Chitosan-multiwalled Carbon Nanotubes Research Articles

Chitosan/MWCNTs nanocomposite coating on 3D printed scaffold of poly 3-hydroxybutyrate/magnetic mesoporous bioactive glass: A new approach for bone regeneration

The utilization of 3D printing has become increasingly common in the construction of composite scaffolds. In this study, magnetic mesoporous bioactive glass (MMBG) was incorporated into polyhydroxybutyrate (PHB) to construct extrusion-based 3D printed scaffold. After fabrication of the PHB/MMBG composite scaffolds, they were coated with chitosan (Cs) and chitosan/multi-walled carbon nanotubes (Cs/MWCNTs) solutions utilizing deep coating method. FTIR was conducted to confirm the presence of Cs and MWCNTs on the scaffolds' surface. The findings of mechanical analysis illustrated that presence of Cs/MWCNTs on the composite scaffolds increases compressive young modulus significantly, from 16.5 to 42.2 MPa. According to hydrophilicity evaluation, not only MMBG led to decrease the contact angle of pure PHB but also scaffolds surface modification utilization of Cs and MWCNTs, the contact angle decreased significantly from 82.34° to 54.15°. Furthermore, investigation of cell viability, cell metabolism and inflammatory cytokines such as interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β) proved that the scaffolds not only do not stimulate the immune system, but also polarize macrophage cells from M1 phase to M2 phase. The present study highlights the suitability of 3D printed scaffold PHB/MMBG with Cs/MWCNTs coating for bone tissue engineering.

Molecularly imprinted polymers-aptamer electrochemical sensor based on dual recognition strategy for high sensitivity detection of chloramphenicol

In this paper, an electrochemical sensor based on a dual recognition strategy of molecularly imprinted polymers (MIPs) and aptamer (Apt) has been designed for the high sensitivity detection of chloramphenicol (CAP). Here, MIPs and Apt have provided dual recognition sites to greatly improve the specific recognition ability of the sensor. Chitosan-multi-walled carbon nanotubes (CS-MWNTs) and AuNPs (gold nanoparticles) have been used for their excellent electrical conductivity. When CAP existed in the detection environment, the imprinted cavities with specific recognition ability bound to CAP through forces such as hydrogen bonds. It hindered the rate of electron transfer and resulted in a decrease in current value. Quantitative detection of CAP could be achieved after analyzing the relationship between the concentration of CAP and the change of current value. After optimizing the experimental parameters, the detection range of the sensor was 10−8 g/L-10−2 g/L with the limit of detection of 3.3 × 10−9 g/L, indicating that the sensor had a high practical application potential.

β-cyclodextrin grafted multi-walled carbon nanotubes/chitosan (MWCNT/Cs/CD) nanocomposite for treatment of methylene blue-containing aqueous solutions

β-cyclodextrin (CD) was grafted with multi-walled carbon nanotubes/chitosan (MWCNTs/Cs) to obtain MWCNTs/Cs/CD nanocomposite (NC) for methylene blue (MB) adsorption from aqueous media. TEM, XRD, TGA, Raman spectra, and BET & BJH analyses were utilized to characterize and confirm the successful synthesis of as-prepared NC. MB capture was investigated by considering the parameters of pH (1.9–9.0), temperature (∼16–63 °C), sonication time (∼5–15 min), MB concentration (∼1.2–48 mg/L), and NC dose (0.03–0.26 mg). The obtained responses were then modelled using CCD, generalized regression neural network (GRNN), and least squares support vector machine (LS-SVM), of which the latter found to provide most reliable and accurate results (RMSE = 0.0235, MAE = 0.020, AAD = 0.0047, and R2 = 0.999). Moreover, the genetic algorithm-based optimization results showed that under the respective values of 7.05, 45.5 °C, 10 min, 23 mg/L, 0.12 g, MWCNTs/Cs/CD NC would be able to remove 96.75% of MB with an adsorption capacity of 603 mg/g, through different mechanisms mainly electrostatic interactions. Following from Dubinin-Radushkevich (D-R) isotherm (qs = 460.66 ± 8.9 and R2 > 0.99) and intraparticle diffusion kinetic (R2 = 0.75–0.90) models indicated a chemical adsorption mechanism. Besides, thermodynamic parameters (ΔH◦ = −66.9 kJ/mol, ΔG◦ = between −3.77 kJ/mol and −8.52 kJ/mol, and ΔS◦ = 237.1818 J/mol K) confirmed an endothermic and spontaneous nature for the adsorption. These findings along with appropriate recyclability (five times), turn the as prepared NC to a promising material in removing MB from aqueous solutions.

Adulteration of Milk Identification Using Ionic Polymer Metal Composite as Sensor

Milk adulteration is found as one of the social problems throughout the globe. Consumption of adulterated milk causes various diseases in humans and great concern to the food industry. Adulteration is generally done by adding chemicals to the milk, especially water. Inappropriately, milk is being very easily adulterated throughout the world and significantly worse in developing and underdeveloped countries due to the absence of adequate monitoring and lack of proper law implementation. The international and national research surveys presented the use of various electrochemical, nanomaterial, and thermal sensing mechanisms for the detection of adulteration in milk (example: spectroscopic methods, thermal sensors, chitosan-multiwalled carbon nanotubes, etc.). However, the ionic polymer metal composite (IPMC) is used as a sensor or actuator; for this application, IPMC is explored as a sensor for detecting the impurities in milk. IPMC used in this experiment is Nafion base, which is a sulfonated tetrafluoroethylene based fluoropolymer-copolymer. In this letter, the authors took the opportunity to use the electroactive polymer material IPMC as a taste sensor.

A Novel Nanocomposite of Zn(II)-Protoporphyrin-Chitosan-Multi Walled Carbon Nanotubes and the Application to Caffeic Acid Sensing.

Caffeic acid is an antioxidant that has been widely been related to the health benefits of people in recent years. In this paper, the amino side chains of chitosan (CS) were modified with protoporphyrin IX by amide cross-linking, and then Zn ions were chelated. The properties of metalloporphyrin-preparing functionalized multi-walled carbon nanotubes (MWCNTs) and Zn ions chelated by protoporphyrin IX composites were used as sensitive-selective electrochemical biosensors for the determination of caffeic acid. The morphology and structure of nanocomposite Zn–PPIX–CS–MWCNTs were observed by X-ray spectroscopy mapping (EDX mapping), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The electrochemical behaviors of Zn–PPIX–CS–MWCNT-modified glassy carbon (GC) electrodes were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the modified electrode had good electrocatalytic activity towards caffeic acid with a wide linear range of 0.0008–1.6 mM, an excellent sensitivity of 886.90 µAmM−1cm−1, and a detection limit of 0.022 µM. In addition, the caffeic acid sensor had excellent reproducibility, stability, and selectivity to various interfering substances. Therefore, the modified electrode prepared by this experiment can also be applied to electrochemical sensors of other substances.

Molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes for specific recognition and determination of chloramphenicol in milk

A molecularly imprinted electrochemical sensor of chloramphenicol (CAP) with high sensitivity and good selectivity is introduced in this paper. Glassy carbon electrode (GCE) was modified by chitosan-multiwalled carbon nanotubes (CS-MWCNTs), the CS could improve the dispersion of MWCNTS, and the MWCNTS could significantly improve the current response of the sensor, thus improving the sensitivity. CAP was used as a template molecule and o-phenylenediamine (o-PD) was used as a functional monomer, respectively. Molecularly imprinted polymers (MIPs) were prepared on the surface of a GCE modified with CS-MWCNTs by electro-polymerization. The MIPs provided specific recognition sites for the detection of chloramphenicol. The experimental parameters such as polymerization cycle, concentration ratio of template molecule to functional monomer, supporting electrolyte pH and incubation time were optimized. Under optimized experimental conditions, the sensor has a linear range of 0.1–1000 ng/mL and the limit of detection (LOD) of 3.3 × 10−2 ng/mL (S/N = 3). The sensor had high selectivity, good stability and reproducibility for the detection of CAP, and it has been successfully used for the determination of CAP in real spiked milk samples.

Surface and internal modification of composite ion exchange membranes for removal of molybdate, phosphate, and nitrate from polluted groundwater

Al 2 O 3 /chitosan-multiwall carbon nanotubes (MWCNTs) were created to increase the exchange capacity of polyvinylidene fluoride (PVDF) ion-exchange membranes. The composite membranes were made by mixing Al 2 O 3 nanoparticles into the PVDF cast solution, then applying a thin coating of chitosan functionalized carbon nano tubes (Cs-MWCNTs) to the PVDF membrane surface. The structure and characteristics of the hybrid membranes were described using XRD, SEM, IR, and TG-DTA. The Al 2 O 3 -PVDF/Cs-MWCNTs membrane beat the other Al 2 O 3 -PVDF/Cs, Al 2 O 3 -PVDF, and PVDF membranes in terms of molybdate, phosphate, and nitrate adsorption. The removal efficiency, pH solution, adsorption capacity, and desorption process of molybdate, phosphate, and nitrate anions by Al 2 O 3 -PVDF and PVDF membranes were investigated. The removal effectiveness of molybdate, phosphate, and nitrate, according to the testing findings, was 94.3, 65.6, and 85.78 %, respectively. The adsorption of MoO 4 2− , PO 4 3− , and NO 3 − increased as the pH increased initially until the best adsorption was achieved, and then decreased significantly as the pH increased further. The total adsorption capabilities of MoO 4 2− , PO 4 3− , and NO 3 − for the Al 2 O 3 -PVDF/Cs-MWCNTs membrane were 65.50, 61.22, and 59.77 mg/g, respectively. Using regeneration and reuse experiments for the simultaneous adsorption of molybdate, phosphate, and nitrate during three consecutive cycles, the adsorption/desorption of Al 2 O 3 -PVDF/Cs-MWCNTs was assessed. Al 2 O 3 -PVDF/Cs-MWCNTs offer a lot of promise when it comes to eliminating MoO 4 2− , PO 4 3− , and NO 3 − from actual wastewater samples.

Characterization of Betulinic Acid-Multiwalled Carbon Nanotubes Modified with Hydrophilic Biopolymer for Improved Biocompatibility on NIH/3T3 Cell Line.

The biocompatibility of carbon nanotubes (CNT) is fairly a challenging task for their applications in nanomedicine. Therefore, the objective of this research was to formulate four types of highly biocompatible betulinic acid-loaded biopolymer nanocomposites, namely chitosan-multiwalled carbon nanotubes (MWBA-CS), polyethylene glycol-multiwalled carbon nanotubes (MWBA-PG), Tween 20-multiwalled carbon nanotubes (MWBA-T2) and Tween 80-multiwalled carbon nanotubes (MWBA-T8). The physico-chemical properties of the modified nanocomposites were determined by Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA) and Raman spectroscopy, while the surface morphology of the resulting nanocomposites was studied using field emission scanning electron microscopy (FESEM). All data revealed that the external surface of MWBA nanocomposites was successfully coated with the respective polymer molecules through hydrophobic and electrostatic interactions with improved thermal profiles. The cell viability assay, which was performed on cultured normal embryonic mouse fibroblast cells, confirmed their excellent biocompatibility in phosphate-buffered saline aqueous media. Overall, our findings herein suggest that the synthesized biopolymer-coated MWBA nanocomposites are promising nanomaterials for drug delivery applications as they enhance the solubility and dispersibility of CNT with significantly reduced cytotoxic effect, especially in normal cells.

Analysis of neural cell behaviour on anisotropic electrically conductive polymeric biodegradable scaffolds reinforced with carbon nanotubes

AbstractThe advent of biocompatible and biodegradable scaffolds has opened up a plethora of possibilities in neural tissue engineering. An emerging approach to overcome some existing drawbacks of neural scaffold design and functioning is a natural conductive polymeric scaffold. It is analogous to the extracellular matrix and provides an environment conducive to neural growth. This study focuses on the fabrication of soft polymeric neural scaffold, reinforced with multi‐walled carbon nanotubes (MWCNTs) in a chitosan matrix, for directional neuronal growth. The scaffolds were fabricated by varying the nanofiller content as 0.5, 1.0 and 2.0. wt%, which were aligned in the chitosan matrix by an alternating bias electric field and compared with their random counterpart. The uniform distribution of the nanofillers in the matrix, good combinatorial bonding, and the directional alignment of the MWCNTs resulted in enhancement of mechanical properties and electrical conductivity in comparison to scaffolds with randomly arranged reinforcements. Additionally, the degradation kinetics of the fabricated scaffolds was tuned to the regeneration regime of peripheral nerves. After physical characterization, the biocompatibility of the designed scaffolds was evaluated by culturing HT‐22 neuronal cells on the scaffolds. Along with biocompatibility, the suitability of anisotropic conductivity of the scaffolds was evaluated by the directional growth of cells cultured on aligned MWCNT–chitosan scaffold. The preferential direction of neurite growth achieved on chitosan‐aligned MWCNT films and the improved mechanical and electrical properties in the MWCNT alignment direction are very encouraging for their potential use in neural tissue engineering.

Determination of Optical Band Gap Energies of CS/MWCNT Bio-nanocomposites by Tauc and ASF Methods

In the quest for developing new and advanced technologies, semiconductor band gap engineering is critical. In this study, chitosan/multi-walled carbon nanotube (CS/MWCNT) bio-nanocomposite films were prepared using a simple, environmental-friendly and cost-effective method, and the changes occurring in optical band gap energies (Eg) were examined with Tauc and Absorbance Spectrum Fitting (ASF) methods. The results of both models were found to be very close to each other. The optical and electrical properties of the bio-nanocomposites were significantly improved, which make them promising materials for ultraviolet protection, coating and optoelectronic applications. In addition, Urbach energies (Eu) (Band tails) and optical parameters of CS/MWCNT bio-nanocomposites such as refractive index (n), absorption (α) and extinction (k) coefficient were investigated. Urbach energy levels and refractive index values were increased with the increase of MWCNT content in CS matrix. The obtained low band gap energies of the composites by adding MWCNT were interpreted as evidence that the electrical conductivity of the composites is increased and this behavior was found to be consistent with surface conductivity measurements of the composites.

Electrical, optical and mechanical properties of chitosan biocomposites

In this work, chitosan/graphene nanoplatelets (CS/GNP) and chitosan/multi-walled carbon nanotube (CS/MWCNT) biocomposite films were prepared using a simple, eco-friendly and low-cost method. The electrical, optical and mechanical properties of these composite films were investigated. The optical, mechanical and electrical properties of the biocomposites were significantly improved, which make them promising materials for food packaging, ultraviolet protection and biomedical applications. With the increase of carbon filler content (GNP or MWCNT) in CS biocomposites, the surface conductivity ( σ), the scattered light intensity ( I sc) and the tensile modulus ( E) increased significantly. This behaviour in the electrical, optical and mechanical properties of the CS/carbon filler biocomposites was explained by percolation theory. The electrical percolation thresholds were determined as R σ = 25.0 wt.% for CS/GNP and R σ = 10.0 wt.% for CS/MWCNT biocomposites, while the optical percolation thresholds were found as R op =12.0 wt.% for CS/GNP and R op = 2.0 wt.% for CS/MWCNT biocomposites. Conversely, the mechanical percolation thresholds for both CS/GNP and CS/MWCNT biocomposites were found to be negligibly small ( R m = 0.0 wt.%). The electrical ( β σ), optical ( β op) and mechanical ( β m) critical exponents were calculated for both CS/carbon filler biocomposites and found compatible with the applied percolation theory.

Effect of Chemical Oxidation Routes on the Properties of Chitosan- MWCNT Nanocomposites

Background: Chitosan-multiwall carbon nanotubes (CS-MWCNTs) nanocomposites are an attractive material due to their biocompatibility and possibility to produce nanocomposites with high conductivities and high mechanical properties. Both electrical and mechanical properties depend upon the method of MWCNT chemical oxidation; this oxidation affects the interaction of CS side groups with MWCNT’s surface groups. However, in the literature, there are no reports on how different methods of MWCNT oxidation will affect the electrical and mechanical properties of related nanocomposites. Objective: The objective of this work is to probe CS-MWCNT nanocomposite’s electrical and mechanical properties by taking advantage of the presence of interfacial layer and its dependence on the methods of MWCNTs chemical oxidation routes. Methods: Nanocomposites are prepared with non-functionalized MWCNT and functionalized MWCNTs obtained by chemical oxidation treatments in HNO3 in H2SO4/NHO3 mixtures and commercially carboxyl-terminated MWCNTs, respectively. Properties of MWCNTs and nanocomposites were evaluated using SEM, FTIR, Raman, TGA, XRD, impedance and mechanical measurements. Results: It was shown that different chemical oxidation routes produce MWCNTs with a different number of carboxylic groups and defects which influence the interaction between MWCNTs with CS matrix and thickness of the interfacial layer between MWCNTs and CS matrix. Additionally, it was shown that the formation of the interfacial layer dominates on the dispersion of MWCNTs and affects on the electrical and mechanical percolation effects. Conclusion: It was shown that contrary to many studies previously reported, good dispersion of MWCNT does not guarantee obtained nanocomposites with the best electrical and mechanical properties.

Visual Electrofluorochromic Detection of Cancer Cell Surface Glycoprotein on a Closed Bipolar Electrode Chip.

This work reports an electrofluorochromic strategy on the basis of electric field control of fluorescent signal generation on bipolar electrodes (BPEs) for visualizing cancer cell surface glycoprotein (mucin 1). The device included two separate cells: anodic sensing cell and cathodic reporting cell, which were connected by a screen-printing electrode patterned on poly(ethylene terephthalate) (PET) membrane. In the sensing cell, anti-MUC1 antibody immobilized on a chitosan-multiwalled carbon nanotube (CS-MWCNT)-modified anodic BPE channel was used for capturing mucin-1 (MUC1) or MCF-7 cancer cells. Then ferrocene (Fc)-labeled mucin 1 aptamers were introduced through hybridization. Under an applied voltage, the ferrocene was oxidized and the electroactive molecules of 1,4-benzoquinone (BQ) in the cathodic reporting cell were reduced according to electroneutrality. This produced a strongly basic 1,4-benzoquinone anion radical (BQ•-), which turned on the fluorescence of pH-responsive fluorescent molecules of (2-(2-(4-hydroxystyryl)-6-methyl-4 H-pyran-4-ylidene)malononitrile) (SPM) coexisting in the cathode reporting cell for both spectrophotometric detection and imaging. This strategy allowed sensitive detection of MUC1 at a concentration down to 10 fM and was capable of detecting a minimum of three MCF-7 cells. Furthermore, the amount of MUC1 on MCF-7 cells was calculated to be 6.02 × 104 molecules/cell. Our strategy also had the advantages of high temporal and spatial resolution, short response time, and high luminous contrast and is of great significance for human health and the promotion of life science development.

Preparation, characterization and anti-bacterial activity of Chitosan/Carbon nanotube nanocomposites

Objective: To prepare Chitosan-Multi Walled Carbon Nanotube (Ch: MWCNT) nanocomposite with different chitosan: MWCNT ratios were successfully prepared by modifying chitosan and functionalized MWCNT. Methods: The prepared Ch-MWCNTs nanocomposite was characterized by TEM analysis confirming the MWCNTs homogenously distributed in chitosan matrix. Furthermore, TEM results indicate the resulting MWCNT tubular length morphology. Based on the FTIR results which confirm the presence of the C = C. The FTIR indicates that the characteristic functional groups of MWCNTs and chitosan are successfully present in modified nanocomposite. Findings/Application: Nanocomposite Ch/MWCNT showed higher antimicrobial activity against both Gram negative and Gram positive bacteria. The nanocomposites are highly differentiable at the lower conc. as even only 1% conc. from multifunctional nanocomposite has found to be very effective against the target microorganisms. Minimal Inhibitory Concentrations (MIC) of Ch-MWCNT (100:50 Ch/MWCNT) against Gram negative and Gram positive pathogenic bacteria between 0.5 and 0.0625 μl, and the growth inhibition effect has been observed in a concentration-dependent species. Keywords: Antimicrobial, Chitosan, CNT, Nanocomposites

Characterization and evaluation of nanocomposites chitosan-multiwalled carbon nanotubes as broad-spectrum antibacterial agent

Due to the wide and inappropriate use of the antibiotics, the development of new resistant strains of bacteria to the most of common antibiotics has become a serious problem in public health; so there is a strong stimulant to continuity developing new and effective antimicrobial agents. Nanotechnology considers as a magic tool to explore and treat the difficult problems of medical sciences. The confluence of nanotechnology and microbiology solves several biomedical problems, and also can revolutionize the health and medicine fields. Recently reports prove that carbon-based nanomaterials like multiwalled carbon nanotubes (MWCNTs) show potent antimicrobial properties. The nanocomposite chitosan-multiwalled carbon nanotube (Ch/MWCNT) was synthesized by the process of sonication for 20 min and examined their antibacterial activity. Seven different concentrations of MWCNT were used in the preparation of Ch/MWCNT (from 5 to 100 mg). The prepared differently concentrated MWCNT nanocomposite was characterized using TEM and FTIR. According to TEM results which showed that the morphology of MWCNTs were obtained in the form of small tubes of a length. FTIR show that the presence of the C=C absorption at the wave number 2344 cm-1which confirm the successful incorporation between chitosan and MWCNT. For antimicrobial activity estimation, the serial dilution method was used towards Gram positive bacteria (Staphylococcus aureus NRC 23516, Methicillin-resistant Staphylococcus aureus (MRSA) NRC 629012) and Gram negative bacteria (Escherichia coli 0157H7 and Pseudomonas aeruginosa ATCC10145). The composite Ch/MWCNT showed higher antimicrobial activity against both Gram negative and Gram positive bacteria; P. aeruginosa, Staphylococcus aureus; respectively with increasing MWCNT concentrationtill ratio 1:4. The nanocomposites are highly differentiable at the low concentration; 1% concentration of the multifunctional nanocomposite is very effective against the tested microbes. Minimal inhibitory concentrations (MIC) of Ch/MWCNT (100:50 Ch/MWCNT) against Gram negative and Gram positive pathogenic bacteria between 0.5 and 0.0625 μg, and the growth inhibition effect was observed in a concentration-dependent species.

Simultaneous fluorescence imaging monitoring of the programmed release of dual drugs from a hydrogel-carbon nanotube delivery system

Multispectral fluorescence imaging, from cellular imaging to in vivo imaging, represents a significant advancement for drug delivery research. Tracking multi-drug release using real-time imaging in vivo can reveal the release processes for guiding the design of an ideal drug delivery system to implement combination chemotherapy. Herein, a sustained and programmed drug delivery system was developed based on a PCL-PEG-PCL thermosensitive hydrogel combined with chitosan-multiwalled carbon nanotubes using doxorubicin (DOX) and rhodamine B (RB) as the model drugs. Dual drug delivery was monitored by fluorescence imaging at the cellular level, and in vivo fluorescence signals in nude mice were tracked by a multispectral fluorescence imaging system. The results demonstrated that the release of these two drugs can be dynamically tracked in vitro and in vivo, respectively using fluorescence imaging techniques. After loading onto carbon nanotubes, DOX exerted a significantly slower release rate compared with RB in the hydrogel due to the dual release of DOX. The hydrogel-carbon nanotube delivery system achieved programmed release of DOX and RB, which affirmed that it can be a potential drug delivery system with programmed release for combined administration.

A Sandwiched Immunosensor for Highly Selective and Sensitive Detection of Alpha-Fetoprotein By Using CdTe@SiO2/GO Electrochemiluminescence Probes

Alpha-fetoprotein (AFP), mainly synthesized in fetal liver, was a highly specific and heightened sensitive tumor marker for primary liver cancer. The increase of the AFP concentration in adult serum may be an early sign of some cancer diseases. Therefore, it is necessary to detect its concentration in clinical diagnosis to improve diagnostic accuracy and efficiency. Currently, many analytical techniques have been developed as a standard method for the determination of AFP, including Enzyme-linked immunoassay, time-resolved fluoroimmunoassay, surface plasmon resonance, atomic absorption spectroscopy, chemiluminescence fluorescence method, high-performance liquid chromatography (HPLC), and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS), which are sensitive and accurate. However, these methods typically require well-equipped laboratory facilities, time-consuming sample pretreatment and skilled operators, which significantly limit the applications for fast-screening of large amounts of practical samples. Herein, an ultrasensitive sandwich-type electrochemiluminescence (ECL) biosensor for the analysis of Alpha-fetoprotein (AFP) antigen was fabricated based on CdTe doped silica nanoparticles on graphene oxide (CdTe@SiO2/GO) nanocomposites as carrier to immobilize labeled AFP antibody and chitosan/multi-walled carbon nanotubes (CS/MWCNTs) composite as carrier to immobilize capture AFP antibody. In this project, capture antibodies were immobilized through covalent combination which could catch the target AFP protein as much as possible. High ECL signal could be obtained due to the luminant CdTe@SiO2/GO produced larges number of the emission photons. Because of its good conductivity and high surface area, the CS/MWCTs composite material, on the one hand, accelerated the electron transfer rate of electrode surface, on the other hand, it improved the loading rate of capture antibody and labeled antibody, thus further obtaining the high ECL intensity and improving the sensitivity of the sensor. In this strategy, under optimized conditions, the ECL intensity increased with the logarithmic values of AFP standard concentrations from 1.0 pg·mL-1 to 100 ng·mL-1 with a detection limit of 0.22 pg·mL-1 (at an S/N ratio of 3). The ECL immunosensor provided detection method with satisfactory recoveries, excellent reproducibility and stability, indicating that this method had a prospect in the practical application in the clinical diagnosis of AFP. Figure 1

Functionalized multiwalled carbon nanotubes by loading phosphorylated chitosan

Novel flame-retardant phosphorylated chitosan-multiwalled carbon nanotubes (PCS-MWCNTs) were obtained by the loading of PCS on the surface of MWCNTs by a chemical deposition cross-linking method. A series of polyethylene terephthalate (PET) composites were prepared by melt compounding with MWCNTs or PCS-MWCNTs to investigate the flame-retardant properties. Field-emission scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared (FTIR) spectrometry were employed to characterize the morphology, chemical structure, and functionalization effect of MWCNTs. The coating degree and thermal stability of PCS-MWCNTs were investigated by thermogravimetric analysis (TGA). Thermal decomposition products after TGA and flame-retardant properties of PET composites were characterized by FTIR and CONE measurements, respectively. The results indicated that PCS is loaded on the MWCNT surface. Modified PCS-MWCNTs exhibited better dispersion and efficient flame retardancy. TGA data indicated that PCS-MWCNTs can enhance the onset temperature of PET and increase the amount of the char residues. The char residue with 1 wt% PCS-MWCNTs/PET increased from 12.62% (pure PET) to 15.46%. The analysis of the decomposition products and morphology of the char residue indicated that PCS-MWCNTs not only retain the effect of alternating couplet carbon (C) and physical barrier by MWCNTs, but also form P–C compounds, improving the flame retardancy of PET. CONE tests demonstrated that the PCS-MWCNTs lead to the efficient decrease in the flammability parameters, such as the heat release rate (HRR), total release heat rate (THR), total smoke production (TSP), mean mass loss rate (MMLR), and the total combustion time. The peak HRR value decreased from 513.22 kW m−2 to 341 kW m−2. The THR, TSP, and MMLR values decreased by 20.38 MJ m−2, 1.1 m2, and 1.32 g s−1, respectively. The total combustion time decreased by 98 s, from 388 s to 290 s, indicating that PCS-MWCNTs extinguish fire.

Multiwalled Carbon Nanotube-Chitosan Scaffold: Cytotoxic, Apoptoti c, and Necrotic Effects on Chondrocyte Cell Lines.

Carbon nanotubes (CNTs) have been considered highly successful and proficient in terms of their mechanical, thermal and electrical functionalization and biocompatibility. In regards to their significant extent in bone regeneration, it has been determined that CNTs hold the capability to endure clinical applications through bone tissue engineering and orthopedic procedures. In the present study, we report on a composite preparation, involving the use of CNT-chitosan as scaffold for bone repair and regeneration. Through the use of water-soluble tetrazolium salt (WST-1) and double staining methods, the cytotoxic, necrotic, and apoptotic effects of chitosan-multiwalled carbon nanotube nanocomposites on the chondrocyte ATTC cell line have been exhibited. The chitosan-multiwalled carbon nanotube scaffolds were prepared. Chondrocytes differentiation tool (ATCC) cell line was prepared. WST-1 assay for cytotoxicity studies were performed by using chondrocytes cells in 12.5-200 μL concentration range. The samples of membranes (chitosan- multiwalled carbon nanotube scaffold) were measured at 2 mg/mL and further prepared amongst chitosan- multiwalled carbon nanotube scaffold's which were placed into separate wells. While in the process of incubation, in the four-hour time range, the plates were immediately read in an Elisa microplate Reader. To predict the number of apoptotic and necrotic cells in culture, the technique of double staining with Hoechst dye was performed with PI on the basis of scoring cell nuclei. The mechanical properties such as tensile strength and elongation at break values of the chitosan only and chitosan/CNT scaffolds were evaluated on Texture Analyzer. Based on the results of the WST-1 assay procedure, the amount of cell viability was not significantly affected by nanocomposite concentrations and the lowest mortality rate of cells was obtained at a concentration of 12.5 μg/mL, whereas the highest mortality rate was obtained at a rate of 200 μg/mL. In addition, the effects of chitosan-CNT nanocomposites were not found to cytotoxic on chondrocyte cells. The double staining method has been able to determine the apoptotic and necrotic effects of chitosan MWCNT nanocomposites. The apoptotic and necrotic effects of the combined compounds had varied within the concentrations. In a similar manner to the outcome of the control groups, apoptosis was obtained at a percentage of 2.67%. Under a fluorescent inverted microscope, the apoptotic cell nuclei were stained with a stronger blue fluorescence in comparison to non-apoptotic cells, which may have had an effect. We also compared the strain-stress curve measurements results. The results indicated that the mechanical properties of scaffold were not different. Elongation at break values increased by addition of CNT. CNTs as a biomaterial hold the potential to be used for applications in future regenerative medicine. By using the components of chondrocytes (ATTC) cell lines, the cytotoxicity evaluations were made for the chitosan-multiwalled carbon nanotube scaffold. The chitosan-MWCNT nanocomposites do not seem to induce drastic cytotoxicity to the chondrocyte cells.

Thermosensitive hydrogel loaded with chitosan-carbon nanotubes for near infrared light triggered drug delivery

Controlled drug release with on demand is an important challenge for drug delivery. Near-infrared (NIR) light triggered drug delivery reflected the development of a significant strategy to control drug release based on photothermal effects. Herein, a sustained and controlled drug delivery system was developed based on a PCL–PEG–PCL thermosensitive hydrogel combined with chitosan-multiwalled carbon nanotubes for a near infrared light triggered drug delivery. Carbon nanotubes that incorporate hydrogel can enhance the sustained effect of drug delivery by a dual-stage release and allow drug delivery by controlling light irradiation. This in situ photothermal process was monitored by thermal imaging and the controlled drug delivery of doxorubicin was tracked in real-time by fluorescence imaging in vivo based on the fluorescence ability of the drug using nude mice as models. The results suggest that the photothermal effect of the carbon nanotubes can disrupt the structure of the hydrogel with a gel–sol transition, triggering the release of the drug from the sustained drug delivery system by NIR irradiation while responding on demand. The sustained and controlled drug delivery has the potential to implement the accurate administration of hydrogel-based drug delivery systems.