Carbon Nanotube Nanocomposites with Highly Enhanced Strength and Conductivity for Flexible Electric Circuits

Ligand-targeted fishing of α-glucosidase inhibitors from Tribulus terrestris L. based on chitosan-functionalized multi-walled carbon nanotubes with immobilized α-glucosidase

α-Glucosidase inhibitors in natural products are one of the promising drugs for the treatment of type 2 diabetes. However, due to the complexity of the matrix, it is challenging to comprehensibly clarify the specific pharmacodynamic substances. In this study, a novel high-throughput inhibitor screening strategy was established based on covalent binding of α-glucosidase on chitosan-functionalized multi-walled carbon nanotubes coupled with high-resolution mass spectrometry. The synthesized MWCNTs@CS@GA@α-Glu was characterized by TEM, SEM, FTIR, Raman, and TG. Performance studies showed that the microreactor exhibited stronger thermostability and pH tolerance than that of the free one while maintaining its inherent catalytic activity. Feasibility study applying a model mixture of known α-glucosidase ligand and non-ligands indicated the selectivity and specificity of the system. By integrating ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-QTOF-MS) with ion mobility mass spectrometry (IMS), 15 ligands were obtained and tentatively identified from Tribulus terrestris L., including 8 steroidal saponins, 4 flavonoids, and 3 alkaloids. These inhibitors were further validated by in vivo experiments and molecular docking simulation.

Electroanalytical biosensor based on GOx/FCA/PEG-modified SWCNT electrode for determination of glucose

This paper describes a simple electrochemical sensing platform based on single-walled carbon nanotube (SWCNT) electrodes for glucose detection. The device fabrication using O2-plasma treatment allows precision and uniformity for the construction of three SWCNT electrodes on the flexible plastic substrate. Glucose assay can be simply accomplished by introducing a glucose sample into the fabricated biosensor. The marked electrocatalytic and biocompatible properties of biosensors based on SWCNT electrodes with the incorporation of ferrocenecarboxylic acid and polyethylene glycol enable effective amperometric measurement of glucose at a low oxidation potential (0.3 V) with low interferences from coexisting species. The device shows efficient electroanalytical performances with high sensitivity (5.5 μA·mM−1·cm−2), good reproducibility (CV less than 3%), and long-term stability (over a month). A linear range of response was found from 0 to 10 mM of glucose with a fast response time of 10 s. This attractive electroanalytical device based on GOx/FCA/PEG/SWCNT electrodes offers a promising system to facilitate a new approach for diverse biosensors and electrochemical devices.

Wearable CNTs-based humidity sensors with high sensitivity and flexibility for real-time multiple respiratory monitoring

Sensors, such as optical, chemical, and electrical sensors, play an important role in our lives. While these sensors already have widespread applications, such as humidity sensors, most are generally incompatible with flexible/inactive substrates and rely on conventional hard materials and complex manufacturing processes. To overcome this, we develop a CNT-based, low-resistance, and flexible humidity sensor. The core-shell structured CNT@CPM is prepared with Chit and PAMAM to achieve reliability, accuracy, consistency, and durability, resulting in a highly sensitive humidity sensor. The average response/recovery time of optimized sensor is only less than 20 s, with high sensitivity, consistent responsiveness, good linearity according to humidity rates, and low hysteresis (- 0.29 to 0.30 %RH). Moreover, it is highly reliable for long-term (at least 1 month), repeated bending (over 15,000 times), and provides accurate humidity measurement results. We apply the sensor to smart-wear, such as masks, that could conduct multi-respiratory monitoring in real-time through automatic ventilation systems. Several multi-respiratory monitoring results demonstrate its high responsiveness (less than 1.2 s) and consistent performance, indicating highly desirable for healthcare monitoring. Finally, these automatic ventilation systems paired with flexible sensors and applied to smart-wear can not only provide comfort but also enable stable and accurate healthcare in all environments.

Electrical and thermal stimulus-responsive nanocarbon-based 3D hydrogel sponge for switchable drug delivery

Smart hydrogels that are responsive to various external (e.g. electrical and/or thermal) stimulation have become increasingly popular in recent years for simple, rapid, and precise drug delivery that can be controlled and turned on or off with external stimuli. For such a switchable drug delivery material, highly homogeneous dispersion and distribution of the hydrophobic, electrically conductive nanomaterials throughout a hydrophilic three-dimensional (3D) hydrogel network remains a challenge and is essential for achieving well-connected electrical and thermal conducting paths. Herein we developed electrical and thermal stimulus-responsive 3D hydrogels based on (i) carbon nanotubes (CNTs) as the core unit and an electrical/thermal conductor, (ii) chitosan (Chit) as the shell unit and a hydrophilic dispersant, and (iii) poly(NIPAAm-co-BBVIm) (pNIBBIm) as the drug carrier and a temperature-responsive copolymer. By formulating the CNT-core and Chit-shell units and constructing a CNT sponge framework, uniform distribution and 3D connectivity of the CNTs were improved. The 3D hydrogel based on the CNT sponge, namely the 3D frame CNT-Chit/pNIBBIm hydrogel, delivered approximately 37% of a drug, ketoprofen used for the treatment of musculoskeletal pain, during about 30% shrinkage after electrical and thermal switches on/off and exhibited the best potential for future use in a smart transdermal drug delivery system. The physicochemical, mechanical, electrical, thermal, and biocompatible characteristics of this nanocarbon-based 3D frame hydrogel led to remarkable electrical and thermal stimulus-responsive properties capable of developing an excellent controllable and switchable drug delivery platform for biomedical engineering and medicine applications.

Injectable and conductive cardiac patches repair infarcted myocardium in rats and minipigs

Cardiac patches can help to restore the electrophysiological properties of the heart after myocardial infarction. However, scaffolds for the repair of heart muscle typically require surgical implantation or, if they are injectable, they are not electrically conductive or do not maintain their shape or function. Here, we report the performance, as demonstrated for the repair of infarcted heart muscle in rats and minipigs, of injectable and conductive scaffolds consisting of methacrylated elastin and gelatin, and carbon nanotubes that display shape-memory behaviour, a hierarchical porous structure and a negligible Poisson's ratio. In rats, the implantation of cell-free patches or patches seeded with rat cardiomyocytes onto the myocardium after ligation of the left anterior descending coronary artery led to functional repair after 4 weeks, as indicated by increases in fractional shortening and the ejection fraction, and by a decrease in the infarcted area. We also observed measures of functional recovery in minipigs with infarcted hearts after the delivery of cell-free patches or patches incorporating cardiomyocytes differentiated from human pluripotent stem cells.

Therapeutic tissue regenerative nanohybrids self-assembled from bioactive inorganic core / chitosan shell nanounits

Natural inorganic/organic nanohybrids are a fascinating model in biomaterials design due to their ultra-microstructure and extraordinary properties. Here, we report unique-structured nanohybrids through self-assembly of biomedical inorganic/organic nanounits, composed of bioactive inorganic nanoparticle core (hydroxyapatite, bioactive glass, or mesoporous silica) and chitosan shell - namely Chit@IOC. The inorganic core thin-shelled with chitosan could constitute as high as 90%, strikingly contrasted with the conventional composites. The Chit@IOC nanohybrids were highly resilient under cyclic load and resisted external stress almost an order of magnitude effectively than the conventional composites. The nanohybrids, with the nano-roughened surface topography, could accelerate the cellular responses through stimulated integrin-mediated focal adhesions. The nanohybrids were also able to load multiple therapeutic molecules in the core and shell compartment and then release sequentially, demonstrating controlled delivery systems. The nanohybrids compartmentally-loaded with therapeutic molecules (dexamethasone, fibroblast growth factor 2, and phenamil) were shown to stimulate the anti-inflammatory, pro-angiogenic and osteogenic events of relevant cells. When implanted in the in vivo calvarium defect model with 3D-printed scaffold forms, the therapeutic nanohybrids were proven to accelerate new bone formation. Overall, the nanohybrids self-assembled from Chit@IOC nanounits, with their unique properties (ultrahigh inorganic content, nano-topography, high resilience, multiple-therapeutics delivery, and cellular activation), can be considered as promising 3D tissue regenerative platforms.

Synthesis of Carbon Nanomaterials from Biomass Utilizing Ionic Liquids for Potential Application in Solar Energy Conversion and Storage

Considering its availability, renewable character and abundance in nature, this review assesses the opportunity of the application of biomass as a precursor for the production of carbon-based nanostructured materials (CNMs). CNMs are exceptionally shaped nanomaterials that possess distinctive properties, with far-reaching applicability in a number of areas, including the fabrication of sustainable and efficient energy harnessing, conversion and storage devices. This review describes CNM synthesis, properties and modification, focusing on reports using biomass as starting material. Since biomass comprises 60-90% cellulose, the current review takes into account the properties of cellulose. Noting that highly crystalline cellulose poses a difficulty in dissolution, ionic liquids (ILs) are proposed as the solvent system to dissolve the cellulose-containing biomass in generating precursors for the synthesis of CNMs. Preliminary results with cellulose and sugarcane bagasse indicate that ILs can not only be used to make the biomass available in a liquefied form as required for the floating catalyst CVD technique but also to control the heteroatom content and composition in situ for the heteroatom doping of the materials.

Paper-Based Flexible Electrode Using Chemically-Modified Graphene and Functionalized Multiwalled Carbon Nanotube Composites for Electrophysiological Signal Sensing

Flexible paper-based physiological sensor electrodes were developed using chemically-modified graphene (CG) and carboxylic-functionalized multiwalled carbon nanotube composites (f@MWCNTs). A solvothermal process with additional treatment was conducted to synthesize CG and f@MWCNTs to make CG-f@MWCNT composites. The composite was sonicated in an appropriate solvent to make a uniform suspension, and then it was drop cast on a nylon membrane in a vacuum filter. A number of batches (0%~35% f@MWCNTs) were prepared to investigate the performance of the physical characteristics. The 25% f@MWCNT-loaded composite showed the best adhesion on the paper substrate. The surface topography and chemical bonding of the proposed CG-f@MWCNT electrodes were characterized by scanning electron microscopy (SEM) and Raman spectroscopy, respectively. The average sheet resistance of the 25% CG-f@MWCNT electrode was determined to be 75 Ω/□, and it showed a skin contact impedance of 45.12 kΩ at 100 Hz. Electrocardiogram (ECG) signals were recorded from the chest and fingertips of healthy adults using the proposed electrodes. The CG-f@MWCNT electrodes demonstrated comfortability and a high sensitivity for electrocardiogram signal detection.

Application of Biodegradable and Biocompatible Nanocomposites in Electronics: Current Status and Future Directions

With the continuous increase in the production of electronic devices, large amounts of electronic waste (E-waste) are routinely being discarded into the environment. This causes serious environmental and ecological problems because of the non-degradable polymers, released hazardous chemicals, and toxic heavy metals. The appearance of biodegradable polymers, which can be degraded or dissolved into the surrounding environment with no pollution, is promising for effectively relieving the environmental burden. Additionally, biodegradable polymers are usually biocompatible, which enables electronics to be used in implantable biomedical applications. However, for some specific application requirements, such as flexibility, electric conductivity, dielectric property, gas and water vapor barrier, most biodegradable polymers are inadequate. Recent research has focused on the preparation of nanocomposites by incorporating nanofillers into biopolymers, so as to endow them with functional characteristics, while simultaneously maintaining effective biodegradability and biocompatibility. As such, bionanocomposites have broad application prospects in electronic devices. In this paper, emergent biodegradable and biocompatible polymers used as insulators or (semi)conductors are first reviewed, followed by biodegradable and biocompatible nanocomposites applied in electronics as substrates, (semi)conductors and dielectrics, as well as electronic packaging, which is highlighted with specific examples. To finish, future directions of the biodegradable and biocompatible nanocomposites, as well as the challenges, that must be overcome are discussed.

Novel Ionic Liquid-Functionalized Chitosan [DSIM][AlCl3] x -@CS: Synthesis, Characterization, and Catalytic Application for Preparation of Substituted Pyrazine Derivatives

Pyrazines are renowned heterocyclic compounds that have played an important role in drug design and are part of many polycyclic compounds of biological and industrial significance. In this article, a novel chitosan-immobilized ionic liquid, [DSIM][AlCl₃] _x ^-@CS, has been synthesized easily at ambient temperature and used for catalyzing the synthesis of a series of biologically relevant pyrazine derivatives. The catalyst is well characterized by various techniques such as Fourier transform infrared spectroscopy, Raman spectroscopy, solid-state ¹³C MAS nuclear magnetic resonance, scanning electron microscopy/energy-dispersive X-ray, elemental mapping, transmission electron microscopy, powder X-ray diffraction, and thermal gravimetric analyses. The advantageous features of the present energy-sustainable methodology include high yield of product (>99%), shorter reaction time periods, and recyclability of the catalyst.

Printing Carbon Nanotube-Embedded Silicone Elastomers via Direct Writing

Direct writing techniques for the printing of colloidal multiwalled carbon nanotubes (CNTs) embedded in polydimethylsiloxane (PDMS) were developed herein to fabricate complex structures including woodpiles, tetragonal scaffolds, and gradient mesh structures. The multiwalled CNTs served as a conductive filler and thickening agent for the printing ink. A suitable rheological behavior was obtained by mixing the CNTs with PDMS dissolved in an isopropyl alcohol solvent. A 7 wt % CNT loading in the PDMS was optimum for printing gap-spanning features at a nozzle moving speed of 20 mm/s. The printed structures, including a woodpile and gradient mesh structure, were capable of detecting changes in external mechanical pressure. Printed CNT/PDMS strips exhibit electrical actuation with good mechanical performance (strain of 8.9%) at a low actuation voltage (60 V). The performance characterization and application display demonstrated the possibility of developing custom complex CNT/PDMS structures for a broad range of applications, including soft robots and flexible electronic devices.

Simple and cost-effective method of highly conductive and elastic carbon nanotube/polydimethylsiloxane composite for wearable electronics

The development of various flexible and stretchable materials has attracted interest for promising applications in biomedical engineering and electronics industries. This interest in wearable electronics, stretchable circuits, and flexible displays has created a demand for stable, easily manufactured, and cheap materials. However, the construction of flexible and elastic electronics, on which commercial electronic components can be mounted through simple and cost-effective processing, remains challenging. We have developed a nanocomposite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS) elastomer. To achieve uniform distributions of CNTs within the polymer, an optimized dispersion process was developed using isopropyl alcohol (IPA) and methyl-terminated PDMS in combination with ultrasonication. After vaporizing the IPA, various shapes and sizes can be easily created with the nanocomposite, depending on the mold. The material provides high flexibility, elasticity, and electrical conductivity without requiring a sandwich structure. It is also biocompatible and mechanically stable, as demonstrated by cytotoxicity assays and cyclic strain tests (over 10,000 times). We demonstrate the potential for the healthcare field through strain sensor, flexible electric circuits, and biopotential measurements such as EEG, ECG, and EMG. This simple and cost-effective fabrication method for CNT/PDMS composites provides a promising process and material for various applications of wearable electronics.

Thermo conductive carbon nanotube-framed membranes for skin heat signal-responsive transdermal drug delivery

Smart carbon nanotube (CNT)-framed (SCNF) membranes were prepared by self-assembly of highly thermo conductive CNT molecules hybridized with chitosan (Chit) in a core–shell structure and then by chemical integration of a temperature-responsive copolymer, poly(NIPAAm-co-BVIm) (or pNIBIm), as an additional outer shell.

Chitosan nanocomposites based on distinct inorganic fillers for biomedical applications

Chitosan (CHI), a biocompatible and biodegradable polysaccharide with the ability to provide a non-protein matrix for tissue growth, is considered to be an ideal material in the biomedical field. However, the lack of good mechanical properties limits its applications. In order to overcome this drawback, CHI has been combined with different polymers and fillers, leading to a variety of chitosan-based nanocomposites. The extensive research on CHI nanocomposites as well as their main biomedical applications are reviewed in this paper. An overview of the different fillers and assembly techniques available to produce CHI nanocomposites is presented. Finally, the properties of such nanocomposites are discussed with particular focus on bone regeneration, drug delivery, wound healing and biosensing applications.