Adhesion of Bacteria to a Graphene Oxide Film.

Graphene oxide (GO)-based materials have recently received increasing attention in antibacterial fields due to their unique two-dimensional structure, high specific surface area, water solubility, easy functionality, low cost, etc. In this work, we investigated the interaction of GO films with several bacteria, including Escherichia coli, Staphylococcus aureus, Bacillus, and Shewanella-MR 1. Surprisingly, it was found that GO films had no influence on the growth of bacteria; bacteria could selectively attach on the GO films, and the adhesion efficiency was dependent on the genus of bacteria and the quality of GO films, as confirmed by quartz crystal microbalance (QCM) measurement. X-ray photoelectron spectroscopy, Ramam spectra analyses, and current-voltage curves further indicated that the bacteria could reduce GO to reductive GO (rGO) or graphite. Through constant current measurements, a possible mechanism that involved electron transfer from bacteria to the GO film was proposed for the adherence of bacteria to GO films and reduction of GO films by bacteria. The study suggested that GO films could act as biocompatible sites for adhesion of bacteria on their surfaces, providing a paradigm for exploring the interaction of GO-related materials with bacteria.

Overactivation of the Reward System and Deficient Inhibition in Exercise Addiction.

PURPOSE: Behavior studies have found that exercise addiction is associated with high impulsivity. In other addictions, neural mechanisms of impulsivity reflect abnormalities in the reward and inhibition systems. In this study, we determined whether abnormalities existed in the reward and inhibition systems of exercise addicts. METHODS: Three groups of male participants (15 exercise addicts, 18 regular exercisers, and 16 exercise avoiders) completed the Mini International Personality Item Pool (Mini-IPIP), the classic go/no-go task, and the exercise-related go/no-go task. Event-related potentials (ERP) were recorded during the go/no-go tasks, and correctly performed trials were analyzed. RESULTS: Exercise addicts scored lower for extraversion and higher for neuroticism, reflecting a poor capacity for emotional regulation and impulse control, and had larger N2 and P3d amplitudes during the exercise-related go/no-go task. Exercise addicts and exercise avoiders demonstrated impaired accuracy in the exercise-related go/no-go task and had larger N2 amplitudes compared with regular exercisers during the letter-digit go/no-go task. Exercise addicts and regular exercisers showed larger Go-N1 and Go-P2 amplitudes compared with exercise avoiders during the exercise-related go/no-go task. Exercisers (exercise addicts and regular exercisers) demonstrated higher activation in response to exercise-related stimuli as reflected by larger N1 and P2, and addicts (exercise addicts) demonstrated poorer inhibition as reflected by larger N2 and P3d amplitudes. Go-N1 and Go-P2 were significantly correlated with no-go accuracy in exercise-related task. CONCLUSIONS: Exercise addicts scored higher for the neuroticism personality trait and exhibited overactivation of the reward system and underactivation of the inhibition system. Overactivation of the reward system may be related to long-term exposure to exercise. Underactivation of the inhibition system may be a crucial factor in exercise addiction.

Pd nanosheets with their surface coordinated by radioactive iodide as a high-performance theranostic nanoagent for orthotopic hepatocellular carcinoma imaging and cancer therapy.

Radiolabeled nanoparticles (NPs), taking advantage of nanotechnology and nuclear medicine, have shown attractive potential for cancer diagnosis and therapy. However, the high background signal in the liver and long-term toxic effects of radioisotopes caused by the nonselective accumulation of radiolabeled nanoparticles in organs have become the major challenges. Here, we report a pH-sensitive multifunctional theranostic platform with radiolabeled Pd nanosheets through a simple mixture of ultra-small Pd nanosheets and radioisotopes utilizing the strong adsorption of 131I and 125I on their surfaces (denoted as 131I-Pd-PEG or 125I-Pd-PEG). Systematic studies reveal that the labeling efficiency is higher than 98% and the adsorption of radioiodine is more stable in an acidic environment. In vivo studies further validate the pH-dependent behavior of this platform and the enhanced retention of radioisotopes in tumors due to the acidic microenvironment. Single photon emission computed tomography (SPECT) images with zero background were successfully achieved in a subcutaneous 4T1 tumor model, an orthotopic LM3 tumor model, and even in a Mst1/2 double-knockout hepatoma model. Moreover, the application of radiolabeled Pd nanosheets for photoacoustic (PA) imaging, and combined photothermal and radiotherapy was also explored. Therefore, this study provides a simple and efficient strategy to solve the critical high background issue of radiolabeled nanoparticles and shows enormous potential for clinical applications.

A Pd corolla-human serum albumin-indocyanine green nanocomposite for photothermal/photodynamic combination therapy of cancer.

In this work, a novel nanoplatform based on Pd corolla-human serum albumin-indocyanine green (PdCs-HSA-ICG) was developed for cancer photothermal/photodynamic combination therapy. Pd corollas (denoted as PdCs) with good near-infrared photothermal conversion efficiency (η≈ 37%) were first prepared and modified with human serum albumin (HSA) and indocyanine green (ICG) to get the PdCs-HSA-ICG nanocomposite. The prepared PdCs-HSA-ICG not only improves the colloid and thermal stability of ICG, but also shows a higher temperature increase than that of PdCs and free ICG as well as a comparable singlet oxygen (1O2) generation capability to that of free ICG. Upon single 808 nm laser irradiation, the photothermal (PTT)/photodynamic (PDT) combined therapeutic efficacy of PdCs-HSA-ICG at both cellular and animal levels was superior to PdCs-HSA (PTT) or free ICG (PTT and PDT), respectively. Thus, the designed PdCs-HSA-ICG nanocomposite holds great potential as a new class of photosensitive agent for cancer phototherapy.

The biodistribution, excretion and potential toxicity of different-sized Pd nanosheets in mice following oral and intraperitoneal administration.

Two-dimensional (2D) Pd-based nanomaterials with strong near-infrared absorption have recently shown great application prospects in cancer diagnosis and therapy. Most previous studies mainly focused on understanding the in vivo behaviors and treatment effects of these Pd-based nanomaterials after intravenous injection into mice. However, it remains unclear whether other administration routes will affect the in vivo biodistribution, excretion and potential toxicity of Pd-based nanomaterials. In this study, for the first time we systematically explored the in vivo behaviors of different-sized Pd nanosheets (NSs) (approximately 5 nm, 30 nm and 80 nm) following oral feeding and intraperitoneal injection. It was found that Pd NSs with oral administration had a rather low accumulation that decreased with time in all examined organs, and became almost undetectable in these organs at 24 h post-injection. In comparison, the intraperitoneally injected Pd NSs exhibited obvious time-dependent and size-dependent accumulations in the reticuloendothelial (RES) system including the liver and spleen within 24 h post-injection, and then the accumulation amounts decreased with the lapse of time. Moreover in tumor tissue, smaller-sized Pd NSs (5 nm) had a higher uptake than larger-sized Pd NSs (30 nm and 80 nm). Excretion studies uncovered that more than 70% ID of Pd NSs could be rapidly excreted from the body through urine and feces within two days after oral administration, whereas Pd NSs with intraperitoneal injection could be gradually cleared, mainly via urine within 8 days. Further histological examination of organ sections and blood biochemical analysis evidenced that these different-sized Pd NSs do not cause obvious toxicity in the treated mice at the tested period with the given dose. These results not only indicate that the biodistribution and excretion capabilities of Pd NSs are closely related to their administration routes, but also imply that the intraperitoneally injected Pd NSs have greater potential for in vivo biomedical studies compared to oral feeding, because of their relatively higher tissue absorption and gradual excretion from the body. This study will provide valuable information for the clinical translation of 2D Pd-based nanomaterials.

Two-dimensional Pd-based nanomaterials for bioapplications.

Noble metal nanomaterials have been extensively explored in cancer diagnostic and therapeutic applications owing to their unique physical and chemical properties, such as facile synthesis, straightforward surface functionalization, strong photothermal effect, and excellent biocompatibility. Herein, we summarize the recent development of two-dimensional (2D) Pd-based nanomaterials and their applications in cancer diagnosis and therapy. Different synthetic strategies for Pd nanosheets and the related nanostructures, including Pd@Au, Pd@Ag nanoplates and mesocrystalline Pd nanocorolla, are first discussed. Together with their unique properties, the potential bioapplications of these 2D Pd nanomaterials are then demonstrated. With strong absorption in near-infrared (NIR) region, these nanomaterials have great potentials in cancer photothermal therapy (PTT). They also readily act as contrast agents in photoacoustic (PA) imaging or X-ray computed tomography (CT) to achieve image-guided cancer therapy. Moreover, significant efforts have been devoted to studying the combination of PTT and other treatment modalities (e.g., chemotherapy or photodynamic therapy) based on Pd nanomaterials. The remarkable synergistic or collaborative effects to achieve better therapeutic efficacy are discussed as well. Additionally, the biosafety of 2D Pd-based nanomaterials in vitro and in vivo was evaluated. Finally, challenges for the applications of Pd-based nanomaterials in cancer diagnosis and therapy, and future research prospects are highlighted.

Platinum(IV) prodrug conjugated Pd@Au nanoplates for chemotherapy and photothermal therapy.

Owing to the excellent near infrared (NIR) light absorption and efficient passive targeting toward tumor tissue, two-dimensional (2D) core-shell PEGylated Pd@Au nanoplates have great potential in both photothermal therapy and drug delivery systems. In this work, we successfully conjugate Pd@Au nanoplates with a platinum(IV) prodrug c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2] to obtain a nanocomposite (Pd@Au-PEG-Pt) for combined photothermal-chemotherapy. The prepared Pd@Au-PEG-Pt nanocomposite showed excellent stability in physiological solutions and efficient Pt(IV) prodrug loading. Once injected into biological tissue, the Pt(IV) prodrug was easily reduced by physiological reductants (e.g. ascorbic acid or glutathione) into its cytotoxic and hydrophilic Pt(II) form and released from the original nanocomposite, and the NIR laser irradiation could accelerate the release of Pt(II) species. More importantly, Pd@Au-PEG-Pt has high tumor accumulation (29%ID per g), which makes excellent therapeutic efficiency at relatively low power density possible. The in vivo results suggested that, compared with single therapy the combined thermo-chemotherapy treatment with Pd@Au-PEG-Pt resulted in complete destruction of the tumor tissue without recurrence, while chemotherapy using Pd@Au-PEG-Pt without irradiation or photothermal treatment using Pd@Au-PEG alone did not. Our work highlights the prospects of a feasible drug delivery strategy of the Pt prodrug by using 2D Pd@Au nanoplates as drug delivery carriers for multimode cancer treatment.

An investigation of the mimetic enzyme activity of two-dimensional Pd-based nanostructures.

In this work, we investigated the mimetic enzyme activity of two-dimensional (2D) Pd-based nanostructures (e.g. Pd nanosheets, Pd@Au and Pd@Pt nanoplates) and found that they possess intrinsic peroxidase-, oxidase- and catalase-like activities. These nanostructures were able to activate hydrogen peroxide or dissolved oxygen for catalyzing the oxidation of organic substrates, and decompose hydrogen peroxide to generate oxygen. More systematic investigations revealed that the peroxidase-like activities of these Pd-based nanomaterials were highly structure- and composition-dependent. Among them, Pd@Pt nanoplates displayed the highest peroxidase-like activity. Based on these findings, Pd-based nanostructures were applied for the colorimetric detection of H2O2 and glucose, and also the electro-catalytic reduction of H2O2. This work offers a promising prospect for the application of 2D noble metal nanostructures in biocatalysis.

Copper sulfide nanoparticles with phospholipid-PEG coating for in vivo near-infrared photothermal cancer therapy.

In this work, small sizes of hydrophobic copper sulfide nanoparticles (CuS NPs, ∼3.8 nm in diameter) have been successfully prepared from the reaction of copper chloride with sodium diethyldithiocarbamate (SDEDTC) inside a heated oleylamine solution. These CuS NPs displayed strong absorption in the 700-1100 nm near-infrared (NIR) region. By coating CuS NPs with DSPE-PEG2000 on the surface, the as-synthesized CuS@DSPE-PEG NPs exhibited good water solubility, significant stability and biocompatibility, as well as excellent photothermal conversion effects upon exposure to an 808 nm laser. After intravenous administration to mice, the CuS@DSPE-PEG NPs were found to passively target to the tumor site, and tumor tissues could be ablated efficiency under laser irradiation. In addition, CuS@DSPE-PEG NPs do not show significant toxicity by histological and blood chemistry analysis, and can be effectively excreted via metabolism. Our results indicated that CuS@DSPE-PEG NPs can act as an ideal photothermal agent for cancer photothermal therapy.