properties and tubular shape. Silviana Fiorito et al. [185] reported the activation of microglia using MWCNTs with highly electro-conductive properties, polarizing the microglia cells into M1 state (pro-infammatory) after 24 h of cell exposure and M2 state (anti-infammatory) after 48 h of exposition. They detected this phenomenon in vitro using primary rat microglial cells, suggesting that the electro-stimulation of these CNTs could modulate microglial responses.

The use of carbon nanotubes as sca olds for neurons has also been well studied, as they are good platforms for protecting neuron damage in ischemia [186]. Jung Lee et al. pretreated rats with amine-modified SWCNTs before an ischemic surgery, finding less tissue damage and better motor function in the treated animals after the insult. More recently, CNTs were reported as good sca olds for di erent types of neurons, like retinal neurons or sciatic nerve [187]. In this work, the authors studied retinal cell growth in vitro using MWCNTs as frame to these cells. They followed the procedure with rat and human retinal cells, finding an e cient growth for both of them. Salehi et al. [188] developed a conduit produced from polylactic acid, MWCNTs, and gelatin nanofibrils coated with the recombinant human erythropoie- tin-loaded chitosan nanoparticles. They loaded this conduit with Schwann cells and implanted it in rats with sciatic nerve defect, finding improved recovery rate. Finally, carbon nanotubes have also shown some neuroprotector properties. Xue et al. [189] reported that C57BL/6J mice pretreated with aggregated SWCNTs significantly inhibited self-administration of methamphetamine. The electrochemical assays indicated that nanotubes made the oxidation of extracellular dopamine in the striatum easier, suggesting the potential use of aggregated SWCNTs for the treatment of methamphetamine addiction.

4.3 Theranostic Applications

Theranostic compounds are nanoparticles integrating both diagnostic and therapeutic capabilities into a platform. CNTs have been intensively studied for theranostic applications [163], as they can be easily coupled with di erent molecules/structures achieving synergetic analytic and curative e ects [190]. Basically, this approach relies on the CNT functionalization with structures carrying abilities for detecting and treating the disease, achieving at the same time cell targeting and delivering of the drug under microenvironmental stimuli. Some examples have already been presented in earlier. Mashal et al. [191] constructed tissue-mimicking materials and found that SWCNTs could enhance dielectric contrast between tumoral and healthy tissue for microwave detection and hyperthermia treatment in breast cancer. More recently, Al Faraj et al. [192] described the preparation and the in vitro and in vivo characterization of drug-conjugated SWCNTs as nanocarriers for breast cancer therapy. The authors aimed to target a stem cell subpopulation with a combination of therapeutic drugs (paclitaxel and salinomycin) selectively delivered via biocompatible CD44 antibody-conjugated SWCNTs with a pH-responsive release. The therapy was non-invasively monitored in tumor-bearing mice with MRI and bioluminescence imaging (BLI), and the results clearly showed enhanced therapeutic e ect of

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