Nanotube Functionalization: Investigation, Methods and Demonstrated Applications

Exploration of the photothermal role of curcumin-loaded targeted carbon nanotubes as a potential therapy for melanoma cancer

In this research, the hydrophilic structure of multi-walled carbon nanotubes (MWCNTs) was modified by synthesizing polycitric acid (PCA) and attaching folic acid (FA) to create MWCNT-PCA-FA. This modified nanocomplex was utilized as a carrier for the lipophilic compound curcumin (Cur). Characterization techniques including TGA, TEM, and UV-visible spectrophotometry were used to analyze the nanocomplex. The mechanism of cancer cell death induced by MWCNT-PCA-FA was studied extensively using the MTT assay, colony formation analysis, cell cycle assessment via flow cytometry, and apoptosis studies. Furthermore, we assessed the antitumor efficacy of these targeted nanocomplexes following exposure to laser radiation. The results showed that the nanocomposites and free Cur had significant toxicity on melanoma cancer cells (B16F10 cells) while having minimal impact on normal cells (NHDF cells). This selectivity for cancerous cells demonstrates the potential of these compounds as therapeutic agents. Furthermore, MWCNT-PCA-FA/Cur showed superior cytotoxicity compared to free Cur alone. Colony formation studies confirmed these results. The researchers found that MWCNT-FA-PCA/Cur effectively induced programmed cell death. In photothermal analysis, MWCNT-PCA-FA/Cur combined with laser treatment achieved the highest mortality rate. These promising results suggest that this multifunctional therapeutic nanoplatform holds the potential for combination cancer therapies that utilize various established therapeutic methods.

L-Lactate Electrochemical Biosensor Based on an Integrated Supramolecular Architecture of Multiwalled Carbon Nanotubes Functionalized with Avidin and a Recombinant Biotinylated Lactate Oxidase

L-Lactate is an important bioanalyte in the food industry, biotechnology, and human healthcare. In this work, we report the development of a new L-lactate electrochemical biosensor based on the use of multiwalled carbon nanotubes non-covalently functionalized with avidin (MWCNT-Av) deposited at glassy carbon electrodes (GCEs) as anchoring sites for the bioaffinity-based immobilization of a new recombinant biotinylated lactate oxidase (bLOx) produced in Escherichia coli through in vivo biotinylation. The specific binding of MWCNT-Av to bLOx was characterized by amperometry, surface plasmon resonance (SPR), and electrochemical impedance spectroscopy (EIS). The amperometric detection of L-lactate was performed at -0.100 V, with a linear range between 100 and 700 µM, a detection limit of 33 µM, and a quantification limit of 100 µM. The proposed biosensor (GCE/MWCNT-Av/bLOx) showed a reproducibility of 6.0% and it was successfully used for determining L-lactate in food and enriched serum samples.

Modified toxic potential of multi-walled carbon nanotubes to zebrafish (Danio rerio) following a two-year incubation in water

Multi-walled carbon nanotubes (MWCNTs), widely used in several industrial fields, are not readily degradable thus, persist in environmental matrices, serving as a source of environmental toxicity to organisms. However, the effects of environmental weathering on nanomaterial toxicity remain unclear. Herein, we prepared aged-MWCNTs (a-CNTs) by incubating commercial pristine-MWCNTs (p-CNTs) for two years and compared their changes in physicochemical properties and toxic effects on zebrafish. The characterization of a-CNTs by transmission electron microscopy, X-ray photoelectron spectra, Raman spectroscopy, and Fourier-transform infrared spectroscopy showed an increased surface area, pore size, structural defects, and surface oxidation than those of p-CNTs. Zebrafish were exposed to 100 mg/L p-CNT and a-CNT for four days. Subsequently, the mRNA expression of antioxidant enzymes, including cat, gst, and sod, in a-CNT group increased by 1.5- to 1.7-fold, consistent with increased expression of genes associated with inflammation (interleukin-8) and apoptosis (p53) compared to control. The higher toxicity of a-CNTs to zebrafish than p-CNT might be due to the increased oxidative potential by altered physicochemical properties. These findings provide new insights into the risk assessment and environmental management of MWCNTs in the aquatic environment. However, further testing at environmentally relevant doses, different exposure durations, and diverse weathering parameters is warranted.

Functionalized Fullerenes and Their Applications in Electrochemistry, Solar Cells, and Nanoelectronics

Carbon-based nanomaterials have rapidly advanced over the last few decades. Fullerenes, carbon nanotubes, graphene and its derivatives, graphene oxide, nanodiamonds, and carbon-based quantum dots have been developed and intensively studied. Among them, fullerenes have attracted increasing research attention due to their unique chemical and physical properties, which have great potential in a wide range of applications. In this article, we offer a comprehensive review of recent progress in the synthesis and the chemical and physical properties of fullerenes and related composites. The review begins with the introduction of various methods for the synthesis of functionalized fullerenes. A discussion then follows on their chemical and physical properties. Thereafter, various intriguing applications, such as using carbon nanotubes as nanoreactors for fullerene chemical reactions, are highlighted. Finally, this review concludes with a summary of future research, major challenges to be met, and possible solutions.

Two birds with one stone: integrating exfoliation and immunoaffinity properties in multi-walled carbon nanotubes by non-covalent functionalization with human immunoglobulin G

An innovative strategy is proposed to simultaneously exfoliate multi-walled carbon nanotubes (MWCNTs) and generate MWCNTs with immunoaffinity properties. This strategy was based on the non-covalent functionalization of MWCNTs with human immunoglobulin G (IgG) by sonicating 2.5 mg mL^-1 MWCNTs in 2.0 mg mL^-1 IgG for 15 min with sonicator bath. Impedimetric experiments performed at glassy carbon electrodes (GCE) modified with the resulting MWCNT-IgG nanohybrid in the presence of anti-human immunoglobulin G antibody (Anti-IgG) demonstrated that the immunoglobulin retains their biorecognition properties even after the treatment during the MWCNT functionalization. We proposed, as proof-of-concept, two model electrochemical sensors, a voltammetric one for uric acid quantification by taking advantages of the exfoliated MWCNTs electroactivity (linear range, 5.0 × 10^-7 M - 5.0 × 10^-6 M; detection limit, 165 nM) and an impedimetric immunosensor for the detection of Anti-IgG through the use of the bioaffinity properties of the IgG present in the nanohybrid (linear range, 5-50 µg mL^-1; detection limit, 2 µg mL^-1).

Metal and Metal Halogenide-Filled Single-Walled Carbon Nanotubes: Kinetics, Electronic Properties, Engineering the Fermi Level

Here, we present a review of the major achievements in kinetics, electronic properties, and engineering in the Fermi level of single-walled carbon nanotubes (SWCNTs). Firstly, the kinetics of metal-filled SWCNTs were revealed with precision over several minutes. Secondly, the growth rates of nanotubes were calculated. Thirdly, the activation energies of nanotubes were measured. Fourthly, the methods of the quantitative analysis of the doping level were developed. Indeed, only qualitative analysis has been previously performed. The quantitative analysis allowed us to obtain quantitative data on charge transfer. Fifthly, the correlation between the physical properties, chemical properties, electronic properties of SWCNTs was elucidated.

Kinetics, Electronic Properties of Filled Carbon Nanotubes Investigated with Spectroscopy for Applications

The paper is dedicated to the discussion of kinetics of growth, and electronic properties of filled carbon nanotubes investigated by spectroscopy for applications. The paper starts with discussion of growth of carbon nanotubes inside metallocene-filled carbon nanotubes. Nickelocene, cobaltocene are considered for growth of carbon nanotubes. Then, the investigations of filled carbon nanotubes by four spectroscopic techniques are discussed. Among them are Raman spectroscopy, near edge X-ray absorption fine-structure spectroscopy, photoemission spectroscopy, optical absorption spectroscopy. It is discussed that metal halogenides, metal chalcogenides, metals lead to changes in electronic structure of nanotubes with n- or p-doping. The filling of carbon nanotubes with different organic and inorganic substances results in many promising applications. This review adds significant contribution to understanding of the kinetics and electronic properties of filled SWCNTs with considering new results of recent investigations. Challenges in various fields are analyzed and summarized, which shows the author's viewpoint of progress in the spectroscopy of filled SWCNTs. This is a valuable step toward applications of filled SWCNTs and transfer of existing ideas from lab to industrial scale.

Genosensing Applications of Glassy Carbon Electrodes Modified with Multi-Walled Carbon Nanotubes Non-Covalently Functionalized with Polyarginine

We report the advantages of glassy carbon electrodes (GCE) modified with multi-walled carbon nanotubes (MWCNTs) non-covalently functionalized with polyarginine (PolyArg) for the adsorption and electrooxidation of different DNAs and the analytical applications of the resulting platform. The presence of the carbon nanostructures, and mainly the charge of the PolyArg that supports them, facilitates the adsorption of calf-thymus and salmon sperm double-stranded DNAs and produces an important decrease in the overvoltages for the oxidation of guanine and adenine residues and a significant enhancement in the associated currents. As a proof-of-concept of possible GCE/MWCNTs-PolyArg biosensing applications, we develop an impedimetric genosensor for the quantification of microRNA-21 at femtomolar levels, using GCE/MWCNTs-PolyArg as a platform for immobilizing the DNA probe, with a detection limit of 3fM, a sensitivity of 1.544 × 10³ Ω M^-1, and a successful application in enriched biological fluids.

Synthesis, Sorting, and Applications of Single-Chirality Single-Walled Carbon Nanotubes

The synthesis of high-quality chirality-pure single-walled carbon nanotubes (SWCNTs) is vital for their applications. It is of high importance to modernize the synthesis processes to decrease the synthesis temperature and improve the quality and yield of SWCNTs. This review is dedicated to the chirality-selective synthesis, sorting of SWCNTs, and applications of chirality-pure SWCNTs. The review begins with a description of growth mechanisms of carbon nanotubes. Then, we discuss the synthesis methods of semiconducting and metallic conductivity-type and single-chirality SWCNTs, such as the epitaxial growth method of SWCNT ("cloning") using nanocarbon seeds, the growth method using nanocarbon segments obtained by organic synthesis, and the catalyst-mediated chemical vapor deposition synthesis. Then, we discuss the separation methods of SWCNTs by conductivity type, such as electrophoresis (dielectrophoresis), density gradient ultracentrifugation (DGC), low-speed DGC, ultrahigh DGC, chromatography, two-phase separation, selective solubilization, and selective reaction methods and techniques for single-chirality separation of SWCNTs, including density gradient centrifugation, two-phase separation, and chromatography methods. Finally, the applications of separated SWCNTs, such as field-effect transistors (FETs), sensors, light emitters and photodetectors, transparent electrodes, photovoltaics (solar cells), batteries, bioimaging, and other applications, are presented.