Regular time-dependent cross-phenomena induced by hormesis: A case study of binary antibacterial mixtures to Aliivibrio fischeri.

Time-dependent cross-phenomenon in which the cross between the actual concentration-response curve (CRC) for mixture crosses the CRCs for reference model varies with time has been frequently reported in previous studies, expressed as a heterogeneous pattern of joint toxic action. However, the variation tendency of time-dependent cross-phenomenon is rarely addressed. In this study, the joint toxic actions of binary antibacterial mixtures (i.e., two quorum sensing inhibitors, tetracycline hydrochloride, erythromycin, and chloramphenicol with sulfonamides) were judged using independent action (IA) model to find the variation tendency of time-dependent cross-phenomenon. The results show that the time-dependent cross-phenomena of the test binary antibacterial mixtures follow a unified variation tendency and the corresponding joint toxic actions change regularly with an increase of both concentration and time. Through investigating the relationship between the stimulatory and inhibitory modes of action for the single agents and the time-dependent cross-phenomena of binary mixtures, the regular time-dependent cross-phenomena is speculated to be derived from the hormetic effects of the components in the mixtures. This study offers an advance for the variation tendency and mechanistic explanation of time-dependent cross-phenomenon, which will provide a support for the future development in the exploration of time-dependent cross-phenomenon and environmental risk assessment of pollutant mixtures.

Chitosan-functionalized graphene oxide as a nanocarrier for drug and gene delivery.

The covalent functionalization of graphene oxide (GO) with chitosan (CS) is successfully accomplished via a facile amidation process. The CS-grafted GO (GO-CS) sheets consist of about 64 wt.% CS, which imparts them with a good aqueous solubility and biocompatibility. Additionally, the physicochemical properties of GO-CS are studied. As a novel nanocarrier, GO-CS is applied to load a water-insoluble anticancer drug, camptothecin (CPT), via π-π stacking and hydrophobic interactions. It is demonstrated that GO-CS possesses a superior loading capacity for CPT, and the GO-CS-CPT complexes show remarkably high cytotoxicity in HepG2 and HeLa cell lines compared to the pure drug. At the same time, GO-CS is also able to condense plasmid DNA into stable, nanosized complexes, and the resulting GO-CS/pDNA nanoparticles exhibit reasonable transfection efficiency in HeLa cells at certain nitrogen/phosphate ratios. Therefore, the GO-CS nanocarrier is able to load and deliver both anticancer drugs and genes.

Analgesic and anti-inflammatory effects and mechanism of action of borneol on photodynamic therapy of acne.

This study aims to explore the analgesic and anti-inflammatory effects of borneol, a traditional Chinese medicine, on photodynamic treatment of acne. Here, we found that borneol significantly decreased the auricular swelling rate and pain threshold of rats. We also showed that borneol noticeably reduced macrophage and lymphocyte infiltration. The number of Th cells was significantly higher in the control PDT group than in the PDT plus borneol treatment group (P < 0.05). The expression of IL-6, TNF-α, and IL-8 mRNA and proteins were noticeably lower in the treatment group in comparison to those of the PDT control group, while PDT plus borneol activated the p38-COX-2-PGE2 signaling pathway, increasing expression in the treatment group. Borneol has significant analgesic and anti-inflammatory effects on PDT of acne, and enhances the healing of acne by activating p38-COX-2-PGE2 signaling pathway.

Multiple-species hormetic phenomena induced by indole: A case study on the toxicity of indole to bacteria, algae and human cells.

Hormesis is a dose-response relationship phenomenon characterized by low-dose stimulation and high-dose inhibition. Although hormetic phenomena have been reported in broadly ranging biological areas, there is still no unified mechanism of hormesis. Investigating multiple-species hormesis of one compound and then exploring the possible mechanism may be an effective approach to clarify the reason for the occurrence of hormetic phenomena in a broad range of organisms. In this study, indole was selected as the test chemical due to the broad biological and hormetic effects of indole compounds. The results show that indole induces multiple-species hormetic phenomena in bacteria (Aliivibrio fischeri (A. fischeri), Escherichia coli and Bacillus subtilis), algae (Microcystis aeruginosa and Selenastrum capricornutum), and human cells (human skin fibroblasts and human cervical cancer cells). Through in-depth investigation of the time-dependent hormetic effects of indole, indole derivatives and indole's structural analogs on the bioluminescence of A. fischeri, indole ring has been identified as the potential key structure that causes indole to act on quorum sensing of A. fischeri to induce hormetic effects on the bioluminescence at lag, logarithmic, and stationary phases. Therefore, the occurrence of multiple-species hormetic phenomena is speculated to be derived from the action of indole on the cell-to-cell communication of organism cells. This paper can not only further confirm the generalizability of hormesis but also provide a reasonable explanation for hormesis, which will benefit the development of hormesis and the risk assessment of environmental pollutants.

Mechanistic explanation of time-dependent cross-phenomenon based on quorum sensing: A case study of the mixture of sulfonamide and quorum sensing inhibitor to bioluminescence of Aliivibrio fischeri.

Cross-phenomenon in which the concentration-response curve (CRC) for a mixture crosses the CRC for the reference model has been identified in many studies, expressed as a heterogeneous pattern of joint toxic action. However, a mechanistic explanation of the cross-phenomenon has thus far been extremely insufficient. In this study, a time-dependent cross-phenomenon was observed, in which the cross-concentration range between the CRC for the mixture of sulfamethoxypyridazine (SMP) and (Z-)-4-Bromo-5-(bromomethylene)-2(5H)-furanone (C30) to the bioluminescence of Aliivibrio fischeri (A. fischeri) and the CRC for independent action model with 95% confidence bands varied from low-concentration to higher-concentration regions in a timely manner expressed the joint toxic action of the mixture changing with an increase of both concentration and time. Through investigating the time-dependent hormetic effects of SMP and C30 (by measuring the expression of protein mRNA, simulating the bioluminescent reaction and analyzing the toxic action), the underlying mechanism was as follows: SMP and C30 acted on the quorum sensing (QS) system of A. fischeri, which induced low-concentration stimulatory effects and high-concentration inhibitory effects; in the low-concentration region, the stimulatory effects of SMP and C30 made the mixture produce a synergistic stimulation on the bioluminescence; thus, the joint toxic action exhibited antagonism. In the high-concentration region, the inhibitory effects of SMP and C30 in the mixture caused a double block in the loop circuit of the QS system; thus, the joint toxic action exhibited synergism. With the increase of time, these stimulatory and inhibitory effects of SMP and C30 were changed by the variation of the QS system at different growth phases, resulting in the time-dependent cross-phenomenon. This study proposes an induced mechanism for time-dependent cross-phenomenon based on QS, which may provide new insight into the mechanistic investigation of time-dependent cross-phenomenon, benefitting the environmental risk assessment of mixtures.

A swinging seesaw as a novel model mechanism for time-dependent hormesis under dose-dependent stimulatory and inhibitory effects: A case study on the toxicity of antibacterial chemicals to Aliivibrio fischeri.

Hormesis occurs frequently in broadly ranging biological areas (e.g. plant biology, microbiology, biogerontology), toxicology, pharmacology and medicine. While numerous mechanisms (e.g. receptor and pathway mediated pathway responses) account for stimulatory and inhibitory features of hormetic dose responses, the vast majority emphasizes the inclusion of many doses but only one timepoint or use of a single optimized dose that is assessed over a broad range of timepoints. In this paper, a toxicity study was designed using a large number of properly spaced doses with responses determined over a large number of timepoints, which could help us reveal the underlying mechanism of hormesis. We present the results of a dose-time-response study on hormesis using five antibacterial chemicals on the bioluminescence of Aliivibrio fischeri, measuring expression of protein mRNA based on quorum sensing, simulating bioluminescent reaction and analyzing toxic actions of test chemicals. The findings show dose-time-dependent responses conforming to the hormetic dose-response model, while revealing unique response dynamics between agent induced stimulatory and inhibitory effects within bacterial growth phase dynamics. These dynamic dose-time features reveal a type of biological seesaw model that integrates stimulatory and inhibitory responses within unique growth phase, dose and time features, which has faultlessly explained the time-dependent hormetic phenomenon induced by five antibacterial chemicals (characterized by low-dose stimulation and high-dose inhibition). This study offers advances in understanding cellular dynamics, the biological integration of diverse and opposing responses and their role in evolutionary adaptive strategies to chemicals, which can provide new insight into the mechanistic investigation of hormesis.

Clothing polymer fibers with well-aligned and high-aspect ratio carbon nanotubes.

It is believed that the crucial step towards preparation of electrical conductive polymer-carbon nanotube (CNT) composites is dispersing CNTs with a high length-to-diameter aspect ratio in a well-aligned manner. However, this process is extremely challenging when dealing with long and entangled CNTs. Here in this study, a new approach is demonstrated to fabricate conductive polymer-CNT composite fibers without involving any dispersion process. Well-aligned CNT films were firstly drawn from CNT arrays, and then directly coated on polycaprolactone fibers to form polymer-CNT composite fibers. The conductivity of these composite fibers can be as high as 285 S m(-1) with only 2.5 wt% CNT loading, and reach 1549 S m(-1) when CNT loading is 13.4 wt%. As-prepared composite fibers also exhibit 82% retention of conductivity at a strain of 7%, and have improved mechanical properties.

The application of graphene oxide in drug delivery.

INTRODUCTION: As a shining star in material science, graphene oxide (GO) and its derivatives possess potential applications in a variety of areas. Among them, the application of GO to drug delivery has attracted ever-increasing interest in the past few years. AREAS COVERED: In this article, the authors summarize the latest progress of utilizing GO in the field of drug delivery. In particular, the functionalization of GO, cytotoxicity of GO and its derivatives, in vitro and in vivo drug delivery and the comparison with carbon nanotube-based delivery systems are discussed. Future perspectives and possible challenges in this emerging field are briefly described. EXPERT OPINION: GO and its derivatives are highly attractive for the application to drug delivery due to their exceptional physiochemical properties and unique planar structure in spite of some existing challenges, such as the reproducibly smart functionalization of GO and the investigation of its long-term toxicology.

Graphene-based materials for energy conversion.

With the depletion of conventional energy sources, the demand for renewable energy and energy-efficient devices continues to grow. As a novel 2D nanomaterial, graphene attracts considerable research interest due to its unique properties and is a promising material for applications in energy conversion and storage devices. Recently, the fabrication of fuel cells and solar cells using graphene for various functional parts has been studied extensively. This research news summarizes and compares the advancements that have been made and are in progress in the utilization of graphene-based materials for energy conversion.

Poly(vinyl alcohol) nanocomposites filled with poly(vinyl alcohol)-grafted graphene oxide.

We present a novel approach to the fabrication of advanced polymeric nanocomposites from poly(vinyl alcohol) (PVA) by incorporation of PVA-grafted graphene oxide. In this work, we have synthesized PVA-grafted graphene oxide (PVA-g-GO) for the strong interfacial adhesion of graphene oxide (GO) to the PVA matrix. It was found that the mechanical properties of PVA were greatly improved by incorporating PVA-g-GO. For example, the tensile strength and Young's modulus of the PVA nanocomposite films containing 1 wt % net GO in the PVA-g-GO significantly increased by 88 and 150%, respectively, as compared to unfilled PVA. The elongation at break was also increased by 22%, whereas the GO/PVA nanocomposite containing 1 wt % pristine GO was decreased by 15%. Therefore, the presence of the PVA-g-GO in the PVA matrix could make the PVA not only stronger but also tougher. The strong interfacial adhesion between PVA-g-GO and the PVA matrix was attributed to the good compatibility between PVA-g-GO and the matrix PVA as well as the hydrogen-bonding between them.

Noncovalently functionalized multiwalled carbon nanotubes by chitosan-grafted reduced graphene oxide and their synergistic reinforcing effects in chitosan films.

Water-soluble chitosan-grafted reduced graphene oxide (CS-rGO) sheets are successfully synthesized via amidation reaction and chemical reduction. CS-rGO possesses not only remarkable graphitic property but also favorable water solubility, which is found to be able to effectively disperse multiwalled carbon nanotubes (MWCNTs) in acidic solutions via noncovalent interaction. The efficiency of CS-rGO in dispersing MWCNTs is tested to be higher than that of plain graphene oxide (GO) and a commercial surfactant, sodium dodecyl sulfate (SDS). With incorporation of 1 wt % CS-rGO dispersed MWCNTs (CS-rGO-MWCNTs), the tensile modulus, strength and toughness of the chitosan (CS) nanocomposites can be increased by 49, 114, and 193%, respectively. The reinforcing and toughening effects of CS-rGO-MWCNTs are much more prominent than those of single-component fillers, such as MWCNTs, GO, and CS-rGO. Noncovalent π-π interactions between graphene sheets and nanotubes and hydrogen bonds between grafted CS and the CS matrix are responsible for generating effective load transfer between CS-rGO-MWCNTs and the CS matrix, causing the simultaneously increased strength and toughness of the nanocomposites.

Functionalized carbon nanomaterials as nanocarriers for loading and delivery of a poorly water-soluble anticancer drug: a comparative study.

Carbon nanomaterials such as multiwalled carbon nanotubes (MWCNTs) and graphene oxide (GO) have been functionalized by highly hydrophilic and biocompatible poly(vinyl alcohol) (PVA) for loading and delivery of an anticancer drug, camptothecin (CPT). For the first time, CPT was loaded onto MWCNT-PVA and GO-PVA through π-π interactions and its capability to kill human breast and skin cancer cells was investigated.

Study on superhydrophobic hybrids fabricated from multiwalled carbon nanotubes and stearic acid.

A waterproof biomaterial, stearic acid (STA), which is one of components of the wax present on the lotus leaf surface, was used as the material with low surface energy to fabricate superhydrophobic multiwalled carbon nanotube (MWCNT) hybrids through a solution method. This method involved preparation of a sodium stearate (SST)-stabilized MWCNT dispersion, followed by a precipitating process. STA was assembled on the MWCNT-SST hybrid surface by a reaction of SST with acetic acid. The rough surface with multiscale protuberances was revealed by scanning electron microscopy (SEM). The effect of SST/MWCNT weight ratio on water contact angle (CA) and the temperature dependence and alkali resistance of superhydrophobicity of MWCNT hybrids have been investigated. With increasing the SST/MWCNT weight ratio, the water CA of MWCNT hybrid increased and then decreased after a maximum value of 163 degrees at the ratio of 1/1. It was interesting that the wetting property of MWCNT hybrids (SST/MWCNT=0.5/1 and 1/1) was tunable between superhydrophobicity and superhydrophilicity by changing temperature. Potential applications of these superhydrophobic materials to make large-area superhydrophobic coatings have been proposed.