Carbon nanotubes have been shown to have the ability to transport therapeutic and detective reagents into cells. However, the rapid advances in new carbon nanotube-based materials and technologies have raised concerns about their safety. Such concerns require a fundamental understanding of the toxicological properties of carbon nanotubes. In particular, the use of carbon nanotubes as drug or probe delivery platforms may depend on the prevention of stimulatory side-effects to the immune system. In this study, we investigated the immunological properties of oxidized water dispersible multi-walled carbon nanotubes (MWCNTs) in healthy BALB/c mice. We injected the MWCNTs subcutaneously, and the immune responses of the mice were monitored over time. We show that the MWCNTs induce complement activation and the production of pro-inflammatory cytokines early after injection of the mice, and that the levels of complement and cytokines return to normal levels over time. With the exception of the lymph nodes, there was no obvious accumulation of MWCNTs observed in the liver, spleen, kidney, or heart. In addition, we did not observe injury in the organs or lymph nodes. Our results indicate that local, subcutaneous administration of MWCNTs induces obvious short-term immunological reactions, which can be eliminated over time.

Biomedical application potentials of carbon nanotubes-based materials have been investigated intensively in recent years; however, characterization and metrology are still facing great technical challenges when the materials are intended to be used as carriers for therapeutics in aqueous solutions. Systematic characterization on the dispersing carbon nanotubes is urgently required and therefore of significance. In this paper multiwalled carbon nanotubes (MWCNTs) with different average lengths or with different oxidation degrees were dispersed in water and characterized systematically by applying UV spectroscopy, SEM, DLS, TGA, XPS, and FTIR. In particular, the characteristic absorption of the carbon nanotubes was analyzed using resolution-fitting technique to establish relations of wavelength and absorption intensity to the size distribution and surface chemistry. Results indicated that the absorption spectra of MWCNTs could reflect the variation of surface chemistry and length distribution of carbon nanotubes dispersed in water by combining with the other measurements. A vascular endothelium cell line was taken as a model to figure out association between physicochemical features and cytotoxicity of the carbon nanotubes. It was showed that the multiwalled carbon nanotubes with different oxidation degrees and similar length distribution exhibited different interaction files to the cells proliferation in a manner of time dependence and concentration dependence.

The immunological responses induced by oxidized water-soluble multi-walled carbon nanotubes on a hepatocarcinoma tumor-bearing mice model via a local administration of subcutaneous injection were investigated. Experimental results show that the subcutaneously injected carbon nanotubes induced significant activation of the complement system, promoted inflammatory cytokines' production and stimulated macrophages' phagocytosis and activation. All of these responses increased the general activity of the host immune system and inhibited the progression of tumor growth.

Metallic nanozymes attracted broad interest because of their efficient catalytic activities and wide applications in biological detection and therapeutics. In this study, PtPdCu trimetallic nanoalloys (TNAs) are prepared by chemical coreduction of Pt2+, Pd2+, and Cu2+ in an aqueous solution. The formation of PtPdCu TNAs is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive system (EDS), and X-ray photoelectron spectroscopy (XPS). Compared to PtPd bimetallic nanoalloys (BNAs) and commercial Pt/C, PtPdCu TNAs have enhanced enzymelike activities, including peroxidase, oxidase (ferroxidase), and catalase, as well as increased DPPH free radical scavenging ability. Due to the synergistic effect between heteroatoms, the incorporation of Cu into Pt and Pd to form trimetallic structure not only exposes more active surfaces but also causes a change in the electronic structure, which is beneficial to improve the enzymelike catalytic activity. Using the ferroxidase-like and peroxidase-like activity of PtPdCu TNAs, we demonstrate the applications of PtPdCu TNAs in selective detection of Fe2+ in oral supplements and evaluation of the antioxidant capacity of natural antioxidants and tea extracts. Three natural antioxidants tannic acid (TA), gallic acid (GA), and ascorbic acid (AA) are found to show different inhibitory behaviors on peroxidase-like activity of PtPdCu and share the order of antioxidant capability TA > GA > AA.

In order to track carbon nanotubes (CNTs) in vitro or in vivo, many technologies have already been applied. However, the potential toxic effects of technologies such as radio and quantum dot labeling are the major problems. Therefore, the need to search for a new kind of biocompatible material to label CNTs has become urgent. In this work, one kind of porphyrin derivative with a single amino group was synthesized and covalently conjugated to oxidized water-soluble multi-walled carbon nanotubes (MWCNTs). The physiochemical properties of the oxidized MWCNTs and the fluorescent characteristics of their conjugate were carefully investigated. The experimental results indicated that the carboxyl group was introduced to the oxidized MWCNTs, allowing reaction with the amino group of the porphyrin, while the tube-like structure was well retained. The conjugate of the amino porphyrin and the MWCNTs exhibited strong red fluorescence emissions at 670 nm and 730 nm when excited with the optimal excitation wavelength of 420 nm. An aqueous solution containing the conjugate was injected subcutaneously into mice and was then imaged in vivo and ex vivo. Results showed that the conjugate was mainly engulfed by macrophages under the skin, and most of the conjugates accumulated in subcutaneous connective mucosa and a small amount in the liver, over a long period.