Antibacterial potentials of carbon dots immobilized on chitosan and glass surfaces.

Due to their antibacterial activity, chitosan­carbon dot composites possess great potential for pharmaceuticals, medicine, and food preservation. Conducting a comprehensive study of the interactions between chitosan, carbon dots, and bacteria is crucial to understanding the processes behind applying these composites. This study aimed to immobilize carbon dots (C-dots) synthesized from Elaeagnus angustifolia fruits on chitosan and glass microbeads' surfaces, to characterize the test materials obtained after synthesis and immobilization, and to investigate their antibacterial potentials. C-dot synthesis was carried out from water extract in an acidic medium with the help of microwave irradiation, and their structural and optical properties were characterized by TEM, XRD, FT-IR, UV-vis, Zeta potential, and fluorescence methods. The surface of the glass microbeads was first activated and functionalized with surface amine groups with a silaning agent. C-dots were immobilized on both glass and chitosan microbeads using a crosslinking agent. Antibacterial potentials of nine different test materials, obtained before or after immobilization, were evaluated both qualitatively (MIC and MBC) and quantitatively (GI50) on E. coli, S. typhimurium, B. subtilis, and S. aureus, with the standard broth microdilution method. FT-IR and SEM-EDX analyses showed that C-dots were immobilized on chitosan (˂1 mm) and glass (˂100 µm) microbead surfaces. C-dots reduced the cell viability by ~25 % on S. typhimurium and B. subtilis (MIC = 25 mg/mL). It was also found that the highest antibacterial effect was recorded for C-dots-glass microbeads, which had a toxic effect of 43 % on S. aureus. In addition, binding C-dots to glass microbeads increased the antibacterial effect selectively in Gram-positive bacteria, while binding to chitosan microbeads was effective in all bacteria. The study showed that the antibacterial potential of C-dots-chitosan microbeads is more effective than C-dots-glass microbeads. C-dots could be used as carbon-based nanomaterials in antibacterial surface preparation once immobilized.

Investigation of in vitro antimicrobial and cytotoxic effects of gold nanoparticles capped with meropenem and imipenem.

Aim: This study aimed to investigate the in vitro antimicrobial effect of gold nanoparticles capped with meropenem and imipenem against various strains and to evaluate the cytotoxic effect of gold nanoparticles on healthy human colon epithelial cells. Materials & methods: Gold nanoparticles were synthesized via the Turkevich method and tested for antimicrobial effects using broth microdilution. Cell culture studies were performed using a cytotoxicity assay with alamarBlue™. Results & conclusion: Nanoparticles (10-20 nm) with antibiotic coating were more effective against Escherichia coli, Proteus spp. and Serratia marcescens than pure antibiotics. They had a cytotoxic effect on cells at high concentrations but were safe at low concentrations.

Carbon quantum dots and chitosan-based heterogeneous silver catalyst for reduction of nitroaromatic compounds.

Chitosan plays a crucial role in catalysis, environmental remediation, and sustainable chemistry as a renewable and cationic polysaccharide. Chitosan-based metal catalysts are used in a broad range of chemical transformations. In the study, carbon quantum dots (CQDs) were derived from Momordica charantia fruits by microwave irradiation following a green chemistry approach. Three catalysts were designed: Ag(0)-chitosan, Ag(0)-chitosan-M. charantia fruit powder, and Ag(0)-chitosan-CQDs. The catalyst supports were prepared by stabilizing CQDs or M. charantia powder within the polymeric matrix of chitosan beads. Metallic silver particles were anchored onto glutaraldehyde cross-linked chitosan beads from the aqueous solution of silver nitrate. The heterogeneous silver catalysts were used to reduce toxic nitroaromatics (4-nitrophenol, 2-nitroaniline, 1,2-diamino-4-nitrobenzene, 2,4-dinitrophenol). The regeneration of catalysts was also covered. The reused catalysts retained their catalytic activities after ten cycles. The study suggested that presence of CQDs or M. charantia powder could improve the efficiency of the chitosan-based metallic silver catalysts.

Crystallization of struvite-K from pumpkin wastes.

BACKGROUND: Use of slow-release fertilizers derived from biological sources is important in sustainable agricultural development. Struvite-K (KMgPO4 ·6H2 O) is magnesium potassium phosphate mineral that has high potential for use as fertilizer in agriculture. Struvite-K is particularly suitable for slow-release fertilizer systems since struvite-K crystals are sparingly soluble in water. Seeds of pumpkin Cucurbita pepo L. are recovered and consumed as food, but the remaining pulp has no economic value. RESULTS: The present study evaluated the feasibility of struvite-K crystals recovery from pyrolysis products of pumpkin wastes. In the study C. pepo pulp was decomposed at high temperatures and potassium was extracted from the residue and then crystalized from the solution by addition of NaH2 PO4 ·2H2 O and MgCl2 ·6H2 O salts. Struvite-K was characterized by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) spectroscopy and X-ray diffraction (XRD) analysis. CONCLUSIONS: The study revealed pumpkin wastes can be evaluated as source of potassium and 80% of potassium could be recovered as struvite-K crystals, which have a potential use as a slow-release mineral fertilizer for sustainable agriculture operations. © 2021 Society of Chemical Industry.

Live Cell Imaging With Biocompatible Fluorescent Carbon Quantum Dots Derived From Edible Mushrooms Agaricus bisporus, Pleurotus ostreatus, and Suillus luteus.

In the study, fluorescent imaging of live cells was performed using fluorescent carbon quantum dots derived from edible mushrooms species; Agaricus bisporus, Pleurotus ostreatus, and Suillus luteus as a fluorophore agent. Carbon quantum dots were synthesized through a facile and low-cost method based on microwave irradiation of dried mushroom samples in hydrogen peroxide solution under optimized conditions (microwave energy, solution type, duration of microwave treatment, amount of mushroom). Upon purification with centrifugation, microfiltration, and dialysis, the lyophilized carbon quantum dots were identified through UV-visible, fluorescence and FT-IR, X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy, and quantum yield calculation. Cell viability assessment of the carbon quantum dots was evaluated against human epithelial cell line PNT1A using the Alamar Blue Assay. In vitro fluorescence cell imaging studies demonstrated that the carbon dots could dynamically penetrate the cell membrane and nuclear membrane and localize in both the cytoplasm and the nucleus.

Hexavalent chromium removal by magnetic particle-loaded micro-sized chitinous egg shells isolated from ephippia of water flea.

Modified chitin and magnetic particles are two important materials widely used in heavy metal removal studies. Loading of magnetic particles into conventional adsorbents has emerged as a recent convenient way to improve the properties of adsorptive materials. Compared to its deacetylated form chitosan, chitin has very limited use in removal of contaminants because of its insolubility in aqueous environments. This study reports an easy way to produce micro-sized chitin and gives details on loading of magnetic particles into micro-sized chitin to enhance the interaction of chitin with heavy metal contaminant; hexavalent chromium Cr(VI). Removal of Cr(VI) ions from the aquatic environments is of high importance considering its detrimental effects on human health. Chitin microcages that had been isolated from the ephippial eggs of Daphnia longispina (crustacean, water flea) were incorporated with magnetic particles. Chitin microcages and magnetic particles-loaded chitin microcages were tested in removal of Cr(VI) under different solution and operational parameters; adsorbent dosage, contact time, Cr(VI) ion concentration, pH and temperature. Magnetic particles-loaded chitin microcages yielded higher Cr(VI) removal performance under all the specified conditions; chitin microcages: 0.77 mmol/ g and particles-loaded chitin microcages: 1.29 mmol/ g.

Production of magnetic chitinous microcages from ephippia of zooplankton Daphnia longispina and heavy metal removal studies.

This is the first study on production of three dimensional chitinous microcages from ephippial eggs of a microcrustacean, Daphnia longispina (water flea) by keeping the original shape of its chitinous structure. Iron-based magnetic particles were successfully loaded into the chitinous microcages to enhance its heavy metal sorption capacity. The FT-IR, SEM-EDX and TGA analysis proved the purity of chitin and demonstrated that the loading of magnetic particles into the chitinous microcages was achieved. These newly obtained three-dimensional chitin microcages and magnetic particles loaded microcages were tested in Cd(II), Cr(III), Cu(II), Ni(II) and Zn(II) removal from aqueous solutions. Magnetic particles loaded microcages exhibited a better performance in removal of Cd(II), Cu(II) and Ni(II) ions; while unloaded microcages showed a higher affinity for Cr(III) and Zn(II). This study demonstrated that the chitin microcages are suitable carriers for iron-based magnetic particles. Here these new materials were studied only for removal of five heavy metal ions but these promising materials have a potential to be used in various fields.

Evaluation of antibacterial properties on polysulfone composite membranes using synthesized biogenic silver nanoparticles with Ulva compressa (L.) Kütz. and Cladophora glomerata (L.) Kütz. extracts.

Polysulfone (PS) composite membrane using green synthesized biogenic silver nanoparticles (Ag-NPs) with Ulva compressa (L.) Kütz. and Cladophora glomerata (L.) Kütz. extract were prepared by spin coating technique and are tested for antimicrobial activity using a direct contact test for the first time. Initially green synthesis of Ag-NPs was accomplished utilizing green macro algae i.e. U. compressa (L.) Kütz. and C. glomerata (L.) Kütz. by the reduction of AgNO3. The Ag-NPs/PS composite membranes from both algae revealed outstanding antimicrobial activity against all bacteria i.e. K. pneumonia, P. aeruginasa, E. coli, E. faecium and S. aureus. Bacterial growth was monitored for 17h with a temperature controlled microplate spectrophotometer. The kinetics of the outgrowth in each well were recorded continuously at 630nm every 60min. Thus present work remarkably offers a feasible, cheap and efficient alternative for making Ag-NPs and their utilization as antimicrobial agent on the PS composite membrane.

Characteristics of corneal lens chitin in dragonfly compound eyes.

Chitin in the compound eyes of arthropods serves as a part of the visual system. The quality of chitin in such highly specialised body parts deserves more detailed examination. Chitin in the corneal (ommatidial) lenses of dragonfly (Sympetrum fonscolombii) compound eyes was isolated by using the classical chemical method. The chitin content of the corneal lenses was determined to be quite high (20.3±0.85%). The FT-IR analysis showed that corneal lens chitin was in the α-form as found in all arthropod species where mechanical strength is required. The surface morphology analysis by scanning electron microscopy revealed that the outer part of corneal lenses consisted of long chitin fibrils with regular arrays of papillary structures while the smoother inner part had concentric lamellated chitin formation with shorter chitin nanofibrils. Chitinase enzymatic digestion studies, elemental analysis results and the degree of acetylation value showed the purity of chitin samples from corneal lens. The maximum degradation temperature value of the corneal lens chitin was observed at 369.2°C. X-ray analysis revealed that corneal lens chitin has high crystallinity index; 96.4%. Identification of chitin found in ommaditia of insect compound eyes can provide insights into insect vision and chitin-based optical material design studies.

Microfungal spores (Ustilago maydis and U. digitariae) immobilised chitosan microcapsules for heavy metal removal.

Designing effective chitosan-based biosorbents from unexploited biomass for heavy metal removal has received much attention over the past decade. Ustilago, loose smut, is a ubiquitous fungal plant pathogen infecting over 4000 species including maize and weed. This study aimed to establish whether the spores of the phytopathogenic microfungi Ustilago spores can be immobilised in cross-linked chitosan matrix, and it reports findings on heavy metal sorption performance of chitosan/Ustilago composite microcapsules. Immobilisation of Ustilago maydis and U. digitariae spores (from maize and weed) in chitosan microcapsules was achieved via glutaraldehyde cross-linking. The cross-linked microcapsules were characterised using scanning electron microscopy, FT-IR spectroscopy and thermogravimetric analysis. Sorption capacities of chitosan-U. maydis and chitosan-U. digitariae microcapsules were investigated and compared to cross-linked chitosan beads: Cu(II): 66.72, 69.26, 42.57; Cd(II): 49.46, 53.96, 7.87; Cr(III): 35.88, 49.40, 43.68; Ni(II): 41.67, 33.46, 16.43 and Zn(II): 30.73, 60.81, 15.04mg/g, respectively. Sorption experiments were conducted as a function of initial metal ion concentration (2-10mg/L), contact time (60-480min), temperature (25, 35 and 45°C), amount of the sorbent (0.05-0.25g) and pH of the metal solution. The microcapsules with spores exhibited better performance over the plain chitosan beads, demonstrating their potential use in water treatment.

Chitosan/sporopollenin microcapsules: preparation, characterisation and application in heavy metal removal.

Use of natural polymers as biosorbents for heavy metal removal is advantageous. This paper reports a study aiming to design a novel biosorbent from two biomacromolecules; chitosan, a versatile derivative of chitin, and sporopollenin, a biopolymer with excellent mechanical properties and great resistance to chemical and biological attack. Chitosan/sporopollenin microcapsules were prepared via cross-linking and characterised by employing scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Sorption performance of the microcapsules and the plain chitosan beads were tested for Cu(II), Cd(II), Cr(III), Ni(II) and Zn(II) ions at different metal ion concentration, pH, amount of sorbent, temperature and sorption time. The adsorption pattern followed Langmuir isotherm model and the sorption capacity of the chitosan/sporopollenin microcapsules was found to be Cu(II): 1.34, Cd(II): 0.77, Cr(III): 0.99, Ni(II): 0.58 and Zn(II): 0.71 mmol g(-1). Plain chitosan beads showed higher affinity for the ions; Cu(II): 1.46, Cr(III): 1.16 and Ni(II): 0.81 mmol g(-1) but lower for Cd(II): 0.15 and Zn(II): 0.25 mmol g(-1). Sporopollenin enhanced Cd(II) and Zn(II) ions sorption capacity of the chitosan microcapsules. Chitosan/sporopollenin microcapsules can be used in Cd(II) and Zn(II) metal removal.

Differentiations of chitin content and surface morphologies of chitins extracted from male and female grasshopper species.

In this study, we used Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), and scanning electron microscopy (SEM) to investigate chitin structure isolated from both sexes of four grasshopper species. FT-IR, EA, XRD, and TGA showed that the chitin was in the alpha form. With respect to gender, two main differences were observed. First, we observed that the quantity of chitin was greater in males than in females and the dry weight of chitin between species ranged from 4.71% to 11.84%. Second, using SEM, we observed that the male chitin surface structure contained 25-90 nm wide nanofibers and 90-250 nm nanopores, while no pores or nanofibers were observed in the chitin surface structure of the majority of females (nanofibers were observed only in M. desertus females). In contrast, the elemental analysis, thermal properties, and crystalline index values for chitin were similar in males and females. Also, we carried out enzymatic digestion of the isolated chitins using commercial chitinase from Streptomyces griseus. We observed that there were no big differences in digestion rate of the chitins from both sexes and commercial chitin. The digestion rates were for grasshoppers' chitins; 88.45-95.48% and for commercial chitin; 94.95%.

Preparation and characterisation of biodegradable pollen-chitosan microcapsules and its application in heavy metal removal.

Biosorbents have been widely used in heavy metal removal. New resources should be exploited to develop more efficient biosorbents. This study reports the preparation of three novel chitosan microcapsules from pollens of three common, wind-pollinated plants (Acer negundo, Cupressus sempervirens and Populus nigra). The microcapsules were characterized (Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and elemental analysis) and used in removal of heavy metal ions: Cd(II), Cr(III), Cu(II), Ni(II) and Zn(II). Their sorption capacities were compared to those of cross-linked chitosan beads without pollen grains. C. sempervirens-chitosan microcapsules exhibited better performance (Cd(II): 65.98; Cu(II): 67.10 and Zn(II): 49.55 mg g(-1)) than the other microcapsules and the cross-linked beads. A. negundo-chitosan microcapsules were more efficient in Cr(III) (70.40 mg g(-1)) removal. P. nigra-chitosan microcapsules were found to be less efficient. Chitosan-pollen microcapsules (except P. nigra-chitosan microcapsules) can be used in heavy metal removal.

Arsenic(V) removal from underground water by magnetic nanoparticles synthesized from waste red mud.

In this study waste red mud (bauxite residue) sample obtained from Seydisehir (Konya, Turkey) was evaluated for the synthesis of Fe(3)O(4) nanoparticles (NPs) in ammonia solution that can be used to remove As(V) from both synthetic and natural underground water samples. The synthesized Fe(3)O(4)-NPs were characterized by using TEM, VSM, XRD, SAXS, TGA and FT-IR spectroscopy. The Fe(3)O(4)-NPs assumed a near-sphere shape with an average size of 9 nm. The results showed that synthesized Fe(3)O(4)-NPs from waste red mud have satisfactory magnetic properties and As(V) sorption capacity, especially at low equilibrium arsenate concentrations.

Determination of heavy metals and metals levels in five fish species from Isikli Dam Lake and Karacaören Dam Lake (Turkey).

The concentrations of heavy metals and metals (Zn, Pb, Bi, Cd, Ni, Co, Fe, Mn, Mg, Cu, Cr, Ca, Sr, Na, Li, K) were measured in muscle of five species Cyprinus carpio (from Isikli dam), Scardinius erythrophthalmus (from Isikli dam), Tinca tinca (from Isikli dam), C. carpio (from Karacaören dam), Carassius carassius (from Karacaören dam) caught from Isikli and Karacaören. The highest metal was Na (466.95 µg/g) in C. carassius, while the lowest levels were Fe (0.37 µg/g) and Cu (0.37 µg/g) in C. carpio from Isikli dam. The mean concentrations µg/g d.w. some of heavy metals in muscle of C. carpio (from Isikli dam), S. erythrophthalmus (from Isikli dam), T. tinca (from Isikli dam), C. carpio (from Karacaören dam), C. carassius (from Karacaören dam) were as follows: Cd 2.00-2.10-1.95-2.06-2.27, Zn 4.36-2.64-13.13-13.33-24.47, Pb 1.65-1.24-1.90-2.37-2.41, Co 2.46-2.37-2.48-2.58-2.80, Mg 138.51-154.35-218.59-204.58-202.16, Fe 0.37-2.62-3.17-3.01-12.33, respectively.

Surface modification of glass beads with glutaraldehyde: characterization and their adsorption property for metal ions.

In this study, a new material that adsorbs the metal ions was prepared by modification of the glass beads surfaces with glutaraldehyde. First, the glass beads were etched with 4M NaOH solution. Then, they were reacted with 3-aminopropyl-triethoxysilane (APTES). Finally, silanized glass beads were treated with 25% of glutaraldehyde solution. The characterization studies by using Fourier Transform Infrared Spectroscopy (FT-IR), Thermal Gravimetric Analysis (TGA), elemental analysis and Scanning Electron Microscopy (SEM) indicated that modification of the glass bead surfaces was successfully performed. The adsorption studies exhibited that the modified glass beads could be efficiently used for the removal of the metal cations and anion (chromate ion) from aqueous solutions via chelation and ion-exchange mechanisms. For both Pb(II) and Cr(VI), selected as model ions, the adsorption equilibrium was achieved in 60 min and adsorption of both ions followed the second-order kinetic model. It was found that the sorption data was better represented by the Freundlich isotherm in comparison to the Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacities for Pb(II) and Cr(VI) were 9.947 and 11.571 mg/g, respectively. The regeneration studies also showed that modified glass beads could be re-used for the adsorption of Pb(II) and Cr(VI) from aqueous solutions over three cycles.

Removal of fluoride from water by using granular red mud: Batch and column studies.

This paper describes the removal of fluoride from water using granular red mud (GRM) according to batch and column adsorption techniques. For the batch technique, the experiments demonstrated that maximum fluoride removal was obtained at a pH of 4.7 and it took 6h to attain equilibrium and equilibrium time did not depend upon the initial fluoride concentration. Kinetics data were fitted with pseudo-second-order model. The Redlich-Peterson and Freundlich isotherm models better represented the adsorption data in comparison to the Langmuir model. Column experiments were carried out under a constant influent concentration and bed depth, and different flow rates. The capacities of the breakthrough and exhaustion points decreased with increase of the flow rate. Thomas model was applied to the experimental results. The modelled breakthrough curves were obtained, and they were in agreement with the corresponding experimental data. The column adsorption was reversal and the regeneration operation was accomplished by pumping 0.2M of NaOH through the loaded GRM-column.

Facilitated transport of Cr(III) through activated composite membrane containing di-(2-ethylhexyl)phosphoric acid (DEHPA) as carrier agent.

The facilitated transport of chromium(III) through activated composite membrane (ACM) containing di-(2-ethylhexyl) phosphoric acid (DEHPA) was investigated. DEHPA was immobilised by interfacial polymerisation on polysulfone layer which was deposited on non-woven fabric by using spin coater. Then, ACM was characterised by using scanning electron microscopy (SEM), contact angle measurements and atomic force microscopy (AFM). Initially, batch experiments of liquid-liquid distribution of Cr(III) and the extractant (DEHPA) were carried out to determine the appropriate pH of the feed phase and the results showed that maximum extraction of Cr(III) was achieved at a pH of 4. It was also found that Cr(III) and DEHPA reacted in 1/1 molar ratio. The effects of Cr(III) (in feed phase), HCl (in stripping phase) and DEHPA (in ACM) concentrations were investigated. DEHPA concentration varies from 0.1 to 1.0M and it was determined that the transport of Cr(III) increased with the carrier concentration up to 0.8M. It was also observed that the transport of Cr(III) through the ACM tended to increase with Cr(III) and HCl concentrations. The stability of ACM was also confirmed with replicate experiments.

Removal of boron from aqueous solution by using neutralized red mud.

The adsorptive removal of boron from aqueous solution by using the neutralized red mud was studied in batch equilibration technique. The effects of pH, adsorbent dosage, initial boron concentration and contact time on the adsorption were investigated. The experiments demonstrated that boron removal was of a little fluctuation in pH range of 2-7 and it takes 20 min to attain equilibrium. The adsorption data was analyzed using the Langmuir and the Freundlich isotherm models and it was found that the Freundlich isotherm model represented the measured sorption data well.

Batch removal of chromium(VI) from aqueous solution by Turkish brown coals.

The ability of using low-rank Turkish brown coals (Ilgin: BC1, Beysehir: BC2, and Ermenek: BC3) to remove Cr(VI) from aqueous solutions was studied as a function of contact time, solution pH, temperature, concentration of metal solutions and amount of adsorbent. Their sorption properties were compared with the activated carbon from Chemviron (AQ-30). Adsorption of Cr(VI) uptake is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.2, depending on the biomaterial, that correspond to initial pH values of 2.3 units for BC1, 3.0 units for BC2 and 3.2 units for BC3 and AQ-30. Batch equilibrium tests showed that the Cr(VI) removal was fitted with Freundlich isotherm and the adsorption reached equilibrium in 80 min. It was proceeding effectively into a short acid pH interval (2.0-3.2) where processes of Cr(VI) sorption are maximized. It was observed that the maximum adsorption capacity of 11.2 mM of Cr(VI)/g for Ilgin (BC1), 12.4 mM of Cr(VI)/g for Beysehir (BC2), 7.4 mM of Cr(VI)/g for Ermenek (BC3) and 6.8 mM of Cr(VI)/g for activated carbon (AQ-30) was achieved at pH of 3.0. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K(c)) for the sorption of Cr(VI) ion. The Cr(VI) sorption capacities of Beysehir and Ilgin brown coals were the same. Ermenek brown coals and activated carbon (AQ-30) showed a similar sorption capacity.