Aptamer-functionalized silver nanoclusters (Ag NCs) have been attracting a lot of interest as label-free probes which have been successfully applied to both cell imaging and molecular detection. MUC1 aptamer is an ssDNA aptamer that specifically binds to MUC1 mucin which is a large transmembrane glycoprotein whose expression level increases at least 10-fold in primary and metastatic breast cancers. Using C4A4C3-linker-MUC1 as template, the Ag NCs were synthesized through one-pot process. The fluorescence intensity of Ag NCs was found to be closely related to the length and type (poly adenine or thymine) of the linker, the optimum linker being–AAAAA–. Using the C4A4C3-A5-MUC1 as the scaffold, the synthesized Ag NCs emitted fluorescence with high quantum yield (QY) of 66.5%. Based on the specific interaction between the MUC1 aptamer and MUC1 mucin, the C4A4C3-A5-MUC1-stabilized Ag NCs could recognize and differentiate the MCF-7 breast cancer cells from MDA-MB-231 breast cancer and A549 human lung cancer cells.

In this work, we demonstrate that ultrasmall, photostable and multifunctional carbon quantum dots (or carbon dots, CDs) passivated with polyamine-containing organosilane molecules can realize simultaneous cell imaging and anticancer drug delivery. The presence of abundant surface amine groups makes these CDs be able to covalently link with the anticancer drug, doxorubicin (DOX), with an extremely high drug loading capacity (62.8%), while the surface hydroxyl groups ensure the good water-dispersibility of the CDs–DOX. Besides the use as a drug carrier, the fluorescent CDs also enable the dynamic tracing of the drug release process. When the CDs–DOX complexes were internalized by the human breast cancer cells (MCF-7), DOX could gradually detach from the surface of CDs and enter into the cell nucleus, while the CDs themselves still resided in the cytoplasm. In addition, the in vivo experiments showed that the CDs–DOX complexes exhibited a better tumor inhibition performance than free DOX molecules, which may be ascribed to the prolonged drug accumulation in tumor tissues. Furthermore, the as-synthesized CDs also exhibited negligible cytotoxicity/systemic side effects, and could successfully illuminate mammalian, bacterial and fungal cells, making them good candidates as not only drug delivery vehicles but also universal cell imaging reagents. The present work may have implications for the fabrication of functional carbon-based nanomaterials and foster the development of carbon dots as novel nanotheranostics for various biomedical applications.

Gold- or carbon-based photothermal therapy (PTT) agents have shown encouraging therapeutic effects of PTT in the near-infrared region (NIR) in many preclinical animal experiments. It is expected that gold/carbon hybrid nanomaterial will possess combinational NIR light absorption and can achieve further improvement in photothermal conversion efficiency. In this work, we design and construct a novel PTT agent by coating a carbon nanosphere with patchy gold. To synthesize this composite particle with Janus structure, a new versatile approach based on a facile adsorption–reduction method was presented. Different from the conventional fabrication procedures, the formation of patchy gold in this approach is mainly a thermodynamics-driven spontaneous process. The results show that when compared with the conventional PTT agent gold nanorod the obtained nanocomposites not only have higher photothermal conversion efficiency but also perform more thermally stable. On the basis of these outstanding photothermal effects, the in vitro and in vivo photothermal performances in a MCF-7 cells (human breast adenocarcinoma cell line) and mice were investigated separately. Additionally, to further illustrate the advantage of this asymmetric structure, their potential was explored by selective surface functionalization, taking advantage of the affinity of both patchy gold and carbon domain to different functional molecules. These results suggest that this new hybrid nanomaterial can be used as an effective PTT agent for cancer treatment in the future.Keywords: carbon nanospheres; Janus structure; MCF-7 cell; patchy gold; photothermal therapy

•Peroxidase-like property of Pt@mSiO2 NPs has been demonstrated.•Pt@mSiO2 NPs have both high catalytic activity and good dispersion stability.•Pt@mSiO2 NPs could be used as a substitute of enzyme in immunoassay.•As low as 10 ng mL−1 hCG could be detected with a linear range from 5 to 200 ng mL−1.Nanomaterial-based artificial enzymes have received great attention in recent year due to their potential application in immunoassay techniques. However, such potential is usually limited by poor dispersion stability or low catalytic activity induced by the capping agent essentially required in the synthesis. In an attempt to address these challenges, here, we studied the novel Pt nanoparticles (NPs) based peroxidase-like mimic by encapsulating Pt NP in mesoporous silica (Pt@mSiO2 NPs). Compared with other nanomaterial-based artificial enzymes, the obtained Pt@mSiO2 NPs not only exhibit high peroxidase-like activity but also have good dispersion stability in buffer saline solution when grafted with spacer PEG. Results show that when the thickness of silica shell is about 9 nm the resulting Pt@mSiO2 NPs exhibit the catalytic activity similar to that of Pt NPs, which is approximately 26 times higher than that of Fe3O4 NPs (in terms of Kcat for H2O2). Due to the protection of silica shell, the subsequent surface modification with antibody has little effect on their catalytic activity. The analytical performance of this system in detecting hCG shows that after 5 min incubation the limit of detection can reach 10 ng mL−1 and dynamic linear working range is 5–200 ng mL−1. Our findings pave the way for design and development of novel artificial enzyme labeling.

A highly selective chemodosimeter based on 1,8-naphthalimide for Pd2+/4+ species via a Claisen rearrangement was developed, which not only discriminated Pd from competing Pt species, but also distinguished Pd in an oxidized state without altering its oxidation states from Pd0. Under optimized reaction conditions, the detection limit can reach 1.4 μM for Pd2+.

To overcome the problem of non-specific silver precipitation occurring in the traditional silver staining, this work presents a new strategy for signal amplification by labeling the biological molecule with Pd/GO nanoparticles (NPs), which further act as catalysts to reduce copper ions to metallic copper to enhance the signal (denoted as “Pd/GO label copper stain” later). Based on this strategy, the electrochemical detection of a single-base mutation associated with the breast cancer gene TOX3 is specially studied by employing differential pulse voltammetry (DPV). The analytical performance of this system shows that after 15 min of copper staining there is a linear relationship between the peak current resulting from the oxidative dissolution of the copper deposit and the logarithm of the target DNA concentration in the range of 10 μM to 1 pM. The limit of detection can reach 1 pM, which benefits from the high catalytic activity of Pd/GO NPs along with a low background level of “Pd/GO label copper stain”. Therefore, this process can be expected to be a good alternative to silver staining used in nanomaterial-based signal amplification strategies in future.

Artificial enzyme mimics have recently attracted considerable interest because they possess many advantages compared with natural enzymes, such as low cost of preparation and high stability. Herein, we present a novel fluorescent artificial enzyme-linked immunoassay strategy by utilizing Pd/C nanocatalyst as the enzyme mimic and bis-allyloxycarbonyl rhodamine 110 (BI-Rho 110) as the substrate, and the amplification procedure is based on the palladium-catalyzed Tsuji-Trost reaction. Pd/C nanocatalyst with the average size of 150 nm was prepared by the impregnation–reduction method, and high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses reveal that Pd clusters with an average size of about 1 nm are dispersed uniformly on each carbon nanosphere’s surface. Kinetic studies show that this reaction follows Michaelis–Menten kinetics and the fluorescence intensity is proportional to the concentration of Pd/C nanocatalyst under certain conditions. The turnover number of Pd/C nanocatalyst reaches up to 3.3 × 107 (h–1). The analytical performance of this system in detecting hCG shows that after a 24 h incubation the sensitivity limit can reach 0.1 ng/mL and the dynamic linear working range is 1–10 ng/mL. Our findings pave the way to use Pd-catalyzed reaction for design and development of novel analytical methods.

The use of nanomaterials in biomolecular labeling and their corresponding detection has been attracting much attention, recently. There are currently very few studies on palladium nanoparticles (Pd NPs) due to their lack of appropriate surface functionalities for conjugation with DNA. In this paper, we thus firstly present an approach to prepare carboxyl group-modified Pd NPs (with an average size of 6 nm) by the use of 11-mercaptoundecanoic acid (MUDA) as a stabilizer in the aqueous solution. The effect of the various reducing reaction conditions on the morphology of the Pd NPs was investigated. The particles were further characterized by TEM, UV–vis, FT-IR and XPS techniques. DNA was finally covalently conjugated to the surface of the Pd NPs through the activation of the carboxyl group, which was confirmed by agarose gel electrophoresis and fluorescence analysis. The resulting Pd NPs–DNA conjugates show high single base pair mismatch discrimination capabilities. This work therefore sets a good foundation for further applications of Pd NPs in bio-analytical research.

To overcome the problem of non-specific silver precipitation occurring in the traditional silver staining, this work presents a new strategy for signal amplification by labeling the biological molecule with Pd/GO nanoparticles (NPs), which further act as catalysts to reduce copper ions to metallic copper to enhance the signal (denoted as “Pd/GO label copper stain” later). Based on this strategy, the electrochemical detection of a single-base mutation associated with the breast cancer gene TOX3 is specially studied by employing differential pulse voltammetry (DPV). The analytical performance of this system shows that after 15 min of copper staining there is a linear relationship between the peak current resulting from the oxidative dissolution of the copper deposit and the logarithm of the target DNA concentration in the range of 10 μM to 1 pM. The limit of detection can reach 1 pM, which benefits from the high catalytic activity of Pd/GO NPs along with a low background level of “Pd/GO label copper stain”. Therefore, this process can be expected to be a good alternative to silver staining used in nanomaterial-based signal amplification strategies in future.