easily absorbed. At present, CS and its derivatives are broadly investigated in numerous pharmaceutical and medical applications including drug/gene delivery, wound dressings, implants, contact lenses, tissue engineering and cell encapsulation. Besides, CS has several OH and NH2 functional groups which allow protein binding. CS with a deacetylation degree of ~50% is soluble in aqueous acidic environment. While CS is dissolved in acidic medium, its amino groups in the polymeric chains are protonated and it becomes cationic which allows its strong interaction with different kinds of molecules. It is believed that this positive charge is responsible for the antimicrobial activity of CS through the interaction with the negatively charged cell membranes of microorganisms. This review presents properties and numerous applications of chitosan-based compounds in drug delivery, gene delivery, cell encapsulation, protein binding, tissue engineering, preparation of implants and contact lenses, wound healing, bioimaging, antimicrobial food additives, antibacterial food packaging materials and antibacterial textiles. Moreover, some recent molecular dynamics simulations accomplished on the pharmaceutical applications of chitosan were presented.

Carboxymethyl chitosan: Properties and biomedical applications.

Chitosan (CS) derivatives are widely used in various biomedical applications due to their unique properties like biocompatibility, mucoadhesion, non-toxicity and capability to form gels. Furthermore, they are suitable candidates to manufacture films, tablets and nanotechnology-based systems which have the possibility for commercial production as well as industrial scale-up. CS has a low solubility at physiological pH (>6.0), thus limiting its application in systems needing higher solubility and drug release rate. Another drawback of CS is its fast water adsorption and high swelling degree in aqueous media, which can cause rapid drug release. Chemical modification of two hydroxyl and one amino groups existing on the CS chains using the carboxymethyl moieties will alter the CS properties. The water solubility of carboxymethyl chitosan (CMC) at various pH environments is governed by the carboxymethylation degree. The CMC derivatives can interact with cells which successfully result in cell growth/tissue regeneration and wound healing. They are also employed in the cosmetics production because of their moisture absorption-retention, antimicrobial and emulsion stabilizing characteristics. This work will highlight the most recent applications of CMC derivatives with antimicrobial, anticancer, antitumor, antioxidant and antifungal biological activities in various areas like wound healing, tissue engineering, drug/enzyme delivery, bioimaging and cosmetics.

Chitosan-based hydrogels: Preparation, properties and applications.

Chitosan (CS), the second most plentiful natural polysaccharide next to cellulose, has valuable characteristics including biocompatibility, nontoxicity and biodegradability. CS is broken down in the human body to innocuous products (amino sugars). Hydrogels are polymeric materials with three dimensional networks retaining a huge quantity of water within their structures which are of great interest in biomedical/environmental applications. Usually, injectable hydrogels have functional groups which are sensitive to pH, temperature or irradiation stimuli. Injectable scaffolds can be formed in situ through stimuli-responsive effect and they can overcome the drawback of traditional scaffolds which require surgery in order to be placed on the desired tissue. The antibacterial/antifungal activities of chitosan-based hydrogels and their applications in controlled drug delivery/release systems, tissue engineering, preparation of injectable hydrogels and water treatment (removal of heavy/toxic metals and dyes) will be described. Moreover, the molecular dynamics (MD) simulation were performed on the delivery of the anticancer chlorambucil (CB) drug using three silica filled polymeric nanocomposites based on chitosan (CS), polylactic acid (PLA) and polyethylene glycol (PEG) and it was illustrated that among three drug delivery systems (DDSs), the CS nanocomposite was the most efficient DDS due to the lowest drug diffusion was measured for the CS system that could lead to the most sustained/controlled drug delivery.