In this study we compare the biodegradation of both single-walled (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) using two different oxidative conditions. In particular, we demonstrate that oxidized multi-walled carbon nanotubes are highly degraded, although not to completeness when treated with horseradish peroxidase (HRP) in the presence of hydrogen peroxide.

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Ultrasonography is a fundamental diagnostic imaging tool in everyday clinical practice. Here, we are unique in describing the use of functionalized multiwalled carbon nanotubes (MWCNTs) as hyperechogenic material, suggesting their potential application as ultrasound contrast agents. Initially, we carried out a thorough investigation to assess the echogenic property of the nanotubes in vitro. We demonstrated their long-lasting ultrasound contrast properties. We also showed that ultrasound signal of functionalized MWCNTs is higher than graphene oxide, pristine MWCNTs, and functionalized single-walled CNTs. Qualitatively, the ultrasound signal of CNTs was equal to that of sulfur hexafluoride (SonoVue), a commercially available contrast agent. Then, we found that MWCNTs were highly echogenic in liver and heart through ex vivo experiments using pig as an animal model. In contrast to the majority of ultrasound contrast agents, we observed in a phantom bladder that the tubes can be visualized within a wide variety of frequencies (i.e., 5.5–10 MHz) and 12.5 MHz using tissue harmonic imaging modality. Finally, we demonstrated in vivo in the pig bladder that MWCNTs can be observed at low frequencies, which are appropriate for abdominal organs. Importantly, we did not report any toxicity of CNTs after 7 d from the injection by animal autopsy, organ histology and immunostaining, blood count, and chemical profile. Our results reveal the enormous potential of CNTs as ultrasound contrast agents, giving support for their future applications as theranostic nanoparticles, combining diagnostic and therapeutic modalities.

In view of the broad potential biomedical applications of carbon nanotubes (CNTs) different studies were performed to assess their effect on the immune system. However, the work performed to date was able to give a restricted view looking only at some activation markers and cytokine expression. The immune system is rarely limited to few molecule interactions being instead always a balance of switching several genes on and off. Whole genome expression (microarray) is a technology able to give the full picture on genome expression. Here we describe a microarray genome-wide study on Jurkat cells, a T lymphocyte cell line, and THP1, a monocytic cell line, representative of both types of immune response, the adaptive and innate, respectively. Since any structure or molecule modification may lead to very different immune reactions, we treated the two cell lines with four types of functionalized multi-walled CNTs that differ in terms of functionalization and diameter. After having assessed the internalization and the lack of toxicity of CNTs in both cell types, we used the Affymetrix technology to analyze the expression of about 32,000 transcripts. Three of the tested nanotubes (i.e., ox-MWCNT-1, ox-MWCNT-NH3(+)-1, and ox-MWCNT-NH3(+)-2) activated immune-related pathways in monocytes but not in T cells. In view of these charateristics they were named as monocyte activating CNTs (MA-CNTs). Molecular pathways upregulated by MA-CNTs included IL6, CD40, dendritic cell maturation, tumor necrosis factor-(TNF)-α/TNFR1-2, NFKB signaling and T helper 1 chemokine pathways (CXCR3 and CCR5 ligand pathways). These pathways are commonly activated during acute inflammatory processes as those associated with immune-mediated tumor rejection and pathogen clearance. One of them (i.e., ox-MWCNT-2) downregulated genes associated with ribosomal proteins in both monocytes and T cells. We validated our findings at gene expression level by performing real-time PCR assessing the most highly modulated genes in monocytes. To confirm the results at protein level, the secretion of IL1β, TNFα, IL6 and IL10 by THP1 and primary monocytes was assessed by ELISA, corroborating gene-expression data. Our results provide new insights into the whole gene expression modulation by different CNTs on immune cells. Considering the well known drug carrier ability of CNTs, our findings demonstrate that MA-CNTs here behave as cell specific immunostimulatory systems, giving very interesting future perspectives for their application also as immunotherapeutic agents and/or vaccine adjuvants.

Our results, on human cells ex vivo, confirmed previous studies demonstrating appropriately functionalized CNTs are nontoxic. The effects on cell functionality were significant for the monocytes and NK cells. These findings encourage the possible use of CNTs for biomedical applications either as carriers of therapeutic molecules or as immune modulator systems.

As nanoparticles can cross different cellular barriers and access different tissues, control of their uptake and cellular fate presents a functional approach that will be broadly applicable to nanoscale technologies in cell biology. Here we show that the trafficking of single-walled carbon nanotubes (SWCNTs) through various subcellular membranes of the plant cell is facilitated or inhibited by attaching a suitable functional tag and controlling medium components. This enables a unique control over the uptake and the subcellular distribution of SWCNTs and provides a key strategy to promote their cellular elimination to minimize toxicity. Our results also demonstrate that SWCNTs are involved in a carrier-mediated transport (CMT) inside cells; this is a phenomenon that scientists could use to obtain novel molecular insights into CMT, with the potential translation to advances in subcellular nanobiology.

Marine toxins appear to be increasing in many areas of the world. An emerging problem in the Mediterranean Sea is represented by palytoxin (PlTX), one of the most potent marine toxins, frequently detected in seafood. Due to the high potential for human toxicity of PlTX, there is a strong and urgent need for sensitive methods toward its detection and quantification. We have developed an ultrasensitive electrochemiluminescence-based sensor for the detection of PlTX, taking advantage of the specificity provided by anti-PlTX antibodies, the good conductive properties of carbon nanotubes, and the excellent sensitivity achieved by a luminescence-based transducer. The sensor was able to produce a concentration-dependent light signal, allowing PlTX quantification in mussels, with a limit of quantification (LOQ = 2.2 μg/kg of mussel meat) more than 2 orders of magnitude more sensitive than that of the commonly used detection techniques, such as LC-MS/MS.

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