Recently, the chemo-photothermal synergistic therapy has become a potential method for cancer treatment. Herein, we developed a multifunctional nanomaterial for chemo-photothermal therapeutics based on silica and graphene core/shell structure (SiO2@GN) because of the ability of GN to convert light energy into heat. Serum protein was further modified onto the surface of GN (SiO2@GN-Serum) to improve the solubility and stability of GN-based nanoparticles in physiological conditions. The as-synthesized SiO2@GN-Serum nanoparticles (NPs) have been revealed to have high photothermal conversion efficiency and stability, as well as high storage and release capacity for anticancer drug doxorubicin (SiO2@GN-Serum-Dox). The therapeutic efficacy of SiO2@GN-Serum-Dox has been evaluated in vitro and in vivo for cervical cancer therapy. In vitro cytotoxicity tests demonstrate that SiO2@GN-Serum NPs have excellent biocompatibility. However, SiO2@GN-Serum-Dox NPs show higher cytotoxicity than SiO2@GN-Serum and free Dox under irradiation with NIR laser at 1.0 W/cm2 for 5 min owing to both SiO2@GN-Serum-mediated photothermal ablation and cytotoxicity of light-triggered Dox release. In mouse models, the tumor growth is significantly inhibited by chem-photothermal effect of SiO2@GN-Serum-Dox. Overall, compared with single chemotherapy or photothermal therapy, the combined treatment demonstrates better therapeutic efficacy. Our results suggest a promising GN-based core/shell nanostructure for biomedical applications.Keywords: cancer therapy; drug delivery; graphene; photothermal therapy; serum protein; silica; synergistic effect

A novel porous carbon nanosheet was successfully fabricated by a one-step annealing process with folic acid as the carbon source in the absence of any other reagents or templates. The product exhibited a large specific surface area and good porosity. Meanwhile, the carbon nanosheets as a metal-free catalyst showed a high electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline solution, including superior onset and reduction potentials as well as a nearly four-electron pathway.Keywords: carbon nanosheets; folic acid; four-electron pathway; oxygen reduction reaction; rotating ring-disk electrode;

Water-solubilized quantum dots have led to a promising application in cellular labeling and biological imaging. The physicochemical properties of water-solubilized quantum dots, particularly in a physiological environment, are strongly dependent on their size. In this paper, we systematically studied the stability of mercaptosuccinic acid-coated CdTe quantum dots (MSA-QDs) of about 2.3 and 5.4 nm diameters in various buffers with different pH values and under laser irradiation by fluorescence spectroscopy. It was found that larger MSA-QDs showed better stability. Size-dependent uptake of MSA-QDs by living HeLa cells was further investigated by confocal microscopy. In phosphate buffer solution, the larger MSA-QDs entered the cells mainly by endocytosis, and part of the smaller ones entered the cells by passive penetration. In cell culture medium, their uptake pathways could be changed due to the changes of their surface properties. The cytotoxicity of smaller and larger MSA-QDs was significantly decreased due to the adsorption of some biological components in the cell culture medium on the nanoparticles surface.Keywords: CdTe quantum dots; confocal microscopy; fluorescence spectroscopy; size-dependent stability; small diameter; uptake mechanism;

The high levels of H2O2 are closely associated with cancer and progressive neurodegenerative diseases, such as Parkinson’s disease. In this study, we developed a novel CuS nanoparticle-decorated reduced graphene oxide-based electrochemical biosensor for the reliable detection of H2O2. The new electrocatalyst, CuS/RGO composites was successfully prepared by heating the mixture of CuCl2 and Na2S aqueous solutions in the presence of PVP-protected graphene oxide at 180 °C. A potential application of CuS/RGO composite-modified electrode as a biosensor to monitor H2O2 has been investigated. The steady-state current response increases linearly with H2O2 concentration from 5 to 1500 μM with a fast response time of less than 2 s. The detection limit (3σ) for determination of H2O2 has been estimated to be 0.27 μM, which was lower than certain enzymes and noble metal nanomaterial-based biosensors. In addition, the study of storage time on the amperometric response of the sensor indicates super stability. Due to these remarkable analytical advantages, the as-made sensor was applied to determine the H2O2 levels in human serum and urine samples and H2O2 released from human cervical cancer cells with satisfactory results. These results demonstrate that this new nanocomposite with the high surface area and electrocatalytic activity is a promising candidate for use as an enhanced electrochemical sensing platform in the design of nonenzymatic biosensors.

•Ultrafine Ag nanoparticles were grown on carbon surfaces with no toxic reagent.•The reduction temperature of silver nanoparticles was at room temperature.•The sample showed a superior oxygen reduction reaction activity.•A feasible synthesis mechanism has been proposed.We have demonstrated a facile and green strategy to synthesize ultrafine silver nanoparticles monodispersed on N-doped three-dimensional carbon nanocloud surfaces without any toxic reagent. Folic acid was employed as the carbon precursor for forming N-doped carbon nanoflakes by a hydrothermal method. The as-prepared products can serve as both reducing agent and substrate, on which a high density of ultrafine Ag nanocrystals is stably grown in a homogeneously dispersive state spontaneously at room temperature. A feasible synthesis mechanism has been proposed by characterization of carbon precursor, nanomaterials composited without and with silver nanoparticles. It was found that the ethylenic and oxygenated groups led to the reduction process. The nanohybrids showed an enhanced electrocatalytic activity toward oxygen reduction reaction (ORR) in alkaline solution via a four-electron pathway. The catalyst also exhibited strong duration of methanol and good stability compared to commercial Pt/C catalysts.

Au core/Ag shell nanorods (Au@Ag NRs) were synthesized through the seed-mediated growth procedure using Au nanorods (Au NRs) as templates and characterized by UV–vis and TEM methods. The as-prepared Au@Ag NRs were used as a new electrode material for construction of sensor by surface casting of Au@Ag NRs aqueous solution on a glassy carbon electrode (GCE). The fabricated sensor exhibits excellent catalytic performance toward H2O2 reduction with a fast amperometric response time of less than 2 s, a wide linear response ranging from 0.02 to 7.02 mM (R = 0.99), and a lower detection limit of 0.67 μM estimated on a signal-to-noise ratio of 3. A glucose biosensor was further fabricated by immobilization of glucose oxidase (GOD) onto the core/shell Au@Ag NRs-modified GCE. The resultant biosensor exhibits high sensitivity, selectivity and stability for glucose detection in phosphate buffer solution. Even in human blood serum, the biosensor also exhibits good performance for glucose detection with an enhanced sensitivity of 33.67 μA mM−1 cm−2.

We report a novel hydrogen peroxide (H2O2) and hydrazine sensor based on low-cost poly(vinylpyrrolidone)-protected silver nanocubes (PVP–AgNCs). The monodisperse silver nanocubes were prepared by adding a trace amount of sodium sulfide in the conventional polyol synthesis for fast reduction of silver nitrate under protection of argon. The sensor was fabricated by simple casting of PVP–AgNCs aqueous solution on a glassy carbon electrode and the performance was evaluated by cyclic voltammetry and amperometric techniques. It was found that the resulting sensor exhibited extremely good performance toward H2O2 detection with wide linear response ranging from 0.05 to 70 mM (R=0.996) at −0.3 V and low detection limit of 0.18 μM estimated at a signal-to-noise ratio of 3. In addition, the fabricated sensor also exhibited high sensitivity toward the detection of hydrazine with a low detection limit of 1.1 μM, wide linear range from 0.005 to 0.46 mM (R=0.999) at 0.4 V and rapid amperometric response time of less than 2 s. For both analytes, the sensor exhibited good reproducibility, selectivity and stability. The excellent performance of the sensor might be attributed to the enhanced electrochemical sensing property of well-defined PVP–AgNCs with rich {100} facets.Highlights► Silver nanocubes with rich {100} facets were used as a new electrode material. ► Silver nanocube-based detection toward H2O2 is better than those of most Pt nanomaterials. ► Silver nanocubes also showed excellent catalytic activity toward the oxidation of hydrazine.

It is well-known that nanomaterials are capable of entering living cells, often by utilizing the cells’ endocytic mechanisms. Passive penetration of the lipid bilayer may, however, occur as an alternative process. Here we have focused on the passive transport of small nanoparticles across the plasma membranes of red blood cells, which are incapable of endocytosis. By using fluorescence microscopy, we have observed that zwitterionic quantum dots penetrate through the cell membranes so that they can be found inside the cells. The penetration-induced structural changes of the lipid bilayer were explored by surface-enhanced infrared absorption spectroscopy and electrochemistry studies of model membranes prepared on solid supports with lipid compositions identical to those of red blood cell membranes. A detailed analysis of the infrared spectra revealed a markedly enhanced flexibility of the lipid bilayers in the presence of nanoparticles. The electrochemistry data showed that the overall membrane structure remained intact; however, no persistent holes were formed in the bilayers.Keywords: confocal microscopy; FTIR spectroelectrochemistry; membrane penetration mechanism; pore formation; zwitterionic quantum dots

Direct electron transfer of horse heart cytochrome c (HHCC) adsorbed on a bare metal electrode has been shown to be hard to achieve. The reason for that has been discussed in terms of conformational changes, protein unfolding, and even denaturation of the protein. We explored the adsorption of HHCC on a bare Au electrode by surface-enhanced infrared absorption spectroscopy on the molecular level. Our results revealed that the native secondary structure of adsorbed HHCC was kept even on the bare Au surface. The hampered electron transfer was mainly caused by its adsorption orientation. The adsorption of HHCC on the bare gold surface led the tyrosine 97 residue to be close to the surface. In this orientation, most of the α-helices of adsorbed HHCC run parallel to the bare Au surface with a flatter orientation of the heme relative to its orientation on an 11-mercaptoundecanoic acid-modified Au surface.