ReviewNanopesticide research: Current trends and future priorities
Introduction
Research into nanotechnology applications for use in agriculture has become increasingly popular over the past decade. The development of novel plant-protection products has received greater attention than other applications, such as those related to nanosensors or fertilizers.
Two complementary literature reviews have previously been published, presenting the knowledge available up to the end of 2011. Kah et al. (2013) integrated information from more than 3000 patents and 100 peer-reviewed publications and reports to provide an overview of the different types of nanopesticides that had been proposed. Possible fate and environmental impacts of nanopesticides were discussed in order to analyze the suitability of current regulatory exposure assessment. A complementary analysis focusing mainly on inorganic nanopesticides and fertilizers (based on 36 publications and 33 patents) has been presented by Gogos et al. (2012).
There has been a considerable amount of subsequent research in this field, and this paper aims to provide an update on the latest research presented in peer-reviewed publications since October 2011 (more than 40 papers in total, not included in previous literature reviews).
A number of issues relating to the definition of nanopesticides are first discussed, in order to define the scope of our analysis. General trends in the most recent research are then presented, followed by more detailed discussions on each specific category of products. The closing sections of the paper discuss a number of key aspects relating to environmental risk assessment for nanopesticides, and that have not been included in any previous literature reviews. The processes discussed are particularly relevant to polymer-based nanopesticides that have received a great deal of attention in recent years.
Section snippets
Definition and scope
It is important to distinguish the different ways in which the term “nanopesticide” is used within regulatory, scientific, public, and commercial frameworks, as the criteria that are applied in these different contexts typically vary with regard to, for example, particle size, activity, and the perceptions of novelty or risk. Issues relating to the definition of nanoparticles and how the criteria proposed to date could apply to nanopesticides have been previously discussed by Kah et al. (2013).
General trends
Analysis of all relevant peer-reviewed literature published between 2000 and 2013 (about 90 peer-reviewed papers) revealed that the majority of publications originated from Asia (mainly from China and India, representing 28% and 20% of the total number of publications, respectively), followed by the United States (20%). About half (i.e., 55%) of the nanopesticides investigated were insecticides, followed by fungicides (30%) and herbicides (15%).
The high proportion of nanoformulations for
Nanoemulsions
The aim of nanoemulsions is generally to increase the apparent solubility of poorly soluble AIs, while keeping the concentration of surfactants lower than that in microemulsions (typically 5–10% of surfactant, compared to 20% in microemulsions).
Nanoemulsions have received a great deal of attention from the pharmaceutical sector, for example as potential vehicles for transdermal delivery of hydrophobic drugs (Shakeel et al., 2012). Nanoemulsions of pesticidal AIs have often been suggested to
Considerations concerning environmental fate
The effects that a nanoformulation has on the fate of an AI may be multiple and depend on the product under consideration. The objective of many of the nanoformulations presented in published literature is to achieve the slow release of an organic AI and/or to protect it from premature degradation. The data summarized in Table 1 show that a number of products have achieved this objective. Such nanoformulations are therefore expected to have a direct impact on the persistence of the AIs.
The
Conclusions
The rapid developments in nanopesticide research over the last two years have motivated a number of international organizations to consider potential issues relating to the use of nanotechnology for crop protection. This analysis of the latest research trends provides a useful basis for identifying research gaps and future priorities.
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Polymer-based formulations have recently received the greatest attention, while research into the application of more classical engineered nanoparticles (e.g.,
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