Chitosan nanocomposite films: Enhanced electrical conductivity, thermal stability, and mechanical properties

Influence of Reduced Graphene Oxide and Carbon Nanotubes on the Structural, Electrical, and Photoluminescent Properties of Chitosan Films

Chitosan is a biopolymer with unique properties that have attracted considerable attention in various scientific fields in recent decades. Although chitosan is known for its poor electrical and mechanical properties, there is interest in producing chitosan-based materials reinforced with carbon-based materials to impart exceptional properties such as high electrical conductivity and high Young's modulus. This study describes the synergistic effect of carbon-based materials, such as reduced graphene oxide and carbon nanotubes, in improving the electrical, optical, and mechanical properties of chitosan-based films. Our findings demonstrate that the incorporation of reduced graphene oxide influences the crystallinity of chitosan, which considerably impacts the mechanical properties of the films. However, the incorporation of a reduced graphene oxide-carbon nanotube complex not only significantly improves the mechanical properties but also significantly improves the optical and electrical properties, as was demonstrated from the photoluminescence studies and resistivity measurements employing the four-probe technique. This is a promising prospect for the synthesis of new materials, such as biopolymer films, with potential applications in optical, electrical, and biomedical bioengineering applications.

Balancing mechanical property and swelling behavior of bacterial cellulose film by in-situ adding chitosan oligosaccharide and covalent crosslinking with γ-PGA

Bacterial cellulose (BC) is an ideal candidate material for drug delivery, but the disbalance between the swelling behavior and mechanical properties limits its application. In this work, covalent crosslinking of γ-polyglutamic acid (γ-PGA) with the chitosan oligosaccharide (COS) embedded in BC was designed to remove the limitation. As a result, the dosage, time, and batch of COS addition significantly affected the mechanical properties and the yield of bacterial cellulose complex film (BCCF). The addition of 2.25 % COS at the incubation time of 0.5, 1.5, and 2 d increased the Young's modulus and the yield by 5.65 and 1.42 times, respectively, but decreased the swelling behavior to 1774 %, 46 % of that of native BC. Covalent γ-PGA transformed the dendritic structure of BCCF into a spider network, decreasing the porosity and increasing the swelling behavior by 3.46 times. The strategy balanced the swelling behavior and mechanical properties through tunning hydrogen bond, electrostatic interaction, and amido bond. The modified BCCF exhibited a desired behavior of benzalkonium chlorides transport, competent for drug delivery. Thereby, the strategy will be a competent candidate to modify BC for such potential applications as wound dressing, artificial skin, scar-inhibiting patch, and so on.

In situ, synthesis of chitosan fabricated tellurium nanoparticles for improved antimicrobial and anticancer applications

The emergence of antibiotic resistance has had a severe impact on human health and economic burdens, drawing attention to the development of novel antimicrobial therapies. Polymer-metal composites have shown evidence of therapeutic applications by exerting antimicrobial effects and delivering these antimicrobials with biocompatibility. Therefore, this study prepared and characterized chitosan (CS)-fabricated tellurium nanoparticles (Te NPs) for enhanced antimicrobial, antioxidant, and cytotoxicity applications. The CS-Te NPs were spherical, polydisperse, and distributed within the CS matrix with an average size of 37.48 ± 14.56 nm, as confirmed by TEM analysis. CS-Te NPs exhibited positive zeta potential in neutral (pH 7.0: 7.90 ± 1.86 mV) and acidic environment. XRD analysis confirmed the crystalline nature of CS-Te NPs, and these nanoparticles exhibited good thermal and less porosity. A higher release of Te ions occurred from CS-Te NPs at an acidic pH. Further, CS-Te NPs displayed stronger antibacterial and antibiofilm activity against E. coli and S. enterica. Furthermore, CS-Te NPs exhibited significant free radical scavenging activity against ABTS and DPPH free radicals. Moreover, these nanoparticles demonstrated cytotoxicity against cancerous cells (A549 and PC3 cells) when compared to normal cells (NIH3T3 cells). Therefore, this study suggests that CS-Te NPs could serve as a substantial therapeutic agent.

Characterization, antioxidant and antibacterial activities of gelatin-chitosan edible coated films added with Cyclocarya paliurus flavonoids

In this study, gelatin-chitosan (GEL-CS) composite films added with 0.1 %, 0.2 %, and 0.3 % Cyclocarya paliurus flavonoids (CPF) were prepared. Then their appearance properties, mechanical properties, barrier properties, microstructure, thermal stability properties, antioxidant activity, and antibacterial properties were investigated. As compared with GEL-CS film, the GEL-CS films with CPF were darker in color, had higher water vapor barrier, higher elongation at break, and higher thermal stability. Additionally, microstructure analysis with Fourier infrared spectroscopy, scanning electron microscopy, and X-ray diffraction demonstrated that hydrogen bonding was the main force for cross-linking CPF with other membrane substrates. Moreover, the addition of CPF strengthened the antioxidant and antimicrobial properties of the membranes. These results indicated that the CPF addition could endow membranes with more excellent functional properties and bioactivity, accompanied by environmentally friendly and edible features. The GEL-CS-CPF composite film would be a potential and prospective packing material for food preservation applications.

Biosensors Based on Stanniocalcin-1 Protein Antibodies Thin Films for Prostate Cancer Diagnosis

Prostate cancer is one of the most prevalent tumors in men, accounting for about 7.3% of cancer deaths. Although there are several strategies for diagnosing prostate cancer, these are only accurate when the tumor is already at a very advanced stage, so early diagnosis is essential. Stanniocalcin 1 (STC1) is a secreted glycoprotein, which has been suggested as a tumor marker as its increased expression is associated with the development and/or progression of different types of malignant tumors. In this work, an electronic tongue (ET) prototype, based on a set of four sensors prepared from thin films that included STC1 antibodies for detecting prostate cancer, was developed. In the preparation of the thin films, polyelectrolytes of polyallylamine hydrochloride, polystyrene sulfonate of sodium and polyethyleneimine, and the biomolecules chitosan, protein A, and STC1 antibody were used. These films were deposited on quartz lamellae and on solid supports using layer-on-layer and self-assembly techniques. The deposition of the films was analyzed by ultraviolet-visible spectroscopy, and the detection of STC1 in aqueous solutions of PBS was analyzed by impedance spectroscopy. The impedance data were statistically analyzed using principal component analysis. The ETs formed by the four sensors and the three best sensors could detect the antigen at concentrations in the range from 5 × 10-11 to 5 × 10-4 M. They showed a linear dependence with the logarithm of the antigen concentration and a sensitivity of 5371 ± 820 and 4863 ± 634 per decade of concentration, respectively. Finally, the results allow us to conclude that this prototype can advance to the calibration phase with patient samples.

Antibacterial properties and osteoblast interactions of microfluidically synthesized chitosan - SPION composite nanoparticles

In this research, a multi-step microfluidic reactor was used to fabricate chitosan - superparamagnetic iron oxide composite nanoparticles (Ch - SPIONs), where composite formation using chitosan was aimed to provide antibacterial property and nanoparticle stability for magnetic resonance imaging (MRI). Monodispersed Ch - SPIONs had an average particle size of 8.8 ± 1.2 nm with a magnetization value of 32.0 emu/g. Ch - SPIONs could be used as an MRI contrast agent by shortening T2 relaxation parameter of the surrounding environment, as measured on a 3 T MRI scanner. In addition, Ch - SPIONs with concentrations less than 1 g/L promoted bone cell (osteoblast) viability up to 7 days of culture in vitro in the presence of 0.4 T external static magnetic field. These nanoparticles were also tested against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa), which are dangerous pathogens that cause infection in tissues and biomedical devices. Upon interaction of Ch - SPIONs with S. aureus and P. aeruginosa at 0.01 g/L concentration, nearly a 2-fold reduction in the number of colonies was observed for both bacteria strains at 48 h of culture. Results cumulatively showed that Ch - SPIONs were potential candidates as a cytocompatible and antibacterial agent that can be targeted to biofilm and imaged using an MRI.

Dual-Pulsed Laser Ablation of Oyster Shell Producing Novel Thin Layers Deposed to Saccharomyces cerevisiae

Dual-pulsed (DPL) laser deposition using oyster shells as targets was studied in order to find out if this method can replace the use of high-power pulsed lasers. Aspects related to changes in the morphological structure of the thin layer but also to the chemical composition of the obtained thin layer were analyzed and compared with the target as well as with the thin layers obtained with a higher power pulsed laser in a single-pulsed (SPL) regime. Orthorhombic structures were noticed with Scanning Electron Microscopy for the thin film obtained in DPL mode compared to the irregular particles obtained in SPL mode. The deacetylation process during ablation was evidenced by Fourier Transform Infrared spectroscopy, resulting in chitosan-based thin films. The effect of the obtained thin films of chitosan on the cells of baker's yeast (Saccharomyces cerevisiae) was studied. Restoration of the yeast paste into initial yeast was noticed mainly when the hemp fabric was used as support for the coating with yeas which was after that coated with chitosan thin film produced by DPL method.

Multidimensional applications and potential health implications of nanocomposites

This study reviews the concept, classifications, and techniques involved in the synthesis of nanocomposites. The environmental and health implications of nanoparticles and composite materials were detailed, as well as the applications of nanocomposites in water remediation, antibacterial application, and printed circuit boards. The study gave insights into the challenges of water pollution treatment and provided a broad list of nanocomposites that have been explored for water remediation. Moreover, the emergence of multi-drug resistance to many antibiotics has made current antibiotics inadequate in the treatment of disease. This has engineered the development of alternative strategies in the drug industries for the production of effective therapeutic agents, comprising nanocomposites with antibacterial agents. The new therapeutic agents known as nanoantibiotics are more efficient and have paved the way to handle the challenges of antibiotic resistance. In printed circuit boards, nanocomposites have shown promising applications because of their distinct mechanical, thermal, and electrical characteristics. The uniqueness of the write-up is that it provides a broad explanation of the concept, synthesis, application, toxicity, and harmful effects of nanocomposites. Thus, it will provide all-inclusive awareness to readers to identify research gaps and motivate researchers to synthesize novel nanocomposites for use in various fields.

Antimicrobial Bilayer Film Based on Chitosan/Electrospun Zein Fiber Loaded with Jaboticaba Peel Extract for Food Packaging Applications

This work focused on developing an active bilayer film based on natural extract. Thus, the jaboticaba peel extract (JPE) was produced and characterized and showed promising application as a natural additive in biopolymeric materials. The zein fiber and bilayer films were produced using a chitosan film (casting) and zein fiber (electrospinning), with and without JPE. All samples were evaluated according to thickness, solubility in water, water vapor permeability, and main diameter, and for these, zein fiber, chitosan/zein fiber, and chitosan/zein fiber + 3% JPE showed values of 0.19, 0.51, and 0.50 mm, 36.50, 12.96, and 27.38%, 4.48 × 10^-9, 1.6 × 10^-10, and 1.58 × 10^-10 (g m^-1 Pa^-1 s^-1), and 6.094, 4.685, and 3.620 μm, respectively. These results showed that the addition of a second layer improved the barrier properties of the material when compared to the monolayer zein fiber. The thermal stability analysis proved that the addition of JPE also improved this parameter and the interactions between the components of the zein fiber and bilayer films; additionally, the effective presence of JPE was shown through FTIR spectra. In the end, the active potential of the material was confirmed by antimicrobial analysis since the bilayer film with JPE showed inhibition halos against E. coli and S. aureus.

Preparation, Characterization and Antibacterial Property Analysis of Cellulose Nanocrystals (CNC) and Chitosan Nanoparticles Fine-Tuned Starch Film

To improve the mechanical and antibacterial properties of traditional starch-based film, herein, cellulose nanocrystals (CNCs) and chitosan nanoparticles (CS NPs) were introduced to potato starch (PS, film-forming matrix) for the preparation of nanocomposite film without incorporation of additional antibacterial agents. CNCs with varied concentrations were added to PS and CS NPs composite system to evaluate the optimal film performance. The results showed that tensile strength (TS) of nanocomposite film with 0, 0.01, 0.05, and 0.1% (w/w) CNCs incorporation were 41, 46, 47 and 41 MPa, respectively. The elongation at break (EAB) reached 12.5, 10.2, 7.1 and 13.3%, respectively. Due to the reinforcing effect of CNCs, surface morphology and structural properties of nanocomposite film were altered. TGA analysis confirmed the existence of hydrogen bondings and electrostatic attractions between components in the film-forming matrix. The prepared nanocomposite films showed good antibacterial properties against both E. coli and S. aureus. The nanocomposite film, consist of three most abundant biodegradable polymers, could potentially serve as antibacterial packaging films with strong mechanical properties for food and allied industries.

Polymer Electrolyte Membranes Containing Functionalized Organic/Inorganic Composite for Polymer Electrolyte Membrane Fuel Cell Applications

To mitigate the dependence on fossil fuels and the associated global warming issues, numerous studies have focused on the development of eco-friendly energy conversion devices such as polymer electrolyte membrane fuel cells (PEMFCs) that directly convert chemical energy into electrical energy. As one of the key components in PEMFCs, polymer electrolyte membranes (PEMs) should have high proton conductivity and outstanding physicochemical stability during operation. Although the perfluorinated sulfonic acid (PFSA)-based PEMs and some of the hydrocarbon-based PEMs composed of rationally designed polymer structures are found to meet these criteria, there is an ongoing and pressing need to improve and fine-tune these further, to be useful in practical PEMFC operation. Incorporation of organic/inorganic fillers into the polymer matrix is one of the methods shown to be effective for controlling target PEM properties including thermal stability, mechanical properties, and physical stability, as well as proton conductivity. Functionalization of organic/inorganic fillers is critical to optimize the filler efficiency and dispersion, thus resulting in significant improvements to PEM properties. This review focused on the structural engineering of functionalized carbon and silica-based fillers and comparisons of the resulting PEM properties. Newly constructed composite membranes were compared to composite membrane containing non-functionalized fillers or pure polymer matrix membrane without fillers.

A Redox-Probe-Free Immunosensor Based on Electrocatalytic Prussian Blue Nanostructured Film One-Step-Prepared for Zika Virus Diagnosis

The Zika virus (ZIKV) is a great concern for global health due to its high transmission, including disseminating through blood, saliva, urine, semen and vertical transmission. In some cases, ZIKV has been associated with microcephaly, neurological disorders, and Guillain−Barré syndrome. There is no vaccine, and controlling the disease is a challenge, especially with the co-circulation of the Dengue virus, which causes a severe cross-reaction due to the similarity between the two arboviruses. Considering that electrochemical immunosensors are well-established, sensitive, and practical tools for diagnosis, in this study we developed a sensor platform with intrinsic redox activity that facilitates measurement readouts. Prussian blue (PB) has a great ability to form electrocatalytic surfaces, dispensing redox probe solutions in voltammetric measurements. Herein, PB was incorporated into a chitosan−carbon nanotube hybrid, forming a nanocomposite that was drop-casted on a screen-printed electrode (SPE). The immunosensor detected the envelope protein of ZIKV in a linear range of 0.25 to 1.75 µg/mL (n = 8, p < 0.01), with a 0.20 µg/mL limit of detection. The developed immunosensor represents a new method for electrochemical measurements without additional redox probe solutions, and it is feasible for application in point-of-care diagnosis.

Novel Amperometric Biosensor Based on Tyrosinase/Chitosan Nanoparticles for Sensitive and Interference-Free Detection of Total Catecholamine

The regulation of nervous and cardiovascular systems and some brain-related behaviors, such as stress, panic, anxiety, and depression, are strictly dependent on the levels of the main catecholamines of clinical interest, dopamine (DA), epinephrine (EP), and norepinephrine (NEP). Therefore, there is an urgent need for a reliable sensing device able to accurately monitor them in biological fluids for early diagnosis of the diseases related to their abnormal levels. In this paper, we present the first tyrosinase (Tyr)-based biosensor based on chitosan nanoparticles (ChitNPs) for total catecholamine (CA) detection in human urine samples. ChitNPs were synthetized according to an ionic gelation process and successively characterized by SEM and EDX techniques. The screen-printed graphene electrode was prepared by a two-step drop-casting method of: (i) ChitNPS; and (ii) Tyr enzyme. Optimization of the electrochemical platform was performed in terms of the loading method of Tyr on ChitNPs (nanoprecipitation and layer-by-layer), enzyme concentration, and enzyme immobilization with and without 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as cross-linking agents. The Tyr/EDC-NHS/ChitNPs nanocomposite showed good conductivity and biocompatibility with Tyr enzyme, as evidenced by its high biocatalytic activity toward the oxidation of DA, EP, and NEP to the relative o-quinone derivatives electrochemically reduced at the modified electrode. The resulting Tyr/EDC-NHS/ChitNPs-based biosensor performs interference-free total catecholamine detection, expressed as a DA concentration, with a very low LOD of 0.17 μM, an excellent sensitivity of 0.583 μA μM⁻¹ cm⁻², good stability, and a fast response time (3 s). The performance of the biosensor was successively assessed in human urine samples, showing satisfactory results and, thus, demonstrating the feasibility of the proposed biosensor for analyzing total CA in physiological samples.

Doubly modified MWCNTs embedded in polyethersulfone (PES) ultrafiltration membrane and its anti-fouling performance

Multiwall carbon nanotubes (MWCNTs) are often used to modify polymer membranes as additives, however, MWCNTs are easy to agglomerate and entangle in polymer matrix due to their own strong van der Waals force. MWCNTs were doubly modified by bonding octadecylamine (ODA) and SiO2 through the respective amidation and esterification reactions to prepare SiO2-MWCNT-ODA nanocomposites. The amino groups on ODA were amidated with the carboxyl groups on MWCNT-COOH. Then the hydroxyl groups on SiO2 were bonded to MWCNT-COOH through esterification to obtain SiO2-MWCNT-ODA nanocomposites. PES/SiO2-MWCNT-ODA composite ultrafiltration (UF) membrane was prepared by non-solvent induced phase separation (NIPS) method. SiO2-MWCNT-ODA nanocomposites and PES/SiO2-MWCNT-ODA membrane were characterized by FTIR, XRD, TGA, and SEM, etc. The results showed that PES/SiO2-MWCNT-ODA membrane had significantly improved permeability, rejection, and antifouling properties for comparison with PES membrane. The pure water flux of PES/Nano.2-0.5 reached 212.5 L m−2 h−1, which was approximately 2.6 times than that of PES membrane, and the rejection of BSA protein for composite membrane was as high as 94.2%. PES/SiO2-MWCNT-ODA composite membrane had excellent antifouling performance and the flux recovery rate (FRR) of PES/Nano.2-0.5 membrane could still maintain at higher value of 84.82% after two cycles in the antifouling test.

Nanoarchitectonics for Biodegradable Superabsorbent Based on Carboxymethyl Starch and Chitosan Cross-Linked with Vanillin

Due to the growing demand for sustainable hygiene products (that will exhibit biodegradability and compostability properties), the challenge of developing a superabsorbent polymer that absorbs significant amounts of liquid has been raised so that it can be used in the hygiene sector in the future. The work covers the study of the swelling and dehydration kinetics of hydrogels formed by grafting polymerization of carboxymethyl starch (CMS) and chitosan (Ch). Vanillin (Van) was used as the crosslinking agent. The swelling and dehydration kinetics of the polymers were measured in various solutes including deionized water buffers with pH from 1 to 12 and in aqueous solutions of sodium chloride at 298 and 311 K. The surface morphology and texture properties of the analyzed hydrogels were observed by scanning electron microscopy (SEM). The influence of this structure on swelling and dehydration is discussed. Fourier transform infrared (FTIR) analyses confirmed the interaction between the carboxymethyl starch carbonyl groups and the chitosan amino groups in the resulting hydrogels. Additionally, spectroscopic analyses confirmed the formation of acetal crosslink bridges including vanillin molecules. The chemical dynamics studies revealed that new hydrogel dehydration kinetics strongly depend on the vanillin content. The main significance of the study concerns the positive results of the survey for the new superabsorbent polymer material, coupling high fluid absorbance with biodegradability. The studies on biodegradability indicated that resulting materials show good environmental degradability characteristics and can be considered true biodegradable superabsorbent polymers.

Alginate NiFe2O4 Nanoparticles Cryogel for Electrochemical Glucose Biosensor Development

Glucose biosensors based on porous material of alginate cryogel has been developed, and the cryogel provides a large surface area for enzyme immobilization. The alginate cryogel has been supplemented with NiFe2O4 nanoparticles to improve the electron transfer for electrochemical detection. The fabrication parameters and operational conditions for the biosensor have also been optimized. The results showed that the optimum addition of NiFe2O4 nanoparticles to the alginate solution was 0.03 g/mL. The optimum operational conditions for the electrochemical detection were a cyclic voltammetry scan rate of 0.11 V/s, buffer pH of 7.0, and buffer concentration of 150 mM. The fabricated alginate NiFe2O4 nanoparticles cryogel-based glucose biosensor showed a linear response for glucose determination with a regression line of y = 18.18x + 455.28 and R² = 0.98. Furthermore, the calculated detection limit was 0.32 mM and the limit of quantification was 1.06 mM.

IL versus DES: Impact on chitin pretreatment to afford high quality and highly functionalizable chitosan

Chitin is mainly extracted from crustaceans, but this resource is seasonally dependent and can represent a major drawback to satisfy the traceability criterion for high valuable applications. Insect resources are valuable alternatives due to their lower mineral content. However, the deacetylation of chitin into chitosan is still an expensive process. Therefore, we herein compare the impact of both DES/IL-pretreatments on the efficiency of the chemical deacetylation of chitin carried out over two insect sources (Bombyx eri, BE and Hermetia illucens, HI) and shrimp shells (S). The results showed that chitosans obtained from IL-pretreated chitins from BE larva, present lower acetylation degrees (13-17%) than DES-pretreated samples (18-27%). A selective N-acylation reaction with oleic acid has also been performed on the purest and most deacetylated chitosans leading to high substitution degrees (up to 27%). The overall approach validates the proper chitin source and processing methodology to achieve high quality and highly functionalizable chitosan.

Flexible and Conductive Bioelectrodes Based on Chitosan-Carbon Black Membranes: Towards the Development of Wearable Bioelectrodes

Wearable sensors for non-invasive monitoring constitute a growing technology in many industrial fields, such as clinical or sport monitoring. However, one of the main challenges in wearable sensing is the development of bioelectrodes via the use of flexible and stretchable materials capable of maintaining conductive and biocompatible properties simultaneously. In this study, chitosan-carbon black (CH-CB) membranes have been synthesized using a straightforward and versatile strategy and characterized in terms of their composition and their electrical and mechanical properties. In this sense, CH-CB membranes showed good conductivity and mechanical resistance thanks to the presence of carbon black, which decreases the insulating behavior of chitosan, while flexibility and biocompatibility are maintained due to the dual composition of the membrane. Thus, flexible and biocompatible conductive bioelectrodes have been developed by the combined use of CH and CB without the use of toxic reagents, extra energy input, or long reaction times. The membranes were modified using the enzymes Glucose Oxidase and Laccase in order to develop flexible and biocompatible bioelectrodes for enzymatic glucose biofuel cells (BFCs) and glucose detection. A BFC assembled using the flexible bioelectrodes developed was able to deliver 15 µW cm^-2, using just 1 mM glucose as biofuel, and up to 21.3 µW·cm^-2 with higher glucose concentration. Additionally, the suitability of the CH-CB membranes to be used as a glucose sensor in a linear range from 100 to 600 µM with a limit of detection (LOD) of 76 µM has been proven. Such demonstrations for energy harvesting and sensing capabilities of the developed membrane pave the way for their use in wearable sensing and energy harvesting technologies in the clinical field due to their good mechanical, electrical, and biocompatible properties.

Endogenous Electric Signaling as a Blueprint for Conductive Materials in Tissue Engineering

Bioelectricity plays an important role in cell behavior and tissue modulation, but is understudied in tissue engineering research. Endogenous electrical signaling arises from the transmembrane potential inherent to all cells and contributes to many cell behaviors, including migration, adhesion, proliferation, and differentiation. Electrical signals are also involved in tissue development and repair. Synthetic and natural conductive materials are under investigation for leveraging endogenous electrical signaling cues in tissue engineering applications due to their ability to direct cell differentiation, aid in maturing electroactive cell types, and promote tissue functionality. In this review, we provide a brief overview of bioelectricity and its impact on cell behavior, report recent literature using conductive materials for tissue engineering, and discuss opportunities within the field to improve experimental design when using conductive substrates.

Coated electrospun polyamide-6/chitosan scaffold with hydroxyapatite for bone tissue engineering

Polyamide-6 (PA6) is a synthetic polymer that bears resemblance to collagen in its backbone and has excellent stability in human body fluid. Chitosan (CS) with the similar structure to that of the polysaccharides existing in the extracellular matrix (ECM), has a more suitable biodegradation rate for the formation of new-bone. Electrospun fiber have nanoscale structure, high porosity and large specific surface area, can simulate the structure and biological function of the natural ECM. To meet the requirements of mechanical properties and biocompatibility of bone tissue engineering, electrospun PA6/CS scaffolds were fabricated by electrospinning technology. The mineralized PA6/CS scaffolds were obtained through immersion in 1.5× simulated body fluid (1.5SBF), which allowed the hydroxyapatite (HA) layer to grow into the thickness range under very mild reaction conditions without the need of a prior chemical modification of the substrate surface. The results showed that electrospun PA6/CS fibrous scaffolds in the diameter range of 60-260 nm mimic the nanostructure of the ECM. The tensile strength and modulus of 10PA6/CS fibrous scaffolds reach up to 12.67 ± 2.31 MPa and 95.52 ± 6.78 MPa, respectively. After mineralization, HA particles uniformly distributed on the surface of PA6/CS fibrous scaffolds in a porous honeycomb structure, and the content of mineral was about 40%. In addition, cell culture study indicated that the mineralized PA6/CS composite scaffolds were non-cytotoxic, and had a good biocompatibility and an ability to promote MC3T3-E1 cell attachment and proliferation.

Development and properties of bacterial cellulose, curcumin, and chitosan composite biodegradable films for active packaging materials

To deal with serious environmental damage resulting from plastic packaging materials, biodegradable films using natural products have gained considerable attention. Here, we provide a simple, fast, and environmentally-friendly route to construct a biodegradable film using chitosan (CS), bacterial cellulose (BC), and curcumin (Cur). Composite films (CSn-BC-Cur) using CS with different molecular weights were investigated, and their water moisture content (MC), water solubility (WS), contact angle (CA), mechanical properties, barrier properties, and antioxidant properties were compared. The obtained films were characterized by SEM, XRD, and TGA. The results showed that chitosan with a higher molecular weight presented higher contact angles and mechanical properties, along with a lower moisture content, water vapor transmission rate, and oxygen transmission rate. Furthermore, when the composite film was placed in 95 % ethanol, it released active substances. The results suggest that these composite films can be used as promising materials for food packaging.

Chitosan-based nanocomposites: preparation and characterization for food packing industry

In the present work, Cerium (IV)-Zirconium (IV) oxide nanoparticles (CeO4ZrNPs) was successfully dispersed into Chitosan/15Gelatin nanocomposites with different quantities. The obtained chitosan-based nanocomposites represented remarkable improvements in structural, morphological, mechanical, and thermal properties. Roughness increased from 74 nm to 6.4 nm, Young’s Modulus enhanced from 1.36 GPa to 2.99 GPa. The influence of dispersed CeO4ZrNPs contents on the phase transition temperature (T g) and the non-isothermal degradation processes of chitosan-based nanocomposites were examined using Differential Scanning Galorimetry (DSC) with different heating rates. Kinetic parameters of the thermal degradation for chitosan-based nanocomposites were evaluated using Kissinger-Akahira-Sunose (KAS) and Kissenger (KIS) procedures. Chitosan-based nanocomposites showed an increase in the thermal degradation temperature with higher activation energies, indicating improved thermal stability. Thermal analysis demonstrated that chitosan-based nanocomposites became more ordered by increasing CeO4ZrNPs as inferred from the negative entropy increase. Moreover, the degradation of chitosan-based nanocomposites has been described as a non-spontaneous process. The resulting information is particularly important in applications in which there is a need to obtain chitosan nanocomposites with improved mechanical and thermal properties such as food packing industry.

Preparation of a PES/PFSA-g-MWCNT ultrafiltration membrane with improved permeation and antifouling properties

In this study, perfluorosulfonic acid (PFSA) was firstly grafted on multi-walled carbon nanotubes (MWCNTs) to obtain PFSA-g-MWCNT nanocomposites.

Recent Developments in Polymer Nanocomposite-Based Electrochemical Sensors for Detecting Environmental Pollutants

The human population is generally subjected to diverse pollutants and contaminants in the environment like those in the air, soil, foodstuffs, and drinking water. Therefore, the development of novel purification techniques and efficient detection devices for pollutants is an important challenge. To date, experts in the field have designed distinctive analytical procedures for the detection of pollutants including gas chromatography/mass spectrometry and atomic absorption spectroscopy. While the mentioned procedures enjoy high sensitivity, they suffer from being laborious, expensive, require advanced skills for operation, and are inconvenient to deploy as a result of their massive size. Therefore, in response to the above-mentioned limitations, electrochemical sensors are being developed that enjoy robustness, selectivity, sensitivity, and real-time measurements. Considerable advancements in nanomaterials-based electrochemical sensor platforms have helped to generate new technologies to ensure environmental and human safety. Recently, investigators have expanded considerable effort to utilize polymer nanocomposites for building the electrochemical sensors in view of their promising features such as very good electrocatalytic activities, higher electrical conductivity, and effective surface area in comparison to the traditional polymers. Herein, the first section of this review briefly discusses the most important methods for polymer nanocomposites synthesis, such as in situ polymerization, direct mixing of polymer and nanofillers (melt-mixing and solution-mixing), sol-gel, and electrochemical methods. It then summarizes the current utilization of polymer nanocomposites for the preparation of electrochemical sensors as a novel approach for monitoring and detecting environmental pollutants which include heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, nitrite, and hydrazine in different mediums. Finally, the current challenges and future directions for the polymer nanocomposites-based electrochemical sensing of environmental pollutants are outlined.

Biocompatible Nanocomposites Based on Poly(styrene-block-isobutylene-block-styrene) and Carbon Nanotubes for Biomedical Application

In this study, we incorporated carbon nanotubes (CNTs) into poly(styrene-block-isobutylene-block-styrene) (SIBS) to investigate the physical characteristics of the resulting nanocomposite and its cytotoxicity to endothelial cells. CNTs were dispersed in chloroform using sonication following the addition of a SIBS solution at different ratios. The resultant nanocomposite films were analyzed by X-ray microtomography, optical and scanning electron microscopy; tensile strength was examined by uniaxial tension testing; hydrophobicity was evaluated using a sessile drop technique; for cytotoxicity analysis, human umbilical vein endothelial cells were cultured on SIBS-CNTs for 3 days. We observed an uneven distribution of CNTs in the polymer matrix with sporadic bundles of interwoven nanotubes. Increasing the CNT content from 0 wt% to 8 wt% led to an increase in the tensile strength of SIBS films from 4.69 to 16.48 MPa. The engineering normal strain significantly decreased in 1 wt% SIBS-CNT films in comparison with the unmodified samples, whereas a further increase in the CNT content did not significantly affect this parameter. The incorporation of CNT into the SIBS matrix resulted in increased hydrophilicity, whereas no cytotoxicity towards endothelial cells was noted. We suggest that SIBS-CNT may become a promising material for the manufacture of implantable devices, such as cardiovascular patches or cusps of the polymer heart valve.

Multi-Bit Biomemory Based on Chitosan: Graphene Oxide Nanocomposite with Wrinkled Surface

Chitosan (CS) is one of the commonly affluent polysaccharides that are attractive biomaterials as they are easily found in different organisms and are biocompatible. An environment-friendly multi-bit biomemory was successfully achieved on the basis of CS as a favorable candidate for resistive-switching memory applications. By incorporating graphene oxide (GO) into CS, the multi-bit biomemory device (indium tin oxide (ITO)/CS:GO/Ni) was obtained through the solution-processable method, which had a high current ratio among a high, intermediate, and low resistance state as well as a low SET/RESET voltage. GO acting as trapping sites in the active layer might be responsible for the biomemory mechanism. This research opens up a new avenue towards renewable and environmentally benign CS-based materials for biodegradable electronic devices.

Novel N-p-carboxy benzyl chitosan/poly (vinyl alcohol/functionalized zeolite mixed matrix membranes for DMFC applications

The novel N-p-carboxy benzyl chitosan (CBC)/ poly (vinyl alcohol) (PVA) based mixed matrix membranes (MMMs) filled with surface-modified zeolite have been prepared using the dissolution casting technique. The applicability of prepared MMMs for direct methanol fuel cell (DMFC) was investigated in terms of water uptake, methanol permeation, and proton conductivity by changing filler content (10-50 wt. %). The zeolite was modified by silane coupling agent, 3-mercaptopropyltrimethoxysilane (MPTMS). The resultant modified zeolite (MZ) was incorporated into CBC/PVA blend to obtain mixed matrix PEMs. The functional group, structural properties, morphological and topographical investigation of MMMs were examined using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning electron microscopy (SEM) respectively. The prepared MMMs exhibited a remarkable decrease in methanol permeability of 2.3 × 10^-7  cm²/s with C-CPMZ50. The maximum value of proton conductivity of 0.0527 Scm^-1, was shown by C-CMPZ10. The prepared PEMs also displayed good stability during long term operating time.

Biomemristic Behavior for Water-Soluble Chitosan Blended with Graphene Quantum Dot Nanocomposite

Bionanocomposite has promising biomemristic behaviors for data storage inspired by a natural biomaterial matrix. Carboxylated chitosan (CCS), a water-soluble derivative of chitosan avoiding the acidic salt removal, has better biodegradability and bioactivity, and is able to absorb graphene quantum dots (GQDs) employed as charge-trapping centers. In this investigation, biomemristic devices based on water-soluble CCS:GQDs nanocomposites were successfully achieved with the aid of the spin-casting method. The promotion of binary biomemristic behaviors for Ni/CCS:GQDs/indium-tin-oxide (ITO) was evaluated for distinct weight ratios of the chemical components. Fourier transform infrared spectroscopy, Raman spectroscopy (temperature dependence), thermogravimetric analyses and scanning electron microscopy were performed to assess the nature of the CCS:GQDs nanocomposites. The fitting curves on the experimental data further confirmed that the conduction mechanism might be attributed to charge trapping-detrapping in the CCS:GQDs nanocomposite film. Advances in water-soluble CCS-based electronic devices would open new avenues in the biocompatibility and integration of high-performance biointegrated electronics.

Multiwalled Carbon Nanotubes and the Electrocatalytic Activity of Gluconobacter oxydans as the Basis of a Biosensor

This paper considers the effect of multiwalled carbon nanotubes (MWCNTs) on the parameters of Gluconobacter oxydans microbial biosensors. MWCNTs were shown not to affect the structural integrity of microbial cells and their respiratory activity. The positive results from using MWCNTs were due to a decrease in the impedance of the electrode. The total impedance of the system decreased significantly, from 9000 kOhm (G. oxydans/chitosan composite) to 600 kOhm (G. oxydans/MWCNTs/chitosan). Modification of the amperometric biosensor with nanotubes led to an increase in the maximal signal from 65 to 869 nA for glucose and from 181 to 1048 nA for ethanol. The biosensor sensitivity also increased 4- and 5-fold, respectively, for each of the substrates. However, the addition of MWCNTs reduced the affinity of respiratory chain enzymes to their substrates (both sugars and alcohols). Moreover, the minimal detection limits were not reduced despite a sensitivity increase. The use of MWCNTs thus improved only some microbial biosensor parameters.

A Novel Method to Increase Tumor Ablation Zones With RFA by Injecting the Cationic Polymer Solution to Tissues: In Vivo and Computational Studies

OBJECTIVE

This study aims to examine, for the first time, the introduction of cationic polymer solutions to improve radiofrequency ablation (RFA) in terms of a potentially enlarged ablation zone.

METHODS

By using in vivo and computational RFA studies, two cationic polymers, Chitooligosaccharides (COS) and carboxymethyl chitosan (CMC), diluted in deionized water, were injected into tissues separately surrounding the RF bipolar electrode prior to power application. A total of 9 rabbits were used to 1) measure the increase in electrical conductivity of tissues injected with the cationic polymer solutions, and 2) explore the enhancement of the ablation performance in RFA trials. A computer model of RFA comprising a model of the solution diffusion with an RF thermal ablation model was also built, validated by the in vivo experiment, to quantitatively study the effect of cationic polymer solutions on ablation performances.

RESULTS

Compared to the control group, the electrical conductivity of rabbit liver tissues was increased by 42.20% (0.282 ± 0.006 vs. 0.401 ± 0.048 S/m, P = 0.001) and 43.97% (0.282 ± 0.006 vs. 0.406 ± 0.042 S/m, P = 0.001) by injecting the COS and CMC solution at the concentration of 100 mg/mL into the tissues, denoted COS_DW100 and CMC_DW100, respectively. Consequently, the in vivo experiments show that the ablation zone was enlarged by 95% (47.6 ± 6.3 vs. 92.6 ± 11.5 mm², P < 0.001) and 87% (47.6± 6.3 vs. 88.8 ± 9.6 mm², P < 0.001) by COS_DW100 and CMC_DW100, respectively. The computer simulation shows that the ablation zone was enlarged by 71% (51.9 vs. 88.7 mm²) and 63% (51.9 vs. 84.7 mm²) by COS_DW100 and CMC_DW100, respectively.

CONCLUSION

The injection of the cationic solution can greatly improve the performance of RFA treatment in terms of enlarging the ablation zone, which is due to the increase in the electrical conductivity of liver tissues surrounding the RF electrode.

SIGNIFICANCE

This study contributes to the improvement of RFA in the treatment of large tumors.

Water sorption, antimicrobial activity, and thermal and mechanical properties of chitosan/clay/glycerol nanocomposite films

Chitosan-based nanocomposites films with different clay loadings (0, 5, 10, 15 wt %), with (10, 20, 30 wt%) and without glycerol as plasticizer, were prepared by solution casting. The effects of the addition of clay and glycerol on the thermal, mechanical, water absorption, and antimicrobial activity properties of chitosan/clay nanocomposites films were investigated in this study. XRD results indicated that the intercalated structure was obtained in the chitosan/clay nanocomposites with and without glycerol. The thermal stability of the chitosan was significantly enhanced by the presence of clay and glycerol. It was found that the addition of clay into the chitosan improved significantly the tensile strength and tensile modulus. The highest values in strength and stiffness were achieved for the chitosal/clay nanocomposites with 5 wt% of clay and 20 wt% of glycerol. The addition of both clay and glycerol reduced drastically the ductility of chitosan. The best water resistance was obtained for the chitosan film containing 5 wt% of clay and 20 wt% of glycerol. The chitosan/clay nanocomposite film had potential for application of alternative food packing materials.

Comparison of the effects of gamma or sonochemical irradiation of carbon nanotubes and the influence on the mechanical and dielectric properties of chitosan nanocomposites

Chitosan-carbon nanotube (Chi-CNT) composite materials have been prepared with CNTs that were surface treated using either dilute acid combined with 20 kHz ultrasound or gamma-irradiation in air. The mechanical and dielectric properties have been measured and compared. Both modification methods gave nanocomposites with much improved tensile properties over native chitosan. The sonochemically treated samples were stronger with higher tensile strength but at the expense of lower elasticity and extensibility than found when γ-irradiation was used. Impedance spectra showed differences in the polymer chain transitions and in the conduction mechanisms within the nanocomposites. The results correlated well with previous work suggesting that the two modification techniques result in CNT surfaces with higher polarity. This enhances interfacial interactions with the chitosan matrix although the extent of functionalisation was greater in the sonochemical case. This work demonstrates that sonochemical modification under mild conditions is a useful method for modifying CNTs for inclusion in nanocomposite materials. However, the resulting material properties depend on the level of treatment so that the sonochemical conditions need to be carefully evaluated and controlled if the effects are to be optimised.