Seed dispersal is a central process in plant ecology with consequences for species composition and habitat structure. Some bird species are known to disperse the seeds they ingest, whereas others, termed 'seed predators', digest them and apparently play no part in dispersal, but it is not clear if these are discrete strategies or simply the ends of a continuum. We assessed dispersal effectiveness by combining analysis of faecal samples and bird density. The droppings of seed dispersers contained more entire seeds than those of typical seed predators, but over a quarter of the droppings of seed predators contained whole seeds. This effect was further magnified when bird density was taken into account, and was driven largely by one frequent interaction: the Chaffinch Fringilla coelebs, a typical seed predator and the most abundant bird species in the area and dispersed seeds of Leycesteria formosa, a non-native plant with berry-like fruits. These results suggest the existence of a continuum between seed predators and seed dispersers.

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(1) Background: The lack of globally standardized allergen labeling legislation necessitates consumer-focused multiplexed testing devices. These should be easy to operate, fast, sensitive and robust. (2) Methods: Herein, we describe the development of three different formats for multiplexed food allergen detection, namely active and passive flow-through assays, and lateral flow immunoassays with different test line configurations. (3) Results: The fastest assay time was 1 min, whereas even the slowest assay was within 10 min. With the passive flow approach, the limits of detection (LOD) of 0.1 and 0.5 ppm for total hazelnut protein (THP) and total peanut protein (TPP) in spiked buffer were reached, or 1 and 5 ppm of THP and TPP spiked into matrix. In comparison, the active flow approach reached LODs of 0.05 ppm for both analytes in buffer and 0.5 and 1 ppm of THP and TPP spiked into matrix. The optimized LFIA configuration reached LODs of 0.1 and 0.5 ppm of THP and TPP spiked into buffer or 0.5 ppm for both analytes spiked into matrix. The optimized LFIA was validated by testing in 20 different blank and spiked matrices. Using device-independent color space for smartphone analysis, two different smartphone models were used for the analysis of optimized assays.

In this critical review, we provide a comprehensive overview of immunochemical food allergen assays and detectors in the context of their user-friendliness, through their connection to smartphones. Smartphone-based analysis is centered around citizen science, putting analysis into the hands of the consumer. Food allergies represent a significant worldwide health concern and consumers should be able to analyze their foods, whenever and wherever they are, for allergen presence. Owing to the need for a scientific background, traditional laboratory-based detection methods are generally unsuitable for the consumer. Therefore, it is important to develop simple, safe, and rapid assays that can be linked with smartphones as detectors to improve user accessibility. Smartphones make excellent detection systems because of their cameras, embedded flash functions, portability, connectivity, and affordability. Therefore, this review has summarized traditional laboratory-based methods for food allergen detection such as enzyme-linked-immunosorbent assay, flow cytometry, and surface plasmon resonance, and the potential to modernize these methods by interfacing them with a smartphone readout system, based on the aforementioned smartphone characteristics. This is the first review focusing on smartphone-based food-allergen detection methods designed with the intention of being consumer-friendly. Graphical abstractA smartphone-based food allergen detection system in three easy steps (1) sample preparation, (2) allergen detection on a smartphone using antibodies, which then transmits the data wirelessly, (3) analytical results sent straight to smartphone Electronic supplementary materialThe online version of this article (10.1007/s00216-018-0989-7) contains supplementary material, which is available to authorized users.

Sandwich lateral flow immunoassays (LFIAs) are limited at high antigen concentrations by the hook effect, leading to a contradictory decrease in the test line (T) intensity and false-negative results. The hook effect is mainly associated with the loss of T, and research focuses on minimizing this effect. Nevertheless, the control line (C) intensity is also affected at higher analyte concentrations, undesirably influencing the T/C ratio in LFIA readers. The main aim of this work is to identify and understand these high antigen concentration effects in order to develop ubiquitous strategies to interpret and mitigate such effects. Four complementary experiments were performed: performance assessment of three different allergen LFIAs (two for hazelnut, one for peanut) over 0.075–3500 ppm, LFIAs with C only, surface plasmon resonance (SPR) binding experiments on the immobilized control antibody, and smartphone video recording of LFIAs during their development. As antigen concentrations increase, the C signal decreases before the T signal does, suggesting that distinct mechanisms underlie these intensity reductions. Reduced binding at the C occurred even in the absence of T, so the upfront T does not explain the loss of C. SPR confirmed that the C antibody favors binding with free labeled antibody compared with a labeled antibody–analyte complex, indicating that in antigen excess, binding is reduced at C before T. Finally, a smartphone-based video method was developed for dynamically monitoring the LFIA development in real time to distinguish between different concentration-dependent effects. Digitally analyzing the data allows clear differentiation of highly positive samples and false-negative samples and can indicate whether the LFIA is in the dynamic working range or at critically high concentrations. The aim of this work is to identify and understand such high antigen concentration effects in order to develop ubiquitous strategies to interpret and mitigate such effects.