Magnetic carbon nanotubes: preparation, physical properties, and applications in biomedicine

Figures & data

Figure 1. Different types of SWCNTs: (a) Illustration of chiral vector and angle and (b) schematic of three ideal SWCNT structures [21].

Figure 2. Magnetization behaviour of ferromagnetic and superparamagnetic NPs under an external magnetic field. (a) Domains of a superparamagnetic and ferromagnetic NPs align with the applied external magnetic field. In the absence of an external field, ferromagnetic NPs will keep a net magnetization, while superparamagnetic NPs will display no net magnetization since quick setback of the magnetic moment. (b) Relationship between NP size and the magnetic domain structures. Ds and Dc are the “superparamagnetism” and “critical” size thresholds [33].

Table 1. Advantages and disadvantages of MCNT production method.

Method	Advantages	Disadvantages
Filling process	Operations low cost, raw materials availability,procedure easement	Hardship of quality control, MCNT’s central hollow blockage, weak reproducibility
Sol–gel process	Relative low temperature, low cost	Possibility of product contamination
CVD	Ultimate control on MCNT structure	Complex equipment, high cost, high energy consummation
Self-assembly	Full control over MCNT properties	Heterogeneity of produced MCNTs
Pyrolysis process	Mass production	Limited control over MCNTs, production of carbon black, certain need to inert atmosphere
Template-based synthesis	High quality of MCNTs	High-quality template, template elimination

Figure 3. TEM images of MCNTs prepared by filling process. (a) MCNTs filled with ferrofluid in magnetic field. (b) High-resolution TEM image of a portion of the nanotube, filled with MNPs [34].

Figure 4. (a) Typical magnetization curve of a MCNT prepared by filling process [34]. (b) XRD pattern of CNTs/Fe₃O₄ hybrids obtained by self-assembly method (the inset shows the XRD pattern of treated CNTs) [67].

Figure 5. The curves of GEM concentrations at different times after administration of GEM, MMWNTs-GEM-Magnet MMWCNT-GEM, MACs-GEM-Magnet and MACs-GEM: (a) in the left popliteal lymph nodes and (b) in blood plasma [12].

Figure 6. In vivo lymph node targeting of the MNPs. (a) Effects of different treatment groups on metastatic lymph node growth inhibition in vivo. (b) A representative photograph of the mouse to which MMWCNTs-GEM was subcutaneously administered under the magnetic field. The primary tumour (white arrow), blackened metastatic popliteal lymph node (arrowhead), and magnet (black arrow) were shown. (c) Photographs of popliteal lymph nodes isolated on day 15 from mice treated with saline, MACs/MMWCNTs, GEM, and various combinations with or without applying implanted in vivo magnets were shown. Scale bars are 5 mm [89].

Figure 7. (a) Schematic illustration of FITC-MCNT uptake into THP-1 cells by external rotating and static magnetic fields and (b) % FITC-positive cells exposed to FITC-MCNT or MCNT only after 1, 3, and 6 h exposures [90].

Figure 8. Drug release of DOX from FITC-MMWCNTs at pH 7.4 and 5.3 (37 °C) [92].

Figure 9. (a) BLI images of tumour-bearing mice at 0, 3, 7, 10, and 14 d after injection of either SWCNT⋅ + CD105 (upper row) or DOX-loaded SWCNT⋅ + CD105 (lower row) showing the progression of tumour and eventual metastasis following inoculation of 4T1-Luc2 breast cancer cells in the left inguinal mammary fat pad. (b) Quantitative assessments of radiance efficiency following intravenous injection of either free DOX or CD105- conjugated SWCNT samples with or without either iron tagging (⋅) or drug loading (DOX) accomplished to evaluate treatment-induced responses. Black arrows highlight the time of DOX or SWCNT injections [93].

Figure 10. Rotational motion of sheep red blood cells. Magnetic nanotubes are attached to the cells. The images correspond to 0, 0.2, 0.4, 0.6, 0.8, and 1.0th cycle of the rotational magnetic field. The scale bars are 5 µm. (a) A sheep red blood cell. Magnetic nanotubes indicated by an arrow are attached to the cell. (b) Two sheep red blood cells bridged with magnetic nanotubes [15].

Figure 11. In vivo T2-weighted MRI images of (a) liver and (b) kidneys/spleen before and after administration of MMWCNT (post 15, 90, 165, 225, and 300 min), (c) time-dependence of the relative signal intensity in liver and spleen after the administration of MMWCNT [121].

Figure 12. MWCNT, SPIO@Lac-Gly and CNT-PDDA-SPIO@Lac-Gly relaxivity results [124].

Figure 13. MRI images of mouse liver before and after injection of CNT-PDDA-SPIO@Lac-Gly (10 mg/kg) (white arrows indicate tumours) compared to internal standard (water, top right) [124].

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