Chitosan Matrix Research Articles

Preparation and investigation of porous chitosan/carbon nanotube biocomposite coating by space holder method

For implants that can be used instead of bone, a porous chitosan/carbon nanotube biocomposite coating on the titanium surface was produced by the spacer holder method. Different chemical contents and varying amounts of space-holding material were studied. Carbon nanotube fibers and pore distributions are homogeneously dispersed in the biopolymer chitosan matrix. NaCl was used as a space holder, and the rate of space holder was increased by 90 % to obtain a trabecular bone-like structure successfully. By increasing the amount of spacer in the coating content from 0.45 g to 0.90 g, the pore size has reached from approximately 1–3 μm to 12 μm. XRD, FTIR, and Raman analysis interpreted the characterization of the coatings. With the addition of carbon nanotubes to the chitosan matrix coating, the stiffness and elastic modulus increased by 55 % and 80 %, respectively. The elastic modulus (12 GPa) of the chitosan/carbon nanotube composite coating is compatible with that of cortical bone. The surface roughness of the chitosan/carbon nanotube coating reached from 1 to 6 μm to 6–16 μm, forming a porous structure. The surface properties of the porous biocomposite coating are promising for orthopedic implant applications.

Enhanced recovery of germanium(IV) from zinc residue leachate by tartaric acid functionalized chitosan: Experiments and DFT calculation

The recovery of germanium (Ge) from zinc residue leachate has attracted increasing attention. Herein, this study report on the development of a tartaric acid functionalized chitosan (TA-CS) material serving as an efficient adsorbent for Ge(IV). The introduction of TA resulted in abundant protonatable hydroxyl and carboxyl groups, which endows materials with excellent buffering capacity under acidic conditions. Adsorption kinetics and isotherms showed a fast and efficient adsorption capacity of 57.28 mg/g for Ge(IV). In binary systems, Ge(IV) was preferentially adsorbed over Zn(II), a major coexisting ion, with a separation factor of 3.22. The SEM–EDS FT-IR, XPS and DFT results revealed that mechanisms in combination, including electrostatic adsorption, complexation, hydrogen bonding, and ion exchange, promoted the immobilization of Ge(IV) on TA. The TA-CS material also exhibited great reusability with an adsorption efficiency of 70% after 3 recycles. For the recovery of Ge(IV) in practical zinc residue leachate, the TA-CS material showed superior affinity toward Ge(IV) and a 10-fold higher of adsorption capacity compared to that of pristine chitosan. Together, TA-CS demonstrates that it is a viable and economical material for the separation and preconcentration of Ge(IV) from zinc residue leachate.

Ultrahigh Proton Conductivities of Postmodified Hf(IV) Metal-Organic Frameworks and Related Chitosan-Based Composite Membranes.

Recently, researchers have focused on preparing and studying proton exchange membranes. Metal-organic frameworks (MOFs) are candidates for composite membrane fillers due to their high crystallinity and structural characteristics, and Hf-based MOFs have attracted our attention with their high porosity and high stability. Therefore, in this study, Hf-based MOFs were doped into a cost-effective chitosan matrix as fillers to fabricate composite films having excellent proton conductivity (σ). First, the nanoscale MOFs Hf-UiO-66-(OH)2 (1) and Hf-UiO-66-NH2 (2) were chemically modified by a ligand design strategy to obtain SA-1 and CBD-2 bearing free -COOH units. The proton conductivities of SA-1 and CBD-2 under optimal test conditions reached 1.23 × 10-2 and 0.71 × 10-2 S cm-1. After that, we prepared composite membranes CS/SA-1 and CS/CBD-2 by the casting method; tests revealed that the introduction of MOFs improved the stabilities and σ values of the membranes, and their best σ could reach above 10-2 S cm-1 under 100 °C/98% RH. Further structural characterization and activation energy calculation revealed the conductive mechanism of the composite films. This investigation not only proposes a novel chemical modification method for optimizing the σ of MOFs but also promotes the development of MOF-doped composite membranes and provides a basis for future applications of MOFs in fuel cells.

Metal-Organic-Framework-based nanofiltration membranes for selective multi-cationic recovery from seawater and brines

Nanofiltration (NF) is gaining a role of increasing importance in Zero Liquid Discharge (ZLD)/Minimal Liquid Discharge (MLD) systems, enhancing the efficiency of downstream technologies to recover valuable minerals from seawater and brines. However, often the purity of the recovered minerals does not meet market specifications, making ZLD/MLD currently economically unfeasible. To such end, in this study, a novel positively charged NF membrane was developed to enhance magnesium and calcium selectivity. The membrane comprised: (i) an ultrafiltration substrate and (ii) an active layer that incorporated NH2-MIL-101(Al) and ZnO nanoparticles in a chitosan matrix. The influence of different loadings of NH2-MIL-101(Al) and ZnO on membrane structure, selectivity and water permeability was investigated. Initial filtration tests with single-salt solutions at 1000 ppm (NaCl, Na2SO4, MgCl2, CaCl2) showed that the membrane with 35%wt of ZnO presented the highest rejections of MgCl2 (90.10%) and CaCl2 (86.49%). Selectivity towards MgCl2 and CaCl2 was higher than those of commercial membranes (NF90 and NF270) and the positively charged membranes introduced in recent literature. The novel synthesized membrane in this work was also tested with synthetic seawater and brine at a trans-membrane pressure of 30 bar. Results highlighted the intriguing competitiveness of the novel membrane in terms of magnesium and calcium selectivity with NF90 and NF270 within the field of both seawater and brine valorization.

The enhancement of antibacterial and anti‐biofouling properties of chitosan/silver nanoparticles‐grafted composite polyamide membrane

AbstractThis study endeavors to augment the antibacterial and anti‐biofouling properties of thin‐film composite polyamide membranes by subjecting them to modification with antibacterial chitosan and silver nanoparticle materials through the UV‐induced graft polymerization technique. Various surface assessment methods were employed, and the efficiency of the membrane performance was demonstrated through the flux and the retention of the filtration process, which used calcium chloride as the foulant. Antibacterial, antifouling, and anti‐biofouling capabilities were assessed through several tests. The findings revealed that the chitosan/silver nanoparticles‐grafted membranes exhibited superior antibacterial and anti‐biofouling abilities with consistent flux and enhanced retention, underscoring the prospective implementation of this approach in filtration systems to curtail biofouling and bolster overall efficacy.

Visible light-responsive chitosan/sodium alginate/QDs@ZIF-8 nanocomposite films with antibacterial and ethylene scavenging performance for kiwifruit preservation

The deterioration of postharvest fruits and vegetables caused by ethylene and microorganisms leads to global resource waste. Therefore, the development of multifunctional packaging materials that scavenge ethylene and inhibit microorganisms is essential to extend the shelf life of fruits and vegetables and minimize waste. Herein, the excellent photocatalytic performance of QDs@ZIF-8 nanoparticles (NPs) was incorporated into chitosan (CS) and sodium alginate (SA) matrix by layer-by-layer (LBL) assembly method to obtain CS/SA/QDs@ZIF-8 nanocomposite films. These as-prepared films exhibited excellent antibacterial (antibacterial ratio >99%) and ethylene scavenging properties (scavenging ratio >40%) due to the synergistic effect between visible light-induced reactive oxygen species (ROS) and the higher specific surface area of ZIF-8. The extended shelf life of kiwifruit further confirmed the enhanced preservation performance of CS/SA/QDs@ZIF-8 nanocomposite films. In addition, with the addition of QDs@ZIF-8 NPs, the color, and transparency of the films decreased, but the mechanical strength, thermal stability, hydrophobicity, and barrier properties were improved. In summary, the successful construction of ethylene scavenging and antibacterial films provides new ideas for the innovation of environmentally adaptive and functionalization of films.

Removal of Cr(VI) by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron: Synthesis, mechanism, and longevity

Microscale zero-valent iron (mZVI) has shown great potential for groundwater Cr(VI) remediation. However, low Cr(VI) removal capacity caused by passivation restricted the wide use of mZVI. We prepared mZVI/GCS by encapsulating mZVI in a porous glutaraldehyde-crosslinked chitosan matrix, and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron particles. The average pore diameter of mZVI/GCS was 8.775 nm, which confirmed the mesoporous characteristic of this material. Results of batch experiments demonstrated that mZVI/GCS exhibited high Cr(VI) removal efficiency in a wide range of pH (2-10) and temperature (5-35°C). Common groundwater coexisting ions slightly affected mZVI/GCS. The material showed great reusability, and the average Cr(VI) removal efficiency was 90.41% during eight cycles. In this study, we also conducted kinetics and isotherms analysis. Pseudo-second-order model was the most matched kinetics model. The Cr(VI) adsorption process was fitted by both Langmuir and Freundlich isotherms models, and the maximum Langmuir adsorption capacity of mZVI/GCS reached 243.63 mg/g, which is higher than the adsorption capacities of materials reported in most of the previous studies. Notably, the column capacity for Cr(VI) removal of a mZVI/GCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day experiment. Therefore, mZVI/GCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(VI) remediation material with practical application prospects.

Characteristics of Chitosan Films with the Bioactive Substances-Caffeine and Propolis.

Chitosan is a natural and biodegradable polymer with promising potential for biomedical applications. This study concerns the production of chitosan-based materials for future use in the medical industry. Bioactive substances-caffeine and ethanolic propolis extract (EEP)-were incorporated into a chitosan matrix to increase the bioactivity of the obtained films and improve their mechanical properties. Acetic and citric acids were used as solvents in the production of the chitosan-based films. The obtained materials were characterized in terms of their antibacterial and antifungal activities, as well as their mechanical properties, including tensile strength and elongation at break. Moreover, the chemical structures and surface morphologies of the films were assessed. The results showed that the solution consisting of chitosan, citric acid, caffeine, and EEP exhibited an excellent antiradical effect. The activity of this solution (99.13%) was comparable to that of the standard antioxidant Trolox (92.82%). In addition, the film obtained from this solution showed good antibacterial activity, mainly against Escherichia coli and Enterococcus faecalis. The results also revealed that the films produced with citric acid exhibited higher activity levels against pathogenic bacteria than the films obtained with acetic acid. The antimicrobial effect of the chitosan-based films could be further enhanced by adding bioactive additives such as caffeine and propolis extract. The mechanical tests showed that the solvents and additives used affected the mechanical properties of the films obtained. The film produced from chitosan and acetic acid was characterized by the highest tensile strength value (46.95 MPa) while the chitosan-based film with citric acid showed the lowest value (2.28 MPa). The addition of caffeine and propolis to the film based on chitosan with acetic acid decreased its tensile strength while in the case of the chitosan-based film with citric acid, an increase in strength was observed. The obtained results suggested that chitosan films with natural bioactive substances can be a promising alternative to the traditional materials used in the medical industry, for example, as including biodegradable wound dressings or probiotic encapsulation materials.

Structural design of a hyperbranched chitosan-based bioplastic with excellent strength, antibacterial, and UV shielding performance

Renewable biomaterials have received increasing attention as ideal alternatives to non-biodegradable plastics, but the poor water resistance, antibacterial property, and bonding strength usually limit their development. Inspired by the mussel chemistry, a sustainable and facile strategy is reported for preparing a high-performance chitosan (CS)-based film by incorporating a water-soluble hyperbranched polyamide (HB) and inorganic–organic system. Nanofibrillated cellulose (NFC) serves as a biological template for the preparation of uniformly dispersed zinc oxide quantum dots (ZnO QDs). As a dynamic glue linkage, protocatechualdehyde (PA) containing catechol groups provides additional bridging between the ZnO QDs and the organic CS biopolymer, thus guiding the ZnO QDs to disperse more evenly in the CS matrix and promoting the multiple cross-linking interactions in the hybrid film. The toughness and strength of the composites are simultaneously increased by 276.7% and 150.9%, respectively. Owing to the optimization of hyperbranched structure, catechol chemistry, and inorganic–organic system, the resultant film also exhibits substantially improved water resistance, thermal stability, and UV shielding capability. Additionally, the functional ZnO QDs, catechol PA, and cationic CS synergistically endow the film with superior antibacterial properties. This novel and biomimetic strategy opens up new ideas for the design of multifunctional bioplastics, while driving the development of CS biomaterials in the areas of antibacterial adhesives, high-strength hydrogels, and UV resistant coatings.

Nickel–cobalt oxides decorated Chitosan electrocatalyst for ethylene glycol oxidation

A composite of NiCo2O4 modified electrocatalyst is prepared to enhance the ethylene glycol electrooxidation. Chitosan matrix is used to improve the activity and adsorption ability of the surface to enhance ethylene glycol conversion. A Comparative study is investigated between pristine NiCo2O4 and Chitosan-modified spinel oxide to evaluate the synergistic effect between spinel oxide and chitosan. The composite is studied in an alkaline solution using electrochemistry techniques. The electrochemical activity towards ethylene glycol electrooxidation is studied as a function of anodic oxidation current density. Thus, the oxidation current values for NiCo2O4 and NiCo2O4@Chitosan in 1.0 M EG and 1.0 M KOH are 36 and 42 mA cm−2, respectively. The long-term stability of the electrode is measured by constant potential chronoamperometry. Kinetic parameters like diffusion coefficient, Tafel slope, surface coverage, and transfer coefficient are calculated. The density-functional theory estimates the adsorption of small molecules like ethylene glycol, urea, and carbon monoxide. The adsorption energy is studied on the top site of Ni and Co atoms of NiCo2O4. Forcite model is used to study the interaction between spinel oxide and chitosan. The energy calculation assumes that chitosan is adsorbed on the spinel oxide surface and enhances chitosan's ability for the adsorption of small molecules.

Synthesis of Novel Bio-Composite Material for Functional Finishing of Cellulosic Textile Substrate

ABSTRACT Development and useful utilization of materials from agricultural wastes and biomass feedstock for the textile-finishing industry is of great significance to the research community worldwide. In this work, a sustainable and green chitosan and waste onion peel extract (CS-OS) composite material is prepared by the co-precipitation method and applied onto cotton fabrics for the development of antibacterial and radical-scavenging textiles. The composite was loaded onto cotton with and without citric acid as a cross-linker to obtain final textile substrate with durable functions. The composite formation and the coated cotton fabrics were examined using SEM, FT-IR, and TGA techniques. Antioxidant activity of the finished fabrics was evaluated using the DPPH assay, and antibacterial tests were performed using the colony counting method. The results revealed that composite-treated cotton showed good radical-scavenging and antibacterial activities. It was found that citric acid-cross-linked cotton fabrics displayed enhanced antibacterial and antioxidant properties.

Tailoring the photocatalytic activity of novel magnetically separable ZnFe12O19-chitosan bionanocomposites: A green preparation, structural characterization and comparative study

Nowadays, the evaluation of nano-catalyts and photocatalytic technology for inactivating environmental pollution is identified as a priority. Although a series of semiconductor nanomaterials have been proven for this aim, suppression of charge carrier recombination and the absorption of solar light are still challenging. In this study, a novel visible-light-responsive bionanocomposite of ZnFe12O19-chitosan (ZF-C) is designed by a facile two-step approach. The utilization of two natural stabilizer and capping agents including turnip and carrot juices is developed to adopt nucleation and growth mechanism of as-fabricated crystals. In addition, benefiting from green templates, various quantities of these precursors show a strong impact on the construction of products in terms of structure and shape. The physic-chemical results confirmed creation of uniform ZF nanoparticles employing 20 mL of turnip juices. The band gap energy of ZF-C nanocomposites was found to be 1.55 eV, offering highly light absorption property in visible area. Moreover, the optimum photocatalyst had a specific surface area of 3.37 m2 g −1. This research encompasses the first insights of photocatalytic efficiencies of ZF and [ZF-Cx] (x: 5.0%, 10.0% and 15.0%) nanocomposites toward five toxic dyes such as methyl violet (MV), erythrosine (EY), methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) under visible light. As a proof-of-concept, the nanocomposites with 10.0% of chitosan matrix could exhibit higher photocatalyst performance about 94.12% EY removal after 120 min, which is 1.15 times better than that of pristine ZF nanostructures. Based on active species trapping experiments, a possible photodegradation pathway of EY dye over the [ZF-C10] nanocomposites has been reported. These findings describes a revolutionary way for selecting [ZF-C10] nanostructure as eco-friendly and magnetically recyclable photocatalysts in dye-containing effluents.

Nano-Pd/Chitosan Composite: An Extremely Effective Catalyst to the Synthesis of Pyrazolyl Analogues through Suzuki–Miyaura Cross-Coupling Reactions in an Aqueous Medium

Substituted pyrazolyl derivatives were synthesized through Suzuki cross coupling of aromatic boronic acid with heterocyclic halide using newly synthesized nano-Pd/chitosan catalyst by the water-mediated green synthesis methodology. The reactivity of the nano-Pd catalyst was highly enhanced by incorporating palladium nanoparticles with a biopolymer chitosan matrix. The synthesized nano-Pd/chitosan catalyst was studied thoroughly for its structure, morphology, and other fundamental aspects such as the size and shape by various techniques including XRD, FESEM, and EDAX analyses. The scope of the catalyst was disclosed by their great stability with remarkable reusability for Suzuki cross-coupling reaction with twelve different boronic acids under the green synthetic methodology.

Chitosan-Based Composite Membranes with Different Biocompatible Metal Oxide Nanoparticles: Physicochemical Properties and Drug-Release Study.

Chitosan (CS) composite membranes were prepared using different biocompatible metal oxide nanoparticles (NPs): titanium dioxide (TiO2); iron oxide (Fe3O4); and aluminum oxide (Al2O3). For each nanoparticle, the CS-based composite membranes were prepared with two NPs contents in the CS solution, high (H) and low (L) NPs concentrations. To establish both concentrations, the NPs saturation point in the CS polymeric matrix was determined. The influence of NP concentrations on the physicochemical properties of the CS films was assessed. The prepared CS membranes were characterized with different techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and zeta potential. It was found that the addition of NPs in the CS matrix improved both swelling and mechanical properties. Nanocomposite CS membranes could be prepared using Al2O3 NPs. Swelling experiments revealed different pH-sensitive mechanisms, which might be beneficial in biomedical applications since solute permeation through CS-based composite membranes could be controlled by adjusting environmental conditions. When aspirin transport (ASA) through the prepared membranes was carried out in different release media, SGF (simulating gastric fluid) and SIF (simulating intestinal fluid without enzymes), it was observed that the Fickian diffusion coefficient (D) was conditioned by the pH of the release solution. In SGIT (simulating gastrointestinal transit) medium, a transition time (ttrans) was detected due to the shrinkage of the CS polymeric chains, and the drug release depended not only on the Fickian's diffusion but also on the shrinkage of the biopolymer, obeying Peppas and Sahlin equation.

Novel Nanogels Loaded with Mn(II) Chelates as Effective and Biologically Stable MRI Probes.

Here it is described nanogels (NG) based on a chitosan matrix, which are covalently stabilized by a bisamide derivative of Mn-t-CDTA (t-CDTA = trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid). the Mn(II) complex acts both as a contrast medium and as a cross-linking agent. These nanogels are proposed as an alternative to the less stable paramagnetic nanogels obtained by electrostatic interactions between the polymeric matrix and paramagnetic Gd(III) chelates. The present novel nanogels show: i) relaxivity values seven times higher than that of typical monohydrated Mn(II) chelates at the clinical fields, thanks to the combination of a restricted mobility of the complex with a fast exchange of the metal-bound water molecule; ii) high stability of the formulation over time at pH 5 and under physiological conditions, thus excluding metal leaking or particles aggregation; iii) good extravasation and accumulation, with a maximum contrast achieved at 24h post-injection in mice bearing subcutaneous breast cancer tumor; iv) high T1 contrast (1 T) in the tumor 24h post-injection. These improved properties pave the way for the use of these paramagnetic nanogels as promising magnetic resonance imaging (MRI) probes for in vitro and in vivo preclinical applications.

Rational design of antimicrobial peptide conjugated graphene-silver nanoparticle loaded chitosan wound dressing

Wound dressing with poor antibacterial properties, the tendency to adhere to the wound site, poor mechanical strength, and lack of porosity and flexibility are the major cause of blood loss, delayed wound repair, and sometimes causes death during the trauma or injury. In such cases, hydrogel-based antibacterial wound dressing would be a boon to the existing dressing as the moist environment will maintain the cooling temperate and proper exchange of atmosphere around the wound. In the present study, the multifunctional graphene with silver and ε-Poly-l-lysine reinforced into the chitosan matrix (CGAPL) was prepared as a nanobiocomposite wound dressing. The contact angle measurement depicted the hydrophilic property of CGAPL nanobiocomposite dressing (water contact angle 42°), while the mechanical property was 78.9 MPa. The antibacterial and cell infiltration study showed the antimicrobial property of CGAPL nanobiocomposite wound dressing. It also demonstrated no cytotoxicity to the L929 fibroblast cells. Chorioallantoic Membrane (CAM) assay showed the pro-angiogenic potential of CGAPL nanobiocomposite wound dressing. In-vitro scratch wound assay confirmed the migration of cells and increased cell adhesion and proliferation within 18 h of culture on the surface of CGAPL nanobiocomposite dressing. Later, the in-vivo study in the Wistar rat model showed that CGAPL nanobiocomposite dressing significantly enhanced the wound healing process as compared to the commercially available wound dressing Tegaderm (p-value <0.01) and Fibroheal@Ag (p-value <0.005) and obtained complete wound closure in 14 days. Histology study further confirmed the complete healing process, re-epithelization, and thick epidermis tissue formation. The proposed CGAPL nanobiocomposite wound dressing thus offers a novel wound dressing material with an efficient and faster wound healing property.

Biocomposite Coatings Doped with Magnesium and Zinc Ions in Chitosan Matrix for Antimicrobial Applications.

Hydroxyapatite doped with magnesium and zinc in chitosan matrix biocomposites have great potential for applications in space technology, aerospace, as well as in the biomedical field, as a result of coatings with multifunctional properties that meet the increased requirements for wide applications. In this study, coatings on titanium substrates were developed using hydroxyapatite doped with magnesium and zinc ions in a chitosan matrix (MgZnHAp_Ch). Valuable information concerning the surface morphology and chemical composition of MgZnHAp_Ch composite layers were obtained from studies that performed scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), metallographic microscopy, and atomic force microscopy (AFM). The wettability of the novel coatings, based on magnesium and zinc-doped biocomposites in a chitosan matrix on a titanium substrate, was evaluated by performing water contact angle studies. Furthermore, the swelling properties, together with the coating's adherence to the titanium substrate, were also analyzed. The AFM results emphasized that the composite layers exhibited the surface topography of a uniform layer, and that there were no evident cracks and fissures present on the investigated surface. Moreover, antifungal studies concerning the MgZnHAp_Ch coatings were also carried out. The data obtained from quantitative antifungal assays highlight the strong inhibitory effects of MgZnHAp_Ch against C. albicans. Additionally, our results underline that after 72 h of exposure, the MgZnHAp_Ch coatings display fungicidal features. Thus, the obtained results suggest that the MgZnHAp_Ch coatings possess the requisite properties that make them suitable for use in the development of new coatings with enhanced antifungal features.

Electrochemical Sensing of Amoxicillin Drug-Assisted Uropathogenic E. coli Bacteria Using Gold Nanostructures—A Preliminary Study

The present study focuses on the electrochemical sensing of amoxicillin (AMX, as a model antibiotic drug) and its interaction with Uropathogenic E. coli (UPEC) bacteria (as a model pathogen) under physiological conditions. The electrochemical sensor probe is formulated by nanostructured gold wires (AuNWs) embedded in a carbon nanofiber–chitosan (CNF-CHIT) matrix. The synthesis of AuNWs is characterized by scanning electron microscopy (SEM), UV-Visible spectrophotometry, and X-ray photoelectron spectroscopy (XPS). The CNF-CHIT/AuNW-modified system is characterized by SEM and XPS. Initially, the CNF-CHIT/AuNW electrode was utilized for the sensing of AMX; later, in the antibiotic drug-assisted sensing of UPEC, i.e., in the presence of AMX, the interaction of UPEC was studied. The modified electrode showed appreciable sensitivity for AMX sensing; also, the interaction of AMX with UPEC is studied at two different conditions. One, at a fixed concentration of AMX (100 µM) and different concentrations of UPEC bacteria (0.6–1.2 × 106 CFU/mL), and another with incubation time (1 h–1 h 35 min) for bacterial reaction. The electrochemical antimicrobial resistance developed by UPEC, which is inherent in the sensing of AMX, is the key concept for the detection of pathogens.

Physicochemical characterization of a low-oxygen composite based on chitosan and electrochemically exfoliated graphene

Chitosan and graphene composites are widely used as biological scaffolds. Aside from environmental concerns related to the Hummer's synthesis the composite obtained contains significant amounts of oxygen and other residues, besides the agglomerate formation. In this work, a few-layer graphene obtained by electrochemically exfoliation of graphite was designed and made up with chitosan forming a uniform composite showing a low oxygen content. The amide group formation and crystallographic data were used as an index of composite dispersion. Electrochemically exfoliated graphene presented higher crystallinity degree and uniform crystallite size conferring a homogeneous dispersion of the nanofiller in the chitosan matrix. Chemical interactions between the electrochemically exfoliated graphene and chitosan allowed a high carbon C/O ratio of 14.63 shown by XPS analysis, which gives the high conductivity value, desirable for several purposes.

Chitosan and cellulose-based composite hydrogels with embedded titanium dioxide nanoparticles as candidates for biomedical applications

Hydrogel based matrices and titanium dioxide (TiO2) nanoparticles (NPs) are well established materials in bone tissue engineering. Nevertheless, there is still a challenge to design appropriate composites with enhanced mechanical properties and improved cell growth. Progressing in this direction, we synthesized nanocomposite hydrogels by impregnating TiO2 NPs in a chitosan and cellulose-based hydrogel matrix containing polyvinyl alcohol (PVA), to enhance the mechanical stability and swelling capacity. Although, TiO2 has been incorporated into single and double component matrix systems, it has rarely been combined with a tri-component hydrogel matrix system. The doping of NPs was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and small- and wide-angle X-ray scattering. Our results showed that incorporation of TiO2 NPs improved the tensile properties of the hydrogels significantly. Furthermore, we performed biological evaluation of scaffolds, swelling degree, bioactivity assessment, and hemolytic tests to prove that all types of hydrogels were safe for use in the human body. The culturing of human osteoblast-like cells MG-63 on hydrogels showed better adhesion of cells in the presence of TiO2 and showed increasing proliferation with increasing amount of TiO2. Our results showed that the sample with the highest TiO2 concentration, CS/MC/PVA/TiO2 (1 %) had the best biological properties.