Highly hydrophilic carbon nanoparticles: uptake mechanism by mammalian and plant cells

In-cell Catalysis by Tethered Organo-Osmium Complexes Generates Selectivity for Breast Cancer Cells

Anticancer agents that exhibit catalytic mechanisms of action offer a unique multi-targeting strategy to overcome drug resistance. Nonetheless, many in-cell catalysts in development are hindered by deactivation by endogenous nucleophiles. We have synthesised a highly potent, stable Os-based 16-electron half-sandwich ('piano stool') catalyst by introducing a permanent covalent tether between the arene and chelated diamine ligand. This catalyst exhibits antiproliferative activity comparable to the clinical drug cisplatin towards triple-negative breast cancer cells and can overcome tamoxifen resistance. Speciation experiments revealed Os to be almost exclusively albumin-bound in the extracellular medium, while cellular accumulation studies identified an energy-dependent, protein-mediated Os accumulation pathway, consistent with albumin-mediated uptake. Importantly, the tethered Os complex was active for in-cell transfer hydrogenation catalysis, initiated by co-administration of a non-toxic dose of sodium formate as a source of hydride, indicating that the Os catalyst is delivered to the cytosol of cancer cells intact. The mechanism of action involves the generation of reactive oxygen species (ROS), thus exploiting the inherent redox vulnerability of cancer cells, accompanied by selectivity for cancerous cells over non-tumorigenic cells.

Integrated analyses of ionomics, phytohormone profiles, transcriptomics, and metabolomics reveal a pivotal role of carbon-nano sol in promoting the growth of tobacco plants

BACKGROUND

Carbon nano sol (CNS) can markedly affect the plant growth and development. However, few systematic analyses have been conducted on the underlying regulatory mechanisms in plants, including tobacco (Nicotiana tabacum L.).

RESULTS

Integrated analyses of phenome, ionome, transcriptome, and metabolome were performed in this study to elucidate the physiological and molecular mechanisms underlying the CNS-promoting growth of tobacco plants. We found that 0.3% CNS, facilitating the shoot and root growth of tobacco plants, significantly increased shoot potassium concentrations. Antioxidant, metabolite, and phytohormone profiles showed that 0.3% CNS obviously reduced reactive oxygen species production and increased antioxidant enzyme activity and auxin accumulation. Comparative transcriptomics revealed that the GO and KEGG terms involving responses to oxidative stress, DNA binding, and photosynthesis were highly enriched in response to exogenous CNS application. Differential expression profiling showed that NtNPF7.3/NtNRT1.5, potentially involved in potassium/auxin transport, was significantly upregulated under the 0.3% CNS treatment. High-resolution metabolic fingerprints showed that 141 and 163 metabolites, some of which were proposed as growth regulators, were differentially accumulated in the roots and shoots under the 0.3% CNS treatment, respectively.

CONCLUSIONS

Taken together, this study revealed the physiological and molecular mechanism underlying CNS-mediated growth promotion in tobacco plants, and these findings provide potential support for improving plant growth through the use of CNS.

Carbon nanosol-induced assemblage of a plant-beneficial microbiome consortium

Carbon nanosol (CNS) is a carbon-based nanomaterial that promotes plant growth; however, its functional mechanisms and effects on the microbiome are not fully understood. Here, we explored the effects of CNS on the relationship between the soil, endophytic microbiomes and plant productivity. CNS treatment increased the fresh biomass of tobacco (Nicotiana tabacum L.) plants by 27.4% ± 9.9%. Amplicon sequencing analysis showed that the CNS treatment significantly affected the composition and diversity of the microbial communities in multiple ecological niches associated with tobacco, especially the bulk soil and stem endophytic microbiome. Furthermore, the application of CNS resulted in enhanced network connectivity and stability of the microbial communities in different niches, particularly in the soil, implying a strengthening of certain microbial interactions. Certain potentially growth-promoting root endophytic bacteria were more abundant under the CNS treatment. In addition, CNS increased the abundance of some endophytic microbial functional genes known to enhance plant growth, such as those associated with nutrient metabolism and the plant hormone biosynthesis pathways. We isolated two bacterial strains (Sphingopyxis sp. and Novosphingobium sp.) that were enriched under CNS treatment, and they were confirmed to promote tobacco plant growth in vitro. These results suggested that CNS might, at least in part, promote plant growth by enriching beneficial bacteria in the microbiome.

Graphene quantum dot doped viscoelastic lyotropic liquid crystal nanocolloids for antibacterial applications

Graphene quantum dots (GQDs) are prepared and characterized via X-ray diffraction (XRD), UV-Visible spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL). GQDs are doped (5 mg and 10 mg) in the lyotropic liquid crystalline (LLC) lamellar and hexagonal phases to prepare GQD/LLC nanocolloids. Polarizing optical microscopy and X-ray diffraction measurement reveals that GQDs do not affect the lamellar and hexagonal LLC structures and may organize on their interface. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and GQD/LLC nanocolloids possess shear thinning and frequency dependent liquid viscoelastic behavior. A complex moduli study of LLCs and GQD/LLC nanocolloids is carried out which indicates the gel to viscous transition in LLCs and GQD/LLC nanocolloids as a function of frequency. LLC phases and GQD/LLC nanocolloids are tested for antibacterial activity against Listeria ivanovii. The effect of surfactant concentration, LLC phase geometry and GQD concentration has been studied and discussed. A probable mechanism for the strong antimicrobial activity of LLCs and GQD/LLC nanocolloids is presented considering intermolecular interactions. The viscoelastic behavior and strong antibacterial activity (inhibition zone 49.2 mm) of LLCs and GQD/LLC nanocolloids make them valuable candidates for lubrication, cleaning, cosmetics and pharmaceutical applications.

Red emitting fluorescent carbon nanoparticles to track spatio-temporal dynamics of endocytic pathways in model neuroblastoma neurons

One of the biggest challenges limiting the biological applications of fluorescent carbon-based nanoparticles is their capacity to emit in the red region of the spectrum and simultaneously maintaining the smaller size. These two parameters always go in inverse proportion, thus lagging their applications in biological imaging. Endocytic pathways play important roles in regulating major cellular functions such as cellular differentiation. The Spatio-temporal dynamics of endocytic pathways adopted by various ligands (including nanoparticles) over longer durations in cellular differentiation remain unstudied. Here we have used red-emitting fluorescent carbon nanoparticles to study the endocytic pathways in neuronal cells at different stages of differentiation. These small-sized, bright, red-emitting carbon nanoparticles (CNPs) can be internalized by live cells and imaged for extended periods, thus capturing the Spatio-temporal dynamics of endocytic pathways in model SH-SY5Y derived neuroblastoma neurons. We find that these nanoparticles are preferably taken up via clathrin-mediated endocytosis and follow the classical recycling pathways at all the stages of neuronal differentiation. These nanoparticles hold immense potential for their size, composition, surface and fluorescence tunability, thus maximizing their applications in spatio-temporally tracking multiple cellular pathways in cells and tissues simultaneously.

α-Synuclein fibrils explore actin mediated macropinocytosis for cellular entry into model neuroblastoma neurons

Alpha-Synuclein (α-Syn), an intrinsically disordered protein (IDP), is associated with neurodegenerative disorders, including Parkinson's disease (PD) or other α-synucleinopathies. Recent investigations propose the transmission of α-Syn protein fibrils, in a prion-like manner, by entering proximal cells to seed further fibrillization in PD. Despite the recent advances, the mechanisms by which extracellular protein aggregates internalize into the cells remain poorly understood. Using a simple cell-based model of human neuroblastoma-derived differentiated neurons, we present the cellular internalization of α-Syn PFF to check cellular uptake and recycling kinetics along with the standard endocytic markers Transferrin (Tf) marking clathrin-mediated endocytosis (CME) and Galectin3 (Gal3) marking clathrin-independent endocytosis (CIE). Specific inhibition of endocytic pathways using chemical inhibitors reveals no significant involvement of CME, CIE, and caveolae-mediated endocytosis (CvME). A substantial reduction in cellular uptake was observed after perturbation of actin polymerization and treatment with macropinosomes inhibitor. Our results show that α-Syn PFF mainly internalizes into the SH-SY5Y cells and differentiated neurons via the macropinocytosis pathway. The elucidation of the molecular and cellular mechanism involved in the α-Syn PFF internalization will help improve the understanding of α-synucleinopathies including PD, and further design specific inhibitors for the same.

Cancer cells targeting with genetically engineered constructs based on a pH-dependent membrane insertion peptide and fluorescent protein

The targeted delivery of nanodrugs to malignant neoplasm is one of the most pressing challenges in the development of modern medicine. It was reported earlier that a bacteriorhodopsin-derived pH low insertion peptide (pHLIP) targets acidic tumors and has the ability to translocate low molecular weight cargoes across the cancer cell membrane. Here, to better understand the potential of pHLIP-related technologies, we used genetically engineered fluorescent protein (EGFP) as a model protein cargo and examined targeting efficiencies of EGFP-pHLIP hybrid constructs in vitro with the HeLa cell line at different pHs. By two independent monitoring methods we observed an increased binding affinity of EGFP-pHLIP fusions to HeLa cells at pH below 6.8. Confocal images of EGFP-pHLIP-treated cells showed bright fluorescence associated with the cell membrane and fluorescent dots localized inside the cell, that became brighter with time. To elucidate the pHLIP-mediated EGFP cell entry mechanisms, we performed a series of experiments with specific inhibitors of endocytosis. Our results imply that EGFP-pHLIP internalization is realized by endocytosis of various types.

Peroxidase catalytic activity of carbon nanoparticles for glutathione detection

Peroxidases are present widely in microorganisms and plants, and catalyze many reactions. However, the activity of natural peroxidases is susceptible to external conditions. We prepared carbon nanoparticles (CNPs) using an environmentally friendly and simple method. These CNPs were demonstrated to possess intrinsic peroxidase-like activity. CNPs could catalyze the reaction of a peroxidase substrate, 3,3,5,5-tetramethylbenzidine (TMB), in the presence of H2O2 to produce a blue solution at 652 nm. CNPs exhibited higher peroxidase activity than that of other carbon-based nanomaterials. Moreover, CNPs retained their high peroxidase activity after being reused several times. Glutathione (GSH) can change the blue color of oxidized TMB into a colorless hue at 652 nm. Based on this fact, qualitative and quantitative approaches were employed to detect GSH using a colorimetric method. This method showed a broad detection range (2.5-50 μM) with a limit of detection of 0.26 μM. This method was shown to be accurate for GSH detection in a cell culture medium compared with that using a commercial assay kit. Our findings could facilitate application of CNPs in biomedical areas.

Designer nanoparticles for plant cell culture systems: Mechanisms of elicitation and harnessing of specialized metabolites

Plant cell culture systems have become an attractive and sustainable approach to produce high-value and commercially significant metabolites under controlled conditions. Strategies involving elicitor supplementation into plant cell culture media are employed to mimic natural conditions for increasing the metabolite yield. Studies on nanoparticles (NPs) that have investigated elicitation of specialized metabolism have shown the potential of NPs to be a substitute for biotic elicitors such as phytohormones and microbial extracts. Customizable physicochemical characteristics allow the design of monodispersed-, stimulus-responsive-, and hormone-carrying-NPs of precise geometries to enhance their elicitation capabilities based on target metabolite/plant cell culture type. We contextualize advances in NP-mediated elicitation, especially stimulation of specialized metabolic pathways, the underlying mechanisms, impacts on gene regulation, and NP-associated cytotoxicity. The novelty of the concept lies in unleashing the potential of designer NPs to enhance yield, harness metabolites, and transform nanoelicitation from exploratory investigations to a commercially viable strategy.

Uptake and Toxicity of Respirable Carbon-Rich Uranium-Bearing Particles: Insights into the Role of Particulates in Uranium Toxicity

Particulate matter (PM) presents an environmental health risk for communities residing close to uranium (U) mine sites. However, the role of the particulate form of U on its cellular toxicity is still poorly understood. Here, we investigated the cellular uptake and toxicity of C-rich U-bearing particles as a model organic particulate containing uranyl citrate over a range of environmentally relevant concentrations of U (0-445 μM). The cytotoxicity of C-rich U-bearing particles in human epithelial cells (A549) was U-dose-dependent. No cytotoxic effects were detected with soluble U doses. Carbon-rich U-bearing particles with a wide size distribution (<10 μm) presented 2.7 times higher U uptake into cells than the particles with a narrow size distribution (<1 μm) at 100 μM U concentration. TEM-EDS analysis identified the intracellular translocation of clusters of C-rich U-bearing particles. The accumulation of C-rich U-bearing particles induced DNA damage and cytotoxicity as indicated by the increased phosphorylation of the histone H2AX and cell death, respectively. These findings reveal the toxicity of the particulate form of U under environmentally relevant heterogeneous size distributions. Our study opens new avenues for future investigations on the health impacts resulting from environmental exposures to the particulate form of U near mine sites.

Application of chloroquine as an endosomal escape enhancing agent: new frontiers for an old drug

INTRODUCTION

Adequate transfection efficiency is indispensable to safe and effective delivery of therapeutically active agents, particularly in cancer. Endosomal escape is regarded as a critical and determining step devoted a significant number of studies of the drug/gene delivery field.

AREAS COVERED

This paper critically reviews the fundamental properties of chloroquine (CQ), its pharmacokinetics, pharmacodynamics, and clinical applications and the present knowledge of CQ application as an endosomal escape enhancing agent. Different approaches to enhance the endosomal escape process of nanoparticles have been introduced including use of endosomal escape enhancing agents. Application of CQ as either a pre-treatment modality in which cells or animals are exposed to CQ prior to the main treatment or a component of co-delivery systems where CQ and other anti-cancer agents are simultaneously entered the cancer cells, is discussed with recent studies.

EXPERT OPINION

CQ is founded to intervene with the natural process of endosomal maturation. Moreover, CQ seems to increase the effectiveness of gene delivery by its electrostatic interaction with negatively charged components of the transferred genetic molecules. Endosomal escape might be regarded as the bottleneck of efficient gene delivery and CQ as an effective and available endosomal escape enhancing agent deserves more sophisticated studies.

Carbon nanoparticles enhance potassium uptake via upregulating potassium channel expression and imitating biological ion channels in BY-2 cells

BACKGROUND

Carbon nanoparticles (CNPs) have been reported to boost plant growth, while the mechanism that CNPs enhanced potassium uptake for plant growth has not been reported so far.

RESULTS

In this study, the function that CNPs promoted potassium uptake in BY-2 cells was established and the potassium accumulated in cells had a significant correlation with the fresh biomass of BY-2 cells. The K+ accumulation in cells increased with the increasing concentration of CNPs. The K+ influx reached high level after treatment with CNPs and was significantly higher than that of the control group and the negative group treated with K+ channels blocker, tetraethylammonium chloride (TEA+). The K+ accumulation was not reduced in the presence of CNPs inhibitors. In the presence of potassium channel blocker TEA+ or CNPs inhibitors, the NKT1 gene expression was changed compared with the control group. The CNPs were found to preferentially transport K+ than other cations determined by rectification of ion current assay (RIC) in a conical nanocapillary.

CONCLUSIONS

These results indicated that CNPs upregulated potassium gene expression to enhance K+ accumulation in BY-2 cells. Moreover, it was speculated that the CNPs simulated protein of ion channels via bulk of carboxyl for K+ permeating. These findings will provide support for improving plant growth by carbon nanoparticles.

Spectroscopic approach for the interaction of carbon nanoparticles with cytochrome c and BY-2 cells: Protein structure and mitochondrial function

In this study, we employed multiple spectroscopic methods to analyze the effects of carbon nanoparticles (CNPs) on structure of cytochrome c (Cyt c) and mitochondrial function in plant cells. The tertiary structures of aromatic amino acid in Cyt c were not changed after addition of CNPs. Cyt c was found to be absorbed on the surfaces of CNPs in a non-linear manner and only bound Cyt c can be reduced. In addition, the binding of Cyt c was found to increase the diameter of CNPs at lower concentrations. The redox potential of Cyt c was almost not affected after treatment with CNPs. There were no obvious differences in cellular ATP after exposure to CNPs, and the mitochondrial membrane potential (MMP) was significantly decreased once the CNPs concentration exceeded 31.25 μg/mL. The levels of reactive oxygen species (ROS) also were increased in BY-2 cells. Taken together, these findings provide basis for the interactions between CNPs and Cyt c, as well as the effect of CNPs treatment on the mitochondria function in plant cells.