Will the public swallow nanofood?

Herbicidal weed management practices: History and future prospects of nanotechnology in an eco-friendly crop production system

Weed management is an important aspect of crop production, as weeds cause significant losses in terms of yield and quality. Various approaches to weed management are commonly practiced by crop growers. Due to limitations in other control methods, farmers often choose herbicides as a cost-effective, rapid and highly efficient weed control strategy. Although herbicides are highly effective on most weeds, they are not a complete solution for weed management because of the genetic diversity and evolving flexibility of weed communities. The excessive and indiscriminate use of herbicides and their dominance in weed control have triggered the rapid generation of herbicide-resistant weed species. Moreover, environmental losses of active ingredients in the herbicides cause serious damage to the environment and pose a serious threat to living organisms. Scientific advances have enabled nanotechnology to emerge as an innovation with real potential in modern agriculture, adding a new dimension in the preparation of controlled release formulations (CRF) of herbicides. Here the required amount of active ingredients is released over longer periods of time to obtain the desired biological efficacy whilst reducing the harmful effects of these chemicals. Various organic and inorganic carrier materials have been utilised in CRF and researchers have a wide range of options for the synthesis of eco-friendly carrier materials, especially those with less or no toxicity to living organisms. This manuscript addresses the history, progress, and consequences of herbicide application, and discusses potential ways to reduce eco-toxicity due to herbicide application, along with directions for future research areas using the benefits of nanotechnology.

Landscape of lipidomic metabolites in gut-liver axis of Sprague-Dawley rats after oral exposure to titanium dioxide nanoparticles

Background

The application of titanium dioxide nanoparticles (TiO₂ NPs) as food additives poses a risk of oral exposure that may lead to adverse health effects. Even though the substantial evidence supported liver as the target organ of TiO₂ NPs via oral exposure, the mechanism of liver toxicity remains largely unknown. Since the liver is a key organ for lipid metabolism, this study focused on the landscape of lipidomic metabolites in gut-liver axis of Sprague Dawley (SD) rats exposed to TiO₂ NPs at 0, 2, 10, 50 mg/kg body weight per day for 90 days.

Results

TiO₂ NPs (50 mg/kg) caused slight hepatotoxicity and changed lipidomic signatures of main organs or systems in the gut-liver axis including liver, serum and gut. The cluster profile from the above biological samples all pointed to the same key metabolic pathway and metabolites, which was glycerophospholipid metabolism and Phosphatidylcholines (PCs), respectively. In addition, absolute quantitative lipidomics verified the changes of three PCs concentrations, including PC (16:0/20:1), PC (18:0/18:0) and PC (18:2/20:2) in the serum samples after treatment of TiO₂ NPs (50 mg/kg). The contents of malondialdehyde (MDA) in serum and liver increased significantly, which were positively correlated with most differential lipophilic metabolites.

Conclusions

The gut was presumed to be the original site of oxidative stress and disorder of lipid metabolism, which resulted in hepatotoxicity through the gut-liver axis. Lipid peroxidation may be the initial step of lipid metabolism disorder induced by TiO₂ NPs. Most nanomaterials (NMs) have oxidation induction and antibacterial properties, so the toxic pathway revealed in the present study may be primary and universal.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00484-9.

Toxicologic Evaluation for Amorphous Silica Nanoparticles: Genotoxic and Non-Genotoxic Tumor-Promoting Potential

Amorphous silica nanoparticles (SiO₂NPs) have been widely used in medicine including targeted drug/DNA delivery, cancer therapy, and enzyme immobilization. Nevertheless, SiO₂NPs should be used with caution due to safety concerns associated with unique physical and chemical characteristics. The objective of this study was to determine the effects of SiO₂NPs on genotoxic and non-genotoxic mechanisms associated with abnormal gap junctional intercellular communication (GJIC) in multistage carcinogenesis. The SiO₂NPs exhibited negative responses in standard genotoxicity tests including the Ames test, chromosome aberration assay, and micronucleus assay. In contrast, the SiO₂NPs significantly induced DNA breakage in comet assay. Meanwhile, SiO₂NPs inhibited GJIC based on the results of scrape/loading dye transfer assay for the identification of non-genotoxic tumor-promoting potential. The reduction in expression and plasma membrane localization of Cx43 was detected following SiO₂NP treatment. Particularly, SiO₂NP treatment increased Cx43 phosphorylation state, which was significantly attenuated by inhibitors of extracellular signal-regulated kinases 1/2 (ERK1/2) and threonine and tyrosine kinase (MEK), but not by protein kinase C (PKC) inhibitor. Taken together, in addition to a significant increase in DNA breakage, SiO₂NP treatment resulted in GJIC dysregulation involved in Cx43 phosphorylation through the activation of mitogen-activated protein kinase (MAPK) signaling. Overall findings of the genotoxic and non-genotoxic carcinogenic potential of SiO₂NPs provide useful toxicological information for clinical application at an appropriate dose.

Nanotechnology-based approaches for food sensing and packaging applications

The rapid advancement of nanotechnology has provided opportunities for the development of new sensing and food packaging solutions, addressing long-standing challenges in the food sector to extend shelf-life, reduce waste, assess safety and improve the quality of food. Nanomaterials can be used to reinforce mechanical strength, enhance gas barrier properties, increase water repellence, and provide antimicrobial and scavenging activity to food packaging. They can be incorporated in chemical and biological sensors enabling the design of rapid and sensitive devices to assess freshness, and detect allergens, toxins or pathogenic contaminants. This review summarizes recent studies on the use of nanomaterials in the development of: (1) (bio)sensing technologies for detection of nutritional and non-nutritional components, antioxidants, adulterants and toxicants, (2) methods to improve the barrier and mechanical properties of food packaging, and (3) active functional packaging. The environmental, health and safety implications of nanomaterials in the food sector, along with an overview of regulation and consumer perception is also provided.

Application of nanotechnology based-biosensors in analysis of wine compounds and control of wine quality and safety: A critical review

Nanotechnology is one of the most promising future technologies for the food industry. Some of its applications have already been introduced in analytical techniques and food packaging technologies. This review summarizes existing knowledge about the implementation of nanotechnology in wine laboratory procedures. The focus is mainly on recent advancements in the design and development of nanomaterial-based sensors for wine compounds analysis and assessing wine safety. Nanotechnological approaches could be useful in the wine production process, to simplify wine analysis methods, and to improve the quality and safety of the final product.

The current application of nanotechnology in food and agriculture

The rapid development of nanotechnology has been facilitating the transformations of traditional food and agriculture sectors, particularly the invention of smart and active packaging, nanosensors, nanopesticides and nanofertilizers. Numerous novel nanomaterials have been developed for improving food quality and safety, crop growth, and monitoring environmental conditions. In this review the most recent trends in nanotechnology are discussed and the most challenging tasks and promising opportunities in the food and agriculture sectors from selected recent studies are addressed. The toxicological fundamentals and risk assessment of nanomaterials in these new food and agriculture products are also discussed. We highlighted the potential application of bio-synthesized and bio-inspired nanomaterial for sustainable development. However, fundamental questions with regard to high performance, low toxic nanomaterials need to be addressed to fuel active development and application of nanotechnology. Regulation and legislation are also paramount to regulating the manufacturing, processing, application, as well as disposal of nanomaterials. Efforts are still needed to strengthen public awareness and acceptance of the novel nano-enabled food and agriculture products. We conclude that nanotechnology offers a plethora of opportunities, by providing a novel and sustainable alternative in the food and agriculture sectors.

Review of the effects of silver nanoparticle exposure on gut bacteria

Gut bacteria are involved in regulating several important physiological functions in the host, and intestinal dysbacteriosis plays an important role in several human diseases, including intestinal, metabolic and autoimmune disorders. Although silver nanoparticles (AgNPs) are increasingly being incorporated into medical and consumer products due to their unique physicochemical properties, studies have indicated their potential to affect adversely the gut bacteria. In this review, we focus on the biotoxicological effects of AgNPs entering the gastrointestinal tract and the relationship of these effects with important nanoscale properties. We discuss in detail the mechanisms underlying the bactericidal toxicity effects of AgNPs and explore the relationships between AgNPs, gut bacteria and disease. Finally, we highlight the need to focus on the negative effects of AgNPs usage to facilitate appropriate development of these particles.

Effects and Mechanism of Nano-Copper Exposure on Hepatic Cytochrome P450 Enzymes in Rats

Although nano-copper is currently used extensively, the adverse effects on liver cytochrome P450 (CYP450) enzymes after oral exposure are not clear. In this study, we determined the effects and mechanisms of action of nano- and micro-copper on the expression and activity of CYP450 enzymes in rat liver. Rats were orally exposed to micro-copper (400 mg/kg), Cu ion (100 mg/kg), or nano-copper (100, 200 and 400 mg/kg) daily for seven consecutive days. Histopathological, inflammatory and oxidative stress were measured in the livers of all rats. The mRNA levels and activity of CYP450 enzymes, as well as the mRNA levels of select nuclear receptors, were determined. Exposure to nano-copper (400 mg/kg) induced significant oxidative stress and inflammation relative to the controls, indicated by increased levels of interleukin (IL)-2, IL-6, interferon (IFN)-γ, macrophage inflammatory protein (MIP-1), total antioxidant capacity (T-AOC), malondialdehyde (MDA), inducible nitric oxide synthase (iNOS) and nitric oxide (NO) after exposure. The levels of mRNA expression of pregnane X receptor (PXR), constitutive androstane receptor (CAR) and aryl hydrocarbon receptor (AHR) were significantly decreased in 400 mg/kg nano-copper treated rats. Nano-copper activated the expression of the NF-kappa B (NF-κB), mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription (STAT)3 signaling pathways. Nano-copper decreased the mRNA expression and activity of CYP 1A2, 2C11, 2D6, 2E1 and 3A4 in a dose-dependent manner. The adverse effects of micro-copper are less severe than those of nano-copper on the CYP450 enzymes of rats after oral exposure. Ingestion of large amounts of nano-copper in animals severely affects the drug metabolism of the liver by inhibiting the expression of various CYP450 enzymes, which increases the risk of drug-drug interactions in animals.

Nanofertilizer for Precision and Sustainable Agriculture: Current State and Future Perspectives

The increasing food demand as a result of the rising global population has prompted the large-scale use of fertilizers. As a result of resource constraints and low use efficiency of fertilizers, the cost to the farmer is increasing dramatically. Nanotechnology offers great potential to tailor fertilizer production with the desired chemical composition, improve the nutrient use efficiency that may reduce environmental impact, and boost the plant productivity. Furthermore, controlled release and targeted delivery of nanoscale active ingredients can realize the potential of sustainable and precision agriculture. A review of nanotechnology-based smart and precision agriculture is discussed in this paper. Scientific gaps to be overcome and fundamental questions to be answered for safe and effective development and deployment of nanotechnology are addressed.

Copper nanoparticles induce early fibrotic changes in the liver via TGF-β/Smad signaling and cause immunosuppressive effects in rats

Copper nanoparticles (Cu NPs) have various uses, including as additives in polymers/plastics, lubricants for metallic coating, and biomedical applications. We investigated the role of transforming growth factor (TGF)-β1 signaling in hepatic damage caused by Cu NPs and explored the effects of a 28-day repeated oral administration to Cu NPs on the immune response. The exposure to Cu NPs caused a dose-dependent increase in Cu levels in the liver and spleen. Cu NPs caused hepatic damage and markedly increased oxidative stress in liver tissues. Cu NPs induced activation of TGF-β1/Smad signaling by induction of vascular endothelial growth factor and matrix metalloproteinase-9. Exposure to Cu NPs also induced activation of Smad-independent pathways, phosphorylation of mitogen-activated protein kinases (MAPKs) and Akt/FoxO3. Consistent with the activation of TGF-β1/Smad-dependent and -independent pathways, Cu NPs markedly increased the deposition and induction of extracellular matrix components, α-smooth muscle actin, and collagens in liver tissues. In addition, repeated exposure to Cu NPs suppressed the proliferation of mitogenically stimulated T- or B-lymphocytes and decreased CD3⁺ (particularly, CD3⁺CD4⁺CD8^-) and CD45⁺ population, followed by decreased levels of immunoglobulins and Th1/Th2 type cytokines. Collectively, Cu NPs caused hepatic damage and induced pro-fibrotic changes, which were closely related to the activation of oxidative stress-mediated TGF-β1/Smad-dependent and -independent pathways (MAPKs and Akt/FoxO3). We confirmed the immunosuppressive effect of Cu NPs via the inhibition of mitogen-stimulated spleen-derived lymphocyte proliferation and suppression of B- or T-lymphocyte-mediated immune responses.

Prenatal exposure to nanosized zinc oxide in rats: neurotoxicity and postnatal impaired learning and memory ability

AIM

To examine the neurotoxicity of prenatal exposure to ZnO nanoparticles on rat offspring.

MATERIALS & METHODS

Pregnant Sprague-Dawley rats were exposed to ZnO nanoparticles (NPs) by gavage. Toxicity was assessed including zinc biodistribution, cerebral histopathology, antioxidant status and learning and memory capability.

RESULTS

A significantly elevated concentration of zinc was detected in offspring brains. Transmission electron microscope observations showed abnormal neuron ultrastructures. Histopathologic changes such as decreased proliferation and higher apoptotic death were observed. An obvious imbalanced antioxidant status occurred in brains. Adult experimental offspring exhibited impaired learning and memory behavior in the Morris water maze test compared with control groups.

CONCLUSION

These adverse effects on offspring brain may cause impaired learning and memory capabilities in adulthood, particularly in female rats.

Comparative toxicity and biodistribution assessments in rats following subchronic oral exposure to copper nanoparticles and microparticles

Background

Copper nanoparticles (Cu NPs) have great potential in electronics and biomedical fields because of their efficient thermodynamic and anti-microbial properties. However, their potential toxic effects and kinetic data following repeated exposure are still unclear.

Methods

We evaluated the physicochemical properties of Cu NPs (25 nm) and copper microparticles (Cu MPs, 14–25 μm). Comparative in vivo toxicity of Cu NPs and Cu MPs was evaluated by conducting a 28-day repeated oral dose study at equivalent dose levels of 0, 100, 200, and 400 mg/kg/day (vehicle, 1 % hydroxypropyl methylcellulose). We determined Cu levels in the blood, tissues, urine, and feces by using inductively coupled plasma mass spectrometry.

Results

The solubility of Cu NPs and Cu MPs was 84.5 and 17.2 %, respectively, in an acidic milieu; however, they scarcely dissolved in vehicle or intestinal milieus. The specific surface area of Cu NPs and Cu MPs was determined to be 14.7 and 0.16 m²/g, respectively. Cu NPs exhibited a dose-dependent increase of Cu content in the blood and tested organs, with particularly high levels of Cu in the liver, kidney, and spleen. Only for liver and kidney increased Cu levels were found in Cu MPs-treated rats. Cu NPs caused a dose-related increase in Cu levels in urine, whereas Cu MPs did not affect the urine Cu levels. Extremely high levels of Cu were detected in the feces of Cu MPs-treated rats, whereas much lower levels were detected in the feces of Cu NPs-treated rats. A comparative in vivo toxicity study showed that Cu NPs caused damages to red blood cells, thymus, spleen, liver, and kidney at ≥200 mg/kg/days, but Cu MPs did not cause any adverse effects even at the highest dose.

Conclusions

Overall, the in vivo repeated dose toxicity study of Cu NPs and Cu MPs demonstrated that large surface area and high solubility in physiological milieus could directly influence the toxicological responses and biodistribution of Cu particles when administered orally. Under these experimental conditions, the no-observed-adverse-effect levels of Cu NPs and Cu MPs were determined to be 100 and ≥400 mg/kg/day, respectively.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0169-x) contains supplementary material, which is available to authorized users.

Comparative toxicity and biodistribution of copper nanoparticles and cupric ions in rats

Despite widespread use and prospective biomedical applications of copper nanoparticles (Cu NPs), their biosafety issues and kinetics remain unclear. Thus, the aim of this study was to compare the detailed in vivo toxicity of Cu NPs and cupric ions (CuCl₂; Cu ions) after a single oral dose. We determined the physicochemical characteristics of Cu NPs, including morphology, hydrodynamic size, zeta potential, and dissolution in gastric (pH 1.5), vehicle (pH 6.5), and intestinal (pH 7.8) conditions. We also evaluated the kinetics of Cu following a single equivalent dose (500 mg/kg) of Cu NPs and Cu ions. Cu NPs had highest dissolution (84.5%) only in gastric conditions when compared with complete dissolution of Cu ions under various physiological milieus. Kinetic analysis revealed that highest Cu levels in blood and tested organs of Cu NP-treated rats were 15%–25% lower than that of Cu ions. Similar to the case of Cu ions, Cu levels in the tested organs (especially liver, kidney, and spleen) of Cu NP-treated rats increased significantly when compared with the vehicle control. However, delay in reaching the highest level and biopersistence of Cu were observed in the blood and tested organs of Cu NP-treated rats compared with Cu ions. Extremely high levels of Cu in feces indicated that unabsorbed Cu NPs or absorbed Cu ions were predominantly eliminated through liver/feces. Cu NPs exerted apparent toxicological effects at higher dose levels compared with Cu ions and showed sex-dependent differences in mortality, biochemistry, and histopathology. Liver, kidney, and spleen were the major organs affected by Cu NPs. Collectively, the toxicity and kinetics of Cu NPs are most likely influenced by the release of Cu dissociated from Cu NPs under physiological conditions.

Oral subchronic exposure to silver nanoparticles in rats

Because of their extremely small size, silver nanoparticles (AgNPs) show unique physical and chemical properties, with specific biological effects, which make them particularly attractive for being used in a number of consumer applications. However, these properties also influence the potential toxicity of AgNPs. In this study, we assessed the potential toxic effects of an in vivo oral sub-chronic exposure to polyvinyl pyrrolidone coated AgNPs (PVP-AgNPs) in adult male rats. We also assessed if oral PVP-AgNPs exposure could alter the levels of various metals (Fe, Mg, Zn and Cu) in tissues. Rats were orally given 0, 50, 100 and 200 mg/kg/day of PVP-AgNPs. Silver (Ag) accumulation in tissues, Ag excretion, biochemical and hematological parameters, metal levels, as well as histopathological changes and subcellular distribution following PVP-AgNPs exposure, were also investigated. After 90 days of treatment, AgNPs were found within hepatic and ileum cells. The major tissue concentration of Ag was found in ileum of treated animals. However, all tissues of PVP-AgNPs-exposed animals showed increased levels of Ag in comparison with those of rats in the control group. No harmful effects in liver and kidney, as well as in biochemical markers were noted at any treatment dose. In addition, no hematological or histopathological changes were found in treated animals. However, significant differences in Cu and Zn levels were found in thymus and brain of PVP-AgNPs-treated rats.

Stable non-covalent labeling of layered silicate nanoparticles for biological imaging

Layered silicate nanoparticles (LSN) are widely used in industrial applications and consumer products. They also have potential benefits in biomedical applications such as implantable devices and for drug delivery. To study how nanomaterials interact with cells and tissues, techniques to track and quantify their movement through different biological compartments are essential. While radiolabels can be very sensitive, particularly for in vivo studies, fluorescent labeling has been preferred in recent years because of the array of methods available to image and quantify fluorescent nanoparticles. However, labeling can be problematic, especially if it alters the physical properties of the nanomaterial. Herein is described a novel non-covalent labeling technique for LSN using readily available fluorescent dimeric cyanine dyes without the need to use excess amounts of dye to achieve labeling, or the need for removal of unbound dye. The approach utilizes the cationic binding properties of layered silicate clays and the multiple quaternary nitrogens associated with the dyes. Preparation of YOYO-1 labeled LSN with optimal dispersion in aqueous media is presented. The utilization of the labeled particles is then demonstrated in cell binding and uptake studies using flow cytometry and confocal microscopy. The labeled LSN are highly fluorescent, stable and exhibit identical physical properties with respect to the unlabeled nanoparticles. The general approach described here is applicable to other cyanine dyes and may be utilized more widely for labeling nanoparticles that comprise a crystalline plate structure with a high binding capacity.

Effects of oral exposure to silver nanoparticles on the sperm of rats

It has been demonstrated that exposure to silver nanoparticles (AgNPs) can induce toxicological effects in rodents. In this study, we investigated whether sub-chronic oral exposure to different doses of polyvinil pyrrolidone (PVP)-coated AgNPs (PVP-AgNPs) (50, 100 and 200mg/kg/day) could induce harmful effects on epididymal sperm rat parameters. Sperm motility, viability and morphology were examined. Moreover, a histological evaluation of testis and epididymis was also performed. High doses of PVP-AgNPs showed higher sperm morphology abnormalities, while a progressive, but not significant effect, was observed in other sperm parameters. The current results suggest that oral sub-chronic exposure to PVP-AgNPs induces slight toxicological effects in sperm rat parameters.

A synergic nanoantioxidant based on covalently modified halloysite–trolox nanotubes with intra-lumen loaded quercetin

Synergic antioxidant activity was achieved by grafting α-tocopherol derivatives on halloysite nanotubes, and by loading quercetin in the inner lumen.

Nano-food packaging: an overview of market, migration research, and safety regulations

Recently, food packages produced with nanoparticles, "nano-food packaging," have become more available in the current market. However, although the use of nanomaterials is increasing in food packaging applications, concern over toxicity affects consumer perceptions and acceptance. Quite a number of commercialized forms of nano-food packaging are coated or composited product with inorganic materials, for example, nanosilver and nanoclay as representative examples. Several studies have shown the possibility of nanomaterial migration from packaging or containers to foodstuff. The debate is still ongoing among researchers about the extent of migration and whether it is negligible and safe. Government agencies and stakeholders must hurry to determine use limitations and release conclusive legislation and regulations as soon as possible since nano-food packaging may have great impacts on human health. This paper aims to review the availability of nano-food packaging in the current market, report case studies on nanomaterial migration, and present the current status of safety regulations and management of nano-food packaging in leading countries across regions. This review should enable governments and researchers to develop further nanomaterial risk assessment studies.

Uptake of bright fluorophore core-silica shell nanoparticles by biological systems

Nanoparticles are used in a variety of consumer applications. Silica nanoparticles in particular are common, including as a component of foods. There are concerns that ingested nano-silica particles can cross the intestinal epithelium, enter the circulation, and accumulate in tissues and organs. Thus, tracking these particles is of interest, and fluorescence spectroscopic methods are well-suited for this purpose. However, nanosilica is not fluorescent. In this article, we focus on core-silica shell nanoparticles, using fluorescent Rhodamine 6G, Rhodamine 800, or CdSe/CdS/ZnS quantum dots as the core. These stable fluorophore/silica nanoparticles had surface characteristics similar to those of commercial silica particles. Thus, they were used as model particles to examine internalization by cultured cells, including an epithelial cell line relevant to the gastrointestinal tract. Finally, these particles were administered to mice by gavage, and their presence in various organs, including stomach, small intestine, cecum, colon, kidney, lung, brain, and spleen, was examined. By combining confocal fluorescence microscopy with inductively coupled plasma mass spectrometry, the presence of nanoparticles, rather than their dissolved form, was established in liver tissues.

Lab-on-a-chip-based high-throughput screening of the genotoxicity of engineered nanomaterials

The continuous increasing of engineered nanomaterials (ENMs) in our environment, their combinatorial diversity, and the associated genotoxic risks, highlight the urgent need to better define the possible toxicological effects of ENMs. In this context, we present a new high-throughput screening (HTS) platform based on the cytokinesis-block micronucleus (CBMN) assay, lab-on-chip cell sorting, and automated image analysis. This HTS platform has been successfully applied to the evaluation of the cytotoxic and genotoxic effects of silver nanoparticles (AgNPs) and silica nanoparticles (SiO2NPs). In particular, our results demonstrate the high cyto- and genotoxicity induced by AgNPs and the biocompatibility of SiO2NPs, in primary human lymphocytes. Moreover, our data reveal that the toxic effects are also dependent on size, surface coating, and surface charge. Most importantly, our HTS platform shows that AgNP-induced genotoxicity is lymphocyte sub-type dependent and is particularly pronounced in CD2+ and CD4+ cells.

Phospholipid-based nonlamellar mesophases for delivery systems: bridging the gap between empirical and rational design

Phospholipids are ubiquitous cell membrane components and relatively well-accepted ingredients due to their natural origin. Phosphatidylcholine (PC) in particular offers a promising alternative to monoglycerides for lyotropic liquid crystalline (LLC) delivery system applications in the food, cosmetics and pharmaceutical industries, provided its strong tendency to form zero-mean curvature lamellar mesophases in water can be overcome. Higher negative curvatures are usually reached through the addition of a third lipid component, forming a ternary diagram phospholipid/water/oil. The initial part of this work summarizes the potential advantages and the challenges of phospholipid-based delivery system applications. In the next part, various ternary PC/water/oil systems are discussed, with a special emphasis on the PC/water/cyclohexane and PC/water/α-tocopherol systems. We report that R-(+)-limonene has a quantitatively similar effect as cyclohexane. The last part is devoted to the theoretical interpretation of the observed phase behaviors. A fruitful parallel is drawn with PC polymer-like reverse micelles, leading to a thermodynamic description in terms of interfacial bending energy. Investigations at the molecular level are reviewed to help in bridging the empirical and theoretical approaches. Predictive rules are finally derived from this wide-ranging overview, thereby opening the way to a future rational design of PC-based LLC delivery systems.

Cryptic epitopes of albumin determine mononuclear phagocyte system clearance of nanomaterials

While plasma proteins can influence the physicochemical properties of nanoparticles, the adsorption of protein to the surface of nanomaterials can also alter the structure and function of the protein. Here, we show that plasma proteins form a hard corona around synthetic layered silicate nanoparticles (LSN) and that one of the principle proteins is serum albumin. The protein corona was required for recognition of the nanoparticles by scavenger receptors, a major receptor family associated with the mononuclear phagocyte system (MPS). Albumin alone could direct nanoparticle uptake by human macrophages, which involved class A but not class B scavenger receptors. Upon binding to LSN, albumin unfolded to reveal a cryptic epitope that could also be exposed by heat denaturation. This work provides an understanding of how albumin, and possibly other proteins, can promote nanomaterial recognition by the MPS without albumin requiring chemical modification for scavenger receptor recognition. These findings also demonstrate an additional function for albumin in vivo.

Progress in the characterization and safety evaluation of engineered inorganic nanomaterials in food

Nanotechnology has stepped into the food industry, from the farm to the table at home, in order to improve the taste and nutritional value, extend the shelf-life and monitor the food quality. In fact, as consumers we have already been in contact, via oral exposure, with a number of food products containing engineered nanomaterials (ENMs) more often than most people think. However, the fate of ENMs after entering the GI tract of the human body is not yet clearly understood. Hence, the related safety issue is raised, and attracts much attention and wide debate from the public, even including protest demonstrations against nanotechnology in food. In this review, we summarize the up-to-date information about the characterization and safety evaluation of common inorganic ENMs (with a focus on silver, titanium dioxide, silica and zinc oxide nanoparticles) in food. Based on the literature, a whole scenario of the safety issue of these ENMs in food and an outlook on the future studies are given.

Nanotechnology in food processing sector-An assessment of emerging trends

Use of nanoscience based technology in the food industry is fast emerging as new area for research and development. Several research groups including private companies in the industry have initiated research programmes for exploring the wide scope of nanotechnology into the value chain of food processing and manufacturing. This paper discusses the current focus of research in this area and assesses its potential impacts. Using the developed relational database framework with R&D indicators like literature and patent documents for assessment of the potential of nanotechnology in food sector, a model to organize and map nanoresearch areas to the food processing sector was developed. The study indicates that the about five basic categories of nanotechnology applications and functionalities currently in the development of food sector, include food processing, packaging, nutraceuticals delivery, food safety and functional foods.

Broad-spectrum antibacterial activity of carbon nanotubes to human gut bacteria

Carbon nanotubes (CNTs) hold promise in manufacturing, environmental, and biomedical applications, as well as food and agricultural industries. Previous observations have shown that CNTs have antimicrobial activity; however, the impact of CNTs to human gut microbes has not been investigated. Here, the antibacterial activity of CNTs against the microbes commonly encountered in the human digestion system--L. acidophilus, B. adolescentis, E. coli, E. faecalis, and S. aureus--are evaluated. The bacteria studied include pathogenic and non-pathogenic, gram-positive and negative, and both sphere and rod strains. In this study, CNTs, including single-walled CNTs (SWCNTs, 1-3 μm), short and long multi-walled CNTs (s-MWCNTs: 0.5-2 μm; l-MWCNTs: >50 μm), and functionalized multi-walled CNTs (hydroxyl- and carboxyl-modification, 0.5-2 μm), all have broad-spectrum antibacterial effects. Notably, CNTs may selectively lyse the walls and membranes of human gut microbes, depending on not only the length and surface functional groups of CNTs, but also the shapes of the bacteria. The mechanism of antibacterial activity is associated with their diameter-dependent piercing and length-dependent wrapping on the lysis of microbial walls and membranes, inducing release of intracellular components DNA and RNA and allowing a loss of bacterial membrane potential, demonstrating complete destruction of bacteria. Thin and rigid SWCNT show more effective wall/membrane piercing on spherical bacteria than MWCNTs. Long MWCNT may wrap around gut bacteria, increasing the area making contact with the bacterial wall. This work suggests that CNTs may be broad-spectrum and efficient antibacterial agents in the gut, and selective application of CNTs could reduce the potential hazard to probiotic bacteria.

Characterization and preliminary toxicity assay of nano-titanium dioxide additive in sugar-coated chewing gum

Nanotechnology shows great potential for producing food with higher quality and better taste through including new additives, improving nutrient delivery, and using better packaging. However, lack of investigations on safety issues of nanofood has resulted in public fears. How to characterize engineered nanomaterials in food and assess the toxicity and health impact of nanofood remains a big challenge. Herein, a facile and highly reliable separation method of TiO2 particles from food products (focusing on sugar-coated chewing gum) is reported, and the first comprehensive characterization study on food nanoparticles by multiple qualitative and quantitative methods is provided. The detailed information on nanoparticles in gum includes chemical composition, morphology, size distribution, crystalline phase, particle and mass concentration, surface charge, and aggregation state. Surprisingly, the results show that the number of food products containing nano-TiO2 (<200 nm) is much larger than known, and consumers have already often been exposed to engineered nanoparticles in daily life. Over 93% of TiO2 in gum is nano-TiO2 , and it is unexpectedly easy to come out and be swallowed by a person who chews gum. Preliminary cytotoxicity assays show that the gum nano-TiO2 particles are relatively safe for gastrointestinal cells within 24 h even at a concentration of 200 μg mL(-1) . This comprehensive study demonstrates accurate physicochemical property, exposure, and cytotoxicity information on engineered nanoparticles in food, which is a prerequisite for the successful safety assessment of nanofood products.

Susceptibility of young and adult rats to the oral toxicity of titanium dioxide nanoparticles

Titanium dioxide nanoparticles (TiO2 NPs) have potential applications as food additives, but concerns persist about their safety. Children are identified as having the highest exposure and may face the greatest health risks. However, the toxicological sensitivity of TiO2 NPs in different ages is not clear. Here, a comparative toxicity study of TiO2 NPs in 3-week (youth) and 8-week (adult) old Sprague-Dawley rats is reported following oral exposure at doses of 0, 10, 50, 200 mg kg(-1) body weight per day for 30 days. The organ mass and histology, blood biochemistry and redox state, intestinal function, and biodistribution of NPs are characterized. The results show that TiO2 NPs induce different toxic effects on young and adult rats. The liver edema, heart injuries and non-allergic mast cell activation in stomach tissues are found in young rats. On the other hand, only slight injury in the liver and kidney and decreased intestinal permeability and molybdenum contents are found in adult rats. Furthermore, TiO2 NP exposure can provoke reductive stress (i.e., increased reduced glutathione (GSH)/oxidized glutathione (GSSG) ratios) in plasmas through enhancing the glucose and GSH levels in young rats or reducing the glutathione peroxidase (GSH-Px) acitivity and GSSG levels in adult rats. These results suggest that different ages may require different biomarkers for identifying and monitoring oral toxicity of nanoparticles.

Comparative absorption, distribution, and excretion of titanium dioxide and zinc oxide nanoparticles after repeated oral administration

Background

The in vivo kinetics of nanoparticles is an essential to understand the hazard of nanoparticles. Here, the absorption, distribution, and excretion patterns of titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles following oral administration were evaluated.

Methods

Nanoparticles were orally administered to rats for 13 weeks (7 days/week). Samples of blood, tissues (liver, kidneys, spleen, and brain), urine, and feces were obtained at necropsy. The level of Ti or Zn in each sample was measured using inductively coupled plasma-mass spectrometry.

Results

TiO₂ nanoparticles had extremely low absorption, while ZnO nanoparticles had higher absorption and a clear dose-response curve. Tissue distribution data showed that TiO₂ nanoparticles were not significantly increased in sampled organs, even in the group receiving the highest dose (1041.5 mg/kg body weight). In contrast, Zn concentrations in the liver and kidney were significantly increased compared with the vehicle control. ZnO nanoparticles in the spleen and brain were minimally increased. Ti concentrations were not significantly increased in the urine, while Zn levels were significantly increased in the urine, again with a clear dose-response curve. Very high concentrations of Ti were detected in the feces, while much less Zn was detected in the feces.

Conclusions

Compared with TiO₂ nanoparticles, ZnO nanoparticles demonstrated higher absorption and more extensive organ distribution when administered orally. The higher absorption of ZnO than TiO₂ nanoparticles might be due to the higher dissolution rate in acidic gastric fluid, although more thorough studies are needed.

Rat pancreatitis produced by 13-week administration of zinc oxide nanoparticles: biopersistence of nanoparticles and possible solutions

Zinc oxide (ZnO) nanoparticles (NPs) are used in diverse applications ranging from paints and cosmetics to biomedicine and food. Although micron-sized ZnO is a traditional food supplement, ZnO NPs are an unknown public health risk because of their unique physicochemical properties. Herein, we studied the 13-week subchronic toxicity of ZnO NPs administered via the oral route according to Organization for Economic Cooperation and Development (OECD) test guideline 408. Well-dispersed ZnO NPs were administered to Sprague-Dawley (SD) rats (11/sex/group) at doses of 67.1, 134.2, 268.4 or 536.8 mg kg(-1) per body weight over a 13-week period. The mean body weight gain in males given 536.8 mg kg(-1) ZnO NPs was significantly lower than that of control male rats, whereas no significant differences were observed between the other treatment groups and the controls. Male and female rats dosed at 536.8 mg kg(-1) ZnO NPs had significant changes in anemia-related hematologic parameters. Mild to moderate pancreatitis also developed in both sexes dosed at 536.8 mg kg(-1) , whereas no histological changes were observed in the other treatment groups. To evaluate the mechanism of toxicity, we performed a bio-persistence study and evaluated the effects of the ZnO NPs on cell proliferation. The treatment of a human gastric adenocarcinoma cell line with ZnO NPs resulted in a significant inhibition of cellular proliferation. The anti-proliferative effect of ZnO NPs or Zn(2+) was effectively blocked by treatment with chelators. These results indicate that the bio-persistence of ZnO NPs after ingestion is key to their toxicity; the no-observed-adverse effect level (NOAEL) of ZnO NPs was found to be 268.4 mg kg(-1) per day for both sexes.

Critical issues in sensor science to aid food and water safety

The stability of food and water supplies is widely recognized as a global issue of fundamental importance. Sensor development for food and water safety by nonconventional assays continues to overcome technological challenges. The delicate balance between attaining adequate limits of detection, chemical fingerprinting of the target species, dealing with the complex food matrix, and operating in difficult environments are still the focus of current efforts. While the traditional pursuit of robust recognition methods remains important, emerging engineered nanomaterials and nanotechnology promise better sensor performance but also bring about new challenges. Both advanced receptor-based sensors and emerging non-receptor-based physical sensors are evaluated for their critical challenges toward out-of-laboratory applications.

Mechanism of hen egg white lysozyme adsorption on a charged solid surface

The mechanism of hen egg white lysozyme (HEWL) adsorption on a negatively charged, hydrophilic surface has been studied using atomistic molecular dynamics (MD) simulation. Sixteen 90 ns trajectories provide adequate data to allow a detailed description of the adsorption process to be formulated. Two distinct adsorption sites have been identified. The main one is located on the N,C-terminal protein face and comprises Arg128 (the crucial one), supplemented by Arg125, Arg5, and Lys1; the minor one is used accidentally and contains only Arg68. Adsorption of this protein is driven by electrostatics, where the orientation of the protein dipole moment defines the direction of protein movement. The diffusion range on the surface depends on protein side-chain penetration through the surface water layers. This is facilitated by the long-range electric field of the charged surface, which can align polar side chains to be perpendicular to the surface. A simulation of adsorption onto a neutral ionic surface shows no such surface water layer penetration. Therefore, protein flexibility is seen to be an important factor, and to adsorb the HEWL has to adjust its structure. Nevertheless, at a flat surface only a slight loss of α-helical content is required. The adsorbed HEWL molecule is oriented between side-on and end-on ways, where the angle between the protein long axis (which mostly approximates the dipole moment) and the surface varies between 45° and 90°. Simulations with targeted mutations confirm the picture that emerges from these studies. The active site is located on the opposite face to the main adsorption site; hence, the activity of the immobilized HEWL should not be affected by the surface interactions. Our results provide a detailed insight into the adsorption mechanism and protein mobility at the surface. This knowledge will aid the proper interpretation of experimental results and the design of new experiments and functional systems.