Preparation of conductive polyaniline/graphene nanocomposites via in situ emulsion polymerization and product characterization

Cold atmospheric plasma modification and electrical conductivity induction in gelatin/polyvinylidene fluoride nanofibers for neural tissue engineering

BACKGROUND

This research follows some investigations through neural tissue engineering, including fabrication, surface treatment, and evaluation of novel self-stimuli conductive biocompatible and degradable nanocomposite scaffolds.

METHODS

Gelatin as a biobased material and polyvinylidene fluoride (PVDF) as a mechanical, electrical, and piezoelectric improvement agent were co-electrospun. In addition, polyaniline/graphene (PAG) nanoparticles were synthesized and added to gelatin solutions in different percentages to induce electrical conductivity. After obtaining optimum PAG percentage, cold atmospheric plasma (CAP) treatment was applied over the best samples by different plasma variable parameters. Finally, the biocompatibility of the scaffolds was analyzed and approved by in vitro tests using two different PC12 and C6 cell lines. In the present study the morphology, FTIR, dynamic light scattering, mechanical properties, wettability, contact angle tests, differential scanning calorimetric, rate of degradation, conductivity, biocompatibility, gene expression, DAPI staining, and cell proliferation were investigated.

RESULTS

The PAG percentage optimization results revealed fiber diameter reduction, conductivity enhancement, young's modulus improvement, hydrophilicity devaluation, water uptake decrement, and degradability reduction in electrospun nanofibers by increasing the PAG concentration. Furthermore, ATR-FTIR, FE-SEM, AFM, and contact angle tests revealed that helium CAP treatment improves scaffold characterizations for 90 s in duration time. Furthermore, the results of the MTT assay, FE-SEM, DAPI staining, and RT-PCR revealed that samples containing 2.5% w/w of PAG are the most biocompatible, and CAP treatment increases cell proliferation and improves neural gene expression in the differentiation medium.

CONCLUSIONS

According to the results, the samples with the 2.5% w/w of PAG could provide a suitable matrix for neural tissue engineering in terms of physicochemical and biological.

Conductive multichannel PCL/gelatin conduit with tunable mechanical and structural properties for peripheral nerve regeneration

Peripheral nerve injuries remain among the most challenging medical issues despite numerous efforts to devise methods in fabrication of nerve conduits to functionally regenerate axonal defects. In this regard, the current study offers a holistic perspective in design by considering the mechanical, topographical and structural aspects which are crucial for a successful nerve guide conduit. Poly(e‐caprolactone) and gelatin were employed to serve this purpose in the form of dual‐electrospun films which were rolled and later shaped the assembly of a multichannel conduit. Polyaniline/graphene (PAG) nanocomposite was incorporated to endow the conduit with conductive properties. FTIR analysis, water contact angle measurements, and SEM observations as well as mechanical and conductivity tests were used to evaluate the properties of the conduits. In addition, MTT assay was conducted to assess the proliferation of rat bone marrow‐derived mesenchymal stem cells cultured on the films. Incorporating 2% PAG proved to have superior cell support and proliferation, while guaranteeing electrical conductivity of 10.8 × 10−5 S/cm and remarkable tensile strength of 3.52 ± 1.3 MPa and 14.12 ± 3.1 MPa for wet and dry conditions, respectively. Overall, the observed results highlight the great potential of the fabricated conduit to be used as a candidate for peripheral nerve defects.

Tuning of the electrocatalytic characteristics of PANI/Fe2O3 composite coating for alkaline hydrogen evolution reaction

The paper reports a simple and cost-effective strategy for the development of a stable and reproducible PANI/Fe2O3 composite coating as an efficient electrode for the electrocatalytic alkaline hydrogen evolution reaction (HER). The surface characteristics of the developed PANI/Fe2O3 composite coatings are tuned to achieve high hardness (510 HVN), thickness (26 μm), porosity, and surface roughness (Sa = 3.760 μm). The PANI/Fe2O3 composite coating with tuned surface characteristics (PANI/Fe2O3-2GL) facilitates the effective conduction of electrons from a highly conducting polymer to a metal. This increases the electron density on the coating surface and enhances the active surface area, which effectively enhances the hydrogen adsorption efficiency on the coating surface to improve HER activity. The composite coating exhibits enhanced HER activity with low overpotential (110 mV) and high exchange current density (95.32 mA cm-2). The mechanism of HER on the coating surface follows the Volmer-Heyrovsky reaction with the Heyrovsky step as the rate-determining step. The stability of the composite coating under aggressive reaction conditions even after long-term HER confirms its competency with commercial electrocatalysts.

Electronic Nose Based on Carbon Nanocomposite Sensors for Clove Essential Oil Detection

This work describes the development of an electronic nose (e-nose) based on carbon nanocomposites to detect clove essential oil (CEO), eugenol (EUG), and eugenyl acetate (EUG.ACET). Our e-nose system comprises an array of six sensing units modified with nanocomposites of poly(aniline), graphene oxide, and multiwalled carbon nanotubes doped with different acids, dodecyl benzene sulfonic acid, camphorsulfonic acid, and hydrochloric acid. The e-nose presented an excellent analytical performance to the detected analytes (CEO, EUG, and EUG.ACET) with high sensitivity and reversibility. The limit of detection was lower than 1.045 ppb, with response time (<13.26 s) and recovery time (<106.29 s) and low hysteresis. Information visualization methods (PCA and IDMAP) demonstrated that the e-nose was efficient to discriminate the different concentrations of analyte volatile oil compounds. PM-IRRAS measurements suggest that the doping mechanism of molecular architectures is composed of a change in the oscillation energy of the characteristic dipoles and changes in the molecular orientation dipoles C═C and C═O at 1615 and 1740 cm^-1, respectively. The experimental results indicate that our e-nose system is promising for a rapid analysis method to monitor the quality of essential oils.

Bioinspired Nanofiber Scaffold for Differentiating Bone Marrow-Derived Neural Stem Cells to Oligodendrocyte-Like Cells: Design, Fabrication, and Characterization

BACKGROUND

Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue accessibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging.

PURPOSE

In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced.

MATERIALS AND METHODS

In order to achieve a sustained release of T3, this factor was encapsulated within chitosan nanoparticles and chitosan-loaded T3 was incorporated within PCL nanofibers. Polyaniline graphene (PAG) nanocomposite was incorporated within gelatin nanofibers to endow the scaffold with conductive properties, which resemble the conductive behavior of axons. Biodegradation, water contact angle measurements, and scanning electron microscopy (SEM) observations as well as conductivity tests were used to evaluate the properties of the prepared scaffold. The concentration of PAG and T3-loaded chitosan NPs in nanofibers were optimized by examining the proliferation of cultured bone marrow-derived mesenchymal stem cells (BMSCs) on the scaffolds. The differentiation of BMSCs-derived NSCs cultured on the fabricated scaffolds into OLCs was analyzed by evaluating the expression of oligodendrocyte markers using immunofluorescence (ICC), RT-PCR and flowcytometric assays.

RESULTS

Incorporating 2% PAG proved to have superior cell support and proliferation while guaranteeing electrical conductivity of 10.8 × 10-5 S/cm. Moreover, the scaffold containing 2% of T3-loaded chitosan NPs was considered to be the most biocompatible samples. Result of ICC, RT-PCR and flow cytometry showed high expression of O4, Olig2, platelet-derived growth factor receptor-alpha (PDGFR-α), O1, myelin/oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) high expressed but low expression of glial fibrillary acidic protein (GFAP).

CONCLUSION

Considering surface topography, biocompatibility, electrical conductivity and gene expression, the hybrid PCL/gelatin scaffold with the controlled release of T3 may be considered as a promising candidate to be used as an in vitro model to study patient-derived oligodendrocytes by isolating patient's BMSCs in pathological conditions such as diseases or injuries. Moreover, the resulted oligodendrocytes can be used as a desirable source for transplanting in patients.

A, Haddadi SA, Ghaderi S, Azamian F. In situ emulsion polymerization and characterization of PVAc nanocomposites including colloidal silica nanoparticles for wood specimens bonding

Polyvinyl acetate (PVAc) nanocomposites for wood adhesives containing different amounts of colloidal silica nanoparticles (CSNs) were synthesized via in situ one‐step emulsion polymerization. The adhesion strength of wood specimens bonded by PVAc nanocomposites was investigated by the tensile test. Thermal properties of PVAc nanocomposites were also characterized by differential scanning calorimetry and thermogravimetric analysis. Rheological and morphological properties of the PVAc nanocomposites were investigated using rheometric mechanical spectrometry and field emission scanning electron microscopy (FESEM), respectively. The obtaining results showed that the shear strength of PVAc nanocomposite including 1 wt. % CSNs has the highest shear and tensile strength about 4.7 and 3.2 MPa, respectively. A small increment of Tg (~3 °C) and considerable increment of the ash content proved the enhancement of PVAc thermal characterization in the presence of CSNs. FESEM results showed uniform dispersion of nanoparticles throughout the PVAc matrix due to using the in situ emulsion polymerization process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48570.

A Review on Biomaterials for 3D Conductive Scaffolds for Stimulating and Monitoring Cellular Activities

During the last years, scientific research in biotechnology has been reporting a considerable boost forward due to many advances marked in different technological areas. Researchers working in the field of regenerative medicine, mechanobiology and pharmacology have been constantly looking for non-invasive methods able to track tissue development, monitor biological processes and check effectiveness in treatments. The possibility to control cell cultures and quantify their products represents indeed one of the most promising and exciting hurdles. In this perspective, the use of conductive materials able to map cell activity in a three-dimensional environment represents the most interesting approach. The greatest potential of this strategy relies on the possibility to correlate measurable changes in electrical parameters with specific cell cycle events, without affecting their maturation process and considering a physiological-like setting. Up to now, several conductive materials has been identified and validated as possible solutions in scaffold development, but still few works have stressed the possibility to use conductive scaffolds for non-invasive electrical cell monitoring. In this picture, the main objective of this review was to define the state-of-the-art concerning conductive biomaterials to provide researchers with practical guidelines for developing specific applications addressing cell growth and differentiation monitoring. Therefore, a comprehensive review of all the available conductive biomaterials (polymers, carbon-based, and metals) was given in terms of their main electric characteristics and range of applications.

Design and fabrication of conductive nanofibrous scaffolds for neural tissue engineering: Process modeling via response surface methodology

Peripheral nervous system in contrary to central one has the potential for regeneration, but its regrowth requires proper environmental conditions and supporting growth factors. The aim of this study is to design and fabricate a conductive polyaniline/graphene nanoparticles incorporated gelatin nanofibrous scaffolds suitable for peripheral nervous system regeneration. The scaffolds were fabricated with electrospinning and the fabrication process was designed with Design-Expert software via response surface methodology. The effect of process parameters including applied voltage (kV), syringe pump flow rate (cm3/h), and PAG concentration (wt%), on the scaffold conductivity, nanofibers diameter, and cell viability were investigated. The obtained results showed that the scaffold conductivity and cell viability are affected by polyaniline/graphene concentration while nanofiber diameter is more affected by the applied voltage and syringe pump flow rate. Optimum scaffold with maximum conductivity (0.031 ± 0.0013 S/cm) and cell compatibility and suitable diameter were electrospun according to the software introduced values for the process parameters (voltage of 13 kV, flow rate of 0.1 cm3/h, and PAG wt.% of 1.3) and its morphology, cell compatibility, and biodegradability were further investigated, which showed its potential for applying in peripheral nervous system injury regeneration.

Electrochemical and surface evaluation of the anti-corrosion properties of reduced graphene oxide

Herein, reduced graphene oxide nanosheets (RGON) were electrochemically grown onto a carbon steel alloy from graphene oxide (GO)​ and the anti-corrosion performance of the RGON-deposited layers was evaluated.

Fabrication and characterization of conductive chitosan/gelatin-based scaffolds for nerve tissue engineering

This paper reports on the development of conductive porous scaffolds by incorporating conductive polyaniline/graphene (PAG) nanoparticles into a chitosan/gelatin matrix for its potential application in peripheral nerve regeneration. The effect of PAG content on the various properties of the scaffold is investigated and the results showed that the electrical conductivity and mechanical properties increased proportional to the increase in the PAG loading, while the porosity, swelling ratio and in vitro biodegradability decreased. In addition, the biocompatibility was evaluated by assessing the adhesion and proliferation of Schwann cells on the prepared scaffolds using SEM and MTT assay, respectively. In summary, this work supports the use of a porous conductive chitosan/gelatin/PAG scaffold with a low amount of PAG (2.5 wt.%) as a suitable material having proper conductivity, mechanical properties and biocompatibility that may be appropriate for different biomedical applications such as scaffold material in tissue engineering for neural repair or other biomedical devices that require electroactivity.