Silver nanoparticles (Ag NPs) are becoming increasingly prevalent in consumer products as antibacterial agents. The increased use of Ag NP-enhanced products may lead to an increase in toxic levels of environmental silver, but regulatory control over the use or disposal of such products is lagging due to insufficient assessment on the toxicology of Ag NPs and their rate of release into the environment. In this article we discuss recent research on the transport, activity and fate of Ag NPs at the cellular and organismic level, in conjunction with traditional and recently established methods of nanoparticle characterization. We include several proposed mechanisms of cytotoxicity based on such studies, as well as new opportunities for investigating the uptake and fate of Ag NPs in living systems.

Indole-3-acetic acid (IAA) is a primary phytohormone that regulates multiple aspects of plant development. Because polar transport of IAA is an essential determinant of organogenesis and dynamic tropic growth, methods to monitor IAA movement in vivo are in demand. A self-referencing electrochemical microsensor was optimized to non-invasively measure endogenous IAA flux near the surface of Zea mays roots without the addition of exogenous IAA. Enhanced sensor surface modification, decoupling of acquired signals, and integrated flux analyses were combined to provide direct, real time quantification of endogenous IAA movement in B73 maize inbred and brachytic2 (br2) auxin transport mutant roots. BR2 is localized in epidermal and hypodermal tissues at the root apex. br2 roots exhibit reduced shootward IAA transport at the root apex in radiotracer experiments and reduced gravitropic growth. IAA flux data indicates that maximal transport occurs in the distal elongation zone of maize roots, and net transport in/out of br2 roots was decreased compared to B73. Integration of short term real time flux data in this zone revealed oscillatory patterns, with B73 exhibiting shorter oscillatory periods and greater amplitude than br2. IAA efflux and influx were inhibited using 1-N-naphthylphthalamic acid (NPA), and 2-naphthoxyacetic acid (NOA), respectively. A simple harmonic oscillation model of these data produced a correlation between modeled and measured values of 0.70 for B73 and 0.69 for br2. These results indicate that this technique is useful for real-time IAA transport monitoring in surface tissues and that this approach can be performed simultaneously with current live imaging techniques.

Repeated applications of phosphorus (P) fertilizers result in the buildup of P in soil (commonly known as legacy P), a large fraction of which is not immediately available for plant use. Long-term applications and accumulations of soil P is an inefficient use of dwindling P supplies and can result in nutrient runoff, often leading to eutrophication of water bodies. Although soil legacy P is problematic in some regards, it conversely may serve as a source of P for crop use and could potentially decrease dependence on external P fertilizer inputs. This paper reviews the (1) current knowledge on the occurrence and bioaccessibility of different chemical forms of P in soil, (2) legacy P transformations with mineral and organic fertilizer applications in relation to their potential bioaccessibility, and (3) approaches and associated challenges for accessing native soil P that could be used to harness soil legacy P for crop production. We highlight how the occurrence and potential bioaccessibility of different forms of soil inorganic and organic P vary depending on soil properties, such as soil pH and organic matter content. We also found that accumulation of inorganic legacy P forms changes more than organic P species with fertilizer applications and cessations. We also discuss progress and challenges with current approaches for accessing native soil P that could be used for accessing legacy P, including natural and genetically modified plant-based strategies, the use of P-solubilizing microorganisms, and immobilized organic P-hydrolyzing enzymes. It is foreseeable that accessing legacy P will require multidisciplinary approaches to address these limitations.

Real-time monitoring of physiological glucose transport is crucial for gaining new understanding of diabetes. Many techniques and equipment currently exist for measuring glucose, but these techniques are limited by complexity of the measurement, requirement of bulky equipment, and low temporal/spatial resolution. The development of various types of biosensors (eg, electrochemical, optical sensors) for laboratory and/or clinical applications will provide new insights into the cause(s) and possible treatments of diabetes. State-of-the-art biosensors are improved by incorporating catalytic nanomaterials such as carbon nanotubes, graphene, electrospun nanofibers, and quantum dots. These nanomaterials greatly enhance biosensor performance, namely sensitivity, response time, and limit of detection. A wide range of new biosensors that incorporate nanomaterials such as lab-on-chip and nanosensor devices are currently being developed for in vivo and in vitro glucose sensing. These real-time monitoring tools represent a powerful diagnostic and monitoring tool for measuring glucose in diabetes research and point of care diagnostics. However, concerns over the possible toxicity of some nanomaterials limit the application of these devices for in vivo sensing. This review provides a general overview of the state of the art in nanomaterial-mediated biosensors for in vivo and in vitro glucose sensing, and discusses some of the challenges associated with nanomaterial toxicity.

In foods, high levels of biogenic amines (BA) are the result of microbial metabolism that could be affected by temperatures and storage conditions. Thus, the level of BA is commonly used as an indicator of food safety and quality. This manuscript outlines the development of laser scribed graphene electrodes, with locally sourced materials, for reagent-free food safety biosensing. To fabricate the biosensors, the graphene surface was functionalized with copper microparticles and diamine oxidase, purchased from a local supermarket; and then compared to biosensors fabricated with analytical grade materials. The amperometric biosensor exhibits good electrochemical performance, with an average histamine sensitivity of 23.3 µA/mM, a lower detection limit of 11.6 µM, and a response time of 7.3 s, showing similar performance to biosensors constructed from analytical grade materials. We demonstrated the application of the biosensor by testing total BA concentration in fish paste samples subjected to fermentation with lactic acid bacteria. Biogenic amines concentrations prior to lactic acid fermentation were below the detection limit of the biosensor, while concentration after fermentation was 19.24 ± 8.21 mg histamine/kg, confirming that the sensor was selective in a complex food matrix. The low-cost, rapid, and accurate device is a promising tool for biogenic amine estimation in food samples, particularly in situations where standard laboratory techniques are unavailable, or are cost prohibitive. This biosensor can be used for screening food samples, potentially limiting food waste, while reducing chances of foodborne outbreaks.