In this study, the effect of coated hydrogel layer on characteristics of the whole gelatin/silver nanoparticles multi‐coated polycaprolactone membrane (PCLGelAg) was investigated through systematic ...and typical wound dressing characterizations to select the optimal number of layers for practical applications. Scanning electron microscopy, free swell absorptive capacity and tensile test in both wet and dry conditions were conducted to characterize all fabricated membranes of six coating times. In vitro cytotoxicity and agar diffusion evaluation were also carried out to assess the biocompatibility and antibacterial activity of the membranes. The findings illustrated that as the coated layers increase, the absorptive capacity, and degradation rate were higher, the membranes were stiffer in dry state while the tensile strength in wet state, elongation, and cell viability were significantly decreased. PCLGelAg3 was chosen to be the best fit for wound healing since it maintained quite sufficient maximum buffer uptake, elasticity, cell viability along with inducing abnormalities in bacterial morphology and preventing biofilm formation.
•Ag/GO was successfully synthesized by co-precipitation.•LAA was used as a reducing agent, which is easy to find, and eco-friendly.•AgNPs with size 17.65 ± 4.76 nm were decorated on GO.•Concentration ...and contact time significantly affect the antibacterial activity.•The antibacterial activity of Ag/GO increased when pH value was decreased.
Herein, silver/graphene oxide (Ag/GO) nanocomposite was fabricated by co-precipitation with green reducing agent and then was characterized with modern analytical techniques. The antibacterial activities were conducted via the effects of Ag/GO concentration, time, and pH. Results show that silver nanoparticles were uniformly distributed on the GO sheets nanosized of 17.65 ± 4.76 nm. The antibacterial performance was optimized at pH 5.6, eradicating P. aeruginosa in 180 min at 50 µg/mL Ag/GO concentration and S. aureus in 480 min at 300 µg/mL Ag/GO. This demonstrates the potential of Ag/GO as an antibacterial nanocomposite material.
Exopolysaccharides (EPSs) are biological polymers secreted by microorganisms including Lactic acid bacteria (LAB) to cope with harsh environmental conditions. EPSs are one of the main components ...involved in the formation of extracellular biofilm matrix to protect microorganisms from adverse factors such as temperature, pH, antibiotics, host immune defenses, etc.. In this review, we discuss EPS biosynthesis; the role of EPSs in LAB stress tolerance; the impact of environmental stresses on EPS production and on the expression of genes involved in EPS synthesis. The evaluation results indicated that environmental stresses can alter EPS biosynthesis in LAB. For further studies, environmental stresses may be used to generate a new EPS type with high biological activity for industrial applications.
This study aims to investigate the mutual effect of integrating alginate (Alg) into N,O-carboxymethyl chitosan (NOCC) – aldehyde hyaluronic acid (AHA) network regarding degradation behavior and ...biocompatibility of the hybrid hydrogel. The introduction of Alg not only generated the synergistic effect between electrostatic interaction and Schiff-base crosslinking, which was proved to significantly enhance the system stability and prolong degradation time, but also circumvented the limitation of bio-inert property of Alg-based composites. This approach is versatile and does not required extra effort to modify chemical compositions of the hydrogel components. Fourier Transform Infrared Spectroscopy (FT-IR) analysis was used to study the crosslinking mechanism of obtained fast gelling hybrid. The variation of volume ratios between three constituent components was found to modulate the gel-forming ability, biodegradation and biocompatibility of acquired hydrogel networks. Among investigated formulations, 6:4(1:1) NOCC-Alg-AHA sample possessed desired interconnected porous structure as shown by SEM technique, appropriate water uptake capacity, extended degradation time and excellent cell attachment and proliferation through in vitro studies, which is a promising injectable scaffold and/or encapsulating substrate for tissue engineering applications.
Display omitted
•Prolong degradation rate of NOCC - AHA hydrogel without chemical modification by adding Alg.•Investigate the effect of hybrid crosslink at different volume ratio of NOCC, AHA and Alg.•Resolve the bio-inert of Alg to enhance cell adhesion and proliferation by endogenous interactions within the system.•Be used as an in-situ base to load inorganic phases, cells or drugs for further application in tissue engineering.
•Ag/rGO was successfully synthesized by co-precipitation.•L-ascorbic acid (environmentally friendly and abundant) was used as the reducing agent.•AgNPs with size 16 ± 3.7 nm were decorated on ...rGO.•Amount of reducing agents and catalysts, reaction time and type of dye significantly affect the antibacterial activity.•Ag/rGO effectively inhibited the development of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa.
The present study involved the preparation of silver-reduced graphene oxide (Ag/rGO) using co-precipitation method. The characteristics of Ag/rGO were confirmed by X-ray Diffraction patterns, Fourier transformation infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area, scanning electron microscopy, and energy-dispersive spectroscopy. The results demonstrated that silver nanoparticles (AgNPs) having diameter of 16 ± 3.7 nm were uniformly integrated on reduced graphene oxide (rGO) The as-synthesized Ag/rGO had a specific area of 54m2/g and 67.36 wt% silver. Antibacterial and catalytic properties of Ag/rGO were then further investigated. Ag/rGO was found to effectively inhibit the developing of gram-negative and gram-positive bacteria such as Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa with the bactericidal rates of 89.35, 95.67, and 99.99 %, respectively. In addition, the catalytic property of Ag/rGO in the reduction of organic dyes was tested with different dosage of reducing agent, amount of catalyst, type of dye, and reaction time. More than 99 % of dyes in aqueous solution at 20 mg/L concentration were reduced after 30 min with amounts of Ag/rGO and sodium borohydride of 10 and 30 mg successively. All results confirmed the potential application of Ag/rGO in the treatment of infected water and dye contamination.
Recycling biomass to cellulose aerogel (Cell-A) provides a promising approach to develop adsorbent materials for spilled-oil recovery. In this work, Cell-A was fabricated from Vietnamese water ...hyacinth via crosslinking methods using PVA as a crosslinker and freeze-drying process. Various cellulose to PVA ratios were investigated to obtain the optimal synthesis condition. The Cell-A was additionally modified by dip-coating in poly(dimethylsiloxane) (PDMS) and pyrolyzing to form PDMS-coated cellulose aerogels (Cell-AP) and carbon aerogels (CA), respectively. Results of the oil adsorption tests show that pyrolysis produced aerogels with greater adsorption capacity with an optimal mass ratio of 15 : 1 cellulose to PVA. Furthermore, the pseudo-second-order model was found to be more accurate than the pseudo-first-order model for the study of oil absorption kinetics. As a result, the modified cellulose aerogel is promising for replacing earth-unfriendly polymer-based oil sorbents due to their high oil absorption capacity.
Display omitted
Graphene aerogels (GAs) were synthesized from GO by chemical reduction in which ethylenediamine (EDA) was used as a reducing agent. The suitable conditions of GA synthesis were 30 μL ...of EDA, reaction temperature of 90 °C, and time of 6 h. The suitable GA was used as an adsorbent for removal of cadmium ions (Cd2+) from water. The adsorption data fitted well to a pseudo-second-order kinetic and Langmuir isotherm models with the maximum adsorption capacity of 149.25 mg/g.
In this study, graphene oxide (GO) was prepared from graphite by improved Hummers method. Graphene aerogels (GAs) were synthesized from GO by chemical reduction in which ethylenediamine (EDA) was used as a reducing agent. Influences of conditions on GA synthesis including content of EDA, reduction temperature and time were investigated. The structure and morphology of GAs were studied by density, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET) specific surface area. It was found that the suitable conditions of GA synthesis were 30 μL of EDA, reduction temperature of 90 °C, and time of 6 h. The density and BET specific surface area of suitable GA were determined to be 4.57 mg/cm3 and 845 m2/g, respectively. FTIR, XRD, and Raman results showed the oxygen-containing groups on the GO surface were partially reduced and self-assembly of reduced GO formed three-dimensional framework. SEM images presented the interconnected porous structure of GA with the pore size of 50 μm. The suitable GA was used as an adsorbent for removal of cadmium ions (Cd2+) from water. Effects of factors including pH, contact time, and initial Cd2+ concentration on the adsorption capacity of GA were studied. The adsorption data fitted well to a pseudo-second-order kinetic and Langmuir isotherm models with the maximum adsorption capacity of 149.25 mg/g. Accordingly, GA could be used as a potential adsorbent for removal of Cd2+ ions from water.
The hedge-algebras (HA) theory has been effectively applied in different fields such as fuzzy database, logic programming, classification and regression, data mining, linguistic database ...summarization, and process control. This work presents a simple approach to design an HA-based controller in stabilizing a nonlinear and underactuated system, an inverted pendulum-cart model, including four input state variables and one output control variable. The HA-based controller is divided into four intermediate controllers with one input state and one output control variable. The combination method of the above intermediate controllers to achieve values of the global control variable in control loops is proposed following the influence level of state variables on the stable state of the system and the principle of HA-Inference step. The proposed approach is appropriate for controlling underactuated systems. Simulation results have indicated that the HA-based controller has high performance, adaptation, stability, and robustness. Moreover, the proposed method significantly reduces the computational time of the controller when compared to a classical Sugeno-type fuzzy controller.
•Ag/GO was successfully synthesized by the in situ method. Glucose was used as an eco-friendly reducing agent.•AgNPs with an average size of 17.68 ± 4.48 nm.•Ag/GO express the extremely high ...antibacterial capacity against S. aureus and S. enterica.•Placket–Burman and Box–Behnken model experimental design was used to optimize.
In this study, silver/graphene oxide (Ag/GO) nanocomposites were synthesized using the in situ method. Glucose was selected as an eco-friendly reducing agent for the reduction of Ag+ into silver nanoparticles (AgNPs). The characterization of GO and Ag/GO with Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopye, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results showed that Ag/GO was successfully synthesized. Silver nanoparticles (AgNPs) with an average size of 17.68 ± 4.48 nm were uniformly distributed onto GO sheets. The antibacterial activity of GO, AgNPs, and Ag/GO were tested against Staphylococcus aureus ATCC 25,923 (S. aureus) and Salmonella enterica ATCC 35,664 (S. enterica) bacteria by optical density and plate colony–counting methods. Test results showed that Ag/GO had higher antibacterial activity than its precursors (bare AgNPs and GO) with a bactericidal rate of more than 99.90 %. Thus, Ag/GO was selected for further experimentation. Simultaneous effects of the interaction time, Ag/GO concentration, pH, annealing temperature, and S. aureus density on the antibacterial activity of Ag/GO were also investigated with full factorial experimental design according to Placket–Burman and Box–Behnken designs. After 10 min of interaction time at 37 °C, the optimal values of these factors were determined to be: Ag/GO concentration of 48 μg/mL, pH 5, and S. aureus density 5.3 × 106 CFU/mL, corresponding to an antibacterial capacity of 99.95 % towards S. aureus. The presented experiment confirmed Ag/GO to be able of eliminating about 99.99 % of S. aureus. All results of the present study affirmed the potential applications of Ag/GO as an antibacterial agent in the medical field.
The use of naturally occurring materials with antibacterial properties has gained a great interest in infected wound management. Despite being an abundant resource in Vietnam, chitosan and its ...derivatives have not yet been intensively explored for their potential in such application. Here, we utilized a local chitosan source to synthesize chitosan oligomers (OCS) using hydrogen peroxide (H
O
) oxidation under the microwave irradiation method. The effects of H
O
concentration on the physicochemical properties of OCS were investigated through molecular weight, degree of deacetylation, and heavy metal contamination for optimization of OCS formulation. Then, the antibacterial inhibition was examined; the minimum inhibitory concentration and minimum bactericidal concentration (MIC and MBC) of OCS-based materials were determined against common skin-inhabitant pathogens. The results show that the local Vietnamese chitosan and its derivative OCS possessed high-yield purification while the molecular weight of OCS was inversely proportional and proportional to the concentration of H
O
, respectively. Further, the MIC and MBC of OCS ranged from 3.75 to less than 15 mg/mL and 7.5-15 mg/mL, respectively. Thus, OCS-based materials induce excellent antimicrobial properties and can be attractive for wound dressings and require further investigation.
PDF
