Purified fluorescent nanohybrids based on quantum dot-HER2-antibody for breast tumor target imaging.

Quantum dots (QDs) have been widely used for bioimaging in vivo because of their excellent optical properties. As part of the preparation process of QD-based nanohybrids, purification is an important step for minimizing contaminants and improving the quality of the product. In this work, we describe high-performance size exclusion chromatography (HPSEC) used to purify nanohybrids of CdSe/ZnS QDs and anti-human epidermal growth factor receptor 2 antibodies (QD-HER2-Ab). The unbound antibody and suspended agglomerates were removed from freshly prepared QD-HER2-Ab via HPSEC. Pure and homogeneous QD-HER2-Ab were then used as immunofluorescence target imaging bioprobes in vivo. The QD-HER2-Ab did not cause any obvious acute toxicity in mice one week after a single intravenous injection of 15 nmol/kg. The purified QD-HER2-Ab bioprobes showed high tumor targeting ability in a human breast tumor xenograft nude mouse model (24 h after injected) with the possibility of in vivo immunofluorescence tumor imaging. The immunofluorescence imaging background signal and acute toxicity in vivo were minimized because of the reduction of residual QDs. HPSEC-purified QD-HER2-Ab is an accurate and convenient tool for in vivo tumor target imaging and HER2 detection, thus providing a basis for the purification of other QD-based bioprobes.

Quaternary ammonium iminofullerenes improve root growth of oxidative-stress maize through ASA-GSH cycle modulating redox homeostasis of roots and ROS-mediated root-hair elongation.

BACKGROUND: Various environmental factors are capable of oxidative stress to result in limiting plant development and agricultural production. Fullerene-based carbon nanomaterials can enable radical scavenging and positively regulate plant growth. Even so, to date, our knowledge about the mechanism of fullerene-based carbon nanomaterials on plant growth and response to oxidative stress is still unclear. RESULTS: 20 or 50 mg/L quaternary ammonium iminofullerenes (IFQA) rescued the reduction in root lengths and root-hair densities and lengths of Arabidopsis and maize induced by accumulation of endogenous hydrogen peroxide (H2O2) under 3-amino-1,2,4-triazole or exogenous H2O2 treatment, as well as the root active absorption area and root activity under exogenous H2O2 treatment. Meanwhile, the downregulated contents of ascorbate acid (ASA) and glutathione (GSH) and the upregulated contents of dehydroascorbic acid (DHA), oxidized glutathione (GSSG), malondialdehyde (MDA), and H2O2 indicated that the exogenous H2O2 treatment induced oxidative stress of maize. Nonetheless, application of IFQA can increase the ratios of ASA/DHA and GSH/GSSG, as well as the activities of glutathione reductase, and ascorbate peroxidase, and decrease the contents of H2O2 and MDA. Moreover, the root lengths were inhibited by buthionine sulfoximine, a specific inhibitor of GSH biosynthesis, and subsequently rescued after addition of IFQA. The results suggested that IFQA could alleviate exogenous-H2O2-induced oxidative stress on maize by regulating the ASA-GSH cycle. Furthermore, IFQA reduced the excess accumulation of ROS in root hairs, as well as the NADPH oxidase activity under H2O2 treatment. The transcript levels of genes affecting ROS-mediated root-hair development, such as RBOH B, RBOH C, PFT1, and PRX59, were significantly induced by H2O2 treatment and then decreased after addition of IFQA. CONCLUSION: The positive effect of fullerene-based carbon nanomaterials on maize-root-hair growth under the induced oxidative stress was discovered. Application IFQA can ameliorate oxidative stress to promote maize-root growth through decreasing NADPH-oxidase activity, improving the scavenging of ROS by ASA-GSH cycle, and regulating the expressions of genes affecting maize-root-hair development. It will enrich more understanding the actual mechanism of fullerene-based nanoelicitors responsible for plant growth promotion and protection from oxidative stress.

Quaternary ammonium iminofullerenes promote root growth and osmotic-stress tolerance in maize via ROS neutralization and improved energy status.

In the present study, the role of quaternary ammonium iminofullerenes (IFQA) on the root growth of plant seedlings was investigated. The root elongation of Arabidopsis and maize exposed to 20 and 50 mg/L of IFQA was promoted under normal and osmotic stress conditions, respectively. In the meantime, the root active absorption area and adenosine triphosphate content in roots of maize seedlings were enhanced by IFQA treatment, however, the contents of hydrogen peroxide (H2O2) and malondialdehyde in roots were down-regulated. IFQA application improved glutathione transferase and glutathione reductase activities and the ratios of glutathione/oxidized glutathione and ascorbic acid/dehydroascorbic acid, and restored the inhibition of root elongation caused by the excess accumulation of H2O2 in roots of maize seedlings under osmotic stress. Furthermore, the expression of 14 proteins involved in cell growth, energy metabolism, and stress response in maize roots was upregulated by two-dimensional electrophoresis combined with mass spectrometry. This analysis revealed that IFQA stimulated the redox pathway to maintain balance levels of reactive oxygen species to ensure normal cell metabolism, promote energy production for root growth, and enhance osmotic-stress tolerance. It provided crucial information to elucidate the mechanism of the root growth of crop seedlings enhanced by water-soluble fullerene-based nanomaterials.

Molecular mechanism of nanochitin whisker elicits plant resistance against Phytophthora and the receptors in plants.

Rod-like nanochitin (NC) whisker with cationic nature has a strong synergistic effect with fungicides on inhibition of tobacco root rot disease. This study we explored the activity of NC against Phytophthora and the mechanism for eliciting plant defense response and the receptors in planta. P. capsici isolates, model Nicotiana benthamiana plants and Arabidopsis thaliana were treated with 0.005% of NC suspension and 1 µM of flg22. Infection control efficacy against P. capsici isolates, biosynthetic enzyme activities and the PR genes expression were determined at different hours post treatment in plant. The infection control efficacy, ROS generation, and PTI maker gene expression were re-analyzed in A. thaliana Col-0, bak1 and cerk1 mutants. The results showed that NC did not exhibit inhibitory effect on vegetative growth of P. capsici, but enhanced the resistance against P. capsici by systemically enhanced phenylalanine ammonia-lyase activity and PR gene expression. P. capsici resistance, PTI maker gene promotion, and ROS production in A. thaliana induced by NC depended not only on chitin receptor CERK1, but also BAK1. NC and flg22 induced oomycete immunity through a mechanism of a cross-microbe protection via the BAK1-CERK1 pathway in plant, pointing to the complexity of the plant immunity system.

Synergistic effects of nanochitin on inhibition of tobacco root rot disease.

Nanomaterials have great potential for use in various fields, due to their unique properties. In order to explore the bioactivity of nanochitin on tobacco, the effects of nanochitin suspensions on tobacco seed germination, seedling growth, and synergistic effects with fungicides were studied in indoor and field trials. Results showed that 0.004% (w/v) of nanochitin improved tobacco seed germination and shortened mean time to germination significantly; 0.005% (w/v) of nanochitin increased tobacco stem length, stem girth, leaf number and leaf area, and 0.001% (w/v) of nanochitin had synergistic effects on inhibition of tobacco root rot when mixed with metalaxyl mancozeb and thiophanate methyl fungicides. This indicates that nanochitin suspensions have a strong potential to protect tobacco from tobacco root rot diseases and reduce the use of chemical fungicides in tobacco plantations.