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We report novel materials for calcium phosphate mineralization processes. These materials were synthesized via a three-step procedure starting from chitosan. In a first step, N-guanidinium-chitosan acetate was prepared via a direct guanylation reaction with cyanamide. This intermediate was then used as a cationic polymer substrate for attracting two functional anionic silica precursors, which subsequently allowed accessing new ionic hybrid materials via sol-gel chemistry. These N-guanidinium-chitosan acetate/silica hybrid materials, containing either sulfonate or carboxylate groups, were characterized using solid state 13 C NMR, 29 Si NMR and FT-IR spectroscopy. Finally, these two ionic hybrids were used as templates for in-vitro biomimetic calcium phosphate mineralization using simulated body fluid solution. We could show that the two ionic hybrids act as versatile templates for biomineralization, inducing the formation of hydroxyapatite, as proved from XRD, SEM, EDX, TEM and TGA. The current results suggest that the new ionic hybrids may be promising candidates for bone tissue engineering applications., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interests., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Methanogenesis and iron reduction play major roles in determining global fluxes of greenhouse gases. Despite their importance, environmental factors that influence their interactions are poorly known. Here, we present evidence that pH significantly influences the balance between each reaction in anoxic environments that contain ferric (oxyhydr)oxide minerals. In sediment bioreactors that contained goethite as a source of ferric iron, both iron reduction and methanogenesis occurred but the balance between them varied significantly with pH. Compared to bioreactors receiving acidic media (pH 6), electron donor oxidation was 85% lower for iron reduction and 61% higher for methanogenesis in bioreactors receiving alkaline media (pH 7.5). Thus, methanogenesis displaced iron reduction considerably at alkaline pH. Geochemistry data collected from U.S. aquifers demonstrate that a similar pattern also exists on a broad spatial scale in natural settings. In contrast, in bioreactors that were not augmented with goethite, clay minerals served as the source of ferric iron and the balance between each reaction did not vary significantly with pH. We therefore conclude that pH can regulate the relative contributions of microbial iron reduction and methanogenesis to carbon fluxes from terrestrial environments. We further propose that the availability of ferric (oxyhydr)oxide minerals influences the extent to which the balance between each reaction is sensitive to pH. The results of this study advance our understanding of environmental controls on microbial methane generation and provide a basis for using pH and the occurrence of ferric minerals to refine predictions of greenhouse gas fluxes., (© 2018 John Wiley & Sons Ltd.)

Minerals are versatile tools utilised to modify and control the physical-chemical and functional properties of substrates. Those properties include ones directing cell fate; thus, minerals can potentially provide a direct and inexpensive method to manipulate cell behaviour. This paper shows how different minerals influence human dermal fibroblast behaviour depending on their properties. Different calcium carbonates, calcium sulphates, silica, silicates, and titanium dioxide were characterised using TEM, ATR-FTIR, and zeta potential measurements. Mineral-cell interactions were analysed through MTT assay, LDH assay, calcein AM staining, live cell imaging, immunofluorescence staining, western blot, and extra/intracellular calcium measurements. Results show that the interaction of the fibroblasts with the minerals was governed by a shared period of adaptation, followed by increased proliferation, growth inhibition, or increased toxicity. Properties such as size, ion release and chemical composition had a direct influence on the cells leading to cell agglomeration, morphological changes, and the possible formation of protein-mineral complexes. In addition, zeta potential and FTIR measurements of the minerals showed adsorption of the cell culture media onto the particles. This article provides fundamental insight into the mineral-fibroblast interactions, and makes it possible to arrange the minerals according to the time-dependent cellular response., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The current article investigates the effect of bioactive cellulose/wool blend on calcium phosphate biomimetic mineralization. Regenerated cellulose/wool blend was prepared by dissolution-regeneration of neat cellulose and natural wool in 1-butyl-3-methyl imidazolium chloride [Bmim][Cl], as a solvent for the two polymers. Crystalline hydroxyapatite nanofibers with a uniform size, shape and dimension were formed after immersing the bioactive blend in simulated body fluid. The cytotoxicity of cellulose/wool/hydroxyapatite was studied using animal fibroblast baby hamster kidney cells (BHK-21) and the result displayed good cytocompatability. This research work presents a green processing method for the development of novel cellulose/wool/hydroxyapatite hybrid materials for tissue engineering applications., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Quaternized carboxymethyl chitosan/organic rectorite (QCMC/OREC) nanocomposites were rapidly prepared by intercalating QCMC into the layer of OREC under microwave irradiation. And then copper-chelate QCMC/OREC (QCMC/OREC-Cu) nanocomposites were obtained by mixing QCMC/OREC with CuSO4 solution. XRD and TEM results indicated that QCMC/OREC nanocomposites were obtained and QCMC was dispersed in the interlayer of OREC. Besides, FT-IR results revealed that the hydrogen bonds and electrostatic interaction in QCMC/OREC-Cu were both stronger than those in QCMC/OREC because of introducing the Cu(2+). The thermogravimetric analysis showed that the thermal stability of QCMC/OREC-Cu nanocomposites was higher than QCMC and QCMC/OREC. Algae inhibition assay revealed that QCMC/OREC-Cu nanocomposites had stronger antifouling activity than original QCMC and QCMC/OREC. This work provides important basis for developing novel antifouling materials., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silver nanoparticles (Ag NPs) were synthesized rapidly in one pot via the Tollens reaction, in which quaternized chitosan (QCS) and rectorite (REC) acted as the reducing and stabilizing agent, while other chemical reducing and stabilizing agents and the surfactant were not included. X-ray diffraction, scanning electron microscopy and transmission electron microscopy results showed that spherical Ag NPs with uniform sizes were obtained, the layers of clay were peeled and thus exfoliated QCS/REC/Ag NP (QCRAg) nanocomposite was achieved. Moreover, Ag NPs dispersed well in the exfoliated nanocomposite matrix, some Ag NPs even entered into the interlayer of REC. QCRAg nanocomposites showed strong antimicrobial activity; the lowest minimum inhibitory concentration against Staphyloccocus aureus was only 0.0001% (w/v). The study reveals that the obtained QCRAg nanocomposites have great potential for biomedical applications.

Microwave irradiation was used to intercalate quaternized carboxymethyl chitosan oligosaccharide (QCMCO) into the layer of rectorite (REC) to prepare QCMCO/REC (QCOR) nanocomposites in 70 min, which was much faster than conventional heating method of 48 h. The structures and morphology of QCOR nanocomposites were characterized by XRD, TEM, FT-IR and zeta potential analysis, the thermal behavior and antimicrobial activity of QCOR nanocomposites were also discussed. The results revealed that the interlayer distance of QCOR nanocomposites enlarged with the increase of QCMCO content, hydrogen bonding and electrostatic interaction between QCMCO and REC took place. As compared to QCMCO, the crystallinity of QCOR nanocomposites reduced, the thermal stability of QCOR nanocomposites improved, and the inhibitory activity of QCOR nanocomposites against microorganisms was stronger, the lowest minimum inhibition concentration was only 0.025% (w/v), the antimicrobial mechanism was discussed via TEM and SEM micrographs., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In this study, an attempt was made to prepare novel D-glucosamine hydrochloride-rectorite (DGH-REC) nanocomposites with improved antioxidant and anti-ultraviolet activity via the solution-intercalation method. The structure and morphology of DGH-REC nanocomposites were characterized by XRD, TEM, (13)C CP/MAS NMR, FT-IR, XPS and SEM. The results showed that the interlayer distance of REC was enlarged after intercalation of DGH; the largest value reached 11.76 nm, and in this case exfoliation of the REC layer was observed. Moreover, most strong crystals of DGH were greatly disrupted while two other weak crystals of DGH were stronger after intercalation of DGH into REC. More importantly, it was found that DGH-REC nanocomposites showed pronounced antioxidant activity, in contrast with DGH, and the nanocomposites had anti-ultraviolet capacity, which was not observed in DGH. Furthermore, the nanocomposites did not show apparent cytotoxicity. Therefore, DGH-REC nanocomposites have great potential in health or functional food application as compared to DGH.

Exfoliated quaternized carboxymethyl chitosan/rectorite (QCMC/REC) nanocomposite was prepared via microwave irradiation method for 70 min, which was performed in only water without any additional plasticizer. XRD, TEM, AFM, SEM and FTIR results revealed that when the mass ratio of QCMC to REC was no less than 4:1, the silicate layers of REC were completely exfoliated in QCMC matrix and were homogenous with QCMC, the surface of QCMC/REC nanobiocomposite was very smooth; two types of interactions of hydrogen bond and electrostatic attraction existed in the QCMC/REC nanobiocomposite. Thermal analysis indicated that QCMC/REC nanobiocomposite had higher thermal stability than only QCMC. Therefore, the microwave irradiation method appears to be a promising tool for preparing exfoliated biopolymer/layered silicate nanocomposites at a mild condition., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The rheological behaviour of the nanocomposites based on chitosan (CS) and unmodified rectorite (REC) were first evaluated. The nanocomposites showed a low shear-rate non-Newtonian viscosity and a rapid shear-thinning behaviour. The zero shear rate viscosity and the storage and loss moduli for the nanocomposites displayed a monotonic increase with increasing REC content in comparison with pure CS. The results implied the presence of electrostatic and hydrogen-bonding interaction between CS and REC, which was corroborated by the SEM images and FT-IR analysis. Then CS beads and CS/REC nanocomposite beads were prepared via the cross-linking interaction of sodium tripolyphosphate and CS, SEM images indicated that the nanocomposite beads had more compact surface and internal structure than those of CS beads. The swelling degree of the nanocomposite beads in 0.9% (w/v) saline was only about 15%, while that of CS beads was 30%. The nanocomposite beads released the drug continuously; in the given 6 days the minimum cumulative release only reached 51.4%, much lower than that of pure CS beads (72.1%). Therefore, CS/REC nanocomposites are more suitable to apply as drug carrier than pure CS.