A framework to evaluate whether to pool or separate behaviors in a multilayer network.

A multilayer network approach combines different network layers, which are connected by interlayer edges, to create a single mathematical object. These networks can contain a variety of information types and represent different aspects of a system. However, the process for selecting which information to include is not always straightforward. Using data on 2 agonistic behaviors in a captive population of monk parakeets (Myiopsitta monachus), we developed a framework for investigating how pooling or splitting behaviors at the scale of dyadic relationships (between 2 individuals) affects individual- and group-level social properties. We designed 2 reference models to test whether randomizing the number of interactions across behavior types results in similar structural patterns as the observed data. Although the behaviors were correlated, the first reference model suggests that the 2 behaviors convey different information about some social properties and should therefore not be pooled. However, once we controlled for data sparsity, we found that the observed measures corresponded with those from the second reference model. Hence, our initial result may have been due to the unequal frequencies of each behavior. Overall, our findings support pooling the 2 behaviors. Awareness of how selected measurements can be affected by data properties is warranted, but nonetheless our framework disentangles these efforts and as a result can be used for myriad types of behaviors and questions. This framework will help researchers make informed and data-driven decisions about which behaviors to pool or separate, prior to using the data in subsequent multilayer network analyses.

Cyanine5-doped silica nanoparticles as ultra-bright immunospecific labels for model circulating tumour cells in flow cytometry and microscopy.

In this work, ultra-bright fluorescent silica nanoparticles (NPs) labels have been shown to selectively bind to a model circulating tumour cell (CTC) line, MCF-7, a metastatic breast cancer by targeting epithelial cellular adhesion molecule (EpCAM) present on the MCF-7 cell membrane. Silica NPs approximately 40nm in diameter were doped with different concentrations of Cyanine5 dye molecules, using the reverse microemulsion method. The NPs were two orders of magnitude brighter than Cyanine5 free dye and the measured fluorescence intensity matched a homo-Förster Resonance Energy Transfer model. NPs were conjugated with anti-EpCAM antibody to the NP surface for immunospecific targeting. In flow cytometry experiments the NPs were twice as bright as two commercial anti-EpCAM red fluorophore conjugates, APC and AlexaFluor®647. This increase is achieved while keeping non-specific binding low as established in control tests with a non-metastatic cancer cell line (HeLa). The NPs were also immunospecific in fluorescence microscopy experiments performed at room temperature on non-fixed cells. Confocal microscopy was used to confirm the NPs were located on the surface of the cells, matching with the location of the EpCAM marker. These NPs labels have excellent potential in biomedical diagnostics, particularly when high signal to noise and good photostability are needed, for example, in point-of-care testing.